2015 Fracture of the Nasal Bones in a Horse by Nathalie

GHENT UNIVERSITY

FACULTY OF VETERINARY MEDICINE

Academic year 2014 - 2015

Fracture of the Nasal Bones in a Horse

Nathalie HILMO

Promotors: Prof. Dr. L. Vlaminck Clinical Case report as a part Veterinary Thomas Van Bergen of the Master’s Dissertation

The author and the promoters agree this thesis is to be available for consultation and for personal reference use. Every other use falls within the constraints of the copyright, particularly concerning the obligation to specially mention the source when citing the results of this thesis. The copyright concerning the information given in this thesis lies with the promoters. The copyright is restricted to the method by which the subject investigated is approached and presented. The author herewith respects the original copyright of the books and papers quoted, including their pertaining documentation such as tables and illustrations. The author and the promoters are not responsible for any recommended treatments or doses cited and described in this study.

GHENT UNIVERSITY

FACULTY OF VETERINARY MEDICINE

Academic year 2014 - 2015

Fracture of the Nasal Bones in a Horse

Nathalie HILMO

Promotors: Prof. dr. L. Vlaminck Clinical case report as a part Veterinary Thomas Van Bergen of the Master’s Dissertation

I would like to express my very great appreciation to my promotor Prof. L. Vlaminck for his indispensable guidance trough this case study. I also wish to thank my second promotor Thomas Van Bergen. Dr. I. Gielen provided me with medical images, for which I am very grateful.

I am particularly grateful to my boyfriend Sindre Stordahl for providing technical help and emotional support when I needed it the most. Marte Ingvild Stordahl has offered very good help with proofreading the paper, for which I want to thank her. Last, but not least, I would like to offer my special thanks to my family for encouragement and invaluable help throughout my whole study period.

Table of Contents

ABSTRACT ...... 1 SAMENVATTING ...... 2 INTRODUCTION ...... 4 1. CASE HISTORY ...... 5 1.1. ANAMNESIS ...... 5 1.2. CLINICAL EXAMINATION ...... 5 1.3. INITIAL TREATMENT ...... 5 1.4. MEDICAL IMAGING ...... 6 1.4.1. Radiography ...... 6 1.4.1. Computed Tomography ...... 7 1.5. DIAGNOSE ...... 8 1.6. TREATMENT ...... 8 1.6.1. Surgery ...... 8 1.6.2. Follow-up ...... 9 2. LITERATURE REVIEW ...... 10 2.1. ANATOMICAL CONSIDERATIONS ...... 10 2.2. INJURY ...... 11 2.3. DIAGNOSIS ...... 12 2.3.1. Physical examination ...... 12 2.3.2. Medical imaging ...... 13 2.3.2.1. Radiography ...... 13 2.3.2.2. Computed tomography ...... 13 2.4. TREATMENT ...... 14 2.4.1. Initial management of the injured horse ...... 14 2.4.2. Conservative treatment ...... 15 2.4.3. Surgical treatment ...... 16 2.4.4. Aftercare ...... 19 2.5. PROGNOSIS ...... 19 DISCUSSION ...... 20 REFERENCES ...... 23

ABSTRACT

A horse was exposed to blunt trauma and was presented with bilateral epistaxis, dyspnea and distortion of the facial contour. Initially, the treatment focused on calming the horse down, managing pain, and stopping the bleeding. Proper subsequent treatment was dependent on an adequate diagnosis and assessment of severity. Hereby, radiography was performed to evaluate the fracture of the nasal bones and involvement of the sinuses. Additionally, pre-operative computed tomography (CT) was performed to depict the fracture configuration and involvement of internal structures. In some cases conservative management of facial structures can provide a functional outcome, however, facial deformities are commonly reported complications. Surgical intervention is often indicated to reconstruct the facial contour, maximize airflow and decrease the risk of complications. Different reconstructive techniques have been described for facial fractures of the paranasal sinuses and nasal cavity. The decision whether fixation is required and which material to use depends on the stability of the fractured fragments after reduction. In this case surgery was performed, consisting of elevating the fracture into good alignment followed by fixation with a compression plate. Other alternatives such as the FlapFix system, or interfragmentary wiring with stainless steel wire or polydioxanone sutures can also be used for fixation. Despite contamination from the respiratory tract, facial fractures which are treated properly generally have good results.

Key words: horse – trauma – nasal fracture – examination – dyspnea – fixation

SAMENVATTING

In deze casuïstiek wordt een klinisch geval beschreven van een neusfractuur bij het paard. Aan de hand van een literatuurstudie wordt een overzicht gegeven van de diagnostische mogelijkheden en de verschillende chirurgische technieken, die toegepast kunnen worden bij traumatische letsels van de neus bij het paard.

Een 8 jaar oude warmbloed ruin werd aangeboden in de kliniek voor heelkunde en anesthesie van de grote huisdieren op de faculteit diergeneeskunde, te Merelbeke. Tijdens aquatraining raakte hij in paniek en liep tegen een ijzeren paal.Hij had een ernstige neusbloeding en een uitwendig zichtbare deformatie van de neus. De doorverwijzende dierenarts diende dexamethasone en meloxicam intraveneus toe, om de pijn en ontsteking te verminderen. Daarna verwees hij het paard door naar de faculteit voor verdere behandeling.

Traumatische letsels en depressiefracturen ter hoogte van de neusbeenderen, behoren tot de meest voorkomende aandoeningen van het respiratoire stelsel van het paard. Doordat de beenderen van de neus en het voorhoofd een dunne cortex en gering bovenliggend weefsel hebben, zijn ze erg gevoelig voor traumata.

Klinisch onderzoek van het paard toonde een normale ademhalingsfrequentie, maar wel een bemoeilijkte ademhaling. Zijn capillaire vullingstijd was minder dan twee seconden en zijn lichaamstemperatuur was 38,7°C. Bij visuele inspectie en palpatie was ter hoogte van het rostrale deel van de neus een transverse depressie fractuur, van twee tot drie centimeter, zichtbaar en voelbaar. Er was een duidelijke zwelling rostraal van de fractuurlijn aanwezig en lichte pijn bij palpatie.

Als initiële behandeling werd benzylpenicilline intramusculair en flunixine meglumine intraveneus toegediend. Phenylephrine werd bilateraal intranasaal toegediend voor vasoconstrictie en het antifibrinolytisch transhexaminezuur werd toegediend om de bloeding onder controle te krijgen. De linker neushelft werd opgetamponneerd. Vanwege de erge dyspnee werd het paard uit voorzorg geschoren voor een eventuele noodtracheotomie.

De anatomie van het hoofd van het paard is vrij complex. Uitgebreide kennis over de anatomie en diagnostische hulpmiddelen zijn een voorwaarde voor een succesvolle diagnose en behandeling bij traumata zoals deze. Een staande links-rechts laterale radiografische opname (Fig. 1) bevestigde een acute depressie fractuur met milde verplaatsing van de neusbeenderen.

Vervolgens besloot men operatief in te grijpen. Het paard werd onder algemene anesthesie gebracht. Voor de operatie werd een CT-scan uitgevoerd. Een CT-scan is een uitstekend middel om de complexiteit van de neus en het voorhoofd van het paard in beeld te brengen. Een axiaal beeld (Fig. 2) toonde een fractuur van beide neusbeenderen met depressie van het linker neusbeen. Met een serie van axiale beelden werden driedimensionale beelden gecreëerd. Figuur 3 toont een transverse fractuur met een depressie van 1,7 cm van het distale fragment. De conchae waren ernstig beschadigd.

Een conservatieve behandeling kan overwogen worden bij stabiele, niet verplaatste fracturen van de neus, die niet interfereren met de luchtpassage of de ogen. Vooral als het cosmetisch resultaat geen prioriteit heeft. Tegenwoordig is chirurgische reconstructie vaak aangewezen om de complicaties zoals sequestratie en obstructie van de luchtwegen te voorkomen. Kleine losse fragmenten kunnen het best verwijderd worden om het risico op sequestratie te verminderen. Grotere fragmenten en

2 fragmenten die nog vast zitten in het periost worden aan intact bot gefixeerd. Bij een enkelvoudige fractuur is de stabiliteit na reductie bepalend of fixatie nodig is of niet.

Tijdens de operatie van het paard werd een huidflap gemaakt. Vervolgens werd gespoeld en een debridement van de fractuurlijn uitgevoerd. Het verplaatste distale stuk werd gereduceerd en een locking compression plate, met 9 schroeven, werd gebruikt voor fixatie. In de literatuur werd ook een fixatie met polidioxanone of roestvrij staal beschreven. Een alternatief is het FlapFix systeem. Postoperatieve radiografische opname (fig. 4) toonde een goede reductie van de neusbeenderen met de plaat en schroeven. Na de operatie werd het paard zes dagen in de kliniek opgenomen. Postoperatieve behandeling bestond uit breedspectrum antibiotica, NSAIDs en verversen van het stentverband.

De prognose voor deze fracturen is in het algemeen goed, omdat de betreffende plaats een goede doorbloeding en relatief weinig druk heeft. Terugkeer tot het vroegere prestatieniveau is mogelijk. Het cosmetisch resultaat is afhankelijk van de ernst van de verwonding en keuze van therapie, vaak met goede, zelfs uitstekende resultaten.

INTRODUCTION

Trauma is the most frequently reported form of all equine nasal cavity and paranasal sinus disease (Boulton, 1985). Skull, and more specifically facial fractures due to collisions with stationary objects are quite common in horses (Caron et al., 1986; Ragle, 1993; Dowling et al., 2001, Turner, 1979). These fractures usually involve the frontal, nasal and maxillary bones, zygomatic process of the frontal bone, and the bones forming the orbital rim (Beard, 1998; Turner, 1979). The high incidence of these fractures is associated with the temperament of horses. As horses are flight animals, they often respond to situations detected as danger by running, pulling back and exaggerated head movements, contributing to this relatively high risk of facial fractures (Barber, 2005). The facial bones are prone to fracture because of the small cortical bone mass in combination with little overlying tissue providing protection (DeBowes, 1996).

Trauma involving distal limb and skull fractures are distressing for the horse and owner. Different clinical signs may be associated with nasal fractures, and severe epistaxis and dyspnea are not uncommon if the fracture results in a fragment wedged in a depression (Ragle, 1993). Initial treatment in the field is crucial to the final success of any repair. Stabilization and medical management may be needed before referral for more definitive treatment. Emergency management of skull or facial fractures in the field has been addressed less extensively than management of fractures of the appendicular skeleton, but many guidelines are similar and can be used for several types of trauma (Mudge and Bramlage, 2007). In contrast to these more dramatic events, minor fractures may go unnoticed for days.

Proper treatment of trauma is dependent on an adequate diagnosis. This may be complicated by the complex anatomy of the equine skull, including the large size and complexity of the paranasal sinuses and the difficulties of access (Freeman, 2003). Fortunately, there are several tools available to help in achieving accurate diagnosis. Still, knowledge of the complex system is important, as analysis and interpretation of skull radiographs are difficult tasks. Nowhere in the skeleton is there greater structural variability, more superimposition and different opacities.

Surgical repair is traditionally performed by elevating the fracture fragments and determining if additional support is required. Wire fixation is a commonly used technique (Caron et al., 1986; Ragle, 1993; Turner, 1979; Turner, 1982; DeBowes, 1996). Plate fixation has also been described (Auer, 2000; Dowling et al., 2001; Burba and Collier, 1991) and was used in this case.

This case report describes diagnosis and surgical treatment of a horse with a depression fracture of the nasal bones.

1. CASE HISTORY

1.1. ANAMNESIS

A warmblood gelding was presented at the Department of Surgery and Anaesthesiology at the faculty of veterinary medicine of Ghent University on 08/10/2013. The horse is used for competitions in eventing. The horse had panicked during aquatraining, and in an effort to escape he hit an iron object with his head. Initially there was a small amount of blood coming from both nostrils. A local veterinarian treated the horse with a corticosteriod (dexamethasone) and a non-steriodal anti- inflammatory drug (meloxicam, Metacam®) intravenously. As the bleeding persisted during the night, the horse was brought to the Faculty of Veterinary Medicine at Ghent University for further treatment.

1.2. CLINICAL EXAMINATION

When the horse arrived at the clinic he was alert, with bilateral epistaxis, and an external deformation was visible. The left nostril was bleeding profusely and the right mildly. Abnormal respiratory sounds indicating certain degree of obstruction of the upper airways were obvious, yet with airflow through both nostrils. A general clinical examination was performed to evaluate his condition: heart rate of 45 beats per minute, respiration rate of 22 per minute, pink mucosae, a capillary refill time of 2 seconds and body temperature of 38,8°C.

Visual inspection and palpation revealed the presence of a transverse depression fracture of 2-3 cm at the rostral part of the nose. Involvement of maxillae and conchae was possible. A diffuse swelling rostral to the lesion was seen. The affected area was mildly painful on palpation.

A blood sample was taken, and the horse’s hematocrit was 38 volume percent.

1.3. INITIAL TREATMENT

30 ml of Benzylpenicilline procaine (Penikel®) was administered intramusculary and an NSAID (Flunixin meglumine, Finadyne®) intravenously. Phenylephrine was bilaterally injected intranasal to produce vasoconstriction and limit bleeding. To keep the horse calm he was mildly sedated with an alpha 2 agonist (detomidine, Domosedan®). A bandage was introduced in the left part of the nasal cavity whereas the right side was left open to maintain adequate airflow. He was shaved as preparation of emergency tracheotomy if needed during the following hours. The horse’s heart rate, respiration rate, temperature and bleeding were closely observed. The introduced bandages seemed to be insufficient to stop the bleeding, and his hematocrit decreased to 24 during the night. Hereby he was treated with an antifibrinolytic drug (Transhexamic acid, Exacyl ®) and new bandages were introduced in the nose, which gained control over the bleeding.

Further examination and treatment was planned to follow after stabilization the next morning.

1.4. MEDICAL IMAGING

1.4.1. Radiography

On 09/10/2013, radiography was performed (Fig. 1) to evaluate the fracture and possible involvement of sinuses and visceral cranium. A standing Left-Right Lateral view of the skull confirmed an acute depression fracture with mild misalignment of the nasal bones. Involvement of sinuses was evident by the presence of fluid lines visible in the rostral compartments.

Figure 1. Radiography: Left-right lateral view of the skull showing a depression fracture of the nasal bones. (Source: Dept. of MI, Ghent University, 2013)

1.4.1. Computed Tomography

Pre-operative CT was performed under general anesthesia. Figure 2 shows an axial image at the level of the lesion. Number 1 indicate the nasal bones where a fracture is seen, with a depression of the left nasal bone.

1: Nasal bones 2: Superior labii levator muscle 3: Ventral nasal conchal sinus 4: Dorsal concha 5: Ventral nasal conchal sinus

6: Nasal septum 7: Common nasal meatus 8: Infraorbital canal 9: Ventral concha 10: Ventral nasal meatus 11: Maxillary bone 12: PM3 13:Palatine process of maxillary bone 14: Endotracheal tube 15: Buccinator muscle

Figure 2: CT, transverse section at the level of the second premolar. (Source: CT-MR Unit, Dept. of MI, Ghent University, 2013)

With a series of axial images, three-dimensional images were created. Figure 3 shows three- dimensional lateral and dorsal views of the patient’s skull. The left os nasale was fractured transversely and the distal fragment was depressed by 1,7 cm. The right os nasale had a transverse fracture line as well, but was not displaced. The dorsal conchae were severely bruised. The maxillary bone was not involved.

Figure 3: Three-dimensional image. Left: Lateral view. Right: Dorsal view. (Source: CT-MR Unit, Dept. of MI, Ghent University, 2013)

1.5. DIAGNOSE

A transverse depression fracture of both nasal bones caused by blunt trauma, with severely bruised conchae.

1.6. TREATMENT

For initial treatment prior to surgery, see chapter 1.3.

1.6.1. Surgery

On 11/10/13 the horse was operated. Prior to surgery he was deprived of any food for twelve hours, with access to water. He was sedated with xylazine (Xyl-M®), and induced with ketamine and midazolam (Dormicum®). Isoflurane was used as inhalation anesthesia. The horse was given anti- tetanos serum subcutaneously, aninfusion of Ringer lactate ®, a constant rate infusion of romifidine (Sedivet®) and 30 ml Benzylpenicilline procaine (Penikel®) intramusculary. The surgery was performed with the horse in right lateral decubitus.

A curvilinear incision was made through the skin over the left nasal bone, and a skin flap was made. The fracture was debrided and rinsed. Then the displaced fragment was repositioned. To bridge the fracture a 9 hole 3,5 Locking Compression Plate was placed. 4 cortical screws were used, two in load and two neutral, besides 5 locking screws. The subcutis was sutured with continuous stitches of vicryl 2-0. Closure of the skin was obtained by simple interrupted stitches of maxon 2.0. The center of the flap was attached to the periostal tissue by two simple sutures. After closure, a stent was fixed over the wound with adhesive spray. Postoperative X-Ray showed good alignment of the nasal bones and no fluid lines in the rostral sinus compartment (Fig. 4).

Figure 4. Postoperative radiography: Left-right lateral view of the skull showing good reposition of the nasal bones with a plate and screws. (Source: Dept. of MI, Ghent University, 2013)

1.6.2. Follow-up

The horse was hospitalized for six days after surgery. Postoperative care consisted of treatment with antibiotics, NSAID’s and refreshing the stent. The first two days after surgery he was given 80 ml of gentamicin once a day, 10 x 10^6 units sodium penicillin twice a day, and two grams phenylbutazone daily through a venous catheter. On the third day the intravenously administered antibiotics were substituted by an oral paste with doxycycline. The days following the operation the horse had a good clinical evolution, and the wound healed nicely.

The horse left the clinic on 17/10/13. He was stabled for one month and walked by hand on a daily basis. Care was taken to prevent pressure of the nose band on the nose bones. The first two weeks at home the antibiotic therapy with doxycycline was continued.The owner contacted a local veterinarian for the follow-up of the horse. An endoscopic evaluation was performed approximately four weeks after surgery. Due to soft tissue swelling, non-steroidal and steroidal anti-inflammatory drugs were administered. The wound continued to heal nicely, and only mild external scars are visible. Three months after surgery the owner started very light recreational work of the horse, continuing for two months. The owner experienced that the horse was negatively affected by persistent narrowing of his airways, confirmed by a new endoscopic examination five months after surgery. Another treatment with NSAIDs was given and the horse rested for a couple of weeks. The following months they continued with recreational work such as light dressage and going out for a walk. After 13-14 months the horse was gradually reintroduced to his former training regime. The owner reported that there are no breath sounds in rest, but when the horse is trotting or cantering some abnormal sounds are present. The intensity of the breath sounds have decreased the last months, but will probably persist. The owner hopes and believes that the horse will return to his former performance level. He keeps in mind that he does not know in which extent this will affect the horse in the future. Even though the owner is happy with the results, he does not think the horse would be a candidate for sale due to some persistent abnormal breath sounds.

2. LITERATURE REVIEW

In order to diagnose and treat trauma of the head, knowledge of the complex equine skull is crucial.

2.1. ANATOMICAL CONSIDERATIONS

The skull consists of several bones, forming the cerebral cranium around the brain, and a visceral cranium as the basis for the face. The mandible and hyoid bone can also be considered as parts of the visceral cranium (Auer, 2012). Figure 5 illustrates the different osseous parts of the horse’s skull.

1: Os incisivum, 2: Os nasale, 3: Os frontale,

4: Maxilla, 5: Os lacrimale, 6: Os zygomaticum, 7: Os interparietale, 8: Os parietale, 9: Os temporale, 10: Pars petrosa and pars tympanica of the os temporale, 11: Os sphenoidale, 12: Os occipital, 13: Os palatinum, 14: Vomer, 15: Os pterygoideum, 16: Mandibula, 16a: Pars incisive, 16b: Margo interalveolaris, 16c: Pars molaris, 16d: Ramus mandibulae, 16e: Processus condylaris, 16f: Processus coronoideus

Figure 5: Diagram of the bones forming the equine skull. (Adapted from Auer, 2012)

The large nostrils form the beginning of the respiratory system, opening into the nasal cavity. They are supported by the alar cartilages for rigidity and by muscles for mobility, in order to be able to open maximally during exercise and provide high airflow rates. This is important because the horse is an obligate nasal breather and rarely breathes orally (Holcombe and Ducharme, 2008).

The nasal cavity is separated in two parts by the medial nasal septum and the vomer bone. The septum has a cartilaginous rostral part and bony caudal part, covered with a highly vasculated mucosa (Robinson and Furlow, 2003). In each nasal cavity, two major nasal conchae divide the nasal passage into the ventral, middle, dorsal and common meatus (Nickels,2012). The ventral is the largest, and the major pathway for air passage between the external nares and the nasopharynx. The dorsal meatus extends into the area of the endoturbinates. Here, the structure of the ethmoid enlarges the mucosal

10 surface of the nasal cavity (Robinson and Furlow, 2007), providing a large surface area for heat and water exchange (Lekeux et al., 2014).

Besides the nasal cavity, the voluminous visceral cranium forms the oral, ocular and sinus cavities (Auer, 2012). The horse’s paranasal sinus system consists of seven pairs of sinuses, as illustrated in figure 6. These are the rostral and caudal maxillary sinuses, frontal, sphenopalatine, dorsal, middle and ventral conchal sinuses (Robinson and Furlow, 2007). These all communicate with the nasal cavity. The maxillary is the only one with direct communication, while the rest are connected through the maxillary sinus (Nickels, 2012).

a: frontal sinus b: ethmoid mass c: frontomaxillary opening d: dorsal bulla of ventral conchal sinus e: caudal maxillary sinus

f: dorsal conchal sinus g: rostral maxillary sinus H: facial crest i: infraorbital foramen j: course of nasolacrimal duct

Figure 6: Diagram of the equine skull with location of the paranasal sinuses. (Adapted from Nickels, 2012)

The facial bones have a thin cortical bone mass, and there is little overlying soft tissue for protection (DeBowes, 1996). The nasolacrimal duct is situated in the bony lacrimal canal adjacent to the maxillary sinus (Wilson and Levine 1990).

2.2. INJURY

A review of 85 cases conducted by Boulton (1985) found that trauma was the most frequently reported form of equine nasal cavity and paranasal sinus disease. Diseases and trauma of the upper respiratory tract are recognized as common problems in the horse. The most common causes of skull fractures in the horse are direct trauma associated with a kick or running onto stationary objects. The

11 frontal, nasal, and maxillary bones are the bony parts that are most commonly involved (Beard, 1999). Most nasal bone fractures are depression-type fractures (Farrow, 2006). Fracture of the nasal bones can be associated with degloving injuries of the overlying soft tissue (Debowes, 1996). Besides osseous, and skin injury, other soft tissue might be damaged. Hemorrhages resulting from upper airway injuries frequently originate from the nasal septum and conchal veins (Lekeux et al., 2014). Even in cases where the overlying skin is intact, fractures of the nasal bones may be associated with interior soft-tissue injury (Farrow, 2006).

2.3. DIAGNOSIS

An accurate diagnosis is necessary to implement the correct treatment.

2.3.1. Physical examination

An initial complete history and physical examination will give valuable information in the evaluation of the case. Evaluating colour, moistness and capillary refill time (CRT) of the mucous membranes can give important information about the blood circulation of the horse (Roy and Lavoie, 2003). Severity of blood loss and other fluids should be estimated. Hemorrhage can be significant even with less severe fractures as the nasal bones are highly vasculated. Pale mucous membranes, prolonged CRT or significant tachycardia (>60 beats per minute) signals a need for medical stabilization before treatment or referral. Packed cell volume measurements give a more objective impression of the severity of blood loss (Mudge and Bramlage, 2007). In stabile patients, evaluating attitude, body condition, and general health should not be forgotten (Roy and Lavoie, 2003).

In case of respiratory distress, severity should be evaluated and treatment started immediately if necessary. Obstruction due to trauma to the upper respiratory tract can usually be determined on the basis of breath sounds caused by resistance to passage of airflow. A large blood clot or major narrowing secondary to fractures of the nasal bones or nasal septum may cause the respiratory distress (Burba and Collier, 1991). In these and other cases of upper airway obstruction, inspiratory dyspnea is often more pronounced than expiratory dyspnea. Further, the amount of effort necessary to breathe can give an indication of the severity of the dyspnea (Schaer and Orsini, 2008). In case of serious instability over nasal passages or paranasal sinuses, movement of skin and underlying bone may be seen as a result of negative inspirational pressure (Ragle, 1993).

Clinical signs depend on the severity of injury and whether the nasal passage, paranasal sinuses, or orbital rim is involved (Barber, 2005). In cases of trauma to the nasal bones, asymmetry might be readily evident, but it can be difficult to identify fresh fractures which are non-displaced or cracked (Farrow, 2006). This is why palpation of the horse’s head for asymmetry is important next to visual examination to discover irregularities (Roy and Lavoie, 2003). Soft tissue swelling might cover minor fractures, leaving them unnoticed for days (Dowling et al., 2001). Also detachment of overlying skin from the bone can maintain a normal facial contour. Progressively, a hematoma and fracture callus can produce a firm subcutaneous swelling (Freeman, 2003). Deformities, draining tracts, nasal discharge and epistaxis are common signs (Boulton, 1985). Characteristics of the nasal discharge and whether it is uni- or bilateral often provide insight into location and nature of the cause (Roy and

Lavoie (2003). Further, crepitus and subcutaneous emphysema may indicate communication of the fracture with the air-filled nasal cavity or sinuses (Dowling et al., 2001). Interventions to limit blood loss and stabilization of the patient take priority over the medical examination outlined in this section.

Periocular or ocular involvement, besides neurologic deficits caused by the trauma to the skull should be examined. Neurological signs may occur several hours after the initial injury (Tremaine, 2004). Further investigation with direct sinus endoscopy can be used to visualize fragments within the sinuses, though the visibility is mostly impaired by the hemorrhage (Tremaine, 2004), and medical imaging is recommended.

2.3.2. Medical imaging

2.3.2.1. Radiography

In the diagnosis of equine respiratory diseases, radiography can be helpful (O’Brien and Biller, 1997). In many cases, the fracture is more extensive than the external soft tissue injury would suggest (Freeman, 2003). A radiological examination can detect latent or non-displaced fractures that are not seen externally (Tremaine, 2004). In standard radiographs, the x-rays are passing through the patient and depict a three-dimensional object as a two dimensional image. Hereby, the main limitation is that overlying structures on the path of the x-rays will be superimposed in the image (Fio and Koblik, 1995). Advantages of conventional radiography are its low cost, and the suitability for imaging the nasal cavity and sinuses, with gas and bone as major structures (Roy and Lavoie, 2003).

A radiographic assessment often begins with a full-length lateral image of the head. The frontal and maxillary sinuses can be imaged in a laterolateral (LL) view (Roy and Lavoie, 2003), including fluid lines from blood within the involved sinuses (Weller and Sinclair, 2012). A dorsoventral (DV) or ventrodorsal (VD) projection can better visualize the other sinuses (Roy and Lavoie, 2003). When a lesion is observed in a LL view, a DV/VD projection is helpful to identify which side is affected. Further, the rostral maxillary sinus and ventral conchal sinus are superimposed on a laterolateral radiograph, while a DV/VD projection allows differentiation (Weller and Sinclair, 2012). Oblique views are suited for evaluating teeth roots and separating the temporomandibular joints. If necessary, customized views can be made to profile surface or interior abnormalities (Roy and Lavoie, 2003). In cases of skull fractures, radiography is most useful for diagnosing subtle depression fractures that are not obvious on clinical examination (Ragle, 1993). Turner (1979) and Caron et al. (1986) report that radiography has limited value in exact evaluation of the extent and nature of skull fractures.

2.3.2.2. Computed tomography

As computed tomography (CT) scanners are becoming more affordable, CT is commonly applied in equine medicine (Roberts and Graham, 2001). Still, it is considerably more expensive than conventional tomography. CT eliminates superimposition of overlying structures, and is considered more effective than conventional radiography in imaging structures such as in the complex nasal and paranasal system of the horse (Solano and Brawer, 2004). Roy and Lavoie (2003) point out that there is no better way to depict the interior of the horse’s head and fracture configurations than with CT.

Series of two-dimensional slices give cross-sectional images of the scanned body part. The axial images can be combined and advanced software can render three-dimensional images. Additionally, compared to the inability of the conventional radiograph to distinguish between two tissues with similar density, CT provides a higher degree of soft tissue contrast resolution (Weller and Sinclair, 2012). Also CT uses x-rays, but contrary to the static probe in conventional radiography, the tube is rotated around the patient. The size of the horse is a dilemma as these apparatus are developed for humans. Using a custom-made large table, the head, parts of the neck, and extremities of the horse can be imaged (Fio and Koblik, 1995). Hereby, general anesthesia is often required to perform CT, and benefits of the examination should outweigh the risks associated with the procedure (Solano and Brawer, 2004). Some institutions have CT scanners that are modified to accommodate the standing sedated horse, eliminating the need for general anesthesia, reducing the risks and costs (Porter ad Werpy, 2014).

2.4. TREATMENT

2.4.1. Initial management of the injured horse

It is important to keep the injured horse as calm as possible, and sedation is generally required for diagnostics such as radiography. Recognizing signs of shock and hypovolemia is crucial, as the effects of sedation may be enhanced by these conditions. In these cases phenothiazine tranquilizers should not be used because they are likely to exacerbate hypotension (Mudge and Bramlage, 2007). The use of xylazine or other tranquillizers causing lowering of the head or an increase in upper airway resistance should be used carefully. Applying ice packs to the external nasal surface can help decrease swelling of the affected area. A spray of lidocaine with 2% epinephrine, or phenylephrine can be used to yield vasoconstriction, decreasing swelling and bleeding. The head of the horse should be kept at the level of the shoulder or higher. Hereby, tying or supporting the head in a high position might be indicated if the horse tolerates it. Tetanus toxoid or antitoxin might be administered in any case, most importantly if no previous vaccination. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as phenylbutazone or flunixin meglumine are the most commonly administered anti-inflammatory therapy for musculoskeletal injury in horses, and give appropriate analgesy for the patient (Mudge and Bramlage, 2007).

If more severe swelling of the nasal cavity is expected, a small nasal tube might be introduced to keep a patent airway (Schaer and Orsini, 2008). In case of more severe dyspnea, an emergency tracheotomy should be carried out immediately (Greet and Ramzan, 2011). In this procedure an airway bypassing the nasal obstruction is established, providing a direct route for manual ventilation. Hereby, tracheotomy is also used to “rest” an inflamed upper respiratory tract (Wilson, 2006). A tube can be introduced between the upper and middle third on the ventral midline of the neck. If time allows it, the site should be prepared carefully. Trough palpation, a suitable area is found and clipped (Schaer and Orsini, 2008). A local anesthetic drug is injected into subcutaneous tissue over the trachea. After scrubbing, a five (ibid.) to twelve cm (Ducharme and Cheetham, 2014) vertical incision through the skin and subcutaneous tissue is made with a scalpel. The underlying paired muscle bellies of the sternomandibularis, sternothyroideus, and sternohyoideus muscle should be incised and separated to each side, exposing the tracheal rings (Wilson, 2006). A horizontal incision in an annular ligament into the tracheal lumen, without removal of portions of the tracheal ring, is sufficient to allow passage of the tracheotomy tube. The tube must be secured to prevent it from moving (Ducharme and Cheetham,

2014). If the horse’s life is in danger, any sharp object is used to cut, and any available tube can be introduced to save the horse’s life, rather than losing time on an ideal sterile technique (Schaer and Orsini, 2008). Tracheotomy tubes require almost continuous monitoring and management, such as removing exudate and blood clots (Wilson, 2006). Complications associated with tracheotomy are usually linked to the primary problem rather than the tracheotomy itself. However, subcutaneous emphysema, hemorrhage and inflammation are relatively common (Freeman, 1991).

In general, a fracture should be considered open if a wound is present, even when direct communication with the fracture seems unlikely. Skull fractures that communicate with the nasal or oral cavity as well as sinuses are also considered open, as bacterial contamination from the airway occurs. In these cases, a broad-spectrum antibiotic therapy, such as the combination of potassium penicillin and gentamicin, should be initiated (Mudge and Bramlage, 2007).

Blood retained in the paranasal sinuses is an excellent nidus for bacterial infection. Lavage of the sinus can be performed to reduce the risk of sinusitis and empyema. The lavage can be performed with the patient standing, or as a part of surgery under general anesthesia. A portal in the frontal sinus can be created with a 6 mm Steinmann pin, followed by infusion of saline 0.9% or lactated Ringer’s solution trough a silastic drain (Auer, 2006).

2.4.2. Conservative treatment

In a case of stable, non-displaced depression fractures that do not interfere with the orbit or airways, conservative treatment is an option, at least if cosmetic appearance is not a priority (Barber, 2005). Non-displaced fractures often involve skull sutures, and are generally recognized to heal spontaneously. Cases that do not require treatment, will generally heal quickly because of an abundant blood supply and minimal interference by movement of the animal (Boulton, 1985). Nevertheless, Barber (2005) encourages reconstruction to diminish the risk of complications. In some cases the cosmetic result or functional outcome of conservative management is not satisfying, leaving surgery as only option. Further, even when the fracture itself heals nicely, interior soft tissue disruption might become a problem. Boulton (1985) found that the cases where complications occur are most commonly those in which the mucosa of the turbinates or nasal cavity is compromised. The undiagnosed soft-tissue disruption may lead to infections (Farrow, 2006), where complications such as sinusitis, necrosis, osseous sequestration, sinus- or nasal fistulae can be expected (Freeman, 2003; Miller et al., 1978). Facial deformity and nasal septal thickening are also seen (Boulton, 1985; Turner, 1979). Excessive callus remodeling, a process that can remain active up to two years following trauma, may be a problem by interfering with air flow or sinus drainage (Mudge and Bramlage, 2007).

If the underlying tissues are considered to heal nicely without surgical intervention, the skin lesion may be closed, following the general principles of wound management (Barber, 2005). Stall rest and careful handling is recommended in the period following trauma.

2.4.3. Surgical treatment

In cases where external damage is seen, surgery should be performed to reconstruct a functional state. Viable bony fragments are reincorporated (Boulton, 1985), and removal of loose fragments might be necessary to decrease risk of sequestration and sinusitis (Ragle, 1993). Reconstruction of the nasal bridge is crucial to restore a normal airflow in cases of dyspnea, especially for horses intended for an athletic career (Tremaine, 2004)

Fractures of the nasal bones should be considered open, even when the overlying skin is intact, due to the fact that penetration of the sinus and nasal cavity usually occurs (Nickels, 2012).

Stabilization of the patient for 24 to 48 hours following injury is advised. Nevertheless, contraction of lacerated skin occurs rapidly and waiting too long may hereby hinder attempts to achieve primary wound closure (Tremaine, 2004). Postponing repair more than a few days can also result in difficulty achieving reduction (Auer, 2012). If the fracture is chronic with fibrosis and callus formation, orthopedic wire or an orthopedic bone saw may be needed to cut fragments that have started to heal in an abnormal position (Caron et al., 1986).

Through the defect, blood clots and small fragments without periostal attachment should be removed to decrease the possibility of sequestrum formation (Barber, 2005; Tremaine and Freeman, 1990). Attempts are made to preserve periosteal attachment to the fragments. The fracture site is debrided thoroughly (Nickels, 2012), followed by flushing with saline (Barber, 2005). Successful surgical reconstruction of more extensive fractures may require a large curved or S-shaped skin incision for complete field exposure (Tremaine, 2004).

In cases of depression fractures, viable fragments should be elevated and fixation is considered if support is required to keep the fragment stable. A periosteal elevator, Langenbeck retractor or Steinmann pin can be passed through the defect to elevate depressed fragments (Tremaine and Freeman, 2007). Holes can be drilled or made with a Steinmann pin in adjacent undamaged bone and the end of a Steinmann pin can be inserted as illustrated in figure 7A. The pin is bent at a suitable angle to give a broad area of contact when inserted into the drilled hole. The length of the bent end should be approximately the same as the width of the depressed bone segment (Beard, 1999).

Figure 7: Elevation of depressed bone fragment by insertion of a Steinmann pin through a small drill hole (A), followed by fixation with wire loops through drilled holes (B). (Source: Auer, 2012)

An alternative is to insert bone screws into the depressed fragments and hereby elevate by traction. In some cases, elevated fragments wedge firmly together in their normal position, leaving fixation unnecessary (Turner, 1979., Turner 1982., DeBowes 1996).

Large or unstable fragments should be attached to intact adjacent bone, and wire fixation is the most commonly recommended technique (Caron et al., 1986; Ragle, 1993; Turner, 1979; Turner, 1982; DeBowes, 1996).Stainless steel wire can be used to apply cerclage sutures in 0.8 to 1 mm drilled holes (See figure 7B). These should not be over tightened, because this can break the soft bone. Alternatively, absorbable monofilament material could be used. In a study conducted by Schaaf et al. (2008), 10 horses with severe distortion of the facial contour, polydioxanone sutures were successfully applied. They outline that sutures can avoid expenses and complexity of plate fixation in selected cases. Further, it did not cut through the bones when they were tightened, and it has excellent handling properties. The sutures provided stable fixation of the elevated fragments. Polydioxanone retains its tensile strength for up to 56 days. Due to degradation, there are no sutures to remove, and the risk of sequestration or infection is greatly diminished.

Alternatively, absorbable suture material can also be used to suture only the periosteum. However, this thin layer may be stripped from the fragments, necessitating complementary wire loops or other fixation techniques (Barber, 2005).

A more stable alternative to wire loops is the FlapFix system (See figure 8), developed for fragment fixation of flat bones in humans. The FlapFix implant consists of a round titanium plate, which is placed underneath the fractured bone. This plate is connected to a thin orthogonally oriented titanium tube that exits through the fracture line or the osteotomy cut. Externally, a cloverleaf-shaped plate is attached to the tube and pressed firmly against the internal plate by pressing the handle. The tube is cut at the level of the external plate. The advantages of this system include the rapid application and increased contact area of the implant with the bone, but has a high cost compared to wire loops (Auer, 2012).

Figure 8: Fragment fixation by the FlapFix system. (Source: Auer, 2012)

Dowling et al. (2001) suggest that cuttable bone plates is a good alternative to interfragmentary wiring in cases of comminuted fractures of the facial bones, even when fractures are open. To repair an unstable and/or compound depression fracture of the nasal bones with substantial bone loss, Burba and Collier (1991) report that a 5-hole T-plate is a good option. It should result in satisfactory bone healing, facial contour, and airway function. When implants are used, aggressive debridement and use of antibiotics is crucial to prevent infection of the implant (Barber, 2005).

Trauma leading to open comminuted fractures with large bony defect may yield a concavity if not reconstructed. To diminish the concavity, the defect may be bridged with a synthetic mesh, and then covered with skin, giving a better cosmetic and functional result (Martis and McIlwraith, 1981). Full thickness defects into sinus or nasal, may result in sinocutaneous or nasocutaneous fistula. To close such defect into the frontal sinus, Campbell and Peyton (2008) described how a transposition flap of the temporalis muscle can be used for restoration of a functional covering and excellent final appearance. Dart et al. (1994) report a successful reconstruction of a maxillary sinus defect in a horse using a levator nasolabialis muscle flap. In both cases the suitable muscle is dissected free from surrounding tissue maintaining a base, and rotated over the defect. They are fixed in their new position and the skin is closed. Use of relief incisions may be necessary to achieve closure of the skin without too much traction on the skin.

According to Schumacher et al (1985) asinocutaneous or nasocutaneous defect can be closed by a single or double periosteal flap technique. The flaps are prepared in the area adjacent to the bone defect, inverted, and drawn over the defect. Then they are sutured to each other or to the periosteum of the opposite side. The goal of this periosteal flap is formation of new bone by the cambium layer of the periosteum. They performed this technique in two horses with such defects, and report that acceptable cosmetic appearance was restored in both horses. Resistance to penetration of a needle and ultrasonic scanning demonstrated bony bridging in one horse.

In all cases, involvement of other structures should be investigated. When a fracture is located near the medial canthus, the nasolacrimal duct should be controlled for damage. In case of disruption, an attempt to salvage the nasolacrimal canal should be made. If this is not possible, Wilson and Levine (1990) report that the damaged nasolacrimal duct can be successfully stented into the lumen of the maxillary sinus, creating communication between proximal part of the duct and the maxillary sinus. After trauma to the nasal bones, thenasal conchae and septum might be injured. When the septum is deformed, thickened, or remaining segments are suspected to become thickened and hereby occlude nasal passage, removal of a part may be indicated. It is important to remain sufficient septum to support the alar folds and nostrils (Freeman 2012).

Before closure, placing a drain may be indicated when there is extensive exudation into the paranasal sinuses, allowing drainage and hereby preventing development of sinusitis. Undermining the skin or making relief incisions a few cm from the wound may be required to close without excessive tension (Barber, 2005). The incision is closed in two layers. Periosteum is re-apposed when possible, and sutured with absorbable material. A continuous intradermal suture pattern helps reapposing the skin edges before suturing the skin.

2.4.4. Aftercare

Postoperatively, most cases need minimal care (Tremaine, 2004). Applying a pressure bandage and keeping it for 3-4 days will help protect the area and minimize postoperative swelling (Waguespack and Taintor, 2011). Further, NSAID’s such as phenylbutazone will decrease inflammatory pain and swelling. Systemic administration of broad-spectrum antibiotics before and for 5-6 days after surgery is recommended to prevent infection, most importantly if implants are used (Nickels, 2012). Normally, the implants are not removed unless infection or migration of the used implant material is seen (Tremaine, 2004).

2.5. PROGNOSIS

Due to the high vascularity of the affected area, and relatively low loads placed on these bones, prognosis to complete recovery in horses with fractures of the nasal bones is good (Tremaine, 2004). Usually, return to previous level of performance is possible. The cosmetic outcome depends on the stability of the fracture, whether conservative treatment is chosen or surgical management with reduction and fixation is performed. The functional and cosmetic outcome depends on severity of the injury and the chosen treatment, usually with acceptable and often excellent results (Auer, 2012).

DISCUSSION

As seen in this case, facial fractures in horses are quite common, and the facial bones most commonly fractured include the nasal and frontal bones, and the maxilla (Beard, 1999). The fractures are typically depressed, open and often highly comminuted, thereby invading the nasal cavity, the frontal or the maxillary sinuses. In this case the fracture was depressed, but it was not comminuted.

As part of the initial treatment the horse received Benzylpenicilline procaine intramuscularly. This is a beta-lactam antibiotic, which is very active against gram positive bacteria and anaerobes, but only partly active against gram negative bacteria. This is a good option for intramuscular injection as it is slowly absorbed into the circulation, providing prolonged concentrations of benzylpenicillin. After surgery a broad-spectrum antibiotic therapy with the combination of potassium penicillin and gentamicin was given. It might have been advantageous to give these antibiotics from the beginning to ensure a broad spectrum of defense already before starting the surgery.

Detomidine was given intravenously on arrival at the clinic to keep the horse calm. As mentioned, this and other alpha2 agonists should be administered carefully because it causes lowering of the head and increased blood pressure in the nose (Schaer and Orsini, 2008). The horse was only mildly sedated, and he was observed carefully, so this was presumably no problem. Further, hay was given in a hay rack to make sure the horse kept his head high, at least parts of the time. Here, tying the head up might have been an alternative option to maintain a more permanent raised position of the head. Also ice packs may have been used to reduce the swelling of the soft tissues. Nevertheless, both for tying up and applying ice packs, care should be taken not to put pressure on the injured site, and it is no good option if the horse gets excited by these interventions. Hereby, an evaluation should be made in each case, and no general rules are valid for all cases. According to the reviewed literature, a spray of lidocaine with 2% epinephrine, or phenylephrine should be used to yield vasoconstriction, decreasing swelling and bleeding. Phenylephrine was bilaterally injected intranasally. Flunixin meglumine, an NSAID, was administered intravenously, which was indicated for pain management and reducing inflammation. NSAIDs also reduce fever, but even though the horse had an elevated body temperature of 38,8 (Ref: 37,0-38,0), fever is not a major point of focus. Rose et al. (1988) report that the exercising horse produces a tremendous amount of metabolic heat. This byproduct of potential energy can raise body temperature from 37 degrees at rest to 42 degrees in a matter of minutes (Carlson, 1983). Even though this horse was not exercising, the elevated temperature was presumably due to stress and the increased amount of effort to breathe through the constricted airways.

In cases of depressed nasal fractures with impairment of breathing, performing a tracheotomy might be lifesaving (Schaer and Orsini, 2008). This was not considered necessary when the horse arrived at the clinic. Still, as the horse had dyspnea, a suitable area was found and clipped as preparation in case the situation got worse and needed quick intervention.

The symptoms as seen in this horse; epistaxis, external deformation and dyspnea are very typical for such trauma. In combination with radiography there was no doubt of the diagnosis. Rhinolaryngoscopic examination is normally used in cases of abnormalities of the respiratory tract (Freeman, 2003). Endoscopy was not considered useful in the presurgical evaluation in this case. Epistaxis would have hindered visualization in the nasal cavity and the quite severe dyspnea was a contradiction to introducing an endoscope.

For facial trauma, radiography is the most used diagnostic procedure. Although the images may be difficult to interpret, radiography does permit examination of most hard and soft tissues within the bony skull (Boulton, 1985). The radiological images confirmed a depression fracture with mild misalignment of the nasal bones. Involvement of the sinuses was evident by the presence of fluid lines in the rostral compartments. This means that there was communication with the airways and the fracture should be considered open. Still, there is no better way to depict the interior of the horse’s head and fracture configurations than with CT (Roy and Lavoie, 2003). The advantages of this technique do come with a higher cost. Additionally, general anesthesia is often required to perform CT, and benefits of the examination should outweigh the risks associated with the procedure (Solano and Brawer, 2004). In this case the CT was performed when the horse was under general anesthesia for surgery, indicating that the additional risk for CT was minimal.

In some cases conservative management of facial structures can provide a functional outcome, however, facial deformities are commonly reported complications. Surgical intervention is often indicated to reconstruct the facial contour, maximize airflow and decrease the risk of complications (Caron et al., 1986; Ragle, 1993). Viable bony fragments are reincorporated (Boulton, 1985), and removal of loose fragments might be necessary to decrease risk of sequestration and sinusitis (Ragle, 1993). Reconstruction of the nasal bridge is crucial to restore a normal airflow in cases of dyspnea, especially for horses intended for an athletic career (Tremaine, 2004). Sometimes fragments interdigitate well and maintain alignment after elevation (Wheat, 1975), but other fractures will need fixation to remain their stability.

Different reconstructive techniques have been described for facial fractures of the paranasal sinuses and nasal cavity. The use of suture material depends on the stability of the fractured fragments after reduction. In this case the fracture was fixated with a plate and screws. Dowling et al. (2001) suggest that cuttable bone plates are good alternatives to interfragmentary wiring in cases of comminuted fractures of the facial bones, even when fractures are open. According to Burba and Collier (1991) bone plates may lead to drainage, screw loosening, and removal of the implants might be required. Before closure, placing a drain may be indicated when there is extensive exudation into the paranasal sinuses, allowing drainage and hereby preventing development of sinusitis (Barber, 2005). This was not considered necessary in this case. The fluid within the sinuses prior to surgery was blood from the trauma, and significant bleeding into sinuses after surgery was not expected. Also infections around the plates are reported complications (Dowling et al., 2001). According to Auer (2006) nose fractures generally heal very well, and infection is not very common taken into consideration that these fractures are considered open.

Schaaf et al. (2008) report that using resorbable sutures for fragment fixation is not much used, but is an alternative to avoid the use of implants. Through their study they demonstrated that fixation with degradable polydioxanone suture should be considered as an alternative to stainless steel wire in equine skull fractures. They report that this material keeps its tensile strength for 56 days and union

21 typically occurs within four to six weeks (Schaaf et al., 2008). Another alternative for fixation was also mentioned. The advantages of the flap fix system is its rapid speed of application, increased stability compared to wiring, increased contact area and greater resistance to failure (Auer, 1996). The major disadvantage is the high cost (Auer, 2012). The surgeon reported that wiring was not considered for this case. Due to the location of the fracture it would not result in the best possible stabilization of the fracture fragments. Fixation with a plate and screws was considered the best treatment option (Vlaminck, 2014).

In contrast to wiring or appliance of the FlapFix system, reconstruction plates can be used to repair severely comminuted fractures, although this was not the case in our horse. Trauma leading to open comminuted fractures with large bony defects may be bridged with a synthetic mesh to diminish the concavity, and then covered with skin, giving a better cosmetic and functional result (Martis and McIlwraith, 1981). Also the periosteal flap technique (Schumacher et al., 1985) and the use of a muscle flap (Campbell and Peyton, 2008) have been described. In this case no defect had to be covered as the fracture aligned nicely after reduction and fixation.

Some complications have been described, but the literature also reports a surprisingly good outcome despite some contamination of the surgical site from the respiratory tract. Postoperative complications associated with repair of facial fractures are generally limited to implant failure and osseous sequestration (Debowes, 1996). The plate was not removed due to the absence of any complications. The use of this treatment should be considered as a good alternative to interfragmentary wiring for unstable fractures of the facial bones. Implant removal may be required in some instances (Dowling et al., 2001).

A good prognosis can generally be given for trauma similar to this case if surgical intervention is performed (Tremaine, 2004). The functional and cosmetic outcome depends on the severity of the injury and the chosen treatment, usually with acceptable and often excellent results (Auer, 2012). The cosmetic and functional outcome was considered very good and postoperative complications were minimal in this case. To give an indication of the prognosis, the desired level of performance has to be kept in mind. In this case it seems like the horse will be able to return to his former performance level. The sales value of the horse has probably decreased.

By the good prognosis and results in this case, it can be recommended to use this treatment plan in similar cases.

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GHENT UNIVERSITY

FACULTY OF VETERINARY MEDICINE

Academic year 2014 – 2015

Angular and Flexural Deformities in a Foal

Nathalie HILMO

Promotors: Prof. F. Pille Clinical Case report as a part Veterinary K. Deneut of the Master’s Dissertation

GHENT UNIVERSITY

FACULTY OF VETERINARY MEDICINE

Academic year 2014 – 2015

Angular and Flexural Deformities in a Foal

Nathalie HILMO

Promotors: Prof. F. Pille Clinical Case report as a part Veterinary K. Deneut of the Master’s Dissertation

PREFACE

I would like to express my very great appreciation to my promotor Prof. F. Pille for providing me this subject and for his guidance. I wish to gratefully acknowledge my second promotor, Veterinary K. Deneut for her constructive feedback and good help. I also want to thank Dr. I. Gielen for providing me with medical images for this case. I am particularly grateful to my boyfriend Sindre Stordahl for providing technical help and emotional support when I needed it the most. Marte Ingvild Stordahl has offered indispensable help with proofreading the paper, for which I am very grateful. Last, but not least, I would like to offer my special thanks to my family for encouragement and invaluable help throughout my whole study period. Last, but not least I would like to thank the people of Reproactief for their very good help.

TABLE OF CONTENTS

ABSTRACT ...... 1 SAMENVATTING ...... 2 INTRODUCTION ...... 4 1. CASE HISTORY ...... 6 1.1. ANAMNESIS ...... 6 1.2. CLINICAL EXAMINATION ...... 6 1.3. MEDICAL IMAGING ...... 6 1.4. DIAGNOSIS ...... 7 1.5. TREATMENT ...... 7 1.5.1. Surgical treatment ...... 7 1.5.2. Aftercare ...... 7 1.6. FOLLOW-UP ...... 7 2. LITERATURE REVIEW ...... 9 2.1. THE GROWING FOAL ...... 9 2.2. DEVELOPMENTAL ORTHOPEDIC PROBLEMS OF THE FOAL ...... 9 2.2.1. Factors contributing to DOD ...... 10 2.2.2. Angular limb deformities ...... 10 2.2.2.1. Etiopathogenesis ...... 10 2.2.2.2. Treatment ...... 12 2.2.3. Contractural deformities ...... 18 2.2.3.1. Etiopathogenesis ...... 19 2.2.3.2. Treatment ...... 19 REFERENCES ...... 27

ABSTRACT

A foal was presented with carpal valgus and a contractural deformity, both most prominent at the level of the left front carpus. The owner reported that it was born with these deformities, and while the retraction was reduced during its two first weeks of life, the valgus had become worse. Contractural deformities are common orthopedic problems in foals, and are the results of relatively too short tendons compared to the skeleton. Congenital cases often resolve spontaneously or can be treated successfully without surgery. Inherited rapid growth in response to high energy nutrition play an important role in the development of acquired contractions, and balancing the nutritional intake is a key in the prevention. Non-surgical treatment might consist of administration of oxytetracycline to induce tendon laxity or corrective farriery by applying toe extensions, increasing tension on the flexor tendons. Another option is limb splinting or casting, which was used in this foal’s case. In severe cases, surgical intervention with transection of accessory ligaments or flexor tendons might be required. A carpal valgus represents a deviation of the joint medially to the long axis of the bone in the frontal plane. A slight carpal valgus should be considered normal and will often resolve spontaneously with growth, while more severe cases might require surgical intervention. The approach to treatment of angular limb deformities is changing. Formerly, early treatment was the aim, while now a more conservative approach has gained popularity. In severe cases, such as with this foal’s deviations, early treatment is proposed. Treatment techniques include growth acceleration, temporarily unilateral growth retardation, and even a combination thereof. Several surgical techniques are described. To correct this foal’s carpal valgus, a transection and elevation of the periost was performed to induce growth acceleration laterally.

Key Words: Foal – contractural deformity – valgus – physis – growth manipulation

SAMENVATTING

In deze casuïstiek wordt een geval beschreven van een veulen, van twee weken oud, dat aangeboden werd in de kliniek voor heelkunde en anesthesie van de grote huisdieren op de faculteit diergeneeskunde, in Merelbeke. Het veulen had een valgus deformatie ter hoogte van de linker en rechter carpus. Deze deformatie was het meest uitgesproken ter hoogte van het linker voorbeen. Ter hoogte van de deze carpus was ook retractie van de buigpezen aanwezig. De eigenaar vermeldde dat de retractie van de buigpezen aangeboren was en verbeterd was ten opzichte van de geboorte. De valgus deformatie van de linker carpus was wel erger geworden.

Aan de hand van een literatuurstudie wordt een overzicht gegeven van de etiopathogenese, diagnose en de verschillende niet-chirurgische en chirurgische behandelingsmogelijkheden waaruit gekozen kan worden.

Deformiteiten van de ledematen van veulens maken deel uit van het “developmental orthopaedic disease complex”. De oorzaken en pathogenese van deze deformaties zijn complex en het klinisch beeld is variabel. Gemeenschappelijk voor deze aandoeningen is de associatie met de groei. De meeste veulens worden geboren met een lichte valgus deformatie van de voorbenen. Dit is een normale variatie in de conformatie van pasgeboren veulens. Valgus deformatie is een angulaire deformatie. Hierbij buigt de carpus in mediale richting ten opzichte van de loodrechte as. Het tegenovergestelde is varus deformatie, hierbij buigt de carpus in laterale richting. Een lichte carpale valgus deformatie is normaal en corrigeert meestal zichzelf, net zoals de exorotatie die hier meestal mee gepaard gaat verdwijnt als de borst van het veulen breder wordt tijdens de groei.

Angulaire deformaties worden vaak veroorzaakt door peri-articulaire laxiteit. Deze laxiteit verbetert als het veulen sterker wordt en de benen meer gaat belasten. Daarom is lichte beweging belangrijk in het herstel van de deformaties. Echter te veel beweging wordt afgeraden in gevallen van onvolledige ossificatie van de carpaalbeenderen. Bij dergelijke veulens kunnen spalken gebruikt worden voor een evenwichtige belasting van deze cuboïdale beenderen en om collaps te vermijden.

Een andere vaak voorkomende oorzaak van angulaire defromaties is de oneven groei ter hoogte van de distale groeiplaat van de radius. In erge gevallen is meestal chirurgie nodig. Verschillende technieken zijn beschreven. Voor een succesvolle correctie van angulaire deformaties moet nog groei mogelijk zijn. Hierbij is kennis over de groei en het tijdstip van sluiten van de verschillende groeiplaten heel belangrijk. Zo kan men evalueren, of afwachten mogelijk is, of snelle behandeling vereist is en of behandeling zinvol is. De meest gebruikte chirurgische behandeling van oneven groei ter hoogte van de groeiplaten is periostale stripping. Dit is een techniek om de groei te versnellen aan de zijde die te langzaam groeit. Het is ook mogelijk om de groei te remmen aan de zijde die te snel groeit. Hiervoor kan men gebruik maken van een transfysale schroef, schroeven en cerclagedraad of stiften die de groeiplaat overbruggen

Retracties en laxiteit van de buigpezen zijn afwijkingen in het sagitale vlak. Congenitale retracties komen het meest voor. Ondanks dat ze veel voorkomen, worden ze niet als normaal gezien. De meeste gevallen van congenitale retractie zijn lichte retracties en worden spontaan gecorrigeerd door het bewegen.

De conservatieve behandeling van retracties is gebaseerd op rust in combinatie met gecontroleerde beweging, een correctie van een foutieve hoefconformatie en medicamenteuze ondersteuning door middel van NSAIDs en/of oxytetracycline. Het is tevens mogelijk om een chirurgische ingreep uit te voeren. Men kan een desmotomie van de accessoire ligamenten of tenotomie van de buigpezen uitvoeren. De keuze tussen beide is afhankelijk van de ernst van de aandoening. Chirurgische interventie wordt het meest uitgevoerd bij niet aangeboren retracties.

Tijdens de behandeling van deze aandoeningen moet men rekening houden met de mogelijkheid dat veel retracties en angulaire deformaties spontaan verbeteren na de geboorte. Ook kunnen deze aandoeningen vaak succesvol behandeld worden zonder chirurgie.

De diagnose van deze aandoeningen berust op de bevindingen van het klinisch en radiografisch onderzoek. In dit geval werd gekozen om de valgus deformatie van het linker voorbeen chirurgisch te behandelen met een periostale stripping ter hoogte van de laterale distale radius. Vervolgens werd het voorbeen voor korte tijd in het gips gezet om retractie van de buigpezen te behandelen. De nabehandeling bestond uit een correctie van de stand door het bekappen van de hoeven.

De prognose van deze aandoeningen is sterk afhankelijk van de leeftijd van het dier, de ernst van de afwijkingen en de behandeling die wordt ingesteld.

INTRODUCTION

The purpose of this paper is to present a case of a foal that was admitted at the faculty of Veterinary Medicine of Ghent University with a combined angular and flexural deformity, followed by a review of the literature about the etiology, diagnosis and treatment of this condition. The emphasis will be on the non- surgical and surgical strategies applied in the management of angular limb deformities (ALDs).

Most foals are born with some degree of angular deformity, and should to a certain extent be considered normal. Newborn foals can be affected by many congenital and acquired conditions that influence normal limb confirmation and function. Of all congenital deformities, musculoskeletal abnormalities are the most common. These deformities may, but do not always cause lameness. Sometimes, lameness may not become evident until the foal matures and begins training. Deformities may also be acquired, in a response to an event that occurs shortly after birth (Auer, 2006). Equine practitioners are commonly involved in the evaluation and treatment of conformational deviations in foals (Auer, 2006). Attention to limb conformation is important as it is commonly used as an indicator of future performance and orthopaedic health (Santschi et al., 2006). In advanced cases, angular limb deformities may become permanent if not corrected early. Further, ALDs have been reported as one of the primary reasons for euthanasia in foals over two weeks of age (Morley and Towsend, 1997).

To be able to consider what is abnormal, knowledge about variations within the range of normal conformation is crucial. Further, the reason and severity of the deformity, the age of the foal and growth potential should be taken into consideration in the decision of whether treatment is needed, and which treatment to implement (Martens et al., 2008).

Most limb deformities are part of the developmental orthophaedic disease complex (Robert et al., 2013). The causes and mechanisms behind these deformities are complex and do vary between individual cases; however, they are all associated with growth (Jeffcott, 2004). The most frequent deformities in foals are flexural limb deformities (FLDs) and angular limb deformities (ALDs) (Auer, 2006). Restriction in a flexed position or inability to extend is termed a flexural limb deformity. Next to restriction, also digital hyperextensions is an FLD, both resulting in a deformity in the sagittal plane (Adams and Santschi, 2000). The foal in the presented case had a mild contractural deformity, most prominent at the left carpus. Flexural deformities are classified as either congenital or acquired depending on the time of first appearance. Most commonly they are present at birth or develop in the first two years of life, but theoretically, they may be acquired at any age (Greet, 2000). The more common areas of involvement include the distal interphalangeal, fetlock, and carpal joint areas.

Angular deformities give deviations in the frontal plane. A deviation of a joint lateral to the long axis of the limb is called varus, and medial to the axis is called valgus. Newborn foals often have a slight carpal valgus which will normally correct spontaneously. Foals with a valgus deformity often have an exorotation of the front limbs. During growth the chest expands, which will result in rotation of the limbs, giving a normal conformed horse if the initial situation was not severe. Laxity of the periarticular tissues is quite common in newborn foals, and is one of the reasons for deviations from the straight axis. Fortunately, this condition will usually disappear quickly as the foal becomes stronger (Greet, 2000; Auer, 2006). ALDs are most commonly caused by differential growth at the physis, which may correct spontaneously or, in advanced cases, may require surgical treatment aiming at growth manipulation (Greet, 2000). Another cause of carpal valgus is lateral collapse of cuboidal bones. This can occur when foals are born immature, where incomplete ossified cuboidal bones are prone to deformation under mechanical pressure (Getman,

2011). Angular deformities are most seen bilaterally but can also be unilateral. Common deviations are valgus of the carpus, valgus of the tarsus, and varus of the fetlock

Many ALDs and FLDs can resolve spontaneously, or may be treated successfully without surgery. Nevertheless, sometimes surgical intervention is required. Surgical techniques used for the management of angular limb deformities are well established. It is the question when to use these techniques that is challenging and controversial, keeping in mind that foals should be expected to be born with some deformities that will correct with time. Diligent observation is needed to ensure that the deviation resolves as the foal grows and matures. Surgical intervention should be directed at those horses that fail to correct the deformity in a timely manner when there is still growth potential across the physis. The best prognosis follows mild cases which can resolve spontaneously, or in more severe cases where early treatment is possible.

1. CASE HISTORY

1.1. ANAMNESIS

A two weeks old foal was presented at the Department of Surgery and Anaesthesiology at the faculty of Veterinary Medicine of Ghent University on 16/07/2014. The owner reported that the foal was born with a bilateral contraction of the flexor tendons, most prominent at the level of the carpus. With movement, the retraction had decreased gradually after birth, but the left front leg was still retracted. Further, the foal was born with a mild bilateral carpal valgus. The owner decided to bring the foal to the clinic as valgus of the left carpus had become more severe during the preceding week. No treatment was performed prior to arrival at the clinic. The future perspectives for the foal was to be adopted, and the budget for treatment was limited. There were no intentions for a future athletic career, and the only goal was to give the foal a good life. Ability to perform light recreational work was considered a bonus.

1.2. CLINICAL EXAMINATION

A general clinical examination was performed on arrival at the clinic. No abnormalities were found in heart rate, respiration rate, mucosae or body temperature of the foal. On visual inspection a bilateral valgus deformation in combination with a mild retraction of the flexor tendons was seen on both legs. Both deformations were more severe on the left front limb. The left front carpus could not be fully stretched manually. An evaluation at walk showed his gait was fairly normal with no lameness.

1.3. MEDICAL IMAGING

At admittance, a radiographic examination was performed to evaluate the severity of the angular deformities more closely. Figure 1 shows a dorso-palmar view of the carpus of the front legs which confirms a medial angular deviation. The deviation between the axis of the radius and the third metacarpal bone (MCIII) of the left front (LF) carpus was 19,6°, while right front (RF) was 12°. The styloid process was present, but the carpal bones had a mildly rounded appearance. The skeletal ossification index of the carpal bones were evaluated to grade 3(1-4), which is a normal degree for a foal of this age.

Figure 1: Dorso-palmar view of both carpi. Left: Left front limb. Right: Right fron t limb. (Source: Dept. of Medical Imaging, Ghent University, 2014)

1.4. DIAGNOSIS

Bilateral valgus and contractural deformity of the carpus which is more prominent on the left front than on the right front limb.

1.5. TREATMENT

As the budget for treatment was quite limited, it was decided to start with surgical treatment of the most severely affected limb (LF) for its valgus deformity, and a tube cast to treat the contractural deformity. The less severely affected limb (RF) would initially be treated conservatively. An evaluation would be made of the evolution as there was still time to eventually intervene should the condition worsen.

1.5.1. Surgical treatment

To treat the LF carpal valgus it was decided to perform a periostal stripping and elevation at the level of the lateral aspect of the distal radius. The surgery was performed on 17/07/2014.

The foal was sedated and put under general anesthesia. The skin was incised on the lateral aspect of the distal radius between the common- and lateral digital flexor tendon, being the concave side of the deformity. A vertical incision was made in the periost, from the level of the distal growth plate of the radius on the lateral side. Then a cranial and caudal incision was made starting from the most distal point of the vertical incision. Hereby an inverted “T” was created in the periost, just proximally of the distal growth plate. The rudimentary ulna was also cut and the periost was elevated. The incision was closed with resorbable sutures. A tube cast was placed from proximal to the fetlock, ending just below the elbow.

1.5.2. Aftercare

During 13 days following surgery an NSAID, carprofen (Rimadyl®), was administered as anti- inflammatory treatment. Cefquinome (Cobactan®), was given as antimicrobial therapy for seven days. As the foal had loose feces after surgery, Enterol® and Lactase was administered for 13 days. Enterol contains yeast, Saccharomyces boulardi, and is antidiarrhoetic. Lactase is an enzyme to help break down lactose in milk.

Before the foal left the clinic after one week, the tube cast was removed. At this point the contractional deformity of the LF carpus was already significantly improved. The farrier at the clinic adjusted the hooves to help correct the ALD. Hereby, the lateral aspect of the hooves were slightly reduced.

After returning to the owner, the foal was kept in a large stall, and could be let out in a small paddock for an hour a day during the first month, if it remained calm. One month after surgery the owner gradually increased the time the foal was let outside, and after two months the aim was to give it as much movement as possible. Then the foal was kept outside all day, and was only stabled during the night. A farrier came every three weeks to follow up the adjustment of the feet.

1.6. FOLLOW-UP

After three weeks the contraction was fully normalized on both legs. A new radiographic examination was performed on 01/09/2014 to evaluate the foal’s valgus deformity post operation. A dorso-palmar image

of both front legs was made (see figure 2). The deviation between the axis of the radius and MCIII of the LF carpus was now 7,9 °, while RF was 9,68°. The deviation of the left carpus had decreased by 11,7° after the operation. At the right carpus the deviation had spontaneously decreased by 2,3 °. The skeletal ossification index of the carpal bones was now 4.

Figure 2: Dorso-palmar view of both carpi after surgery. Left: Left front limb. Right: Right front limb. (Source: Dept. of Medical Imaging, Ghent University, 2014)

Three and a half months after surgery, on 30/10/2014 the foal came back to the clinic for a control. As seen in figure 3, the angular deformity of the LF limb had almost normalized completely. The angle of the RF deformity was also reduced, though the deviation seen on the radiographical images was greater than the clinical appearance.

Figure 3: A dorso-palmar image of the LF carpus, three and a half months after surgery. (Source: Dept. of Medical Imaging, Ghent University, 2014)

2. LITERATURE REVIEW

This literature review will discuss limb deformities with emphasis on valgus- and flexural deformities of the carpus.

2.1. THE GROWING FOAL

During the fetal period, the skeleton is formed on a scaffolding of cartilage. During growth of the fetus, this growth cartilage proliferates and progressively transforms into bone during a process called endochondral ossification. Growth continues in the various growth centers of the different bones until skeletal maturity is reached at the age of around four to five years. Anderson et al. (2004) found that longitudinal bone growth of the distal limb is presumably completed before one year of age. Further, growth increased by only five to seven percent, from weanling to the age of three years. In long bones, some growth occurs at the level of the epiphysis, growing toward the articular cartilage and epiphysis. The metaphyseal region contributes the most to the growth (Auer, 1998). In contrast to long bones, cuboidal bones do not have growing physes and epiphyses, and progressively ossify from their center to the surface (Floyd, 2007).

Physeal growth is regulated through signaling molecules between the growth zones and surrounding periosteum or perichondrium. Among others, parathyroid hormone related protein (PTHrP), the PTHrP receptor (PTHrPR), and Indian hedgehog (IHH) are important signaling molecules in this process (Vortkamp, 2001). The approximate time during which new bone is formed at the different regions differs, but closing time of the different long bones occur at predictable time points (Auer and Von Rechenberg, 2006). This is very important in the evaluation of treatment of ALDs, and will be further discussed in chapter 2.2.2.2.

According to Robert et al. (2013) more than half of the foals have a degree of angular limb deformities in their first month of life. Carpal valgus is considered as a normal conformation for young foals, and the legs will straighten gradually on their own (McIlwraith, 2004). Normally, angular deviations and other abnormalities such as tendon and ligament laxity will have improved within four weeks of age (Curtis and Stoneham, 1999). According to Greet (2000), a slight carpal valgus of approximately two to five degrees should be considered normal, and will straighten as the foal grows and its chest expands. A certain degree of carpal valgus has even been proved to exhibit a protective mechanism in Thoroughbreds, with decreasing odds for carpal fracture and effusion (Anderson and McIlwraith, 2004). Studies of normal conformational changes with age (Anderson et al., 2004) give valuable information in the decision whether conformational “abnormalities” have to be considered “normal” or not.

2.2. DEVELOPMENTAL ORTHOPEDIC PROBLEMS OF THE FOAL

The term developmental orthopedic disease (DOD) encompasses all orthopedic problems affecting the growing foal. Acquired angular- and flexural deformities (ALDs and FLDs), physitis, osteochondrosis, osteochondrosis dissecans (OCD), wobbler syndrome (Pagan and Jackson, 1996) and cuboidal bone abnormalities (McIlwraih, 2004) are all diseases brought under the term DOD. These diseases can develop as a single problem, or together, mainly in fast-growing, heavy animals (Sirin and Alkan, 2010). How closely the various forms of DOD may be related is still to be determined (McIlwraith, 2004). According to Getman (2011) the three types of limb deformities; angular, rotational and flexural, are often seen in combination in more severe cases.

2.2.1. Factors contributing to DOD

A multifactorial and complex etiology is common for developmental orthopaedic diseases. Genetic predisposition, trauma, nutrition-, vitamin-, and mineral imbalances, as well as endocrine factors have been proposed, though the exact cause is not known (Sirin and Alkan, 2010).

Lack of space in the uterus has been proposed as one of the primary causes of congenital angular- and flexural deformities. As the size and capacity of the uterus would influence the size of the fetus, lack of space in the uterus may rather be a contribution factor than the major cause of these problems (Floyd, 2007).

After birth, nutrition may play a role as a risk factor in development of orthopedic disease. Excessive energy- or carbohydrate intake may give mineral deficits, excesses or imbalances (Harris et al., 1999). Horses with fast growth or sudden weight gain may be prone to DOD (Sirin and Alkan, 2010). A study conducted by Pagan and Jackson (1996) in Kentucky indicated a faster growth rate in foals operated for OCD compared to normal foals. Besides OCD, overfeeding and rapid growth rate in foals may contribute to ALDs and FLDs (Auer and Martens, 1980). Further, growth rate and predisposition is influenced by genetic factors. Nevertheless, the association of growth rate and body size with DOD is controversial among researchers. Mechanisms are complex and their clinical appearance differs greatly. However, a common factor is the association with growth (Jeffcott, 2004).

2.2.2. Angular limb deformities

A deviation of the extremity from the vertical plane in axial direction is called an angular deformity (Sirin and Alkan, 2010). The distal part of the limb may deviate laterally, called a valgus deformity, or medially called a varus deformity. Valgus of the carpus is the most common deformity, but it can also affect the fetlock or tarsal joint (Douglas, 2003).

2.2.2.1. Etiopathogenesis

Next to the factors contributing to DOD generally, congenital angular limb deformities may more specifically be a result of asymmetrical growth of long bones, peri-articular laxity and incomplete ossification of cuboidal bones of the carpus and tarsus. Joint laxity predisposes to abnormal weight bearing and increased risk of crush injury of cuboidal bones (Lester, 2005). Further, cuboidal bone abnormalities such as wedging may give angular deformities, most commonly seen in pre- or dysmature foals. These bones first ossify in a circle and later form a bony cube. As this process is not finished in an early born foal, deformation of these bones can develop (McIlwraith, 2004). As the duration of the gestational period in mares is variable, the term immaturity is not clearly defined. A study conducted by Rossdale and Short (1967), found that 95% of Thoroughbred mares foaled between 327 and 357 days of gestation. Hintz et al. (1979) found a normal range of 305 to 365 days, also in Thoroughbred mares. Birth before 320 days of gestation is the most common definition of prematurity (Rossdale, 1993). Dysmaturity is a term used to describe foals that experienced intrauterine growth retardation, typically showing some signs of immaturity at birth, despite a gestational length within the “normal” range (Lester, 2005).

Severity of incomplete ossification may be evaluated by radiographic examination. A gradation from grade 1, where some cuboidal bones are present, but with no ossification, to grade 4 where the cuboidal bones are shaped like adults, may be applied (McAuliffe, 2014). Prenatal asymmetrical growth of long bones

can cause a deviation of the adjacent joint. According to Greet (2000), the most common type of deformity is related to differential growth at the level of the physes.

Figure 4: Grade of incomplete ossification. Left: Grade 1: Tarsus. Some cuboidal bones present, no ossification. Middle: Grade 2. Carpus. All cuboidal bones present, all with some ossification. Right: Grade 3. Carpus. Cuboidal bones are small and round, wide appearance of joint spaces. (Source: McAuliffe, 2014)

Acquired angular limb deformities become apparent within weeks or months after birth. Assymmentrical growth at the physes is not always congenital, but can also be caused after birth. Postnatal factors affecting growth of the physeal region include poor confirmation, unbalanced and overnutrition, trauma, excessive exercise and hematogenous osteomyelitis (Auer and Martens, 1980). Metabolic abnormalities or trauma may cause abnormal ossification of the epiphysis, resulting in a tilted joint surface (Floyd, 2007). A summary of contributional factors to angular limb deformity is given in figure 5.

Figure 5: Contributional factors to postnatal development of angular limb deformities. Source: Ballard (1986)

2.2.2.2. Treatment

The key to management of ALDs is to decide whether immediate management is necessary or if a wait- and-see approach is tolerated. To decide which treatment to implement in the therapeutic plan depends on type of deformation, the cause, location and severity, as well as the age of the foal (Bramlage and Auer, 2006; Getman, 2011).

The terms mild, moderate, and severe angular deformities can be used to describe deformities of respectively less than 10°, 10° to 20°, and greater than 20° (Gaughan, 1998). According to Auer and Von Rechenberg (2006) and Roberts et al. (2009), deformities of greater than 12° are considered severe, and early treatment is proposed. Conservative management is indicated in mild cases, and as an immediate option before surgical intervention in more severe cases (Greet, 2000).

Conservative treatment

In most foals born with mild to moderate ALDs, spontaneous straightening of the limbs occur within the first two to four weeks of life (Auer et al., 1982). Bramlage and Auer (2006) report that correction of carpal valgus within five to seven degrees should occur by approximately four months of age. It is equally important to know when to abstain from intervention, in situations where spontaneous correction is likely to occur, as when to implement treatment of foals which may not be able to correct the deformity spontaneously (Bramlage and Auer, 2006). The following figure shows a foal with carpal valgus that improved over eight weeks without treatment.

Figure 6: Spontaneous improvement of carpal valgus. Image A shows the foal at one week, B at six weeks and C at nine weeks of age. (Source: Morrison, 2015)

The most common cause of mild ALDs in newborn foals is peri-articular laxity. In these cases, light exercise such as 10 – 20 minutes walk daily is recommended (Auer, 2006). Another option is placing the mare and foal in a small paddock or large stable (Baker et al., 2010). Swimming may be a part of the therapeutic plan, as an excellent option for controlled physiotherapy in foals with laxity of the peri-articular supporting structures and a normal degree of ossification. Hereby, no weight is put on the limbs and the paddling is carried out against the resistance of water (Fackelman, 1984). Fackelman (1984) suggests

that the resultant increase in muscle tone causes rapid improvement of the condition. A wait-and-see approach can be considered in cases of mild ALDs caused by disproportionate growth at the physes if radiology shows adequate ossification. In these cases stall rest for four to six weeks is recommended, and surgery if correction is not achieved (Auer, 2006). Waiting too long for results is no option, as most surgical procedures require growth potential at the growth plate to be effective (Auer, 2006). Farriery can help in mild cases or initially in any case. With valgus deformities the medial aspect of the hoof is subjected to excessive wear by the abnormal stance. Hereby, trimming the lateral side of the hoof is an option to give an even confirmation of the sole. Application of a shoe with an extension in medial direction might also be helpful in prevention of uneven weight bearing (Greet, 2000).

Management of foals with incomplete skeletal ossification is controversial. To minimize the risk of collapse of immature cuboidal bones, stabilization to facilitate even axial load and restriction of exercise is recommended (Getman, 2011). Nevertheless, forced recumbency may predispose pulmonary disease, and is not indicated. Further, a certain amount of weight load is necessary to encourage ossification. Rigid external limb support such as splints or casts can be used to maintain good alignment, yet allow some weight bearing to facilitate ossification. Hereby, the cast or splint has to end at the fetlock, as incorporation of the foot may cause laxity of the musculotendinous structures of the foot (Auer, 1991).

Surgical treatment

Distinguishing normal variation from severe deformities that do not correct spontaneously or with non- surgical techniques, is the key to decide whether surgical intervention is indicated or not (Auer, 2006). Also foals that were thought to, but fail to correct the deformity by growth should have surgery when there is still growth potential across the physis (Baker et al., 2010).

Deformities caused by differential growth at the level of the physis may respond to surgical intervention in the form of growth plate manipulation through acceleration or temporarily growth retardation (Greet, 2000). Deciding between the two principles is primarily a function of the amount of correction necessary and the amount of growth left in the physis involved (Bramlage and Auer, 2006). As closing times of physes of long bones are predictable, location and age should be taken into consideration when evaluating treatment options. Table 1 shows the correlation between rapid growth, time of closure, and age limits of interventional techniques for some physes. The highest growth rate is between birth and ten weeks of age. When most other growth plates have closed, distal radial epiphyseal closure happens later, at average 24.7 months (Fretz et al., 1984), indicating that surgical intervention is possible during a longer time span. In contrast, the physes of the metacarpophalangeal (MCP) and metatarsophalangeal (MTP) regions closes early, at approximately three months of age. Hereby, Auer and Von Rechenberg (2006) indicate that foals suffering from varus deformities of this region should be treated before one month of age.

Table 1: Period of rapid growth, age at radiographic closure, and age limit recommendations for correcting angular limb deformities for some growth plates in horses.

Growth Plate Period of Rapid Growth Age at Radiographic Technique and Age Limit Physeal Closure

Distal radial 0-8 months 22-36 months HCPTE: 4 months TBP: 12 months

Distal tibial 0-6 months 17-24 months HCPTE: 4 months TBP: 10 months

Distal MC/MT 0-100 days 6-15 months HCPTE: 2 months TBP: 3 months

HCPTE = Hemicircumferential periosteal transection and elevation, TPB = transphyseal bridging, MC = Metacarpal. MT = Metatarsal. (Adapted from: Fretz et al., 1984)

A procedure to correct angular deformities through inducing growth acceleration that has gained worldwide acceptance, is periosteal transection and elevation. This method is based on “stripping” on the concave side of the deformed limb, being the lateral side in an animal with a valgus deformity. This procedure can already be performed at two weeks of age. In theory, early intervention should give faster correction. Still, surgery on a case that would have corrected spontaneously must be avoided. In most cases, the decision is made around four months of age. In more severe cases, it may be obvious at an earlier point that intervention is needed (Auer, 2006).

For the treatment of carpal valgus, a vertical skin incision is made between the common- and lateral digital extensor tendons, parallel to the long axis of the bone (Auer and Martens, 1982). From a point 4- 5 cm proximal to the distal physis of the radius, the incision is made approximately 3 cm in proximal direction (see figure 7), and down to the periosteum (Auer and Von Rechenberg, 2006). The next step is to make a vertical hemicircumferential incision in the periosteum, extending 3 cm cranially and caudally from the skin incision (Ballard, 1986). To be able to only involve the periosteum in this vertical incision, a curved haemostatic forceps is used to separate subcutaneous tissues and tendons from the underlying tissues. The forceps is brought into the distal point of the vertical skin incision between the extensor tendons, parallel to the physis in cranial direction. Pressing onto the bone, the tips of the forceps are abducted. Now a curved scalpel blade can be inserted between the tips of the forceps for protection and pulled back in direction of the skin incision. The procedure is repeated from the distal tip of the vertical incision, this time in caudal direction, creating the vertical part of the inverted “T” (Auer, 2006). The periosteum in the foal is very thick and highly vasculated, usually producing some hemorrhage when incised (Greet, 2000). The next step is to transect the rudimentary ulna, under the protection of the forceps. In about 20% of all cases the rudimentary ulna is ossified and must be removed with rongeurs (Bertone et al., 1985). Starting at the horizontal incision, the periosteum is then incised in a proximal direction parallel to the vertical skin incision, over a length of 2 cm. Hereby the hemicircumferential periosteal transection is performed. This can be performed with or without elevation of the two triangular flaps. To elevate these, a periosteal elevator is brought underneath the periosteum, elevated and gently laid back onto the bone to prevent the tips from curling (Greet, 2000).

Figure 7: A: Overview of locations of the landmarks for surgical intervention in cases of carpal valgus. Cranial: common digital extensor tendon. Lateral: Lateral digital extensor tendon. Caudal: Rudimentary ulna (not shown). B: Completed periosteal transection at the distal radius. (Source: Auer and von Rechenberg, 2006)

For closure, a simple continuous suture pattern with 2-0 absorbable material is used for the subcutaneous tissue and intradermally. This procedure gives an acceptable cosmetic appearance. A non-adherent dressing may be applied on the surgical site followed by an adhesive elastic bandage (Auer and Von Rechenberg, 2006). Postoperatively, exercise should be restricted until the ALD is corrected. Hereby, the foal should be kept in a stall for at least two to three weeks, allowing minimal exercise. Every two weeks the feet should be rasped slightly on the outside (for valgus), which contributes to straightening of the limb and a correction of outward rotation (Auer and Von Rechenberg, 2006).

The principle behind periosteal transection may be release of tension in the periosteum, stimulating the physis to grow more rapidly on the concave side of the bone. According to this theory, the tension across the growth plate is mechanically released by making the hemicircumferential periosteal transection with or without elevation on the concave side (Warrell and Taylor, 1979). More recent work has suggested that this increase of growth is mediated by signaling molecules. It is suggested to be a disruption of the negative feedback loop between Indian hedgehog and parathyroid hormone-related protein, caused by the transection of periosteum or perichondrium, hereby stimulating growth (Auer and Von Rechenberg, 2006). This effect may also be achieved by less invasive alternatives (Bramlage, 2009). Bramlage (2009) reports that a less traumatic approach to periosteal manipulation leads to good correction as well. A study conducted by Auer et al. (2011) revealed that multiple insertions of a hypodermic needle into the physis at the concave side leads to correction of the deformities, similarly to HCPTE. The advantage is obviously the less invasive approach and hereby a better cosmetic outcome. Nevertheless, the effect of these techniques are controversial among researchers. According to Greet (2000), another disadvantage with HCPTE is that the degree of correction is less dramatic than that following transphyseal bridging. Hereby, in severe cases or when there is not much time left until functional physeal closure, it may be preferable to perform transphyseal bridging alone or in combination with HCPTE (Greet, 2000).

Different techniques are described for growth retardation, and all except one use the same principles. Implants are applied at the convex side, bridging the physis temporarily, allowing the shorter side to grow (Auer and Von Rechenberg, 2006). Growth retardation can be performed either in young foals (less than three months of age) with severe ALDs or in foals with significant ALDs after the rapid growth phase, for example after six months for the radius (Fretz et al., 1984).

Stapling was probably the first technique described of growth retardation in the foal, but is no longer commonly used. One or more staples are placed across the physis to prevent growth. Commercial staples are available, but Steinmann pins can also be bent into the right shape. After making a longitudinal vertical incision on the convex side, a staple of appropriate length is chosen (Smith, 2010). The legs of the staples are placed equidistant from the physis into the meta- and epiphysis (Heinze, 1969; Smith, 2010). More than one staple can be applied, depending on severity. An intraoperative radiograph may be helpful to ensure accurate placement. By overbridging the physis, this procedure will retard growth on the side to which it is applied. Formerly staples were commonly used, but have been replaced by other techniques also bridging the physis. To prevent overcorrection, the staples need to be removed (Smith, 2010).

Screws and cerclage wires (see figure 8) are now the most frequently applied implants to achieve growth retardation and “catch up” growth of the contralateral side of the bone (Fackelman et al., 1975; Turner and Fretz, 1977; Auer and Martens, 1980). Two stab incisions are made, and a 4.5 mm cortex screw is inserted in the center of the epiphysis and one proximal to the physis. Using a haemostatic forceps, the soft tissue between the incisions is elevated. Through the proximal incision, a wire loop is brought in and turned around the distal screw. The two wire ends are tightened together over the most proximal screw. After applying the wire loop, the screws can be tightened completely, increasing the tension on the wire additionally. It is important to tighten until heads of screws are flush with soft tissues. Excessive tightening of the screws may dislodge the wires over the screw heads (Howard, 2006). A second wire can be applied for extra strength and reducing the risk of wire failure. The two small stab incisions are closed with two simple interrupted skin sutures. The surgical site is protected with a light bandage for 10 days (Auer, 2006).

Figure 8: Growth retardation procedure with screws and cerclage wire. A: Stab incisions to the bone. B: Elevation of soft tissue between the two incisions. C: Implantation of screws through each incision without tightening. D: Introduction of wire loop through the proximal incision, tightened in figure-eight around distal screw and tightened at the proximal screw. E: Complete insertion of screws. (Source: Auer, 2006)

Alternatively, a curvilinear incision can be made over the lateral aspect of the distal radial physis, oriented along the long axis of the radius, beginning at the level of the radiocarpal joint and extending toward the diaphysis. Insertion of screws and a figure-eight wire is placed similarly to the procedure with stab incisions (Howard, 2006).

Another alternative for transphyseal bridging is appliance of a transphyseal screw (Howard, 2006). Kay et al. (2005) report that this technique successfully corrects ALDs at the distal tibial, radial, and metacarpal physis. Also this procedure is performed to attempt retarding growth on the more active side of physis (Greet, 2000). Howard (2006) reports that a 4,5mm cortical screw can be inserted through a stab incision at the distal radius. As seen in figure 9, the screw is applied in the epiphysis and directed distally through the physis into the metaphysis, in an angle of 30° from the vertical plane. With growth, the bone will move relative to the screw, tightening it across the physis, slowing growth on this side (Smith, 2010). The screw can be removed when desired conformation is reached. The advantage of this procedure is the ease of insertion and improved cosmesis with one single screw. Further, it may be applied after the rapid growth phase is over. Martens et al. (2008) report that this technique is primarily used for retardation of growth at the distal growth plate of the metatarsus and metacarpus, in the correction of fetlock varus deformities.

Figure 9: Dorso-palmar radiograph of the carpus with a single 4,5mm cortical bone screw placed across the distal radial physis. (Source: Howard, 2006)

Next to insertion of screws, a small 2,7mm bone plate of adequate length can be used to correct ALDs in older foals, following the same principles as in the former mentioned procedures of growth retardation. It can be inserted through a stab incision on either side of, or by a slightly curved incision entered over the physis (Auer, 2006).

Acoording to Smith (2010) and Howard (2006), implants should be removed just prior to complete correction, as the limb will have a tendency to continue to correct for a short time after implant removal. Auer (1998) and Roberts et al (2009) indicate that removal should be performed when the deformity is corrected or when growth has ceased due to physeal closure . Close monitoring is important and removing the implant may be crucial to avoid overcorrection resulting in deformity of the opposite type (Greet,

2000). In contrast, i t has been suggested that a small degree of overcorrection might be indicated before removal of the implant, as the trauma by removal may cause an enhancement of growth, similar to described with HCPTE (Pille, F., Personal communication, 2015).

Several surgical techniques that aim to locally accelerate or retard growth plate activity have been described. Radial extracorporal shock wave therapy (ECSWT) is the mentioned supplementary technique for growth retardation beside the other surgical techniques using transphyseal bridging (Bathe et al, 2006). ECSWT is a new non-invasive method, and the use hereof has been suggested as an alternative to the mentioned surgical techniques (Bathe et al., 2006). As described by Smith (2010), it may be used in foals over two weeks old, and can be performed on a standing or recumbent sedated foal. The shockwave probe is applied on the side where growth retardation is desired, being the convex side of affected physis. The instrument is adjusted to 1500-2000 cycles at 15 Hz, set at 2,5 - 3 bars. The treatment is typically repeated every two weeks until clinical assessment reveals correction. It is generally well tolerated and no lameness should be seen following treatment. Bussy et al. (2013) performed a retrospective study of 64 cases to report the use and assess the effects of ECSWT for the treatment of carpal joint valgus deformities (CJVD) in young foals. Only foals with deformities greater than 5 degrees were included in their study, and were divided into three groups based on their degree of CJVD. Next to ECSWT, each group received specific exercise, hoof trimming and hoof extensions. They found that ECSWT could be applied successfully in different degrees of severity and should be considered effective for the treatment of CJVD. They report that it is likely that some foals presented in their study with mild deformities would probably have improved without ECSWT. However, their impression was that treatment of those mild deformities with hoof trimming or shoe extensions might need greater time for ALD resolution, and the degree of correction less significant than obtained in foals treated with ECSWT additionally. Also foals with severe carpal deformities corrected using this technique in combination with corrective farriery. Nevertheless, they report that future studies with negative and positive (surgical) control groups are needed. Further, all foals in this study were treated during the rapid growth phase, and the authors report that this technique is likely less effective in older foals. The overall positive effect of this new technique was also reported by Bathe and Hilton (2008). They found that 85 percent had successful outcomes following this procedure.

In severe cases, a combination of growth acceleration and retardation may give faster and more complete results (Auer, 2006). Time is a limiting factor, and once the physis is closed, correction of ALDs through growth modulation is not possible. Then the only option is corrective osteotomy/ostectomy (Auer and Von Rechenberg, 2006). Arthrodesis of the intercarpal joint can be used as a salvage procedure in severe cases of ALDs. Following this procedure the horse may be used for non-performance purposes (Auer et al., 1982).

2.2.3. Contractural deformities

Flexural limb deformities represent deviations in the sagittal plane. Hyperflexion or hyperextension might be seen, and can be congenital or acquired (Auer, 2006). A hyperflexion that cannot be manually straightened is often called contracted tendons, even though the problem is not shortening of tendons, but short tendons relative to the associated osseous structures. One or several areas might be affected by the contractural deformity. Hyperextension is caused by laxity or rupture of flexor tendons (Schneider, 1989). Due to the scope of this paper, only contractural deformities will be discussed.

2.2.3.1. Etiopathogenesis

Next to the factors contributing to DOD generally (see subchapter 2.2.1), congenital flexural limb deformities may be a result of diseases acquired by the mare during pregnancy. A wide range of causes and agents have been mentioned in association with this problem. Possible factors are: ingestion of locoweed and Sudan grass during pregnancy, gene mutations in the sire, goiter, influenza outbreaks, disorders of the neuromuscular system, and elastin and collagen cross-link defects caused by lathyrism. Some causes are said to be speculative with lack of evidence, though a multifactorial origin is likely (Auer, 2006). Flexural deformities can also be acquired, as a part of, and in association with other disorders of the DOD complex (Bramlage, 1987). In cases of rapid grow rates, the lengthening of a bone might exceed the elongation potential of the tendon, where the tendon will become relatively too short. Limitation of passive elongation is among others caused by the presence of the accessory ligament of the digital flexor tendons (Fackelman, 1984). Rapid growth as well as any other cause of pain and lameness may lead to contractural deformities as a result of less weight-bearing (Getman, 2011).

2.2.3.2. Treatment

The age of the foal, location, severity and existence of other bony abnormalities should be taken into consideration when a decision is made whether to treat, and which treatment to implement (Getman, 2011).

Non-Surgical treatment

Many congenital flexural limb deformities can be treated successfully without surgery (Adams and Santschi, 2000). Mild flexural deformities of the carpus or fetlock joints resolve spontaneously if the foal is able to stand, nurse and walk on its own (Hunt, 2011). Some mild to moderate cases do not resolve spontaneously, but will often respond to medical management, external coaptation, and farrier work (Auer, 2006) if addressed in time. If not treated promptly, the deformities may progress into more severe cases, and surgery could be the only option left to solve the problem (Getman, 2011). According to Floyd (2007) conservative treatment should be tried before considering surgical intervention in almost all cases.

Physiotherapy with manual extension of the limbs in sessions of 15 minutes every four to six hours can be sufficient to straighten the foal’s limbs. Alternatively, the foal can be forced to stand and ambulate (Hunt, 2011). The foal should perform controlled exercise such as turnout in a small paddock for one hour daily (Adams and Santschi, 2000).

As nutrition and genetics control the growth rate of the foal, balanced nutrition is generally recommended, and particularly important in rapid growing foals (Adams and Santschi, 2000). If concentrates are fed, this can easily be reduced. Nevertheless, heavily lactating mares may also be the reason for excessive energy intake by the foal. A decrease in the mare’s concentrate ration or early weaning of the foal are possible options (Kidd, 2012). Further, the mineral balance of the ration for both the mare and the foal should be balanced, as research has shown that imbalances, particularly in calcium/phosphorus, contribute to developmental diseases (Knight et al., 1985).

Corrective farriery is often used as the first line of treatment. This often involves applying toe extensions and trimming the heels to lower the hoof angle (Adams and Santschi, 2000). Sometimes, the toe is elevated to be able to achieve the desired angle of the foot. These techniques will force the heels to the ground, as well as delaying breakover, forcing stretching and lengthening of the flexor tendons. This is 19

most valuable in cases of FLD of the distal interphalangeal (Adams and Santschi, 2000) and MCP/MTP joints (Metcalf et al., 1982). In newborn foals these toe extensions may be sufficient to prevent knuckling over, allowing them to bear weight (Kidd, 2012). The dorsal hoof/toe extension might be acrylic alone or in combination with a lightweight plate to provide protection against excessive wear next to increasing forces on the flexor tendons. To make these extensions more stable and make them stay on longer, acrylic can be worked into 2 mm drilled holes in the dorsal hoof wall. Also special half-round glue on shoes is commercially available (Kidd, 2012). Nevertheless, Greet (2000) reports that these interventions are not effective in all cases. Though, in mild to moderately affected foals, trimming excessive heel growth (every two weeks) due to abnormal wear by an incorrect stance is helpful (Greet and Curtis, 2003). Shoeing may be successful as sole treatment in mild cases or may reinforce the results of successful surgery. Further, it may help prevent recurrence of the problem (Tarr et al., 1993).

Other methods for physically stretching the limbs, is heavy bandaging, splinting or casting (Bohanon, 1995; Lokai and Meyer, 1985). In cases of unresponsiveness to toe extensions, half-limb casts may be an option (Wagner et al., 1982). Further, if the foal is not able to stand, splinting or casting the limb in extension is necessary to help the foal stretch its legs and be able to put weight on them, which is crucial for stretching the tendons and palmar soft tissues. Support bandages will also protect the dorsal surface of the fetlock, when the foal has difficulties standing (Auer, 2006). Fixed casting of a limb produces tendinous and ligamentous laxity, and is effective for treating FLD of the carpal and fetlock joints, besides some tarsal deformities (Wagner et al., 1982). Some authors prefer splints over casts because applying the splints can be alternated with periods without them. If casts are applied, they must be replaced at least every two weeks (Auer, 2006), ideally every 3-4 days (Greet, 2000) to keep pace with the growth of the foal and prevent the formation of pressure sores (Auer, 2006). FLD of the proximal and distal interphalangeal joint may require casts as they are more difficult to immobilize. Any strong, light material is suitable as splint. Polyvinylchloride pipes can easily be cut longitudinally into thirds or halves, and cut in the length to fit the foal’s limbs. Greet (2000) reports that a series of gradually extending splints should be used to passively and progressively extend the joint. Bandage should be applied on the legs and the ends of the splints should be covered with cotton before positioning. If the contracture is located in the phalangeal or fetlock joints, the feet should be incorporated, and if located in the metacarpophalangeal and carpal region, incorporation of the phalangeal region should be avoided (Kelly et al., 1987). Bandages over the splints will hold them in place. According to Adams and Santschi (2000), the splints can be left on for a maximum of eight hours. After leaving them unsplinted for several hours, they are replaced. This treatment causes relaxation of the muscle-tendon units (Fackelman, 1984). When the joint angles are becoming normal and the foal can stand unassisted, the splints are usually not longer used. Controlled exercise may now correct the deformity completely (Adams and Santschi, 2000).

Next to stretching the limbs, cautious use of non-steroidal anti-inflammatory drugs (NSAIDs) may be beneficial (Hunt, 2011). As passive stretching of (relatively) shortened tendons is a painful situation, administration of analgesics may facilitate weight-bearing and improvement of the contracture (Kidd and Barr, 2002). Further, other causes of pain in the limb can quickly lead to off-loading of the limb and flexor tendon contracture. Hereby, thorough lameness examination and treatment if necessary is essential in prevention and treatment of flexural deformities. Phenylbutazone or flunixine may be administered for analgesia as an important part of the therapeutic plan, mainly in cases of acquired fetlock contracture (Floyd, 2007). As NSAIDs can cause and exacerbate gastric ulcers (Tobin et al., 1986), Kidd and Barr (2002) outline the importance of concurrent treatment with ranitidine or cimetidine as gastric protectant.

In mild cases of congenital flexural deformities, oxytetracycline (OTC) may be given intravenously to relax flexor musculotendon units (Lokay and Meyer, 1985; Madison et al., 1994). The most effective

results are seen in foals that receive OTC therapy in the first few days of life, but may also be useful in older foals (Adams and Santschi, 2000). A dose of 2-3 grams (Wright et al., 1993), or 20-60 mg/kg body weight in 250 to 500 mL saline is slowly given intravenously once a day (Lokai and Meyer, 1985). This dose appears safe for healthy foals, but should be used cautiously in sick foals as the drug is potentially nephrotoxic (Wright et al., 1993). Results from a study conducted by Arnoczky et al. (2004) indicate that OTC inhibits tractional structuring of collagen fibrils by equine myofibroblasts through an MMP-1- mediated mechanism as well as inhibition of collagen gel contraction. Hereby, the ligaments and tendons can become more susceptible to elongation during weight bearing. This treatment is continued until the limbs are in a position where the foal is able to stand without assistance, normally within 24-48 hours, but up to three consecutive days of treatment may be needed. Splints are often used in combination with this medical treatment to stretch the legs and help the foal to stand as described earlier (Fackelman, 1984).

Surgical treatment

Surgical intervention is seldom necessary with congenital flexural deformities, and is used in severe cases or those that do not respond to non-surgical interventions. Further, according to Getman (2011) recurrence of the contracture is not uncommon following some initial improvement with non-surgical techniques, and surgery may be necessary. For congenital FLD, surgery is mainly carried out for carpal contractures. In contrast to congenital FLD, acquired flexural limb deformities do often require surgical intervention in addition to medical treatment (Adams and Santschi, 2000).

Which procedure to choose and when to perform surgery should be determined by the anatomical location involved, severity of the condition, and age of the patient (Floyd, 2007; Hunt, 2011). Floyd (2007) suggests that the best approach is to start with the most conservative surgical procedure, and a more invasive procedure can be considered if the first option does not give desired results. This can be performed during the same surgery if the result is not satisfying. For example, if cutting a check ligament is effective in correcting the flexor contracture, results will be seen immediately during the procedure. If restoring the affected joint to its normal angle is not possible after cutting the ligament, a more invasive procedure is necessary.

For FLDs at the level of the distal interphalangeal joint, desmotomy of the accessory ligament of the deep digital flexor tendon (DDFT) is the most common procedure. If a more invasive approach is needed, tenotomy of the DDFT is an option. Desmotomy of the accessory ligament of the superficial digital flexor tendon (SDFT), a tenotomy of the SDFT, or a combination are possible interventions for resolving metacarpophalangeal FLDs. Whereas surgery combined with aggressive medical therapy is often successful in resolving the deformity, transection of flexor tendons is not recommended if the foal is intended for an athletic future (Adams and Santschi, 2000).

In severe cases of fetlock- or proximal interphalangeal deformities secondary to abnormally formed bones, arthrodesis of the joint is an option, resulting in pasture-sound animals (Whitehair et al., 1992).

For severe cases of carpal FLD where the foal is not able to nurse, palmar carpal joint capsule transection or tenotomy may be indicated (Wagner, 1990). Tenotomy of the muculus flexor ulnaris lateralis and flexor carpi ulnaris is sometimes performed, 2 cm proximal to the accessory carpal bone (Vasey et al., 1995).

DISCUSSION

This paper presented a case of a foal with bilateral valgus at the level of the carpi. The LF Limb was more severely affected than the RF. According to Auer (2006) it is very typical that one limb is more affected than the other. In addition to the ALDs, the foal had a mild FLD; retraction of the flexor tendons, most prominent at the level of the carpus of the LF limb. When the foal was presented, an assessment had to be made whether this condition could resolve spontaneously, and whether it could resolve with conservative treatment. By the severity of this foal’s condition it was obvious that this would not correct without intervention. Additionally, according to the owner the ALDs had become more severe lately, and immediate intervention might hereby be indicated. Which procedure to choose and when to perform surgery should be determined by the anatomical location involved, the cause and severity of the condition, and the age of the patient (Floyd, 2007; Getman, 2011; Hunt, 2011). Also a limited budget was an important factor in the decisions.

Studies of normal conformational changes with age (Anderson et al., 2004) give valuable information in the decision whether conformational “abnormalities” have to be considered “normal” or not. Robert et al. (2013) report that there is extensive information available on variations in conformation in Thoroughbred horses within populations of mature horses and yearlings, and several studies have also evaluated changes in conformation with growth. But very little information is available of evolution of limb deformities in Standardbred trotter and warmblood horses. With more studies of development of limb deformities, a more accurate assessment can be made in the decision of management of these foals.

Preoperative radiographs were taken to confirm the source of the ALDs and determining if the growth plate was indicated for treatment. As this foal was only two weeks old, all growth plates should be active. If the origin is within the joint, bridging can cosmetically straighten the limb and improve the external appearance, though internal misalignment may result in degenerative joint disease and lameness. In this case the origin was within the distal physis of the radius, whereas growth plate manipulation could be indicated. The angles of the foal’s carpi were 19,6° (LF) and 12°(RF). In most foals born with mild to moderate ALDs, spontaneous straightening of the limb occurs within the first two to four weeks of life (Auer et al., 1982). Bramlage and Auer (2006) report that correction of carpal valgus within five to seven degrees of straight should occur by about four months of age. According to Auer and Von Rechenberg (2006) and Roberts et al. (2009), deformities of greater than 12° are considered severe. Gaughan (1998) proposes greater than 20° as severe. With 19,6°, this can be evaluated as a severe case, and immediate intervention was correct according to the literature. Due to the limited budget the less severely affected LF limb was treated conservatively.

The management of ALDs and FLDs is well established, and there are several techniques that can be used to manipulate a foal’s limb confirmation. The animal should be continuously monitored from two weeks of age to ensure that timing of these procedures can be optimized. As the physes close, the window of opportunity to manipulate the limbs’ growth diminishes. All the potential methods and pitfalls should be carefully considered before manipulation. The older a foal is when treated, the more complex and invasive techniques are needed to correct the deviations. Hereby, more conservative treatment may be considered first, but making sure the window of opportunity is not lost is crucial. When surgical intervention is required, Floyd (2007) suggests that the best approach is to start with the most conservative surgical procedure, and a more invasive procedure can be considered if the first option does not give desired results. In this case, it was decided to perform an HCPTE of the LF Limb. The RF limb

would hopefully improve with conservative treatment. This means that in this case we could follow up two different scenarios.

HCPTE is a frequently used technique in correcting angular deformities in foals when there is still growth potential. The effectiveness of this technique was questioned by the results of a study conducted by Read et al. (2001). In this study, a temporary transphyseal bridging on the lateral aspect of the distal radius was performed to induce a carpal valgus in normal foals. The implants were removed when the ALD reached 15°. Then the foals were separated in two groups. On the foals in group one HCPTE was performed, while the other group had surgery without any correctional interventions. The results showed that the ALD corrected in both groups, meaning that the HCPTE was ineffective. Auer and Von Rechenberg (2006) outline that cross-talk molecule signaling between periosteum and growth plates are responsible for growth acceleration after HCPTE. A feedback loop of PTHrP, PTHrPR and IHH explains the growth acceleration. As the same effect was probably achieved by removal of the transphyseal screws prior to HCPTE and mimic surgery, Auer and Von Rechenberg (2006) indicate the stimulus was applied in both groups. The study of Read et al. (2001) did not mention molecular cross talk. An older theory indicated that the accelerated growth after periostal incision was caused by the release of tension. The basis of this theory may be originated in a study with rats where circumferential incision produced tibial length differences in the hind limb. A vertical incision had no effect on bone growth, and the direction in which the periosteum was incised appeared to be an important factor (Warrell and Taylor, 1979). However, there is growing evidence that transection of periosteum over the metaphysis stimulates growth at the physis due to a more complex process than simply releasing tension. Recent work has suggested that a negative feedback loop between IHH and PTHrP is disrupted when the periosteum or perichondrium is transected, therefore stimulating growth on one side of the physis (Auer and Von Rechenberg, 2006). The criticism on HCPTE on basis of the study of Read et al. (2001) is hereby probably proven irrelevant. There is growing evidence in the literature that HCPTE is effective and has many advantages. First of all it is relatively easy to perform. There may be some swelling at site of surgery and development of a fibrous and/or bony lump, but few other complications are reported (Greet, 2000). A theoretical disadvantage of HCPTE is that the degree of correction seems to be less dramatic than transphyseal bridging. In severe cases a combination of HCPTE and TPB or TPB alone may be more effective, but there is no evidence indicating that this combination results in better or faster correction of the deformity (Greet, 2000).

The primary advantage of transphyseal bridging compared with HCPTE is a more consistent response achieved, and a more dramatic effect on physeal growth, even in severely deformed or older patients. Correction will occur unless the opposite side, which is supposed to keep growing, is damaged or too mature (Howard, 2006). In the foal presented in this case, a screw could theoretically have been placed across the lateral aspect of the distal radial physis to retard growth, allowing the medial aspect to “catch up”. Nevertheless, this procedure is associated with some important disadvantages. Simply the use of implants may be considered a disadvantage because of extra costs and need for a second operation to remove them. The risk of infection comes with all use of implants. Further, some authors have reported less than satisfactory cosmetic results. Probably, trauma to the physis by placement and removal contribute to poor cosmetic appearance (Auer and Von Rechenberg, 2006). Also, the load is placed on a single screw, and as the foal matures, it may bend or the head may be covered in bone, making removal very difficult (Smith, 2010). Auer (2012) reports that resorbable screws are now available. These screws are considerably more expensive than cortex screw, but as removal in not necessary, costs of a second operation is avoided.

An old alternative to screws are staples, which could have been applied medially in this case, similarly as described for the screws. Orthophaedic staples are easier and quicker to place (Hunt, 2000). Nevertheless, there is a limited flexibility in placement caused by the fixed length of the commercial available staples. Using bent Steinmann pins can be an alternative to avoid this disadvantage. In contrast to TPB with screws, there is lack of compression across the growth plate in the early postoperative period with staples, so they may take longer to exert growth retardation effects (Smith, 2010). Further, they are not commonly applied due to implant- and correction failures (Auer, 2006), next to cosmetically unfavorable results (Auer and Von Rechenberg, 2006). Using screws and cerclage or bone plates can correct uneven growth at the physis, following the same principles as described for the transphyseal screws and staples. Swelling, inflammation, and scar tissue formation at the surgical site are quite common complications when implants are used, but typically become less apparent once the limb has straightened, and resolve once the implants have been removed. The possibility of overcorrection should always be kept in mind in order to remove the implants in time. Sometimes premature removal of the implants is required, as a serious potential complication is overcorrection of the ALDs. According to Auer and Von Rechenberg (2006) It is better to end up with a slight valgus than varus by delayed removal of TPB implants. Still, a slight varus might even be indicated as the trauma by removal may cause an enhancement of growth (Pille, F., Personal communication, 2015).

As mentioned for the use of screws, all placement of implants may be associated with an increased risk for infection, and there is need for a second operation for removal. Taking the advantages and disadvantages of these techniques into consideration, HCPTE seemed to be a safe and effective choice of treatment for this foal.

ECSWT, a non-invasive technique, avoids many of the disadvantages of the other techniques. According to Bussy et al. (2013), this technique in combination with corrective farriery and exercise may be successful in cases as severe as this foal. Additionally, it may have been indicated on the RF limb which was only managed by corrective hoof trimming. Still, some of these mild cases might have resolved spontaneously without ECSWT. This procedure can be performed under light sedation, with no risk of infection and no noticeable cosmetic changes of the treated area. This means that implementing ECSWT in the management of ALDs, even though it is not known whether the condition will improve spontaneously or not, is not a problem, and may be beneficial in many cases (Bussy et al, 2013). A combination of growth acceleration and deceleration procedures may be indicated in severe cases, though is most commonly reported for transphyseal bridging in combination with periosteal manipulation (Auer, 2012).

Farriery can help in mild cases, initially in any case, or supplementary to surgery, both for ALDs and FLDs. This foal had corrective trimming, focusing on the valgus deformity, shortly after surgery and every three weeks the following period. The combined skills of the farrier and the veterinary surgeon offered invaluable help in this case. With valgus deformities, the medial aspect of the hoof is subjected to excessive wear. This is mainly seen in cases where the limb shows exorotation in combination with the valgus deformity. In foals with valgus, exorotation of the limbs is very common, and causes a more medial point of breakover, with uneven wear of the hooves (Auer, 2006). Hereby, trimming of the lateral side is an option to give an even confirmation of the sole. The medial side could also be protected against excessive wear with a shoe. Additionally, application of a shoe with an extension in medial direction might be helpful to prevent the abnormal stance associated with valgus (Greet, 2000). In this case the lateral side of the hooves were trimmed, but no extensions were applied. Slight trimming of the heels might in some cases be indicated to treat FLD. This will lower them and put more tension on the flexor tendons.

If this is done, the foal should be monitored for pain and lameness, to assure that the angle changes have not been excessive and thus causing undue pressure of the deep digital flexor tendon and the navicular bone, or painful tension on the suspensory ligament. A toe extension might be indicated in treatment of FLDs. This will delay breakover, and hereby putting forces on the flexor tendons without the risk of overstretching by changing the heel angle. The contraction was mild in this case, and was already solved after three weeks, hereby corrective trimming of the heels was not necessary. This may be indicated in more severe cases of, and mainly for acquired FLDs.

The use of oxytetracycline as treatment for contractural deformities has been mentioned. In mild cases of congenital flexural deformities, OTC may be given intravenously to relax flexor musculotendon units (Lokay and Meyer, 1985; Madison et al., 1994). The most effective results are seen in foals who receive OTC therapy in the first few days of life. Even though it may also be useful in older foals (Adams and Santschi, 2000), it was not considered as an option of the treatment of this foal. This foal’s mild retraction was expected to be solved by a cast on the most affected limb. Further, a comparative study conducted by Madison et al. (2004) found no clinical value of OTC treatment of FLD. In this study a single dose of 44 mg/kg OTC was administered intravenously to newborn foals with and without FLD. The decrease in the fetlock angle was significant in both groups. Nevertheless, the foals in both groups regained their pretreatment angle within 4 days. Auer (2006) reports that the treatment may be repeated once or twice within the first weeks of life to give a better effect. As no adverse side effects were found, this treatment may safely be implemented in the management of FLD, even if the results may be questioned by some authors. As the drug is potentially nephrotoxic, the foal has to be in good condition and be well hydrated to prevent damage to the kidneys (Wright et al., 1993).

Following the surgery of our foal, a tube cast was applied on the LF limb to correct the mild contractural deformity. Such cases will often respond to external coaptation and farrier work (Auer, 2006). Fixed casting of a limb produces tendinous and ligamentous stretching (Wagner et al., 1982), and was effective for treating the FLD of this foal. Whereas the foot was not incorporated, laxity caused by immobilization was avoided. In this case replacement was not necessary as it could be removed when the foal left the clinic. As this treatment gave good results, it is reasonable to believe this was a good choice of treatment, and other treatments would have been excessive. The RF contraction was expected to resolve spontaneously, which was confirmed by the complete straightening after three weeks.

Surgical intervention for the FLD was not indicated in this case, and will not be further discussed.

The prognosis for foals with mild and moderate FLD is good for athletic use. Even horses requiring surgical treatment, such as desmotomy of the accessory ligament of the deep digital flexor tendon may race successfully (Stick et al., 1992). If tenotomy of the DDFT is required for resolution of the FLD, the prognosis for performance is poor. These horses can often be used for pleasure riding, but the prognosis also depends on the response to therapy (Adams and Santschi, 2000). This foal had a mild FLD with good response to therapy.

To determine the prognosis of ALD treatment in a foal, it is also important to evaluate the extent of rotation of the limbs around the limb axis. Some rotation is considered “normal” and should have no effective practical means of correcting ALDs and FLDs, and hereby has a good prognosis. Auer (2006) outlines the importance of a carpus and toe pointing in the same direction. With a toe and carpus pointing slightly outward, the growing chest will cause an inward rotation of the limb, resulting in a normal confirmation. Deformities being primarily rotational, and more severe than “normal” rotation that will straighten, must

be identified. These cases are usually unrewarding candidates for physeal surgery or even conservative management (Greet, 2000). This foal had “normal” rotation, leaving the ALD as the important factor for the prognosis. A study conducted by Baker et al. (2010) evaluated the racing and sales performance of Thoroughbred horses with carpal valgus treated by unilateral or bilateral transphyseal screw placement. They found that correction of one to eight degrees resulted in a group that performed at an equal level compared with siblings. This generally indicates a good prognosis for mild cases. Nevertheless, our foal had a deviation of 19,6° (LF) and 12° (RF), which may be considered severe. Several studies have reported the response to both nonsurgical and surgical treatment of foals with angular limb deformities. In one study, 81.5% of foals treated with HCPTE, achieved total straightening of the limbs. Out of these, 60% were suitable for the intended performance level (Bertone et al, 1985). Generally, the prognosis for foals with ALDs is good, with exception of foals with important abnormalities of the carpal bones, or foals that are treated after six months of age. In these cases the prognosis is less favorable. Foals with carpal valgus are reported to have a better prognosis than with tarsal valgus (Auer, 2006). Auer (2006) reports conflicting results regarding the role of the location of the pivot point and the presence of bony abnormalities. A more distal pivot point may have a poorer prognosis, but some studies found no such correlation. Hereby, it is difficult to give an accurate diagnosis. Six weeks after surgery, the ALDs of this foal’s carpi had decreased from 19,6° to 7,9° (LF) and from 12° to 9,7° (see figure 2). Three and a half months after surgery the foal returned for control, and it was obvious that its legs had become almost straight (see figure 3). Radiography showed that the deviation of the RF limb was more severe than the clinical appearance. Still, much improvement was seen, and the results were satisfying, keeping the expectations in mind. Hereby, it was concluded that treating the RF valgus deformity of the carpus conservatively was a good decision. Further, the very good response to HCPTE on the severely affected left carpus indicates a good choice of treatment. Obviously, the good response to therapy is positive for this foal’s prognosis and one may expect the residual deformity to correct spontaneously in the next months. The owner of this foal had no intentions to use the horse for an athletic career, and the goal was to give it a good life. If the foal can be used for light recreational work in the future, this would be a bonus. Keeping in mind the expectations of the owners and the favorable evolution so far, the prognosis for this foal seems fair.

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