Subtalar arthrosis: evaluation with CT.

The surgical implantation of a Silastic wedge into the lateral subtalar joint (subtalar arthrosis) is designed to restrict the osseous malalignment associated with a flexible or neurogenic flatfoot deformity. We used CT to examine patients who had persistent pain after a subtalar arthrosis and retrospectively reviewed our experience with CT scans of 13 subtalar implants (seven patients) during a 3.5-year period. The CT scans of four asymptomatic subtalar implants showed each implant in the expected position and orientation, and the findings were considered normal. Conversely, the findings on CT scans of all nine painful implants (seven patients) were interpreted as abnormal. The scans showed oblique orientation of four implants (44%), loosening of three implants (33%), extruded methyl methacrylate in the subtalar joint in two implants (22%), and abnormal calcaneal recession in two implants (22%). Five of the nine painful implants were revised with improvement or resolution of symptoms. Our experience suggests that CT scanning of the subtalar joint can show the position and orientation of a subtalar implant and identify causes of persistent pain after a subtalar arthrosis.