[Comparison of radiological procedures in preoperative assessment of anchorage strength of spinal implants].
OBJECTIVE
To compare three techniques with regards to their ability to estimate pull out strength of spinal fusion hardware.


METHODS
VDS-screw fixation strength in 50 human cadaveric vertebral bodies was approximated by means of pull out force measurement. Bone quality was assessed by Dual X-ray Absorptiometry (DXA). Quantitative Computed Tomography (QCT) and T2*-relaxation time. For each of these techniques, correlation with axial pull out force strength was investigated.


RESULTS
Highest correlation was found for cancellous bone density measured by QCT (r = 0.72; p < 0.001). Immediately followed by DXA (r = 0.70; p < 0.001), which involves all bone components. Inverted T2*-relaxation time (r = 0.55; p < 0.001) and cortical bone density (QCT) correlated just slightly with pull-out force strength.


CONCLUSIONS
Absorptiometrical techniques like QCT and DXA are most appropriate to estimate VDS-screw fixation strength preoperatively.
Schwitalle
M
M
Orthopädische Klinik, Johannes Gutenberg-Universität, Mainz.
Eysel
P
P
Eckardt
A
A
Oberstein
A
A
von Zitzewitz
H V
HV
D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D001863:Bone Screws; D002102:Cadaver; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013123:Spinal Fusion / Q000295:instrumentation*; D014057:Tomography, X-Ray Computed