CT Measurement of Range of Motion of Ankle and Subtalar Joints Following Two Lateral Column Lengthening Procedures

Background: Lateral column lengthening (LCL) has become an accepted procedure for the operative treatment of the flexible flatfoot deformity. Hindfoot arthrodesis via a calcaneocuboid distraction arthrodesis (CCDA) has been considered a less favourable surgical option than the anterior open wedge calcaneal distraction osteotomy (ACDO), as CCDA has been associated with reduced hindfoot joint motion postoperatively. The ankle and subtalar joint ranges of motion were measured in patients who underwent an ACDO or CCDA procedure for flatfoot deformity. Methods: CT scanning was performed with the foot in extreme positions in five ACDO and five CCDA patients. A bone segmentation and registration technique for the tibia, talus and calcaneus was applied to the CT images. Finite helical axis (FHA) rotations representing the range of motion of the joints were calculated for the motion between opposite extreme foot positions of the tibia and the calcaneus relative to the talus. Results: The maximum mean FHA rotation of the ankle joint (for extreme dorsiflexion to extreme plantarflexion) after ACDO was 52.2 degrees +/- 12.4 degrees and after CCDA 49.0 degrees +/- 12.0 degrees. Subtalar joint maximum mean FHA rotation (for extreme eversion to extreme inversion) following ACDO was 22.8 degrees +/- 8.6 degrees, and following CCDA 24.4 degrees +/- 7.6 degrees. Conclusion: An accurate CT-based technique was used to assess the range of motion of the ankle and subtalar joints following two lateral column lengthening procedures for flatfoot deformity. Comparable results with a considerable amount of variance were found for the range of motion following the ACDO and CCDA procedures