Hip dysplasia can be diagnosed through palpation, radiography, computed tomography (CT), and magnetic resonance imaging (MRI). Radiography has been the gold standard for diagnosis but is limited by the lack of cartilaginous and bony detail. Standard radiographic measures of coxofemoral joint articulation have variable sensitivities. Three-dimensional (3-D) CT is routinely used in humans, has been studied in dogs, and is a powerful method of evaluating and quantifying structural changes in joints. This study evaluated the relationship between joint volume ratios (measured by 3-D CT) and the degree of joint laxity and degenerative disease (measured radiographically) from youth to maturity in 46 dogs. One hip joint in each dog was examined radiographically at 16, 32, and 104 weeks of age. A numeric score was calculated based on the films to characterize the level of degenerative joint disease present. A pelvic CT scan was performed and 3-D CT reconstructions of the hip joints were created. The joints were disarticulated by virtual analysis, and acetabular volume and femoral head volume were quantified. The results indicate that 3-D CT may provide a more sensitive window into the pathologic sequence of hip dysplasia and that the most significant changes occur between the ages of 16 and 32 weeks. 3-D CT imaging techniques may be useful in identifying anatomic changes that can affect diagnosis, prevention, and treatment of hip dysplasia in dogs.

Commentary:
Although they are fascinating and well presented in this article, volumetric joint analysis and 3-D CT are probably relegated to the veterinary academic setting at this time. These technologies remain beyond reach for most referral hospitals, let alone the private practice setting. With that said, 3-D CT creates a fascinating new window into the pathogenesis of canine hip dysplasia and may take us one more step toward better detection, prognosis, and treatment of this painful disease.—Heather Troyer, DVM, Diplomate ABVP

Relationships of hip joint volume ratios with degree of laxity and degenerative disease from youth to maturity in a canine population predisposed to hip joint osteoarthritis. D’Amico LL, Xie L, Abell LK, et al. AM J VET RES 72:376-383, 2011.