Acetabulum pedis. Part I: Talocalcaneonavicular joint socket in normal foot.

The socket of the talocalcaneonavicular ball and socket joint in the foot is termed acetabulum pedis (AP). Observations of 72 feet from necropsies of stillborns or deceased newborns are the basis of our architectural description of AP. It has five walls: the roof or superior wall, the floor or inferior wall, the bottom or anterior wall, the medial wall, and the lateral wall. Variations in the tridimensional situation of the anterior and middle articular facets of the calcaneus modify the acetabular floor area. The same is true of the variations in position of the ligaments in both the acetabular floor and the medial wall. These modifications of the acetabular floor and medial wall areas can change the shape of the foot.