A retrospective-prospective study has documented 54 cases of moderate to severe hip dysplasia, with varying degrees of shallowing of the acetabulum, flattening or loss of the femoral head, widening or loss of the femoral neck, and curvature of the femur, in northern koalas (Phascolarctus cinereus adustus) in the San Diego Zoo collection. For the retrospective study, historic radiographs were examined where available. For the prospective study, three standard views (ventrodorsal extended, ventrodorsal frogleg, and lateral extended) were used. A scoring system was developed using four areas (acetabulum, femoral head, femoral neck, and femur) and ranges of 0 to 5 (0 = not affected, 5 = severely affected) for a total score out of 40. Scores were graded as follows: Excellent = 0–2, Mild = 3–6, Moderate = 10–19, Severe = 20+.
Twenty-nine koalas were graded as severe, 25 koalas as moderate, 38 koalas as excellent or mild. Preliminary examinations of pedigree charts were inconclusive due to multiple missing data points. Preliminary reports of serum vitamin D levels appear low (normal values from free-ranging koalas are pending). Affected koalas may or may not demonstrate gait abnormalities. Mild to severe degenerative joint disease may develop and symptoms may be alleviated with glucosamine/chondroitin sulfate (half a capsule PO SID [Cosequin® DS, Nutramax Laboratories, Inc., Edgewood, MD 21040 USA]) for mild to moderate clinical cases, plus non-steroidal anti-inflammatory drugs (meloxicam, 0.1–0.2 mg/kg, PO SID [Metacam® Oral Suspension; Boehringer Ingelheim Vetmedica, Inc., St. Joseph, MO, 64506-2002 USA]) long term for severe clinical cases.
The authors thank the many veterinarians, veterinary technicians, keepers, and koalas at the Zoological Society of San Diego who have contributed to this study.