Patients with metal-on-metal implants stand no more chance of developing cancer 7 years after hip replacement than the general population, according to findings of a study commissioned by the National Joint Registry of England and Wales and Hospital Episode Statistics.
For their study, investigators from the Universities of Bristol and Exeter analyzed the cancer rates in patients with metal-on-metal (MoM) hip implants and compared them with the cancer rates of patients with other bearing surfaces and the general population, according to a British Medical Journal press release. Using data from the national joint registry, indentified 40,576 patients with MoM bearing surfaces, 21,264 patients stemmed MoM prostheses and 19,312 patients who underwent resurfacings.
The researchers collected data on patient age and gender, and assessed general health at the time of surgery using diagnostic codes recorded at the time of injury, American Society of Anesthesiologists grade and admissions to the hospital in the previous 5 years. The authors noted in their study that comparison with the general population was not straightforward because hip replacement patients “tend to be healthier than others of the same gender and age group.”
According to the release, the investigators discovered a 60-year-old man in moderate health with a MoM stemmed hip replacement would have a 6.2% chance of being diagnosed with cancer 5 years postoperatively compared to a 6.7% chance if other bearing surfaces were used. Women aged 60 years with MoM stemmed hip replacements showed a 4% chance of developing cancer during the same time period compared to a 4.4% chance if they had other bearing surfaces. The investigators also found that cancer rates were lower than predicted for both hip replacement patients and the general population.
The study authors hope clinicians can use the information to inform patients that cancer risks are low for MoM hips. Further studies are ongoing to acquire long-term data, the release noted, as cancer may develop after years or decades.
- Smith AJ, Dieppe P, Porter M, Blom AW. Risk of cancer in first seven years after metal-on-metal hip replacement compared with other bearings and general population: Linkage study between the National Joint Registry of England and Wales and hospital episode statistics. BMJ 2012; 344 doi:10.1136/bmj.e2383. (Published 3 April 2012.)