Foot abduction increases after achilles tenotomy in clubfoot patients.

Background: Although Achilles tenotomy is performed to increase the ankle dorsiflexion in clubfoot patients, it may also increase the amount of the foot abduction due to the unique oval field of motion property of the ankle and subtalar joint complex. This study investigated the effect of Achilles tenotomy on foot abduction in patients with clubfoot.

Methods: Equinus deformity before tenotomy (EBT), equinus deformity after tenotomy (EAT), abduction before tenotomy (ABT), and abduction after tenotomy (AAT) were measured. The decrease in the amount of equinus after tenotomy (Δ equinus) and the increase in the amount of abduction (Δ abduction) after tenotomy were then calculated.

Results: The Achilles tenotomy was performed on 22 feet of 16 patients. The results (Mean ± standard deviation) were as follows: EBT: 28° ± 19 (range, 8-76), EAT: -27° ± 7 (-36- -11), ABT: 54° ± 16 (21-72), AAT: 77° ± 5 (66-85), Δ equinus: 55° ± 15 (38-87), Δ abduction: 23° ± 15 (5-51). The change between EBT-EAT and ABT-AAT was statistically significant (both p < 0.001). EBT was correlated negatively with ABT (r = -0.648; p = 0.001) and Δ equinus was correlated positively with Δ abduction (r = 0.522; p = 0.013).

Conclusion: The Achilles tenotomy in clubfoot patients not only increases ankle dorsiflexion but also increases the foot abduction due to oval field of motion of the ankle and subtalar joint complex. It should be considered that an increase of the foot abduction may be achieved after the Achilles tenotomy. Therefore, the maximum foot abduction may be achieved after the Achilles tenotomy, not before the Achilles tenotomy.