[Long-term Results of Arthrodesis of the Talocrural Joint.]

The authors evaluate a group of 19 arthrodeses of the talocrural joint in 16 patients after a mean interval of 6 years and three months following arthrodesis (operation). They demonstrate that the hitherto used method of evaluation of the position of the foot after arthrodesis of the ankle - measurement of the tibiotalar angle, is insufficient and does not record the changes in function and shape distally from Chopart's joint, e. g. pes cavus. Some deformities of the foot can lead to an entirely afunctional arthrodesis even when from the theoretical aspect the tibio-talar angle of arthrodesis is correct. The evaluation from the lateral radiograph only is misleading, as the X-ray picture without the extreme position of dorsiflexion of the forefoot does not express the real position of the foot important from the functional aspect. The X-ray evaluation must be in relation to the position of the planta. The authors recommend therefore their own method of X-ray evaluation of the arthrodesis of the talus. In their opinion the position of the arthrodesis of the ankle is correct when during sustained dorsal flexion of the foot the connecting line of the plantar margin of the head of the 1st metatarsus and the plantar margin of the tuber calcanei and the tibial axis form an angle of 85 - 90 degrees . The authors describe this angle as the "functional angle of arthrodesis of the ankle". It can be measured during sustained dorsiflexion of the foot by means of an elastic longet-te. The functional results of arthrodesis of the talocrural joint were assessed by the authors by a Mazur ankle evaluation grading system. The authors demonstrate the importance of a correct position of the foot after arthrodesis in case-histories of some patients where already in case of desis of the foot in plantiflexion of 10 degrees , the arthrodesis was obviously inadequate from the functional aspect. After arthrodesis of the talocrural joint the range of motion of the forefoot is 10 - 15 degrees . It is therefore essential to perform the arthrodesis of the joint in a position so that the functional interval of the joint will be used as expediently as possible and standing and walking will be as close as possible to physiological burdening of the joint. This is possible only when the dorsal flexion of the foot will be between 3 and 5 degrees . In the authors' opinion the optimal position of arthrodesis is 3 - 5 degrees in dorsiflexion of the foot. This position makes possible not only a physiological position of the foot, but also walking barefoot and with a heel of 3.5 cm. Conversely arthrodesis of the talus in plantar flexion, in particular at > 10 degrees leads to overburdening of the forefoot and has a negative impact on the possible role of compensation mechanisms and the patient is able to move without difficulty only when wearing prosthetic shoes. Evaluation of the group of patients revealed also a relationship between the extent of mobility of the forefoot and the position of the arthrodesis. The extent of mobility of the forefoot is reduced with increasing deficit of dorsal flexion. The authors assume that this is the result of lower functional adaptation and a major role of degenerative changes of foot joints in arthrodesis performed in plantar flexion. Key words: arthrodesis of the talo-crural joint.