Patients on Losartan Have Similar Rates of Manipulation Under Anesthesia After Total Knee Arthroplasty

Introduction Patients have identified knee stiffness as a factor contributing to postoperative dissatisfaction after total knee arthroplasty (TKA). Losartan is an angiotensin receptor blocker (ARB) that has demonstrated antifibrotic effects; however, the impact of perioperative losartan on arthrofibrosis after TKA is not well understood. Therefore, the purpose of this study was to determine if losartan exhibits antifibrotic benefits in patients who undergo TKA by decreasing the rates of manipulation under anesthesia (MUA), when compared to patients who are not taking losartan. Methods All patients who underwent primary TKA by fellowship-trained arthroplasty surgeons at a single institution from January 1^st, 2020 through December 31^st, 2023 were identified by Current Procedural Terminology (CPT) code (27447). Patient demographic and surgery-specific information was collected. Patients were grouped into cohorts based on the presence of a patient-reported active prescription for losartan in the perioperative period. A 3:1 propensity match was performed. The two cohorts underwent matching based on angiotensin-converting enzyme inhibitor prescription, cyclooxygenase-2 (COX-2) inhibitor usage, age, sex, body mass index, and race. Postoperative rates of MUA (CPT 27570) and MUA with lysis of adhesions (LOA) (CPT 29884) were calculated, and Knee Injury and Osteoarthritis Outcome Score (KOOS), Pain Catastrophizing Scale (PCS), and Mental Component Summary (MCS) scores were collected. Results Twenty-seven thousand two hundred and twenty patients who underwent primary TKA within the study period were identified. Prior to propensity matching, 25,219/27,220 (92.6%) did not have a prescription for losartan within the perioperative period and 2,001/27,220 (7.4%) had a prescription for losartan within the perioperative period. After propensity matching, cohorts consisted of 6,024 patients who did not have a prescription for losartan within the perioperative period and 2,008 patients who had a prescription for losartan. There was no significant difference in the rate of MUA between patients with (74/2,008 - 3.69%) or without (240/6,024 - 3.98%) a prescription for losartan (X² (1, N = 8032) = 0.3, p = 0.60). Additionally, there was no difference in the rate of MUA with LOA between patients with (12/2,008 - 0.60%) or without (18/6,024 - 0.30%) a prescription for losartan (X² (1, N = 8032) = 2.9, p = 0.09). The odds ratio for MUA and MUA with LOA between groups was 1.08 (95% confidence interval 0.8 to 1.4; p = 0.55) and 0.50 (95% confidence interval 0.2-1.0p = 0.06), respectively. Additionally, there was no significant difference between groups with regard to postoperative KOOS, PCS, or MCS scores. Conclusions There are similar rates of MUA after primary TKA during the first postoperative year in patients with and without a prescription for losartan. However, this should be interpreted with caution as we are underpowered to detect small differences for this relatively rare outcome. Additionally, we found no difference in postoperative KOOS, PCS, and MCS between patients taking losartan and those not taking losartan. Despite the antifibrotic properties of losartan, its clinical impact on arthrofibrosis after TKA may be limited.