Cancer No Threat to Metal Hips (Biloine Young @ OTW)
Patients who received metal-on-metal hip replacements are at no more risk of developing cancer in the seven years following their surgery than are people in the general population. This is according to a study led by the University of Bristol and commissioned by the National Joint Registry of England and Wales, published April 4 in BMJ.
Ashley Blom, Professor of Orthopaedic Surgery in the School of Clinical Sciences at the University of Bristol, who led the team that undertook the study, said “Although this is very reassuring, we do not know what the long-term risks are and thus further studies will be necessary in the future.”
The registry used by the study contains records of over one million procedures from at least 97% of orthopedic units. Technicians link up the registry data and hospital episode statistics, every year, to check how patients who have had joint replacements are faring.
Researchers compared the cancer rates in patients with metal-on-metal hip replacements with both a group of patients who had other hip bearing surfaces implanted and the general population. They found that 14% (40,576) of registered patients had some type of metal-on-metal bearing surface; 7% (21,264) had a stemmed metal-on-metal prosthesis and 7% (19,312) had a resurfacing procedure.
The researchers compared the patients’ outcomes using mathematical modeling. The models included the age and gender of the patients as well as three measures of general health at the time of the hip surgery. The authors note that comparison with the general population is not straightforward as hip replacement patients “tend to be healthier than others of the same gender and age group”.
The results of the study show that the chance of a 60-year-old man with moderate health and a metal-on-metal stemmed hip replacement being diagnosed with cancer in the five years following surgery is 6.2% , compared to 6.7% chance with a hip replacement using other bearing surfaces. For women, these figures were 4.0% for metal-on-metal stemmed hip replacement and 4.4% for other bearing surfaces. Further results showed that the incidence of cancer diagnosis is low after hip replacement and lower than that predicted for the age and sex matched general population.
The authors hope that their study will help clinicians reassure patients that the “risk of cancer for hip replacement patients is relatively low” with no evidence of an increase in cancer associated with metal-on-metal hips at least within the first seven years.