PLANTAR APONEUROSIS AND INTERNAL ARCHITECTURE OF BALL OF FOOT

Abstract

The ball of the human foot was investigated by dissection of fixed and fresh specimens and by histological examination of feet from fetuses aged 4-6 mo. The ball can be divided into 3 transverse areas, each with a different mechanical function: an area proximal to the heads of the metatarsals in which the retinacula cutis are developed into a series of transverse bands, and in which the deep fibers of the plantar aponeurosis form 10 sagittal septa connected to the deep transverse metatarsal ligament and the proximal phalanges of the toes; an area below the heads of the metatarsals in which vertical fibers from the joint capsules and the fibrous flexor sheaths form a cushion below each metatarsal head, and in which fat bodies cover the digital nerves and vessels and their passage between the cushions; and a distal area which comprises the interdigital web. The superficial fibers of the plantar aponeurosis are inserted into the skin of this distal area, and deep to them the plantar interdigital ligament forms a series of transverse lamellae connected to the proximal phalanges by a mooring ligament. When the metatarsophalangeal joints are extended, the fibers of the 3 areas are tensed and the skin is anchored firmly to the skeleton. A concentration of Pacinian corpuscles is found along the digital nerves in the intermediate, weight-bearing area.