Transfibular Total Ankle Replacement: Midterm Outcomes in 251 Consecutive Cases

Research Type: Level 4 – Case series Introduction/Purpose: In contrast to other modern total ankle arthroplasty (TAA) designs, 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. Previously we reported excellent midterm survivorship in 130 ankles. Here we present a follow-up study by a single surgeon analyzing the implant 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 January 2020. Inclusion criteria included: minimum 5-years of follow-up, patient-reported outcomes measures (PROM), and radiographs. 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 cysts (lucency >2mm) 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 251 ankles (237 patients) with average follow-up of 6.9 years (range, 5.0-12.1) were included in the study. The average age was 59.9 years-old, with 48.5% being females. Results: Postoperative PROMs included SF-12 PCS: 42.0; SF-12 MCS: 54.8; VAS: 2.3; AOS Pain: 19.2; AOS Disability: 27.0. Postoperative tibiopedal ROM was 18.2° dorsiflexion and 21.6° plantarflexion; tibiotalar ROM was 9.1° dorsiflexion and 18.0° plantarflexion. A total of 9 (3.6%) ankles had at least one cyst, most commonly located about the posterior talar component (Zone 12), with no patients having more than 2 cysts. Reoperation rate was 35.1% (n=88) at average 25.5 months, most commonly medial gutter debridement (n=36, 14.3%). One (0.4%) implant revision was performed for tibial component subsidence. There were 9 (3.6%) cases of acute infection, 6 requiring polyethylene exchange, 3 requiring only I&D and removal of fibular hardware. Overall implant survival, defined by retention of the metal components, was 99.6%. Conclusion: Midterm outcomes of the transfibular TAA continue to demonstrate sustained improvements with respect to patient-reported outcomes and radiographic alignment. A third of patients may require elective reoperations, most commonly for medial gutter impingement. There is a relatively low incidence of periprosthetic cysts and component failure requiring revision during this time period, and there were no incidences of fibular nonunion.