No major differences seen at 5 years for highly-crosslinked, conventional polyethylene in TKA

SAN DIEGO — Results of a prospective randomized study of polyethylene used in total knee arthroplasty revealed no differences in survivorship at the 5-year follow-up based on the type of polyethylene used. However, investigators recommended that patients with the brands of highly-crosslinked and conventional polyethylene studied undergo continued follow-up.

Perspective from Craig J. Della Valle, MD

“There was also no significant difference in clinical outcomes and, importantly, no significant difference in complications with the highly-crosslinked polyethylene,” Matthew P. Abdel, MD, said when he presented the level-1 study at the American Academy of Orthopaedic Surgeons Annual Meeting.

Abdel and colleagues studied 515 patients undergoing total knee arthroplasty (TKA) with the all-cemented, posterior-stabilized, fixed-bearing Stryker Triathlon Total Knee System with patellar resurfacing. Overall, 259 patients received X-3 polyethylene — which is highly crosslinked — and 256 patients received conventional N2vac polyethylene.

The 5-year survivorship analysis showed no differences between the groups in terms of being free of any revision or reoperation of any kind, Abdel said.

There were also essentially no significant differences between the groups at middle-term follow-up for clinical outcomes based on the Knee Society Scores and SF-12 physical and mental scores.

“With regard to complications, you can see that there is a similar rate between the X-3 and N2vac group,” Abdel said.
Of important note at this mid-term follow-up study, there were no early failures due to X-3 highly-crosslinked polyethylene fractures, particularly at the tibial post or the patellar pads.” – by Susan M. Rapp

Reference:

Abdel MP, et al. Paper #169. Presented at: American Academy of Orthopaedic Surgeons Annual Meeting; March 14-18, 2017; San Diego.

Disclosure: Abdel reports he is a paid consultant for Stryker, which manufactured the products studied and funded the study.

Perspective

Craig J. Della Valle, MD

The authors are to be congratulated on an important study examining a critical question; the use of highly crosslinked polyethylene in primary total knee arthroplasty (TKA). While the use of this material has become standard in primary total hip arthroplasty, its use in TKA has been more controversial. Specifically, in an era where value reigns supreme, it has been harder to show a clinical advantage to this more expensive bearing material in terms of a lower revision rate or a lower wear rate. Measurement of wear has been a particular challenge around the knee and has been the main metric used to support the use of highly crosslinked polyethylene in the hip.

While this study cannot answer the question of wear, it does suggest that the safety of this bearing is equivalent to standard polyethylene, at least at short to midterm follow-up. This is important as amongst the concerns with the use of highly crosslinked polyethylene in the knee is that the crosslinking process changes the mechanical properties of the bearing which could lead to unintended consequences including increased fragility of the liner itself.

Craig J. Della Valle, MD

ORTHOPEDICS TODAY Editorial Board member

Disclosures: Della Valle reports he receives royalties and research support from Zimmer Biomet, is a consultant for DePuy Synthes, is a consultant for and receives research support from Smith & Nephew., and receives research support from Stryker.