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Wear Particles Impact the Life of Joint Implants

Replacing a painful knee with a new knee joint may not be the end of a patient's problems. Particles from the implant can flake off and end up in the joint lining. The body then sets off an immune response that can cause bone loss and loosening of the implant.

The build-up of particles from wear and tear on the implant is one of the most important factors in how long an implant will last. Researchers must think about this as implant design is changed or improved. A study of knee joint fluid (synovial fluid) from 17 patients with no problems after knee replacement offers some useful information.

Synovial fluid was collected one year after surgery. All of the patients had a joint that was working quite well. Half of the patients had an older kind of implant (posterior stabilized) and half had a newer type (medial pivot). The researchers found that the size and shape of the particles didn't make a difference. It's the total number of particles that can bring on bone changes and implant loosening. And the medial pivot implant had fewer wear particles than the posterior-stabilized model.

Future studies are needed to see what if any effect early particle wear has on how long the implant lasts. The authors think it's important to look at implant wear in new joint designs before they are used in many patients. Early studies like this help compare older implant wear to the newer, updated designs.

References: Yukihide Minoda, MD, et al. Polyethylene Wear Particles in Synovial Fluid after Total Knee Arthroplasty. In Clinical Orthopaedics and Related Research. May 2003. Vol. 410. Pp. 165-172.

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