Second carpal bone slab fracture and subluxation of the middle carpal joint in a horse subsequent to arthrodesis of the carpometacarpal joint.
Authors: MacKay Angela V, Panizzi Luca, Sparks Holly D, Barber Spencer M
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Arthrodesis of the carpometacarpal (CMC) joint offers a potential solution for end-stage CMC osteoarthritis, but this case report documents a serious complication arising from the drilling technique commonly used to achieve fusion. A 12-year-old Quarter Horse underwent CMC arthrodesis using a fanning drill technique—inserting a 4.5 mm bit at three sites with 30–45° lateral fanning and 5–10° longitudinal angulation to destroy articular cartilage—but presented with severe lameness just two weeks post-operatively, with imaging revealing a slab fracture of the second carpal bone and middle carpal joint subluxation. The aggressive cartilage destruction required to achieve CMC fusion appears to have compromised the structural integrity of adjacent carpal bones, destabilising the middle carpal joint and ultimately resulting in euthanasia due to poor prognosis. This case highlights a critical trade-off in CMC arthrodesis technique: whilst sufficient articular surface destruction is necessary for fusion, the fanning approach may exceed the load-bearing capacity of surrounding carpal structures, particularly in mature horses where bone quality may already be compromised. Practitioners should weigh the potential benefits of CMC arthrodesis against the risk of catastrophic complications, and consider whether alternative techniques or more conservative management of CMC-OA might be preferable in horses with marginal bone quality or advanced degenerative changes.
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Practical Takeaways
- •If considering CMC arthrodesis with drilling techniques, surgeons must carefully balance cartilage destruction against maintaining carpal joint stability and bone integrity
- •The fanning drilling technique at aggressive angles may be too destructive and risks secondary complications in adjacent carpal joints
- •CMC arthrodesis patients should be monitored closely post-operatively for signs of lameness, as serious carpal complications can develop rapidly within 2 weeks
Key Findings
- •Arthrodesis of the CMC joint using a fanning drilling technique (30-45° in joint plane, 5-10° in long axis) resulted in slab fracture of the second carpal bone within 2 weeks post-operatively
- •The surgical technique caused subluxation of the middle carpal joint leading to severe lameness and poor prognosis
- •Excessive articular surface destruction with the fanning technique compromised joint stability and carpal bone integrity