The Effect of Targeting the Plantaris Muscle-tendon in Surgical Correction of Ankle Equinus in Children

Plain-language summary

Tight ankle muscles can produce ankle equinus (limited ability to pull the foot upward) and occur often in children, significantly impacting their ability to walk. If not treated, children with ankle equinus frequently experience reduced function and long-term foot problems, such as pain. Currently, treatment options include surgery or Botulinum toxin (BoNTA) injection into the large calf muscles that point the foot downwards, aiming to reduce their tightness. However, these treatments can be less effective over time, can create prolonged calf weakness, and may require long-term bracing. Another small muscle in the leg, the plantaris, is believed to have some contribution to equinus in many children. It is sometimes included in treatment plans for equinus but its contribution is poorly understood. It is unclear whether targeting the plantaris alone could lead to better treatment of ankle equinus. Understanding the effect of treatments targeting the plantaris could help clinicians improve the management of ankle equinus. In this study, the investigators will look at the impact of surgical treatment to the plantaris in ankle equinus. The investigators hypothesize that the plantaris is a significant contributor to equinus. In this study, data will be collected from children undergoing surgical correction of ankle equinus, including lengthening of the plantaris and lengthening of the larger muscles producing equinus (the gastrocsoleus mechanism). Children will be randomly assigned to have either their plantaris or the gastrocsoleus lengthening be done first during surgery. All children will have both structures lengthened during surgery, only the order will be varied and all surgical procedures for each patient will be completed in a single setting. In both groups, maximum passive ankle dorsiflexion (upwards bend of the ankle with the knee straight) will be measured before and after each structure is lengthened. The outcome is maximum passive ankle dorsiflexion (upwards bend of the ankle) with the knee straight. The investigators expect that maximum passive ankle dorsiflexion will increase after lengthening of the plantaris. Understanding the contribution of the plantaris muscle in ankle equinus could lead to significant improvements in the treatment of children with tight ankles.

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