Rate of Correction and Recurrence of Ankle Valgus in Children Using a Transphyseal Medial Malleolar Screw.

BACKGROUND: Transphyseal medial malleolar screw (TMMS) hemiepiphysiodesis is an effective treatment for ankle valgus in children. There is limited evidence on the effect of age and diagnosis on the rate of correction as well as the deformity recurrence after screw removal. The purpose of this study was to determine (1) the rate of correction of ankle valgus after hemiepiphysiodesis using a TMMS, (2) the effects of clinical diagnosis and age at surgery on the rate of correction, and (3) the rate of valgus recurrence after TMMS removal.

METHODS: In this retrospective study we included 16 male and 21 female patients (63 ankles) with an average age at surgery of 11.0 years (range, 5.4 to 14.8 y) who underwent TMMS hemiepiphysiodesis for the treatment of ankle valgus. There was a mean radiographic follow-up of 1.6 years (range, 0.4 to 4.9 y) before screw removal. For subjects who received screw removal (43 ankles), the average time from insertion to removal of the screw was 1.4 years (range, 0.4 to 5.2 y). Valgus deformity was assessed on anteroposterior ankle radiographs by measurement of tibiotalar angle. Linear mixed effects models were used to determine rates of correction and valgus recurrence.

RESULTS: The average rate of correction in tibiotalar angle was 0.37±0.04 degrees per month (P<0.001). Clinical diagnosis and age at surgery significantly affected the amount of postoperative correction in tibiotalar angle (P<0.05). Eighteen of 22 ankles (81.8%) demonstrated recurrence of ankle valgus after screw removal. The average recurrence rate in patients who underwent screw removal was 0.28±0.08 degrees per month (22 ankles, P=0.002).

CONCLUSIONS: This study supports the effectiveness of the TMMS hemiepiphysiodesis for treating pediatric ankle valgus, but the effects of additional skeletal growth should be considered as the ankle may rebound into valgus after correction and screw removal. The results from this study can help with surgical planning to predict the amount of correction that may be achieved depending on underlying diagnosis and age at surgery.

LEVEL OF EVIDENCE: Level IV-retrospective study.