Implant size distribution and mid-term outcomes of transfibular total ankle arthroplasty in a Japanese cohort

Aims: Total ankle arthroplasty (TAA) is a widely accepted alternative to ankle arthrodesis for end-stage ankle arthritis. Preserving ankle motion is particularly relevant in Japanese populations, in which kneeling and squatting are integral to routine activities. However, Japanese individuals generally have smaller bone morphology than Western patients, raising concerns regarding the suitability of implant size variations originally designed for Western populations. This study aimed to examine implant size distribution, clinical and radiological outcomes, and implant survival rate following transfibular TAA in a Japanese cohort. Methods: This retrospective analysis included 50 patients (51 ankles) who underwent transfibular TAA between March 2019 and October 2022 with three or more more years of follow-up (mean 4.3 years (3.0 to 6.0, SD 0.9)). Clinical outcomes were evaluated preoperatively and at three, six, 12, and 24 months postoperatively, and at final follow-up using the Self-Administered Foot Evaluation Questionnaire (SAFE-Q) and ankle range of motion. Radiological assessment comprised the lateral distal tibial angle, anterior distal tibial angle, tibiotalar angle, and tibiotalar ratio. Complications and implant survival were analyzed using Kaplan-Meier curves, with implant removal as the endpoint. Results: Smaller implant sizes predominated, with size 2 (33.3%) and size 3 (37.3%) used most frequently; no patients required size 5 or 6. All SAFE-Q domains improved significantly from baseline, with mean changes exceeding the minimal clinically important difference. Range of motion increased by three months postoperatively and subsequently stabilized. Radiological parameters demonstrated satisfactory alignment and reduced coronal variance. Delayed wound healing occurred in 15.7% and medial malleolar fractures in 9.8%; all cases achieved bone union without additional intervention. Implant survival rate was 98.0% at three years and 95.5% at four years. Conclusion: Transfibular TAA produced favourable mid-term clinical, radiological, and survival outcomes in Japanese patients. The available implant size range adequately accommodated the smaller ankle morphology typical of Japanese patients. These findings may inform implant development and preoperative planning for populations with similar anatomical characteristics.