The outcomes of complex primary Inbone total ankle replacement

A. Jamalfar, M. Kakwani, R. Kakwani, D. Townshend, A. Murty

Introduction: The Inbone prothesis is a third-generation total ankle arthroplasty (TAAs), consisting of modular stem components inserted into the tibia and talus. In comparison to other prostheses, the Inbone offers increased stability, structural support and improved correction of malalignment and revisions. This is at the expense of more bone excision compared to resurfacing type of prosthesis. We present the radiological, functional and operative outcomes of all consecutive patients operated with the Inbone prosthesis at our institute.

Methodology: All patients with a primary Inbone prosthesis operated at our trust, from June 2013 to June 2021, were included. Patient demographics, indications using the Canadian Orthopaedic Foot and Ankle Society (COFAS) ankle arthritis classification system, complications and radiological outcomes were recorded. Functional outcomes reported by the patients included: Manchester-Oxford Foot Questionnaire (MOXFQ), EuroQol-5 Dimension (EQ-5D) and the Visual Analogue Score (VAS).

Results: Total of 69 patients underwent primary Inbone TAA (M:F 47:23; average age = 71 years; range: 48 to 90 years). According to the COFAS grading system, patients included in the study were Grade 1 (1 patient) Grade 2 (13 patients) Grade 3 (20 patients) Grade 4 (29 patients). The minimum follow-up was 1 year (range: 1 to 8 years). Overall, there was a statistically significant improvement in the average outcome score (pre/post-operation): 62/29 in MOXFQ, EQ5D Index value of 0.39/0.69, and VAS scores of 26.7/10.0. However EQ5D VAS score of 69.9/70.5 was not statistically significant (p=0.82). The average improvement in the coronal deformity correction was 9 degrees. There were no implant revisions. Complications included a periprosthetic fracture of the distal tibia and two cases of DAIR procedure.

Conclusion: The Inbone TAA is a safe and successful procedure for end stage ankle arthritis with deformities around the foot and ankle.