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Cortical bone trajectory fixation cause low compression force in anterior vertebral column
Sho Fujiwara1,2, Yuichiro Ohnishi1,2, Koichi Iwatsuki2
1Department of Neurosurgery, Osaka University Graduate School of Medicine, Osaka, Japan.
North American Spine Society Journal
|April 18, 2022
Summary
Cortical bone trajectory (CBT) screws provide high insertional torque but lower anterior column compression. This may lead to cage micromotion and reduced bone fusion rates compared to conventional methods.
Area of Science:
- Spinal surgery
- Orthopedic biomechanics
- Spinal fusion techniques
Background:
- Cortical bone trajectory (CBT) screws follow a unique path, differing from conventional pedicle screws.
- The comparative compressive forces and fusion rates of CBT screws remain under investigation.
- This study aimed to evaluate CBT screw insertional torque and compression loading.
Purpose of the Study:
- To assess the insertional torque of CBT screws intraoperatively.
- To compare compression loading and pressure distribution between CBT and conventional pedicle screw fixation.
- To investigate the relationship between insertional torque and bone fusion rates.
Main Methods:
- Insertional torque was measured for 115 CBT screws, with positions confirmed by CT scans.
- Screw loosening and interbody fusion were assessed one year post-surgery.
- Compression loading and pressure distribution were analyzed in pig bone models using conventional and CBT fixation.
Main Results:
- Insertional torque was influenced by screw length and proximity to the endplate and pedicle.
- No significant correlation was found between insertional torque and 12-month bone fusion rates.
- CBT fixation resulted in significantly lower average pressure and compression loading in the anterior column.
Conclusions:
- High insertional torque of CBT screws does not guarantee adequate anterior column compression.
- Reduced compression may compromise intervertebral cage stability, potentially leading to micromotion.
- CBT fixation may negatively impact bone fusion rates due to insufficient compression.
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