The bearing surfaces in the artificial hip joint that serve as the interface between the ball and socket. The most commonly used materials are metal, ceramic, and polyethylene (a type of plastic). Each material has its advantages and disadvantages. The choice of bearing surface depends on the patient's age, activity level, and overall health.
The main bearing surfaces (moving parts) are the following:
- Ceramic on highly cross-linked polyethelene
- Metal on highly cross-linked polyethelene
- Ceramic on Ceramic
- Metal on Metal Resurfacing
Hip replacement implants have been around for over 50 years and over the past 50 years scientists and the orthopaedic community have developed bearing surfaces that are now much longer lasting and likely not to require revision for wear-related problems in the majority of patients. In other words, most patients needing hip replacement surgery over the age of 60 are unlikely to require revision hip surgery for a bearing failure.
The latest Australian National Joint Registry (2022) results show that after 20 years the following revision rates apply to bearing surfaces:
- Ceramic on highly cross-linked polyethelene: 6.8%
- Metal on highly cross-linked polyethelene: 7.7%
- Ceramic on Ceramic: 9.3%
- Metal on Metal Resurfacing in Males: 7.7%
- Duel-Mobility at 10 years is 5%. There is only 10 year data available. At 10 yrs Ceramic on highly cross-linked polyethelene revision rate was 4%
It appears that the most durable and “safe” bearing for the majority of patients is ceramic on highly cross linked polyethelene. Duel-mobility bearings have a higher revision rate in young patients and this bearing is best used when there is a high risk of instability in a particular patient.
Whilst larger femoral heads and duel-mobility bearings have a theoretical improved range of motion, the reality is that a well-positioned hip replacement will have good flexibility and stability with any head size 32mm and above.