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Surgeons report unexpected mechanical failures in discontinued modular cups

Investigators called the durability of the implant poor. Acetabular osteolysis marks cup dissociation.

Issue: Issue 6 2006

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Japanese orthopaedic surgeons have reported about a 17% revision rate at mid-term follow-up for modular layered acetabular components implanted during cementless ceramic-on-ceramic total hip replacements.

Investigators identified the main reasons for the revisions as infection, dislocation, ceramic liner fractures, and one case of component disassociation in conjunction with pelvic osteolysis.

Between May 1999 and July 2000, they performed 35 total hip replacements (THRs) with the implant in 30 consecutive patients at Mie University Medical School, Tsu City, Japan. Of those, six acetabular components needed revising. In 2000, Kyocera Corp. of Kyoto, Japan, manufacturer of the layered ceramic acetabular component, withdrew the product from the market.

Mid-term results

“To our knowledge, our paper is the only one that reported mid-term results of this model,” Masahiro Hasegawa, MD, PhD, told Orthopaedics Today. Hasegawa is assistant professor of orthopaedic surgery at the Mie University Graduate School of Medicine.

Other reports have estimated the fracture rate alone with this component to be 2%. For the study, which was recently published in the Journal of Bone and Joint Surgery, investigators analyzed their patients’ clinical and radiographic results at a mean follow-up of 5.8 years. In most revision cases, the stems were firmly fixed, so investigators only switched the acetabular component to a metal shell with a polyethylene liner.

Although there are risks associated with revising a well-fixed stem, when the ceramic has fractured, “we recommend removal of all components and use of alumina-on-alumina or ceramic-on-polyethylene bearings to avoid third-body damage to metal caused by ceramic particles,” Hasegawa said.

Surgeons following patients with this design should consider acetabular osteolysis as a sign that cup dissociation has occurred, he said.

For more information:

• Hasegawa M, Sudo A, Uchida A. Alumina ceramic-on-ceramic total hip replacement with a layered acetabular component. J Bone Joint Surg (Br). 2006;88-B;7:877-882.
• Dr. Hasegawa has no financial interest in the products discussed in this article, nor is he a paid consultant or employee of any company mentioned.