Increased risk of deep vein thrombosis and post-operative delirium following total knee arthroplasty compared with unicompartmental knee arthroplasty in patients aged 80 years and older: A nationwide Japanese medical claims-based propensity score-matched study

Purpose: As life expectancy increases, the number of elderly patients undergoing knee arthroplasty continues to rise. Total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA) are both viable options, yet comparative data on post-operative risks in very elderly patients are limited. The aim of this study was to compare in-hospital post-operative complications between TKA and UKA in patients aged ≥80 years using a large-scale Japanese nationwide database derived from Diagnosis Procedure Combination (DPC)-participating acute care hospitals. Methods: A retrospective cohort study was conducted using the DPC database from 2016 to 2023. Patients aged ≥80 years undergoing TKA or UKA were identified. Propensity score matching (1:1) was used to balance baseline characteristics, including age, sex, body mass index, Charlson comorbidity index, anesthesia type, and simultaneous bilateral surgery. Outcomes included deep vein thrombosis (DVT), cognitive dysfunction, pneumonia, cerebrovascular events, surgical site infection, in-hospital mortality, length of stay, discharge disposition, and blood transfusion volume. Results: After matching, 7782 TKA and 7782 UKA patients were analyzed. TKA was associated with higher rates of DVT [9.0% vs. 6.0%; odds ratio 1.56; p ​< ​0.0001] and post-operative delirium (1.6% vs. 0.7%; odds ratio 2.31; p ​< ​0.0001). Additionally, surgical site infections were more frequent and transfusion volumes were greater in TKA. UKA patients had shorter hospital stays and higher rates of discharge to home (75.3% vs. 65.4%). Conclusions: In patients aged ≥80 years, TKA was associated with higher risks of DVT and cognitive dysfunction compared with UKA. Given the observational design, causal inference is limited. UKA may be a safer option in appropriately selected patients.