Mechanical contribution of the fibula to torsion stiffness in the lower extremity.

The role of the fibula in rotational stability of the lower extremity, taking into account the intact knee joint and tibia, to the best of our knowledge, has not been investigated. A cadaver study was designed to determine the torque transfer down the lower extremity, with and without the fibula. Six fresh, frozen human cadaver legs were used. The knee joint was left intact and the foot disarticulated. An external rotation up to 5 degrees , coupled with axial compression, was applied to the femur passing through the knee joint in extension and down the lower extremity to the fixed distal end, where torque (N m) was measured via a load cell. Each specimen was further tested with the fibula, cut 4 cm from the distal end, and finally with the entire fibula disarticulated at the proximal end and removed. To achieve 5 degrees rotation, torques reached 1.82 N m (SD, 0.66 N m). When the fibula was cut, the torque reduced a small yet significant amount of 5%. With the entire fibula removed, the torque reduction was significant and more pronounced at 11%. The fibula provided a small yet significant role in torsion stability. From this study, where the biomechanical characteristics of the fibula is explicated, it is hoped that this information will have use in further understanding the biomechanical role of the fibula, especially, in relation to the altered mechanics associated with lower limb pathology involving a deficient fibula. Copyright 2006 Wiley-Liss, Inc.