Wear versus thickness and other features of 5-Mrad crosslinked UHMWPE acetabular liners.
BACKGROUND
The low wear rates of crosslinked polyethylenes provide the potential to use larger diameters to resist dislocation. However, this requires the use of thinner liners in the acetabular component, with concern that higher contact stresses will increase wear, offsetting the benefits of the crosslinking.


OBJECTIVE
We asked the following questions: Is the wear of conventional and crosslinked polyethylene liners affected by ball diameter, rigidity of backing, and liner thickness? Are the stresses in the liner affected by thickness?


METHODS
Wear rates were measured in a hip simulator and stresses were calculated using finite element modeling.


RESULTS
Without crosslinking, the wear rate was 4% to 10% greater with a 36-mm diameter than a 28-mm diameter. With crosslinking, wear was 9% lower with a 36-mm diameter without metal backing and 4% greater with metal backing. Reducing the thickness from 6 mm to 3 mm increased the contact stress by 46%, but the wear rate decreased by 19%.


CONCLUSIONS
The reduction in wear with 5 Mrad of crosslinking was not offset by increasing the diameter from 28 mm to 36 mm or by using a liner as thin as 3 mm.


CONCLUSIONS
The results indicate, for a properly positioned 5-Mrad crosslinked acetabular component and within the range of dimensions evaluated, neither wear nor stresses in the polyethylene are limiting factors in the use of larger-diameter, thinner cups to resist dislocation.
Shen
Fu-Wen
FW
The J Vernon Luck Sr, MD, Orthopaedic Research Center, UCLA & Orthopaedic Hospital Department of Orthopaedic Surgery, 2400 S Flower Street, Los Angeles, CA 90007, USA.
Lu
Zhen
Z
McKellop
Harry A
HA
D000077:Acetabulum / Q000601:surgery*; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation* / Q000379:methods; D003432:Cross-Linking Reagents / Q000737:chemistry; D020342:Finite Element Analysis; D006622:Hip Prosthesis; D006801:Humans; D008422:Materials Testing / Q000379:methods*; D011095:Polyethylenes; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013499:Surface Properties
D003432:Cross-Linking Reagents; D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene