Abstract

Purpose In patients with open growth plates, the direction of tunneling that avoids distal femoral physis (DFP) damage in anatomic reconstructions of the medial patellofemoral ligament (MPFL) has been a topic of discussion. The objective of this study was to determine the ideal orientation for anatomic reconstructions of MPFL tunneling that minimized DFP damage while avoiding breaching the intercondylar notch. Methods Eighty magnetic resonance images of patients aged 10 through 17 were obtained, randomly sampled from the institutional database. A de novo software was developed to obtain 3D models of the distal femur and DFP. In each model, the anatomical insertion point of the MPFL was determined as defined by Stephen. A 20-mm-depth drilling was simulated, starting from the insertion point at every possible angle within a 90 degrees cone using 5-, 6- and 7-mm drills. Physeal damage for each pair of angles and each drill size was determined. Damage was expressed as a percentage of total physis volume. Statistical analysis was conducted using Student'sttest and one-way ANOVA. Results Maximum physeal damage (5.35% [4.47-6.24]) was obtained with the 7-mm drill when drilling 3 degrees cephalic and 15 degrees posterior from insertion without differences between sexes (n.s.). Minimal physeal damage (0.22% [0.07-0.37]) was obtained using the 5-mm drill aimed 45 degrees distal and 0 degrees anteroposterior, not affected by sex (n.s.). Considering intra-articular drilling avoidance, the safest zone was obtained when aiming 30 degrees-40 degrees distal and 5 degrees-35 degrees anterior, regardless of sex. Conclusion Ideal femoral tunnel orientation, avoiding physeal damage and breaching of the intercondylar notch, was obtained when aiming 30 degrees-40 degrees distal and 5 degrees-35 degrees anterior, regardless of sex. This area is a safe zone that allows anatomic MPFL reconstruction of patients with an open physis.