Stitching Considerations especially for Scoliosis Cases

Why Stitching Can Change Measurements: A Step-by-Step Review

1. Understand why stitched scoliosis values can change 0:01

This tutorial is for advanced users stitching scoliosis sectionals.
The main point: measurement changes after stitching are often expected, not necessarily a software bug.
The changes usually come from how the x-rays were taken, chosen, and aligned.

2. Remember that each sectional is shot from a different central ray angle 0:52

Sectionals are usually taken as multiple x-rays.
Each image has a different central ray angle, so the same vertebra can look slightly different from one film to another.
That changes the perceived end plates and Cobb line placement, which can alter the measured angle.

3. Prefer stitching to a new case when possible 1:40

For scoliosis, it is often easier to stitch into a new case rather than an existing one.
This is especially helpful when the curve extends beyond the edges of the film.
A new case makes it easier to:
- work with the full spine,
- identify the true start/end of the curve,
- compare full-spine studies later,
- avoid confusion from re-editing an existing case.

4. Set patient expectations before stitching 3:19

Tell the patient up front that the x-rays are being stitched together.
Explain that small measurement changes can happen because the goal is to create an overall picture of spinal alignment.
You do not need to explain the physics in detail—just enough so the patient understands why values may shift.

5. Fine-tuning points after stitching is normal 2:59

Post-processing often places the images in the general vicinity.
The doctor may then adjust digitization points or even the scoliosis level after stitching.
That is acceptable, but it reinforces why the clinician must understand how projection affects the result.

6. Choose the correct film for the overlay 4:34

A major source of change is choosing the wrong x-ray as the top image during stitching.
In the example, the lumbar film was placed on top instead of the thoracic film.
Because the overlap and visible anatomy were different, the Cobb angle changed significantly even though the points were not moved much.

7. Understand why Cobb angles are especially sensitive 6:13

Cobb angles are still the standard and must be reported.
But Cobb measurements are highly sensitive to small endpoint changes.
That means even a slight difference in projection or endpoint selection can create a large change in the final angle.

8. Compare Cobb with other methods to see the difference 6:52

In the example, the Risser-Ferguson measurement changed only slightly.
The Cobb angle changed much more dramatically.
This shows that Cobb is more vulnerable to projection and endpoint differences than some other methods.

9. Restitch using the better overlay image 7:18

The fix in the example was to restitch without moving the points, but choose the thoracic film as the top overlay.
Once the correct film was used, the measurements returned to nearly the original values.
This confirms the issue was image selection and projection, not a software error.

10. Know the main reasons stitched values change 8:08

The clinician may move points during post-processing.
The wrong x-ray may be chosen as the overlay.
The central ray differs between sectionals, so the same vertebra is viewed from a different angle.
All of these can cause small or large measurement differences after stitching.

11. Use full-spine AP imaging when available, but know its limits 9:00

A full-spine AP image reduces some projection distortion because it captures the spine in one shot.
But sectionals can still be useful because they reduce distortion in the areas they cover.
The key is understanding that different imaging methods produce different perspectives.

12. Watch for upcoming stitching improvements 10:03

Future updates to the stitching module will make it easier to see ghosted overlays, lines, and digitization points.
That should help users judge alignment more accurately during stitching.
Version 27 and later will also improve how scoliosis is handled in reporting.

13. Use scoliosis digitization more directly in newer versions 10:42

In older versions, users often had to digitize with the 3-point modified Risser-Ferguson method, then restitch and redo as scoliosis.
In newer versions, you can digitize directly as scoliosis.
This saves time and still reports the Cobb angle appropriately without incorrectly labeling every small curve as a scoliosis diagnosis.

14. The same principles apply on lateral views 11:48

Lateral stitching can also produce changes, though usually less than AP views.
That is because the lateral view looks more along the axis of rotation, with cleaner end plates and vertebral bodies.
Still, projection differences can happen, so the same caution applies.

15. Final takeaway 12:22

If stitched scoliosis values change, that does not automatically mean something is wrong.
The likely causes are:
- projection differences,
- image selection,
- point placement,
- and the sensitivity of Cobb measurements.
The clinician should understand this well enough to explain it to the patient and to choose the best stitching workflow going forward.

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