The effect of interbody cage positioning on lumbosacral vertebral endplate failure in compression

Labrom, Robert D., Tan, Juay-Seng, Reilly, Christopher W., Tredwell, Stephen J., Fisher, Charles G. and Oxland, Thomas R. (2005) The effect of interbody cage positioning on lumbosacral vertebral endplate failure in compression. Spine, 30 19: E556-E561. doi:10.1097/01.brs.0000181053.38677.c2

Author Labrom, Robert D.
Tan, Juay-Seng
Reilly, Christopher W.
Tredwell, Stephen J.
Fisher, Charles G.
Oxland, Thomas R.
Title The effect of interbody cage positioning on lumbosacral vertebral endplate failure in compression
Journal name Spine   Check publisher's open access policy
ISSN 0362-2436
Publication date 2005-10
Sub-type Article (original research)
DOI 10.1097/01.brs.0000181053.38677.c2
Volume 30
Issue 19
Start page E556
End page E561
Total pages 6
Place of publication Philadelphia, PA, United States
Publisher Lippincott Williams & Wilkins
Language eng
Formatted abstract
Study Design: A biomechanical investigation using a human cadaver, multisegmental lumbosacral spine model.

Objectives: To determine if 2 small, posterolaterally positioned titanium mesh interbody cages would provide superior construct strength and stiffness in compression compared to central cage placement. In addition, determine construct stiffness with interbody cages as opposed to an intact spine and assess the effect of bone mineral density (BMD).

Summary of Background Data:
Previous work has shown that the posterolateral corners of the lumbosacral endplates are stronger than the anterior and central regions. Information to suggest appropriate interbody cage positioning to avoid subsidence into adjacent vertebrae would be valuable for spine surgeons and implant designers.

Methods: A total of 27 functional spinal units from L3 to S1 were dual x-ray absorptiometry scanned for BMD, instrumented with pedicle screw systems, and tested to failure in compression with titanium mesh interbody cages placed in 1 of 3 positions: 2 small posterolateral, 2 small central, or 1 large central. Analysis of covariance was conducted to compare failure load and stiffness across the different cage configurations. Repeated measures analysis of variance was used to analyze stiffness between functional spinal units with intact disc, discectomy, or interbody cages. Failure load was correlated against BMD.

Results: Of the 3 placement patterns, 2 small titanium mesh cages in the posterolateral corners had 20% higher failure loads, although the difference was not significant (P = 0.20). Stiffness in compression for the 3 cage positions was not significantly different (P = 0.82). All intact discs with posterior instrumentation were significantly stiffer than any of the cage patterns (P = 0.0001). BMD of the vertebrae significantly correlated with failure loads (P = 0.007).

Conclusions: The placement of 2 small interbody cages posterolaterally tended to result in higher failure loads than central cage placement, although the results were not statistically significant. It is noteworthy that cage placement in any position resulted in a less stiff construct in compression than with an intact disc.
Keyword Spinal fusion
Compressive strength
Internal fixators
Interbody cages
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Medicine Publications
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