Risk of THA failure may be lower in ceramic vs polyethylene bearings

Although crosslinked polyethylene bearings offer a cost-advantage, the overall outcomes may be better with ceramic-on-ceramic hip bearings.

Ormonde M. Mahoney, MD, and Andrew M. Shimmin, MBBS, FRACS, debated the use of highly crosslinked polyethylene for patients who undergo total hip arthroplasty at the Orthopedics Today Hawaii Annual Meeting.

According to Mahoney, “Crosslinked polyethylene is good for everybody.”

He said the issue with materials for THA prostheses boils down to the cost of the bearing. He said one-third of the price of these implants goes toward logistics, such as for the management of inventory and transportation of the implants.

“When you consider the importance of that economic fact and the difficulties with managing inventories, keeping up with different polyethylenes, and the fact that once you have the equipment to cross-link polyethylene, the cost is nominal. You are talking about less than 3% of the cost of polyethylene,” Mahoney said.

More stable bearings

However, there are no long-term data on crosslinked polyethylene, especially with 36-mm heads, Shimmin said. He emphasized that ceramic bearing wear products have less biological activity and minimal reports of osteolysis with its long-term use.

Furthermore, Shimmin noted ceramic-on-ceramic bearings can be made with larger articulations, which can lead to greater jump height and more stability.

“In the registry data that I presented yesterday, larger ceramic bearings are revised less than smaller diameter ceramic-on-ceramic bearings,” he said.

Fracture, signs of wear

Although still a potential problem, the incidence of in situ fracture of the modern fourth-generation ceramics is incredibly low, Shimmin said.

Squeaking of ceramic bearings has been reported in several publications. One of the causes is edge-loading of the articulation that can occur at near extremes of range of motion. This situation presents a potential high-wear scenario, according to Shimmin. However, he noted, edge-loading scenarios undoubtably occur in all bearings. The advantage of a ceramic bearing is it can tolerate this high-wear scenario better than polyethylene or meal-on-metal bearings, and the consequence of the high wear is less.

Mahoney told Orthopedics Today in an interview after the meeting, “Dr. Shimmin took a bit of license implying that polyethylene wear due to edge-loading in metal-on-plastic is as clinically relevant as that which occurs with hard-on-hard bearings. In fact, hips are not revised due to edge-loading of plastic bearings unless there is catastrophic failure of the material, which is rare. Although revision of ceramic-on-ceramic bearings for edge-loading and ensuing noise is rare, clinically significant squeaking is reported at double-digit rates by several authors,” Mahoney said. – by Casey Tingle

Disclosures: Mahoney reports he receives royalties from Stryker and for contracted research from Arthrex and Stryker. Shimmin reports he receives royalties and consulting fees from Corin and MatOrtho.

Ormonde M. Mahoney, MD, and Andrew M. Shimmin, MBBS, FRACS, debated the use of highly crosslinked polyethylene for patients who undergo total hip arthroplasty at the Orthopedics Today Hawaii Annual Meeting.

According to Mahoney, “Crosslinked polyethylene is good for everybody.”

He said the issue with materials for THA prostheses boils down to the cost of the bearing. He said one-third of the price of these implants goes toward logistics, such as for the management of inventory and transportation of the implants.

“When you consider the importance of that economic fact and the difficulties with managing inventories, keeping up with different polyethylenes, and the fact that once you have the equipment to cross-link polyethylene, the cost is nominal. You are talking about less than 3% of the cost of polyethylene,” Mahoney said.

More stable bearings

However, there are no long-term data on crosslinked polyethylene, especially with 36-mm heads, Shimmin said. He emphasized that ceramic bearing wear products have less biological activity and minimal reports of osteolysis with its long-term use.

Furthermore, Shimmin noted ceramic-on-ceramic bearings can be made with larger articulations, which can lead to greater jump height and more stability.

“In the registry data that I presented yesterday, larger ceramic bearings are revised less than smaller diameter ceramic-on-ceramic bearings,” he said.

Fracture, signs of wear

Although still a potential problem, the incidence of in situ fracture of the modern fourth-generation ceramics is incredibly low, Shimmin said.

Squeaking of ceramic bearings has been reported in several publications. One of the causes is edge-loading of the articulation that can occur at near extremes of range of motion. This situation presents a potential high-wear scenario, according to Shimmin. However, he noted, edge-loading scenarios undoubtably occur in all bearings. The advantage of a ceramic bearing is it can tolerate this high-wear scenario better than polyethylene or meal-on-metal bearings, and the consequence of the high wear is less.

Mahoney told Orthopedics Today in an interview after the meeting, “Dr. Shimmin took a bit of license implying that polyethylene wear due to edge-loading in metal-on-plastic is as clinically relevant as that which occurs with hard-on-hard bearings. In fact, hips are not revised due to edge-loading of plastic bearings unless there is catastrophic failure of the material, which is rare. Although revision of ceramic-on-ceramic bearings for edge-loading and ensuing noise is rare, clinically significant squeaking is reported at double-digit rates by several authors,” Mahoney said. – by Casey Tingle

Disclosures: Mahoney reports he receives royalties from Stryker and for contracted research from Arthrex and Stryker. Shimmin reports he receives royalties and consulting fees from Corin and MatOrtho.