Midterm Outcomes of Transfibular Total Ankle Arthroplasty: Clinical and Radiographic Analysis of 130 Cases with Minimum 5-Year Follow-Up

Category: Ankle Arthritis; Ankle Introduction/Purpose: The current fourth generation of total ankle arthroplasty (TAA) continues to build upon previous advances in implant design. In contrast to these implants, which utilize a traditional anterior approach for implantation, the Zimmer Trabecular Metal Total Ankle (Zimmer-Biomet, Warsaw, IN) is unique in that it utilizes a transfibular approach to the ankle. This allows for a shallow resection depth, and the insertion of a curved prosthesis design, mimicking the native tibiotalar joint. While previous case-series have reported on implant survivorship, a comprehensive midterm study of the clinical and radiographic outcomes of this system is limited. Here we present the largest midterm study to date by a single-surgeon, and analyze the survivorship, clinical, and radiographic outcomes of the transfibular TAA at a minimum of 5-years follow-up. Methods: Retrospective review was performed on prospectively followed patients who underwent primary transfibular TAA by a single surgeon from October 2012 to December 2018. Inclusion criteria included: minimum 5-years of follow-up. patient-reported outcomes measures (PROM), and radiographic follow-up. Patient demographics and perioperative data were collected. PROMs included: 12-item Short Form Health Survey (SF-12) physical (PCS) and mental (MCS) component scores, Ankle Osteoarthritis Scale (OAS), and Visual Analog Scale (VAS). Functional outcomes included range of motion (ROM) measured on weightbearing ROM radiographs. Radiographic outcomes included coronal and sagittal alignment, and evaluation of periprosthetic lucency utilizing a 12-zone system. Adverse events and reoperations were reported using the Canadian Orthopedic Foot and Ankle Society (COFAS) Reoperation Coding System (CROCS). A total of 130 ankles (122 patients) with average follow-up of 5.9 years (range, 5.0-10.1) were included in the study. The average age was 60.8 years-old, with 50.8% being females. Results: Postoperative PROMs included SF-12 PCS: 41.5; SF-12 MCS: 54.9; VAS: 2.3; AOS Pain: 19.1; AOS Disability: 28.5. Postoperative tibiopedal ROM was 17.7° dorsiflexion and 21.8° plantarflexion. Postoperative tibiotalar ROM was 7.4° dorsiflexion and 17.3° plantarflexion. A total of 26 (20%) ankles had a single zone of lucency, while 7 (5.4%) ankles had 6 or more; none had more than 7 zones. There were no cases of cysts, subsidence, septic/aseptic loosening, or fibular non-union. Reoperation rate was 36.2% (n=47) at average 26.7 months, most commonly removal of fibula hardware (n=28, 21.5%), medial gutter debridement (n=18, 13.8%). There were 5 (3.8%) cases of acute infection treated with I&D and metal component retention. Overall implant survival, defined by retention of the metal components, was 100%. Conclusion: Transfibular TAA is an effective durable treatment option for end-stage ankle arthritis with excellent implant survivorship, providing sustained improvements in clinical and radiographic outcomes at the midterm. Reoperations were mostly elective removal of fibular hardware or medial impingement. There was 100% retention of the metal components. Deformity correction was achieved and maintained. The majority of ankles had no radiographic lucencies and only 20% had a single zone out of 12 zones which did not correlate with clinical outcomes. There were no cysts, subsidence, or fibular non-unions.