Simultaneous bilateral total knee arthroplasty has higher risk of asymptomatic deep vein thrombosis in patients in their 80s compared with unilateral total knee arthroplasty: a propensity score-matched comparative study across different age groups

Introduction This study compared complications and clinical outcomes between simultaneous bilateral total knee arthroplasty (SBTKA) and unilateral total knee arthroplasty (UTKA) across different age groups. Materials and methods This retrospective single-center study included 939 consecutive patients aged 60-89 years who underwent primary total knee arthroplasty between 2019 and 2023. After applying propensity score matching for preoperative deep vein thrombosis (DVT), American Society of Anesthesiologists (ASA) classification, and preoperative functional activity according to the Knee Society Score 2011 (KSS) to 223 patients who underwent SBTKA and 716 patients who underwent UTKA, SBTKA and UTKA were compared in the following age groups: 60s (28 vs. 28), 70s (110 vs. 110), and 80s (60 vs. 60). Perioperative complications and clinical outcomes at 1 year after surgery were compared between SBTKA and UTKA. Lower limb Doppler ultrasound was performed to screen for asymptomatic DVT preoperatively and on postoperative day 7. Results Average ASA classification ranged from 2.0 to 2.2 across all age groups, with no difference between SBTKA and UTKA. Compared with UTKA, the decrease in hemoglobin was significantly greater after SBTKA in patients in their 70s and 80s (both p < 0.001). The proportion of blood transfusion showed no significant difference across all age groups. Asymptomatic DVT was more frequent after SBTKA than after UTKA in patients in their 80s (58.3% vs. 40.0%, p < 0.045), but not those in their 60s (42.9% vs. 32.1%) or 70s (50.9% vs. 46.3%). Clinical outcomes (knee symptoms, patient satisfaction, patient expectations, functional activity according to the KSS) were comparable between SBTKA and UTKA across all age groups at 1 year postoperatively. Conclusions SBTKA had higher risk of asymptomatic DVT in patients in their 80s. With evaluation of risk factors and careful patient selection, SBTKA is a valid option in terms of safety and clinical outcomes in elderly patients with ASA 2.