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EQUINE VETERINARY EDUCATION
Equine vet. Educ. (2018) 30 (2) 88-93 doi: 10.1111/eve.12742
Original Article
Single transphyseal screws for the correction of moderate to severe angular limb deformities in 28 Thoroughbred foals
A. Gray†‡*, P. Randleff-Rasmussen†‡ and O. M. Lepage‡ †Drakenstein Veterinary Clinic, Paarl, Western Cape, South Africa; and ‡University of Lyon, VetAgro Sup, Veterinary Campus of Lyon, Marcy l’Etoile, France. *Corresponding author email:
drewgrays@yahoo.com
Keywords: horse; valgus; varus; surgery
Summary This study reports on the effective use of a single transphyseal screw for the treatment of moderate to severe angular limb deformities (ALDs) of the fetlocks and carpi of 28 young Thoroughbred foals. The objective was to evaluate the surgical management of foals with moderate to severe ALDs treated with single transphyseal screws. Evaluation of medical records of 28 Thoroughbred foals treated with single transphyseal screws placed across the distal radial, metacarpal and metatarsal physes was undertaken. The angle of joint deviation was measured prior to implantation and at removal of the implants, and the degree of improvement was calculated. A total of 39 screws were placed: 24 in the distal metacarpus or metatarsus and 15 in the distal radial physis. Varus or valgus deformities in the fetlock improved by 4–5° over a period of 15–30 days. Varus or valgus deformities in the carpi improved by 8–11° in 11– 56 days. One case failed to improve adequately due to implant infection. Single transphyseal screws were effective in treating moderate to severe varus and valgus ALD of the fetlocks and carpi in young Thoroughbred foals. Further investigation into their use in the distal radius in young foals is needed. While single transphyseal screws are almost exclusively used by some clinics in the distal metatarsal and metacarpal physes, many clinicians do not use them in the distal radial physis of young foals due to fear of over- correction, physitis and metaphyseal collapse. This was not observed in any of our cases.
Introduction
Congenital angular limb deformity (ALD) observed as an axial deviation in a frontal plane is relatively common in foals and strategies for management thereof, including surgical techniques, are well established (Auer 2012). Foals with ALD can present with either a varus deformity (medial deviation distal to the affected joint/physis) or a valgus (lateral deviation). These deviations are often associated with axial rotation of the distal limb and are mainly observed in the fetlocks, tarsal or carpal regions (Auer 2012). Diagnosis is mainly based on inspection, manipulation
and radiography. To ensure optimal outcomes, early recognition and monitoring are important. The need for early diagnosis is essential, especially if incomplete ossification is suspected, and the clinician always needs to evaluate the entire limb during weight bearing and locomotion. Radiography is used as a complementary examination to allow exact determination of the location and degree of the
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deformity and is essential for assessment of cuboidal bone ossification (Bramlage and Embertson 1990). Angular limb deformity conditions require corrective
management and one needs to decide on the most appropriate treatment. Most ALDs are self-correcting and only require conservative management, including restricted exercise, splints, corrective hoof trimming and, in some cases, shoeing with extensions placed on the medial or lateral aspect (Ruggles and McIlwraith 2008). In cases of severe deformities (>10° valgus or 3° varus of
the carpus, >3° valgus or varus of the fetlock) (Munroe and Weese 2011) or those that fail to respond adequately to conservative approaches, other treatments focused on growth acceleration or retardation of the bones involved in the ALD, need to be considered. These techniques depend on the growth potential at the physis of the developing foal. Growth acceleration is performed on the concave aspect of the limb and growth retardation on the convex aspect. Periosteal transection and elevation is the original method (Auer and Martens 1982) of growth acceleration but modifications of the technique to minimise the surgical approach have been described, such as hemicircumferential periosteal transection through a stab incision (Auer 2012) and physeal stimulation (Colles 2008). There is currently a debate about the efficacy of these growth accelerating techniques: a recent study by Baker et al. (2015) indicated that periosteal elevation has no effect on carpal angulation. Conversely, work on lambs has shown that periosteal transection and elevation have a direct effect on parthyroid hormone and related peptide, all of which are involved in bone growth (Von Rechenberg et al. 2010). Growth retardation is achieved by means of a temporary
transphyseal bridge that acts to retard growth on the convex aspect of the limb. The original transphyseal stapling methods (Heinze 1963) are used less frequently for routine bridging except in very young foals, age <3 weeks, and have mostly been replaced by screws and cerclage wire (Fretz and Donecker 1983), the latter material sometimes replaced by a small bone plate (Auer 2012). A nonsurgical approach to local growth retardation has also been described, using radial shockwave therapy (Bussy et al. 2013). More recently, implantation of a single transphyseal screw
has been described as an effective method for retarding growth of distal metacarpal and metatarsal bones in young horses with mild to moderate ALDs (Kay et al. 2005; Roberts et al. 2009). In this case series we report the results of foals with moderate to severe ALDs in the fetlock or the carpi, treated with only a single transphyseal screw.
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