Shoulder Dysplasia in Koalas (Phascolarctos cinereus) at San Diego Zoo

Abstract

A radiographic study documented shoulder dysplasia (n = 43), with varying degrees of malformation of the supraglenoid and infraglenoid tubercles and the coracoid process, shallowing or loss of the glenoid cavity, flattening or loss of the humeral head, malformation of the greater and lesser tubercles, loss of the intertubercle groove, and humeral diaphyseal abnormalities, in northern koalas (Phascolarctos cinereus) in the San Diego Zoo (San Diego, California, USA) colony. Retrospectively, historic radiographs (n = 38) were examined where available. Prospectively, three standard views (lateral extended arm, ventrodorsal cranially positioned arms, and ventrodorsal caudally positioned arms) were imaged (n = 25). In all radiographs, shoulders were graded as normal, or mildly, moderately, or severely dysplastic. Although affected koalas typically do not exhibit clinical signs, degenerative joint disease may develop and clinical signs treated with nonsteroidal anti-inflammatory drugs. Where shoulder and hip radiographs were both available (n = 60), 92% of individuals had correlation between the degree of shoulder and hip dysplasia.