Abstract

Various ligamentoplasties are available allowing formation of new proprioceptive chains in cases of failure of physiotherapy. Most of these plasties sacrifice half or all of the fibulolateral tendon, causing stiffness of the subtalar joint. This is a too serious complication to accept for simple tibiotarsal instability: hence the importance of preoperative assessment to determine the type of plasty most appropriate for each type of instability. We have designed an adjustable boot, linked to a dynamometer by means of a metal rod, with a radiological marker attached to the boot, to measure subtalar mobility preoperatively. We studied this boot with the ankles of 15 cadavers, on which we sectioned the ligaments of the tibiotarsal and subtalar joints to measure the degree of laxity. Accurate assessment is possible if the mobility of the tibiotarsal and subtalar joints is measured in cases of acute sprain, in particular in isolated lesions of the anterior talofibular ligament and lesions of the calcaneofibular ligament; or in chronic instability, including: purely tibiotarsal, purely subtalar, and mixed types. This method allows optimal therapeutic choice.