Metabolic syndrome and the functional outcomes of hip and knee arthroplasty

Patients with an elevated systemic inflammatory state are known to report greater pain with knee osteoarthritis (OA). We investigated the influence of risk factors of metabolic syndrome (MetS) on patient function before and after hip and knee replacement surgery.

A total of 677 consecutive patients with primary knee replacement and 547 consecutive patients with primary hip replacement with at least one MetS risk factor were reviewed from our joint registry. Demographic variables of age, sex, and comorbidity were retrieved. MetS risk factors were defined as body mass index (BMI) > 30 kg/m(2), diabetes, hypertension, and hypercholesterolemia. Baseline and 1-year Western Ontario McMaster University Osteoarthritis Index (WOMAC) scores were compared across patients by number of MetS risk factors, ranging from 1 to 4. Linear regression modeling was used to evaluate the effects of the MetS risk groups and the individual metabolic abnormalities on predicting baseline and 1-year WOMAC scores. Knee and hip patients were reviewed separately.

The knee and hip patients showed a significant difference in sex distribution, BMI, and mean comorbidity across risk groups (p < 0.05). Unadjusted analysis showed that baseline and 1-year WOMAC scores, for both knee and hip patients, increased significantly with increasing number of MetS risk factors (p < 0.05). The linear regression model with the individual metabolic abnormalities was found to be more predictive of outcome than one with the number of MetS risk factors. Hypertension and obesity were the metabolic factors most predictive of a poorer outcome following hip surgery as compared to just obesity for knee patients.

Patient function following joint replacement surgery, particularly hip surgery, is negatively affected by metabolic abnormalities perhaps secondary to the systemic proinflammatory state. This knowledge should be used when counseling patients prior to surgery.