Normal Cervical Interspinous Distance Size on Radiography, CT, MRI
The cervical interspinous distance refers to the space measured between adjacent spinous processes on anteroposterior imaging of the cervical spine. This measurement serves as an indirect indicator of posterior ligamentous complex integrity, including the interspinous and supraspinous ligaments. Abnormal widening is a critical radiologic sign, particularly in the context of trauma and suspected unstable cervical spine injury.
Normal Reference Values
| Orientation | Measurement |
|---|---|
| Anteroposterior | <1.5 x mean interspinous distance |
Clinical Significance
A cervical interspinous distance exceeding 1.5 times the mean interspinous distance of adjacent levels is considered abnormal and should raise suspicion for disruption of the posterior ligamentous complex. This threshold is especially important when evaluating trauma patients, as isolated ligamentous injuries may not be apparent on initial assessment without careful measurement.
Widening of the interspinous distance can indicate flexion-distraction injuries, hyperflexion sprains, or unstable fracture-dislocations. Failure to identify this finding may lead to delayed treatment of an unstable cervical spine, with risk of neurological compromise. It is important to note that patient positioning and voluntary or involuntary muscle guarding can influence measurements; comparison with adjacent levels provides the most reliable assessment.
- Hyperflexion sprain with posterior ligamentous disruption
- Flexion-distraction (Chance-type equivalent) injury
- Facet joint dislocation or perched facets
- Jumped facets with or without associated fracture
- Physiologic pseudowidening in children due to ligamentous laxity
Reference: Benson M, Fixsen J. Children’s Orthopaedics and Fractures. Springer Verlag. p. 822 (2010).
Imaging Notes
On anteroposterior radiography, the interspinous distance is measured between the tips of adjacent spinous processes. The measurement should be compared across multiple levels; a single level appearing wider than 1.5 times the mean of adjacent levels is the accepted threshold for abnormality. Optimal technique requires a true AP projection to avoid rotational artifact that may artificially widen or narrow the apparent distance.
On CT, multiplanar reconstructions allow precise measurement and simultaneous assessment of osseous injury. MRI is the modality of choice for directly visualizing ligamentous disruption, edema, or hemorrhage within the interspinous ligament complex, providing complementary functional and structural detail beyond what measurements alone can offer.