Total knee replacements (TKRs) are made of metal and/or plastic parts. Tiny particles called debris can loosen from the implant. As the knee joint rolls, slides, and rotates during motion, the surface of the implant forms pits, cracks, and uneven surfaces.
Over time, the bone around the implant dissolves and the implant loosens. This process is called osteolysis. Implant failure can be the final result.
In this review article, researchers explain three of the major factors known to cause wear debris and osteolysis. These factors are patient activity, implant design, and joint alignment.
There isn’t always much that can be done about patient activity. Active adults with joint replacements often want to remain active. That’s why they had the joint replacement in the first place. Many of these patients do not want to give up or modify their activities.
On the other hand, implant manufacturers are actively searching for ways to improve the implant design to reduce debris wear. For example, methods of sterilizing the implant have changed for the better.
The optimal thickness of the implant has been determined. Stronger materials have been developed. A new process called cross-linking has improved implant resistance to wear. Many other design changes have been made to improve the contact area, load bearing, and shape of the implants.
The surgical procedure is the last factor to consider. Good alignment and proper mechanics are needed to avoid increased forces and uneven load on the joint. Even minor deviations from neutral can result in implant failure.
The authors provide guidelines for management and intervention if osteolysis occurs. No treatment is needed if the patient has no symptoms and the condition is self-limiting (doesn’t get worse). Surgery is advised when the patient has symptoms and the X-ray shows osteolysis is increasing in size quickly.