Conditions affecting the carpal sheath of Thoroughbred horses

The presentation is based on the author’s experiences with diagnostic and surgical tenoscopy of the carpal sheath of the digital flexor tendons (carpal sheath) in Thoroughbred horses in training. This has expanded the list of differential diagnoses associated with tenosynovitis of the carpal sheath and when correlated with diagnostic imaging provided by Gaynor Minshall has led to the development of a good level of nonsurgical/ preoperative assessment of clinical cases. The findings have been published in a recent series of papers [1–4]. The data will be updated to include cases detailed in Table 1.

The bullet point conclusions may be summarised as:
• Caudal distal radial osteochondromata are a common developmental anomaly in young racing Thoroughbreds. The most plausible aetiology is aberrant translocation of physeal chondrocytes. Most occur in the mediolateral middle one-third of the metaphysis. Clinical signs result from impingement on the deep digital flexor tendon and subsequent synovitis; both are unrelated to the size of the osteochondroma. Tenoscopic removal of the osteochondroma and torn tendon tissue carries a good prognosis for return to training and racing. Recurrence is rare.
• Tears of the radial head of the deep digital flexor appear to be avulsions from the prinicipal (conjoined humeral and ulnar) tendon. Lameness is usually mild to moderate. Distension of the carpal sheath is consistent but of variable degree. Ultrasonographic predictability is good. Tenoscopic removal of the torn and extruded tissue carries a good prognosis for training and racing. […]