2015 ISAKOS Biennial Congress ePoster #1920

Biomechanical Evaluation of MPFL Reconstructions: Differences in Dynamic Contact Pressure Between Gracilis and Fascia Lata Graft

Olaf Lorbach, MD PhD, Bensheim GERMANY
Alexander Haupert, MD, Homburg (Saar) GERMANY
Dieter Kohn, MD, PhD, Homburg (Saar) GERMANY
Konstantinos Anagnostakos, MD, PhD, Homburg (Saar) GERMANY
Saarland University, Homburg (Saar), GERMANY

FDA Status Cleared

Summary: Anatomic reconstruction of the MPFL with either a gracilis or a fascia lata graft was not able to fully restore knee kinematics compared to the intact knee

Abstract:

Purpose

Evaluation of changes in dynamic patellofemoral contact pressure after reconstruction of the MPFL using the gracilis tendon or a fascia lata graft.

Methods

16 human cadaveric knees were used for the testing. Knees were fixed in a custom-made fixation device which allows for a knee flexion from 0 to 90°. A lateral arthrotomy was performed in order to fix a sensitive pressure film (Tekscan) in the patellofemoral joint. After accurate closure of the lateral approach, a constant pull of 50N was applied on the quadriceps tendon in order to simulate the physiological muscle pull in an in-vivo situation. Patellofemoral contact pressure was assessed during a dynamic flexion movement from at 15-30-45-60-75 and 90°. A medial parapatellar incision was made, the medial patellofemoral ligament was cut and measurements were repeated. Reconstruction of the MPFL was performed by an experienced knee surgeon with the gracilis tendon (Group I) or a fascia lata graft (Group II).Tunnel localisation was performed under fluoroscopic control in order verify anatomic tunnel placement. Grafts were fixed at 30° of flexion using two 4.75mm knotless anchors in the patella and a bio-interference screw in the femur. After final fixation of the grafts, pressure measurements were repeated.

Results

Incision of the medial patellofemoral ligament significantly reduced patellofemoral contact pressure at 15°, 30° and 45° compared to the intact knee (p<.05). In the hamstring group, reconstruction of the MPFL closely restored patellofemoral contact pressure compared to the intact knee except of a significant reduced contact pressure at 45° of flexion (p=.038). In the fascia lata group, a significant reduction of patellofemoral contact pressure was observed after MPFL reconstruction at 45,60,75 and 90° (p<.05). Although not significant, different loading patterns in patellofemoral contact pressure were observed between the different grafts.

Conclusions

Incision of the MPFL significantly reduces patellofemoral contact pressure compared to the intact knee. Anatomic reconstruction of the MPFL with either a gracilis or a fascia lata graft was not able to fully restore knee kinematics compared to the intact knee as a remaining reduction in patellofemoral contact pressure was found during knee flexion. Moreover, different loading patterns were observed in dynamic patellofemoral contact pressure measurements between the tested grafts.

CLINICAL RELEVANCE
Anatomic reconstruction of the MPFL may lead to persistently reduced patellofemoral contact pressure during knee flexion. Moreover, the type of graft may alter loading pattern in the patellofemoral joint.