Correlations of Lumbar Interspinous Distance with Neuroforaminal Dimensions, Disc Space Height, and Patient Demographic Factors.

Background/objectives: A thorough understanding of spinal anatomy is essential for diagnostic assessment and surgical intervention. Interspinous distance (ISD), neuroforaminal dimensions (NFDs), and disc space height (DSH) have each been studied separately; however, their interrelationship remains unstudied. Given the use of interspinous implants as a minimally invasive treatment for lumbar stenosis and degenerative disc disease, defining these relationships is of growing clinical significance. This study investigates the correlation between ISD and both NFDs and DSH in a normative population and whether ISD varies with demographic factors.

Methods: A retrospective chart review was performed on 852 patients who underwent CT imaging of the lumbar spine. ISD was measured from L1 to L5 as the shortest distance between the most caudal tip of the superior spinous process and the inferior spinous process. DSH was measured at the anterior, middle, and posterior margins. NFDs were assessed in axial and sagittal views, including axial width, craniocaudal height, and foraminal area. Statistical analysis assessed correlations between ISD, NFDs, DSH, and demographic variables.

Results: No strong correlation was observed between ISD and either NFDs or DSH. Slightly greater correlation was present at L1-L3, weakening at L4-L5, where interspinous implants are most commonly placed. Demographic analysis revealed no consistent relationship between ISD and ethnicity, sex, or BMI. While it may be expected that larger ISD correlates with greater NFDs or DSH, our findings do not support this assumption.

Conclusions: ISD does not strongly correlate with NFDs or DSH, and demographic factors do not significantly influence ISD in a healthy population.