Prospective Three-Year Outcomes Comparing Cemented and Cementless Fixation in the Trabecular Metal Total Ankle Arthroplasty

Abstract

Category: Ankle; Ankle Arthritis Introduction/Purpose: In total ankle arthroplasty (TAA), the implant can be inserted with or without cement. The United States Food and Drug Administration (FDA) requires cement fixation on most TAAs, whereas cementless TAA can be performed in other countries. The laterally placed trabecular metal ankle replacement is inserted using a jig and a fibular osteotomy. The tibia and talus are reamed to match the curved contour of the replacement. Two rails on the tibial and talar component are used to transfix the cementless component onto bone. FDA licensing requires a bead of cement applied on the fixation rails to assist in early component fixation. The purpose of this study was to compare early and three-year results of TAA with and without rail cement performed in six countries. Methods: One hundred and twenty-one patients were prospectively enrolled (from 2014 to 2016) across 11 centers in six countries. Patients were assigned cement or no cement based on the surgeon's practice. EQ5D, AOS, and AOFAS scores were obtained preoperatively, six weeks and six months postoperatively, and yearly thereafter. Secondary endpoints were revision of metal components for infection or loosening. Statistical significance was tested by the Wilcoxon Signed Rank Test and set at p=0.05.Sixty ankles had cement; 61 ankles were press fit. Cement augmentation patients were heavier and older. Cement cases had longer surgical times (173 minutes, 95% CI 162.8 to 183.2, versus 150 minutes, 95% CI 139.9 to 158.4). The sites using cement fixation varied. Of 121 cases, 117 were followed at one year, 96 at two years, and 84 at three years. Three patients underwent revision and five withdrew (one died, two lost to follow-up, and two requested discontinuation). Results: The EQ5D scores demonstrated better outcomes for the press fit component without cement at six weeks (p<0.001), six months (p=0.001), one year (p=0.005), and two years (p=0.02), but not at three years (p=0.132). The AOS Disability scale demonstrated better outcomes for the press fit component at six weeks (p=0.008), six months (p=0.022), one year (p=0.020) and two years (p=0.024). The AOS Pain scale demonstrated better outcomes for the press fit component at six months (p=0.05). The AOFAS score demonstrated better outcomes for the press fit component at six weeks (p<0.001), but no significant differences thereafter. Survivorship for joint replacement (revision of metal components) was 97.4% for the full cohort. Three metal components were revised in three ankles in the cementless group (chi square not significant). Conclusion: Patient-reported outcome measures favored cementless, press fit fixation through two years postoperatively, with outcomes equalizing between the groups at three years postoperatively. Given the better early outcomes with the press fit design, there does not seem to be a need to augment fixation with cement in this total ankle implant design. There were two metal component revisions and one revision associated with loosening in the cementless group. The significant demographic differences between the groups indicate that a randomized clinical trial is needed to comprehensively define differences in early outcomes and to evaluate long-term results.