Is there a negative correlation between screw length and correction rate via guided growth? A retrospective study of 138 limbs with genu varum.

PURPOSE: To identify factors that contribute to the speed of angular correction in skeletally immature patients with genu varum treated with paraphyseal tension band plates, hypothesizing that screw length and divergence, severity of deformity, and underlying pathology influence the rate and speed of genu varum correction.

METHODS

Fifty-three patients (38 males, 15 females) undergoing genu varum correction were included; a total of 138 physes (64 distal femur, 74 proximal tibia) were assessed. The median age at surgery was 37.83 ± 34.27 months (24.37-188.60), and the median follow-up was 11.03 ± 4.9 months (3.17-23). The severity of the deformity, the relative screw length, correction speed (degree per month), and initial screw divergence were calculated for comparison.

RESULTS

Patients close to skeletal maturity showed faster correction speed. Patients with genu varum secondary to metabolic disease had the slowest correction speed (0.76° per month), while there was no clinically significant difference with different etiologies. The distal femur showed a lower correction speed than that of proximal tibia in genu varum. The correction rate was negatively correlated with the relative screw length in genu varum deformity (linear regression coefficient: - 2.39; P < 0.01). The initial screw divergence had no statistically significant impact on the correction speed (P = 0.97).

CONCLUSION

Screw length is an important parameter affecting the rate of genu varum correction with GG using paraphyseal tension band plates.