DOES BODY MASS INDEX AFFECT THE OUTCOME OF PRIMARY CEMENTED TOTAL HIP REPLACEMENT?

Abstract

Introduction: There is little evidence describing the influence of Body Mass Index (BMI) on the outcome of Total Hip Replacement (THR). There are concerns that an increasing BMI may increase complication rates such as superficial and deep infection, blood loss, operation time and aseptic loosening. There is evidence that obese patients receive good symptomatic relief from THR and so it is important that the advisability of surgery is made on good evidence.

Methods: 800 patients undergoing primary Charnley total hip replacement were followed prospectively for a minimum of 18 months. The Harris Hip Score (HHS) and SF-36 were recorded pre-operatively and at 6 and 18 months post-operatively. Other significant events were noted, namely death, dislocation, re-operation, superficial and deep infection and blood loss. Stepwise multiple regression analysis was performed to identify whether BMI was an independently significant predictor of the outcome of THR.

Results: The mean age of patients was 68 years, with 61% females. At 18 months 31 patients (39 hips) had died. There were 15 re-operations, 13 dislocations and 7 deep infections.

No relationship was seen between the BMI of an individual and the development of post-operative complications. The HHS was seen to increase dramatically postoperatively in all patients (mean 43 points at 18 months). BMI did predict for a lower HHS at 6 and 18 months and a lower physical functioning score on the SF-36.

Discussion: THR produces a significant improvement in symptoms in patients, irrespective of BMI. An increasing BMI does not result in an increase in the early complication rate following THR. There is a reduction in the HHS and physical function component of SF-36 with increasing BMI, although this effect is small. On the basis of this study we do not think that THR should be withheld solely on the grounds of BMI.