Ligamentum Flavum

1. Overview

The ligamentum flavum (Latin for “yellow ligament”) is a series of paired elastic ligaments that connect the laminae of adjacent vertebrae from the cervical to the sacral region. These ligaments are part of the posterior wall of the vertebral canal and contribute significantly to spinal stability and posture. Their elasticity allows for smooth motion during spinal flexion and extension while maintaining tension on the vertebral column.

2. Location

The ligamentum flavum is located on the posterior aspect of the vertebral canal:

• Extends from: The axis (C2) to the sacrum, segmentally connecting the laminae of adjacent vertebrae.

• Position: Lies just anterior to the laminae and posterior to the spinal cord and dura mater.

• Part of: The inner wall of the vertebral arch, forming a continuous part of the posterior boundary of the spinal canal.

3. Structure

The ligamentum flavum is a paired elastic ligament with the following features:

• Composition: Rich in elastin fibers (up to 80%), giving it a yellowish appearance and high elasticity.

• Arrangement: Each ligament extends between the anterior surface of the upper vertebra's lamina to the posterior surface of the lamina below.

• Thickness: Thickest in the lumbar region (~3–5 mm), where mechanical demand is greatest; thinnest in the cervical region.

• Paired nature: Each side is separated by the midline and attaches to the right or left side of the lamina.

4. Function

The ligamentum flavum serves several important mechanical functions:

• Maintains spinal posture: Helps maintain an upright posture by providing continuous tension on the vertebral column.

• Assists recoil during movement: Its elastic nature helps the spine return to a neutral position after flexion.

• Protects neural structures: Prevents buckling into the spinal canal during extension, protecting the spinal cord and nerve roots.

• Supports laminar alignment: Helps maintain close approximation between adjacent vertebral laminae.

5. Physiological role(s)

In addition to structural support, the ligamentum flavum contributes to several physiological processes:

• Energy conservation: Stores elastic energy during flexion and releases it during extension, reducing the workload on back muscles.

• Stabilization: Helps stabilize spinal segments during minor movements and prevents excessive flexion or rotation.

• Limits abrupt motion: Acts as a buffer to protect the intervertebral discs and facet joints from sudden jolts.

6. Clinical Significance

The ligamentum flavum is implicated in several spinal pathologies and surgical concerns:

• Ligamentum flavum hypertrophy:

  • Thickening of the ligament, especially in the lumbar region, can narrow the spinal canal (spinal stenosis), compressing the spinal cord or nerve roots.

• Spinal stenosis:

  • Hypertrophied or ossified ligamentum flavum contributes significantly to central canal stenosis, leading to symptoms such as back pain, neurogenic claudication, and sciatica.

• Ligamentum flavum cysts:

  • Degenerative cysts can form within or adjacent to the ligament, causing mass effect on neural structures.

• Surgical relevance:

  • Often resected during laminectomy or spinal decompression procedures; care must be taken to avoid injury to the dura mater underneath.

• Ossification (OLF):

  • More common in thoracic spine and certain populations (e.g., East Asians), ossified ligamentum flavum can cause myelopathy requiring surgical intervention.