Have A Joint, Know Your Bearings

One of the most significant advances in modern surgery is in total joint replacement (TJR). Every year, surgeons perform hundreds of thousands of TJR surgeries. Material improvements have contributed significantly to this advancement.

In patients with chronic pains due to joint diseases arthritis, bursitis and osteomyelitis, TJR can decrease pain and improve joint function as well be cost-effective; thus, improve the quality of life for of patients. The three most widely performed procedures worldwide are Hip, knee, and shoulder replacements followed by other smaller joints.

Till recently TJR was performed mainly on patients over 60 years old. Surgeons tried to delay its introduction in patients less than 60 years. The reason being patients over 60 are less physically active, and thus the implants did not wear out 10 to 15 years. However, in younger patients, who are physically more active and often participate in high impact sporting activity, the implants undergo more wear and tear. In these patients, the implants could wear out quickly and would require a revision surgery. Each successive revision may not be as effective as the first operation. Improvements in materials, implant designs, and surgical techniques have mitigated the wear and tear and increase their longevity in younger active patients.

The image shows a femoral ball and an acetabulum liner. The surface where these two components meet is called the articulation surface.

The most wear happens where the acetabulum liner and femoral ball rubs against each other. This interface is known as the bearing or articulation surface. For example, if the femoral ball is made of metal and the acetabulum liner is made of a polymer, it is called metal on polymer articulation or simply metal-on-polymer. Or if the femoral ball is made of the ceramic and acetabulum liner is made of polymer then the articulation is referred as ceramic-on-polymer.