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.

Purpose: This study aimed to analyze (1) whether isolated medial patellofemoral ligament (MPFL) reconstruction in increased femoral anteversion could replicate 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 three MPFL state (intact, released, and reconstructed) and three 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 to 43.2 ± 8.6 psi of hypothetical normal population (P-value 0.027 and 0.004, 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 to 44.1 ± 10.3 psi of hypothetical normal population (P-value 0.009 and 0.027, 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 to 40.0 ± 9.9 psi and 16.7 ± 10.8 to 33.9 ± 15.0 psi compared to the intact MPFL (P-value 0.047 and <0.001, 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 following isolated MPFL reconstruction.