Outcomes following functionally aligned total knee arthroplasty in severe varus deformity.

Introduction: Total knee arthroplasty (TKA) in severe varus deformity still remains a challenge. Alternative alignment TKA aims to improve outcomes and satisfaction. The purpose of this study is to report on the outcomes of a functionally aligned TKA in severe varus deformity. Methods: This is a retrospective review of single surgeon series. 92 patients with a varus deformity of >15⁰ on varus stress underwent a functionally aligned, TKA (Stryker Triathlon, Mahwah, New Jersey, USA) between 2016 and 2022. A control group, matched for age, gender and body mass index (BMI) from the same period was also identified with mild varus deformity (<10⁰). Intra-operative robotic data collected included gap measurements, bone resection depths, alignment, and rate of soft tissue releases. Clinical outcome data was collected as part of the prospective registry which included patient reported outcome measures (Forgotten Joint Score 12, Oxford Knee Score and Knee Injury and Osteoarthritis Outcome Score Joint Replacement), pain Visual analogue score (VAS), patient satisfaction and range of motion. We reported a minimum follow-up of 12 months. Results: Medial soft tissue release was performed in 7.6 % of patients in the severe varus group. No soft tissue release was required in the control group. 96.7 % of TKAs achieved coronal balance in extension within 1 mm in the severe varus group. The varus stressed Hip knee ankle angle (HKA) was corrected by 8.5⁰ (95 % CI -9.4 to -7.6, p < 0.001). Patients in both group achieved excellent clinical outcomes scores and satisfaction (Severe varus: 91.9 % vs control: 92.7 %) at the final follow-up. Conclusion: Patient with severe varus deformity (>15⁰) undergoing a functionally aligned TKA achieve a well-balanced TKA with excellent clinical outcomes and small rates of soft tissue release.