J Korean Neurosurg Soc.  2018 Mar;61(2):180-185. 10.3340/jkns.2017.0404.004.

Straight-Forward versus Bicortical Fixation Penetrating Endplate in Lumbosacral Fixation-A Biomechanical Study

• Karakasli
• Acar N
• Uzun B

• KMID: 2408018
• DOI: http://doi.org/10.3340/jkns.2017.0404.004

Abstract

OBJECTIVE
Many lumbosacral fixation techniques have been described to offer a more screw-bone purchase. The forward anatomical fixation parallel to the endplate is still the most preferred method. Literature revealed little knowledge regarding the mechanical stability of lumbosacral trans-endplate fixation compared to the traditional trans-pedicular screw fixation method. The aim of this study is to assess the pull-out strength of lumbosacral screws penetrating the end plate and comparing it to the conventional trans-pedicular screw insertion method.
METHODS
Eight lumbar and eight sacral vertebrae, with average age 69.4 years, Left pedicles of the 5th lumbar vertebrae were used for trans-endplate screw fixation, group 1A, right pedicles were used for anatomical trans-pedicular screw fixation, group 1B. In the sacral vertebrae, the right side S1 pedicles were used for trans-endplate fixation, group 2A, left side pedicles were used for anatomical trans-pedicular screw fixation, group 2B. The biomechanical tests were performed using the axial compression testing machine. All tests were applied using 2 mm/min traction speed.
RESULTS
The average pull-out strength values of groups 1A and 1B were 403.78±11.71 N and 306.26±17.55 N, respectively. A statistical significance was detected with p=0.012. The average pull-out strength values of groups 2A and 2B were 388.73±17.03 N and 299.84±17.52 N, respectively. A statistical significance was detected with p=0.012.
CONCLUSION
The trans-endplate lumbosacral fixation method is a trustable fixation method with a stronger screw-bone purchase and offer a good alternative for surgeons specially in patients with osteoporosis.

Keyword

Endplate; Pedicular screw; Biomechanical study

MeSH Terms

Humans
Lumbar Vertebrae
Methods
Osteoporosis
Spine
Surgeons
Traction

Figure

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  Fig. 1 A : Traditional trans-pedicular screw fixation through the body parallel to the end plate. B : Trans-endplate screw fixation penetrating the upper end plate, starting from the level of the inferior border of the transverse process, just 2 mm distal to the pedicle entrance, the trans-endplate lumbar pedicle screw is introduced 30° cranially to penetrate the superolateral anterior aspect of the end plate.

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  Fig. 2 The left pedicles of the 5th lumbar vertebrae were used for transendplate screw fixation penetrating the upper end plate, 2 mm distal to the pedicle entrance the lumbar pedicle screw was introduced 30° cranially to penetrate the superolateral and anterior aspect of the end plate. The right sides of the 5th lumbar vertebrae were used for anatomical transpedicular screw fixation through the body parallel to the end plate.

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  Fig. 3 The right sides of S1 pedicles were used for trans-endplate fixation penetrating S1 upper end plate, just 2 mm distal to the pedicle entrance the screw was directed cranially 30° to penetrate the superolateral and anterior aspect of the upper end plate of S1. The left side pedicles of S1 vertebra were used for anatomical trans-pedicular screw fixation through the body of S1 without penetrating the anterior cortex.

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  Fig. 4 The biomechanical tests were performed using the axial compression testing machine (AG-I 10 kN, Shimadzu Shikenki Engineering Co., Ltd, Shimadzu, Japan). All tests were applied using 2 mm/min traction speed.

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  Fig. 5 A bar graph demonstrating the pull-out strength differences between different fixation techniques in L5 and S1 vertebrae.

Reference

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