Conversion of ankle arthrodesis to total ankle arthroplasty remains controversial. Although satisfactory outcomes have been published, not all foot and ankle surgeons performing total ankle arthroplasty have embraced this modality.
Twenty-three total ankle arthroplasties were performed in patients who had undergone a prior or an attempted ankle arthrodesis. The mean age at surgery was fifty-nine years (range, forty-one to eighty years), and the mean duration of follow-up was 33.1 months (minimum, twelve months). Indications for the procedure were symptomatic adjacent hindfoot arthritis (twelve patients) or symptomatic tibiotalar or subtalar nonunion (eleven) after tibiotalocalcaneal arthrodesis. We performed concomitant surgical procedures in eighteen ankles (78%), with the most common procedure being prophylactic malleolar fixation (70%). We prospectively evaluated clinical outcomes using the Short Form-36 (SF-36), Short Musculoskeletal Function Assessment (SMFA), and visual analog scale (VAS) for pain and assessed initial weight-bearing radiographs and those made at the most recent follow-up evaluation.
The mean VAS pain score (and standard deviation) improved from 65.7 ± 21.8 preoperatively to 18.3 ± 17.6 at the most recent follow-up evaluation (p < 0.001), with five patients being pain-free (VAS score = 0). The mean SMFA bother and function indexes improved from 55 ± 22.9 and 46.7 ± 12.6 preoperatively to 30.6 ± 22.7 and 25.4 ± 17.4 at the most recent follow-up visit (p = 0.001 and p < 0.001, respectively). The mean SF-36 total score improved from 37.7 ± 19.3 to 56.4 ± 23.1 (p = 0.002). The implant survival rate was 87%. Four (20%) of the tibial components and fourteen (70%) of the talar components that were not revised exhibited initial settling and then were seen to be stabilized radiographically without further change in implant position. Three total ankle replacements (13%) showed progressive talar subsidence, prompting revision. Ten patients (43%) had minor complications not requiring repeat surgery.
Short-term follow-up after conversion of ankle arthrodesis to total ankle arthroplasty demonstrated pain relief and improved function in a majority of patients. Patients who undergo this surgery frequently require concomitant procedures; we recommend prophylactic malleolar fixation when performing conversion total ankle arthroplasty. The rate of complications, particularly talar component settling and migration, is cause for concern. We do not recommend the procedure for ankle arthrodeses that included distal fibulectomy.