Dermatomyositis and polymyositis in total hip arthroplasty

Idiopathic inflammatory myopathies (IIM) are systemic autoimmune disorders such as dermatomyositis (DM), polymyositis (PM), inclusion body myopathy, and autoimmune necrotizing myopathy that, similar to osteoarthritis, affect quality of life and activities of daily living. Moreover, these patients are often burdened with chronic pain and disability; however, the outcomes and risk of total hip arthroplasty (THA) in this patient population remain unclear.

To evaluate 90-d complications and costs in patients with these conditions.

A retrospective case control study was designed by accessing data from the Medicare dataset available on the PearlDiver server. Patients with IIM, here, those with DM and PM were matched based on possible confounding variables to a cohort without these diseases and with the same 10-year risk of mortality as defined by the Charlson Comorbidity Index Score (CCI). Univariate and multivariate analysis were performed to evaluate complications and t-tests to evaluate 90-d Medicare reimbursements as markers of costs after THA.

The total sample was 1090 patients with each cohort comprised of 545. Females were 74.9% of the population. The mean CCI was 5.89 (SD 2.11). Those with IIM had increased rates of pneumonia [odds ratio (OR) 1.45, P < 0.001] and pulmonary embolism (OR 1.46, P = 0.035) and decreased hematoma risks (OR 0.58, P = 0.00). 90-d costs were on average $1411 greater for those with IIM yet not significantly different (P = 0.034).

Patients with IIM have an increased 90-d rate of pneumonia and pulmonary embolism concomitant with a decreased hematoma rate consistent with their pro-coagulatory state. Further attention to increased resource utilization in these patients is also warranted.