Moderate and severe coronal plane deformity corrected with the Infinity ankle prosthesis

H. Tribe, K. Pearce, H. Fraig, H. Taylor

Selected ankle arthroplasty implants have been shown to be suitable for patients with end-stage ankle arthritis and significant coronal plane deformity. The outcomes using the Infinity prosthesis in this patient group are currently unknown. Our aim was to evaluate the outcomes of patients undergoing ankle arthroplasty using the Infinity prosthesis with a preoperative coronal plane deformity of 10-20 degrees (moderate) and 20 degrees or greater (severe).

We identified patients who had undergone a primary ankle arthroplasty from 2014 to 2022. From the total of 103 patients, 25 patients had a moderate deformity (10-20 degrees) and four patients had a severe deformity (>20 degrees). Of these patients, 17 (59%) patients had a varus deformity and 12 (41%) had a valgus deformity. The mean age was 72 years. Mean length of follow-up was 34 (range 12-71) months.

The mean preoperative coronal plane deformity was 15.84 (range 10.4 to 29.7) degrees. The mean immediate postoperative deformity was 1.8 (range 0.2 to 6.5) degrees. The mean deformity at final follow-up was 3.8 (range 0.3 to 12.5) degrees. The difference between preoperative deformity and final correction was statistically significant (p <0.0001). There was no significant difference between initial and final postoperative correction, nor between the moderate and severe groups. Overall, recurrence of coronal plane deformity occurred in 3 patients (10.3%). Manchester-Oxford Foot Questionnaire scores and visual analogue scale scores were recorded at final follow-up and the scores were equivalent to previously published data. Correction of the coronal plane deformity was achieved by using intraoperative softtissue balancing, including lateral ligament reconstruction in three patients. Tibial bone cysts were seen in two patients, leading to tibial tray subsidence in one patient.

Stable correction of moderate and severe coronal plane deformity in end-stage ankle arthritis can be reliably achieved with the infinity prosthesis using only soft-tissue balancing procedures.