The effect of body mass index on the functional outcome of patients with hip replacement

Objective: The objective of this study is to investigate the association between body mass index (BMI) and the functional progress among patients with a recent hip replacement. Data suggest that a number of medical societies and organizations are restricting patient access to joint replacement surgeries based on the patient's BMI. This restriction seems to be related to the increased risk of complications, primarily wound infections, at the time of surgery. Few studies have been conducted on the relationship between BMI and outcomes during rehabilitation after hip replacement surgery. Design: Retrospective cohort study. Setting: All patients admitted to a rehabilitation hospital, with a recent diagnosis of hip replacement and available hospital admission height and weight data during the years 2014-2017. Main Outcome Measure: Functional independence measure (FIM) gain per day of patients by BMI category. Results: The chart review identified 479 patients had undergone hip replacement surgery. Over half of the patients were overweight or obese. FIM efficiency (FIM change/day) was the highest in the obese class II category (3.65), followed by obese class III (3.60). The differences in FIM efficiency between the normal and obese I groups reached statistical significance in favor of obese I (P = 0.024). Conclusion: This study did not demonstrate that obesity significantly impairs functional outcomes during the rehabilitation process after hip replacement surgery.