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EQUINE VETERINARY EDUCATION / AE / FEBRUARY 2018


six foals had valgus of the right carpus, two foals had valgus of the left carpus, one foal that had a right carpal valgus had a contralateral left carpal varus. All screws were removed when the carpus reached an angle of between 1° and 5°. There was one case of implant failure due to implant infection with Staphylococcus aureus. This particular foal had poor patient compliance with bandaging. There was one complication during surgery when a drill bit tip broke within


a) R L


the radius of the foal; the tip was left in place and did not affect the foal. The broken drill bit may have affected the sales value of the horse; however, this particular horse was not destined for sales so no attempt at retrieval was made. Two foals were treated for carpal varus deformities. One


had bilateral carpal varus (2° on the left and 3° on the right). This foal also had concurrent fetlock varus deformities. Long-term follow-up was achieved through personal


owner or farm manager communication. Except for one foal with white hairs, and one with a persistent periosteal reaction, all cases were reported to have excellent cosmetic outcomes.


Discussion


Most ALDs in foals are self-limiting or self-correcting, or responsive to conservative approaches and management changes. Some researchers are of the opinion that all angular deformities will correct with conservative management alone (Read et al. 2002); however, one study evaluating a large number of horses through the first year of life showed that up to 14% of carpal valgus deformities did not self-correct to what was considered a desirable conformation (Santschi et al. 2006). It is imperative to recognise severe deformities or those


b)


that are not improving, or are deteriorating, in order for timeous surgical intervention. Early surgical intervention at the level of the distal metacarpus and metatarsus is essential, as rapid growth reduces at approximately 10 weeks of age (Auer 2012), and failure to utilise this window of growth potential leads to poor response to treatment. Intervention at the distal radius and distal tibia is possible up to the age of 15 months (Auer 2012); however, valgus deviation in the carpi at an angle of >10° may potentially lead to lateral physeal collapse and should be approached more aggressively (Ruggles and McIlwraith 2008). Fetlock varus or toe-in conformation is a highly undesirable trait leading to severe penalty at time of sales as well as potential degenerative changes in the fetlock joint during athletic career (Marks 2000; Ross 2003). There have been large retrospective studies on the


L R


Fig 1: a) Dorsopalmar radiographs of the carpi of a 31-day-old colt with bilateral carpal valgus (left carpus 17°, right carpus 14°) and physeal dysplasia (arrow) prior to surgery. b) Dorsopalmar radiographs of the carpi of the same colt prior to removal of the right screw 35 days later,


© 2017 EVJ Ltd


effectiveness of a single transphyseal screw for correction of both forelimb and hindlimb fetlock varus (Kay et al. 2005; Roberts et al. 2009). Some authors exclusively use single transphyseal screws in the fetlock region, even in animals younger than 4 weeks (Roberts et al. 2009). The majority of cases in these large studies had mild to moderate varus deformities (<4°), whereas our inclusion criteria selected for those foals with more severe deviations (≥4°). The mean age at time of implant placement and duration of time the implants remained in place in this case series was comparable to other reported studies. There are also reports that single transphyseal screws are not effective in younger foals, due to poor holding potential of the soft epiphyseal bone (Auer 2011; Russell 2013). Transphyseal screws were placed in the distal metatarsal physes of two foals younger than 14 days (one hind fetlock varus, 6°, one hind fetlock valgus, 7°); in both cases, holding potential of the epiphysis was sufficient and no over-correction occurred with the use of 4.5 mm standard cortex screws. In both of these cases, great care was taken to remove the implants prior to complete correction of the deviation due to the potential for further correction after removal of the implants. Neither foal developed excessive callus reaction. Two foals were treated


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