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An experimental study of lumbar destabilization. Restabilization and bone density
G J Bennett1, H A Serhan, P M Sorini
1Department of Neurosurgery, State University of New York at Buffalo, School of Medicine and Biomedical Sciences, USA.
Spine
|July 1, 1997
Summary
Lumbar spine fixation offers partial stability, with interbody bone enhancing it further. Higher vertebral bone density leads to greater immediate stability from pedicle screws.
Area of Science:
- Spinal biomechanics
- Orthopedic surgery
- Bone densitometry
Background:
- Lumbar pedicle screw fixation is widely used for spinal stabilization.
- Screw loosening in osteoporosis is a known construct failure mechanism.
- Previous studies examined bone density's effect on screw pull-out strength, but not combined with interbody fixation.
Purpose of the Study:
- To measure cadaveric vertebral bone densities using computed tomography (CT) scans.
- To correlate bone density with lumbar spine stability during sequential destabilization and restabilization procedures.
Main Methods:
- Computed tomography (CT) scans measured bone densities in 20 human cadaveric lumbar spines.
- L4-L5 motion segments underwent cyclic axial compression-torsional loading.
- Sequential destabilization and restabilization procedures were performed, including laminectomy, facetectomy, discectomy, and pedicle screw-plate fixation with and without interbody bone.
Main Results:
- Axial and rotational displacements increased significantly after destabilizing procedures (facetectomy, discectomy).
- Pedicle screw-plate fixation reduced displacements; interbody bone further enhanced stability.
- Rotational stabilization from instrumentation correlated with vertebral bone density (r=0.804), improved by interbody bone (r=0.939).
Conclusions:
- Lumbar pedicle screw fixation provides partial spinal stability.
- Interbody bone significantly enhances spinal stability.
- Higher vertebral bone density results in greater immediate stability from pedicle screw fixation.