The Role of the Plantaris in Intramuscular Gastrocnemius Equinus Correction.

Equinus deformity is a common cause of foot and ankle pathology. The purpose of our study was to evaluate the role of the plantaris in equinus. Secondary aims were to describe the role of the plantaris in intramuscular gastrocnemius recession and to determine the prevalence of the plantaris in our patient population. We measured ankle dorsiflexion during the steps of a Baumann-type intramuscular gastrocnemius recession. Eighty-nine patients were enrolled in our study. Fourteen of 89 (15.7%) patients did not have a plantaris. A mean dorsiflexion of 9 (interquartile range 6-12)° was obtained after transection of the plantaris tendon and an additional mean 8 (interquartile range 5-10)° was obtained after recession of the gastrocnemius aponeurosis. There was a strong positive correlation (rs = 0.842) of dorsiflexion increase after plantaris transection and dorsiflexion increase after gastrocnemius recession (p < .00). Linear regression showed that for every one-degree of dorsiflexion increase with plantaris transection, there was a predicted dorsiflexion increase of 0.69° with gastrocnemius recession. These results indicate that the plantaris is a component of equinus deformity.