| Popis: |
Cementless femoral implants have demonstrated widespread clinical success, particularly in the patient populations for which various cemented techniques have been troublesome [1–4]. Long-term fixation and consequent clinical stability occurs primarily via bony ingrowth into a porous-coated implant surface. The adequacy of this biologic fixation depends in part upon the initial or short-term fixation of the implant with respect to the adjacent bone [5,6]. Short-term fixation refers to the post-operative limitation of relative motion between the porous-coated implant surface and the adjacent bone structure. This relative motion, or micromotion, may be limited by utilizing a porous implant coating in concert with a stem press-fit — both increase the frictional resistance to motion [7]. The holding power of the press-fit over time is dependent upon the viscoelastic nature of cortical bone. Data has long been available in the literature for the viscoelastic behavior of cortical bone in the longitudinal direction [8]; however, a transverse viscoelasticity model is required to evaluate a press-fit since it generates considerable radial and circumferential stress but very little axial stress. Only recently has such a model become available [9]. |
