Overconstraint Associated With a Modified Lemaire Lateral Extra-Articular Tenodesis Is Decreased by Using an Anterior Femoral Insertion Point in a Cadaveric Model.

ABSTRACT

PURPOSE: To investigate tibiofemoral knee kinematics when shifting the femoral insertion point of the modified Lemaire lateral extra-articular tenodesis (LET) anterior to the lateral epicondyle. METHODS: Six fresh-frozen human knee joints were tested on a test bench in the following states (1) native, (2) anterolateral insufficient, (3) original Lemaire (oLET; insertion point 4 mm posterior and 8 mm proximal to the epicondyle), (4) anterior Lemaire (aLET; insertion point 5 mm anterior and 5 mm proximal to the epicondyle). Internal tibial rotation was statically investigated under an internal tibial torque of 5 Nm in 0°, 30°, 60°, and 90° of flexion. Anterior translation was statically investigated during a simulated Lachman test with an anterior translational force of 98 N. Additionally, the range of internal tibial rotation and anterior translation were dynamically investigated by a simulated pivot-shift test. Tibiofemoral kinematics were measured using an optical 3D motion analysis system. RESULTS: The aLET showed an internal tibial rotation comparable to the native state for all tested flexion angles except 90° (0° P = .201; 30° P = .118; 60° P = .126; 90° P = .026). The oLET showed an internal tibial rotation below the values of the native state for all tested flexion angles indicating an overconstraint (0° P = .003; 30° P = .009; 60° P = .029; 90° P = .029). Direct comparisons between aLET and oLET showed a significantly decreased overconstraint at 0° and 30° of flexion (P = .001 and P = .003, respectively) when using the aLET. No differences in anterior translation and internal tibial rotation were found between the oLET and aLET during simulated Lachman and pivot-shift test (P > .05), approximating the native state. CONCLUSIONS: An anteriorly shifted LET insertion point restored internal tibial rotation after anterolateral insufficiency to the native state while decreasing the overconstraint of internal tibial rotation induced by an LET using the originally described insertion point for small flexion angles ≤30°. CLINICAL RELEVANCE Using an LET insertion point anterior to the epicondyle was recently reported to lower the risk of tunnel interference and has now been shown to restore internal tibial rotation effectively in vitro in the course of the present study. Concerns of overconstraining internal tibial rotation are not diminished by this technique, but using an anterior insertion point helps to decrease overconstraint.