See colby notes deformity section
This osteotomy is what some people call a “SPO”. This is the Dr. Lewis version of it. Obviously the greatest possible version of if it (leaves the IAP intact while removing the SAP (where the flavum attaches) so it actually allows the most correction while stitll leaving full boney contat)
Osteotomies are ambiuously named, and people mislabel and misuse names ie: Ponte, SPO etc
Steps
- Osteotome the lateral edge of the SAP (avoids having too remove the inferior facet)
- Leksell inferior lamina
- Decompress leading edge of target level lamina
- Get lateral to cord ASAP
- Resect SAP
- Trajectory is important here
- Need to avoid unproductively running into pedicle
- Coronal 45 degrees
- Sagittal 20 degrees superiorly
- Leave the IAP intact for bony contact (fusion)
The Spine Book 