Anterior and distal tunnel orientation for anatomic reconstruction of the medial patellofemoral ligament is safer in patients with open growth plates

Date

2020

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Article

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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 defned by Stephen. A 20-mm-depth drilling was simulated, starting from the insertion point at every possible angle within a 90° 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’s t test and one-way ANOVA. Results Maximum physeal damage (5.35% [4.47–6.24]) was obtained with the 7-mm drill when drilling 3° cephalic and 15° posterior from insertion without diferences between sexes (n.s.). Minimal physeal damage (0.22% [0.07–0.37]) was obtained using the 5-mm drill aimed 45° distal and 0° anteroposterior, not afected by sex (n.s.). Considering intra-articular drilling avoidance, the safest zone was obtained when aiming 30°–40° distal and 5°–35° anterior, regardless of sex. Conclusion Ideal femoral tunnel orientation, avoiding physeal damage and breaching of the intercondylar notch, was obtained when aiming 30°–40° distal and 5°–35° anterior, regardless of sex. This area is a safe zone that allows anatomic MPFL reconstruction of patients with an open physis.

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Citation

Knee Surgery Sports Traumatology Arthroscopy, 2020 Epub

Keywords

Pediatric patellar instability, MPFL reconstruction, Growth plate, Knee anatomy, Femoral tunnel positioning

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