Minimum 2 Year Prospective Follow-Up on a Laterally Placed Trabecular Metal Total Ankle Arthroplasty

Abstract

Category: Ankle, Ankle Arthritis Introduction/Purpose: The laterally placed trabecular metal ankle replacement is placed using a jig and a fibular osteotomy. The tibia and talus are reamed to match the curved contour of the replacement. The lateral approach was advocated to reduce the wound complications of the anterior approach. Additional fixation is achieved using two rails on the tibial and talar component. This study outlines the outcomes of 121 ankles followed prospectively with minimum 2 years follow up. Methods: 121 total ankles were consented to enrollment in a prospective study on outcomes. 10 centers were involved in the prospective study. Enrollment was from 2014 to 2016. 3 patients underwent revision and 5 withdrew (1 death, 2 lost to follow up and 2 requested discontinuation). Demographics were obtained at baseline. The average age was 59.9 at the time of surgery. 48% were male and BMI averaged 29.2. 12.4% had inflammatory arthropathy. EQ5D, AOFAS, AOS scores were obtained preoperatively and at 6 weeks, 6 months, and yearly there after. Revision of metal components for infection or loosening were secondary end points. Statistical significance was tested by the Wilcoxon Signed Rank Test 26 and set at p= 0.05. 95% confidence intervals are given. Of 113 cases, 113 were followed at 6 weeks, 113 at 1 year, and 100 at 2 years and 67 at 3 years. Results: AOS Outcomes improved from 59.7 (SD 20.6) to 22 (SD 18) at 6 months, 18.6 (SD 19.6) at 1 year, 19.8 (SD 21) at 2 years and 21.3 (SD 25) at 3 years. AOFAS scores and EQ5 D scores showed similar improvements at all time points. The improvements were significant compared to baseline at all time points (see figure). Survivorship was .98 at 1 year (CI .92 to .99), and .96 at 2 and 3 years (CI .90 to .99). 3 components were revised, a tibial component (loosening), a talar component (instability), and a polyethylene liner (infection). Conclusion: The laterally placed trabecular metal total ankle arthroplasty has demonstrated reliable improvements in outcome and an excellent survivorship at minimum 2 years follow up. Longer term follow up and larger series will be required to clearly outline its outcome. This early outcome demonstrates very promising outcomes at 3 years and low revision rates.