Minimum 5-Year Outcomes of the Lateral Trabecular Metal Ankle Arthroplasty

Abstract

Category: Ankle; Ankle Arthritis Introduction/Purpose: The treatment of ankle arthritis has changed significantly with the recent advances in total ankle arthroplasty (TAR). Many different designs of TAR have been used around the world as the biomechanical technology advances and our understanding increases. Most implant system are anterior-based and have a flat cut on the tibial prosthesis. Only one implant, the Trabecular Metal (Zimmer-Biomet, Warsaw, IN), utilizes a lateral approach with a fibular osteotomy to gain access to the tibiotalar joint and a sagittally curved tibial component. Recent publications have described a higher reoperation rate with this implant system. This study aimed to report the 5-year clinical and radiographic outcome as well as the survivorship of the implant. Methods: Over a three-year period, two fellowship-trained foot and ankle surgeons used this implant system for patients indicated for TAR. A total of 38 patients were reviewed with an average age of 63.4+-8.6 years-old, BMI of 28.9+-4.6 and the majority (78%) had post-traumatic arthritis. Reoperations and revisions were collected prospectively as part of the local database. Patients participated in surveys preoperatively and at every annual follow-up which included the Foot and Ankle Outcome Score (FAOS). Patients were also evaluated with weightbearing radiographs preoperatively, at the 3 months postoperative and at the 5 year-mark. Those were analyzed by looking at the implant position with validated angles and comparing those over time. Further statistical analysis used paired t-test and Mann-Whitney U test. Results: The survivorship for our cohort was 92% at the 5-year mark. Three patients had the implant extracted at 12 and 15 months postoperative. Two of those patients had revisions to stemmed TARs and one had a below-knee amputation. Reoperations otherwise included 4 fibular hardware removal and 5 medial gutter debridement. As seen in Table 1, the FAOS improved significantly for all domains at 5-year compared to preoperative status. The Pain and Symptoms domains improved above than the MCID. The implant positioning both tibial coronal and sagittal as well as talar sagittal did not significantly change between 3 months and 5 years postoperative. Conclusion: This study describes the use of a laterally based Trabecular Metal TAR with great survivorship (92%) and clinically significant improvement in patient-reported outcomes. The rate of reoperation is higher due to prominent lateral hardware or poorly visualized medial gutters and revisions had to be performed through an anterior approach. Few other studies report 5-year outcomes from this prosthesis. There is a growing need to present more data from different centers to guide its ongoing clinical use.