Abstract
BACKGROUND: Medial patellofemoral ligament (MPFL) reconstruction has become very popular for treating patellar instability. However, it is unclear how patellofemoral (PF) contact pressure changes after MPFL reconstruction and how to restore the native PF contact pressure. PURPOSE: To identify the effect of intra-operative factors (graft types, tunnel locations, pre-tension levels, and graft fixation angles) of MPFL reconstruction on PF contact pressure in a review of human cadaveric studies. METHODS: Studies in PubMed and Web of Science databases were searched from database inception to June 2023. The inclusion criterion was cadaveric biomechanical studies of MPFL reconstruction that provided data on the PF contact pressure. The Quality Appraisal for Cadaveric Studies (QUACS) scale was used to perform comprehensive assessment of the methodological quality of the included studies. RESULTS: A total of 14 biomechanical studies comprising 135 knees were identified and reported for the overall or medial and lateral PF contact pressures after MPFL reconstruction. Five studies selected at least two different grafts for reconstruction and reported that all graft types could restore the native PF contact pressure. In terms of femoral tunnel location: Schöttle point (7 studies), adductor tubercle (1 study), proximal or distal to the anatomic origin (2 studies), the femoral tunnel location should be closer to the native insertion; otherwise, the postoperative PF contact pressure could increase significantly. The graft pre-tension was most commonly 2 N or 10 N, while fixation of the graft was commonly at 30° or 60° of knee flexion. Overtensioning of the graft increased the medial PF contact pressure and patellar tilt; a fixation angle deviating significantly from the commonly used 30° or 60° (e.g.0° or 90°) may lead to an increase in PF contact pressure, particularly on the medial facet, however, the effect is not uniform across all studies and may be influenced by graft type and tension. CONCLUSION: In cadaveric biomechanical testing, MPFL reconstruction can effectively restore the native PF contact pressure irrespective of the graft type, but changes in the femoral tunnel location can severely affect the postoperative PF contact pressure. Fixation of the graft at 30° or 60° of knee flexion with 2 N or 10 N of pre-tension would be more conducive to restoration of the original PF pressure.