Wheeless' Textbook of Orthopaedics

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- See:
      - Cross Table Lateral
      - Spondylosis

- Discussion:
    - risk of spinal cord injury with damage to cervical vertebrae is greater in individuals who have narrow spinal-canal diameters;
    - narrow mid-sagittal spinal-canal diameter increases risk of severe neurological injury from spinal frx or dislocation compared w/ pts
           w/ large mid-sagittal canal diameter;
    - in the study by Blackley JR, et al (1999), the authors studied the reliability of using radiographs to determine the true
           diameter of the cervical canal;
           - they noted a poor correlation between the true diameter of the canal and the ratio of its saggital diameter to that of the vertebral body;
           - the authors felt that other types of ratios were equally ineffective in predicting true saggital canal diameter;
    - Torg ratio:
           - diameter of cervical canal : to width of cervical body;
           - less than 0.80 as seen on the lateral view, cervical stenosis is present;
    - Pavlov's ratio (canal-vertebral body width):
           - should be 1.0, with < 0.85 indicating stensosis;
           - ratio of < 0.80 is a significant risk factor for lateral neurologic injury;
           - this identifies a congenitally narrow canal;
    - absolute (AP canal diameter < 10 mm) or relative (10-13 mm canal diameter) stenosis are risk factors for myeopathy, radiculopathy, or both
           due to relatively minor spondylosis pathology or trauma;
           - normal is about 17 mm;
    - minor trauma such as hyperextension may lead to central cord syndrome, even without an overt injury;
    - hyperextension:
           - cord increases in diameter;
           - anteriorly: roots are pinched between discs & adjacent spondylitic bars;
           - posteriorly: hypertrophic facets & infolded ligamentum flavum posteriorly;
    - hyperflexion:
           - neural structures are tethered anteriorly across discs or spondylitic bars;
    - vetebral collapse:
           - collapse of lordotic cervical discs results in loss of normal lordosis of the cervical spine and chronic anterior cord compression;
    - soft disc herniation w/ radiculopathy;
           - usually posterolateral, between the posterior edge of uncinate process and the lateral edge of posterior longitudinal ligament;
    - ossificaition of posterior longitudinal ligament:
            - causes cervical stenosis & myelopathy;
            - common in Asians

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Cervical spinal stenosis: determination with vertebral body ratio method.

Cervical spinal stenosis with cord neurapraxia and transient quadriplegia.

Determining the sagittal dimensions of the canal of the cervical spine. The reliability of ratios of anatomical measurements.