Registry data show Smith & Nephew Orthopaedics’ ceramicized metal/crosslinked polyethylene bearings have lowest hip revision rate

Data from the Australian Orthopaedic Association’s National Joint Replacement Registry Annual Report shows that, at 5 years postoperative, hip replacement implants made from ceramicized metal heads which articulate against polyethylene-lined cups have superior survivorship compared to implants made from any other material, according to a Smith & Nephew Orthopaedics press release.

OXINIUM Oxidized Zirconium and crosslinked polyethylene (XLPE), the materials in VERILAST Technology from Smith & Nephew Orthopaedics Division, comprise the overwhelming majority of ceramicized metal hip implants in the global orthopedic market, the company stated. VERILAST Technology is used in both hip and knee replacement implants.

The Australian joint registry tracks virtually all joint replacements implanted in that country, and in the 2010 edition, the group reports on more than 150,000 hip replacements implanted between 1999 and 2009.

The data show that implants using ceramicized metal technology, such as OXINIUM Oxidized Zirconium, in combination with polyethylene, remained successful in 97.9% of patients 5 years after surgery. Implants with bearings made from other materials had to be revised over the same period at higher rates. The survivorship rate for ceramicized metal bearings improved to 98.5% in the larger component sizes, and the performance gap between ceramicized metal bearings and other bearing materials widened, as well, according to the press release.

“OXINIUM material in combination with crosslinked polyethylene is unique among hip replacement technologies,” Joseph M. DeVivo, president of Smith & Nephew Orthopaedics, stated in the release. “We’re thrilled by these results — we’ve worked hard to introduce technologies that improve the wear performance of implants, and this report confirms our decades of research and innovation. Active patients demand implants that can keep pace with their lifestyle, and we have the patent on the most technologically advanced material for this segment.”

Studying the performance of OXINIUM Oxidized Zirconium against other bearing surfaces in a large patient group is now possible because the 2010 edition of the patient registry marks the first time the Australian Orthopaedic Association has tracked “Ceramicized Metal/Polyethylene” as a distinct category of bearing surface materials. OXINIUM material is a metal alloy that undergoes a proprietary heating process, transforming its surface into a hard, smooth ceramic that is 4,900 times more resistant to scratching than the traditionally used metal alloy, cobalt chrome. The underlying alloy retains its original properties, giving the implant the strength of metal, but the improved wear performance of a ceramic. It is 20% lighter than cobalt chrome, and because it doesn’t contain detectable amounts of nickel like cobalt chrome does, it is considered hypoallergenic and safe for patients with metal allergies, Smith & Nephew reported.

The company recently introduced VERILAST Technology, which is the combination of OXINIUM material and a unique crosslinked polyethylene formula. This bearing couple has been shown in laboratory tests to reduce hip implant wear by up to 98% when compared to cobalt chrome and conventional polyethylene, according to the press release.

In April 2010, Smith & Nephew announced the results of an unprecedented laboratory test on the use of VERILAST Technology with its LEGION Primary Knee System, which showed that it is expected to provide performance for 30 years of typical physical activity.

The results of this in-vitro wear simulation testing have not been proven to quantitatively predict clinical wear performance, the company said. Also, a reduction in total polyethylene wear volume alone may not result in an improved clinical outcome as wear particle size and morphology are also critical factors in the evaluation of the potential for wear mediated osteolysis and associated aseptic implant loosening. Particle size and morphology were not evaluated as part of the testing. The same test has not been performed on the use of VERILAST technology in hip replacements.