Few injuries generate as much debate in personal injury litigation as spinal ligament injuries — and few are as frequently misunderstood. A key diagnostic consideration is alteration of motion segment integrity (AOMSI), which can result from ligament compromise and present as measurable instability between adjacent vertebrae. Unlike muscle injuries, which often heal completely, ligament damage may create lasting biomechanical changes.
The American Medical Association’s Guides to the Evaluation of Permanent Impairment (AMA Guides) offer a widely accepted framework for evaluating these injuries. Both the 5th and 6th editions note that spinal motion is not reliably assessed through physical examination and is best evaluated using flexion extension radiographs. The Spinal Regional Grid places documented AOMSI in the same impairment category as intervertebral disk herniations, highlighting its clinical and legal significance.
Motion Segment Integrity and Ligament Compromise
A spinal motion segment is made up of two adjacent vertebrae, the intercalated disk, and facet joints. Stability depends on ligaments such as the anterior longitudinal, posterior longitudinal, and capsular ligaments. When trauma compromises these ligaments, abnormal motion may result.
The AMA Guides describe this loss of integrity as either:
- Abnormal translation: anterior or posterior shift of one vertebra relative to another.
- Abnormal angular motion: excessive tilting compared with adjacent levels.
Such instability can produce pain, neurological irritation, and early degeneration, forming the basis for permanent impairment.
Radiographic Evaluation of AOMSI
The AMA Guides outline thresholds for identifying AOMSI through flexion extension radiographs:
Cervical Spine (6th ed., p. 580):
- Translation: >20% anterior or posterior relative translation.
- Angular motion: >11° greater than adjacent levels.
Lumbar Spine (6th ed., pp. 579–580):
- L1–L5: >8% anterior or >9% posterior translation.
- L5–S1: >6% anterior or >9% posterior translation.
The 5th edition notes:
“Motion of individual spine segments cannot be determined by physical examination but is evaluated with flexion extension roentgenograms.”
This statement can provide attorneys with an evidentiary anchor, emphasizing the role of objective imaging in confirming or ruling out AOMSI.
Equivalence to Disk Herniation
The AMA Guides’ Regional Grid recognizes AOMSI and intervertebral disk herniation as producing comparable impairment levels. This is legally significant because:
- Recognition of Seriousness: AOMSI represents structural injury, not merely a soft-tissue complaint.
- Impairment Ratings: Physicians may assign ratings consistent with disk herniation.
- Objective Support: Radiographic criteria help show that patient complaints are not purely subjective.
Legal Considerations in Personal Injury Cases
Flexion extension studies demonstrating AOMSI can provide objective evidence linking trauma to ligament instability, helping address claims that pain is pre-existing. Because ligaments generally do not return to pre-injury strength, AOMSI supports a finding of permanency — a critical factor in determining damages.
Since the AMA Guides equate AOMSI with disk herniation, attorneys can argue for comparable impairment ratings and compensation, even without surgery. Flexion extension radiographs are typically regarded as objective evidence, which courts and juries often give greater weight than subjective complaints alone.
Conclusion
AOMSI represents a measurable, potentially permanent, and clinically significant spinal injury resulting from ligament compromise. The AMA Guides provide criteria for documenting these findings and place AOMSI in the same impairment category as disk herniation.
For attorneys and physicians, recognizing and documenting AOMSI offers a strong foundation for establishing causation, permanency, and impairment — key factors in achieving fair outcomes for injured individuals.
