Macnab analyzed 68 patients from 842 lumbar spine explorations who had no disc herniation found at surgery despite classic signs of nerve root compression. The study asks: where is the compression actually coming from? All identified lesions resided in the 'hidden zone' — the nerve root segment between surgical exposure and the intervertebral foramen.
For decades, a normal-appearing disc at surgery was treated as a dead end — surgeons would either enucleate an innocent disc in desperation or close without relief. Macnab's paper reframed the problem: the disc is not always the culprit, and limited laminotomy leaves an entire anatomic zone unexplored.
When you expose a disc and find no herniation, assess the nerve root directly. A freely mobile root is reassuring. A root that is taut and cannot be shifted medially tells you compression exists distal to your view. In the hidden zone.
At that point, extend your exposure and systematically work through Macnab's five diagnoses: foraminal fragment, pedicular kinking, facet impingement, segmental stenosis, and far-lateral herniation. Be willing to sacrifice the posterior joint and even the pedicle to free the root, then stabilize with intertransverse fusion if discs above are healthy.
The data on re-exploration are a warning worth internalizing: outcomes drop sharply with each prior surgery. Getting the diagnosis right the first time is not just good surgery. It is the single biggest determinant of outcome.
Macnab analyzed 68 patients from 842 lumbar spine explorations who had no disc herniation found at surgery despite classic signs of nerve root compression. The study asks: where is the compression actually coming from? All identified lesions resided in the 'hidden zone' — the nerve root segment between surgical exposure and the intervertebral foramen.
For decades, a normal-appearing disc at surgery was treated as a dead end — surgeons would either enucleate an innocent disc in desperation or close without relief. Macnab's paper reframed the problem: the disc is not always the culprit, and limited laminotomy leaves an entire anatomic zone unexplored.
When you expose a disc and find no herniation, assess the nerve root directly. A freely mobile root is reassuring. A root that is taut and cannot be shifted medially tells you compression exists distal to your view. In the hidden zone.
At that point, extend your exposure and systematically work through Macnab's five diagnoses: foraminal fragment, pedicular kinking, facet impingement, segmental stenosis, and far-lateral herniation. Be willing to sacrifice the posterior joint and even the pedicle to free the root, then stabilize with intertransverse fusion if discs above are healthy.
The data on re-exploration are a warning worth internalizing: outcomes drop sharply with each prior surgery. Getting the diagnosis right the first time is not just good surgery. It is the single biggest determinant of outcome.