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Annular bulge contours from an axial photogrammetric method
Karl H Wenger1, John D Schlegel
1Orthopaedic Bioengineering Research Laboratory, Department of Orthopedics, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
Clinical Biomechanics (Bristol, Avon)
|June 21, 2001
Summary
The lumbar spine's annulus bulges most posterolaterally under compression, a key factor in nerve root impingement. This study quantified the characteristic contour of this annular bulge.
Area of Science:
- Biomechanical Engineering
- Spinal Anatomy
- Orthopedic Research
Background:
- Annular bulge in the lumbar spine is implicated in nerve root impingement.
- Previous research lacks consensus on the most prominent bulging region.
- Existing measurement techniques have limitations in accuracy and scope.
Purpose of the Study:
- To characterize the typical contour of lumbar annular bulge under compression.
- To identify specific regions of the annulus that exhibit the greatest bulge.
- To utilize a non-contacting technique for precise bulge measurement.
Main Methods:
- Lumbar motion segments were subjected to 2500 N of compression.
- Axial photographs were captured pre-load and post-load.
- Photographs were digitized to measure transverse annular bulge at 5-degree intervals.
Main Results:
- The greatest annular bulge occurred posterolaterally (0.93 mm), and the least anteriorly (0.37 mm).
- Average bulge across all regions was 0.67 mm.
- Regional bulge differences were more pronounced in lower lumbar segments.
Conclusions:
- Posterolateral lumbar disc herniation may correlate with significant annular bulge in this region.
- Normal annular bulge is minimal, approximately 1/100th of the disc diameter.
- Findings provide a characteristic contour for lumbar annular bulge under compression.