BACKGROUND

While most total ankle arthroplasty (TAA) procedures utilize an anterior approach for implantation, the Zimmer Biomet Trabecular Metal implant is unique in that it utilizes a lateral transfibular approach. We present the largest mid-term study to date to analyze the implant survivorship and clinical and radiographic outcomes of transfibular TAA at a minimum 5-year follow-up.

METHODS

We retrospectively identified and evaluated 130 ankles (122 patients; mean age, 60.8 years; 50% female) with a mean follow-up of 5.9 years (range, 5.0 to 10.1 years) after primary TAA performed between October 2012 and December 2018. Patient-reported outcome measures (PROMs) included the 12-item Short Form Health Survey (SF-12) Physical Component Summary (PCS) and Mental Component Summary (MCS), Ankle Osteoarthritis Scale (AOS) for pain and disability, and visual analog scale (VAS) for pain. Radiographic measurements for range of motion, coronal and sagittal alignment, and implant subsidence were evaluated. The presence of periprosthetic radiolucency was determined using a 12-zone classification system. Adverse events were reported using the Canadian Orthopaedic Foot and Ankle Society (COFAS) Reoperation Coding System (CROCS).

RESULTS

The cohort had mean postoperative values of 41.5 for the SF-12 PCS, 54.9 for the SF-12 MCS, 2.3 for VAS pain, 19.1 for AOS pain, and 28.5 for AOS disability. The postoperative tibiotalar range of motion was 7.5° of dorsiflexion and 17.3° of plantar flexion. A total of 42 valgus ankles (mean coronal tibiotalar angle, 10.4°; range, 1.0° to 25.3°) and 44 varus ankles (mean, -9.1°; range, -1.0° to -25.0°) were corrected to neutral. Twenty-six ankles (20%) had 1 zone of radiolucency, and none of the ankles had >7 zones. There were 3 cases of cysts (2.3%) and 0 cases of subsidence, septic or aseptic loosening, or fibular nonunion. Adverse events occurred in 47 ankles (36.2%) at a mean of 26.7 months, with the most common reoperation being medial gutter debridement (22 ankles; 16.9%). There were 2 ankles (1.5%) with acute infection treated with debridement, antibiotics, and polyethylene exchange with metal component retention. Overall implant survivorship, defined as retention of the metal components, was 100% at the time of final follow-up.

CONCLUSIONS

The clinical and radiographic data in this study suggest that transfibular TAA is an effective and durable treatment option for end-stage ankle arthritis, with excellent mid-term implant survivorship. Periprosthetic radiolucency was limited and did not lead to implant subsidence or loosening. The most common reoperation was medial gutter debridement.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.