A series of 100 consecutive UCI knee replacements showed a 7 per cent
incidence of reoperation due to loosening of the prosthesis associated with
permanent deformation of the tibial component. Analysis of the clinical
data, roentgenograms, and removed implants showed associations between
failure and radiolucency at the cement-bone interface, prosthetic
obliquity, collapse of trabecular bone, change of the alignment of the
extremity, and permanent deformation of the tibial component. Although no
one of these factors by itself can be responsible for the mechanical
failure of the arthroplasty, a predominant failure pattern exists. We think
that the sequence of events is as follows: implantation of the tibial
component with medial or lateral tilt; lack of firm skeletal stabilization;
continual microtrabecular fractures; change in alignment of the extremity;
and permanent deformation of the plastic component.