Clinical screening for sarcopenic obesity in patients with end-stage knee osteoarthritis

Abstract

Purpose: In adults with end-stage knee osteoarthritis (OA), a body mass index (BMI) ≥30 kg/m2 is associated with increased surgical risk in total knee arthroplasty (TKA). To our knowledge, no studies have examined the influence of sarcopenic obesity on TKA outcomes. Sarcopenic obesity, a phenotype of low muscle mass and high fat mass, may be present in adults with knee OA but missed by clinical assessments that only consider BMI. Sarcopenic obesity has been shown to impact infection rates and surgical outcomes in other clinical populations, but it has not been thoroughly investigated in patients with OA. The purpose of this cross-sectional study was to examine the prevalence of sarcopenic obesity in adults with unilateral or bilateral end-stage knee OA, and to determine which assessments completed in the clinical setting might be useful to identify this subgroup of patients. Methods: Patients with a BMI ≥30 kg/m2 and end-stage knee OA being screened for TKA were included. Body composition was measured in n=151 adults (59% female, mean age 65.1±7.9 years, mean BMI 37.1±5.5 kg/m2) using dual-energy x-ray absorptiometry (DXA). Appendicular skeletal muscle mass (ASM) was calculated and adjusted by BMI. Sarcopenic obesity was classified by low ASM/BMI (using previously published cut-points of <0.512 kg/m2 in females and <0.789 kg/m2 in males) and dichotomized into those with or without sarcopenic obesity. Physical function was assessed using 4 metre gait speed, the six minute walk test (6MWT), and maximal grip strength (absolute and adjusted by BMI). Logistic regression models were built using clinical variables (including age, sex, and physical function) to discriminate the outcome of sarcopenic obesity. Receiver operating characteristic (ROC) curves and area under the curve (AUC) were used to test which model best identified the presence or absence of sarcopenic obesity. Results: Prevalence rates for sarcopenic obesity were 27% in this cohort, with differences between sexes (37% in males vs. 20% in females, p=0.022). Three prediction models, all controlled for sex, had moderate discriminating power to identify sarcopenic obesity in this cohort: relative grip strength (grip strength/BMI) alone (AUC 0.774), gait speed with absolute grip strength (AUC 0.737), and 6MWT with absolute grip strength (AUC 0.741), all p<0.001. Age did not contribute significantly to any of the prediction models. Conclusions: Sarcopenic obesity is prevalent in adults with end-stage knee OA, particularly males, suggesting increased screening and awareness of this condition is warranted to determine its influence on TKA outcomes. Relative grip strength is a simple measure to screen for possible sarcopenic obesity in the clinical OA setting, requiring only measurement of height, weight and grip strength. Patients awaiting TKA with low relative grip strength should be evaluated for sarcopenic obesity and managed appropriately prior to surgery.