Cyclic Testing of 3 Medial Patellofemoral Ligament Reconstruction Techniques

BACKGROUND: Several techniques are available to secure the graft to the patella during medial patellofemoral ligament (MPFL) reconstruction. The biomechanical properties of these techniques remain unknown. PURPOSE: To compare the biomechanical properties of 3 MPFL patellar fixation techniques: bone tunnels (BT), PushLock anchors (PL), and tenodesis screws (TS). STUDY DESIGN: Controlled laboratory study. METHODS: Forty-five MPFL reconstructions were performed using 3 different reconstruction techniques (BT, PL, and TS). The specimens were randomly assigned, with 15 specimens in each of the 3 groups. Cyclic loading (500 cycles) and load-to-failure testing were performed. Gap formation after 100 and 500 cycles, ultimate load to failure, and stiffness were measured. RESULTS: Six constructs failed during cyclic loading, 5 in the PL group (33%) and 1 in the TS group (6.7%). After 100 cycles, differences in gap formation were found between the PL and BT groups (4.48 vs 3.62 mm, P < .03) and between the PL and TS groups (4.48 vs 2.28 mm, P < .0001). After 500 cycles, differences in gap formation were found between the BT and TS groups (6.63 vs 4.16 mm, P < .002) and between the PL and TS groups (7.89 vs 4.16 mm, P < .005). The PL group was found to have a lower ultimate load to failure when compared with the BT group (161.4 vs 258.3 N, P = .019) and the TS group (161.4 vs 237.1 N, P = .009). Group differences in stiffness did not reach statistical significance among the 3 groups (PL, 33.72 N/mm; BT, 37.50 N/mm; TS, 43.00 N/mm). CONCLUSION: The TS and BT groups have more ideal biomechanical properties than the PL group, as demonstrated by less displacement during cyclic loading and a higher load to failure. CLINICAL RELEVANCE: Fixation of the patellar limbs during MPFL reconstruction may be optimized with the use of TS or BT over a PL technique.