Angular Limb Deformities in Foals: Treatment and Prognosis*

Home , Angular limb deformity, Valgus deformity, Varus deformity

Article #4 CE Angular Limb Deformities in Foals: Treatment and Prognosis*

Nicolai Jansson, DVM, PhD, DECVS Skara Equine Hospital Skara, Sweden

Norm G. Ducharme, DVM, MSc, DACVS Cornell University

ABSTRACT: This article presents an overview of the clinical management of foals with angular limb deformities. Both conservative and surgical treatment options exist; the choice of which to use should be based on the type, severity, and location of the deformity as well as the age of the foal. Conservative measures include controlled exercise, rigid external limb support, and corrective hoof trimming. Surgical treatment modalities comprise techniques for manipulating physeal growth and, after physeal closure, various corrective osteotomy or ostectomy methods. The prognosis is generally good if treatment is initi- ated well in advance of physeal closure.

ngular limb deformities and their treat- Conservative Treatment ment in foals and young horses constitute In most foals born with mild to moderate a significant part of the orthopedic prob- angular deformities, spontaneous resolution A 2 lems that veterinarians must manage. This article occurs within the first 2 to 4 weeks of life. In discusses the clinical management and prognosis newborn foals, periarticular laxity is the most of these postural deformities. likely cause, and these foals require no special treatment other than a short period of con- TREATMENT trolled exercise. In our opinion, mildly and The absence of controlled studies has moderately affected foals should not be confined impaired the accumulation of scientific data to a stall because exercise is important for nor- guiding the management of angular limb defor- mal muscular development and resolution of the mities in foals (Table 1). The following man- angular deformity. The opposite treatment (i.e., agement recommendations are based on the unlimited exercise) often leads to fatigue, which literature and our experience in treating foals exacerbates the deformity. Therefore, we suggest with angular limb deformities. Also, we use the that the mare and foal be placed in a small pad- terms mild, moderate, and severe angular defor- dock (e.g., 15 × 15 m). Alternatively, the mare mities, which are defined as less than 10˚, 10˚ to and foal may be kept in a large stall (e.g., 5 × 3 20˚, and greater than 20˚, m) and allowed frequent access to a small pad- Send comments/questions via email respectively.1 dock for a few hours at a time to prevent exces- [email protected], *A companion article on cause sive fatigue. There is a lack of scientific data fax 800-556-3288, or web and diagnosis appeared in the documenting how much confinement these CompendiumVet.com January 2005 issue (p. 48). foals need, and these recommendations are

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Table 1. Treatment Modalities for Foals with Angular Limb Deformities Treatment Modality Angular Limb Deformity Stall and/or small paddock rest All types Rigid external support to the limb (e.g., splint Periarticular laxity bandage or tube cast) Cuboidal bone hypoplasia Hypoplasia of the proximal aspect of the fourth metacarpal bone Corrective hoof measures (e.g., trimming, Deformities originating in a long bone before cessation of physeal shoeing) growth Surgical manipulation of physeal growth (growth Deformities originating in a long bone before cessation of physeal acceleration and/or growth retardation techniques) growth Corrective ostectomy or osteotomy Deformities originating in a long bone after cessation of physeal growth based only on our experience. that is bent to follow the dorsal contour of the limb.2 Foals with severe periarticular laxity and grave angular For splint bandaging, the foal should be sedated and lat- deformities are unlikely to experience spontaneous cor- erally recumbent. After this, the deformity can be man- rection.2 These foals often need some form of external ually corrected and the splint applied to the limb.a support to straighten the limb in addition to stall and Splint bandages should be changed at least every 3 to 4 small paddock rest. A splint bandage or tube cast (i.e., a days to check for skin pressure sores.3 However, a cast that does not enclose the foot and fetlock) can be shorter bandage change interval is preferred. applied to keep the limb straight and allow the periar- In our experience, managing splint bandages is prob- ticular tissues and collateral ligaments to strengthen lematic on many farms because of the help necessary in within 2 to 4 weeks.2–4 By not incorporating the foot, a placing a splint: someone to hold the mare, someone to splint bandage or tube cast allows weightbearing, thus restrain the foal, and someone to apply the splint. The preventing muscular atrophy and worsening of the con- labor required for splint application competes with the

Confinement to reduce axial compressive forces on the affected limb is an important part of managing angular limb deformities in foals. dition. However, treatment of periarticular laxity by demands of a breeding farm during the breeding season. rigid external support has been debated and, according To minimize these labor concerns, we have used snap-on to one author, may actually delay strengthening of the splints or tube casting. The snap-on splint is custom- periarticular structures.5 Because periarticular laxity made from padded fiberglass (Endurasplint 2, Carapace most often affects the carpus or tarsus, the splint band- Inc., New Tazewell, TN; Figure 1). These splints have age or cast should extend from the proximal radius or enough strength for foals younger than 6 weeks of age. tibia to just above the fetlock joint. We use a transected The foal should be sedated and laterally recumbent. A polyvinylchloride pipe to create a hemispherical splint rectal sleeve should be placed over the limb to be that can be applied to the palmar aspect of the forelimb splinted to protect it from contact with water and over roll cotton padding regardless of whether a valgus polyurethane resin. The splint should be immersed in or varus deformity is being treated. water at a temperature of 69.8˚F to 73.4˚F (21˚C to Because of the anatomy of the hindlimb, tarsal defor- aAuer JA: Personal communication, University of Zurich, mities can be best stabilized by applying a dorsal splint Switzerland, 2003.

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Figure 2. Radiograph of the right carpus of a 1-day-old mixed-breed foal with carpal valgus caused by carpal bone hypoplasia.

Figure 1. Endurasplint (Carapace Inc., New Tazewell, TN) is made of padded fiberglass and has the advantage of being molded to follow the contour of the limb, thereby reducing the risk of skin pressure sores. Note the rounded and The foal was treated with incompletely ossified carpal external support to the limb, bones as well as the which allowed the carpal bones 23˚C), and excess water should subsequently be squeezed hypoplastic proximal aspect of and the proximal aspect of the the fourth metacarpal bone fourth metacarpal bone to out. The splint should be applied to the limb so that the contributing to the valgus ossify under even loading as felt is against the skin and half of the circumference of deformity. seen on this radiograph taken the limb is covered. It should then be secured to the limb 3 weeks later. (Courtesy of Dr. with gauze and allowed to dry sufficiently to hold its Tony Pease, Cornell University, shape. The splint should be removed and allowed to set Ithaca, NY) for 5 to 7 minutes before reapplying it to the limb. Because the splint is padded and molded to the contour of the limb, it should be easy to place and only a single shells immediately following application.7 The shells may roll of self-adhesive elastic bandage should be needed to then be removed every 3 to 4 days to evaluate the skin.8 secure it, making it convenient for daily use. In a hospital It should be noted that foals cope with rigid uni- or setting, we recommend leaving the splint on for 12 hours bilateral forelimb bandages or unilateral hindlimb band- at a time to prevent pressure sores; the splint should be ages without difficulty, whereas they need help rising if applied at night while the foal is less active. both hindlimbs require rigid external support.4 Another means of establishing external support to a In foals born with angular deformities associated with limb is application of a tube cast, which is best done with cuboidal bone hypoplasia of the carpus and/or tarsus, the patient under general anesthesia.4,6 Casts should be treatment should be directed toward maintaining normal changed at 10- to 14-day intervals to allow rapid growth alignment of the affected limb and allowing the carti- of young foals.6,7 The main disadvantage of tube casting laginous templates to ossify under even loading4–6,8,9 (Fig- is the risk of developing skin pressure necrosis; this can ure 2). Except for very mild cases (<7˚), untreated foals be somewhat reduced by cutting the cast into two half are at risk of developing permanent angular limb defor-

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Orthotics We have treated a select number of weanlings with angular deformities using orthotic devices (orthoses). Orthotics is the science that focuses on the design, manufacturing, application, and evaluation of orthotic devices to assist in patient ambulation and correction of various skeletal deformities. Using orthotic devices in children is well established and recommended for a variety of pediatric conditions.a–c In veterinary medicine, the use of orthotic devices has been extremely limited (excluding corrective shoeing and the standard splints and casts described in this article). Use of an ankle–foot orthosis in a dog with traumatic sciatic neuropathy has been reported.d The orthotic devices that we have used are custom-made to a given limb of a weanling. A mold is first made using a roll of cast material over a stockinette to reproduce for the orthotist the relevant portion of the limb. The cast is cut and removed so that the custom-made device can be constructed to fit the limb of the animal. To treat angular deformities, a stabilizing stainless-steel bar should be placed on the concave side of the deformity and pressure applied on A. Weanling with carpal valgus and external rotation the convex side to help correct it (A). The foal should of the right forelimb. The brace should be secured over wear the device for progressively longer periods up to 12 the midradius and mid-third metacarpal bone. Note the hr/day. The device should be removed at night. Further stabilizing bar on the concave side (lateral aspect) of the limb. investigation into this technology is required before its A hinge centered over the pivot point allows normal range of value and potential can be fully assessed. flexion of the carpus.

aGenaze RR: Pronation: The orthotist’s view. Clin Podiatr Med Surg 17:481–503, 2000. bVankoski SJ, Michaud S, Dias L: External tibial torsion and the effectiveness of the solid ankle-foot orthoses. J Pediatr Orthop 20:349–355, 2000. cWoolam PJ, Lomas B, Stallard J: A reciprocal walking orthosis hip joint for young paediatric patients with a variety of pathological conditions. Prosthet Orthot Int 25:47–52, 2001. d Levine JM, Fitch RB: Use of an ankle-foot orthosis in a dog with traumatic sciatic neuropathy. J Small Anim Pract 44:236–238, 2003. mity due to ossification of the cuboidal bones in a seal or epiphyseal growth usually develop between 2 wedge-shaped or collapsed configuration.2,3,7 It is there- weeks and 6 months of age; foals are rarely born with fore very important that these foals be identified early this type of angular deformity. These foals should not be and treated appropriately.2 In these foals, the required treated with external support because it almost invari- treatment includes confinement and external support of ably results in skin pressure sores without correction of the limb. The external support may be in the form of the deformity.3–5 Mild deformities often respond well to splint bandages or tube casts as previously discussed. stall or small paddock rest, whereas moderately affected Radiographs should be obtained at 14-day intervals to foals need additional treatment in the form of corrective determine the degree of cuboidal bone ossification.3 hoof trimming and, possibly, application of glue-on External support should be maintained until the ossifica- shoes.11,12 Confinement reduces the axial compressive tion process is complete, which normally takes 2 to 4 forces acting on the physeal and epiphyseal growth car- weeks. In some foals, it may take up to 2 months, which tilage, possibly correcting deformity by stimulating lon- stresses the importance of repeated radiographic evalua- gitudinal growth on the concave side of the limb.10 tions.3 Foals with incomplete ossification of the proximal Contrary to this, excessive compressive forces as a result aspect of the fourth metacarpal bone should be treated in of free pasture exercise reduce longitudinal growth on the same way as foals with cuboidal bone hypoplasia.10 the concave side. Free exercise may therefore delay cor- Angular limb deformities caused by asymmetric phy- rection or even cause the deformity to worsen.6

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Table 2. Period of Rapid Growth and Age Table 3. Age Limit Recommendations at Radiographic Closure of Some Growth (for Optimal Results) for Correcting Plates in Horses6 Angular Limb Deformities by Surgically Manipulating Physeal Growth Age at Growth Period of Radiographic Technique and Plate Rapid Growth Physeal Closure Growth Plate Age Limit (mo) Distal radial 0–8 mo 22–36 mo Distal radial HCPTE: 4 TPB: 12 Distal tibial 0–6 mo 17–24 mo Distal tibial HCPTE: 4 Distal metacarpal/ 0–100 days 6–15 mo TPB: 10 metatarsal Distal metacarpal/metatarsal HCPTE: 2 TPB: 3 To further correct the deformity, the high side of the HCPTE = hemicircumferential periosteal transection and elevation; = transphyseal bridging. hoof wall can be frequently trimmed so that the foot is TPB level.3,7,13 The aim of hoof trimming is to correct the concurrent rotational deformity. In foals with valgus deformities, this is done by slightly rasping the outside hoof wall, experience, the described methods for trimming and which causes the inside hoof wall to contact the ground shoeing, if used judiciously and with frequent monitor- first during ambulation, thereby causing slight inward ing, can be applied with success. rotation of the foot.3 Correspondingly, the inside hoof Alternatively, trimming and shoeing to correct carpal wall should be lowered in foals with varus deformities.3 and tarsal deformities could be done after closure of the The effect of corrective hoof trimming may be in- distal metacarpal or metatarsal growth plate. It is creased by placing a glue-on shoe with extension to the important not to extend the period of corrective trim- inside in foals with valgus deformities (outside in foals ming and shoeing for too long. Also, we recommend with varus deformities).3,11,12 As an alternative to glue-on that glue-on shoes not be left on for longer than 2 shoes, an extension can be molded directly onto the weeks to avoid development of a contracted foot. At hoof using acrylic (minimal or nonhyperthermic poly- least 7 to 10 days of growth should be allowed to pass

Both conservative and surgical treatment options are available for managing angular limb deformities in foals. mers should be used to prevent hoof damage); we do before resetting the shoes. If confinement and, possibly, not feel that this is as safe as glue-on shoes because trimming and shoeing have not resulted in significant more stress can be applied to the hoof laminae (by improvement of the deformity within 4 to 6 weeks, sur- building onto or molding the hoof wall), possibly tear- gical treatment should be attempted.3 ing a portion of the laminae. By forcing the foot into an abnormal position, corrective trimming and shoeing Surgical Treatment result in torsional forces that may influence joints and In severely affected foals or those in which an angular periarticular structures negatively and lead to concurrent limb deformity is unresponsive to restricted exercise angular deformities elsewhere.3,12 For example, a varus and, possibly, corrective trimming and shoeing, surgical deformity at the metacarpophalangeal joint could be treatment should be administered. The surgical tech- created during correction of a carpal valgus. Therefore, niques to correct angular limb deformities in foals can some authors do not recommend trimming and shoeing be divided into growth acceleration and retardation, the as outlined but prefer light rasping to balance the foot aim of which is to lead to correction by influencing the and ensure normal breakover instead.14 However, in our growth rate of the growth plate. Thus sufficient growth

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potential should remain and surgery should be performed well before the end of the rapid growth phase. Restricted exercise until the angular limb deformity is corrected is an important part of postoperative treatment. It is important to note that the period of rapid growth is different from the age at radiographic evidence of physeal closure6,15 (Table 2). The age limits for optimal results of surgical manipulation of physeal growth depend on the degree and location of the deformity.15 Recommendations regarding the optimal age for surgical treatment vary among authors.1,16,17 In general, for optimal postoperative results, deformities caused by asymmetric growth at the distal radial and distal tibial growth plates should be treated before 4 months of age, whereas deformities at the distal growth plate of the third metacarpal or metatarsal bones should be treated before 2 months of age (Table 3). These are only general guidelines because the degree of deformity greatly influences the possibility of surgical correction. The earlier surgery is performed, the faster correction occurs, which is often the rationale for choosing surgical treatment well before the end of the rapid growth phase.3 However, according to a recent experimental study18 in which angular deformities were created by abaxial growth-plate retardation, surgically induced growth acceleration was as effective in correcting carpal angular limb deformities as stall confinement alone. In that study, the cosmetic blemish left after surgery gave the visual impression that limbs that were operated on

Surgical manipulation of physeal growth depends on residual growth potential.

were straighter than control limbs, but radiographic comparisons showed there was no difference between limbs. Multiple conclusions can be extrap- olated from this study: Growth acceleration is of little value, and exercise restriction is effective in treating angular limb deformities. Since its introduction into equine surgery approximately 20 years ago,7,13,19 growth acceleration by hemicircumferential periosteal transection and elevation (HCPTE) has gained widespread acceptance as the standard surgical technique for correcting angular limb deformities.3,5,8,16,17,19–21 However, previous clinical studies all lacked a control group and merely relied on the degree of limb straightening as evidence of a positive effect of the proce- dure. This fact and the results of the experimental study already mentioned may change the interpretation of the value of HCPTE in the future. With the patient under general anesthesia, HCPTE should be performed on the concave aspect of the bone responsible for the deformity. A periosteal incision shaped like an inverted T should be made proximal to the affected growth plate followed by elevation of the periosteum to create two triangu- lar flaps (Figure 3). The periosteal incision and elevation stimulates longitudinal growth for approximately 2 months and can be repeated if correction is incomplete.3 Overcorrection of the deformity has not been reported with this technique. The exact mechanism by which HCPTE exerts its effect remains unknown. However, several mechanisms have been proposed,

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Figure 4. Postoperative radiograph showing a Figure 3. HCPTE is performed on the lateral aspect of transphyseal implant that has been placed across the the distal radial growth plate to correct carpal valgus. lateral aspect of the distal radial growth plate to treat a Note the inverted T-shaped periosteal incision.This surgery carpal varus. The implant temporarily slows longitudinal growth stimulates longitudinal growth on the lateral side of the growth on the lateral side of the growth plate, thereby correcting the plate and has an effect for up to 2 months. deformity.

including induction of mild metaphyseal ischemia, sionally have detectable thickening at the surgery site. removal of periosteal compression across the growth Growth retardation by temporary transphyseal bridg- plate, and creation of a so-called “internal splint” that ing (TPB) was once the surgical treatment of choice for braces the metaphyseal area and helps regulate its correcting angular limb deformities.24–27 Although there growth.22,23 are no controlled studies to document its effectiveness, Postoperative exercise restriction to reduce the axial there is little doubt that TPB is effective. The surgery is compressive forces on the growth plate is an integral performed with the patient under general anesthesia part of treatment. HCPTE results in a cosmetic blemish and entails placing a growth-restraining implant across that may increase in size up to 2 months after surgery the growth plate on the convex aspect of the bone (Fig- and then progressively remodel in the following months. ure 4). The implant temporarily arrests longitudinal The result is that the carpus in the vast majority of year- growth, allowing the concave aspect of the bone to con- lings that have undergone surgery bears no evidence of tinue to grow, which eventually corrects the deformity. this. In our experience, the cosmetic results at the The rate of correction following TPB has been re- metacarpo- or metatarsophalangeal joint are not quite as ported.28 In general, carpal deformities that are treated good, and yearlings that have had previous surgery occa- at 1 month of age can be expected to correct at a rate of

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Techniques for Temporary TPB remains an effective therapy in managing foals with Transphyseal Bridging angular limb deformities. TPB can be performed in young Stapling foals with severe angular deformities, miniature foals, or One or more Vitallium (Dentsply Austenal, York, PA) foals with significant limb deformity after the rapid growth 3 staples should be inserted, with the staple legs placed phase is over. In these cases, growth acceleration and retar- equidistant on each side of the growth plate. The staple dation techniques are often combined for faster and more legs should be parallel to the growth plate and the cross complete correction of the deformity. TPB can be success- member perpendicular to it. The staples should be ful in treating carpal or tarsal angular limb deformities in placed using special equipment (staple holder and growing horses 6 to 12 months of age. Similarly, the tech- driver). nique can be used to correct distal metacarpal or metatarsal deformities in foals 2 to 3 months of age. However, it is our Screws and wires clinical impression that many warmblood and draft horses A screw (cortex or fully threaded cancellous) should be may have a slower growth profile; thus surgery may be use- placed on each side of the growth plate. One or two ful even in slightly older foals. loops of 1.2-mm cerclage wire should be placed and tightened in a figure-of-eight pattern over the screw Foals with angulation of the third metacarpal or meta- heads. tarsal bone should first be treated with restricted exercise. If the deformity is severe or no improvement is seen Screws and a small bone plate in the first month of life, we perform periosteal stripping A 2.7-mm bone plate should be contoured to the shape on the concave side of the deformity. With the patient of the bone and placed perpendicular to the growth plate under general anesthesia, an I-shaped periosteal incision by a 3.5-mm cortex screw on each side of the growth is made and elevation is performed on the entire length plate. The screws should be inserted to produce of the angulated bone on the concave side. The hypothe- compression across the growth plate. sis is that if surgery is performed at a young age, the resulting periosteal reaction will be followed by a natural remodeling process that eventually leads to axial loading 0.4˚ to 0.5˚ per day, which successively decreases to 0.05˚ of the affected bone because of bone resorption on the to 0.1˚ per day at 100 days of age.6 The corresponding convex side and preservation of newly formed bone on improvements for metacarpo- or metatarsophalangeal the concave side. A similar principle has been applied to deformities are different from those just mentioned foals younger than 2 months of age with bench knee because of the relatively short growth phase of the distal conformation.29 In that study, bench knee conformation metacarpus or metatarsus: The rate of correction rapidly was corrected by a combination of HCPTE at the disto- declines from approximately 0.3˚ to 0.4˚ per day at 2 lateral aspect of the radius and an I-shaped periosteal weeks of age to 0.1˚ per day at 80 days of age.28 incision and elevation on the medial aspect of the third Three techniques for TPB have been described3 (see metacarpal bone. However, this approach has never been box above): evaluated in a controlled clinical study. Correction of angular limb deformities after cessation • Stapling of physeal growth necessitates a corrective ostectomy or • Application of two screws and cerclage wire osteotomy.30 Several types of corrective ostectomy and • Application of two screws and a small bone plate osteotomy techniques have been reported in the literature3 (box on p. 144). Because corrective ostectomy The main difference between these techniques and or osteotomy requires substantially more skill, experience, HCPTE is the need for a second surgery to remove the and equipment, is associated with a higher postoperative implant once correction has been achieved. Timing is risk rate, and is more expensive, the technique is usually important because delayed removal results in overcor- reserved for valuable animals with significant angular rection of the deformity (Figure 5). In addition, the cos- limb deformity after physeal closure. metic results are generally inferior to those after HCPTE. Although HCPTE has been regarded as the PROGNOSIS current standard surgical treatment, its popularity is Several studies have reported the response to both declining in light of recent studies. nonsurgical and surgical treatment of foals with angular

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Figure 5. Preoperative radiograph of the right carpus of a 5-month-old standardbred foal with carpal valgus.

The foal was treated using TPB on By 5 months after surgery, the foal had developed a carpal A concurrent radiograph showed the medial aspect of the distal varus. that the implant had resulted in radial growth plate. overcorrection of the valgus deformity.TPB implants must be removed once the deformity has been corrected.

limb deformities. One study reported that in 81.5% of deformities are not declared as such in yearling sales. A foals treated with HCTPE to correct angular deformi- study reporting the results of treatment in foals with ties, total limb straightening was achieved and 60% of tarsal valgus demonstrated that only 52.4% met the foals went on to be used at their intended performance expectations of their intended use, and these authors level.17 In a study that reported the results of transphy- concluded that foals with tarsal valgus have a poorer seal bridging, 80% of foals with carpal deformities and prognosis for future athletic use than do foals with 27.3% of foals with metacarpo- or metatarsophalangeal carpal deformities.33 Another study showed that foals deformities went on to a form of athletic use.31 The poor with incomplete ossification of the tarsal bones and results obtained in the foals treated for metacarpo- or greater than 30% collapse of the third and central tarsal metatarsophalangeal deformities were attributed to the bones had a poorer outcome than did similar foals with fact that several of these foals were operated on near or less than 30% collapse,34 thereby stressing the impor- after the end of the rapid growth phase of the distal tance of early recognition and treatment. third metacarpal or metatarsal growth plate. Racing per- Conflicting results regarding the significance of the formance after HCPTE in Thoroughbreds has been location of the pivot point and the presence of radi- reported; treated foals had fewer starts at 2 years of age ographic abnormalities in cases of carpal deformities and lower start percentile ranks.32 However, it is difficult have been published. According to one study, the more to rely heavily on these comparison numbers because radiographic abnormalities that are seen distal to the many foals that have undergone surgery for angular limb distal radial physis and the more distal the location of

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Ostectomy and Osteotomy Techniques within 2 to 3 weeks, surgical intervention is considered. for Correcting Angular Limb Deformities If no improvement is seen within 2 months for a carpal After Cessation of Physeal Growth or tarsal angular limb deformity, surgery is considered. Closing wedge ostectomy This approach tends to decrease the number of foals A bone wedge should be removed from the horizontal that require physeal bridging. plane in the physeal region of the affected bone. Fixation can be achieved using one or two dynamic compression REFERENCES plates. 1. Gaughan EM: Angular limb deformities in horses. Compend Contin Educ Pract Vet 20(8):944–946, 955, 1998. Step ostectomy in the sagittal plane 2. Auer JA, Martens RJ, Morris EL: Angular limb deformities in foals, part I. A vertical bone wedge, the point of which should be Congenital factors. Compend Contin Educ Pract Vet 4(8):330–339, 1982. located at the pivot point of the deformity, should be 3. Auer JA: Angular limb deformities, in Auer JA, Stick JA (eds): Equine removed from the center of the affected bone. Fixation Surgery. Philadelphia, WB Saunders, 1999, pp 736–752. can be achieved by inserting lag screws and a bone plate. 4. Leitch M: Angular limb deformities arising at the carpal region in foals. Compend Contin Educ Pract Vet 1(11):39–43, 1979. Step osteotomy in the frontal plane 5. Caron JP: Angular limb deformities in foals. Equine Vet J 20(3):225–228, 1988. A Z-shaped osteotomy in the frontal plane of the 6. Fretz PB: Angular limb deformities in foals. 2(1):125–150, affected bone should be performed. The distal horizontal Vet Clin North Am 1980. cut should be located at the level of the pivot point of th the deformity. Fixation can be achieved by inserting lag 7. Auer JA, Martens RJ: Angular limb deformities in young foals. Proc 26 Annu Conv AAEP:81–96, 1980. screws and a bone plate. 8. Leitch M: Musculoskeletal disorders in neonatal foals. Vet Clin North Am 1(1):189–207, 1985.

35 9. Sedrish SA, Moore RM: Diagnosis and management of incomplete ossifica- the pivot point is, the poorer is the prognosis. In tion of the cuboidal bones in foals. Equine Pract 19(5):16–21, 1997. another study, no such correlation could be made.36 10. Stashak TS: Angular limb deformities associated with the carpus (carpus val- Also, it has been demonstrated that surgical manipula- gus and carpus varus, medial deviation of the carpus and lateral deviation of tion of distal radial physeal growth can cause changes in the carpus), in Stashak TS (ed): Adams’ Lameness in Horses. Philadelphia, Lea the angles of all the carpal joints.37 Thus surgical manip- & Febiger, 1987, pp 624–641. ulation of physeal growth may be successful in correct- 11. Barr ARS: Management of angular limb deformities in the foal. Equine Vet ing angular limb deformities originating distal to the Educ 7:75–78, 1995. growth plate (e.g., epiphyseal deformities). 12. Parente EJ: Angular limb deformities, in Ross MW, Dyson SJ (eds): Lame- In summary, the prognosis for foals with angular ness in the Horse. Philadelphia, WB Saunders, 2003, pp 557–561. deformities is generally good with the exception of foals 13. Auer JA, Martens RJ, Morris EL: Angular limb deformities in foals, part II. Developmental factors. Compend Contin Educ Pract Vet 5(1):27–35, 1983. with greater than 30% collapse of the third and central tarsal bones. However, the age at which the foals are 14. Bertone AL: Angular limb deformities associated with the carpus (carpus valgus and varus; medial and lateral deviation of the carpus), in Stashak TS diagnosed and treated influences the prognosis. Defor- (ed): Adams’ Lameness in Horses. Philadelphia, Lippincott Williams & mities that are treated near or after the end of the rapid Wilkins, 2002, pp 830–841. growth phase have a less favorable prognosis. This 15. Fretz PB, Cymbaluk NF, Pharr JW: Quantitative analysis of long-bone places the clinician in a dilemma. If treatment is delayed growth in the horse. Am J Vet Res 45(8):1602–1609, 1984. until the foal is 4 to 6 months of age, the prognosis for a 16. Mitten LA, Bertone AL: Angular limb deformities in foals. JAVMA 204(5): successful outcome is decreased. On the other hand, if 717–720, 1994. treatment is done early, many foals may receive unneces- 17. Bertone AL, Turner AS, Park RD: Periosteal transection and stripping for sary treatment. In Dr. Ducharme’s practice, which con- treatment of angular limb deformities in foals: Clinical observations. JAVMA 187(2):145–152, 1985. sists mainly of Thoroughbred racehorses, foals are 18. Read EK, Read MR, Townsend HG, et al: Effect of hemi-circumferential evaluated within 2 weeks of birth and then every 2 to 3 periosteal transection and elevation in foals with experimentally induced weeks thereafter. Significant angular limb deformity is angular limb deformities. JAVMA 221(4):536–540, 2002. treated with corrective trimming and shoeing in the 19. Auer JA, Martens RJ: Periosteal transection and periosteal stripping for cor- hope that surgical treatment will be unnecessary. If an rection of angular limb deformities in foals. Am J Vet Res 43(9):1530–1534, angular limb deformity involving the metacarpo- or 1982. metatarsophalangeal joint shows no improvement 20. Auer JA: Periosteal transection of the proximal phalanx in foals with angular

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limb deformities of the metacarpo/metatarsophalangeal area. JAVMA 187(5): 30. Fretz PB, McIlwraith CW: Wedge osteotomy as a treatment for angular 496–499, 1985. deformity of the fetlock in horses. JAVMA 182(3):245–250, 1983. 21. Jansson N: Angular limb deformities in 4 foals: Treatment by periosteal tran- 31. Fretz PB, Donecker JM: Surgical correction of angular limb deformities in section and stripping. Equine Vet Educ 7(2):70–74, 1995. foals: A retrospective study. JAVMA 183(5):529–532, 1983. 22. Mase CA: The anatomy and response to surgical manipulation of the distal 32. Mitten LA, Bramlage LR, Embertsson RM: Racing performance after hemi- radial growth plate in foals [master’s thesis]. University of Saskatchewan, circumferential periosteal transection for angular limb deformities in thor- 1986. oughbreds: 199 cases (1987–1989). JAVMA 207(6):746–750, 1995. 23. Deppermann F, Dallek M, Meenen N, et al: The biomechanical significance of the periosteum for the epiphyseal groove. Unfallchirurgie 15:165–173, 1989. 33. Dutton DM, Watkins JP, Honnas CM, et al: Treatment response and athletic outcome of foals with tarsal valgus deformities: 39 cases (1988–1997). 24. Heinze CD: Epiphyseal stapling. th :203–216, 1963. Proc 9 Annu Conv AAEP JAVMA 215(10):1481–1484, 1999. 25. Heinze CD: Epiphyseal stapling: A surgical technique for correcting angular 34. Dutton DM, Watkins JP, Walker MA, et al: Incomplete ossification of the limb deformities. Proc 15th Annu Conv AAEP:59–73, 1969. tarsal bones in foals: 22 cases (1988–1996). JAVMA 213(11):1590–1594, 1998. 26. Turner AS, Fretz PB: A comparison of surgical techniques and associated complications of transphyseal bridging in foals. Proc 23rd Annu Conv 35. Pharr JW, Fretz PB: Radiographic findings in foals with angular limb defor- AAEP:275–287, 1977. mities. JAVMA 179(8):812–817, 1981. 27. Vaughan LC: Growth plate defects in foals. Vet Rec 98:165–168, 1976. 36. Bertone AL, Park RD, Turner AS: Periosteal transection and stripping for 28. Fretz PB, Turner AS, Pharr J: Retrospective comparison of two surgical tech- treatment of angular limb deformities in foals: Radiographic observations. niques for correction of angular deformities in foals. JAVMA 172(3):281–286, JAVMA 187(2):153–156, 1985. 1978. 37. Brauer TS, Booth TS, Riedesel E: Physeal growth retardation leads to correc- 29. Auer JA: Beitrag zur frühdiagnose und behandlung einer speziellen stel- tion of intracarpal angular deviations as well as physeal valgus deformity. lungsanomalie beim pferd. Pferdeheilk 5(4):201–205, 1989. Equine Vet J 31(3):193–196, 1999.

ARTICLE #4 CE TEST This article qualifies for 2 contact hours of continuing education credit from the Auburn University College of Veterinary CE Medicine. Subscribers may purchase individual CE tests or sign up for our annual CE program. Those who wish to apply this credit to fulfill state relicensure requirements should consult their respective state authorities regarding the applicability of this program. To participate, fill out the test form inserted at the end of this issue or take CE tests online and get real-time scores at CompendiumVet.com.

1. Which statement regarding management of con- 3. To allow rapid growth in young foals, tube casts genital angular limb deformities is correct? should be changed at ______intervals. a. In most foals born with mild to moderate angular a. 3- to 4-day c. 3- to 4-week limb deformities, spontaneous resolution is unlikely. b. 10- to 14-day d. 4- to 6-week b. In most foals born with mild to moderate angular limb deformities, spontaneous resolution occurs 4. Corrective ostectomy or osteotomy is within 2 to 4 weeks of life. a. preferred in treating tarsal bone hypoplasia. c. In most foals born with angular limb deformities due b. preferred in treating severe carpal or tarsal bone to carpal or tarsal bone hypoplasia, spontaneous res- hypoplasia. olution occurs within 2 to 4 weeks of life. c. generally performed before cessation of physeal growth. d. In most foals born with angular limb deformities due d. generally performed after cessation of physeal growth. to carpal or tarsal bone hypoplasia, spontaneous res- 5. According to a recent experimental study, olution occurs within 4 to 8 weeks of life. HCPTE was a. more effective than stall confinement alone in cor- 2. To avoid development of a contracted foot in a recting carpal angular limb deformity. foal, glue-on shoes should not be left on for b. less effective than stall confinement alone in correct- longer than ing carpal angular limb deformity. a. 2 months. c. as effective as stall confinement alone in correcting b. 3 months. carpal angular limb deformity. c. 2 weeks. d. as effective as unlimited pasture exercise in correct- d. none of the above ing carpal angular limb deformity.

February 2005 COMPENDIUM 146 CE Angular Limb Deformities in Foals:Treatment and Prognosis

6. Which statement regarding treatment of foals with carpal bone hypoplasia is correct? a. Foals with carpal bone hypoplasia often require surgical treatment after an initial period of splint bandaging. b. Foals with valgus deformities caused by carpal bone hypoplasia should be treated with confinement and by applying a glue-on shoe with extension to the inside. c. Foals with valgus deformities caused by carpal bone hypoplasia should be treated with confinement and by applying a glue-on shoe with extension to the outside. d. Foals with carpal bone hypoplasia should be treated with splint bandaging or tube casting.

7. A 6-week-old foal with a significant varus deformity caused by asymmetric growth at the distal metatarsal growth plate in the left hindlimb is best treated with a. splint bandaging and confinement. b. confinement. c. corrective trimming and, possibly, shoeing as well as confinement. d. surgery, corrective trimming, and, possibly, shoeing as well as confinement.

8. Which statement regarding HCPTE is true? a. HCPTE temporarily retards longitudinal growth on the convex aspect of the deformity. b. HCPTE temporarily increases longitudinal growth on the concave aspect of the deformity. c. Foals that have undergone HCPTE require a second surgery to prevent overcorrection of the deformity. d. HCPTE exerts its effect for approximately 3 months.

9. Which statement regarding TPB is correct? a. TPB is primarily used in young foals with severe angular deformities, miniature foals, or foals with significant limb deformity after the rapid growth phase. b. TPB is primarily used in foals with diaphyseal deformities. c. Contrary to HCPTE, overcorrection has not been reported after TPB. d. TPB is primarily used in young foals with severe angular deformities, miniature foals, or foals with diaphyseal deformities.

10. Postoperative treatment of foals using HCPTE includes a. free pasture exercise because it tends to increase the rate of correction. b. confinement. c. splint bandaging. d. none of the above

COMPENDIUM February 2005