ORLANDO, Fla. — The use of contemporary cross-linked polyethylene bearings has improved the durability of total hip arthroplasty; however, most available data are for 28-mm and 32-mm bearings and longer-term data are needed for larger bearings, according to a presenter here.
“We always have to have perspective. If we talk about the way we were when wear and osteolysis were the limitation of total hip technology, and dislocation was prevalent with the common use of 28-mm diameter heads, we really have come a long way,” Thomas P. Schmalzried, MD, said at the Current Concepts in Joint Replacement Winter Meeting. “There are definite benefits of cross-linked polyethylene, but recognize the limitations of our experiences with cross-linked polyethylene.”
He said the use of cross-linked polyethylene bearings have come a long way since their introduction in 1997. At the time, polyethylene wear and osteolysis were the limiting factors of total hip replacement technology. Wear rates have now been reduced by 90% compared with their predecessors, he said, and osteolysis has been reduced.
Thomas P. Schmalzried
With this improved wearing technology, larger-diameter bearings also have reduced the occurrence of dislocation. However, clinical evidence suggests volumetric wear has increased with larger-diameter cross-linked polyethylene bearings, he said. Modular liner fracture is still more likely with larger-diameter bearings, which is associated with increased cup abduction angle and anteversion.
“Cross-linked polyethylenes have clearly and consistently improved the outcomes of total hip replacement,” Schmalzried said. “Longer-term data are needed with larger-diameter bearings on cross-linked polyethylene.”
Schmalzried said opportunities exist for improvements in component positioning, modularity and material properties. Additionally, the relevant benefits and risks for antioxidant cross-linked polyethylene have yet to be determined.
”Only time will tell for sure,” he said. — by Kristine Houck, MA, ELS
Schmalzried TP. Paper #8. Presented at: Current Concepts in Joint Replacement Winter Meeting. Dec. 10-13, 2014; Orlando, Fla.
Disclosure: Schmalzried has received royalties from DePuy for hip products; however, none are related to polyethylene.