Transfibular Total Ankle Arthroplasty: Clinical, Functional, and Radiographic Outcomes and Complications at a Minimum of Five Years Follow-up

Category: Ankle Arthritis; Ankle Introduction/Purpose: Total ankle arthroplasty (TAA) has surpassed arthrodesis as the gold standard for treatment of end-stage ankle arthritis. The Zimmer Trabecular Metal Total Ankle Implant (Zimmer-Biomet, Warsaw, IN) differs from other newer- generation implants in the transfibular approach, non-mobile-bearing prosthesis, high-molecular-weight polyethylene, curved surface at every interface in the sagittal plane, and shallow resection depth. There is limited mid-term follow-up for this system. Therefore, we sought to report mid-term clinical, functional, and radiographic results we well as complications and survival for patients treated with the transfibular TAA at a minimum of 5-years follow-up. Methods: A retrospective review was performed on patients who underwent primary transfibular TAA by a single surgeon from October 2012 to January 2018. Inclusion criteria was a minimum of 5-years of follow-up with a completed consent for participation in the study and patient-reported outcome measures (PROM). 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. Adverse events and reoperations were reported using the Canadian Orthopedic Foot and Ankle Society (COFAS) Reoperation Coding System (CROCS). Of the consecutive 151 TAAs, 83 (55.0%) ankles are included in this study, evaluated at a mean of 5.8 years clinical and 6.3 years radiographic follow-up. Results: The average age was 60.6 years-old. Preoperative tibiotalar coronal deformity included 27 valgus (10°, range 2-20°) and 25 varus ankles (-9°, range -2--25°), successfully corrected to neutral postoperatively. The postoperative PROMs were: SF-12 PCS: 40.4, SF-12 MCS: 56.0, VAS: 2.3, AOS Pain: 17.0, and AOS Disability: 24.9. Radiographic postoperative tibiopedal ROM was 17.8° dorsiflexion and 21.8° degrees plantarflexion. The overall reoperation rate was 38.6%(n=32) at an average of 28.7 months postoperative. Most common were removal of the fibula hardware (n=21,25.3%) and medial gutter debridement (n=15, 18.1%). There were 3 (3.6%) cases of acute postoperative infection (< 3 months) treated with operative irrigation and debridement but retention of the metal components. There were no cases of septic or aseptic loosening or subsidence. The overall implant survival, defined by retention of the metal components, was 100%. Conclusion: Transfibular TAA is a safe and effective treatment for end-stage ankle arthritis at 5-year mid-term follow-up. This study confirms excellent clinical results including PROMs and ROM as well as radiographic alignment correction and maintenance. The survival rate was 100% for retention of the trabecular metal components. The survival rate to reoperation was 60.7% with patients commonly requiring removal of the fibula hardware or medial gutter debridement. Patients should be counseled on the risk of reoperation preoperatively for postoperative expectation management.