• Spine · Jul 2012

    Comparative Study

    Pullout analysis of a lumbar plate with varying screw orientations: experimental and computational analyses.

    • David Rios, Wyzscx Merfil Patacxil, Daniel Kyle Palmer, Paul A Williams, Wayne K Cheng, and Serkan Inceoğlu.
    • Department of Orthopaedic Surgery, Orthopaedic Biomechanics Laboratory, Loma Linda University, Loma Linda, CA 92354, USA.
    • Spine. 2012 Jul 15; 37 (16): E942-8.

    Study DesignExperimental and finite element analysis of anterior lumbar interbody fixation (ALIF) plate pullout.ObjectiveThe objective of this study was to determine the effect of screw angle and orientation on ALIF plate pullout strength.Summary Of Background DataIt has been thought that angling the screws in an ALIF plate leads to better fixation strength; however, a few studies are published on this question, which produced conflicting results.MethodsUsing custom guides, screws were configured in 9 different orientations to affix ALIF plates to polyurethane foam blocks. Pullout tests were performed at a rate of 1 mm/min. In addition, finite element analyses were performed on a 2-dimensional screw-block model to gain insight into the internal stress during pullout.ResultsThe pullout load was the greatest, with screws positioned 12° outward sagittaly and 6° inward coronally (936 ± 72 N). This orientation was statistically greater than the orientation with the lowest pullout load (812 ± 45 N, P < 0.05); however, no group was statistically different than placing the screws straight in (868 ± 86 N, P > 0.05). Finite elements analysis showed some gain in pullout strength at 12° followed by some loss at greater angles. As the screw insertion angle increased, stress levels elevated within the block even in the regions away from the screw.ConclusionSignificant difference was found between certain screw-angle configurations; however, when compared with simply placing the screws straight in, the difference was never more than 8%. This implies that there is greater freedom in the angle and placement of screws than previously thought. Our results show that there is little change in fixation strength when placing the screw in a different direction.

      Pubmed     Full text   Copy Citation     Plaintext  

      Add institutional full text...

    Notes

     
    Knowledge, pearl, summary or comment to share?
    300 characters remaining
    help        
    You can also include formatting, links, images and footnotes in your notes
    • Simple formatting can be added to notes, such as *italics*, _underline_ or **bold**.
    • Superscript can be denoted by <sup>text</sup> and subscript <sub>text</sub>.
    • Numbered or bulleted lists can be created using either numbered lines 1. 2. 3., hyphens - or asterisks *.
    • Links can be included with: [my link to pubmed](http://pubmed.com)
    • Images can be included with: ![alt text](https://bestmedicaljournal.com/study_graph.jpg "Image Title Text")
    • For footnotes use [^1](This is a footnote.) inline.
    • Or use an inline reference [^1] to refer to a longer footnote elseweher in the document [^1]: This is a long footnote..

    hide…