Computed tomographic evaluation of growth-related changes in the hip joints of young dogs

To evaluate changes in canine hip joint characteristics during growth via computed tomography (CT) and compare CT features of hip joints with and without laxity in young dogs placed in 2 imaging positions.

21 dogs (42 hip joints).

From 2 to 12 months after birth, CT examinations of the acetabulum of each hip joint in simulated normal standing and simulated weight-bearing positions were performed monthly for all dogs. Acetabular angle, dorsal acetabular rim angle (DARA), and femoral head diameter (FHd) were analyzed as skeletal variables; the lateral center edge angle (LCEA), dorsolateral subluxation (DLS) score, and center distance (CD) index were analyzed as joint laxity variables. At 12 months, all dogs underwent the Ortolani test to as-sess hip joint laxity.

Hip joint laxity was detected in 5 dogs (10 joints) at 12 months of age; from 2 months, the acetabular angle and FHd increased and DARA decreased significantly until 5 months and the LCEA and DLS score increased significantly until 6 months. In nonlax hip joints in both positions, the CD index decreased significantly until 4 months of age and be-came stable thereafter. In lax hip joints, the CD index increased from 4 through 12 months; between 8 and 12 months, these changes were significantly greater in the weight-bearing position than in the standing position.

Results suggest that CT-detected abnormalities in the DARA and CD index during body weight loading might be useful indicators of hip dysplasia in 2- to 6-month-old dogs.