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EQUINE VETERINARY EDUCATION / AE / MAY 2018


a)


b)


Fig 7: Case 2: pancarpal arthrodesis with 2 plates, 5 month post-operative radiographs. (a) Lateromedial projection, (b) dorsopalmar projection. Bony ankylosis of the middle carpal joint. Thinning of the antebrachial carpal and carpometacarpal joint spaces. Periarticular osteophytes of the antebrachial carpal, middle carpal and carpometacarpal joints, more pronounced laterally.


instructed to keep the colt in the box for 1 month, have the cast removed after this time and then let the horse on a small paddock for 1 month. Two and a half months after surgery, the colt was turned out in pasture. Radiographic examination 3 months post-operatively showed beginning of bony ankylosis of the MC and CMC with mild periarticular bone formation. The DMPLO views showed healing of the fracture line in the C2 and partial fusion of the bone with the head of the proximal MCII. Ten months after surgery, a video of the horse showed that it was sound at walk and trot and was kept in pasture. Radiographs revealed ankylosis of the


MC joint and marked thinning of the CMC joint. Carpal flexion was calculated from a picture at 44° (Tulloch et al. 2015).


Discussion


We report a minimally invasive technique for partial and pancarpal arthrodesis using LCP in 3 horses. In all 3 cases, complete debridement of the visually apparent cartilage in the MC (Cases 1, 2 and 3), and the ABC (Case 2), was achieved with curettes and motorised (shaver) burrs, using a standard arthroscopy approach. Motorised burrs should be used with caution, specifically for cartilage removal, to avoid inadvertent or excessive bone trimming leading to destabilisation of the bones. James and Richardson (2006) described arthroscopic debridement of the cartilage, in a case of metacarpophalangeal/metatarsophalangeal arthrodesis, as having the advantage of being thorough and accurate, but the disadvantage of requiring significantly more time. In our cases, arthroscopic debridement was completed quickly due to the arthroscopically noncomplex appearance of the MC and ABC joints. The arthroscope and the instruments were switched so that all visually apparent


© 2016 EVJ Ltd


cartilage could be removed. We believe that, with the help of a motorised shaver tool, arthroscopic debridement for carpal arthrodesis can be completed within an acceptable time. An alternative minimally invasive debridement technique is to drill the cartilage with a 5.5 mm drill bit inserted through several stab incisions. James and Richardson (2006) reported using this technique for minimally invasive metacarpophalangeal/metatarsophalangeal and proximal interphalangeal joint arthrodesis. This procedure is quick but there is a possibility of incomplete cartilage removal. We believe that with the drilling technique there is a definite risk of incomplete cartilage removal, particularly in the MC and ABC joint, (due to the different small bones, articular steps and difficult fluoroscopic assessment). However, we did use drilling to debride the rigid CMC joint. We used a horizontal fanning technique through 3 incisions and this resulted in radiographically visible bony fusion in all 3 cases. Use of the drilling technique for treatment of CMC osteoarthritis is established and was evaluated on 12 client horses by Barber et al. (2009). It has also been used by Carpenter et al. (2008) for the CMC joint during a pancarpal arthrodesis procedure. A minimally invasive approach was used to apply the


plates. We made small skin incisions at the distal or proximal end of the plate and passed a custom-made tunnelling tool under the skin and under the joint capsule to create a subcapsular, intrasynovial path for the plate. We then passed the plate and applied screws through small skin incisions at the level of the plate holes. The minimally invasive principle of bone plate fixation was described by James and Richardson (2006) in a case series of 32 horses with lower limb injuries. A single plate was applied in all these cases, whereas 2 or 3 plates were minimally invasively applied in our cases. This added the difficulty of having to place the screws of one plate without them interfering with the screws of the other


plate(s). In Cases 1 and 3, this step was facilitated by fluoroscopic image intensification, which also reduced the need for numerous radiographs. Fluoroscopy was not available for Case 2 and radiological exposure for the surgical team was probably higher than if an open approach had been used. One advantage of the minimally invasive approach is the ease of skin closure. Skin closure can be challenging with an open approach, where 2 or even 3 plates are placed, and can require tension-relieving sutures (Carpenter et al. 2008) or even relief incisions. These were not necessary in our cases and we were able to close all incisions with simple skin sutures and/or staples. This easier closure of the incision might help to reduce surgery time. However, the time taken to close the incisions was not recorded for any of the cases and would not be easy to compare with other reports due to the small number of cases published. The tension due to the subcutaneous plates was distributed over the many small incisions and this facilitated healing of the skin incisions. In all 3 cases, incisional healing was excellent, rapid, without dehiscence or secondary healing, and the final outcome was cosmetically appealing. LCPs were applied in all our cases. These plates were


initially described by Levine and Richardson (2007), in a case series of fracture repair and distal limb arthrodesis in 31 horses. They suggested the major advantage of such LCPs was the increased stability. The comfort of the horses after surgery in our report was good, and no loosened implants or screws were observed, confirming the stability of the constructs. Another advantage of LCPs cited by Levine and


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