Supine thoracolumbar sagittal spine alignment: comparing computerized tomography and plain radiographs

Surgery

Spine (Phila Pa 1976). 2012 Feb 15;37(4):340-5.

Title:

Supine thoracolumbar sagittal spine alignment: comparing computerized tomography and plain radiographs

Authors

Abdel MP

Bodemer WS

Anderson PA

Study Design.

Imaging supine sagittal alignment study

Objective.

1. To determine differences between plain radiographs and CT scans in supine sagittal alignment

2. To establish supine reference Cobb angles for both

Summary of Background Data.

1. Few studies comparing plain radiographs versus CT scans with regard to sagittal spine alignment

2. None utilization of supine patients

Methods.

1. Fifty sequential blunt trauma individuals with routine clearance of the thoracolumbar spine (plain radiographs and CT scans/supine position)

2. Reviewed independently by 2 spine surgeons

3. Cobb method to determine angles at each spine level from T4 to L5

4. No patient with acute ligamentous or bony pathology

5. Intraclass correlation coefficients (ICCs) to determine intraobserver, interobserver, and method reliability.

***The sagittal angle was recorded by measuring from the superior end plate of the vertebral body above to the inferior end plate of the vertebral body below the vertebrae of interest (Cobb Method). Ex, from a line estimating the superior end plate of L2 comparing with a line estimating the inferior end plate of L4.

Results.

1. Thoracic region: kyphotic with a peak at T6.

2. Lumbar region: fairly linear progression from a near-neutral alignment at L1 to approximately 50° of lordosis at L5.

3. Intraobserver reliability was consistent, with ICCs for

*Observer 1 plain radiographs at 0.653, Observer 2 plain radiographs at 0.891,

*Observer 1 CT scans at 0.677, Observer 2 CT scans at 0.648.

4. Interobserver reliability was very high, with ICCs for

*Plain radiographs at 0.902

*CT scans at 0.895  

5. Method reliability (plain radiographs and CT scans) was excellent as well with ICCs

*Observer 1= 0.808, Observe 2= 0.781

*Mean= 0.817

Conclusion.

1. This study provides a supine reference for sagittal spine alignment using the Cobb method for both CT scans and plain radiographs.

2. It also demonstrates the high degree of reliability between measurements from 2 imaging sources and various observers as shown with the ICC values.

Key Points

1. A definitive supine reference for sagittal spine alignment using the Cobb method has been created utilizing both plain radiographs and CT scans.

2. Such a reference should be the standard when evaluating trauma patients.

3. There is a high degree of reliability between plain radiographs and CT scans with regard to supine sagittal spine alignment.

4. There is also a high degree of reliability between observers with regard to supine sagittal spine alignment.

"This comes from Spine (c) 2012 Lippincott Williams & Wilkins, Inc."