The measurement of creep in ultrahigh molecular weight polyethylene: a comparison of conventional versus highly cross-linked polyethylene.
Quantification of creep of highly cross-linked polyethylene would enable separation of creep from wear when evaluating femoral head penetration into polyethylene. We compared creep magnitude of a highly cross-linked versus conventional polyethylene in the laboratory. Twelve acetabular liners of each material were tested, 6 of which had a 32-mm inner diameter (ID) and 6 had 28-mm ID. Creep was measured using coordinate measuring machines during loading at 2 Hz without motion to 4 million cycles. Penetration into 32-mm ID conventional liners reached 97 microm versus 107 microm for highly cross-linked material, not significant. Penetration into 28-mm conventional liners was 132 microm versus 155 microm for highly cross-linked material (P = .017). Ninety percent of the creep had occurred by 2.5 million cycles.
Estok
Daniel M
DM
Orthopaedic Biomechanics and Biomaterials Laboratory, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
Bragdon
Charles R
CR
Plank
Gordon R
GR
Huang
Anna
A
Muratoglu
Orhun K
OK
Harris
William H
WH
D019644:Arthroplasty, Replacement, Hip; D001696:Biomechanical Phenomena; D005270:Femur Head; D006622:Hip Prosthesis; D006801:Humans; D008970:Molecular Weight; D020959:Polyethylene
D020959:Polyethylene