Covered femoral head area width

The covered femoral head area width 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 measurement is usually made using medical image processing software. The diameter of the femoral head is drawn perpendicular to the dorsal acetabular edge: on this line, the width of the dorsal acetabulum that covers the femoral head is measured and represents the covered femoral head area width.