The psoas muscle index as a useful predictor of total hip arthroplasty outcomes

Introduction The aim of this study is to assess the association between the psoas muscle index (PMI) and total hip arthroplasty (THA) outcomes. This is a critical issue as sarcopenia has been associated with poor patient satisfaction post-THA. Materials and methods This was a retrospective case–control study of 205 THAs, with a mean follow-up of 3.6 (range, 2.0–5.5) years. Age, sex, serum immune markers, spinopelvic parameters, PMI (quantified as the cross-sectional area of the psoas, bilaterally, at L3 divided by the individual’s height squared), and patient-reported outcomes were compared between patients ‘with’ ( n = 118) and ‘without’ ( n = 87) achievement of a minimum clinically important difference (MCID) improvement in the EuroQol 5-Dimension (EQ-5D), post-THA. Logistic regression and receiver operating characteristic curve analyses were used to identify predictive factors. Results A ≥ MCID improvement in the EQ-5D was associated with the PMI (odds ratio, 0.75; 95% confidence interval, 0.63–0.91; P = 0.028), prognostic nutritional index (odds ratio, 0.85; 95% confidence interval, 0.45–0.94; P = 0.043), and age (odds ratio, 1.09; 95% confidence interval, 1.01–1.18; P = 0.044). After adjusting the PMI threshold to 4.0 cm 2 /m 2 for females and 6.4 cm 2 /m 2 for males, there were significant differences in serum factors ( P = 0.041 for albumin and P = 0.016 for a prognostic nutritional index