Percutaneous Epiphysiodesis Using Transphyseal Screws in the Management of Leg Length Discrepancy: Optimal Operation Timing and Techniques to Avoid Complications

Background: Percutaneous epiphysiodesis using transphyseal screws (PETS) has been used to manage leg length discrepancy (LLD) in growing children. The purposes of this study were to analyze effects of PETS on LLD, its associated complications, to determine optimal operation timing, and find ways of preventing complications. Patients and Methods: The data of 59 patients obtained up to screw removal or at skeletal maturity were retrospectively analyzed. Retrospective growth calculations were done using multiplier method. The efficacy of LLD correction was calculated, and the predicted segment length with the index operation was compared with the final measured length and final LLD was measured. The screw insertion angle in 3-dimension was calculated, and it was correlated with the efficacy. Complications associated with screw design and the techniques used were analyzed. Results: The LLD correction efficacy averaged 75.5% (5.0 to 114.0) at the distal femur and 78.9% (11.0 to 111.0) at the proximal tibia. However, mean final LLD was 3.0mm (range, -10.0 to 16.7 mm), presumably because operations were performed on average 1.3 years earlier than estimated by growth calculation. Three-dimensional screw insertion angle was positively correlated with LLD correction efficacy. Complications were closely related to the screw design and the implantation techniques. Conclusions: PETS provides a minimally invasive and effective means of LLD correction. In view of its delayed effect, we recommend that PETS be performed at least 1 year earlier than estimated optimal epiphysiodesis timing. The careful selection of screw design and length and accurate screw placement are the keys to successful results. Level of Evidence: Level IV prognostic studies.