Introduction

Complicated articular fractures, severe arthritis and luxation of the glenohumeral joint may necessitate arthrodesis of the scapulohumeral joint. There is paucity of data concerning clinical outcome of historically reported techniques. This case series describes surgical technique and outcome for six dogs with intractable thoracic limb lameness attributed to shoulder pathology.

Materials and Methods

A craniolateral approach to the scapulohumeral joint was employed. Osteotomies of the glenoid and humeral head were performed with a microsaggital saw creating two parallel surfaces for joint fusion at approximately 120°. Two k-wires were driven across the excision site to approximate appositional alignment. A plate was contoured such that screws would engage the scapula at the bisecting angle of the spinous process and body cranially and such that the distal extent of the plate did not migrate from the cranio-lateral aspect of the proximal humerus. The osteotomised humeral head was morselised to provide cancellous bone graft. Screws through the proximal humeral metaphysis were driven across the osteotomy into the distal scapula.

Results

Reasons for patient presentation included intractable shoulder pain secondary to osteoarthritis (n=2) or ligament injury (n=1), intra-articular fracture (n=2), or luxation (n=1). Mean age at surgery was 8.72 years (range 3-12). Mean weight was 20.34kg (range 11.2kg to 30.0kg). The mean angle of fusion was 119° (range 117-122°). Complications included delayed union (n=2), plate breakage (n=1) and wound infection (n=2). Progression of osseous union and time to lameness resolution was 33-64 days (n=4), and osseous union with pain free limb use was evident at 95 days in the patient affected by plate breakage and delayed union. 4/5 patients had mechanical lameness. One case was euthanased subsequent to infection. Implants included a 3.5mm dynamic compression plate (n=3), 3.5 mm reconstruction plate (n=2) and SOP^TM plate (n=1). During revision surgery a second SOP^TM could be stacked over the original plate; healing was augmented with Colloss^TM and proved successful.

Discussion

Scapulohumeral arthrodesis subjectively provides good results for return to pain free ambulation. Implant loosening or failure can occur at the scapula or with inadequate bone stock buttress such as might occur with fracture. Anecdotally, use of the SOP^TM plate allowed easier plate contouring and maximised stability of the repair in comparison to conventional plating. Colloss^TM is a useful adjunct to encourage arthrodesis even in the absence of autogenous cancellous bone graft.