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, < .03) and between the PL and TS groups (4.48 vs 2.28 mm, < .0001). After 500 cycles, differences in gap formation were found between the BT and TS groups (6.63 vs 4.16 mm, < .002) and between the PL and TS groups (7.89 vs 4.16 mm, < .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, = .019) and the TS group (161.4 vs 237.1 N, = .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.