Birmingham hip resurfacing offers lowest mortality risk

By Lynda Williams

Men with osteoarthritis who undergo Birmingham hip resurfacing have a lower risk for mortality than patients undergoing cemented or uncemented total hip arthroplasty (THA), UK researchers reveal.

The procedure had a comparable rate of revision due to implant failure to uncemented THA, both of which had significantly higher rates than cemented THA, report Richard Riley (University of Birmingham) and co-workers in the BMJ after examining data for approximately 275,000 patients included in the National Joint Registry.

Compared with men who underwent Birmingham hip resurfacing (n=8352), those undergoing uncemented (n=50,529) and cemented (n=53,409) THA were 1.47 and 1.64 times more likely to die during follow up, after adjusting for age, gender, American Society of Anesthesiologists score, and complexity. The hazard ratios (HRs) for revision were 1.04 and 0.65, respectively.

Multivariate analysis showed that male and female patients who received cemented THA between 2003 and 2011 (n=154,996) had a significantly higher rate of mortality than those who received uncemented THA (n=120,017), with a HR of 1.11 (7.6 vs 3.1%).

However, cemented THA was associated with a significantly lower rate of revision surgery due to prosthesis failure than uncemented THA (1.0 vs 1.6%; HR=0.53). Cemented and uncemented THA patients were followed up for a median of 3.6 and 2.6 years, respectively.

The researchers observe that the absolute risk difference in mortality and revision rates between the surgery types was "small."

However, noting the recent focus on the potential toxic effects of metal ions associated with metal-on-metal resurfacing, the researchers say it is "ironic" that that procedure has the lowest mortality risk of the studied osteoarthritis procedures. They believe that their findings should "reassure patients with metal-on-metal resurfacing that this procedure is at least as safe and at best safer than the total hip replacement in terms of overall mortality."

Riley et al add: "More work is necessary to determine whether the higher mortality rate after cemented total hip replacement is caused by the cementing procedure or if this is because of other as yet unknown confounding factors such as differences in activity level between the groups."

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