Efficacy of Percutaneous Retrograde Transphyseal Guided Growth Screw in Distal Femoral Angular Deformity Correction: A New Technique.

Background: We modified the original technique for percutaneous transphyseal screw which was described in 1998 by Metaizeau and colleagues for distal femoral coronal angular deformity correction; the modification is related to the screw direction, whereas the screw is administered in a retrograde pattern, starting from the epiphysis and directed toward the metaphysis. This technique opposes the original technique that was started with a metaphyseal entry point which aimed toward the epiphysis. This study evaluates the efficacy of the newly suggested surgical technique regarding the rate of correction and growth resumption after screw removal.

Methods: This prospective study looked at 40 patients (65 distal femoral physes), who underwent a percutaneous retrograde transphyseal guided growth screw procedure, from October 2017 to September 2019. All the patients included had distal femoral coronal angular deformities; 52 in valgus and 13 in varus deformities. The study included 17 females with an average age of 11.75 (range: 8.4 to 14.5 y) for 29 femurs and 23 males with an average age of 13.75 (range: 11.75 to 15.6 y) for 36 femurs. The mechanical lateral distal femoral angle was measured initially, and then again was measured after reaching the desired corrected orientation. The patients were then followed up after the screw removal and followed up to maturity, if the physis had continued to grow postcorrection. The degree of correction per month was calculated, and the consequence of screw removal was detected. Follow-up average time was 12.6 months (range: 30 to 6 mo).

Results: The average correction in the distal femur was 1.3 degrees per month (range: 0.5 to 1.857 degrees/mo). In all of the 65 segments (61 femurs had significant growth remaining and 4 femurs had reached skeletal maturity with suboptimal mechanical lateral distal femoral angle correction), the screws were removed at the time of angular correction. Rebound growth was observed in 15 physes with an average of 1.8 degrees (range: 2 to 3 degrees); they were stable in 42 physes and progressed in 4 physes with an average of 1.6 degrees (range: 1 to 2 degrees). Complications were minor and related to entrapment of soft tissue under the screw washer.

Conclusion: Percutaneous retrograde transphyseal guided growth screw for distal femur coronal angular deformity is a minimally invasive procedure, with a statistically significant correction rate when compared with the original transphyseal screw technique. The new technique has proven to have growth resumption after screw removal with minimal complication risk.

Level Of Evidence: Level III-prospective observational study.