Dimeglio's derotation of calcaneo pedal block and Pirani's talar head reduction: a quantitative matching.

We aimed to determine the quantitative value of derotation of calcaneo pedal block (DCPB) of Dimeglio system equivalent to talar head reduction of Pirani system. We also compared the ankle dorsiflexion obtained post tenotomy for different measures of DCPB. The study involved 53 idiopathic clubfoot children (86 feet) treated with Ponseti technique. Percutaneous Achilles tenotomy to correct ankle equinus was performed when forefoot adduction, heel varus were corrected and ankle dorsiflexion was <10°. Pirani's coverage of lateral head of talus was taken as a determinant of adequate DCPB and to perform tenotomy. Mean patient age at enrollment was 60.9 ± 71.1 days. The median pre and posttreatment Dimeglio scores were 13 (range 4-20) and 0 (range 0-3), respectively. DCPB at the time of talar head reduction was 53.8 ± 9.8°. In 85% feet, talar head reduction was obtained by DCPB 60° and all were reduced by 70°. The average ankle dorsiflexion improved significantly with DCPB ≥ 50°. The measure at which DCPB matched with talar head reduction of Pirani system was variable (40-70°). In all feet, talar head was reduced by 70° DCPB. Post tenotomy, ankle dorsiflexion was better with DCPB ≥ 50°.