The Food and Drug Administration (FDA) released updated safety information to patients and health care providers about risks associated with metal-on-metal hip replacement systems and metal-on-metal hip resurfacing systems based on the agency’s current assessment of the implant and results from the June 2012 Orthopaedic and Rehabilitation Devices Advisory Panel meeting.
The safety announcement advises health care providers to consider the benefit-risk profile of using metal-on-metal hip implants as opposed to an alternative hip system made with ceramic or plastic parts, to inform patients about the risks associated with the all-metal implants, and be aware of risk factors in the patient that may predispose a device to excess wear and early failure.
The agency also advised surgeons who use or have used the devices in patients to follow reporting procedures about adverse events related to metal-on-metal hip systems including pain, malposition, adverse local tissue reaction, a type of blood poisoning known as metallosis, hypersensitivity or allergy, loosening and dislocation.
Metal-on-metal hip implants involve a metal ball and metal cup that slide against each other during walking or running. During times of movement, metal an be released from the implant where the two parts connect. This movement may cause some tiny metal particles to wear off of the device around the implant, which could cause damage to bone and/or soft tissue surrounding the implant and joint.
Soft tissue damage may cause the patient pain, lead to loosening of the implant, device failure, and the need for revision surgery. Some of the metal ions released may enter the bloodstream and travel to other part of the body, where they may cause symptoms of illnesses elsewhere in the body.
The FDA says it does not yet have enough scientific data to specify the concentration of metal ions in a patient’s body or blood necessary to produce adverse systemic effects. The reaction appears to be specific to individual patients, with different patients having different reactions to the metal wear particles.
The agency said that metal-on-metal implant patients with systemic symptoms are more likely to visit their primary care doctors than their orthopedic surgeon, which makes it important for all health care providers to be aware of metal ion adverse events that may occur in metal-on-metal implant patients. Reactions reported include general hypersensitivity reactions such as skin rashes; cardiomyopathy; neurological changes including sensory changes such as auditory or vision impairments; psychological status change such as depression; renal function impairment; and thyroid dysfunction including neck discomfort, fatigue, weight gain or feeling cold.
Patients who currently have metal-on-metal hip implants are advised to discuss any symptoms they experience with their orthopaedic surgeon at least every one to two years. Patients should also see their surgeon if they develop new or worsening symptoms such as pain, swelling, numbness, noise (popping, grinding, clicking or squeaking coming from the hip), and/or changes in the ability to walk. They should also discuss with their surgeons any changes in general health, including new or worsening symptoms separate from the hip.