Acetabular index angle

The acetabular index angle is a measurement used to assess the steepness of the weight-bearing surface of the acetabulums. It is used to score coxofemoral dysplasia. The acetabular index angle is determined from a ventrodorsal radiograph of the hips. The dog is placed dorsal recumbency and the pelvic limbs are extended caudally, the femurs are parallel to each other. Positioning is considered satisfactory if :

• the pelvis is symmetrical (iliums and obturator foramina are symmetrical)

• the femur cortex pass through the middle of the sesamoid bones of the gastrocnemius muscle

• the patellas are centered on the trochlea of femur.

The acetabular index angle is the angle formed between a line connecting the lateral and medial extremities of the sclerotic projection of the acetabulum (acetabular sourcil slope) and a line perpendicular to the ilac axis.

Mostafa et al (2022) measured the following acetabular index angle in adult Labrador Retrievers (mean ± SD (range)).

• Normal hip joints: 8.6 ± 4.1 (7.8–9.3)

• Near normal hip joints: 7.8 ± 3.3 (6.7–8.9)

• Mild hip dysplasia: 11.1 ± 3.9 (9.9–12.3)

• Moderate hip dysplasia: 16.7 ± 8.1 (14.7–18.7)

• Severe hip dysplasia: 27.8 ± 18.4 (23.6–32.1)