The US Food and Drug Administration (FDA) has updated its advice on the use of metal-on-metal (MoM) hip replacement prostheses.
The safety communication, published on January 17, provides guidance for orthopedic surgeons, physicians responsible for ongoing care of patients with MoM hip implants, and patients considering or using a MoM hip prosthesis.
After examining data from published studies, and the findings from the June 2012 Orthopaedic and Rehabilitation Devices Advisory Panel meeting, the FDA found insufficient scientific evidence to determine the concentration of metal ions released from MoM implants that is necessary to cause adverse local tissue reactions (ALTRs) or systemic effects in patients.
Indeed, there seems to be differing reactions to metal wear particles between patients, the report states.
The FDA therefore recommends that orthopedic surgeons determine that their patient's risk-benefit profile supports MoM use over alternative metal, polyethylene, and ceramic devices, and discuss the issues with the patient. This should include assessing the patient's age, gender, weight, diagnosis, and activity level, as well as specific contraindications and risk factors for early device failure.
After implantation, asymptomatic patients should undergo physical examination and radiographs every 1-2 years, with closer monitoring for patients at increased risk for ALTR, such as patients with bilateral implants or small femoral heads, obese patients, patients with suspected metal sensitivity, and those using high doses of corticosteroids.
Physicians should be aware of the signs and symptoms of ALTR and thoroughly examine patients who develop hip pain or swelling, or experience changes in walking ability or hip noise 3 or more months after surgery,
Symptomatic patients should be examined every 6 months, and soft tissue imaging and ion testing should be considered, the FDA recommends.
"At this time, the FDA is not recommending a specific metal ion level as a trigger for revision or other medical intervention," the communication states. "The metal ion concentration values, including increases in metal ion levels over time, should be considered in addition to the overall clinical scenario including symptoms, physical findings, and other diagnostic results when determining further actions."
In addition, general healthcare providers should be aware of the risk for metal ion adverse events in MoM hip replacement patients, such as skin rash, cardiomyopathy, sensory changes, depression, renal function impairment, and thyroid issues.
Similarly patients with MoM hip replacements are asked to report changes to their hip, such as pain or noise, immediately to their surgeon, and make healthcare providers aware of their implant.
Writing on the website, the FDA also announced a proposed order which will require manufacturers of MoM total hip replacement systems to submit a premarket approval application or product development protocol for hip joint MoM semi-constrained prostheses with a cemented or uncemented acetabular component.
This update means that manufacturers will now have to demonstrate the safety and efficacy of their prostheses whereas previously they were required only to show the MoM were comparable to devices already in use.
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