Texas Equine Veterinary Association

www.teva-online.org • Page 7 shouLDeR: PAthoLogIc conDItIons, tReAtment, AnD PRognosIs osteochondrosis Osteochondrosis (OC) occurs less frequently in the shoulder joint than other common locations in the horse. Lameness is typically noticed in horses at a young age (6 to 12 months of age) and can become apparent when horses are placed in work. Diagnosis is based on clinical exam findings and localization with intra-articular anesthesia. Radiographs are typically sufficient to diagnose most osteochondrosis lesions of the shoulder; however, subtle lesions can sometimes appear normal (Figure 3). If intra-articular pathology is highly suspected, diagnostic arthroscopy should be performed even in the absence of radiographic confirmation. The treatment of choice for osteochondrosis of the shoulder is arthroscopic surgery to remove cartilage flaps and debride abnormal subchondral bone. Lesions on the medial aspect of the humeral head can be inaccessible. Prognosis is highly dependent on lesion severity, lesion location, and presence of secondary osteoarthritis. If osteoarthritis is already present or the lesion is inaccessible, the prognosis for return to performance is poor. If lesions are present on both the humeral head and glenoid cavity, prognosis is poor. Subtle lesions have a good prognosis for return to performance. 4,5 supraglenoid tubercle fractures Supraglenoid tubercle fractures are often simple intra-articular fractures that involve the epiphysis of young horses that have not yet ossified the physis of the supraglenoid tubercle. Fracture is commonly associated with a traumatic event to the cranial portion of the shoulder. Overflexion of the shoulder leading to increased biceps brachii tendon (which originates on the supraglenoid tubercle) tension, has also been implicated as a cause of fracture. Lameness is acutely severe; however, rapid improvement is often noted leading to delayed diagnosis. Diagnosis is made based on clinical and radiographic examinations. In acute cases, firm digital palpation at the point of the shoulder can elicit pain. During lameness examination, a pronounced decreased anterior phase of the stride is almost always noted. In chronic cases, muscle atrophy of the shoulder is noted (Figure 4). On medial-to-lateral radiographic projections, the fracture fragment is displaced cranioventral (Figure 5). Concurrent evidence of osteoarthritis decreases the prognosis for return to function. Treatment is dependent on fracture duration and configuration. Conservative management is typically only suggested with very small fragments and in the presence of little to no shoulder joint involvement. 6 Contrast radiography can help determine the extent of joint involvement when determining whether to treat conservatively or surgically. Surgical options include fragment removal or fracture repair using lag screw and tension band application. In cases involving chronic fractures, fragment removal is the treatment of choice. Prognosis for return to use is dependent upon the amount of cartilage damage present at the time of surgery and the amount of the glenoid cavity removed. If secondary osteoarthritis is already present, the prognosis for return to function is poor. Of the few reports available, prognosis for return to function following fracture removal or internal fixation is fair, Figure 1: Normal mediolateral radiograph of the shoulder joint. Notice joint overlying the trachea. Figure 2: Skyline radiograph of the greater tubercle. This view allows for evaluation of the interubercular groove tubercle of the humers. Figure 3: Osteochondrosis lesion of the caudal humeral head (black arrow). The OC lesion was debrided arthroscopically and the horse was able to return to performance.

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