Hip Implants More Likely to Fail in Women

Researchers at the Southern California Kaiser Permanente Research Group (San Diego, USA) reviewed the Kaiser Permanente system's registry of total joint replacements performed at 46 hospitals in California, Hawaii, Oregon, Washington, and Colorado by 319 different surgeons between 2001 and 2010. The data included arthroplasty procedure volumes; the patients and the implants they received (cemented, uncemented, or hybrid); and implant bearing surface, such as metal on metal, metal or ceramic on highly crosslinked polyethylene, or ceramic on ceramic. Only patients undergoing unilateral procedures were included in the analysis.

In all, about 58% of the 35,140 procedures were performed in women (mean age 65.7, versus 63.8 for men). The age difference between men and women was statistically significant, and women in the cohort tended to be slightly more likely to be white or Asian and to have osteoarthritis (OA), rheumatoid arthritis (RA), or dysplasia. They were less likely to be diabetic or obese and to have osteonecrosis or post-traumatic arthritis. The main outcome measures were failure of THA, defined as revision procedure for any reason, septic reason, or aseptic reason after the index procedure.

The results showed that failure rates for hip implants were 29% higher for women than men, after controlling for a variety of factors including device type; the risk appeared most prominent for aseptic revision compared with septic failure. Larger femoral head sizes appeared especially problematic for women. For head sizes of 36 mm or more, the failure rate in women was 49% higher. Not surprisingly, women were much less likely to have implant femoral head sizes of 36 mm or more (32.8% versus 55.4% for men).

The researchers also found that much of the increased risk for women seemed concentrated in metal-on-metal implants, with a doubling in risk for women versus men (19.4% versus 9.6%). Overall, however, ceramic or metal on highly cross-linked polyethylene were more popular for female patients. The DePuy resurfacing implant was used in 1.3% of women versus 2.6% of men. The study was published on February 18, 2013, in JAMA Internal Medicine.

“After considering patient-, surgery-, surgeon-, volume-, and implant-specific risk factors, women had a 29% higher risk of implant failure than men after THA,” concluded lead author Maria Inacio, MS, and colleagues. “With no significant increase in risk of septic failure for women, the results mean that factors other than infection are responsible for the higher overall revision rate.”

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Kaiser Permanente Research Group