Biomechanical tensile strength analysis for medial patellofemoral ligament reconstruction.

BACKGROUND: 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 human cadaver knees were used for the analysis of five 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, IS-F/IS-P). Each method was examined six times, each using a new human gracilis allograft. The force necessary for 50% patellar displacement and 100% patellar displacement were recorded for each method. Additionally, we examined the peak force to fixation failure for all methods. Patella dislocation or loss of fixation was considered failure.

RESULTS: SC-F/SC-P, IS-F/SC-P, and SC-F/IS-P required force to failure greater than that of the native MPFL. 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: SC-F/SC-P, IS-F/SC-P, and SC-F/IS-P fixations were found to be stronger than the native MPFL, with the strongest being SC-F/IS-P.