Dorsal acetabular sector angle

The dorsal acetabular sector angle is a measurement used to assess the anatomy of the hip joint in dogs, in particular the lateral slope of the acetabular roof. It is determined from a 2D CT images in a transversal plane. The dog is placed in dorsal recumbency with hip joints extended, adducted, and rotated slightly internally. Measurement is performed on three contiguous images that include an acetabular fossa, a well-defined acetabular sourcil, a round head of femur, and a fovea capitis.

A line is drawn on the horizontal pelvic axis defined as a line through the center of both femoral heads. Depending on authors, the center of the femoral heads is defined as the center of the best fit circle delimiting the femoral head (Andronescu et al 2015) or the midpoint of a line drawn perpendicular to a straight line that connects the caudal articular cartilage margins on the dorsal and ventral articular surfaces of the femoral head (Lopez et al. 2008). The dorsal acetabular sector angle is the angle between a line that extends dorsally from the center of the femoral head to the dorsolateral border of the lunate surface and the horizontal pelvic axis.

Lopez et al (2008) found that the dorsal acetabular sector angle in adult mixed-breed dogs with laxity of the hip joints was 75,9 +/- 6,13° (range 28,2 - 91,4)

Andronescu et al (2015) published the following results for dorsal acetabular sector angle in relation to osteoarthritis score:

• OA score 0: 86,85 +/- 7,68°

• OA score 1: 75,64 +/- 8,69°

• OA score 2: 69,78 +/- 6,87°

• OA score 3: 61,06 +/- 9,25°

Andronescu et al. (2015) published dorsal acetabular sector angle in 46 dogs with all osteoarthritis scores combined at each age:

• 16 weeks of age: 87.02 ± 7.83°

• 32 weeks of age: 82.01 ± 12.06°

• 104 weeks of age: 77.20 ± 13.38°