Isolated Medial Patellofemoral Ligament Reconstruction Under Increased Femoral Anteversion Is Associated With Increased Contact Pressure of Medial Patellofemoral Facet at Deep Flexion Angle: A Cadaveric Study

Abstract

Purpose

To analyze (1) whether isolated medial patellofemoral ligament (MPFL) reconstruction in increased femoral anteversion could replicate the patellofemoral (PF) pressure pattern of a hypothetical normal population and (2) the change of PF pressure according to MPFL state under the same anteversion setting.

Methods

Ten fresh-frozen cadaveric knees were used. Experiments were performed from knee flexion 0° to 90° with 3 MPFL state (intact, released, and reconstructed) and 3 anteversion (initial state, 10° and 20° more increased). Medial and lateral PF joint contact pressures were measured at each point.

Results

At 0° flexion, lateral PF pressure was increased to 62.1 ± 7.8 psi in 10° and 67.3 ± 13.5 psi in 20° more increased anteversion, compared with 43.2 ± 8.6 psi of hypothetical normal population (P .027 and .004, respectively). At 30° flexion, medial PF pressure was decreased to 31.3 ± 11.9 psi in 10° and 27.3 ± 17.5 psi in 20° more increased anteversion, compared with 44.1 ± 10.3 psi of hypothetical normal population (P .009 and .027, respectively). Within the same femoral anteversion, when anteversion was increased 10° and 20° more than the initial state, medial facet pressure after MPFL reconstruction at 90° flexion was increased from 28.7 ± 11.4 psi to 40.0 ± 9.9 psi and 16.7 ± 10.8 psi to 33.9 ± 15.0 psi compared with the intact MPFL (P .047 and <.001, respectively).

Conclusions

Biomechanically, isolated MPFL reconstruction under increased femoral anteversion was unable to replicate the state of a hypothetical normal population. Even when comparing within the same femoral anteversion, isolated MPFL reconstruction at increased femoral anteversion caused medial PF overpressure at 90° flexion angle.

Clinical Relevance

When performing MPFL reconstruction for recurrent patellar dislocation, femoral anteversion should be assessed. Increased femoral anteversion can cause overpressure on the medial facet after isolated MPFL reconstruction.