Perspective

Highly cross-linked polyethylene liners showed reduced wear at 10-year follow-up

A significantly lower prevalence of osteolysis and revision was also found in the highly cross-linked polyethylene liner group.

Patients with degenerative hip disease who received a highly cross-linked polyethylene liner during total hip replacement experienced significantly reduced wear and had greater implant survival at 10 postoperative years than patients who received ultra-high molecular weight polyethylene liners, according to study results.

Peter Devane headhsot
Peter A. Devane

Peter A. Devane, MBChB, MSc, FRACS, and his colleagues randomly assigned 122 patients undergoing total hip arthroplasty for degenerative hip disease to receive either a Enduron conventional ultra-high molecular weight polyethylene liner (UHMWPE) (DePuy) or a Marathon highly cross-linked polyethylene liner (XLPE) (DePuy). Researchers collected Oxford Hip Scores and SF-12 Healthy Survey scores in 91 patients who were available for follow-up at 10-years postoperatively. They also used validated software to analyze radiographs for osteolysis and for 2-dimensional, 3-D and volumetric wear.

Results showed a mean wear rate of 0.03 mm per year and of 0.27 mm per year for patients in the highly XLPE liner group and UHMWPE group, respectively. There was a significantly lower prevalence of osteolysis in the highly XLPE liner group at 10-years postoperatively. Despite that finding, Devane said in an interview with Orthopedics Today it was surprising osteolysis could still occur when highly cross-linked polyethylene was used.

“We believe the osteolysis seen with the highly [cross-linked polyethylene liner] XLPE in our study came from premature loosening of a less than optimal cemented femoral stem,” Devane told Orthopedics Today.

Similarly, patients in the highly XLPE group had a significantly lower revision rate, according to results, with 10 of 12 revisions being in the UHMWPE liner group. However, researchers found no significant differences between the groups based on the Oxford Hip Scores or SF-12 mental or physical well-being scores.

The study is limited as it is a single center study with polyethylene liners analyzed from a single manufacturer that were analyzed, and it has the potential for underreporting of osteolysis with anteroposterior and lateral radiographs used instead of CT or MRI, Devane noted.

But he said surgeons can be confident in their use of highly XLPE in THR.

“Surgeons are able to offer total hip replacement with this bearing surface to patients with confidence that their prosthesis will last substantially longer than previous conventional polyethylene, which has been quoted at 15 years,” Devane said. “This allows total hip to be performed in much younger patients than previously thought, with the knowledge it may be their only operation,” he said. – by Casey Tingle

Reference:

Devane PA, et al. J Bone Joint Surg Am. 2017;doi:10.2106/JBJS.16.00878.

For more information:

Peter A. Devane, MBChB, MSc, FRACS, can be reached at Wellington Hospital, Riddiford St., Newtown, Wellington 6021, New Zealand; email: peterdevane@yahoo.co.nz.

Disclosure: Devane reports he received grants from DePuy and has a patent US 8,659,591 B2 issued to Peter Devane.

Patients with degenerative hip disease who received a highly cross-linked polyethylene liner during total hip replacement experienced significantly reduced wear and had greater implant survival at 10 postoperative years than patients who received ultra-high molecular weight polyethylene liners, according to study results.

Peter Devane headhsot
Peter A. Devane

Peter A. Devane, MBChB, MSc, FRACS, and his colleagues randomly assigned 122 patients undergoing total hip arthroplasty for degenerative hip disease to receive either a Enduron conventional ultra-high molecular weight polyethylene liner (UHMWPE) (DePuy) or a Marathon highly cross-linked polyethylene liner (XLPE) (DePuy). Researchers collected Oxford Hip Scores and SF-12 Healthy Survey scores in 91 patients who were available for follow-up at 10-years postoperatively. They also used validated software to analyze radiographs for osteolysis and for 2-dimensional, 3-D and volumetric wear.

Results showed a mean wear rate of 0.03 mm per year and of 0.27 mm per year for patients in the highly XLPE liner group and UHMWPE group, respectively. There was a significantly lower prevalence of osteolysis in the highly XLPE liner group at 10-years postoperatively. Despite that finding, Devane said in an interview with Orthopedics Today it was surprising osteolysis could still occur when highly cross-linked polyethylene was used.

“We believe the osteolysis seen with the highly [cross-linked polyethylene liner] XLPE in our study came from premature loosening of a less than optimal cemented femoral stem,” Devane told Orthopedics Today.

Similarly, patients in the highly XLPE group had a significantly lower revision rate, according to results, with 10 of 12 revisions being in the UHMWPE liner group. However, researchers found no significant differences between the groups based on the Oxford Hip Scores or SF-12 mental or physical well-being scores.

The study is limited as it is a single center study with polyethylene liners analyzed from a single manufacturer that were analyzed, and it has the potential for underreporting of osteolysis with anteroposterior and lateral radiographs used instead of CT or MRI, Devane noted.

But he said surgeons can be confident in their use of highly XLPE in THR.

“Surgeons are able to offer total hip replacement with this bearing surface to patients with confidence that their prosthesis will last substantially longer than previous conventional polyethylene, which has been quoted at 15 years,” Devane said. “This allows total hip to be performed in much younger patients than previously thought, with the knowledge it may be their only operation,” he said. – by Casey Tingle

Reference:

Devane PA, et al. J Bone Joint Surg Am. 2017;doi:10.2106/JBJS.16.00878.

For more information:

Peter A. Devane, MBChB, MSc, FRACS, can be reached at Wellington Hospital, Riddiford St., Newtown, Wellington 6021, New Zealand; email: peterdevane@yahoo.co.nz.

Disclosure: Devane reports he received grants from DePuy and has a patent US 8,659,591 B2 issued to Peter Devane.

    Perspective
    Per Kjaersgaard-Andersen

    Per Kjaersgaard-Andersen

    Those of us who have been in business long enough know about the dilemma from wear-out of first-generation polyethylene in both THR and total knee replacement. An initial well-functioning THR or TKA slowly becomes painful after 5 years to 10 years, radiographs show significant wear — not rarely full wear-through — and frequently large osteolytic lesions around the joint; lesions that during revision surgery frequently proved to be much more dramatic than could be localized on the radiographs, and demanding to restore. Therefore, we as surgeons are extremely thankful to scientists who took the challenge to investigate how the soft bearings could be improved.

    Polyethylene in the orthopedic field as a bearing has in the 1990s and this decade been through dramatic developments, and today all the manufacturers have a proven, highly XLPE. Several publications have proven highly XLPE to be significantly better than the older, conventional polyethylene. Personally, I would, from these results, question whether it would be ethical still to implant a THR or TKR prosthesis that uses older, conventional polyethylene. The new highly XLPE shows, in more studies, no or insignificant wear using the “gold standard” technique to measure with roentgen stereophotogrammetry analysis. One may even question whether the observations from these studies show true wear or creep. This is due to the fact that since about 2004 to 2005, when most of us started using highly XLPE, we did not see wear of the socket any longer, as osteolytic lesions due to wear were becoming less of a reason for revision. This finding is significant from more of the national joint registries. Also, scientists have shown the few wear particles that appear after loading of highly XLPE are smaller in number, as well as in size. We still need further investigation to learn whether this is the reason for less osteolysis in the adjacent bone, and if, because of that, there is a less frequent incidence of aseptic loosening and revision.

    This study is added proof of the clinical benefit of using new highly XLPE. However, changing the stiffness of the polyethylene may other impacts, like making the material more brittle and increasing the risk of polyethylene fracture if the material used is too thin. These longer-term observations must be our focus in the coming years.

    • Per Kjaersgaard-Andersen, MD
    • Chief Medical Editor, Orthopedics Today Europe

    Disclosures: Kjaersgaard-Andersen reports no relevant financial disclosures.

    Perspective
    Craig J. Della Valle

    Craig J. Della Valle

    A decade ago, it was unclear whether highly XLPE, metal-on-metal or ceramic-on-ceramic was the ideal bearing surface for THA. With time, the “winner” of this battle has become clear given the problems associated with metal-on-metal bearings and, to a lesser extent, with ceramic-on-ceramic bearings. However, there remains some doubt over the longer-term performance of highly XLPE, as we have little data beyond 10 years.

    The randomized study by Devane and colleagues is clear evidence highly XLPE is associated with a lower wear rate, a lower revision rate and a lower risk of osteolysis. The one surprising finding was osteolysis was reported in some of the patients who had the highly crosslinked liners. I am only aware of one other report that described osteolysis in association with highly crosslinked polyethylene, but in combination this suggests that careful continued monitoring of the performance of this bearing surface is warranted. It also suggests that continued monitoring of second and third generation polyethylene is warranted to see if the risk of osteolysis can be eliminated or further reduced.

    • Craig J. Della Valle, MD
    • Orthopedics Today Editorial Board Member

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