Abstract
Age is often used as a surrogate for activity. However, it has been demonstrated that BMI has a stronger correlation to post-operative activity than age. The fundamental exercise in choosing a bearing is maximizing the benefit-to-risk ratio. The following question should be addressed on a patient by patient basis: what available bearing is most likely to meet the needs of this patient, with an acceptable risk of revision surgery during their lifetime, is accepted in my community, and with a justifiable cost?
The risk of ceramic fracture is very low with Biolox® Delta, and that risk decreases with increasing head size. However, concerns of taper corrosion, not wear and osteolysis, have driven the increase in utilization of ceramic heads. More research is needed into the etiology of taper corrosion, especially surgeon variability in taper assembly.
Crosslinked polyethylene has substantially reduced wear, osteolysis, and revision rates compared to non-crosslinked polyethylene, regardless of the countersurface. In the AOA National Joint Replacement Registry, ceramic/ceramic, metal/XLPE, ceramic/XLPE, and ceramicised metal/XLPE are the most commonly used bearing surfaces. With 12–15 year follow-up, there is no difference in the cumulative percent revision of these four bearings in patients aged <55.
Ceramic heads are variably more expensive. The ability to recoup the increased cost of ceramic heads through a diminished lifetime revision cost is dependent on the price premium for ceramic and the age of the patient. A wholesale switch to ceramic bearings regardless of age or cost differential could result in an economic burden to the health system.
One measure of “standard” is simply “the most frequently used”. In this regard, market data alone makes the determination of “standard” without regard to clinical or economic outcomes. However, longer follow-up, including financial data, is necessary to better assess the relative value (benefit-to- risk ratio) of all the available bearing couples.
