Influence of loading history on the cervical screw pullout strength value.
The problem of the loosening and pullout of bone screws in cervical spine stabilisation is a significant factor in failed implantations of that spine region. Therefore, studies were undertaken to determine the impact of the loading history of bone screws of the cervical spine, inserted from the anterior approach, on the stability of the screw-bone interface. The research was conducted on vertebrae obtained from cadaver specimens of the cervical spine. Two screws were inserted into each vertebra and then pulled out with a force acting along the screw axis. The mean pullout force for the screws subjected to cyclic preloading was 355.2+/-74.4 N, and for the screws subjected to direct pullout it was 411.0+/-78 N (p<0.05). The research results show a significant impact of bone tissue preloading with a cyclic variable force on the pullout force obtained. For the preloaded bone screws the recorded rupture strength of the implant-vertebral body interface was by 16% lower compared to the screws pulled out without preloading. The values presented also show a strong correlation between the bone density and the pullout force obtained after cyclic loading with the strength normal to the screw axis.
Institute of Machine Design and Operation, Wrocław University of Technology, Poland. celina.pezowicz@pwr.wroc.pl
Celina
C
Pezowicz
Jarosław
J
Filipiak
D000328:Adult; D000368:Aged; D000497:Alloys; D001696:Biomechanical Phenomena; D015519:Bone Density; D001863:Bone Screws; D002102:Cadaver; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D066298:In Vitro Techniques; D008875:Middle Aged; D011475:Prosthesis Failure; D011859:Radiography; D013124:Spinal Injuries / Q000601:surgery*; D013314:Stress, Mechanical; D014025:Titanium; D055815:Young Adult
D000497:Alloys; C031462:titanium alloy (TiAl6V4); D014025:Titanium