الفهرس 
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Abstract
Anatomical study of the lumbar ligamentum flavum revealed that it was rectangular in shape, it was attached superiorly to the inferior edge and the anteroinferior surface of the upper lamina while below it was attached to the upper margin and upper part of the external surface of the lower lamina.
Ligamentum flavum has two surfaces, external and internal and two borders, medial and lateral.
The medial borders of the right and left ligaments come into contact where they are united together, leaving a narrow slit for the passage of small blood vessels. The medial border of the ligamentum flavum corresponded to the base of the spinous process and to the corresponding border of the opposite ligamentum flavum. The lateral border extended as far as the intervertebral foramen forming the entire posterior boundary or roof of the foramen.
The internal surface of the ligament was found to limit the vertebral canal and to be separated from the dura mater by the epidural space. The external surface is related above to the inner surface of the adjacent upper lamina, and below to the interspinous ligament medially and to sacrospinalis muscle laterally. The ligamentum flavum had two parts, superficial and deep.
Out of the 15 cadaveric lumbar specimens, 4 specimens (26.%) showed midline gaps. The gaps were not in the whole length of the ligamentum flavum, it measures 10 mm in length and 2 mm in width. This gap was present in the lumbar region between third and fourth (L3-L4) and between fourth and fifth lumber vertebrae (L4-L5). The exposed epidural space was filled with connective tissue and fat.
The length of the ligamentum flavum ranged from 13mm to 20mm with a mean of 16.7±2.4mm. The width and thickness of its lower part ranges from 12mm to 22mm with a mean of 17.6±3.1mm, and 3mm to 5mm with a mean of 3.9±0.7mm respectively.
By MRI of forty patients, the width and thickness of the ligamentum flavum ranged from 13.5mm to 20mm with a mean of 16.7±2.4 mm, and 3.5mm to 6mm with a mean of 4.5±1 mm respectively using soft tissue window.
The distance between the skin and the epidural space at the 3rd to the 4th lumbar vertebrae (depth of epidural space) ranged from 3.2-5.6 cm with a mean value of 4.4 ±0.9cm. The circumference of the left mid-arm ranges from 23.5 to 33.8 cm with a mean value of 28.9±3.6 cm. There was a significant positive linear correlation between left mid-arm circumference and depth of epidural space (r = 0.93 and t =7.31 at p 0.001).