Vertebral Column PDF

Vertebral Column - The vertebral column is a complex made up of single bony units, called vertebrae. - It is located on the posterior part of the neck and trunk and is composed of 33 or 34 vertebrae, which articulate with each other throught the interposition of the intervertebral...

Vertebral Column - The vertebral column is a complex made up of single bony units, called vertebrae. - It is located on the posterior part of the neck and trunk and is composed of 33 or 34 vertebrae, which articulate with each other throught the interposition of the intervertebral discs formed by fibrocartilage. - The vertebral column can be divided into five parts or segments, in craniocaudal direction are as follows: - *Cervical part* consisting of 7 vertebrae - *Thoracic part* consisting of 12 vertebrae - *Lumbar part* consisting of 5 vertebrae - *Sacral part* consisting of 5 vertebrae fused together in the sacrum - *Coccygeal part* which includes 4-5 vertebrae fused together in the coccyx - The vertebral column is not straight but has a series of curvatures, both on the sagittal and the frontal plane. - In lateral projection, there are two curves with anterior convexity, called *lordoses* , and two curves with anterior concavity called *kyphoses*. - In particular, proceeding from top to bottom, in lateral projection, it is possible to observe: - A *cervical lordosis* between the first cervical vertebrae and the second thoracic vertebra - A *thoracic or dorsal kyphosis* between the second and twelfth thoracic vertebrae - A *lumbar lordosis* of greater amplitude in women from twelfth thoracic vertebra to the sacral angle, which is the angle between the horizontal plane and the upper surface of the sacrum, the amplitude of which is about 30°. - A *sacral or sacrococcygeal kyphosis* from the lumbosacral joint to the tip of the coccyx. Function of the vertebral column: - It supports the body in static and dynamic conditions - It protects the spinal cord and nerves and gives insertions to several muscles - Since the vertebrae contain red bone marrow, the vertebral column is also an important site of hematopoiesis. Parts of a typical vertebra *Vertebral body:* - It is the anterior and most voluminous part of the vertebra. - It is roughly cylindrical in shape and varies in size, shape and propotions in the different regions of the vertebral column. - Presents two intervertebral surfaces, one superior and one inferior, slightly concave and rought in the center (due to the fact that the spongy bone, at this level, comes up to the surface and rauses and smooth in the periphery, forming a contour of compact bont tissue). - The intervertebral surfaces are articulated to each other by the interposition of the fibrocartilaginous intervertebral disc which acts as elastic pads to absorb the numerous mechanical stresses sustained by the vertebral column. - The size of the vertebral bodies increases in craniocaudal direction, from the second cervical vertebra to the third lumbar vertebra, and this increase accounts for the increase in weight and pressure that they have to sustain. - From the fourth lumbar vertebra, proceeding in caudal direction, the width of the vertebral bodies decreases progressively until the tip of the coccyx. *Pedicle of the vertebral arch:* - They are two transversely flattened laminae, directed anterioposteriorly, that joint the body to the laminae of the vertebral arch, their superior and inferior margins are hollow to form the superior and inferior vertebral notches. - The juxtaposition of the vertebral notches of two consecutive vertebrae forms the intravertebral foramina, which give passage to the spinal nerves, *Processes of the vertebral arch:* - Pairs of transverse processes are formed from the junction of the pedicles with the laminae and are directed externally and posteriorly, acting as levers for muscles and ligaments, particularly for those that allow rotation and lateral inclination movements of vertebral column. - The transverse processes have structural difference in the various segments of the vertebral column. - Four articular processes, two on each side, two superior or cranial and two inferior or caudal, also originate from the junction between the pedicles and the laminae of the vertebral arch. - The superior articular processes have the superior articular facets at their ends, for the joint with the inferiorarticular processes of the overlying vertebra. - The inferior articular processes terminate at their ends with the inferior articular facets, for the joint with the superior articular facets of the underlying vertebra. - All articular facets are covered by hyaline cartilage. These articular processes form the movable joints of the vertebral column, which allow for small movements between the vertebra, which vary considerably between segments. - A spinous process projects posteriorly and inferiorly from the junction of the two laminae and is a site for muscle and ligament attachment. Cervical vertebrae The cervical vertebrae (C1-C7) have specific features that allow them to be recognized with respect to the other vertebral segments: - They are smaller than the other vertebrae because they have to support less load. - The body which increases in size proceeding from top to bottom. - Is quadrangular in shape, with the transverse diameter greater than the anteriorposterir one. - The superior intervertebral surface is concave transversely and is delimited laterally by the uncinate processes. - The inferior invertebral surface is convex transversely and in correspondence to the uncinate processes of the underlying vertebra, presents two depressions. - The pedicles of the vertebral arch are directed backward and outward. - The laminae of the vertebral arch are wide and thin. - The transverse process have foramina transversaria,which give passage to the vertebral artery and vein, [in the foramina transversaria of C7 only the vertebral vein passes]. - The foramina transversaria are delimited by two laminae, one anterior, connected to the body and one posterior, in continuity with the articular processes. - The [two laminae terminate at their ends with the anterior and posterior tubercles]. - The anterior tubercle [of the C6 is particularly developed and is called carotid tubercles] because, palpable at the base of the neck, [it represents a landmark for the common carotid artery]. - The articular processes are located behind the transverse processes and have superior articular facets that tend to be plane, inclined backward and upward, and inferior articular facets facing forward and downward. - The spinous process is short, almost horizontal, and is split (or bifid) from C2 to C6. - The vertebral foramina are relatively wide to accommodate the enlargement of the spinal cord present at this level. Atlas (C1) and Axis (C2) - Vertebra C1 atriculates with the head by the atlanto-occipital joint which allows the head to nod up and down on the vertebral column. - It lack a vertebral body which is fused onto the body of C2 during development to become the dens of C2. - There is no intervertebral disc between C1 and C2. - The atlas is ring shaped and composed of two lateral masses interconnected by an anterior arch and a posterior arch. - Lateral mass articulates superiorly with an occipital condyle of the skull and inferiorly articulates with the superior articular surface of C2. - Superior articular surfaces are bean shaped and concave, whereas the inferior articular surface are almost circular and flat. - The posterior surface of the anterior arch has an articular facet for the dens, which projects superiorly from the vertebral body of the axis. - The dens is held in position by a strong transverse ligament of atlas posterior to it and spanning the distance between the oval attachment facets on the medial surfaces of the lateral masses of the atlas. - The dens acts as a pivot that allows the atlas and attached head to rotate on the axis, side to side - The transverse processes of the atlas are large and protrude further laterally than those of the other cervical vertebrae and act as levers for muscle action, particularly for muscles that move the head at the atlanto-axial joints. - The axis has the dens which extends superiorly from the vertebral body. - The anterior surface of the dens has an oval facet for articulation with the anterior arch of the C1 - The two superolateral surfaces of the dens possess circular impressions that serve as attachments sites for strong alar ligaments, one on each side, which connects the dens to the medial surfaces of the occipital condyles. - These alar ligaments check excessive rotation of the head and atlas relative to the axis. Vertebra Prominens (C7) - Its spinous process, which is not bifid, is long and protrudes posteriorly, ending in a tubercle that can be easily palpated at the base of the neck. - The transverse process of C7 has a highly developed and laterally projecting posterior lamina, which sometimes may form the so called cervical rib. - The foramen transversarium is small and unlike what is evident in the first six cervical vertebrae, gives passage to the vertebral vein only. Thoracic Vertebrae - The thoracic vertebrae (T1-T12) are larger than the cervical vertebrae and their volume increases in craniocaudal direction. - All thoracic vertebrae articulate with ribs and thus have plane costal facets covered by hyaline cartilage. - The body of the thoracic vertebrae is shaped like the heart of a playing card and articulates with the ribs by two costal facets superior and inferior located in the vicinity of the pedicle of the vertebral arch. - The head of the ribs lies between the two vertebral bodies, articulating with the inferior costal demifacet of one vertebra and with the superior costal demifacet of the underlying vertebra. - The pedicles of the vertebral arch originates from the upper part of the body and have a very pronounce inferior vertebral notch. - The laminae of the vertebral arch are extended and overlap those of the underlying vertebra. - The transverse processes are developed and directed laterally. - The anterior surface presents the costal facet of the transverse process which articulates with the tubercle of the rib. - The ribs are articulated with the thoracic vertebrae both at the level of the vertebral bodies and at the level of transverse processes. - The articular processes are vertical, the superior ones are directed posteriorly, the inferior ones anteriorly. - The superior articular processes are also more developed than the inferior ones. - All articular processes have plane articular facets covered by cartilages. - The spinous process is very long and tilted downward and this inclination tends to increase in craniocaudal direction. - The vertebral foramen is oval and smaller than that of other segments. - T1 has a body that resembles the one of the cervical vertebrae and has uncinate processes. - The body of the latter has a larger and circular superior costal facet, for the joint with the head of the first rib, and a smaller inferior costal facet, for the joint with the demifacet of the head of the second rib. - T10 has a single superior costal facet for the joint with the tenth rib. - T11 and T12 articulate with the heads of the eleventh and twelfth pairs of ribs, the bodies of these vertebrae have complete costal facets, also the last two ribs articulate with the vertebrae ony at the level of the head. Lumbar Vertebrae The lumbar vertebrae (L1-L5): - Have a voluminous body which futher increases in craniocaudal direction, also the lumbar vertebra has a larger laterolateral diameter than the anteriorposterior one. - The pedicle of the vertebral arch are short and robust and have an inferior vertebral notch that is deeper than the superior one. - The laminae of the vertebral arch are thick and more developed in height than width. - The transverse processes are replaced by three processes, costal prosses, a laterally directed lamina, corresponding to the rib, mamillary and accessory processes, small reliefs located posteriorly to the previous one, one above the other. - The superior articular processes originate just behind the costal prosses, heading upward, and have superior articular facets in the shape of a hollow cylinder segment, facing posteriorly. - The inferior articular processes lead downward and have inferior articular facets in the shape of a solid cylinder segment, facing anteriorly. - The concavity of the superior articular facets and the convexity of the inferior articular facets allow movements of flextion, extension, lateral inclination and some degrees of rotation. - The spinous process is robust and shaped like a rectangular lamina directed horizontally backwards. - The vertebral foramen is triangular with an anterior base. -  Sacrum - The sacrum is a single bone that represents the five fused sacral vertebrae. - It is triangular in shape with the apex pointed inferiorly, and is curved so that it has a concave anterior surface and a correspondingly covex posterior surface. - It articulates above with vertebra L5 and below with the coccyx. - It has two large L-shaped facets, one on each lateral surface, for articulation with the pelvic bones. - The posterior surface of the sacrum has four pairs of posterior sacral foramina, and the anterior surface has four pairs of anterior sacral foramina for the passage of the posterior and anterior rami, respectively of S1 to S4 spinal nerve. - The posterior wall of the vertebral canal may be incomplete near the inferior end of the sacrum. Coccyx - It is the last segment, rudimentarly of the vertebral column, deriving from the fusion of four or five coccygeal vertebrae. - Has a pyramidal shape, with a superior base and an inferior tip. - Articulates with the sacrum to form, together with it, the posterior wall of the pelvis. - The base is formed by the superior invertebral surface of the first coccygeal vertebra that articulates with the apex of the sacrum. - Lateral and dorsal to the articular surface, two elevations, the coccygeal cornua, rise upward, which correspond to the superior articular processes of the other vertebrae and articulate with the sacral cornual (horns). - Laterally to the base, small transverse processes detach. - The tip correspond to the inferior invertebral surface of the last coccygeal vertebra and is directed downward and forward. - The ventral and dorsal surfaces of the coccyx present grooves that correspond to the fusion of the first coccygeal vertebrae. Editing Sacrum - Physiopedia *Vertebral canal:* - The spinal cord lies within a bony canal formed by adjacent vertebrae and soft tissue elements (the vertebral canal): a. The anterior wall is fromed by the vertebral bodies of the vertebrae, intervertebral discs, and associated ligaments. b. The lateral walls and roof are formed by the vertebral arches and ligaments. - Within the vertebral canal, the spinal cord is surrounded by a series of three connective tissue membranes (the meninges): a. The pia mater is the innermost membrane and is intimately associated with the surface of the spinal cord. b. The second membrane the arachnoid mater, is separated from the pia by the subarachnoid space, which contains cerebrospinal fluid. c. The thickest and most external of the membranes, the dura mater, lies directly against, but not attached to the arachnoid mater. - In the vertebral canal the dura mater is separated from surrounding bone by an extradural space containing loose connective tissue, fat, and a venous plexus. *Intervertebral foramina:* - Are formed on each side between adjacent parts of vertebrae and associated invertebral discs. - The foramina allows structures, such as spinal nerve and blood vessels, to pass in and out of the vertebral canal. - Is formed by the inferior vertebral notch on the pedicle of the vertebra above and the superior vertebral notch on the pedicle of the vertebra below. - The foramen is borded: a. Posteriorly by the zygapophysial joint between the articular processes of the two vertebrare. b. Anteriorly bt the intervertebral disc and adjacent vertebral bodies.  Vertebral canal Intervertebral foramina Joints in the vertebral column The joints of the vertebral column include: - *Intrinsic joints* represented by the intervertebral joints and the zygapophysial joints also the lumbosacral joint and the sacrococcygeal joint. - *Extrinsic joints* are joints of the vertebral column with the cranium, the ribs and the hip bones. Invertebral joints - The joints between the vertebral bodies from C2 to S1 are symphyses that are established between the intervertebral surface of the invertebral surface of the vertebral bodies. - The latter are slightly concave and covered by hyaline cartilage. - A biconvex, fibrocartilaginous invertebral disc is interposed between the articular surfaces of the vertebral bodies of two contiguous vertebrae and the joint is reinforced by the anterior and posterior longitudinal ligaments. - In normal vertebral column, the invertebral discs make up about [\$\\frac{1}{3}\$]{.math.inline} or [\$\\frac{1}{4}\$]{.math.inline} of its height. - They consist of an outer anulus fibrosus and a central nucleus pulposus, being thinner in the upper thoracic region and thicker in the lumbar region. - The thickness of the invertebral discs tends to increase in cranicaudal direction. - The presence of the invertebral discs allows torsion and lateral inclination movements of the vertebral column on the various planes. +-----------------------------------+-----------------------------------+ | *Anulus fibrosus* | *Nucleus pulposus* | +===================================+===================================+ | - *Is composed of | - *Is soft, eccentric and | | fibrocartilage whose fibrous | gelatinous.* | | component is more abundant | | | than that of the nucleus | - *Is anteriorly in the | | pulposus.* | cervical segments and | | | posteriorly in the lower | | - *Correspond to the anular | thoracic and lumbar | | epiphysis of the body.* | segments.* | | | | | | - *Corresponds to the central | | | part of the body.* | +-----------------------------------+-----------------------------------+ Zygapophysial joints - The joint between the articular processes of the vertebrae are called the zygapophysial joints. - Are plane joints that are established between the inferior and superior articular facets of two contiguous vertebrae. - The articular surfaces, covered by hyaline cartilage, are predominantly plane. - Only in the lumbar vertebrae, the articular afcets are slightly curved, thus allowing for greater sliding movements in this segment of the vertebral column. - The means of union are given by the joint capsules that insert in proximitly to the articular surfaces. Atlanto-occipital joint - The atlanto-occipital joint is the joint between the occipital bone and the atlas. - A pair of synovial joints that are between the occipital condyles and the superior articular surface of the lateral masses of the atlas. - The occipital condyles are convex and enlongated from front to back and laterally. - The articular surfaces of the atlas are in similar shape with the occipital condyles but are concave. - Each of these joints is enclosed by a joint capsule that inserts on the contour of the articular surfaces. - This joint is enforced by the anterior atlanto-occipital membrane alarge dense fibrous structure that from the anterior contour of the foramen magnum attaches to the superior margin of the anterior arch of the atlas. - Also is enforced by the posterior atlanto-occipital membrane, a large buut relatively thin membrane that from the posterior contour of the foramen magnum inserts on the posterior arch of the atlas. *Movements of the atlanto-occipital joint* *Flextion* *The occipital condyle slide on the superior articular facets of the atlas movingin posterior direction, increasing the distance between the occipital bone and posterior arch if the atlas. Altogether the entire cervical column flexes 40°.* -------------------------------------------- ----------------------- -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- *Extension* *The occipital condyles move in anterior direction. The occipital bone and the posterior arch of the atlas approach. Altogether the entire cervical column extends 45°.* *Rotation* *The occipital bone rotates around the atlas because the contralateral condyle slides forward and the ipsilateral condyle slides backward. The contralateral alar ligament is put into tension and exerts traction on the corresponding condyle by bringing it toward the dens of the axis causing a slight contralateral inclination. The amplitude of movement is 5°.* *Lateral inclination* *Modest movements of the occipital condyles in the lateral and medial direction do not exceed 3-5° in one or the other direction.* Atlantoaxial joints - The atlas articulates with the axis through three synovial joints. These are two joints between the lateral masses of the atlas and the axis (lateral atlantoaxial joint) and a (median atlantoaxial joint) between the dens of the axis and the atlas (anterior arch of the atlas and the transverse ligament of the atlas). - Lateral atlantoaxial joint has two plane joints, between the inferior articular surfaces of the lateral masses of the atlas and the superior articular facet of the axis. - The joint capsules is attached close to the articular surfaces. - The lateral atlantoaxial joint is reinforced by the anterior and posterior atlantoaxial ligaments which, from the inferior margin of the anterior and posterior arches of the atlas, attach to the anterior surface of the body of the axis and the superior contour of its arch, respectively. - Median atlantoaxial joint is established between the posterior surface of the anterior arch of the atlas and the anterior surface of the dens of the axis and between the posterior surface of the axis and the transverse ligament of the atlas. - It is a pivot joint in which the solid cylinder consists of the dens of the axis, with its anterior and posterior articular facets, while the hollow cylinder is represented by an osteofibrous canal consisting of the dens of the anterior arch of the atlas and the transverse ligament of the atlas. - Two distinct articular cavities exist in the joint, between the dens of the axis and the arch of the atlas and between the dens of the axis and the transverse ligament of the atlas. - The joint capsule is relatively weak and lossely compared, especially in its superior portion. - The median atlantoaxial joint is primarily involved in axial rotational movements. *Movements of atlantoaxial joints* *Flexion* *The inferior articular facets of the atlas slide backward and upward. The fossa of the dens of the axis moves downward and away from the dens. The distance between the posterior arch of the atlas and the spinous process of axis increases.* ------------------------------------ ----------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- *Extension* *The inferior articular facets of the atlas slide forward and upward. The fossa of the dens of the axis moves upward, anteriorly approaching the dens and posteriorly moving away from it.* *Rotation* *The osteofibrous ring which encloses the dens rotates around it. The lateral mass of the talas ipslilateral to the rotation moves posteriorly and in opposite direction (anteriorly) with respect to the contralateral. Starting from 20° of rotation there is a lowering of the atlas towards the axis caused by the convexity of the articular surfaces. The amplitude of movement reaches 40°.* *Lateral inclination* *The movements of the dens of the axis in lateral direction are so modest that cannot be measured and are accompanied by rotation.* Lumbosacral joint - Is the joint between the fifth lumbar vertebra and the sacrum. - The L5 participates in the joint with the invertebral surface and the inferior articular processes, the sacrum with the oval surface and the superior articular processes of its base. - The reinforcing ligaments are the same as the ones of the invertebral joints, in addition to the inferior bundles of the iliolumbar ligament, which joins the costal process of L5 to iliac crest. Sacroccygeal joint - Is a symphysis that is established between the apex of the sacrum and the superior invertebral surface of the first coccygeal vertebra, with a fibrocartilaginous between. - The joint is reinforced by five ligaments: - The anterior sacrococcygeal ligament, is stretched between the pelvic surface of the sacrum and anterior surface of the coccyx. - The two posterior sacrococcygeal ligament, superficial and deep, between the dorsal surface of the coccyx. - The lateral sacrococcygeal ligaments between the lateral part of the sacrum and the coccygeal cornu. - Allows small flexion and extension movements of the coccyx, which increases near delivery. Movements of the joints of the vertebral column - Cervical segment: - flexion and extension is good especially in the lower segment \- lateral inclination is good \- rotation that is maximal at the level of the median atlatantoaxial joint - Thoracic segment: - flexion and extension is poor get better as we go in the lower segments \- lateral inclination is good but get better as we go in the lower segments \- rotation is moderate but get better as we go in the lower segments - Lumbar segment: - flexion and extension is good especially in the lumbosacral joint \- lateral inclination is moderate \- rotation is poor *Plane of movement: sagittal* ------------------------------------------- ---------------- ---------------- ---------------------------- *Axis of rotation: transverse* *Flexion* *Cervical 40°* *Thoracic 40°* *Lumbar 60°* *Lumbar flexion* *70% at L5-S1* *20% at L4-L5* *10% at L1-L2/L2-L3/L3-L4* *Extension* *Cervical 45°* *Thoracic 15°* *Lumbar 30-35°* *Trunk flexion (thoracolumbat): 100-105°* *Trunk extension (thoracolumbar): 45°* *Plane of movement: frontal* -------------------------------------------------- ---------------- ---------------- -------------- *Axis of rotation: sagittal* *Lateral inclination* *Cervical 40°* *Thoracic 25°* *Lumbar 15°* *Lateral trunk inclination (thoracolumbar): 40°* Ligaments - The anterior longitudinal ligament is a long ribbon that adheres to the anterior surface of the vertebral bodies and, in part of the intervertebral discs from the occipital bone to the pelvic surface of the sacrum. - The posterior longitudinal ligament is located on the posterior surface of the vertebral bodies, within the vertebral canal and extends from the occipital bone to the sacral canal. - It has a festooned shape because it is thinner where it adheres to the vertebral body and wider at the level of the intervertebral discs, to which it strongly adheres. Remote ligaments - The remote ligaments, which hold different portions of the vertebrae together, are represented by the ligamenta flava, the interspinous ligament, the supraspinous ligament and the intertransverse ligaments. - Ligamenta flava is rectangular in shape, they connect the laminae of adjacent vertebrae and are located in the vertebral canal. - They are stretched between the inferior margin of a vertebral lamina and the superior margin of the underlying lamina. - There are two in each pair of vertebrae and they close the space interposed between the laminae. - Interspinous ligaments, they join the inferior margin of a spinous process with the superior margin of the underlying spinous process and continue anteriorly into the ligamenta flava. - Supraspinous ligament, it is a strong fibrous cord stretched from the occipital bone to the dorsal surface of the sacrum. - It joins the apices of the spinous processes of the vertebrae and anteriorly with the posterior margin of the interspinous ligaments. - In cervical segment of the vertebral column the supraspinous ligament is highly developed and thicker, forming the ligamentum nuchae that is stretched between the external occipital protuberance and the spinous process of C7. - Intertransverse ligaments, they are bundles that join the apices of the transverse processes of adjacent vertebrae. - They are poorly developed in the cervical segments of the vertebral column and show greater consistency in the thoracic and lumbar segments. - In the latter segment, they are stretched between the costal process of the lumbar vertebra and mammillary process of the underlying vertebra. Remote ligaments of the atlantoaxial joint - The dens of the axis is attached to the occipital bone by the apical ligament of the dens, which inserts on the anterior contour of the foramen magnum. - The dens is also attached by the alar ligaments, which from the dens of the axis lead to the medial surface of occipital condyles. - The cruciate ligament of the atlas is located posterior to latter ligaments and is formed by the transverse fibers of the transverse ligament of the atlas and the longitudinal fibers of the longitudinal bands that descend from the anterior contour of the foramen magnum to the posterior surface of the body of the axis.