Unsuspected tarsal coalitions in equinus and varus foot deformities

Tarsal coalitions have been reported in the setting of equinovarus foot deformities, but only as rare isolated findings. Failure to recognize this diagnosis may inhibit successful equinovarus correction. Here, we review a series of tarsal coalitions seen in congenital and neuropathic equinovarus deformity at two institutions, to report the breakdown of types of coalitions encountered, and to suggest methodology to facilitate earlier diagnosis. The records of all patients treated by two of the authors for bilateral equinovarus deformities and found to have either a unilateral or bilateral tarsal coalition between 2006 and 2016 were reviewed. Nine feet with tarsal coalition (calcaneonavicular n = 7 and talocalcaneal n = 2) were reviewed. Five of these cases occurred in patients with idiopathic equinovarus and four cases in patients with equinovarus related to a neurologic disease. All patients were definitively diagnosed by computed tomography scans with 3D reconstruction. In 56% of cases, the patient had previously undergone at least one open procedure before the coalition was recognized. The mean age at diagnosis of the coalition was 11.4 years. Our experience suggests that tarsal coalitions, particularly calcaneonavicular coalitions, may occur more frequently in equinovarus deformities than previously reported. Upon recognition and removal of these coalitions, we were able to achieve improved correction of the equinovarus deformities and improved range of motion. We recommend that surgeons maintain an awareness of this potential concomitant problem in all equinovarus foot deformities and consider advanced imaging in cases which fail to respond to traditional treatment.