Morphometric aspects of extraforaminal lumbar nerve roots

Area of Science:

• Neurosurgery
• Anatomy
• Spinal Surgery

Background:

• The lumbar extraforaminal region presents surgical challenges due to unfamiliar neural anatomy.
• Posterolateral and anterolateral approaches require precise knowledge of nerve root pathways.

Purpose of the Study:

• To define normal morphometric parameters of lumbar nerve roots.
• To map nerve root anatomy from the intervertebral foramen to surrounding bony structures.

Main Methods:

• 15 adult fixed cadavers were dissected.
• Measurements of nerve root course and distances to bony landmarks (transverse process, superior articular process, disc space) were taken.
• Angles of exiting nerve roots were measured.

Main Results:

• Distances from the transverse process ranged from 5.1-6.4 mm (superior border) and 6-8.5 mm (inferior border).
• Distances from the superior articular process tip were 19-22 mm.
• Nerve trunk widths varied from 10-25 mm, with exiting root angles of 16-25 degrees.

Conclusions:

• The lumbar nerve complex in the extraforaminal region is located anteriorly, >5 mm from the transverse process and >19 mm from the superior articular process.
• The 'danger zone' extends up to 25 mm anteriorly from the intervertebral foramen in lower lumbar segments.
• Careful surgical technique is crucial within 25 mm of this region, particularly in the lower lumbar spine.