The objectives of this study were to clarify the efficacy of the calcaneal lengthening procedure for flatfoot deformity in spastic conditions, and to identify factors affecting results after calcaneal lengthening.

Ninety-eight feet in sixty patients were included in this study. The average age was 9.5 years and mean follow-up was 2.4 years. The following comparisons were made pre- and post-operatively: clinical, radiographic, kinematic, kinetic changes, and type of bone graft.

Seventy five feet (77%) showed excellent or good clinical results. Decreased longitudinal arch was the most resistant component after calcaneal lengthening. All of the radiological indices improved significantly, and were within the normal range, except calcaneal pitch post-operatively. Pre-operative calcaneal pitch was the most sensitive index for predicting the end result. According to 3-D gait analysis, peak knee flexion during early swing increased from 56.2° to 61.9° on average, and exaggerated dorsiflexion of the ankle in the stance phase improved to the normal range with restoration of first rocker action post-operatively. Foot progression angle, which averaged 16.7° of external progression pre-operatively, improved to 7.4° of external progression post-operatively. Peak and A2 power generation of the ankle increased post-operatively.

Calcaneal lengthening proved an effective procedure for improving foot function, foot progression angle and knee flexion, and for increasing ankle power generation by increasing the foot lever arm.