Age-adjusted Charlson Comorbidity Index as an effective tool for the choice between simultaneous or staged bilateral total knee arthroplasty

Introduction: The choice between simultaneous and staged bilateral total knee arthroplasty (BTKA) remains controversial. Age-adjusted Charlson Comorbidity Index(CCI) is a promising tool for risk-stratification. We aimed to compare the outcomes between patients who underwent simultaneous and staged BTKA, stratified by age-adjusted CCI scores. Materials and methods: We conducted this retrospective, single-surgeon case series from 2010 to 2020. This study consisted of 1558 simultaneous BTKA and 786 staged BTKA procedures. The outcome domains included 30-day and 90-day readmission and 1-year reoperation events. We performed multivariate regression analysis to compare the risk of readmission and reoperation following simultaneous and staged BTKA. Other factors included age, sex, body mass index, diabetes mellitus, rheumatoid arthritis, smoking, receiving thromboprophylaxis and blood transfusion. Results: The rates of 30-day, 90-day readmission and 1-year reoperation following simultaneous BTKA was 1.99%, 2.70% and 0.71%, respectively. The rates of 30-day, 90-day readmission and 1-year reoperation following staged BTKA was 0.89%, 1.78% and 0.89%, respectively. For patients with age-adjusted CCI ≥ 4 points, simultaneous BTKA was associated with a higher risk of 30-day (aOR:3.369, 95% CI:0.990-11.466) and 90-day readmission (aOR:2.310, 95% CI:0.942–5.668). In patients with age-adjusted CCI ≤ 3 points, the risk of readmission and reoperation was not different between simultaneous or staged BTKA. Conclusion: Simultaneous BTKA was associated with an increased risk of short-term readmissions in patients with age-adjusted CCI ≥ 4 points but not in those with age-adjusted CCI ≤ 3 points. Age-adjusted CCI can be an effective index for the choice between simultaneous and staged BTKA procedures.