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Richardson (2007) was the reduced need for accurate anatomical plate contouring. Plate contouring, however, was considered necessary in our cases as the small carpal bones were fixed to the plate with 4.5 mm cortical screws in neutral or lag fashion. We used cortical screws in order to anchor as much of the small carpal bones as possible so as to increase stability. The application of cortical screws in a plate in a noncontact way could lead to screw loosening. Contouring the plates proved challenging, as the minimally invasive approach did not allow direct visualisation of the bone contours. Several radiographs or fluoroscopic image intensification were required for this step. The number of radiographic of fluoroscopic images is likely to be smaller in an open approach, pointing out a disadvantage of the minimal invasive approach. A third advantage of LCP mentioned by Levine and Richardson (2007) was that the threaded drill guides were helpful when drilling and applying the screws through small incisions. We add that these threaded drill guides made it possible to determine the position of the intended screw on radiographs and helped to hold the plate in place during insertion of the first LHS screw. We agree with Levine and Richardson’s comment that the use of self-tapping LHS screws eliminates the time-consuming step of tapping predrilled holes and would reduce surgery time. LCP and LHS implants have the disadvantage of being expensive, and our 3 cases of carpal arthrodesis each required 2 or 3 plates, leading to higher costs compared to the dynamic compression plate system. Reported complications after carpal arthrodesis include


supporting limb lameness, and infections of the incision and implant (Auer and Lischer 2012). The minimal invasive approach for carpal arthrodesis might have reduced the risk for infection in our cases. Minimally invasive plate fixation in horses reduces the tissue exposed to contamination and keeps the soft tissue envelope more intact than the conventional open approach (James and Richardson 2006). In their publication, James and Richardson compared 10 minimally invasive metacarpophalangeal/ metatarsophalangeal and proximal interphalangeal joint arthrodeses with 15 treated by conventional open approach. Only 4 of the 10 minimally invasive arthrodeses became infected, compared with 12 out of the 15 treated by open approach. There was no significant difference between these groups; however, a tendency is visible and the authors suggested that the minimally invasive arthrodesis technique may reduce morbidity and mortality of these procedures (James and Richardson 2006). For both partial and pancarpal arthrodesis, the incision required with the conventional approach is very long (up to 40 cm) (Carpenter et al. 2008) and therefore prone to postoperative infection. We report our experience of carpal arthrodesis using a minimal invasive approach in 3 cases and no infection occurred in this small sample group. However, we suspected a chronic infection in Case 1 and removed the plates 8 months after surgery. The bacteriological sample of the surgical site and plates were negative and an inflammatory irritation or instability might have been the cause of the intermittent discomfort. The horse was comfortable after the removal of the plates. We believe that using the minimal invasive approach for carpal arthrodesis reduces this risk, because of less tissue being exposed to contamination, less soft tissue trauma, tissue handling and tissue dehydration (James and Richardson 2006).


We found that the horses with the partial carpal


arthrodesis (CMC and MC joints) had a nonpainful flexion with remaining angles of 42.6° and 44°, 3 years (Case 1) and 10 months (Case 3) after surgery, respectively. The remaining carpal flexion was calculated by Tulloch et al. (2015) in an


ex vivo model to be 43  7.6° after MC/CMC arthrodesis. The authors speculated that this would allow a horse to be used at a trot or slow canter and the outcome of our cases supports their statement, as both Cases 1 and 3 could trot and gallop without signs of lameness and Case 1 was used as a leisure riding horse. Pancarpal arthrodesis is known to be a salvage procedure. The mare in our study showed gait changes due to the stiffness of the limb but was able to trot and gallop and could fulfil the intended use as a breeding mare.


The minimally invasive LCP plate fixation technique


seems to be well suited for partial and pancarpal joint arthrodesis. Disadvantages include the greater radiological exposure, due to the multiple control radiographs required to correctly apply the plates and screws. Surgery time is not necessarily shorter than with the standard open approach technique. The main advantages of the minimally invasive approach are easier closure and the lower exposure to contamination.


Authors’ declaration of interests No conflicts of interest have been declared.


Ethical animal research No experimental animals were included in the study.


Authorship


F. Rossignol performed all surgeries and contributed to the preparation of the manuscript. O. Brandenberger assisted in one surgery and wrote the manuscript. S. Bartke, T. Van Bergen and A. Vitte all assisted in one surgery. All authors have approved the final version of the manuscript.


Manufacturers' addresses


1Ethicon, Issy Les Moulineaux, France. 2Arthrex, Lezennes, France. 3Kraft, Kraft Horse Walker, Frankenhardt-Hornhardt, Germany.


References


Auer, J. and Lischer, C. (2012) Arthrodesis techniques. In: Equine Surgery. Eds: J. Auer and J. Stick, Elsevier, Saunders, St.Louis, MO, USA. pp 1139-1141.


Barber, S.M., Panizzi, L. and Lang, H.M. (2009) Treatment of carpometacarpal osteoarthritis by arthrodesis in 12 horses. Vet. Surg. 38, 1006-1011.


Barr, A. (1994) Partial carpal arthrodesis for multiple carpal fractures and subluxation in a pony. Equine Vet. Educ. 6, 255-258.


Carpenter, R.S., Goodrich, L.R., Baxter, G.M., Joyce, J. and Wallis, T.W. (2008) Locking compression plates for pancarpal arthrodesis in a thoroughbred filly. Vet. Surg. 37, 508-514.


James, F.M. and Richardson, D.W. (2006) Minimally invasive plate fixation of lower limb injury in horses: 32 cases (1999-2003). Equine Vet. J. 38, 246-251.


Levine, D.G. and Richardson, D.W. (2007) Clinical use of the locking compression plate (LCP) in horses: a retrospective study of 31 cases (2004-2006). Equine Vet. J. 39, 401-406.


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