Second-generation highly cross-linked X3™ polyethylene wear: a preliminary radiostereometric analysis study.
BACKGROUND
First-generation highly cross-linked polyethylene liners have reduced the incidence of wear particle-induced osteolysis. However, failed acetabular liners have shown evidence of surface cracking, mechanical failure, and oxidative damage. This has led to the development of second-generation highly cross-linked polyethylene, which has improved wear and mechanical properties and resistance to oxidation in vitro. Owing to its recent introduction, there are no publications describing its clinical performance.


OBJECTIVE
We assessed early clinical wear of a second-generation highly cross-linked polyethylene liner and compared its clinical performance with the published results of hip simulator tests and with first-generation highly cross-linked polyethylene annealed liners.


METHODS
Twenty-one patients were enrolled in a prospective cohort study. Clinical outcome and femoral head penetration were measured for 19 patients at 6 months and 1 and 2 years postoperatively.


RESULTS
The median proximal head penetration was 0.009 mm and 0.024 mm at 1 and 2 years, respectively. The median two-dimensional (2-D) head penetration was 0.083 mm and 0.060 mm at 1 and 2 years, respectively. The median proximal wear rate between 1 and 2 years was 0.015 mm/year.


CONCLUSIONS
The wear rate calculated was similar to the in vitro wear rate reported for this material; however, it was less than the detection threshold for this technique. Although longer followup is required for wear to reach a clinically quantifiable level, this low level of wear is encouraging for the future clinical performance of this material.


METHODS
Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
Campbell
David G
DG
Wakefield Orthopaedic Clinic, 270 Wakefield Street, Adelaide, SA, 5000, Australia. hipknee@tpg.com.au
Field
John R
JR
Callary
Stuart A
SA
D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D005260:Female; D005720:Gamma Rays; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D020959:Polyethylene / Q000528:radiation effects; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D016059:Range of Motion, Articular; D020127:Recovery of Function; D013021:South Australia; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D016896:Treatment Outcome
D020959:Polyethylene