Study: 2nd-Gen Metal Hip Implants Tied to Adverse ReactionsJan 23, 2014
A recent study reveals that second-generation metal-on-metal hip implants are tied to adverse reactions.
The second-generation study found that most—two-thirds—of the cementless metal-on-metal revision surgeries conducted involved devices that were positioned out of the so-called “safe zone,” according to Helio. The hip devices revealed signs of wear and some patients also reported adverse reaction to metal debris as long as 15 years during the study’s follow-up, the Japanese study indicated.
“The second-generation metal-on-metal (MoM) cementless total hip arthroplasty (THA) encountered adverse reactions to metal debris in two hips,” Keiju Haraguchi, MD, of Osaka General Medical Center, in Osaka, Japan, said, Helio reported. He noted that “The researchers found that “impingement caused by improper cup orientation” was a key factor for the life of “second-generation metal-on-metal total hip arthroplasty with a 28-mm head,” he said.
According to the Journal of Bone and Joint Surgery, impingement occurs due to poor outcomes following prosthetic hip arthroplasty and can cause instability, accelerated wear, and unexplained pain. Evidence of impingement tied to dislocation and accelerated wear has been seen in various studies.
The researchers conducted a retrospective review of outcomes in surgeries conducted with cementless Metasul MoM THA prosthesis in 87 patients between 1997 and 2002. Surgeries were conducted with either the Zimmer APR cup or the Centerpulse Converge cup; 28 mm bearings were used in every case, according to Haraguchi, Helio wrote. The participants were nine men and 42 women who were at an average 60 years of age in the follow-up study.
Patients were followed up for about 12.3 years and the latest follow-up took place at 15 years in some of the patients. According to Helio, 13 surgeons performed the device implants using what is known as a posterolateral approach.
Stem neck notch formation—a sign that impingement has occurred—was seen in 12 patients, and two patients developed reactions to metal debris. Revision was called for in two cases involving loose cups and seven cases of osteolysis. Neck impingement was seen in all cases, wrote Helio. The researchers found that in the Zimmer APR cup, liner dissociation from a poor liner locking mechanism occurred. “There is little benefit for continued use of metal-on-metal bearings in total hip arthroplasty,” Haraguchi said, according to Helio.
All-metal hip device implants were advertised to last for at least 20 years and were believed to have provided increased range of motion over traditional hip replacement devices, which were constructed with plastic or ceramic components. Instead, the all-metal devices have been tied to high and premature failure rates, as well as increased blood metal ion levels and metal poisoning. Injury reports and mounting litigation have also included allegations of dislocation; pain; fracture; difficulty ambulating, rising, standing, and balancing; noise emanating from the joint; and pseudotumors.
Mechanical wear of hip device implants is seen in all types of these devices over time because the femoral head and acetabular cup component surfaces will rotate against each other during typical wear and tear. In metal-on-metal systems, tiny shards of metal may be released during normal wear, which leads to a build-up of cobalt and chromium metal ions within the implant area.