Body Composition, Functional, and Nutritional Characteristics of Patients with Hip or Knee Osteoarthritis

Background: Body composition refers to the amounts of fat and lean tissues in the body. It is a superior measurement compared to simple assessments of body weight and other anthropometrics. Osteoarthritis (OA) is an important public health problem and one of the most common causes of disability among American adults. An estimated 67 million Americans will develop OA, many of whom will require surgical intervention. The majority of patients with hip or knee OA are obese, older and sedentary. These factors would make them prone to a body composition phenotype of concurrent excess fat and low lean tissue that has been associated with unfavorable health outcomes in other cohorts of patients. Although obesity (assessed by overall body weight or its derivatives) has been extensively studied in patients with OA, only a handful of these studies have investigated fat versus lean tissue contributions to OA outcomes. Furthermore, there is evidence to suggest that body composition abnormalities may be caused and perpetuated by abnormal nutrition and physical function. Objectives: The overall purpose of this study was to describe body composition, functional and nutritional characteristics of patients with hip or knee OA undergoing total hip arthroplasty (THA) or total knee arthroplasty (TKA) surgery and to investigate the relationship between abnormal body composition and surgical-related outcomes. Methods: In this prospective pilot study, patients scheduled for THA or TKA due to OA were recruited from August 2013 until February 2014 from the Tallahassee Orthopedic Clinic (TOC). Patients underwent body composition assessment using bioelectrical impedance analysis. Functional measurements included handgrip strength testing and questionnaires that comprised of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Activities of Daily Living (ADL), Aerobics Center Longitudinal Study Questionnaire, and the Falls Efficacy Scale, International (FES-I). Dietary data were collected through a 24-hour dietary recall. In a subset of patients, medical discharge summaries were analyzed to quantify surgical outcomes. Results: A total of 42 patients (66.7% females) with a mean age of 66 ± 10 years were included in this study. The body mass index (BMI) ranged from 21.5 to 55.0 kg/m2 with 69% of patients being classified as obese. A wide variability of fat mass (FM) and fat-free mass (FFM) was observed across the BMI spectrum. Patients reporting low back pain presented with lower FFM index (FFMI), p=0.026, as well as with significantly higher body fat percentage (p=0.049). Handgrip strength was positively correlated with FFMI (r=0.44, p=0.008), but not with other functional assessments. Total WOMAC scores were significantly correlated to FMI (r=0.34, p=0.039), while BMI trended towards significance. An overall low ADL score was observed and physical activity levels were most strongly negatively correlated with FMI (r=-0.46, p=0.006). FES-I was positively associated with numerous body composition compartments, the strongest of which was body fat percentage (r=0.48, p=0.024). In order to further explore the relationship between body composition and functional variables, individual assessments were dichotomized in function of both FM and FFM, on the basis of the idea that higher FM and lower FFM values would be associated with poorer physical function. Using this approach, different patterns of unfavorable physical function emerged among different body composition phenotypes. Overall, patterns of higher FM and lower FFM were associated with adverse outcomes. Average caloric intake was approximately 1700 kcals/day, with a mean protein consumption of 0.81 g/kg body weight/day. Protein intake was not associated with body composition variables. Conversely, iron intake was positively associated with FFMI (r=0.43, p=0.019) and average handgrip strength (r=0.43, p=0.020). Surgical outcomes were available for a small number of patients (n=16) and was not associated with any body composition, functional or nutritional characteristics. Nonetheless, pre-surgical blood creatinine (mg/dL) was positively associated with FFMI (r=0.60, p=0.040). Conclusion: The major findings of this study reveal a wide variability of body composition (FM and FFM) in patients with hip or knee OA despite BMI. Overall, FM and FFM were more strongly associated with functional assessments and low back pain compared to simple measures of body weight. We conclude that the assessment of body composition may be advantageous compared to simple anthropometric measurements when predicting poor functional status in patients with hip or knee OA. This remains to be tested in future larger studies with more in-depth and accurate body composition assessments.

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