Dorsal femoral head coverage area index

The dorsal femoral head coverage area index (or dorsal acetabular femoral head coverage area index) is a measurement used to assess the anatomy of the hip joint in dogs. It quantifies the extent of lateral and dorsal coverage of the femoral head and is used to score coxofemoral dysplasia. It 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 dorsal femoral head coverage area index is calculated by dividing the covered femoral head area (A) by the overall femoral head area (B).

Mostafa et al (2022) measured the following dorsal femoral head coverage area index in adult Labrador Retrievers (mean± SD (range)):

• Normal hip joints: 0.60 ± 0.05 (0.59–0.6)

• Near normal hip joints: 0.55 ± 0.06 (0.53–0.57)

• Mild hip dysplasia: 0.49 ± 0.08 (0.47–0.51)

• Moderate hip dysplasia: 0.36 ± 0.10 (0.33–0.38)

• Severe hip dysplasia: 0.24 ± 0.10 (0.21–0.26)