ABSTRACT
The functional importance of the ligamentum flavum to the integrity of the vertebral column and the frequency with which they are encountered surgically justify consideration of its anatomy in adults. The aim of this study was to make a detailed investigation of the gross and microscopic anatomy of the ligamentum flavum. The information reported in this study is of clinical value in the practice of lumbar epidural anaesthesia. The material used were 14 normal male cadaveric lumbar vertebral columns in the middle and old age. Length, width and thickness of the ligamentum flavum were measured in the lumbar region in millimeters. Computed tomography was done on 30 patients [18 males and 12 female] complaining of problems far away from the lumbar region that was studied. Width and thickness of the ligamentum flavum were measured by CT. Various portions of the 14 gross specimens were chosen for microscopic study. Sections were prepared and stained by Masson trichrome and Orcein and examined by light microscopy. The ligamentum flavum was found to be attached inferiorly to the superior edge and the posterosuperior surface of the lamina below. Some deep fibres were attached to the antero superior surface of the lamina below. Thus the ligamentum flavum was considered to be formed of superficial and deep parts. The ligamentum flavum was attached superiorly to the inferior edge and the anteroinferior surface of the lamina above. The medial border of the ligamentum flavum corresponded to the base of the spinous process. The lateral border extended as far as the intervertebral foramen. The direct-ion of fibres of the superficial part of the ligament was upwards and medially towards the spine and was more oblique in its lateral portion close to the intervertebral foramen. The direction of the deep fibres was craniocaudal. The length, width and thickness of the ligamentum flavum of the normal male cadavers had a mean of 16.4 +/- 5.2mm, 18.7 +/- 3.4mm and 4.5 +/- 0.8mm respectively. By CT of thirty patients, the width and thickness had a mean of 16.7 +/- 2.6mm and 43 +/- 0.6mm respectively. Histological results showed that the ligamentum flavum was chiefly made up of elastic connective tissue which in older age specimens decreased due to its fragmentation with increase in the amount of the collagenous tissue. The information reported in this study is of clinical value in the practice of lumbar epidural anaesthesia. It is suggested that the epidural puncture can be best performed through the lower and medial portion of the ligamentum flavum [slightly lateral to the midline] to be away from the intervertebral foramen