Biomechanical comparison of two medial patellofemoral ligament reconstruction techniques: Quadriceps tendon fixation versus single-tunnel patella fixation with gracilis autograft did not differ in load to failure and stiffness

Abstract

Background: The purpose of this study was to evaluate the ultimate failure load and stiffness of two patellar fixation techniques for medial patellofemoral ligament (MPFL) reconstruction: (1) quadriceps tendon fixation (QT), (2) single tunnel (STG) patella fixation with gracilis autograft.

Methods: A total of 16 fresh-frozen cadaveric knees (eight matched pairs) were randomized into two groups (QT vs. STG). The MPFL reconstructions were subjected to cyclic loading for 10 cycles to 30 N and then tested to failure at a constant displacement rate of 15 mm/min using a materials-testing machine (MTS 810 Universal Testing System). Failure mode, ultimate failure load and stiffness were recorded for each cadaveric specimen.

Results: There was no significant difference in mean ultimate failure load among groups (P = 0.35). The STG group failed at a mean ultimate load of 190.04 N [standard deviation (SD) 23.18] and the QT group failed at 206.24 N (SD 37.99). The STG group had a mean stiffness of 21.38 N/mm (SD 1.44). This was not significantly higher than the mean stiffness value achieved for the QT group at 20.36 N/mm (SD 1.3) (P = 0.19). In the QT group all reconstructions failed due to tendon rupture at the patella attachment. The reason for failure in the STG group was the graft-suture connection.

Conclusions: This cadaver study showed no statistically significant difference in biomechanical performance of the evaluated patella fixation techniques, in terms of maximum load to failure and stiffness. Both techniques are reliable in terms of biomechanical properties and could offer additional surgical solutions.

Keywords: Biomechanical evaluation; Cadaveric study; Medial patellofemoral ligament; Patella instability; Single-bundle reconstruction.