Highly Crosslinked Polyethylene in Knees
A Scientific Approach to Alternative Bearing Surfaces
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Watch the Highly Crosslinked Polyethylene Video Presentation Presentation Topics
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Overview
Millions of patients now enjoy the benefits of total joint arthroplasty, which has evolved into a “routine” procedure during more than five decades of clinical development and application. Yet the tangible patient benefits of less pain and greater mobility were offset in some cases by a new disease—periprosthetic osteolysis—associated with small particles of foreign materials, especially polyethylene, within the human body.1
As the etiology and manifestations of osteolysis have been elucidated, so too has been the need for more robust orthopaedic materials and designs. Thus began the search for alternative bearings, articulating couples whose in vivo performance would rival the historical metal-on-conventional polyethylene couple. Key to the quest for improved performance is tribology—the science of the mechanisms of friction, lubrication, and wear of interacting surfaces.
The success of total joint arthroplasty (TJA) is multifactorial and dependent on patient-related factors, surgical technique and, in large measure, on the materials and design of the bearings used to replace the body’s articulating surfaces.
The search for alternative bearings with robust in vivo performance is a quest to prevent wear from being a limiting factor in treating these patients.
Because prosthetic materials are evolving, any discussion of alternative bearings must include consistent definitions and accurate descriptions of the materials in question. Alternative bearings are combinations made from materials developed specifically to reduce wear, for example, highly crosslinked polyethylene, metal-on-metal, or ceramic-on-ceramic couples.
Crosslinking was introduced to improve polyethylene’s wear resistance. Crosslinking can be accomplished by using peroxide chemistry, variable-dose ionizing radiation, or electron-beam irradiation. In general, crosslinking and oxidation are competing reactions—as crosslinking increases, oxidation decreases and vice versa.2
Currently available highly crosslinked polyethylene implants differ with respect to the dose and type of irradiation (gamma or electron beam), heat stabilization (remelting or annealing), machining, final sterilization (gas plasma, ethylene oxide or gamma), and packaging.2 Therefore, the wear characteristics of each polyethylene must be considered separately with regard to in vitro and in vivo results.
Related Articles
Zimmer ® Prolong™ Highly Crosslinked Polyethylene
Durasul® Highly Crosslinked Polyethylene
References
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Harris Wh. The osteolysis phenomena in total hip and total knee
replacement surgery. In: Rieker C, Oberholzer S, Wyss U, Eds. World
Tribology Forum in Arthroplasty. Bern: Hans Huber; 2001:17-23.
- Heisel C, Silva M, Schmalzried T P. Bearings surface options for total hip replacement in young patients. J Bone Joint Surg. 2003;85-a(7):1366-1379.
