Iliotibial band tenodesis: a new strategy for attachment.

We investigated the changes in distance between Gerdy's tubercle on the tibia and points on the posterior two thirds of the lateral surface of the lateral femoral condyle and adjacent lateral femoral shaft in 15 cadaveric knees. A three-dimensional digitizer was used to quantify motion of the knee during flexion ranging from full extension to 120 degrees of flexion. Four load states were applied: internal, external, and neutral rotation, and quadriceps muscles loads based on one third of values in the literature for maximal isometric quadriceps muscles moments. The femoral location most isometric to Gerdy's tubercle was found to be strongly influenced by the load state. A 1.0 cm wide iliotibial band tenodesis was modelled by five straight lines arising from Gerdy's tubercle and attaching to a simulated washer at the junction of the lateral femoral condyle and shaft. Using this model and the motion data obtained from the cadavers, we investigated the effects of quadriceps muscles loading and external rotation of the knee on changes in the distances between these tibial and femoral attachments for each of the five lines. A 180 degrees twist modelled into the tenodesis significantly reduced the range of changes in distance (difference between the largest and smallest changes in distance among the lines for a given angle of flexion) for both of these load states. Therefore, a 180 degrees twist in the tenodesis can enhance isometry among the fibers of the tenodesis. This implies that a 180 degrees twist can enhance load sharing among the fibers of the tenodesis and, therefore, enhance the overall strength of the tenodesis.