Can we make out the coronal plane corrections of the knee region by studying the screw divergence in tension band plate induced growth modulations?

We studied the correlation between changes in the interscrew angle (screw divergence) and the correction achieved with tension band plates applied for valgus deformities of the knee region. Twenty-eight children with 68 operated physes were included in this retrospective review. The interscrew angle and screw trajectory angle were measured in the initial and follow-up radiographs. 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 changes in the above-mentioned parameters and the magnitude of correction. The location of the implant was in the distal femur in 49 and the proximal tibia in 19 limbs. A mean correction of 12.1° was achieved at a follow-up of 12.1 months. The correction was calculated as 1.1°/month (SD = 0.6). The correlation of screw divergence ( R = -0.01; P = 0.97) and changes in screw trajectory angle ( R = -0.11; P = 0.36) to the angular correction achieved was statistically insignificant. The changes in the interscrew angle did not correlate with the angular correction following tension band plates.