Accessory carpal bone fractures are less common in horses than other fractures of the carpus. Lameness is typically acute and severe, and there may be synovial effusion in the carpal sheath and, less commonly, the radiocarpal joint. Radiography confirms the diagnosis. These fractures are typically treated conservatively; however, if the fracture is articular and fragmented, surgical removal of the fragments has been performed. Fibrous union might enable a horse to return to athletic activity.
Subchondral bone damage is common in racehorses and can precede slab fractures of the third carpal bone. Clinical signs include lameness, decreased performance, and effusion of the middle carpal joint. Horses typically improve with intra-articular analgesia of the middle carpal joint. A skyline-view radiograph is critical for diagnosis and typically shows lysis and sclerosis in the third carpal bone (typically, radial facet). The treatment of choice is arthroscopic removal of the abnormal cartilage and subchondral bone.
Intercarpal ligament injuries in horses most commonly involve the medial palmar intercarpal ligament, but they can involve the lateral palmar intercarpal ligament. A typical presentation is synovitis and capsulitis unresponsive to therapy, or the presence of carpal chip fragments with an untoward amount of lameness. Diagnosis is made by arthroscopic examination, and treatment is arthroscopic debridement of the torn fibers. Prognosis depends on the extent of tearing, as well as the absence or presence of concurrent subchondral bone damage.
Exostoses or osteochondromas in horses can arise on the caudal aspect of the distal radius metaphysis and can cause carpal sheath tenosynovitis and lameness. Diagnosis is generally made by radiographic examination; however, ultrasonographic examination can be helpful to define the presence of soft tissue injury. Both conditions can be treated successfully via tenoscopy of the carpal sheath, with removal of the protruding mass, as well as identification and debridement of concomitant damage to the deep flexor tendon. The prognosis is good but depends on the extent of soft tissue damage.
