Surgeons debate the future of metal-on-metal, which has good survivorship but scrutiny

Despite criticism in the media of the bearing couple, some surgeons say it is still useful for resurfacing.

Although recent reports focusing on the potential risks of metal-on-metal hip replacement have caused some orthopedists to foresee the end of their widespread use, others hold that the bearing will be here to stay given proper patient selection and head size.

In a crossfire debate with Fares S. Haddad, FRCS (Orth), at the Current Concepts in Joint Replacement 2011 Winter Meeting in Orlando, Fla., Keith R. Berend, MD, noted that although researchers have found up to 97% survival with such articulations at nearly 6 years, lay newspapers have reported on the possible problems with these devices.

Science and media

“In North America, we are bombarded with the data of science, but then we are bombarded with the data of the New York Times,” Berend said. “When I say metal-on-metal is going, going, gone, [I mean that] we are doing the research, we are doing the clinical evaluation, we are doing the surgeries and we are taking care of patients, and then we run into something like this, where the New York Times claims that in medicine, new is not always improved.”

Keith R. Berend

In a study using a second generation metal-on-metal total hip arthroplasty (MoM THA) device, Berend and colleagues found 94% survivorship at an average 12-year follow-up. On average, he said, ceramic- or metal-on-polyethylene articulations have a survivorship of 97% to 98%.

However, a New York Times article reported that, “metal hip replacements are on a trajectory to become the biggest, most costly medical implant problem since one particular company recalled a heart device in 2007,” and used terms such as “crippling injuries caused by tiny particles of cobalt and chromium.”

Berend noted, “This is confusing and frightening to our patients, and for this reason, I think we are moving further and further away from a technology that is truly misunderstood. We are examining this in the laboratory of life because we cannot examine it truthfully in the laboratory — that is in our universities and centers.”

The unknown

Officials in the United Kingdom have issued a medical device alert warning orthopedists who use MoM articulations of aseptic lymphocytic vasculitis associated lesions (ALVALs) and to follow patients who have metal ion levels measuring greater than 7 parts per billion or revise those with a soft tissue mass. However, Berend said that MoM devices are “not all created equal,” and the term ALVAL is not fully understood.

“Is it metal ions, is it impingement, is it reaction, is it hypersensitivity or is it allergy?” he asked. “We do not know. For that reason, I think that metal-on-metal is going, going, gone. I think we need to stick to what works. We need to use it over time and make sure we understand what is happening to our patients. We need to opt for fewer variables, fewer issues and potentially a more reliable solution, which may be going back to what we know from John Charnley.”

Subcategories of MoM

However, Haddad argued that MoM is not “going, going, gone” and that surgeons should consider three subtypes of MoM arthroplasty:

• MoM hip resurfacing;
• MoM THA using large diameter heads; and
• MoM THA with 28-mm and 32-mm heads.

Selecting the right implant and head size for the right patient is key, and he noted that many studies report excellent survivorship with 28-mm MoM bearings.

Fares S. Haddad

“Perhaps there is still a role for 28-mm type metal-on-metal arthroplasty,” Haddad said.

However, he noted that the use of larger MoM heads on stems with resurfacing sockets, leads to problems with bony destruction and soft tissue damage caused by corrosion at the taper. These should be avoided at present, he said.

“If you have heads 50 mm and above, hip resurfacing implants do well if you insert them correctly,” Haddad said. “If we pick the males younger than 65 years with an impingement type (etiology) and a big femoral head, they will do much better than females with small heads, the inflammatories or the dysplastics.”

MoM is still indicated for hip resurfacing, Haddad said. Patients who had MoM resurfacing had good performance in functional tasks, endurance, jumping ability, sports and heavy manual work.

Haddad noted, “The 28 mms have stood the test of time and is a bearing that you should at least continue to follow up if not necessarily take up at this stage. The reality is that hip resurfacing with a metal-on-metal articulation may not be for everyone, but it works well for the right patient with a well carried-out operation.” – by Renee Blisard

References:

• Berend KR, Haddad FS. Metal-metal hip arthroplasty: Going, going, gone. Papers #2 and #3. Presented at the Current Concepts in Joint Replacement 2011 Winter Meeting. Dec. 7-10. Orlando, Fla.
• Molli RG, Lombardi AV Jr, Berend KR, et al. Metal-on-metal versus metal-on-improved polyethylene bearings in total hip arthroplasty. J Arthroplasty. 2011;26(6):8-13.

• Keith R. Berend, MD, can be reached at Joint Implant Surgeons, 7277 Smith’s Mill Rd., Suite 200, New Albany, OH 43054; 614-221-6331; email: berendkr@joint-surgeons.com.
• Fares S. Haddad, FRCS (Orth), can be reached at University College Hospital, 250 Euston Rd., London NW1 2BU; 44-20-79356083; email: fares.haddad@ucl.ac.uk.
• Disclosures: Berend receives royalties from and is a consultant for Biomet Orthopedics, receives funds for research from ERMI and has stock options for intellectual property in OrthAlign Inc. Haddad receives research/institutional support from Stryker, Smith & Nephew, Corin and Pfizer, and is a consultant for Corin, Smith & Nephew and Stryker Orthopaedics.