Resistant to Third-Body Wear

Foreign particles such as cement, metal or hard bone fragments can become trapped between the articulating surfaces, for example the surfaces of a metal head and a polyethylene insert, and cause abrasion and wear. These foreign particles become embedded in the polyethylene because it is softer and act like sandpaper. This is the so-called “sandpaper effect”, which causes the surface of the metal head to become scratched. This makes the metal surface much rougher and in turn causes further wear of the polyethylene insert. When this type of wear occurs the metal surfaces exhibit many different types of scratches, which are responsible for the abrasion and wear of both polyethylene and metal inserts.

Third-Body Wear on Metal Surfaces

High Resistance of Ceramics to Third-Body Wear

Ceramic surfaces, in contrast, are extremely durable and resistant to third-body wear and can therefore not be scratched. Ceramic is the world’s hardest material next to diamond and is therefore significantly more wear resistant than metal. This is why there is practically no wear in ceramic/ceramic wear couples. Foreign particles that become trapped in a ceramic wear couple are ground together without causing any damage to the ceramic. The synovial fluid washes the residual material away. This is another reason why ceramic implants are considered safer and more reliable than metal implants for wear couple use. More information is available in the brochure BIOLOX®delta Nanocomposite for Arthroplasty

Ceramic Surfaces' Resistance to Third-Body Wear

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    Scientific information and performance data

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No Scratches on Ceramic Surfaces

With cement particles and accidental contact with surgical instruments there is no danger of scratches on ceramic surfaces – an important advantage when using cement and minimally invasive procedures.

Surface of a metal ball head. Scratched surfaces increase abrasion in cup inserts made of PE, XPE and metal.

Only an unscratched smooth surface of the sort achieved in BIOLOX® ceramics enables optimal wetting, outstanding lubrication and minimal wear.

No Third-Body Wear

Unsurpassed hardness prevents third-body wear in ceramic/ceramic wear couples – foreign particles are “ground” without negative impacting the bearing surfaces.

Abrasion Resistance Test in a Hip Joint Simulator

Materials and Methods

Wear volume of Ce/Ce wear couples (primary care)
Source: Endolab Rosenheim

Ball heads: Alumina matrix composite (BIOLOX®delta), CoCrMo
Inserts: Cross-linked UHMWPE 32 mm, UHMWPE 32 mm
Foreign particles: Alumina (Al2O3) particles (BIOLOX®forte)

Ceramic particulate matter up to 5 mm was introduced in the area between the bearing surfaces in order to test abrasion resistance in simulated third-body wear. The abrasion resistance of BIOLOX®delta and CoCrMo ball heads used in conjunction with PE and XPE inserts was tested in a hip joint simulator (Endolab® Rosenheim). Al2O3 particles were introduced in the corresponding inserts prior to the test. Further ceramic particles were added to the wear couples during the test via the test liquid (calf serum). Each wear couple underwent 5 million test cycles. The tests were conducted according to the standards ISO 14242 Part 1 and 2. The damage to the surfaces of the wear couples was assessed visually, and the wear was measured gravimetrically.

Results

Ceramic/PE and Ceramic/XPE

Comparison of wear volume of different wear couples (provision after ceramic fracture)
Source: Endolab Rosenheim

The test results with ceramic particulate matter show that the ceramic/PE and ceramic/XPE wear couples present provision options following the fracture of a ceramic component in order to minimize wear-related problems caused by third-body wear and the related complications. The Ce/XPE wear couple had a ball head wear volume that was 1,000 times lower than an Me/XPE wear couple. A quantification of PE and XPE insert wear was not possible due to the introduction of ceramic particulate matter. Both surfaces maintained their integrity after 5 million cycles, which guarantees the functionality of the wear couple.

Recommended Contacts

Please click on the button “Contacts” to the right, to get a list with the personal and direct responsible contacts within the CeramTec Group.