EQUINE VETERINARY EDUCATION / AE / FEBRUARY 2018
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Materials and methods
Animals and study design All animals that underwent evaluation/surgery for ALD between August 2010 and April 2015 were identified. Each foal underwent a preoperative examination which consisted of clinical and dynamic locomotor examination as well as radiographic examination. Thoroughbred foals that showed deviations of 4° or greater at the fetlocks or carpal valgus of 10° or greater or varus of 2° or greater were selected for inclusion in this study. Single transphyseal screws were placed in most foals after more conservative approaches failed to correct the deviation adequately. Medical records were reviewed for age in days at time of screw placement and removal, the joint affected and direction of deviation, the number of screws placed and degree of angulation of the deviation before placement and after removal of screws. Cosmetic blemishes and post-operative complications were also noted. Dorsopalmar and dorsoplantar radiographs taken prior to screw placement and at or after time of removal were evaluated for each case. Prior to surgical intervention, all foals were examined
standing and walking in a straight line on a firm surface to and from the examiner. Limbs were evaluated perpendicular to the frontal plane of the outward-rotated limb (Auer 2012). The affected limbs were subsequently radiographed using digital radiograph equipment with dorsoplantar and dorsopalmar views taken with the x-ray beam at a right angle to the frontal plane of the limb with a minimum of 10 cm of the long bones above and below the affected joint included in the projection. Shape and degree of ossification of the cuboidal bones was noted. For the carpus, angle of deviation was calculated after drawing two lines, one through the middle of the distal radius and one through the middle of the McIII/MtIII diaphysis. For deviations of the fetlocks, lines through McIII/ MtIII and P1 were drawn. The angle of deviation was calculated where these lines intersected. Radiographs were all evaluated by two authors and the degree of angulation measured independently. A standard premedication and anaesthetic protocol was
used for surgery.
Surgery Single transphyseal screws were placed under general anaesthetic using the same technique as described by Kay
and Hunt (2009). Hooves were balanced, and extensions placed as necessary.
Post-operative follow-up A standard controlled exercise regime was followed post- operatively. Foals were re-evaluated every week to assess limb angle
and decide on time of screw removal. Once the limb appeared clinically straight, radiographs were taken to assess bone alignment, to ascertain whether correction of the angular deviation was complete. Some screws were removed while a 1–2° deviation remained as there is some further correction of the deformity after implant removal. Radiographs of the affected limb were evaluated either at the time of screw removal or later, and angles of deviation measured as described above. Screws were then removed, either under standing sedation with local anaesthesia or under a short general anaesthetic.
Results
There were 157 foals with ALD of the fetlocks or carpus region that were operated on over a 4-year period, from August 2010 to April 2015 at the first author’s clinic. Of these, 28 foals with placement of 39 cortex screws met the inclusion criteria. These are detailed in Table 1. All individuals were assessed clinically before and after surgery by the same clinician. Sixteen screws were placed into 10 foals for front fetlock
varus. All screws were removed when a radiographic angle of 0–2° varus was achieved and the clinician was satisfied upon subjective clinical evaluation. One foal had an unrelated lameness of the left forelimb and one foal had a large wound on the operated leg due to a bandage rub, leading to white hairs and a cosmetic blemish. Six foals received screws in the hind fetlock for unilateral
varus. All screws were removed when the radiographic degree of angulation was 0–1°. One foal had a persistent periosteal reaction at the site of screw placement, which was later surgically removed prior to yearling sales. Two foals had valgus deviations of the fetlocks. One foal
with a hindlimb valgus of the fetlock had a concurrent valgus deformation of MtIII, which was addressed with growth acceleration along the lateral aspect of the bone. Ten foals were treated with 12 screws for carpal valgus deformities. Two foals had bilateral carpal valgus (Figs 1 and 2),
TABLE 1: Details of the 28 Thoroughbred foals with severe angular limb deformities treated with the transphyseal screw technique
Number of screws placed
Front fetlock varus RF 8, LF 8
Mean age at screw placement (days)
85.5 Hind fetlock varus RH 2, LH 4 68
Front fetlock valgus LF 1 hind fetlock valgus LH 1 Carpal varus Carpal valgus
RF 1, LF 2 RF 8, LF 4
105 14 35 47
Mean duration of implant (days)
32 27
24 27 30 35
Mean angle of deviation at insertion (degree)
5.3 4.8
4 7 5
15 LF, left frontlimb; LH, left hindlimb; RF, right frontlimb; RH, right hindlimb. © 2017 EVJ Ltd
Mean angle of deviation at removal (degree)
0.93 0.3
2 2 3 4
Mean degree of improvement Complications
4.4 4.5
2 5 8
11 1 implant infection
1 bandage rub with resultant skin defect, 1 poor response
1 persistent periosteal reaction
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