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Optimal knee flexion angle during medial patellofemoral ligament reconstruction graft tensioning in a cadaveric model
Robert C Gillis1, Brent G Parks2, Daryl C Osbahr3
1Department of Orthpedic Surgery WellSpan Orthopedics, WellSpan Gettysburg Hospital Gettysburg Pennsylvania USA.
Purpose:
To determine the optimal knee flexion angle for graft tensioning of the MPFL reconstruction to minimize patellofemoral contact pressures.
Methods:
Ten cadaveric knees underwent MPFL reconstruction using a hamstring auto-graft. The graft was fixed to the patella at 40% of length from the proximal tip, secured with suture tied over a bone bridge. On the femoral side, the graft was placed at the anatomic footprint and was draped over a modified pedicle screw with a soft tissue washer. The graft was tensioned at 0°, 15°, 30°, 45° and 60° of knee flexion with 300 N of force. Patellofemoral joint contact pressures were measured at 30°, 45°, 60°, 75° and 90° of knee flexion. Specimens were tested in intact MPFL and reconstructed state. Collinear compressive forces were applied using a custom jig on a load frame. Contact pressure measurements were recorded using the I-scan system. Data were analyzed comparing different angles of tensioning in the intact, cut MPFL, and reconstructed states at different angles of knee flexion Data were analyzed with repeated measures analysis of variance (ANOVA) with p < 0.05 considered significant.
Results:
No statistical differences were found in patellofemoral contact pressures when comparing different angles of tensioning in the intact MPFL, or reconstructed state at different angles of knee flexion.
Conclusion:
At all angles of knee flexion tested, no significant differences were found in the patellofemoral contact pressures. Cadaveric studies have multiple limitations and most important in this study is the older age of the specimens (average age of 83 years in this study) as most patella instability patients are on the younger side. This study suggests that there is no ideal angle of knee flexion at which to tension an MPFL reconstruction and thus no specific knee flexion angle which is superior to another angle when tensioning the MPFL in a cadaveric model.
Study Design:
Controlled laboratory study.
Level Of Evidence:
N/A.
