Surgical treatment of scapulohumeral subluxation in an alpaca (Vicugna pacos) using osteotomy of the acromion, open reduction and extracapsular tension sutures.

CASE HISTORY AND CLINICAL FINDINGS

A 3.3-year-old male alpaca, weighing 60 kg was referred for investigation of a severe left forelimb lameness of 4 weeks duration. A scapulohumeral subluxation had been diagnosed radiographically by the referring veterinarian.

CLINICAL FINDINGS AND DIAGNOSIS

Based on clinical, ultrasonographic and radiographic findings the diagnosis of cranio-lateral subluxation of the left humeral head was confirmed. In addition, a full thickness lesion (approximately 1×1 cm) of the articular cartilage on the caudomedial aspect of the humeral head was diagnosed by arthroscopy.

TREATMENT AND OUTCOME

Treatment included open reduction with internal fixation. Severe muscle contraction and local tissue fibrosis around the scapulohumeral joint (SHJ) required osteotomy of the acromion 3 cm proximal to the distal acromial edge, to allow adequate access. Internal stabilisation was achieved by placing tension band sutures between one cortical screw in the scapular neck and two cortical screws, with washers, craniolaterally on the greater tubercle of the humerus. Post-surgery, a carpal flexion sling was applied with the carpus maintained in 70° flexion for 4 weeks to avoid postoperative weight-bearing. An exercise programme was started 8 days after surgery and continued for 12 weeks. The alpaca had an uneventful postsurgical recovery and showed no lameness after 8 weeks. The long-term outcome was excellent; 21 months after surgery the alpaca was sound and the range of movement of the left SHJ was equal to the right SHJ.

CLINICAL RELEVANCE

Even in this chronic case of subluxation of the SHJ of 4 weeks duration, surgical treatment using osteotomy of the acromion, open reduction and internal fixation with extracapsular scapulohumeral tension sutures resulted in an excellent long-term outcome in this alpaca, despite the presence of a cartilage lesion.