EQUINE VETERINARY EDUCATION / AE / MAY 2018


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collected from the ileal wing and injected into the MC joint through the lateral and medial arthroscopy portals using 3 mL syringes with their tips cut off. The portals were then closed in a routine manner and the fluoroscope positioned in a lateromedial direction. Debridement of the CMC joint cartilage was achieved using a drilling technique through stab incisions. A 4.5 mm drill bit was inserted approximately 2.5 cm laterally, dorsolaterally and dorsomedially and the drilling was performed with a fanning technique (3 horizontal directions for each insertion point) under fluoroscopic guidance. A longitudinal 3-4 cm skin incision was made on the lateral aspect of the proximal third of the third metacarpal bone (MCIII), after which a custom-made tunnelling tool/plate-passer (James and Richardson 2006) was inserted under the skin (under fluoroscopic guidance) to create a subcutaneous tunnel in direct apposition to the


periosteum. The tunnelling tool was pushed over the thin fibrous CMC joint capsule and under the thick joint capsule of the MC joint by pressing its tip against the distal aspect of the capsule, incising it through the skin and gliding the tool under the capsule and under the synovial membrane (Supplementary Item 1). This was performed to be able to place the plate close to the bone surface and create stability as the distance between the plate and the bone was reduced and therefore allowing to anchor the carpal bones with angled nonlocking cortical screws. A similar incision was made on the proximal aspect of the MC joint capsule to allow the tool to exit. A 7-hole narrow LCP plate was suitably contoured with radiographic control using a plate-bending press (Synthes). After verifying the appropriate placement by fluoroscopy and radiography, stab incisions were made through the most proximal and most distal holes of the plate after palpation of the depression of the plate


hole. LCP drill guides were inserted and radiographic and fluoroscopic images were again obtained before drilling holes in the MCIII and intermediate carpal bone, and inserting the locking head screws (LHS) while pressing the plate firmly against the bone. A 4.5 mm cortical screw was placed in the intermediate carpal bone using an angle in order to avoid entering the articulation between the intermediate carpal bone and the third carpal bone. An LHS was placed in the third carpal bone, the remaining 3 distal holes were filled with 2 LHS and a 4.5 mm cortical screw inserted using stab incisions in the McIII. This procedure was repeated on the medial side using a 7-hole broad LCP plate. The most proximal hole was filled with a LHS inserted in the radial carpal bone, the second proximal hole was a LHS inserted


the third carpal bone and the third most proximal hole was filled with a 4.5 mm cortical screw inserted in the third carpal bone. Three LHS and one 4.5 mm cortical screw were anchored in the MCIII (Fig 2). The skin incisions were closed in a single layer using 1 USP monofilament polyamid (Ethilon).1 A full limb fibreglass cast was applied and a head and tail rope system used to assist recovery, which was uneventful. Anaesthesia time was 5 h and surgical time was 3.25 h.


Case 2 Premedication, sedation, induction and maintenance of general anaesthesia were similar to Case 1. The mare was placed in dorsal recumbency, with the limb attached to an electrical winch. This positioning allowed a good alignment of the limb in extension and radiographic control of the position of the limb and the plates was easy to achieve


a)


b)


AD POSTOP AD POSTOP


Fig 2: Case 1: Partial arthrodesis of the middle carpal and carpometacarpal joints with 2 plates (one 7-hole broad locking compression plate dorsomedially and one 7-hole narrow locking compression plate dorsolaterally) 24 h post-operative radiographs. (a) Lateromedial projection, (b) DP projection. carpometacarpal [CMC], middle carpal [MC] joint or antebrachial carpal.


from all directions. General anaesthesia was maintained as described for Case 1. The limb was aseptically prepared and draped for a pancarpal arthrodesis. The MC and ABC joint were debrided using arthroscpy, the CMC joint was debrided with the drilling technique as described for Case 1. An arthroscopic motorised shaver device (Arthrex Shaver with Oval FlushCut 8 Flute, 5.5 mm, 13 cm, Ref AR 8550FOE)2 was used to facilitate articular cartilage debridement in the MC and ABC joint. Cancellous bone graft (approximately 6 mL) was collected from the sternum due to the position of the horse in dorsal recumbency. A technique described by Richardson et al. (1986) was used; briefly, a 7 cm incision was performed approximately 20 cm cranial to the xyphoid, the pectoral muscle was elevated and after removing the ventral cartilage of the underlying forth and fifth sternebrae, the cancellous bone was removed using a large curette and was injected into MC and ABC joint through the arthroscopy portals similar to Case 1. First, a 12-hole, 5.5 mm broad LCP plate was placed dorsolaterally by tunnelling and using radiographic control. The plate was placed under the MC and ABC joint capsule through stab incisions similar to Case 1. Five 5.0 mm LHS screws were anchored in the distal radius, one LHS was anchored in the radial, intermediate and ulnar carpal bone, one 4.5 mm cortical screw placed in lag fashion across the plate and the fractured C4 through stab incisions, and 3 LHS were anchored in the MCIII. A second, 13-hole, broad 4.5 mm plate was placed dorso-medially and was stabilised with 4 LHS in the distal radius and 4 LHS anchored in the MCIII (Figs 3 and 4). Again the plate was placed under the MC and ABC joint capsule. The skin was closed using a combination of skin sutures (same as Case 1) and skin staples. Full limb fibreglass cast application and assisted recovery was as described for Case 1. Total anaesthesia time was 5 h and total surgery time 3.5 h.


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