Lateral hindfoot instability treated with the Evans tenodesis: a biomechanical analysis.

The stabilizing effect of the Evans tenodesis on movements in the tibiotalocalcaneal joint complex was studied in 10 amputation specimens, using a kinesiologic testing device. The tenodesis was tested following solitary lesion of the anterior talofibular ligament and after combined lesions of the anterior talofibular and calcaneofibular ligaments. All tenodeses were performed with the joint complex in the neutral position. Regardless of the extent of ligamentous damage, the tenodesis frequently restricted adduction and internal rotation to a level below that recorded at intact ligaments. Instability in external rotation in the joint complex and anteroposterior laxity of the talus were never completely reconstructed, regardless of what degree of flexion in the joint complex the tenodeses were tested. The study demonstrates that, if performed with the tibiotalocalcaneal joint complex in the neutral position, the Evans tenodesis cannot reconstruct normal hindfoot kinematics, irrespective of the extent of ligamentous damage. However, severe instability in adduction and internal rotation, both part of clinical supination, were effectively prevented by the tenodesis.