The Journal of Bone and Joint Surgery, Vol 75, Issue 1 19-26, Copyright © 1993 by Journal of Bone and Joint Surgery, Inc
Failure of the porous-coated anatomic prosthesis in total knee arthroplasty due to severe polyethylene wear
A Tsao, L Mintz, CR McRae, SD Stulberg and T Wright
Department of Orthopaedic Surgery, Northwestern University, Chicago, Illinois 60611.
Four hundred and eighty-seven total knee arthroplasties were performed by a
single surgeon with use of a porous-coated anatomic prosthesis between 1982
and 1989. There were thirty-two clinical failures (7 per cent) due to
severe wear of the surfaces of the tibial and patellar polyethylene
components. Thirty patients had a revision. The average time to failure of
the implant was four and one-half years. The initial clinical symptoms of
failure by wear consisted of a painless effusion with a decreased range of
motion. Subsequent pain was considered as the criterion for failure
necessitating operative intervention. Increased weight and decreased age of
the patient and a thinner tibial component were significant predictors of
an increased risk of failure (p < 0.01). Examination of retrieved tibial
components revealed extensive delamination caused by fracture of the
polyethylene at a depth of about one millimeter below the surface. Cracks
that had propagated in from the medial and lateral peripheries of the
tibial component toward the center of the condyles were also a common
finding. It appears that the design of the implant as well as clinical
factors (the age and weight of the patient) contributed to the mechanical
failure of the polyethylene of these implants.
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