Immune thrombocytopenic purpura as a predictor of postoperative complications in total knee arthroplasty: A nationwide cohort study.

Abstract

Total knee arthroplasty (TKA) is one of the most common joint replacement procedures in the United States, with increasing use among medically complex populations. Immune thrombocytopenic purpura (ITP), a rare autoimmune disorder marked by low platelet counts, may increase the risk of adverse postoperative outcomes. We conducted a retrospective cohort study using the TriNetX Research Network, which includes de-identified electronic health records from over 74 million U.S. patients. Patients undergoing primary total knee arthroplasty (TKA) between 2005 and 2023 were identified using CPT code 27447. Immune thrombocytopenic purpura (ITP) was defined using ICD-9 code 287.3 and ICD-10 code D69.3 within one year prior to surgery. ITP patients were compared to non-ITP controls before and after 1:1 propensity score matching. Postoperative complications were identified using ICD codes. Odds ratios (ORs) and 95 % confidence intervals (CIs) were reported; p < 0.05 was considered significant. We identified 3817 ITP patients and 233,543 non-ITP controls, with 3817 matched pairs in the final analysis. ITP was associated with increased odds of several postoperative complications. Infectious outcomes included higher rates of wound dehiscence (OR = 2.77), periprosthetic joint infection (OR = 5.40), and pneumonia (OR = 2.44) (all p < 0.001); deep surgical site infection was elevated pre-matching. Hematologic and cardiovascular complications included blood loss anemia (OR = 2.58), acute renal failure (OR = 2.67), and myocardial infarction (OR = 4.20). VTE events were more common, including deep vein thrombosis (OR = 2.44) and pulmonary embolism (OR = 2.90). Mechanical complications included periprosthetic fracture (OR = 3.18) and mechanical failure (OR = 4.20) (all p ≤ 0.002). ITP was a significant risk factor for complications following TKA, underscoring the need for preoperative risk stratification and tailored perioperative management in this high-risk population.