Biomechanical tensile strength analysis for medial patellofemoral ligament reconstruction

Abstract Purpose Medial patellofemoral ligament (MPFL) reconstruction is a surgery for acute and chronic dislocating patella. Several surgical techniques have been described. No biomechanical study has compared suture anchors, interference screws, and suspensory cortical fixation for MPFL reconstruction using human gracilis allograft. Methods Twelve (six matched pairs) fresh human cadaver knees were used for the analysis of five different MPFL reconstruction techniques on the femur (F) and patella (P): suspensory cortical (SC), interference screw (IS) and suture anchor (SA) fixation (SC-F/SC-P, SC-F/IS-P, SC-F/SA-P, IS-F/SC-P and IS-F/IS-P). Each method was examined six separate times with each using a new human gracilis allograft. The forces that were necessary for 50% patellar displacement (subluxation) and 100% patellar displacement (dislocation) were recorded for each method. Additionally, the peak force to fixation failure for all methods was examined. Patella dislocation or loss of fixation was considered failure. Results Three methods required force to failure greater than that of the native MPFL: SC-F/SC-P, IS-F/SC-P and SC-F/IS-P. The SC-F/IS-P required the largest force to failure. The SC-F/SA-P fixation technique required significantly less force to failure ( P < 0.05) than the native MPFL, and significantly less force to failure ( P < 0.05) than all four other fixation techniques. All methods of fixation employing an interference screw failed secondary to graft pullout at the interference screw-bone interface. Methods employing suture anchors and two suspensory cortical fixations failed at the graft-suture anastomosis. Conclusion The three fixations that were found to be stronger than the native MPFL were SC-F/SC-P, IS-F/SC-P and SC-F/IS-P, with the strongest method being SC-F/IS-P.