Metal-on-Metal hip implants received an extensive set of cautionary guidelines for use from the FDA based on an FDA Orthopedic and Rehabilitation Advisory Panel Meeting in June 2012. The source of the problem with Metal-on-Metal (MoM) implants is metal release that causes bone and soft tissue damage, known as “adverse local tissue reaction” (ALTR). When bone and soft tissue damage from metal particles occurs, it leads to pain, implant loosening and the need for revision surgery. However, the metal ions can also enter the bloodstream, travel to other organs and trigger systemic illness such as rash, cardiomyopathy and renal dysfunction. The FDA is unable to define level of metal concentrations in blood or body that produce adverse effects, because different patients have different levels of reactivity to them.
The FDA advises surgeons to carefully weigh the risk benefit analysis for each patient before implanting a MoM hip implant. Alternative implants include metal-on-polyethylene, ceramic-on-polyethylene, ceramic-on-ceramic and ceramic-on-metal. A patient’s age, sex, weight, diagnosis and activity level must all be considered before using a MoM implant. Patients and situations with an increased risk of increased device wear and hence adverse outcomes with MoM implants include:
· Bilateral implants
· Small femoral heads (44mm or less)
· High doses of corticosteroids
· Renal insufficiency
· Suppressed immune systems
· Suboptimal alignment
· Suspected metal sensitivity
· High levels of physical activity
Patients at increased risk of wear need to be followed most closely with symptomatic patients followed every 6 months. The FDA has not recommended that any specific metal-ion level be used to determine whether to undergo revision surgery or other intervention. Such decisions should be made clinically. Unfortunately, replacing a MoM hip implant may have a worse prognosis than replacing one of the other types. Britcher Leone & Roth believes that the physician and the implant manufacturer may be responsible for injury after hip replacement, if the procedure was done incorrectly or if an unsafe device was used.