Abstract
We undertook a retrospective cohort study to determine if body mass index (BMI) is an independent factor in determining patient outcome following total hip replacement (THR). Outcomes were determined using the Oxford Hip Score, a questionnaire designed to evaluate self-reported function and pain levels in people with hip pain. We looked at all THRs carried out on patients with a BMI of ≥30 over a 38 month period (220 operations) and compared these with 220 randomly selected THRs carried out on patients with a BMI of <30 within the same 38 month period. For each case we recorded patient BMI, P score and Oxford scores. We calculated the difference between pre-operative and one-year post-operative Oxford hip scores. We used Kendall's rank correlation to assess any potential correlation between BMI and functional change, and the Mann-Whitney U test to establish if functional change between the groups was statistically significant. Our study indicates that BMI is not an independent factor in determining relative subjective functional change following THR. Although it showed that patients with a BMI of ≥30 have worse function both before and after THR, there was no statistically significant difference between the two groups in terms of functional change. We therefore suggest that patients with a higher BMI be considered candidates for THR as they can expect the same degree of functional improvement. Given the trend for increasing numbers of obese patients in the population these findings could have a significant impact on the future of THR operations.
