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Femoral Tunnel Position Thresholds Associated With Functional Outcomes After Medial Patellofemoral Ligament
Byeong-Hun Jeon1,2, Min Jung1,2, Kwangho Chung1,3
1Arthroscopy and Joint Research Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
Background:
While numerous studies have examined the effects of femoral tunnel malposition in medial patellofemoral ligament (MPFL) reconstruction (MPFLR), the extent to which deviation from the anatomic femoral insertion can be tolerated before patient-reported outcome measures (PROMs) are adversely affected has not been clearly established.
Purpose:
To evaluate postoperative improvements in PROMs after MPFLR, determine outcome-based cutoffs for femoral tunnel placement using 3-dimensional imaging, and assess the effects of directional deviations.
Study Design:
Cohort study, Level of evidence 3.
Methods:
This retrospective study included 50 knees that underwent MPFLR between 2011 and 2023, with or without concomitant tibial tubercle osteotomy. PROMs (Lysholm, Tegner, International Knee Documentation Committee [IKDC], Knee injury and Osteoarthritis Outcome Score [KOOS], and Kujala) were collected pre- and postoperatively, and minimal clinically important differences (MCIDs) were calculated using a distribution-based method. Femoral tunnel positions were analyzed in 37 knees using postoperative computed tomography. Pearson correlation and receiver operating characteristic (ROC) curve analyses identified tunnel deviation thresholds associated with clinically meaningful improvements, and directional analyses assessed anterior-posterior and proximal-distal variations.
Results:
All PROMs significantly improved after surgery, with MCID achievement rates of up to 68%. Femoral tunnel deviation was negatively correlated with the IKDC, KOOS, and Kujala scores. ROC analysis identified a 7.2-mm cutoff for predicting meaningful IKDC improvement (area under the curve = 0.892). Directional analysis showed no significant differences between anterior and posterior placements; however, a distal deviation >4.5 mm was associated with significantly poorer IKDC, KOOS pain, and KOOS sports outcomes.
Conclusion:
This study establishes a PROM-based cutoff for femoral tunnel positioning in MPFLR. A deviation of >7.2 mm from the anatomic insertion significantly compromises functional improvement, and excessive distal displacement has a particularly detrimental effect on outcomes.
