[Development and biomechanics of the talocrural joint].

We have studied the development of talocrural joint in fetuses, newborns and children. The results of the microscopical, anatomical and biomechanical studies are as follows: 1. The distal extremities of tibia and fibula are joint not only by the distal part of the tibiofibular syndesmosis, but also by an articulation (articulation tibiofibularis distalis). Its articular cavity communicates with the cavity of the talocrural joint and is visible on its arthrographic pictures. This articulation enables the mutual shift and rotation between distal extremities of tibia and fibula-during the plantar flexion fibula turns and shifts round tibia anteriorly, by the dorsal flexion posteriorly. 2. We recommend to preserve the possibility of mutual movements of tibia and fibula in all cases of the surgical treatment of talocrural injuries. 3. Analysis of prostheses of talocrural joint showed why they cannot be functionally successful. They do not respect the physiological movements, the small articulations of tarsus are overloaded. Pain, arthrosis and functional collapse results in these small articulations, because the prostheses change the axis of movements and the biomechanics at all. 4. We have defined conditions for a successful talocrural prosthesis. 5. Study of the topography of the attachment of the Achilles tendon showed, that it develops medially from the axis of the extremity and therefore rotates in the fetus the foot in the equinovarus position. The tendon shifts till the axis during the second half of fetal life. When this shift is temporarily stopped or slown down, the syndrome of pes equinovarus congenitus develops. We recommend the modification of the surgical treatment of pes equinovarus congenitus: transposition of the Achilles tendon in the axial position.