Early to mid-term results of fixed-bearing total ankle arthroplasty with a modular intramedullary tibial component.

BACKGROUND: There has been a continuing increase in the use of total ankle arthroplasty for the treatment of end-stage ankle arthritis. Our aim was to determine the clinical, radiographic, and functional outcomes of total ankle arthroplasties done with a prosthesis with a modular intramedullary stem and intramedullary referencing to align the tibia.

METHODS: A consecutive series of patients who underwent total ankle arthroplasty with the INBONE Total Ankle Replacement from June 2007 to December 2010 were enrolled in this study. Pain and patient-reported function were assessed with use of a visual analog scale (VAS) for pain, the American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score, the Short Musculoskeletal Function Assessment (SMFA), and the Short Form-36 (SF-36) Health Survey. Objective function was measured with assessment of walking speed, the Timed Up and Go (TUG) test, the Sit-to-Stand (STS) test, and the Four Square Step Test (4SST). Standardized weight-bearing radiographs obtained preoperatively and after total ankle arthroplasty were evaluated. We analyzed clinical, functional, and radiographic measurements with a series of repeated-measures analyses of variance (ANOVAs) with post-hoc testing to assess differences between preoperative, one-year postoperative, and most recent follow-up data. On the basis of the number of statistical comparisons, a Bonferroni correction was completed (alpha < 0.003).

RESULTS: We identified 194 primary INBONE total ankle arthroplasties with a mean duration of clinical follow-up of 3.7 years (range, 2.2 to 5.5 years). Patients demonstrated a significant improvement (p < 0.003) in VAS pain, AOFAS, SMFA, and SF-36 scores at the time of final follow-up, compared with preoperative values, and in walking speed, STS time, TUG time, and 4SST time at two years postoperatively, compared with preoperatively. The mean coronal tibiotalar angle for varus and valgus ankles significantly improved postoperatively and was maintained until the time of final follow-up. The prevalence of unstable subsidence leading to impending failure was 5%, and the prevalence of revision was 6%.

CONCLUSIONS: Patients who underwent total ankle arthroplasty with the INBONE Total Ankle Replacement demonstrated significant improvement in radiographic, functional, and patient-reported outcome scores at a mean of 3.7 years postoperatively. The overall implant survival rate was 89%.

LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.