title: The effect of obesity on theatre utilisation time during primary hip and knee replacements.
abstract: BACKGROUND
  The aim of this study is to assess the effect of body mass index (BMI) and body weight on theatre utilisation time during primary total hip (THR) and knee replacements (TKR).
  
  
  METHODS
  A total of 1859 cases were included (820 THR and 1039 TKR). Patients were divided into groups based on BMI and body weight. The time interval from 'starting anaesthesia' to 'transfer back to recovery' was used as total theatre time. Hierarchal regression analysis was then used to study the effect of BMI and body weight while controlling the effect of any confounding variables.
  
  
  RESULTS
  In THR cases, the median theatre time was significantly different between BMI and body weight subgroups (p=0.001). In TKR cases, the median theatre time was more significantly different between weight subgroups (p<0.001) than BMI subgroups (p=0.021). Regression analysis showed that only weight remained a significant predictor (p=0.018) of theatre time in THR cases after controlling for other variables. In TKR cases, body weight and BMI were not predictors of theatre time after controlling for other variables.
  
  
  CONCLUSIONS
  Body weight is a significant predictor of theatre time during THR. Neither weight nor BMI predicted theatre time during TKR.
authors: Orthopaedic Surgery, Mersey Deanery, Liverpool, UK.
authors: Seif
authors: S
authors: Sawalha
authors: Orthopaedic Surgery, Mersey Deanery, Liverpool, UK.
authors: Peter
authors: P
authors: Ralte
authors: Orthopaedic Surgery, Mersey Deanery, Liverpool, UK.
authors: Carol
authors: C
authors: Chan
authors: Warrington and Halton Hospitals NHS Trust, UK.
authors: Prakash
authors: P
authors: Chandran
keywords: body mass index; body weight; hip replacement; knee replacement; obesity; theatre time