From Our Practice to Yours Emagazine

NORTHEAST ASSOCIATION OF EQUINE PRACTITIONERS

from our practice to yours emagazine

HEAD SHAKERS – IS THERE ANYTHING NEW UNDER THE SUN?

HOW MRI HAS CHANGED THE WAY I READ RADIOGRAPHS AND PERFORM US EXAMINATIONS

DIAGNOSIS AND MANAGEMENT OF CONDITIONS AFFECTING THE NAVICULAR BURSA

THE LATEST ON LAMINITIS

THE USE AND APPLICATION OF THE WOODEN SHOE

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Volume 10, Number 9 October 2020

Executive Committee Board Of Directors Veterinary Industry Council Rep President Ronald B. Gaeta, DVM Mr. Keith Wacker Sarah Cohen, DVM Dunbarton Equine Sound Technologies Inc. Miller and Associates Sasha Hill, DVM Vice President Cleveland Equine Clinic Farrier Industry Council Rep Remco van der Linden Stuart Muir, NZCEF, CJF, DIPWCF, APF Christopher Penola, APF Delta Mustad Hoofcare Center Inc. Podiatry Department, Christopher Penola Farrier Services Rood and Riddle Equine Hospital Bob Pethick, APF, CJF Executive Director/CEO Treasurer Bedminster Forge David G. Dawson Gregory S. Staller, DVM Katherine Chope, VMD, DACVSMR Running ‘S’ Equine Veterinary Services Tufts University Past-President Jim Zeliff, DVM, MBA Allegheny Equine Associates contents

Head Shakers – Is There Anything 6 New Under The Sun?

How MRI has Changed the Way 13 I Read Radiographs and Perform US Examinations

Diagnosis and Management 17 of Conditions Affecting the Navicular Bursa

26 The Latest on Laminitis

The Use and Application 31 of the Wooden Shoe The Clinician 3 THE CLINICIAN OCTOBER 2020

From Our Practice to Yours President’s Letter

Greetings fellow practitioners,

Six years ago when I attended my first Board of Director’s meeting for the Northeast Association of Equine practitioners I thought that I was signing up for a 3 year board position. I now have had the honor and privilege of beginning my 6th year on the Board of Directors as the President of the NEAEP. The NEAEP has always been and will continue to be an extraordinarily special group of practitioners. We are veterinarians and farriers learning, collaborating and furthering the profession by advancing the nuances of the relationship between two equally important parts of the horse’s team. This past year has brought so much upheaval and change to all of our communities and though nothing at all has been easy, the NEAEP has risen to the challenge under the guidance of our past president Dr Jim Zeliff, our virtual symposium committee, our fearless executive director Dave Dawson and our tireless and engaged Board of Directors. The NEAEP has long proven that we are more than a regional educational provider. In the past year we have transformed a top tier association providing education and outreach to veterinarian and farriers to an internationally recognized virtual online learning platform. The NEAEP had actually begun providing valuable and engaging online webinars months before anyone had heard the word Covid and we were able to use our head start to build an excep- tional, user friendly platform for our months long symposium which has now been viewed in 32 countries. This year is sure to be filled with more uncertainty and ups and downs but I am confident that the NEAEP will navigate through them with the deftness of the past year. I am so excited to continue to be a part of the NEAEP’s mission and to help lead such a remarkable association into the year ahead of us.

Sarah President Northeast Association of Equine Practitioners

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Head Shakers – Is There Anything New Under The Sun? Peter R. Morresey BVSc MACVSc DipACT DipACVIM (LA) Rood and Riddle Equine Hospital, Lexington, KY

INTRODUCTION humoral changes, changes in temperature and humidity, Head shaking in horses is a syndrome of many alleged causes allergen exposure or unknown environmental factors and numerous touted treatments. It is a source of frustration to contribute to the onset of the headshaking syndrome. owners, trainers and veterinarians alike. Often a diagnosis of exclusion, a systematic and comprehensive work-up is necessary to PATHOPHYSIOLOGY OF eliminate treatable organic disease that may manifest as shaking of HEAD SHAKING the head. Contemporary theories on pathophysiology, diagnostic Shaking of the equine head can be associated with approaches, and current treatment of head shaking are discussed. frustration or anticipation of activity. It is also a response to noxious stimuli – insects, poorly fitting tack SIGNALMENT and restraint. While there is a long list of potential caus- The mean age at onset (or recognition) of headshaking has es of headshaking, many are not amenable to treatment. been reported in various studies, both clinical and owner observa- Those amenable to medical or surgical treatment in tional, as 7.3, 7.5, and 9 years (Lane, 1987;Madigan, 2001;Mills, include temporohyoid osteoarthropathy, trigeminal 2002). Geldings in these studies were over-represented (63–78%) neuralgia and allergic reactions. Other causes include however breed predilection was detected. In the populations hormonal imbalances and vascular changes. studied, many affected horses were acquired by the current owner in late autumn or winter when headshaking was not present or Temporohyoid osteoarthropathy (THO) apparent to the new owner (Lane, 1987;Madigan, 2001). Headshaking with or without deficits of the facial and/or vestibular nerves has been attributed to bony CLINICAL SYNDROME proliferation of the temporohyoid joint and proximal Headshaking syndrome is commonly seen during exercise, shaft of the stylohyoid bone. While some reports particularly at a trot when the head is held relatively stationary. indicate an infectious etiology (recovery of bacteria via However, it can also occur at rest or during other gaits. Affected tympanocentesis or necropsy (Blythe, 1997;Power, horses display a characteristic headshaking or head-tossing in a 1983), others have not (Naylor, 2010). The predilection vertical plane. Other signs include snorting, rapid movements of for Quarter horses, Paints and Appaloosas also speaks the upper lip, nasal discharge, lacrimation, and rubbing or striking against an infectious etiology. the nares or side of the face with a foreleg or fixed object. Affected horses are most commonly presented The majority of affected horses have a seasonal worsening of when neurological deficits develop. Bony proliferation signs. Onset occurs in spring with signs continuing until late leads to impingement of either or both of the facial and summer or autumn. This suggests photoperiod associated neuro- vestibular nerves in the area of the acoustic meatus. The

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onset of neurologic signs may be acute (vestibular ataxia, facial trigeminal nerve, the ganglion and several branches from head- nerve deficits), chronic (persistent corneal ulceration resulting from shaking horses has not revealed demyelination or other pathology diminished tear production or blinking), or initially subtle but (Newton, 2001). However, increased excitability of the nerve has progressive (as with the onset of a head tilt, trouble with the bit, or been demonstrated following stimulation of the trigeminal nerve in difficulty chewing) (Blythe, 1997;Walker, 2002). four horses with headshaking syndrome (Pickles, 2011b). Trigeminal ganglion infection with latent EHV-1 has been Trigeminal neuralgia/neuropathy (TN) investigated as a cause of altered trigeminal nerve function. In the horse, TN triggers include bright light or sunshine However, latent EHV-1 as detected by real-time PCR, was recov- (photic headshaking), touch, auditory and olfactory stimuli ered from only one of eight geldings with headshaking syndrome (Madigan, 1995;Madigan, 2001;Mills, 2002). Also, exercise-induced (Aleman, 2012). increases in airflow through the nasal passages, blood flow to nasal and turbinate mucosa, and maxillary arterial pulse profile Luteinizing hormone (LH) (Newton, 2000). Headshaking syndrome is observed most frequently in As a cause of headshaking, TN was first considered over a geldings and displays a seasonal occurrence. Increased activity of century ago (1899) following successful treatment by infraorbital gonadotropin releasing hormone (GnRH) leading to increased neurectomy (Williams, 1899). Further supporting evidence has circulating concentrations of luteinizing hormone (LH) and been provided more recently, as follicle-stimulating hormone (FSH), could lead to seasonal changes perineural anesthesia of in trigeminal nerve excitability in affected geldings (Pickles, 2011a). branches of the trigeminal However, GnRH vaccine was administered to geldings with nerve has led to transient headshaking syndrome decreased LH and FSH concentrations but improvement, with did not ameliorate signs of headshaking (Pickles, 2011a). lasting improvement reported following Allergy neurectomy, As headshaking has a seasonal prevalence, it has been hypothe- chemical sclerosis, sized that headshaking syndrome may be initiated by allergic or coil compres- reactions (LANE, 1987). Cough (27% of cases evaluated) and sion of the excessive tracheal mucus (32% of horses examined by airway infraorbital or endoscopy) in keeping with recurrent airway obstruction (RAO or maxillary nerves ‘heaves’). Allergic rhinitis associated with these conditions in (Mair, 1999;Mair, humans, affecting up to 30% of adults and 40% of children, may 1992;Newton, trigger headshaking syndrome. Serous nasal secretions, congestion, 2000;Roberts, sneezing, and airflow obstruction present in humans with allergic 2009;Roberts, 2013). rhinitis can be associated with facial pain. However investigation in Paralleling TN as a cause of horses (nasal mucosal biopsies, gross and microscopic examination headshaking in horses, TN in of the head and nasal passages), of headshakers has not supported humans can cause a shooting or this hypothesis. burning sensation across the face. The maxillary branch is most often affected with right-sided disease more prevalent (considered Vasomotor rhinitis due to a narrower right foramen rotundum and foramen ovale Non-allergic rhinopathy (vasomotor rhinitis) has been through which the nerve passes). In people with classical TN documented to cause headshaking syndrome (Lane, 1987;McGo- (parallels idiopathic headshaking in horses) is partial demyelination rum, 1990). Being non-seasonal and non-allergic in origin, it is of the trigeminal nerve is the only pathological finding, and is considered that altered autonomic control of nasal mucosal blood thought to be associated with vascular compression. It is consid- flow and secretions precipitates the condition. With increased ered that the resulting demyelination disturbs trigeminal nerve airflow during exercise, clinical signs that are indistinguishable electrophysiology, resulting in ectopic electrical impulses that from allergic rhinitis may develop. Vasoconstrictive drugs (i.e. precipitate facial pain (Zakrzewska, 2002). Histopathology of decongestants) and intranasal corticosteroids can alleviate signs.

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Photic headshaking nerve requires an extended period for diffusion of the anesthetic to In humans, photic stimulation via the optic nerve leads to a achieve a full effect (Aleman, 2014;Newton, 2000). tickling sensation in the nasal mucosa (Whitman, 1993). This may be the result of light stimulation of the optic nerves causing TREATMENT activation of the maxillary branch of the trigeminal nerve, or Headshaking may be a response to a noxious stimulus, regional parasympathetic branches (Everett, 1964). It has been whether physiological or behavioral. Removal of the source of postulated that the photic trigger is present in some horses with discomfort or treatment of the underlying organic disease is headshaking similar to this human photic sneeze (Madigan, 1995). necessary in all cases. However, since the etiology of idiopathic Clinical signs of photic headshakers are indistinguishable from headshaking is unknown, there are no specific or demonstrably those of non-photic headshakers (Madigan, 2001;Newton, 2000). curative treatments currently. The basis of control is therefore This suggests multiple triggers activate the same final effector management (where possible) and not cure. Currently reported trigeminal response. Such stimuli include sound (metal sound, treatments have a low success rate, and do not correct the underly- clap), eating (hard carrots, fibrous hay), and nasal mucosal stimula- ing abnormal trigeminal neurophysiology. tion via diagnostic nasal swabbing (Aleman, 2014). As some horses have been noted to go into spontaneous remission, it seems possible that the aberrant trigeminal nerve DIAGNOSIS physiology and activity might be reversible. Ameliorating the disturbed nerve function appears to hold promise as the key to History and characteristics of headshaking successful treatment. A detailed history should be taken from the owner. This can Environmental management to avoid established precipitating include management procedures, diet, exercise and environmental stimuli is central to control. This may involve riding at night or in changes. When investigating idiopathic headshaking following low light situations, but this is impractical especially for competi- exclusion of other diseases, the characteristic head motion (rapid tion horses. Nose nets and face masks have enjoyed some success, downward motion of the nose followed by upward flinging of the with up to 75% of owners reporting measurable improvement with head) should be present. appliances ranging from full coverage of the muzzle and lips, to coverage of only the nostrils and upper lip (Mills, 2003). Physical examination Medication usage is commonplace, with a number of com- In addition to a complete general examination which includes pounds reported to be at least partially effective in reducing severity the oral cavity, ophthalmic and otoscopic examinations are needed. of presentation (Table 1). As with all pharmaceutical usage, Endoscopy of the upper airway, including the guttural pouches, and deleterious effects and tendency to overuse are of concern, as is radiography of the head and throatlatch region are indicated. violation of regulations relating to competition withdrawal times. Computed tomography (CT) and magnetic resonance imaging Surgical approaches have been reported. Infraorbital neurecto- (MRI) improve visualization of both bone and soft tissue. my first appeared in the veterinary literature in the late 1800s (Williams, 1899). Response is minimal and a high post-surgical Local anesthesia of the infraorbital nerve complication rate suggests this procedure is contraindicated (Mair, Used as an aid to diagnosis but reported success is low. 1999). Chemical sclerosis of the posterior ethmoidal nerve Infraorbital anesthesia with 2% mepivacaine improved 3/19, had no similarly suffers from a lack of efficacy with a high rate of reoccur- effect on 8/19, and worsened 8/19 horses (Mair, 1999). In another rence reported (Newton, 2000). The placement of platinum coils to study only 1/8 horses improved and only by 50% however the compress the caudal infraorbital nerve has been reported used in volume of mepivacaine was lower (Newton, 2000). A higher horses unresponsive to medical therapy, with up to 50% success volume of local anesthetic infiltration may however affect achieved however multiple surgeries were required in some horses adjacent nerves. due to repeated reoccurrence of headshaking (Roberts, 2009;Rob- Bilateral anesthesia of the posterior ethmoidal nerve (maxillary erts, 2013). Due to post-operative complications including nerve) improved 13/17 horses (Newton, 2000) and 23/27 horses increased severity of nose rubbing progressing to self-trauma, (Roberts, 2013) with headshaking. However the location of the surgical interventions should be considered salvage procedures for horses non-responsive to other modalities and at risk of euthanasia.

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TABLE 1

TREATMENT DOSE/FREQUENCY COMMENTS Cyproheptadine 0.3mg/kg po q12h Moderate improvement. Lethargy Carbamazepine 2-8mg/kg po q6h-q12h Moderate improvement. Unpredictable efficacy. (may be used in combination with cyproheptadine). Hydroxyzine 1mg/kg po q12h Moderate improvement. Fluphenazine 50mg im. Repeat 1-4 monthly Neurological dysfunction. Phenobarbital 3-6mg/kg po q12h Calmative. Sedation. Gabapentin 5-20 mg/kg po q12h-q24h Anecdotal reports, variable. Corticosteroids Standard dosage, also pulse therapy Variable success reported. Magnesium Variable Calmative. Melatonin 15-18mg po q24h Dose 5pm. Altered hair shedding. Sodium cromoglycate eye drops Apply OU q6h Seasonal head shakers.

Adapted from: (Madigan, 2001) (Mair, 1999) (Madigan, 1995) (Newton, 2000) (Pickles, 2014) (Stalin, 2008) (Tomlinson, 2013)

Reference List Mair TS, Howarth S and Lane JG. Evaluation of some prophy- Aleman M, Pickles KJ, Simonek G, et al. Latent Equine lactic therapies for the idiopathic headshaker syndrome. Equine Vet J Herpesvirus-1 in Trigeminal Ganglia and Equine Idiopathic Head- 1992;24(S11):10-2. shaking. J Vet Intern Med 2012;26(1):192-4. McGorum BC and Dixon PM. Vasomotor rhinitis with Aleman M, Rhodes D, Williams DC, et al. Sensory Evoked headshaking in a pony. Equine Vet J 1990;22(3):220-2. Potentials of the Trigeminal Nerve for the Diagnosis of Idiopathic Mills DS, Cook S, Taylor K, et al. Analysis of the variations in Headshaking in a Horse. J Vet Intern Med 2014;28(1):250-3. clinical signs shown by 254 cases of equine headshaking. The Veteri- Blythe LL. Otitis media and interna and temporohyoid osteoar- nary record 2002;150(8):236-40. thropathy. The Veterinary clinics of North America Equine practice Mills DS and Taylor K. Field study of the efficacy of three types 1997;13(1):21-42. of nose net for the treatment of headshaking in horses. The Veterinary Everett HC. Sneezing in response to light. Neurology record 2003;152(2):41-4. 1964;14(5):483. Naylor RJ, Perkins JD, Allen S, et al. Histopathology and Lane JG and Mair TS. Observations on headshaking in the computed tomography of age-associated degeneration of the equine horse. Equine Vet J 1987;19(4):331-6. temporohyoid joint. Equine Vet J 2010;42(5):425-30. Madigan JE, Kortz G, Murphy C, et al. Photic headshaking in Newton SA. The fuctional anatomy of the trigeminal nerve of the horse: 7 cases. Equine Vet J 1995;27(4):306-11. the horse. University of Liverpool; 2001. Madigan JE and Bell SA. Owner survey of headshaking in Newton SA, Knottenbelt DC and Eldridge PR. Headshaking in horses. Journal of the American Veterinary Medical Association horses: possible aetiopathogenesis suggested by the results of diagnostic 2001;219(3):334-7. tests and several treatment regimes used in 20 cases. Equine Vet J Mair TS. Assessment of bilateral infra-orbital nerve blockade 2000;32(3):208-16. and bilateral infra-orbital neurectomy in the investigation and treatment of idiopathic headshaking. Equine Vet J 1999;31(3):262-4.

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Pickles KJ, Berger J, Davies R, et al. Use of a gonadotrophin-re- caudal compression of the infraorbital nerve for its treatment, in 58 leasing hormone vaccine in headshaking horses. Veterinary Record horses. Equine Vet J 2013;45(1):107-10. 2011a;168(1):19. Stalin CE, Boydell IP and Pike RE. Treatment of seasonal Pickles KJ, Gibson TJ, Johnson CB, et al. Preliminary investiga- headshaking in three horses with sodium cromoglycate eye drops. The tion of somatosensory evoked potentials in equine headshaking. The Veterinary record 2008;163(10):305-6. Veterinary record 2011b;168(19):511. Tomlinson JE, Neff P, Boston RC, et al. Treatment of Idiopathic Pickles K, Madigan J and Aleman M. Idiopathic headshaking: Is Headshaking in Horses with Pulsed High-Dose Dexamethasone. it still idiopathic? The Veterinary Journal 2014;201(1):21-30. J Vet Intern Med 2013;27(6):1551-4. Power HT, Watrous BJ and de Lahunta A. Facial and vestibulo- Walker AM, Sellon DC, Comelisse CJ, et al. Temporohyoid cochlear nerve disease in six horses. Journal of the American Osteoarthropathy in 33 Horses (1993-2000). J Vet Intern Med Veterinary Medical Association 1983;183(10):1076-80. 2002;16(6):697-703. Roberts VLH, Mckane SA, Williams A, et al. Caudal compres- Whitman BW and Packer RJ. The photic sneeze reflex Literature sion of the infraorbital nerve: A novel surgical technique for treatment review and discussion. Neurology 1993;43(5):868. of idiopathic headshaking and assessment of its efficacy in 24 horses. Williams LW. Involuntary shaking of the head and its treatment Equine Vet J 2009;41(2):165-70. by trifacial neurectomy. American Veterinary Review 1899;23:321-6. Roberts VLH, Perkins JD, Skärlina E, et al. Caudal anaesthesia Zakrzewska JM. Diagnosis and Differential Diagnosis of Trigem- of the infraorbital nerve for diagnosis of idiopathic headshaking and inal Neuralgia. The Clinical Journal of Pain 2002;18(1).

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How MRI has Changed the Way I Read Radiographs and Perform US Examinations Natasha Werpy, DVM, DACVR Radiology Department, University of Florida

MANY LESIONS APPEAR OBVIOUS using the location of the osseous abnormality and amount of superimposi- advanced imaging, such as Magnetic Resonance Imaging (MRI). tion of adjacent bone(s). Peripheral osseous proliferation and These same lesions can appear obscure on other modalities. This resorption will be most easily detected on ultrasound, followed by often results in the impression that these lesions were not able to be radiographs (again dependent on superimposition). The visibility of diagnosed with other modalities. However, this may not be the peripheral osseous proliferation on MRI is quite dependent on the case or may only be the case initially. Advanced imaging provides a character of the adjacent tissues. Osseous proliferation is typically great educational tool that will cause us to reexamine the results of dark gray to black on MR images, which is similar in signal intensity other imaging modalities with great scrutiny. This reexamination to joint capsule, tendons, and ligaments. The osseous proliferation will set in motion a process that will make us better at reading can blend into the adjacent soft tissue structures. Although an radiographs, as well as obtaining and interpreting ultrasound abnormality can be detected on the MR image, differentiating soft images. It will not change the fact that certain lesions will require tissue from bone can be challenging. These cases benefit from advanced imaging for a diagnosis. In contrast, other cases will ultrasound and radiographs, despite having MR images. initially require advanced imaging for a diagnosis. However, the Although certain osseous abnormalities can be more difficult knowledge gained from these cases will facilitate the development to identify on MRI, others are quite obvious. The study of these of the skills necessary to make the diagnosis without advanced abnormalities leads to the development of methods to identify them imaging in the future. on other imaging modalities. Retrospective study of radiographs All modalities have advantages and disadvantages. Despite the and detection of an osseous lesion that was not recognized on the vast information obtained with advanced imaging, using different initial reading adds another systematic step to radiograph evalua- modalities in conjunction is often a requirement for obtaining all the tion, ensuring we will recognize that lesion in the future. In necessary diagnostic information about a lesion. Owner education addition, MRI can demonstrate predilection sites for certain about this fact is important as it prevents the common scenario that osseous lesions that might not be initially recognized on radio- MRI answers “all questions”, which we recognize is not always true. graphs. As an example, MRI is reported to be superior to radio- Owner education is always easier done prior to completion of the graphs for the identification of periarticular osteophytes on the 1 study, as opposed to justifying additional imaging after the comple- margins of the metacarpophalangeal joint. However, using MRI as tion of a MR study that required a considerable financial investment. a guide to determine the predilection sites for osteophyte develop- Understanding the strengths and weaknesses of the modalities can ment, followed by subsequent, meticulous evaluation of these sites facilitate this conversation with owners. Having owners understand facilitates identification of the osteophytes. In contrast, MRI has the potential need of additional diagnostics following a MR study will shown that in many cases significant articular cartilage damage can allow you the opportunity to obtain all the necessary information be present in the distal interphalangeal joint (DIPJ) without any before making a final diagnosis. evidence of osteophytes, trabecular bone fluid or trabecular bone Radiographs, and to a greater degree ultrasound, can be more sclerosis. Therefore, close and diligent radiographic evaluation in sensitive to osseous abnormalities than MRI. This is dependent on these cases will not yield any findings due to the absence of

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radiographically detectable abnormalities. With this knowledge we appearance can also be quite challenging to identify with ultra- recognize that a lack of radiographic or scintigraphic abnormalities sound. However, off angle imaging provides a great advantage in in a horse with lameness, which resolves following intra-articular creating a difference in the echogenicities of different tissue types, analgesia of the DIPJ may still have significant joint injury. thereby allowing their delineation. It is important to note that Similar to radiographs, ultrasound will be superior at demon- margin fraying in areas where the ultrasound cannot be positioned strating certain abnormalities. In addition, MRI will help us to strike the soft tissue margin at a perpendicular or 90 degree angle become better ultrasonographers. Finding a lesion on ultrasound will be much better demonstrated on MR images. when using a 4-5 cm depth can cause the lesion to look quite large. In addition to better define soft tissue margins, off angle Even a small margin defect in a tendon or ligament can occupy 25% ultrasound imaging is highly beneficial when examining structures of the screen image. When that anatomic region is imaged using with complex anatomy and different tissue types, such as the MRI the margin defect can get lost in the detailed anatomy on the suspensory ligament. Knowledge obtained from MRI studies has MR images. The global view of the anatomy obtained with MRI, resulted in a better understanding of suspensory ligament anatomy.2 while extremely advantageous in many ways, can sometimes This knowledge led to the development of innovative US techniques obscure small, yet important abnormalities. A small surface DDFT that better represent the anatomy of the ligament, facilitating the lesion can precipitate tenosynovitis in the digital sheath. This type diagnosis of injury.3 In addition to off angle imaging, imaging soft of lesion can benefit from tenoscopy and in certain cases is more tissue structures with the limb in a non-weight bearing position can easily detected with ultrasound. Similar to differentiating osseous improve visualization of anatomy, allow manipulation of tissues, proliferation from synovial tissue on MR images, defects in soft and is required for dynamic examination. Imaging the limb in a tissue structures can be occupied by synovial proliferation with a non-weight bearing position can be performed in most cases similar signal intensity obscuring it on the MR images. This without significant alterations in the echogenicity of soft tissue structures. The comparison between US and MRI when evaluating soft tissue structures will continue to advance our US skills. MRI will change what a “complete” ultrasound examination entails. However, if a MRI study of an anatomic region takes 45-60 minutes to complete, it will take at least that long or longer to attempt to achieve the maximum information available from ultrasound. The goals of the this presentation are to demonstrate the strengths and weakness of the different modalities in conjunction with examples that will provide a guide for understanding how MRI has advanced our skills when reading radiographs and performing ultrasound examinations.

References: 1. Olive J, D’anjou M-A, Alexander K, Laverty S, Theoret C. Comparison of magnetic resonance imaging, computed tomography, and radiography for assessment of noncartilaginous changes in equine metacarpophalangeal osteoarthritis. Veterinary Radiology & Ultrasound. 2010;51(3):267–79. 2. Werpy NM. Ultrasound of the suspensory ligament using perpendicular and oblique beam angles for identification of anatomy with comparison with MRI. 57th Proc Am Assoc Eq Pract, San Antonio, TX 2011 3. Denoix J-M, Coudry V, Jacquet S. Ultrasonographic procedure for a complete examination of the proximal third interosseous muscle (proximal suspensory ligament) in the equine forelimbs. Equine Veterinary Education. 2008;20(3):148–53.

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American Farriers Team is selected from the Cultural Exchange Program — The exchanges top competitors at the annual National Forging with the United Kingdom, South Africa, and & Horseshoeing Competition during the AFA Australia offer farriers a once-in-a-lifetime Convention. The AFT represents the USA in experience of living and working with top international competitions. international farriers who will broaden your knowledge and improve your skills. Jim Linzy Memorial Fund sponsors the Keynote Speaker at the convention and helps fund Equine Research Fund supports a grant system benefit clinics for injured and ill AFA member that allows farriers to produce research that is farriers. Through the Bruce Daniels Memorial sophisticated enough to be read in veterinary Scholarship it awards $500 for the purchase of and research circles and makes an impact on tools to nominated recent graduates of our everyday shoeing. horseshoeing schools. THE CLINICIAN OCTOBER 2020 NEAEP

Diagnosis and Management of Conditions Affecting the Navicular Bursa José M. García-López, VMD, Diplomate ACVS and ACVSMR Tufts University Cummings School of Veterinary Medicine, North Grafton, MA

INTRODUCTION diagnostic anesthesia be performed. When dealing with conditions Navicular disease is a term that has been used historically to localized to the foot, radiographs are a traditional first line of describe a musculoskeletal disorder in horses with palmar or diagnostics used by most equine practitioners. Although there have plantar foot pain with or without radiographic lesions within the been significant advances in the quality of image acquisition with distal sesamoidean (navicular) bone1-3. Traditionally diagnosis has the use of computed or digital radiography, there are still inherent been based on the horse’s response to palmar (plantar) digital limitations with this modality such as summation of densities and anesthesia and radiographic findings. With the use of more superimposition of the structures. In addition, radiography fails to sensitive and specific imaging modalities such as ultrasound, nucle- give the clinician information regarding soft tissue structures such ar scintigraphy, magnetic resonance imaging (MRI) and Computed as the DDFT, CSL, DISL and collateral ligaments of the distal Tomography (CT), a great deal of information has been obtained interphalangeal (DIP) joint. regarding injury to the various components of the equine podo- Ultrasonography of the podotrochlear apparatus has been trochlear apparatus, including the navicular bone, the deep digital described in the literature and has become an important diagnostic 9,10 flexor tendon (DDFT), the podotrochlear (navicular) bursa, the modality for many practitioners . Ultrasonography of the foot collateral sesamoidean ligament (CSL), and the distal sesamoidean has limitations such as the presence of a limited imaging “window” impar ligament (DSIL)4-8. As navicular disease is not a single through the bulbs of the heel and frog, level of complexity and high disease process but rather a syndrome with many clinical entities dependency on operator’s expertise. Grewal and McClure (2004) that can contribute to pain within the podotrochlear apparatus, concluded in their study on normal horses and those clinically treatment options, rehabilitation programs and prognosis for affected with navicular syndrome that ultrasound was a useful tool 3 athletic use can be highly variable. in diagnosing causes of caudal heel pain . We have found likewise The aim of this presentation is to discuss the diagnosis of in our clinical practice. Certainly, though, limitations exist and conditions involving the navicular bursa such as adhesions and ultrasound is less sensitive than high filed MRI for evaluation of DDFT lesions with the aid of ultrasound, MRI and navicular the foot. However, with experience, careful sonographic evalua- bursoscopy. We will discuss the benefits and limitations of tion of the foot can provide important diagnostic information in commonly used diagnostic modalities, as well as our experience many horses. It is this author’s opinion that it remains a reasonable managing these conditions. imaging option, particularly in cases where finances, location, timing or other concerns prevent performing an MRI. Future studies correlating findings on ultrasound with MRI (as well as DIAGNOSTIC MODALITIES other modalities) should aid in improving our diagnostic skills and Regardless of the diagnostic tools or equipment available, it is may help further define the role of ultrasound in this area. imperative that a thorough physical examination together with a Nuclear scintigraphy has been used regularly for over 15 years lameness evaluation (in-hand on a straight line and circle) and in the United States during the routine work-up of equine lameness,

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and can provide an objective assessment of bone activity in this bursa is the primary structure affected in order to attain a higher region. It has a sensitivity much greater than that of digital concentration of anti-inflammatories in to the area. This can be radiography since the radiopharmaceutical uptake (hot spot) is particularly effective and therapeutic in cases of primary navicular related to the osteoblastic activity of the bone. However it lacks bursitis16. However as Bell and colleagues reported (2009), such specificity, meaning that it is important to use it in conjunction with therapy may prove ineffective or short lived if the source of the other diagnostic modalities such as MRI, CT, radiography and/or discomfort is due to adhesions or DDFT lesions within the bursa16. ultrasound. However despite its increased sensitivity when Novel Systemic Treatments and Orthobiologics- The use of compared to radiography, the lack of radiopharmaceutical uptake Tildren® (Tiludronic Acid; CEVA Sante Animale, France) and now does not preclude certain lesions or conditions to be present Osphos (Decra Veterinary Products, Overland Park, KS) in cases of such as insertional desmopathies of the collateral ligaments of navicular degeneration has been shown to be a useful treatment the DIP joint11. option particularly when used in conjunction with corrective It is generally accepted nowadays the use of MRI (in particular shoeing and other therapies such as shockwave therapy, navicular high field MRI) as the gold standard for a complete examination of bursoscopy, and intra-articular administration of corticosteroids the equine foot. Contrast enhanced CT is another imaging (triamcinolone acetate or methylprednisolone acetate), hyaluronic alternative that can equal or surpass the image quality of certain acid, Polyglycan® (Arthrodynamic Technologies, Versailles, KY; low field MRIs. Among some of it advantages, MRI can provide 2.5-5 ml either alone or in combination with corticosteroids), and the clinician with an objective assessment of both bony and soft IRAP 2® (Arthrex Vet Systems, Bonita Springs, FL; 3-4ml dose tissue structures. Lesions affecting the DDFT, DSIL, CSL and into the DIP joint every 7 days for 3 treatments). collateral ligament of the DIP joint might occur more commonly Intra-lesional Therapy for DDFT than once thought. A number of studies have been published which lesions- As our knowledge of this describe the MRI appearance of the podotrochlear apparatus in region improves based on the both sound and lame horses4,6,12. The MRI appearance of adhesions improvement in ultra- within the podotrochlear bursa between the DDFT and the flexor sound equipment and surface of the navicular bone has been described in multiple techniques as well as publications using histopathology as a gold standard for diagno- the more common sis8,13. With our increased knowledge of conditions affecting the use of MRI, we navicular bursa such as DDF tendonitis, CSL desmitis, adhesions have learned that and flexor surface erosions and their effect on locomotion, lesions affecting minimally invasive techniques such as navicular bursoscopy are the DDFT are not being used more commonly now in order to manage these uncommon. more effectively14. Lesions in this tendon at the level of THERAPEUTIC MANAGEMENT the navicular bursa “Traditional”- Treatment of navicular syndrome has tradi- vary from mild fibrilla- tionally involved a combination of NSAIDS, corrective trimming tion of the dorsal border of and shoeing, intra-articular administration of corticosteroids into the tendon, to longitudinal the distal interphalangeal joint, and ultimately palmar digital tears and traditional “core” neurectomy (not discussed in this presentation)1,16. In addition, lesions. As we will discuss below, intrabursal injection of corticosteroids and/or hyaluronic acid has lesions that “break out” dorsally might benefit from surgical been described as an alternative treatment in horses with signs of debridement through minimally invasive techniques (bursoscopy) navicular syndrome that do not respond to traditional treatment before considering intra-lesional therapy with either stem cells, methods16-18. Despite the effective diffusion of corticosteroids platelet rich plasma (PRP) or bone marrow aspirate concentrate between the DIP joint and the navicular bursa that recent studies (BMAC). However, similar to other regions in the equine distal have shown18, direct infiltration of the navicular bursa is recom- limb, central core lesions or defects can be treated using these mended over infiltration of the joint in cases where the navicular products without the need of surgery.

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Currently there are several sources for veterinarians to obtain regeneration, promote stem cell bindings and healing due to in part stem cells for clinical use: marrow derived, adipose-derived by the large concentration of growth factors within them, such as (vascular stromal fraction cells) and embryonic-like stem cells. All PDGF, TGF-β and VEGF, which become activated upon platelet of these have their own advantages and disadvantages ranging from lysis or rupture. PRP has been used also in combination with stem processing time (adipose derived cells are typically available 48-72 cells as a way to provide further growth factors in order to “im- hours following shipping, marrow derived cells take 2-3 weeks for prove” the efficacy of the treatment. However, there is limited if any adequate culture and expansion), cosmetic impact (scar at the site clinical evidence available to date that objectively assesses the of sample harvest), chance for teratoma formation (historically benefit of such combination in equine patients. There are several been a big concern when using embryonic cells although this has companies in North America that provide the materials or kits not been reported following a large multi-center clinical trial), and necessary to process the patient’s blood in order to obtain PRP, subjective efficacy based on the lesion being treated. ranging from gravity filtration systems to centrifugation systems. Platelet Rich Plasma or PRP is another therapy that has gained The procedure is easy to perform in either a clinic or ambulatory significant popularity and acceptance in particular when treating environment; although the chances of reactions or flares are soft tissue injuries in equine athletes. More recent studies have also minimal due to the autologous nature of the product, it is impera- shown the potential benefit of PRP in cases of OA or articular tive to adhere to aseptic principles during the collection, prepara- defects. PRP was originally described in maxillofacial surgery as a tion and injection into the lesion. way to promote better bone formation and growth in cases of large Bone marrow aspirate concentrate or BMAC is yet another bony defects. PRP involves a high concentration of autologous option in the regenerative therapy repertoire. BMAC requires a platelets in a small volume of plasma. Platelets, in addition to being bone marrow aspirate similar to that obtained for culture and a wound and vascular sealant, can provide a scaffold for tissue expansion of stem cells. However, the aspirate goes through a series

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of filtration and centrifugation steps which create a concentrate flexor surface of the navicular bone14,20,21. In their report, Smith and similar to PRP with regards to growth factors and other scaffolding colleagues (2007) approximately 70% of the horses suffering from agents but with the added benefit of a limited number of stem cells DDFT lesions and erosions to the flexor surface of the navicular (approximately 13% of the mononucleated cells found in the bone returned to their previous level of soundness following aspirate). The platelet and mononuclear cell counts as a whole in endoscopic debridement of the lesions14. Recently, Smith and BMAC represent an increase of 7-8 fold of those found in a regular Wright (2012) reported on the management and outcome of 92 aspirate. It is important to point out that BMAC does not have cases that underwent navicular bursoscopy for the management of anywhere near the number of stem cells found in a sample that has conditions such as DDFT lesions and similarly found that 61% of been cultured and expanded. The use of BMAC has gained the horses returned to work sound with 42% returning to their popularity or preference in the clinical setting for the past 1-2 years previous level of performance22. At our hospital we have observed a based not only in the fact that it is less expensive (however it is similar outcome when using bursoscopy in these cases, either alone more expensive than PRP) and has quicker turnaround time (it or in combination with other therapeutic modalities such as takes approximately 30 minutes to process) when compared to intra-lesional therapy with PRP or stem cells. Similar to other cultured stem cells, but also based on experimental evidence that reports14,22, in our experience the presence of lesions of the DDFT shows similar characteristics in the quality of repair when com- concurrently with erosions/degeneration of the flexor surface of the pared to marrow derived stem cells. In addition to its use treating navicular bone carry a worse prognosis to return to the previous tendon and ligamentous injuries, BMAC has shown promise in the level of soundness than when the flexor surface of the navicular management of SBCs and full thickness cartilage defects. In these 2 bone is not involved. conditions, BMAC can be deposited into the defects with or Prior to considering navicular bursoscopy it is imperative that without the use of Hydroxyapatite or Tricalcium Phosphate (TCP) the lesion(s) be adequately identified in order to design an optimal as a mineral scaffold, and activated into a gel by adding thrombin surgical and post-surgical plan to be discussed with the owner and and CaCl2. trainer ahead of time. For this reason MRI of the affected foot Although there is limited in vivo information that objectively (feet) is typically done at our hospital in horses with conditions assesses the efficacy of these therapies, due to the general safety of localized to the foot and where involvement of the navicular bursa the products, ease of access and our constant pursuit of the best is strongly suspected. Following the MRI, an ultrasound is per- “cure” for our equine athletes, the clinical use of stem cells, PRP and formed (even if one was done prior to the MRI) in order to BMAC have outpaced or in some cases by-passed objective clinical accurately “map” the lesion sonographically and establish a baseline research. Because of this, although subjectively we believe that for the follow up ultrasound examinations. these therapies do enhance or improve the quality of the repair in Navicular bursoscopy can be done with the patient in lateral or both soft tissue and cartilaginous (articular) injuries, we still don’t dorsal recumbency, although this author prefers the lateral recum- have a full and objective idea of the full benefit (or lack thereof), bency. In order to reduce bleeding, a tourniquet applied to the mid effectiveness and clinical indication of these products. In addition, third metacarpal (tarsal) bone can be applied. Based on the regardless of which regenerative therapy we choose, careful, closely location of the lesion, the surgical approach can be done using a controlled and monitored (particularly with the use diagnostic traditional19,20 or transthecal approach14. In our hospital when modalities such as ultrasound) rehabilitation program is paramount using a traditional approach, in order to avoid penetration of the in order to achieve the best possible outcome. palmar (plantar) pouch of the DIP joint, distension of the bursa is Navicular Bursoscopy- Endoscopy of the navicular bursa achieved either under fluoroscopic or digital radiographic guidance (navicular bursoscopy) was originally described as a preferred using radio-opaque contrast material diluted to a 25% strength with alternative to the traditional “street nail” procedure in cases of sterile saline. Once in the bursa a combination of motorized foreign body penetration of the navicular bursa through the frog19. synovial resectors and rongeurs are used to debride the lesion(s) This technique revolutionized the way equine surgeons approached effectively. Following adequate debridement, the bursa is thorough- this region as well as greatly improving its prognosis to return to ly lavaged, the skin incisions are sutured in a routine fashion and 4 athletic soundness. More recently navicular bursoscopy has been ml of Polyglycan® is injected into the bursa. described as a method of diagnosing and treating lesions within the In order to try to reduce the load of the DDFT onto the navicular bursa, including lesions in the deep digital flexor tendon, navicular bone, an egg bar shoe with a 4-5 degree wedge pad is the collateral sesamoidean ligament, the impar ligament, and the applied to the foot immediately following surgery. Physical therapy

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CMY

K THE CLINICIAN OCTOBER 2020

in the form of hand-walking exercise is initiated 72 hours following Blunden A, Murray R, and Dyson S. Lesions of the deep digital surgery in order to minimize adhesion formation and re-introduce flexor tendon in the digit: A correlative MRI and post mortem study normal gliding to the tendon. A typical case will begin hand-walk- in control and lame horses. Equine Vet J 2009;41:25-33. ing exercise 5 minutes a day with 5 minute increments every week Busoni V, et al. Magnetic resonance imaging findings in the until reaching 25-30 minutes at which time walking exercise under equine deep digital flexor tendon and distal sesamoid bone in saddle followed by trot work is instituted. The navicular bursa is advanced navicular disease--an ex vivo study. Vet Radiol Ultrasound typically injected with Polyglycan® (2.5 mls) 2 and 6 weeks following 2005 46(4):279-86. surgery. In cases where either articular erosions or significant Bolen G, et al. Sonographic anatomy of the palmarodistal aspect inflammation/edema are identified, the horse is treated with of the equine digit. Vet Radiol Ultrasound 2007;48(3):270-5. Tildren® given once intravenously (500 mg) either immediately Dakin SG, et al. Osseous abnormalities associated with collateral before or following surgery, and again 4 months later. As the horse desmopathy of the distal interphalangeal joint: Part 1. Equine Vet J re-enters more active controlled exercise, the degree of the heel 2009; 41(8): 786-793. wedge is reduced by 1 degree (usually every 5-6 weeks) until Murray RC, et al. Magnetic resonance imaging characteristics reaching 2 degrees. Other treatments include the use of IM of the foot in horses with palmar foot pain and control horses. Adequan® (500 mg [1 vial] given IM once every 4 days for 7 Vet Radiol Ultrasound 2006; 47(1):1-16. treatments) or oral nutraceuticals. Follow-up examinations Sherlock C. Deep Erosions of the palmar aspect of the navicular including ultrasound examinations are typically performed every bone diagnosed by standing magnetic resonance imaging. Equine Vet 6-8 weeks. Based on these, the exercise protocol is modified. J 2008;40(7):684-692. Return to full exercise is dependent on the degree of the injury but Smith MRW, Wright IM, and Smith RKW. Endoscopic assess- typically a minimum of 4-6 months is required. ment and treatment of lesions of the deep digital flexor tendon in the navicular bursae of 20 lame horses. Equine Vet J 2007;39:18-24. REFERENCES Sage AM and Turner TA. Ultrasonography of the soft tissue Dabareiner RM, Carter GK, and Honnas CM. Injection of structures of the equine foot. Equine Vet Ed 2002; 14(4): 221-224. corticosteroids, hyaluronate, and amikacin into the navicular bursa Bell CD, et al. Outcomes of podotrochlear (navicular) bursa in horses with signs of navicular area pain unresponsive to other injections for signs of foot pain in horses evaluated via magnetic treatments: 25 cases (1999-2002). J Am Vet Med Assoc resonance imaging: 23 cases (2005-2007). J Am Vet Med Assoc 2003;223(10):1469-1474. 2009;234(7):920-925. Stashak TS. Adams’ lameness in horses. 1987. 4th edition Spriet M, David F, and Rossier Y. Ultrasonographic control of (Philadelphia: Lea and Febiger):499-514. navicular bursa injection. Equine Vet J 2004;36:637-639. Grewal JS, et al. Assessment of the ultrasonographic characteris- Pauwels FE, et al. Evaluation of the diffusion of corticosteroids tics of the podotrochlear apparatus in clinically normal horses and between the distal interphalangeal joint and navicular bursa in horses with navicular syndrome. J Am Vet Med Assoc horses. Am J Vet Res 2008; 69(5):611-616. 2004;225(12):1881-8. Wright IM, Phillips TJ, Walmsley JP. Endoscopy of the Dyson S, et al. Magnetic resonance imaging of the equine foot: navicular bursa; a new tequnique for treatment of contaminated 15 horses. Equine Vet J 2003;35(1):18-26. and septic bursae. Equine Vet J 1999; 31: 5-11. Dyson SJ, Murray R, and Schramme MC. Lameness associated Cruz AM, et al. Podotrochlear Bursa Endoscopy in the Horse: with foot pain: results of magnetic resonance imaging in 199 horses A Cadaver Study. Vet Surg 2001;30(6):539-545. (January 2001 - December 2003) and response to treatment. Equine Rossignol F and Perrin R. Tenoscopy of the navicular bursa: Vet J 2005;37(2):113-121. Endoscopic approach and anatomy. J Equine Vet Science Busoni V and Denoix JM. Ultrasonography of the podotrochlear 2003;23(6):258-265. apparatus in the horse using a transcuneal approach: technique and Smith MRW, Wright IM. Endoscopic evaluation of the navicu- reference images. Vet Radiol Ultrasound 2001;42(6):534-540. lar bursa: Observations, treatment and outcome in 92 cases with Dyson S. and Murray R. Magnetic resonance imaging evalua- identified pathology. Equine Vet J 2012; 44: 339-345. tion of 264 horses with foot pain: the podotrochlear apparatus, deep digital flexor tendon and collateral ligaments of the distal interphalangeal joint. Equine Vet J 2007; 39(4):340-3.

26 www.theneaep.com 585-205-5122 THE CLINICIAN OCTOBER 2020 NEAEP

The Latest on Laminitis The equine industry is still learning about what causes laminitis, how to prevent it and how to treat it. Nancy S. Loving, DVM

LAMINITIS RESEARCH continues to progress as laminitis and support limb laminitis result primarily from loss of clinicians pursue efforts to prevent and manage this insidious and cell adhesion of the hemidesmosome and desmosomes. painful syndrome. Recently, a new paradigm for looking at Research (pursued at the Belknap laboratory at The Ohio State laminitis was presented by Cathy McGowan, BVSc, MACVSc, University’s veterinary medicine department) has identified a DEIM, Dip ECEIM, PhD, FHEA, FRCVS, of the Equine Sciences problem at the level of the mTOR signaling pathway that is Department at the University at Liverpool. Her pioneering research important to cell growth and homeostasis, as it regulates epitheli- into endocrinopathic laminitis has yielded invaluable information al-mesenchymal transition (EMT). Regardless of the inciting cause that elucidates a different pathologic process than previously of laminitis, alterations in mTOR signaling and resultant changes in considered. EMT integrity occur in all three forms of laminitis. Structural Historically, it has been thought that laminitis pathophysiology failure of the lamellar cytoskeleton and interference with cellular falls into one “bucket” of pathological changes primarily related to energy metabolism are consequences of abnormal mTOR signaling. ischemia. This is no longer the case. In fact, now it is considered Similar aberrations in the MTOR signaling system also play an that there are three distinct pathways to the development of important role in the pathophysiology of cancer and diabetes. laminitis: 1. endocrinopathic laminitis (EL) ENDOCRINOPATHIC LAMINITIS 2. sepsis-associated laminitis (SAL) Endocrinopathic laminitis is linked to obesity, insulin dysregu- 3. support limb laminitis (SLL) lation, pasture-associated laminitis, equine metabolic syndrome, pars pituitary intermedia dysfunction (PPID) and/or administra- A presentation at the 2019 Northeast Association of Equine tion of glucocorticoids. Roughly 90% of laminitis cases are due to Practitioner’s Symposium by Andrew van Eps, BVSC, PhD, these types of metabolic derangements. DACVIM, of University of Pennsylvania’s School of Veterinary While laminitis from sepsis is associated with acute lamellar Medicine, outlined distinct differences and similarities between inflammation and adhesion failure, that is not the case with these forms of laminitis. endocrinopathic laminitis that occurs more slowly—some horses All three forms result from injury to, and ultimate failure of, demonstrate hoof wall ridging or changes in the sole and white line lamellar epithelial cells that result in either lamellar epithelial months before a full-blown laminitic attack. The delay in develop- stretching and/or failure of epithelial cell adhesions between cells ment of overt laminitis signs might be due to intermittent and and their dermal connections with the basement membrane. While transient hyperinsulinemia based on endocrine triggers, as well as all these cellular disruptions can occur in any case of laminitis, each ingestion of diets that include soluble carbohydrates such as grains of the three pathways has a predominant pathological footprint. or rich pasture. Endocrinopathic laminitis develops mostly due to cellular Hyperinsulinemia is an inciting cause of lamellar stretch. stretch from disruption of the cytoskeleton. Sepsis- associated Excessive insulin overstimulates growth factor receptor IGF-1R that

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6424 Clinician Trade Ad .indd 1 9/15/20 10:56 AM THE CLINICIAN OCTOBER 2020

then triggers a proliferative response in lamellar epidermal cells. supporting limb laminitis, but it does not seem to play a role in the The result is disruption of normal cell adhesions. (Excess activity of other two forms of laminitis. this growth factor, mediated by mTOR, also alters EMT in epithelial cancers.) TREATMENT APPROACHES TO LAMINITIS SEPSIS-ASSOCIATED LAMINITIS The more quickly a horse is recognized at risk of laminitis or in (SAL) the throes of the disease, the better the possibility of arresting Roughly 12% of laminitis cases result from systemic inflamma- progression of lamellar injury. As much as possible, prevention is tion, particularly when bacteria and endotoxemia are involved as key. If that didn’t occur, then early intervention is important to occurs with metritis, pneumonia, colitis and enteritis. Endotoxin is control inflammation and to limit further mechanical damage. In considered an important risk factor and trigger in these cases. all active cases of laminitis, movement restriction is important Sepsis can result in dysfunction in multiple organs, with through stall confinement supplied with comfortable bedding. laminitis one form of organ dysfunction. For horses with sepsis-associated laminitis, the goal is to Features of human cases—circulatory derangements, local reverse and control the primary disease problem, whether it be inflammation, apoptosis and non-ischemic derangement of cellular gastrointestinal disease, metritis, pneumonia or grain overload. energy metabolism— have been investigated in the horse. Strategies include intravenous circulatory support, binding of Local inflammation involves cytokines and leukotriene (IL-6) endotoxin with polymyxin B and hyperimmune plasma, inflamma- activation that are often implicated in systemic inflammation. tion control with NSAIDs and attention to cooling of the hooves Matrix metalloproteinases that degrade the extracellular matrix with cryotherapy. have a secondary role in disrupting lamellar integrity. It is also The feet should be cooled to temperatures below 50 degrees possible that dysregulation or failure of oxidative energy metabo- Fahrenheit using ice baths or boots, if possible. Cooling is best lism in SAL can elicit adhesion failure in lamellar epithelial cells. accomplished by immersing the limbs from the mid-cannon to the bottom of the hooves in an ice bath or cooling boot. Sole support is SUPPORTING LIMB LAMINITIS critical when the feet aren’t being iced—appropriate hoof trimming, special orthotic support (SLL) (Soft-Ride boots, as one example) or the Supporting limb laminitis is a risk factor in a horse that is use of deep sand are greatly helpful non-weight-bearing on one limb due to an extremely painful to support internal hoof struc- orthopedic injury or fracture repair. Supporting limb laminitis is tures as well as for improving a estimated to occur in 10-15% of horses with significant orthopedic horse’s comfort. conditions. One suggested mechanism for why laminitis occurs in Endocrinopathic the contralateral limb from the injury is explained as an increase in laminitis is best managed load created by a horse standing full time on a single front or rear with early intervention to limb; lamellar epidermal remodeling might occur in response to control obesity and body this mechanical stress. condition through dietary In addition, a horse’s constant stance of full weight on the strategies and exercise, supporting limb obviates the normal cyclic limb loading that is preferably before a horse critical for normal blood circulation and energy provision to becomes lame. the lamellae. Screening tests of insulin Normally, nutrients and oxygen are delivered to the lamellar and ACTH can help to identify dermis through the blood during cyclic loading as a horse weights horses with insulin dysregulation and unweights a limb by shifting weight at rest or by walking. and/or PPID. Without this cyclic loading, lamellar tissues might be deprived of Pasture should be eliminated while also glucose that is important energy to maintain the lamellar cytoskele- controlling the amount and type of food offered by ton and epithelial adhesions. Ischemia can further contribute to

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limiting concentration of non-structural carbohydrates to less than Prevention or control of supporting limb laminitis relies on 10%. Soaking hay and pouring off the supernatant removes as enabling a horse to comfortably weight the injured limb enough much sugar as possible before feeding. that the support limb receives a necessary amount of cyclic loading The use of slow feeders or nibble nets allows a horse to from shifting of weight and walking steps. consume its dietary portions less quickly and more closely resem- In some cases, the use of sling support might help to relieve the bles “grazing.” Exercise programs are important not only to whittle mechanical stress on the lamellae of the supporting limb. away overweight pounds but also because exercise improves Appropriate analgesia improves comfort and facilitates insulin sensitivity. reasonable use of an injured limb to better normalize limb weight Cryotherapy is also recommended for active cases of endocr- distribution. inopathic laminitis to alter progression of an acute laminitis flare. Cases that are refractory to strict dietary control measures TAKE-HOME MESSAGE might need further help to reduce body weight by using medica- The veterinary industry is still learning about what causes tions like metformin and thyroid supplementation. Horses with laminitis, how to prevent it and how to treat it. PPID respond well to daily treatment with pergolide. Ongoing research should help practitioners and horse owners Investigation is ongoing on the use of veglagliflozen to learn more about the various causes of laminitis and hopefully offer counteract insulin dysfunction by reducing reabsorption of glucose prevention and treatments that can help bring horses back to full by the kidneys and increasing excretion of glucose through the function. urinary tract.

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NEAEP_theclinicialmag_Fullpg_20201005_2.indd 1 05/10/2020 13:02 THE CLINICIAN OCTOBER 2020 NEAEP

The Use and Application of the Wooden Shoe An alternative to traditional farriery Jeff Ridley, APF, CJF, TE

INTRODUCTION phalanx recognized are: dorsal capsular rotation, distal displace- The wooden shoe has become a viable option for treating ment (sinking) medial or lateral displacement of the distal phalanx 3 many foot problems including acute and chronic laminitis, white or any combination of the above . The most common type of line disease, distal phalanx fractures and a method to promote sole displacement encountered is dorsal capsular rotation. If dorsal depth in horses with thin soles. This device is most often used to capsular rotation is severe, the instability of the distal phalanx treat chronic laminitis, so chronic laminitis will be considered here combined with the weight of the horse often leads to prolapse of the to illustrate the use of this treatment option. Chronic laminitis is a sole or penetration of the distal phalanx through the sole. The frustrating and often disheartening disease for veterinarians, wooden shoe has become another farriery option that has been farriers and horse owners to manage. Our ability to rehabilitate found to be a consistently successful method to address dorsal horses with laminitis, despite the type of farriery employed, is capsular rotation (Fig.1). related to the severity of damage to the lamellae 1, 2. For this reason, The wooden shoe accompanied by the appropriate trim allows treatment failures with any given methodology are commonplace. the distal phalanx to be realigned, has all the mechanical compo- Chronic laminitis is defined by the presence of mechanical collapse nents of other farriery systems previously advocated for the of the lamellae and displacement of the distal phalanx within the treatment of chronic laminitis yet may possess many additional hoof capsule 1. The various forms of displacement of the distal advantages over previous methods used.

Advantages are: l readily accessible materials l simplicity of construction l mechanics such as breakover and heel elevation can be fabricated into the shoe l beveled perimeter of the shoe concentrates the load under the distal phalanx l solid base of shoe allows maximum recruitment of surface area in the palmar / plantar section of the foot to accept load l solid base combined with an appropriate Silastic material places even pressure and load across the palmar / plantar section of the foot Fig.1. A wooden shoe attached to a hoof model. Note the mechanics l heel elevation, when necessary, can be applied incorporated in the shoe - beveled perimeter of the shoe for in a uniform manner lateral / medial breakover, extended dorsal to palmar breakover l easily altered according to the radiographic guidelines and and heel elevation. structural requirements of individual foot conformation l non-traumatic application 33 www.theneaep.com 585-205-5122 THE CLINICIAN OCTOBER 2020

The application process of the wooden shoe is one of the main the lever arm effects of a shoe in all directions around the foot. A 30 advantages when we look at the non-traumatic fashion in which it is degree angle is used in the heel area as this provides stability when applied in comparison to a horseshoe nailed to the bottom of the the foot strikes the ground. horse’s foot. This factor should always be considered when working A thin layer of wood glue is applied between the 1/4” or 3/8 on a sore, laminitic horse. From the above, it can be noted that the plywood and the 3/4” plywood and the two pieces are secured in wooden shoe offers the veterinarian and farrier an alternative farriery place with a couple of 1 inch drywall screws. option when confronted with a variety of debilitating lameness issues. There are limitations using a steel shoe as the thickness of the The wooden shoe offers the farrier many biomechanical options steel prevents making sufficient biomechanical changes to be otherwise not available using traditional horseshoes. The flexibility of beneficial when significant rotation is present, for example, when being able change the biomechanics such as moving break over and using a 5/16 inch steel shoe, one can only grind break over so far changing the center of pressure can easily be altered by the thickness before you are simply grinding a flat surface on the toe of the shoe. of the wooden shoe and how it is positioned on the foot. The ease of However with the wooden shoe, the thicker the wood, the farther working with wood allows the farrier to readily manipulate modifica- you can move break over in a palmar direction to correspond with tions both prior to the application of the wooden shoe as well as after the amount of rotation (Fig.2&3) the device has been applied to the foot. The farriery goal of treating chronic laminitis is realignment of the distal phalanx with the ground THE TRIM 5,6 surface of the foot . When applying the wooden shoe, it is essential to use a radiograph as a template8. Dorsal/palmer (DP) radiographs, along CONSTRUCTION OF THE with lateral radiographs are essential to determine the position/ WOODEN SHOE displacement of the distal phalanx within the hoof capsule8. The The wooden shoe is relatively simple to construct using a foot is trimmed using the widest part of the foot as this is a couple different thicknesses of plywood, 3/4” and ¼ / 3/8”, some landmark for the center of rotation that can be transferred from the wood glue and a couple of drywall screws. Using a shoe with a radiograph. The trim begins with a line being drawn across the broad toe as a pattern, the wooden shoe can be cut in several widest part of the foot. Any exfoliating horn is removed from the different sizes using a angle saw or it can be cut out with a straight frog and the heels are trimmed from the line to the point where the saw and then modified using carpentry or farrier tools to incorpo- hoof wall at the heels and the frog are on the same plane. This alone rate the appropriate bevel. The 45 degree bevel around the perime- increases the ground surface in the heel area and thus the ability to ter of the shoe helps negate ground reaction forces exerted on the accept load. If the foot can be trimmed to coincide with the line perimeter of the hoof wall and hence the lamellae. When the outer drawn parallel to the solar surface of the distal phalanx, the palmar edge of the wooden shoe is beveled under the foot this minimizes aspect of the ground surface of the foot will be on a different plane

Fig. 2&3 The wooden shoe vs the steel heartbar shoe.

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to the dorsal aspect of the ground surface which will often unload frog has receded. Additional impression material is placed against the dorsal section of the foot. The dorsal hoof wall is trimmed to the bulbs of the heels to act as cast padding when fiberglass casting parallel the parietal surface of the distal phalanx using the angle of material is applied around the perimeter of the hoof. The shoe is growth at the coronet as a guideline. This will generally create a held in the proper position with one hand placed at the toe, the foot more acceptable alignment between the dorsal hoof wall and the is brought forward into the clinching stance and the 3 pre-started parietal surface of the distal phalanx. screws are driven through the hoofwall into the wooden shoe to secure it in place. Once the wooden shoe is secured, the foot is FITTING THE SHOE placed on the ground to disperse the impression material evenly A wooden shoe is then fitted to the trimmed foot. The foot under the shoe.. The remaining drywall screws are applied to each surface of the shoe should be fit slightly wider then the perimeter of side of the foot for further security; generally placing 3 screws per the trimmed foot. Additionaly, the shoe needs to extend .5 - 1 cm side. Additional screws are placed next to the hoofwall, on both beyond the end of the heel to form a heel base to support the sides of the foot beyond the last screw used to attach the wooden palmar section of the foot. The heel base is fitted somewhat full at shoe. These screws act as struts which will provide increased the heels not only to increase the ground surface of the shoe but to stability when they are incorporated into the casting tape. accept screws placed against the hoof wall to act as struts (Fig.4). A straight edge (such as a rasp) is held in a vertical manner against the side of the hoof, dorsal to the leading edge of the coronet and a mark is placed on the shoe at the distal end of the vertical line. This line is used as a guide where breakover should occur which is slightly dorsal to the margin of the distal phalanx (Fig.5).

Fig.4 wooden shoe fit appropriately to accommodate struts and cast padding.

APPLICATION METHOD Holes are pre-drilled in the horse’s foot to create a tract that Fig.#5 Establishing where breakover needs to be. ensures the appropriate placement of the screws. A motorized tool and a 3/64 drill bit are used to pre-drill holes in the palmar half of the hoof starting in the white line and going proximally…exiting 2-inch fiberglass casting tape is applied around the foot with the hoof wall the same height as a horseshoe nail. The foot is placed half of the casting material encompassing the distal hoofwall, on the ground and a minimum of 3 screws (2 lateral and 1 medial) including the struts while the other half is to encompass the are started in the pre-drilled holes in the hoof wall. wooden shoe. This application process further secures the shoe in Having the foot and shoe properly prepared, the shoe is now place and offers the hoofwall circumferential stability (Fig.6). ready to be applied. Impression material is placed in the palmar section of the foot filling the sulci of the frog and any area where the

36 www.theneaep.com 585-205-5122 THE CLINICIAN OCTOBER 2020

lateral rotation or white line disease, allowing one to shift the load to a more stable portion of the foot, minimizing the forces placed upon the compromised area of the foot8,9. Recognizing that there is no replacement for traditional farriery and the foundation upon which it is built , the use of the wooden shoe is a viable farriery option and the temporary therapeutic application of this device to help a horse is should always be considered.

References 1. Hood, D.M. (1999) The mechanisms and consequences of structural failure of the foot. In: Hood, DW, ed. The veterinary clinics of North America, vol. 15:2. Philadelphia: W.B. Saunders. pp 437-461. 2. Hunt, R. J. (1998) Chronic Laminitis In: White NA and Fig.6 Casting material provides circumferential stability Moore JN, ed. Current techniques in equine surgery and lameness. to the hoof wall. 2nd ed. Philadelphia: WB Saunders. pp 548-552. 3. O’Grady, S.E., Steward, M., Parks, A.H. (2007a) How to ADDITIONAL MODIFICATIONS Construct and Apply the Wooden Shoe for treating Three Manifesta- tions of Chronic Laminitis. Proceedings. Amer. Assoc of Equine Wooden shoes further offer the farrier certain modifications Practnrs. 53, 423-429. not able to be incorporated in a traditional horseshoe. An example 4. Parks, A.H., O’Grady, S.E. (2008) Chronic Laminitis. In: would be a laminitic horse’s foot that becomes convex rather than Robinson, NE, and Sprayberry, K. ed. Current Therapy in Equine being concave as a result of rotation. A traditional steel shoe is Medicine. vol 6. St. Louis: W. B. Saunders. pp 561-580. difficult to use due to the convexity and the unlikelihood of being 5. O’Grady, S.E. (2006) Realignment of P3 – the basis for treating able to apply the shoe without creating sole pressure. However, a chronic laminitis. Equine Vet Edu. 8, 272-276. trough can be ground into the foot surface of the shoe to accommo- 6. Parks, A.H. (2003) Chronic Laminitis. In: Robinson NE, ed. date the convexity. This modification allows the farrier to decrease Current Therapy in Equine Medicine. vol 5. St. Louis: W. B. force and protect the area of the foot that is most compromised. Saunders. pp 520-528. Success with the wooden shoe is dependent on the alignment 7. Parks, A.H., O’Grady, S. E. (2003) Chronic laminitis: current of the digit and location of the distal phalanx (P3) within the hoof treatment strategies. In: O’Grady SE, ed. The veterinary clinics of capsule. Trimming the heels in an attempt to realign the distal North America, vol. 19:2. Philadelphia: W. B. Saunders. pp 393-416. phalanx will often place increased tension on the deep digital flexor 8. Steward, M.L. (2003) How to Construct and Apply Atraumat- tendon DDFT. The addition of wedges may be added to the wooden ic Therapeutic Shoes to Treat Acute or Chronic Laminitis in the shoe to decrease the stresses on the DDFT on horses that have Horse. Proceedings. Amer. Assoc of Equine Practnrs. 49, 337-346. significant tension on the DDFT after realigning the solar margin 9. O’Grady, S.E, Steward M.L. The Wooden shoe as an option of the distal phalanx. for treating chronic laminitis. Equine Vet Edu 2009;8:272-276. The wooden shoe placement on the foot can be used to change the forces on the foot and is useful on horses that have medial/

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