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Médecine et chirurgie du pied

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The “coxa pedis” Volume 22, issue 4, Décembre 2006

Authors

The “coxa pedis” corresponds to the talocalcaneonavicular joint. This is a ball-and-socket joint with an epiphysis represented by the head and neck of the talus and a socket in the form of a bony, fibrous, cartilaginous cavity composed of the posterior surface of the navicular and the surfaces of the sustentaculum tali and large apophysis of the calcaneus, constituting the anterior subtalar joint. Sometimes divided by a groove, they usually form a single joint.

The joint area between the navicular, sustentaculum tali and the large apophysis of the calcaneus is completed by a genoid fibrocartilage reinforced plantarly by the plantar calcaneonavicular ligament. This extends from the base and anteromedial border of the sustentaculum tali to its distal insertion on the tubercule and inferoposterior edge of the navicular bone. It corresponds to the bottom of the coxa pedis and subtends a true cartilage-covered glenoid in an articular relationship with the inferomedial side of the head of the talus, between the navicular and calcaneal sides. Its inclusion of proprioceptive corpuscles suggests that the coxa pedis has a cybernetic receptorial function.

In the 16th- to 17th-week embryo, the talonavicular and subtalar joints are differentiated in a single ball-and socket joint.

The wider meaning of coxa pedis expresses the functional significance of a structure whose anatomical, evolutionary and clinical features are similar to those of the hip joint, with which, together with the knee, it integrates functionally in the lower limb.

Enarthrodial differentiation proximal and distal to the lower limb, with the knee in between, is the biomechanical premise for the rotatory mechanisms (plane at right angles to the segmentary axes of the limb) indispensable for securing its stabilisation in the weight-bearing phase closed kinetic chain), as well as for the succession of intercurrent mechanisms in the frontal (lateral translation of the load in initiation of the weight-bearing phase) and sagittal planes (oscillating phase).

Particular reference is made to degenerative glenopathy and peritalar destabilisation syndrome. Recent reference to the coxa pedis (1999) appears in the updated Encyclopédie Medico-Chirurgicale, edited by Biga, Moulies and Mabit.