Six cases of comminuted fracture of the accessory carpal bone where dorsoproximal fragments within the palmar antebrachiocarpal joint were removed by arthroscopy in the standing horse.

Background: Accessory carpal bone fractures in the horse often result in a fracture configuration described as frontal plane, complete fractures, with dorsoproximal fragmentation. Conservative management of accessory carpal bone fracture type has been associated with good outcomes. Horses that do not return to soundness are highly likely to develop osteoarthritis of the carpal joints, carpal sheath pathology, or both. The removal of these fragments to ameliorate osteoarthritis is reported in the literature. Objective: To describe a novel technique to remove dorsoproximal accessory carpal bone fracture fragments from the palmar aspect of the antebrachiocarpal joint in the standing horse. Study design: Retrospective case series of six horses that underwent standing carpal arthroscopy between 2016 and 2025. Methods: Six horses with comminuted accessory carpal bone fractures underwent standing arthroscopic removal of dorsoproximal osteochondral fragments within the palmar antebrachiocarpal joint. The antebrachiocarpal joint was anaesthetised and the subcutaneous tissue infiltrated using mepivacaine hydrochloride. A suction punch forceps and a soft tissue motorised ablator were used to dissect the soft tissue attachments. A motorised bone burr was used to remove or debulk the fragments. Results: All horses recovered well from surgery and were stabled for 3 months. In all six cases, the fracture healed by fibrous union. 5 of 6 horses returned to athleticism, often within 12 months from injury; one horse was retired for breeding purposes. Main limitations: Retrospective nature of study, small sample size, varying degrees of pathology present. Conclusions: This is a novel technique that may be suitable in selected cases of accessory carpal bone fracture to ameliorate antebrachiocarpal joint osteoarthritis. Performing the surgery standing negated the need for general anaesthesia. The described technique may encourage surgeons to adopt standing removal of fragments earlier in the healing process which may improve the outcome in horses with this fracture configuration.