[Arthrodesis of the ankle by a tibiometatarsal frame.]

The authors submit a biomechanical analysis of the most frequently used methods of stabilization of arthrodesis of the ankle joint. From the biomechanical aspect they describe the foot as a two-arm lever; on its shorter arm (rotation centre of the talus insertion of the Achilles tendon) acts the muscular force, i. e. plantiflexion with a value of 640 kg, and on its longer arm (rotation centre of the talus - forefoot) acts the muscular force in the sense of dorsiflexion with a value of 140 kg. These forces in particular in the sense of plantiflexion act after fusion of the ankle against the stability of the arthrodesis. The relatively small success of some methods of arthrodesis is according to the authors the result of an inadequate solution of biomechanical relations. Consistent with clinical findings in a group of 21 arthrodeses of the ankle, the authors consider adequate only surgical procedures and configurations of devices for external fixation which along with stabilization of the arthrodesis neutralize flexion forces which act on the forefoot. Hitherto used configurations of external fixation - Charnley's compression clamp, modification of the AO clamp and triangular fixation do not resolve this demand fully. From the biomechanical aspect fixation of the talus by Ilizarov's apparatus is quite satisfactory but its implementation is technically pretentious and the authors recommend it only for the solution of complicated cases. The authors recommend a new simple method of arthrodesis by means of a tibiometatarsal frame. The proximal nail inserted into the diaphysis of the tibia is connected with a distal nail inserted into the base of metatarsal bones by a simple frame fixation. The suggested method was tested on pathological specimens. The authors demonstrate the first clinical results in 6 patients where firm healing of the desis was achieved precisely in the required angle of 90 degrees . On the other hand, in patients of a group where arthrodesis was performed by another method without stabilization of the forefoot the authors observe frequently undesirable plantiflexion. Key words: arthrodesis of the ankle, biomechanics of arthrodesis, tibiometatarsal osteosynthesis.