PETS (Percutaneous Epiphysiodesis Using Transphyseal Screws) in the Proximal Tibia: Deep Peroneal Nerve Proximity

Background: Percutaneous epiphysiodesis with transphyseal screws (PETS) is commonly used to treat limb-length discrepancy and angular knee deformity in children. PETS carries a small but serious risk of nerve injury from mechanical and/or thermal damage caused by instrumentation near the deep peroneal nerve (DPN). Our goals were to (1) characterize the location of the DPN to an ideally placed PETS screw in pediatric patients undergoing medial proximal tibia hemiepiphysiodesis; and (2) describe the optimal PETS screw trajectory in this location. Methods: This was a retrospective study of lower-extremity magnetic resonance imaging (MRI) of pediatric patients at our institution between January 2017 and July 2024. MRIs were excluded for incomplete visualization of the proximal tibia or the presence of tumors or fractures. Multiplanar reformations were generated to simulate the ideal medial proximal tibia PETS trajectory, defined as a screw crossing the medial 1/6 of the proximal tibia physis at a 55 degrees angle relative to the physis. Distances between the DPN and the ideal PETS trajectory were measured at the lateral cortical entry site on the proximal tibia, the point nearest the nerve, and the superficial fascia. Results: Of the 56 MRIs identified, 19 were included (mean patient age, 10.8 y, 68% female). Mean ± SD distance from the DPN to the lateral cortical entry site of the tibia was 1.4 ±0.4 cm. The closest mean distance between the screw and DPN was 1.0± 0.5 cm. Mean distance between the DPN and the superficial fascia was 2.4± 0.7 cm. The screw trajectory was always anterior to the DPN. Conclusions: Given the proximity of transphyseal screws to the DPN during percutaneous epiphysiodesis of the medial proximal tibia, correct screw trajectory and a thorough understanding of the neurovascular anatomy in relation to bony landmarks is crucial to prevent nerve injury. In addition, biasing the screw path anteriorly can assist in maintaining a "safe zone"between the instrumentation and the DPN.