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Intervertebral mobility in the progressive degenerative process. A radiostereometric analysis
Paul Axelsson1, Bjarki S Karlsson
1Department of Orthopedics, Lund University Hospital, 221 85 Lund, Sweden. paul.axelsson@skane.se.
Summary
Degenerative disc disease shows changing mobility. Stabilization begins when disc height reduces by 50%, but individual differences mean instability can persist even with significant degeneration.
Area of Science:
- Orthopedics
- Biomedical Engineering
- Radiology
Background:
- The three-stage hypothesis of spinal degeneration posits temporary dysfunction, segmental instability with deformity, and osteoligamentary repair-induced stabilization.
- Understanding intervertebral mobility changes is crucial for diagnosing and managing low back pain.
Purpose of the Study:
- To test the three-stage hypothesis of spinal degeneration by assessing intervertebral mobility in relation to disc degeneration.
- To evaluate the relationship between disc height loss and segmental instability in the lumbar spine.
Main Methods:
- Radiostereometric analysis (RSA) was used to measure intervertebral mobility (vertical and sagittal translation) in 18 adult patients with low back pain and degenerative disc findings.
- Lumbar disc segments were categorized into four grades (IA-IV) based on disc height and dehydration.
Main Results:
- Vertical mobility increased slightly and non-significantly with initial disc height loss (grades IB and II).
- A significant reduction in vertical mobility was observed when disc height decreased by at least 50% (grade III).
- Sagittal translation showed non-significant changes across degeneration grades, with a reduction in grade III.
Conclusions:
- Intervertebral mobility changes during disc degeneration, with stabilization commencing around 50% disc height reduction.
- Segmental mobility status is not solely predictable from radiographic disc degeneration stage due to pronounced inter-individual variability.
- Instability may persist even with significant disc height reduction (grade III), and a preceding instability stage with deformity was not confirmed in this study.