A new study from the Hospital for Special Surgery (HSS) has found that the cause of unexplained pain among metal-on-metal hip implant patients is more likely to be tissue damage than wear of the implant. The research team set out to determine the causes of unexplained pain among patients with metal-on-metal hip implants who came to the hospital for revision surgery. Timothy Wright, Ph.D., Kirby Chair of Orthopedic Biomechanics of HSS, states, “nationwide, failure of metal-on-metal hip devices due to unexplained pain is rising.”
The researchers compared 50 patients, 33 with total hip arthroplasties and 17 with hip resurfacing arthroplasties, who came to HSS for revision surgery due to unexplained pain, to a control group of 48 patients who also came to HSS for a revision surgery but because of malalignment, loosening, infection, or fracture. Of the control group, 23 patients had total hip arthoplasties and 25 had hip resurfacing arthroplasties.
According to the HSS report, the investigators combined results from clinical examinations of the patients, magnetic resonance imaging, wear analysis studies on the removed implants, and pathology studies of tissues removed at surgery. The results revealed that thirty patients with unexplained pain had an ALVAL score of at least 5 on a 10-point scale, and 12% of patients had some buildup of metal deposits in their soft tissue. Researchers found implants in both groups showed similar signs of wear.
Wright explains that as some patients in the study had a significant amount of tissue damage but not a lot of wear, it may suggest that “factors other than wear are contributing to the problem regardless of whether the patients have pain.” He adds that the team has used the information from the study to develop guidelines for surgeons and patients.
Source: Hospital for Special Surgery