Range of motion of foot joints following total ankle replacement and subtalar fusion

Background: In severe cases of ankle and subtalar arthritis, arthrodesis of the subtalar joint is performed in combination with ankle arthroplasty. In these special cases gait analysis reveals real motion at the replaced tibiotalar joint. Methods: Twenty-three patients affected by ankle and subtalar arthritis, treated either with a 3-component or a 2-component prosthesis in combination with subtalar arthrodesis, were clinically evaluated preoperatively and at a minimum of 1-year follow-up. Gait analysis was performed postoperatively using a multi-segment foot protocol. Foot kinematics were compared to corresponding data from a healthy control group. Results: Clinical scores significantly improved from preoperative to follow-up. The clinically measured passive ankle dorsiflexion/plantarflexion significantly improved at the follow-up. Patients’ normalized walking speed and stride length were significantly lower than those in control. With exception of the ankle frontal-plane motion, sagittal-plane mobility of foot joints was about 50% than that in healthy joints. Conclusions: Improvement in clinical scores was found for both prostheses. Normal spatio-temporal parameters were not restored. In these patients, fusion of the subtalar joint appeared to be compensated by larger frontal-plane motion at the tibiotalar joint. Level of evidence: Level III- retrospective comparative study. The study was approved by the local Ethics Committee as protocol MAT (protocol registration at clinicaltrials.gov NCT03356951).