Northwestern University Feinberg School of Medicine

Northwestern University Prosthetics-Orthotics Center

Sagittal Spinal Alignment Study

Principal Investigator: Tyler Koski, MD**

Project Director: Pranitha Gottipati, PhD**

Co-Investigators: Stefania Fatone, PhD, Rebecca Stine, MS, and Aruna Ganju, MD**

**Department of Neurosurgery, Northwestern University

Funded by: Medtronic Sofamor-Danek, Inc.

Status: In Progress


The outcomes of spinal realignment surgery are assessed primarily on static x-rays of the spine with limited understanding of the effect of spinal alignment on functional activities. The purpose of this project is to compare the C7/S1 sagittal alignment assessed by x-ray (see Figure) with that calculated non-invasively in the motion analysis laboratory in able-bodied adults. If the static sagittal alignment results from both methods are similar, the motion analysis technology can be used to assess sagittal alignment during walking. We will also assess the assumption that the C7/S1 plumb line approximates the location of the body center of mass (BCOM) in the sagittal plane.


C7 and S1 vertebral positions and the BCOM position are calculated using the data collected from reflective markers placed on subjects' limbs, back and head. Then we address our hypotheses by comparing able-bodied C7/S1 alignment data, acquired non-invasively in the motion analysis laboratory, with position data acquired via x-ray from another study led by Dr. Koski to establish normative values for x-ray based assessment of C7/S1 alignment.

Preliminary Results

Preliminary results from 14 subjects suggest that the difference between the average radiograph sagittal alignment results and the non-invasive method is less than 1cm. These preliminary results support our hypothesis that the two methods are comparable. The anterior-posterior distance between C7 and S1 vertebrae during walking appears to be considerably larger than static values. The mean absolute distance between the C7 plumb line and BCOM while standing and walking is 2.0 cm and 1.8 cm, respectively.


Bernhardt M. Normal spinal anatomy: Normal sagittal plane alignment. In: The textbook of spinal surgery (2nd edition) (Eds. Bridwell K H and DeWald R L). Lippincott-Raven, Philadelphia 1997: 185-91.

C7/S1 plumb line to measure sagittal alignment (Bernhardt, 1997)C7/S1 plumb line to measure sagittal alignment (Berndardt, 1997).