Outcomes and Gait Mechanics after Ankle Arthrodesis Take Down with Total Ankle Arthroplasty or Subtalar Fusion in Patients with Previous Tibiotalar Arthrodesis: A Comparative Study

CATEGORY: Ankle, Ankle Arthritis, Basic Sciences/Biologics, Hindfoot INTRODUCTION/PURPOSE: Ankle arthrodesis has traditionally been the treatment of choice for ankle arthritis. However, loss of range of motion, chronic pain, risk of nonunion, and potential risk of adjacent arthritis are ongoing concerns after this procedure. Most of surgeons state that subtalar fusion is an alternative to treat a painful and dysfunctional ankle fusion, but successful ankle arthrodesis take down using Total Ankle Arthroplasty (TAA) has been reported in the literature. The paucity of literature comparing these two treatment methods hinders the ability to make an informed decision on the best therapy. The purpose of the study was to compare patient-reported outcomes; gait mechanics and complications in patients with ankle arthrodesis take down using TAA to those who underwent subtalar fusion in a previously fused ankle. METHODS: This is a comparative study of patients who underwent tibiotalar arthrodesis take down with total ankle arthroplasty and subtalar arthrodesis in previously arthrodesed ankles. Patients who were willing to take the gait mechanics test were included. They were distributed in two groups according to the undergone procedure. Postoperative outcomes consisted of patient- reported functional measures, and complications rate. Patient-reported functional measures included the American Orthopaedic Foot & Ankle Society Score (AOFAS) hindfoot scale, Visual Analogue Scale (VAS) for pain, and the Short Form 36 Health Survey (SF-36). Three-dimensional joint mechanics and ground reaction forces were measured during level walking at least one-year post surgery. Gait mechanics included spatiotemporal parameters, and the peak plantar and dorsiflexion moment. Data were analyzed using analysis of variance (ANOVA) to determine significant differences between the two groups. (a = 0.05). RESULTS: Ten patients were included in the ankle arthrodesis taken down (AATD) group, and seven patients were included in the subtalar fusion (STF) group. The average follow-up time in the AATD and SFT group was 70.4 and 46 months, respectively P=0.14. There were no statistically significant differences in the demographics of both groups. The peak plantar flexion was 4.6 degrees and 1.3 degrees in the AATD and STF group, respectively; P=0.04. The range of motion in the sagittal plane was 11.5 degrees and 7.8 degrees in patients with AATD and STF groups, respectively; P=0.13. The complication rate was higher in the AATD group (7 patients, 70% vs 1 patient, 14%; P=0.02). There were no statistically significant differences in the patient-reported outcomes between the two groups. CONCLUSION: Patients with ankle arthrodesis taken down using total ankle arthroplasty as compared with patients with tibiotalocalcaneal arthrodesis have better range of motion of the hindfoot and improved gait mechanics. The improved cadence and mobility decreased the imbalance in the midfoot and forefoot during the gait. Nevertheless, due to the complexity of the procedure the complication rate is considerably higher. Further research with a larger sample of both groups may demonstrate greater differences in patient-reported outcomes.