SAC Radiographic Measurement for Spinal Stenosis
SAC stands for "Space Available for the Cord" and is calculated by subtracting the sagittal diameter of the spinal cord from the sagittal diameter of the spinal canal.
- The sagittal spinal cord diameter is measure from the posterior wall of the vertebral body (half way down) to the laminar line.
- The sagittal diameter of the spinal cord usually comes from measurement on an MRI.
SAC Measurements of:
- > 18 mm = normal
- 15 to 17 mm = possible abnormality
- < 14 mm = concerning for spinal cord compression
Editors: Anthony J. Busti, MD, PharmD, FNLA, FAHA