Where does the ligament flavum attach?

Attachments of the Ligamentum Flavum

The ligamentum flavum attaches superiorly to the ventral surface of the superior lamina and inferiorly to both the superior edge and anterosuperior surface of the inferior lamina, with the inferior attachment being particularly important clinically during spinal procedures. 1

Anatomical Attachments

Superior Attachment

• Attaches to the ventral (anterior) surface of the superior lamina, extending approximately 6.8 mm along this surface 1
• This attachment is primarily to the deep surface of the lamina above

Inferior Attachment

• Has a dual attachment pattern to the inferior lamina:
  • Superficial component: Attaches to the superior edge and posterosuperior surface of the inferior lamina
  • Deep component: Attaches to the anterosuperior surface of the inferior lamina for a variable distance (averaging 2.2 mm) 1
  • This deep component forms an inferoventral slip that remains between the surgeon and the dura during surgical approaches 1

Regional Variations

Lumbar Region

• The ligamentum flavum becomes more prominent at each successive caudal level of the lumbar spine 2
• At lower lumbar levels, it lines more of the laminae and encroaches further into the posteroinferior region of the intervertebral foramen 2
• The lumbar ligamentum flavum can be divided into three parts 3:
  1. Pars interspinalis: Differs from the interspinous ligament and contains venous anastomoses
  2. Pars interlaminaris: The main target area for surgical flavotomy
  3. Pars capsularis: Merges with the facet joint capsules

Fiber Orientation

• Shows a characteristic change in fiber direction from dorsal to ventral aspects 3:
  • Dorsal fibers: Oriented cranio-medially to caudo-laterally (15-30° angle to midline)
  • Ventral fibers: Aligned strictly in a cranio-caudal direction
  • These fibers are tightly interwoven without any natural spaces between them

Clinical Significance

Surgical Considerations

• The insertion of the ligamentum flavum at the superior aspect of the caudal lamina represents the most constrained area of the spinal canal 4
• During lumbar laminectomy procedures, inadvertent durotomies (CSF leaks) can occur when resecting the ligamentum flavum at its caudal insertion 4
• En bloc resection with a laminotomy beyond the caudal insertion point has been shown to decrease the risk of CSF leaks compared to piecemeal resection 4

Pathological Considerations

• Ossification of the ligamentum flavum can lead to spinal stenosis and neurological symptoms 5
• In central cord syndrome, sudden compression of the spinal cord can occur between a hypertrophic spondylotic disc-osteophyte complex and the buckled ligamentum flavum 5

Recent Anatomical Controversy

Recent research has challenged the traditional view that the ligamentum flavum has two distinct layers:

• Some studies suggest the ligamentum flavum is actually a single structure that is confluent with the interspinous ligament 6
• These researchers propose describing it as having interlaminar and interspinous parts rather than two separate layers 6

Understanding these attachments is crucial for spine surgeons to safely perform decompressive procedures and avoid complications such as dural tears, especially when working in the constrained space at the caudal insertion point.