Why a transition zone?
The channel built in this group is noticeably longer than in distal cases. As the channel gets longer, the area that needs monitoring for both fistula and stricture grows — this is why the protective tissue layer covering the new channel is more critical here than in distal repairs.
- On the other hand, if curvature is minimal and the groove is usable, the channel can be built on the existing plate and the repair completed in a single session.

