[Measuring spatial micro-movement of the femur shaft of endoprostheses in relation to the spatial force system].
A precision measurement method (resolution: 0.1 micron) is described that simultaneously tracks spatial movement of the prosthesis and its bending as a function of the spatial force system (three force and three torque components). With this technique, we examined the effects of complete separation between shaft and cement on bending and micromovement. With regard to mechanical stability a completely tied and a loosened prosthesis differ only in respect to torsional load: the loosened prosthesis bears a 2.5-fold larger torsion flexibility. In both cases the shaft does not move like a rigid body: it bends up or down depending on the way the torque acts. It is the torques (that are produced by the forces) rather than the forces themselves that are responsible for the extent of micromovement and bending. In the completely loosened shaft, the shaft's apex only moves either intrusively or extrusively according to the directions of the torque vector: the horizontal movement cannot be resolved. The data suggest that shafts that are freely mounted into its cement quiver load the cement layer in a less damaging fashion than tied shafts.
Nägerl
H
H
IV. Phys. Inst. der Univ. Göttingen.
Kubein-Meesenburg
D
D
Schäfer
W
W
Cotta
H
H
Thomsen
M
M
Strachwitz
B
B
Fanghänel
J
J
D000328:Adult; D001843:Bone Cements; D005269:Femur / Q000503:physiopathology*; D006622:Hip Prosthesis; D006801:Humans; D008768:Methylmethacrylates; D011183:Postoperative Complications / Q000503:physiopathology*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016474:Weight-Bearing / Q000502:physiology*
D001843:Bone Cements; D008768:Methylmethacrylates
Messung der räumlichen Mikrobewegung des Femurschaftes von Endoprothesen in Abhängigkeit des räumlichen Kraftsystems.