The medial patellofemoral ligament (MPFL) is essential for the maintenance of correct biomechanical function of the knee. Reconstruction of the MPFL is commonly used in the restoration of patellofemoral stability after traumatic lateral subluxation of the patella. Although a method to accurately determine the MPFL's insertion point has been described, it remains unclear if anatomic placement of MPFL graft tissue is essential for preservation of knee function after MPFL reconstruction. Thus, the purpose of this study was to determine the importance of anatomic placement of MPFL graft tissue for the preservation of knee function following MPFL reconstruction operations.
Twenty-seven subjects who underwent MPFL reconstruction operations were retrospectively analyzed. Postoperative radiographs were reviewed. Measurements were taken, and the placement of each patient's MPFL graft tissue was determined to be anatomic or non-anatomic based on radiographic methods previously described in the literature. Each subject's electronic medical record was then reviewed, and clinical data was recorded. Finally, the clinical outcomes of each patient were compared to placement location of the MPFL graft tissue in their procedure.
Thirteen patients were found to have anatomic MPFL graft tissue placement, and 14 non-anatomic. A significant post-operative difference was found between groups in the following parameters: WOMAC pain (anatomic mean = 85.71 ± 11.34, non-anatomic mean = 75.00 ± 26.35 p = 0.018), function (anatomic mean = 85.85 ± 9.96, non-anatomic mean = 79.09 ± 24.45, p = 0.017) and in KOOS symptom (anatomic mean = 75.63 ± 11.79, non-anatomic mean = 67.83 ± 22.40, p = 0.024), pain (anatomic mean = 77.54 ± 8.61, non-anatomic mean = 71.39 ± 25.18, p = 0.01), ADL (anatomic mean = 85.85 ± 9.97, non-anatomic mean = 79.09 ± 24.45, p = 0.017) and overall (anatomic mean = 74.61 ± 10.33, non-anatomic mean = 69.41 ± 24.25, p = 0.01) scores. No significant difference was observed for post-op instability (p = 0.290) or apprehension (p = 0.496), improvement in WOMAC or KOOS, 2-week, 6-week, or final 1-year range of motion, WOMAC stiffness, or KOOS sport/recreation or QOL.
Within the range of graft placement values considered by this study, while no reduction in range of motion was seen, non-anatomic placement of MPFL graft tissue in MPFL reconstruction operations caused increased pain and decreased function, evidenced by post-operative KOOS and WOMAC scores.
It seems that the pivotal step in MPFL reconstruction operations is ensuring correct patellofemoral tracking via intraoperative electrical femoral nerve stimulation. If this step of the procedure is performed correctly, non-anatomic placement will not limit range of motion, lead to continued apprehension, or affect the overall biomechanical functioning of the knee.