Anulus fibrosus in bulging intervertebral disks

Area of Science:

• Orthopedics
• Spinal Anatomy
• Biomechanical Engineering

Background:

• The anulus fibrosus is the outer layer of the intervertebral disk.
• Disk bulging is a common spinal condition.
• The integrity of the anulus fibrosus in bulging disks is debated.

Purpose of the Study:

• To investigate the association between radial tears of the anulus fibrosus and intervertebral disk bulging.
• To quantify disk bulging and correlate it with annular tears.

Main Methods:

• 149 lumbar intervertebral disks from 31 cadavers were analyzed.
• Sagittal anatomic sections were used to measure a disk bulging index.
• Indexes were correlated with disk development and presence of annular tears.

Main Results:

• The largest disk-bulging indexes were consistently associated with radial tears of the anulus fibrosus.
• 84% of disks with radial tears exhibited bulging indexes greater than 2.5 mm.
• Normal adult disks typically had bulging indexes below 2.5 mm.

Conclusions:

• Radial tears in the anulus fibrosus are a key factor in intervertebral disk bulging.
• The findings challenge the notion that the anulus fibrosus remains intact during disk bulging.
• This suggests a potential pathway for herniation in bulging disks with annular tears.