[The influence of bone quality and the fixation procedure on the primary stability of cementless implanted tibial plateaus].
BACKGROUND
An overview of prospective studies on cementless and cemented primary knee joint endoprosthetics carried out between 1988 and 2004 reveals that the aseptic tibial loosening rate of cemented prostheses implanted with fixed meniscal bearings amounts to 2-6% within a period of 4-14 years, while cementless implanted prostheses show loosening rates of up to 28% within a period of 4-10 years. If these results arise from a lack of proper initial osseointegration as a result of insufficient primary stability, and how this is influenced by the tibial bone quality and the tibial fixation procedure has not yet been investigated.


METHODS
Tibial plateaus were press-fit implanted, both screwed and unscrewed, into each of six pairs of tibial heads from corpses. Stability testing was conducted applying eccentric axial load, shear and torsion.


RESULTS
The average amounts of relative movement at the medial and lateral plateau are clearly different in the screwed version and the unscrewed version when loaded axially, but the difference was significant (p = 0.016) only at the medial plateau. Relative movements under shear and torsion showed no significant differences. The bone density of the tibial metaphyses had no significant effect on the primary stability of the cementless implanted tibial plateau.


CONCLUSIONS
When using cementless knee endoprostheses, the fixation of the tibial plateau with screws--in addition to a flawless press-fit and form-fit customization of the tibial head--appears indispensable for guaranteeing proper osseointegration under physiological axial loads.
Boos
Carsten
C
Klinik für Orthopädie, Universitätsklinikum Schleswig-Holstein, Campus Lübeck, Lübeck, Deutschland. carsten.boos@bluewin.ch
Fink
Klaus
K
Stomberg
Peter
P
Koeller
Wolfgang
W
Igl
Bernd-Wolfgang
BW
Russlies
Martin
M
D002484:Cementation; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology* / Q000517:prevention & control*; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery*; D007720:Knee Prosthesis; D009038:Motion; D013977:Tibia / Q000601:surgery*; D016896:Treatment Outcome