Early Clinical and Radiographic Outcomes of Intramedullary-Fixation Total Ankle Arthroplasty

Background: The present study evaluated the early clinical outcomes, radiographic parameters, and survivorship of first and second-generation INBONE intramedullary-fixation total ankle arthroplasties.

Methods: Fifty-nine primary total ankle arthroplasties utilizing INBONE I or II implants were performed in fifty-nine patients (thirty-one men and twenty-eight women; mean age, 57.2 years) from 2008 to 2012. The AOFAS (American Orthopaedic Foot & Ankle Society) ankle-hindfoot score and VAS (visual analog scale) pain score were recorded preoperatively and at the time of the latest follow-up. Weight-bearing radiographs were used to determine ankle motion and assess component alignment and subsidence. Intraoperative and postoperative complications, reoperations, and failures were evaluated.

Results: All fifty-nine patients were available for follow-up at least two years after surgery; the mean follow-up duration was 35.0 ± 11.9 months. The estimated survival rate at two years was 96.6% in the entire cohort (91.3% in the INBONE I group and 100% in the INBONE II group) when revision of the tibial and/or the talar component was used as the end point. The mean AOFAS ankle-hindfoot score improved from 44.1 to 87.3 at the time of the latest follow-up (p < 0.01), and the mean VAS pain score improved from 8.1 to 1.6 (p < 0.01). Mean total ankle motion improved from 29.0° to 38.0° (p < 0.01). Fourteen patients (24%) required a reoperation because of a postoperative complication. Five of these patients (four with INBONE I implants and one with INBONE II implants; 8% of the entire cohort) required revision surgery at a mean of 32.4 months (range, fifteen to fifty-eight months) because of symptomatic talar subsidence. Talar revisions utilized an INBONE II implant with a pegged talar sulcus for definitive management. The patients who underwent revision surgery had mean total ankle motion of 41.6°, neutral alignment, and no further reoperations at the time of the latest follow-up.

Conclusions: Early results of INBONE intramedullary-fixation total ankle arthroplasty demonstrated improved patient-reported outcomes and increased ankle motion at a minimum follow-up of two years. Arthrofibrosis and talar subsidence were the main postoperative complications that required revision, and these predominantly affected the first-generation INBONE I implants.

Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.