Bearings in Total Hip Replacement

The bearing that has been used very successfully for decades in total hip replacement is a polished metal ball and a socket made of polyethylene (a type of plastic). One of the main factors that affects the longevity of total hip replacement is wear of the bearing surface between the ball and the socket. This wear creates small particles that create an inflammatory response. This can lead to resorption of the bone around the implants. In a small number of patients this can eventually require further surgery.

This problem has led to the development of alternative bearing surfaces. The main alternatives currently in use are improved cross-linked polyethylene, ceramics and metal bearings. These bearings have been tested in laboratories, but the long term results in patients are not yet known.

Cross-linked polyethylene bearings have a higher wear resistance than the original polyethylene, and it is well know that polyethylene is non-toxic to patients. This is the standard bearing surface that is suitable for most patients.

Metal bearings have even higher wear resistance, but lead to increased metal ion levels in the blood and internal organs. More long-term research needs to be done to determine the long-term effects of this in patients. There is a possibility that these meal ions may lead to allergic reactions, an increased risk of certain types of cancer, or affect unborn babies in women of child-bearing age.

Ceramic bearings are very hard and have the highest wear resistance. They are also known to be non-toxic. Because ceramics are brittle there is a small risk of chipping or fracture of the bearing. This is a painful problem that requires further surgery.

The bearing surface is tailored to each individual patient. Your surgeon will be happy to discuss the different options with you before your surgery.