Relationships of hip joint volume ratios with degrees of joint laxity and degenerative disease from youth to maturity in a canine population predisposed to hip joint osteoarthritis

Objective—To assess relationships of acetabular volume (AV), femoral head volume (FV), and portion of the femoral head within in the acetabulum (FVIA) with each other and with degrees of hip joint laxity and degenerative joint disease from youth to maturity in dogs predisposed to developing hip joint osteoarthritis (OA). Animals—46 mixed-breed half- or full-sibling hound-type dogs. Procedures—The distraction index (DI), AV, FV, FVIA, and degree of osteoarthritis (OA score) were quantified in 1 hip joint at 16, 32, and 104 weeks of age. Relationships among variables were evaluated within and between ages. Ratios corresponding to OA scores were compared within ages. Differences among 16-week ratios corresponding to 32-week OA scores and among 16- and 32-week ratios corresponding to 104-week OA scores were evaluated. Results—Significant positive relationships existed between FV and AV across ages as well as between FVIA/FV and FVIA/AV and between DI and OA score across and within most ages. Such relationships also existed within these variables across most ages. Negative relationships of DI and OA scores with FVIA/FV and FVIA/AV within and among all ages were significant. Sixteen-week AVs, FVs, and FVIAs were greater and FV/AVs and OA scores were less than 32- and 104-week values. The 32-week FVIA/FV was less than 16- and 104-week values, and the 32-week FVIA/AV was less than the 104-week value. The FVIA/FV and FVIA/AV were lower and the DI was higher with higher OA scores within and among most ages. Conclusions and Clinical Relevance—Structural volumes in lax canine hip joints changed predictably relative to each other during growth, despite degenerative changes. Measures developed in this study may augment current diagnosis and treatment strategies for hip dysplasia in dogs.