An artificial hip replacement can be life-changing, especially with so many different implant materials available. Surgeons used glass, ivory and metal implants over the past 100 years while performing total hip arthroplasty procedures. In recent years, companies manufactured most artificial hip implants using some combination of ceramic, polyethylene and metal-on-metal components.
Device Manufacturers Voluntarily Recall Several Different Metal-On-Metal Hip Implants
While each material comes with risks and benefits, patients with metal-on-metal implants report the highest complication and failure rates. Device manufacturer Stryker voluntarily recalled all LFIT V40 and Accolade components in 2016 due to high taper lock failure rates. In other words, metal-on-metal implant corrosion left many THR patients with serious injuries, including dislocation, tissue necrosis, and metal poisoning. In fact, the U.S. Food and Drug Administration now informs consumers about increased health complication risks from using metal-on-metal implants. Due to increased adverse event reports involving metal-on-metal hip implants, the FDA launched a post-market surveillance study in early 2016.
Composite Materials That Comprise Most Total Hip Replacement Systems
Device manufacturers use three different composite materials to create most total hip replacement system components. Here’s a breakdown of each type of replacement and what they entail:
Hip Implant Type: Ceramic-on-Ceramic (COC)
Among all ceramic hip implant types currently in use, COC is the most common material pairing for total hip arthroplasty. Other, similar hip implants in this category combine ceramic with more durable secondary materials, including Ceramic-on-Metal (COM) and Ceramic-on-Polyethylene (COP). Ceramic hips are made from the same material that’s found in most dinner plates and dishes, only much more durable. While ceramic hips have fewer complications and less wear than metal-based implants, approximately 4% of COC patients report audible squeaking.
Hip Implant Type: Polyethylene and Metal-on-Polyethylene (MOP)
MOP implants include a metal convex femoral stem and a concave plastic (polyethylene) liner placed between the ball and socket. The most popular choice among orthopedic surgeons, MOP implants are extremely durable and long-lasting, but still shed some wear particles.
Hip Implant Type: Metal-on-Metal (MOM)
In MOM implants, both hip socket and ball are made from stainless steel, titanium, cobalt, chromium, or combined metal alloys. Traditional metal-on-metal hip implant variants go back as far as 1955, finally winning FDA approval for U.S. patients in 1999. However, several device manufacturers have issued urgent MOM hip implant recalls over the last decade due to safety concerns, including:
- DePuy: ASR™ (both XL Acetabular and Hip Resurfacing Systems) in 2010
- Smith & Nephew: R3 Acetabular System metal liners in 2012, then both Modular SMF and REDAPT™ Hip Systems in 2016
- Stryker: Rejuvenate and ABG II modular-neck hip stems in 2012 and LFIT V40 Femoral Head components in 2016
Among all device manufacturers, Stryker has issued the most artificial hip implant recalls since 2002.
The Main Metal-On-Metal Hip Implant Safety Issue? Wear Particles
Since artificial hips require permanently implanting a foreign object, anyone can have an adverse reaction, regardless of the materials used. However, the potential for wear particles is the single biggest concern among orthopedic surgeons. The hip joint’s inherent design means that an individual’s hip and socket continually grate against each other during any movements. When metal-on-metal hip components rub together, it can release metal debris (e.g., “wear particles”) into the bloodstream and surrounding tissue.
Two metal-on-metal implant studies shed light on potential damage caused by Adverse Reactions to Metal Debris, or ARMD:
- A 2004 study on artificial knee and hip implants analyzed the wear particles issued by metal-and-metal devices removed from patients. After comparing the subjects’ chromosomal health against the amount of metallic wear particles found, the researchers discovered a direct correlation. “Wear debris can damage chromosomes in a dose-dependent manner which is specific to the type of metal,” asserts the study, concluding the “worn implant is at least partly responsible for the chromosomal damage” found in surrounding tissue. This study’s results are understandably alarming, since theoretically, chromosomal abnormalities can also cause individuals to develop cancer.
- Yet another 2015 study examined the association between metal-on-metal hip implants and pseudotumor incidence rates. Essentially, when a solid mass of irritated tissue forms around a patient’s artificial hip joint, it’s called a pseudotumor. While observing 706 THR patients, researchers found that 35% developed pseudotumors within three years. This study confirmed yet another serious health risk that’s highly correlated with using metal-on-metal hip implants.
Who’s Most Likely To Suffer ARMD Complications After Total Hip Arthroplasty?
Some orthopedic surgeons may promote one specific hip implant type as “minimally invasive” over another option. But in reality, no minimally invasive THR procedure or device actually exists. While surgeons use slightly smaller incisions to insert metal-on-metal hip implants, they’re actually much more invasive than non-MOM medical devices. In fact, certain patient populations have much higher adverse reaction risks than others with metal-on-metal implants.
A 2015 randomized trial found that small women were most likely to develop pseudotumors after metal-on-metal total hip arthroplasty (75%). Further, women with MOM hip implants were more than twice as likely to develop psuedotumors than women with MOP implants. Male MOM hip implant subjects saw a 40% increase in psuedotumor incidence rates compared with MOP hip implants. However, women with MOM hip implants and elevated cobalt levels showed the greatest risk for developing pseudotumors within five years.
In general, studies have linked implant systems using larger femoral head sizes with increased adverse reaction risks involving metal-on-metal debris. However, one 2016 study found 5% of patients with smaller MOM hip implants still required revision surgery for ARMD complications. The study concludes, “Patients with all MoM THA devices should be encouraged to return for clinical and radiographic follow up… Symptomatic patients should undergo thorough investigation and vigilant observation for ARMD.”
What Metal-On-Metal Hip Implant Patients Can Do
MOM hip implants can corrode, eventually damaging the surrounding tissue. This damage can cause pain, swelling, pseudotumors, dislocation, corrosion and premature joint failure. These complications often necessitate multiple painful revision surgeries, which can be financially devastating. If you received a Stryker, DePuy or Smith & Nephew metal-on-metal hip implant, you may be eligible for compensation. After recalling several faulty metal-on-metal hip implants, Stryker agreed to pay $1.43 billion to settle thousands of lawsuits in 2014. To see in just minutes if you may qualify for a cash settlement, get your hip implant claim review today.
Mandy Voisin
Mandy Voisin is a freelance writer, blogger, and author of Girls of the Ocean and Star of Deliverance. As an accomplished content marketing consultant, mom of four and doctor's wife, Mandy has written hundreds of articles about dangerous drugs and medical devices, medical issues that impact disabled Americans, veterans' healthcare and workers' compensation issues since 2016.