Hemiepiphysiodesis using tension band plates: does the insertion technique or screw length influence the rate of correction?

Abstract

We retrospectively studied the effect of certain characteristics of the insertion technique and the construct of tension band plates on its angular correction rates. The study included 68 physes in 28 children. The following preoperative radiological parameters were measured: interscrew angle; the length of the epiphyseal screw, its distance and angle (screw trajectory angle) with respect to the physis. Additionally, changes in the mechanical lateral distal femoral angle and medial proximal tibial angle were calculated from the follow-up radiographs. The statistical calculations involved correlating the above-mentioned parameters and correction rates using a correlation coefficient. The mean patient age at the time of surgery was 8.6 years and the follow-up was 12.1 months. The mean screw trajectory angle was 13.4 degrees, the interscrew angle 18.9 degrees and the proportion of screw length was 41.3%. The mean correction rate recorded was 1.1 degrees/ month. The child's age (R = -0.13), screw trajectory angle (R = -0.13), interscrew angle (R = -0.02), distance of screw from physis (R = 0.04), and length of screw (R = 0.07) did not show statistically significant correlation with the angular correction rates. The correction rate produced by the tension band plate was found nearly independent of the parameters recorded for insertion technique (screw trajectory angle, interscrew angle, distance of screw from the physis) or construct (length of the epiphyseal screw). It functions as long as the physis is tethered by a side plate adequately secured by appropriate length screws.