Abstract
Current literature comparing the effect on body mass index (BMI) on the outcome of total hip replacements (THR) is inconclusive. To describe the effect of BMI on THR over the first five years.
We prospectively recruited 1,617 patients undergoing primary THR for osteoarthritis and followed them up at 5 years, recording, dislocations, revisions, deep and superficial infections, Harris Hip scores (HHS) and SF-36. A multivariate analysis was performed to identify if BMI is an independent predictor of adverse outcome.
148 (9%) patients had a BMI >35. 6.8% of patients with a BMI >35 had a dislocation by 5 year post op compared with 3.2%BMI 30–34.9, 2% BMI 25–29.9 and 1.5% BMI<25 (p=0.03) Superficial infections 14.2% BMI >35, 4.4% BMI <25. In SF 36 scores only Mental Health and change in health had no significant differences with an increase in BMI having a statistically significant decrease in all other SF scores. HHS had a mean improvement of 45.1 at five years with an expected loss of 0.302 HHS points (95% CI0.440–0.163) per 1 point BMI increase. There was no significant difference in deep infections, mortality <3 months, revision rates or length of stay.
The most significant risk in increasing BMI is the dislocation rate, possibly representing increased technical difficulty in larger patients. Whilst increasing BMI has a reduced HHS and SF16 score, the overall benefit is still positive.
