 anatomy of spine or the vertebral column as all of us know that the vertebral column is an amazingly complex structure which is designed to meet the mobility and stability and simultaneously protect the spinal cord. So, this vertebral column is made up of 33 vertebrae of which may be 24 or pre-sacral, 7 cervical, 12 thoracic, 5 lumbar and 5 sacral and 3 to 4 oxygel vertebra with an intervertebral disc which are 23 in number as C1 and C2 do not have the intervertebral disc. The adjacent vertebra with the intervertebral disc and the ligament is complex associated with it make one functional spinal unit. In the fetal life if you look at the curvatures because it is a curved rod. So, initially there is a curvature which is convex posteriorly and this posterior curvature is actually maintained in the thoracic and the sacral regions and as the child begins to hold the neck a laudotic curve appears that is in the cervical region and the second laudotic curve appears when the child begins to stand upright and walk. So, these are the primary curves which are kyphotic that is thoracic and sacral and the ones which are secondary curves are the laudotic curves seen in the cervical and the lumbar region. Now, because of it being a curved rod it is not a straight rod. So, this curvature gives it a 10 foldability to resist the axial compression. Looking at the center of gravity we can see that it passes through the dense in the spinal column and then anterior to the thoracic spine and then from the sacral promontory. Now, if we come to the parts of a typical vertebra we all know that it has an anteriorly cylindrical shaped body and posteriorly posterior structure which is an irregular shaped structure and is known as the vertebral arch. This vertebral arch is further divided into two components that is the pedicle which is lying anterior to the articular processes and the posterior elements. The pedicle which is lying anterior to the articular processes is well designed that is it is tau thick and which is actually meant for transmitting the bending forces from the posterior elements to the vertebral body. By posterior elements I mean the laminas, the articular facets, the transverse processes and the spine. If you look at the laminas they are actually centrally located and they are the origination point for rest of the posterior elements here. Now, this laminas are actually here kept to you know transmit the forces from all the posterior elements and then to the pedicles and from pedicles to the vertical body. So, to transmit this forces it is the anterior part of the lamina which actually we see between these two facets is known as the parts. So, this is the part which is responsible for transmitting the forces from posterior elements to the pedicle. So, these are actually known as the bending forces because the lamina is oriented vertically and pedicle is oriented horizontally. So, these bending forces are actually transmitted through the parts or we say parts interarticular is because it is between the superior and inferior articular facets. So, it is subjected to the bending forces. So, if we see descend down from cervical to lumbar region we see that it is most developed in the lumbar spine and of course, because the weights are increasing as we descend down. So, this also shows an increase in the amount of cortical bone to accommodate these increased forces and if there is an insufficient bone in this region it can make them susceptible to the stress fractures. Coming to the spinous and transverse processes they are the sites for muscle attachments and of course, they serve to increase the lever arm for the muscles of the vertebral column. Now, the articular processes which we have superior and inferior articular facet they form synovial facet joints they are complementary to each other and also they form the posterior boundaries of the inter vertebral foramen through which the nerve roots are coming out. And this capsule of these joints is actually closely related to medial branches of the dorsal remi of the spinal nerves. So, any injury to these will denervate the muscles of the back and these together form a supporting column which is referred to as the articular pillar. Now, as we saw so the parts so the vertebra which they adhere to a common basic structural design, but they show regional variation in size and configuration that reflects actually the functional demands of a particular region. So, let us see one by one how the features change. Now, if you look at the vertebral body in the cervical region it is very very small as compared to the thoracic and the lumbar vertebra. The transverse diameters are much more than the apiantro posterior diameter and also in the cervical region there is a lateral liping which is known as the yansinate process. So, this discull surface that is which is facing the inter vertebral disc restricts both the lateral and the api gliding movements. In the thoracic region especially the mid thoracic region the transverse and the antropocere diameter are almost equal, but as we you know go up the cervical or the lateral the lumbar extremes the lateral dimension will increase towards these extremes. So, in the thoracic region if you look at the ventral and the dorsal height the ventral height which is the vertical height and the dorsal height. In the thoracic region the dorsal height is more than the ventral height which actually contributes to the normal physiological kyphotic curve in this region and also the body has a unique demi-facet for articulation for the ribs. The lumbar body is massive where the transverse diameter is much more than the antroposterior as well as the height. Now in the lower lumbar vertebra especially the L5 the body and inter vertebral disc both the ventral height is much more than the dorsal height giving it a law-dotic curve rather is a wedge shaped and which actually contributes to the formation of lumbosacral angle. The inferior border of the body in the cervical region overhangs the lower vertebra. Now looking at the actually what I said initially that if you look at the transverse diameter or the width the AP diameter or the depth in the cervical region we can see that it is around 16 to 17 millimetres. There is a gradual increase up to the C5 but there is a steep increase in the transverse diameter up to the second thoracic vertebra more or less constant. Again there is a steep increase and by L5 the dimension has increased up to 46 to 47 millimetre that is 4.6 to 4.7 centimetres. The depth also shows the same pattern and again in the L4 actually we have the maximum depth in the L5 there may be a small decline towards the depth. Now this is actually all designed to permit the efficient load carrying capacity of the vertebra. Now when we look at the ventral and the dorsal height ventral height and behind we have the dorsal height they also the ventral height initially may decline by C6 but then again a sharp increase in this but as we look at the lumbar region the dorsal height that is the posteriorly shows a decrease up to the L5 vertebra. Coming to the pedical anatomy actually four important dimensions are generally used that is we have the diameter or the thickness of the pedicle that is the transverse pedicle width and we have another that's called transverse pedicle angle which is the angle between the axis of the pedicle and the midline axis the sagittal line okay. In the sagittal view we have the height that is the sagittal pedicle width or the pedicle height and we have the sagittal angle that is the angle which the pedicle axis forms with the horizontal plane. Now this the transverse actually talks about the tells us about the orientation of the pedicles in the transverse or the horizontal plane whether they are directed posteriorly postrolaterally or postomerially whereas if you look at the sagittal angle it indicates whether they are oriented rostrally horizontally or they have a chordal bend. Now transverse pedicle width if we go down from cervical to lumbar we can see that it's around six millimeters here may decline there is a gradual increase and T2 has the you know the pedicle width which is around 7 to 8 millimeters showing a steep decrease in the mid thoracic region T4 pedicle is actually the narrowest pedicle we say and then we see here that by the L5 vertebra there is 16 to 17 millimeter of the pedicle width. So this pedicle width is very important because here the manipulation with the pedicle screws is there is more space to manipulate this area. Coming to the transverse pedicle angle we can see here that is the angle which it is making with the mid sagittal plane it is around 43 to 44 degrees here we can see how they are directed they are directed now postrolaterally when we are looking at from the anterior aspect from the posterior aspect we will say they are converging but from the anatomy we look from the anterior aspect so we say that they are directed postrolaterally because they form a very cute angle of 43 to 44 degrees and then there is a sharp decline in this angle and we can see the direction of the pedicles in the thoracic region now they are you know moving towards the more posterior direction and it may be up to 0 degrees that is parallel to the mid sagittal plane and we go down in the minus direction but as the lumbar vertebra they again start to increase and the angle reaches up to the 25 to 30 degrees in the lumbar vertebra the transverse pedicle angle the sagittal pedicle width also shows the more or less same width in the cervical region but steep increase in the from T1 to T5 vertebra mid thoracic again has more or less similar sagittal height steep increase in the lower thoracic region but again there is a bit of decrease in the sagittal height in the lumbar region but actually the dimensions are so massive that it doesn't contribute so much now the sagittal pedicle angle that how this thing is directed if this is the the angle the sagittal pedicle angle so it is telling us about the directions of these pedicles now if if we looking from the anterior aspect they are directed upwards or if you're looking from behind they are directed downwards so in this we can see the angle which is now towards the positive side in the thoracic region because they are directed more upwards when we are looking from the anterior aspect and when we are looking from the posterior aspect from postro superior to antero inferior direction they are going down so this is in the cervical region the angle is around minus 6 to 7 or 8 degrees whereas we can see in the thoracic it's more positive and in the lumbar again they you know tend to become more horizontal the laminas are thin and slightly curved and they face post to medially in the thoracic region they are slightly thick and broad and they overlap overlap is minimum in the lumbar region as far as the spinous process is concerned this is short slender and horizontal with the bifid tips in the thoracic region the spines are actually oblique but more so the oblique actually the which tends to overlap is much more in between T5 to 28 but the two extremes that is towards the cervical and the lumbar extreme they tend to become horizontal and in the lumbar region they are broad thick and horizontal as far as the transverse process variation is concerned in the cervical region if we see this is the transverse process this is the pedicle so they arise from the junction of the vertebral body and the pedicle whereas here if we see the transverse process arise from the junction of the pedicle and the parts so in the cervical region they have foramen transversarium which transmits the vertebral artery vein and maybe branches from the cervical thoracic ganglia in the thoracic region they are thicker they are longer and they are directed more postural laterally and they bear costal fissure for the tubercles of the ribs in the lumbar region if we see they are thin and long and slender and they are directed just laterally they are little more ventrally placed and in the l5 they actually find more ventral attachment from the body so we say they are triangular and they are thick and they have accessory process at the postural inferior aspect of the of their root coming to the facets now it is the facets orientation which actually decides the movement in the particular region of the vertebral column so looking from behind if we see the superior articular facet in the cervical region they are flat and oval and they face postural superior and medial so this direction is very important we look at the thoracic region again they are flat and oval but this face postural superior and more laterally and in the lumbar region the direction has completely changed they are vertically oriented they are concave and they face more postural medially and of course they show a very thick projection on the posterior border that is the mammillary process now it's because of their direction and their angulation with the horizontal coronal and the vertical plane we can see that the regional variation in the mobility of the spine and this depends on not only the geometry of the articular facets but the orientation and the properties of the facets and the of course related ligamentous complex so looking at the three movements which are actually possible because there are six degrees of freedom so we have flexion extension lateral bending and axial rotation now in the cervical region if we see the axial rotation is the maximum around 45 degrees they say 44 to 45 degrees both ways that is this kind of a movement and this axial rotation is actually possible at C12 which we call it as atlanto-axial and we say it has no no joints so the axial rotation is maximum in this region and then we have flexion extension possible up to 25 degrees but the lateral bending is not really so much possible but if we see the actually flexion extension is more possible at the atlanto-oxipital joint because of the special kind of geometry the atlas condyles have in the mid cervical region we have flexion extension up to 20 degrees we have lateral bending around 10 degrees and rotation is minimized we say that in the cervical column most of the 50% of the movements are at atlanto-oxipital or atlanto-axial joint thoracic part of the spine shows minimum movements in all directions that is the stabilizing factor here so we have actually almost nil flexion extension a bit of lateral bending and axial rotation is still there because of their orientation and they lie on the arc of the actually axis of rotation coming to the lumber region again because of their geometry now flexion extension has increased the lateral bending is again minimal but axial rotation is not possible because they are oriented more vertically the atypical vertebras that is the cervical first which is the atlas we all of know has there's no body it has lateral masses which are connected by the short anterior arch and a long posterior arch this bears a facet for the dense here and this are the kidney-shaped aty superior articulating facets which are permitting more of flexion and extension so we call them as yes yes joints for a man transversarium for the vertebral bodies the inferior facets are actually more you know flat and oval complementary to the the superior facets of the C2 now posterior arch has the important relation that is a vertebral artery from coming from the for a man transversarium and these first occipital nerve we can see here the vertebral artery and the first cervical nerve related to the posterior arch of the atlas now second cervical vertebra is again atypical and unique in that that it has the centrum the body and from the body projects a structure which is called the dense now this dense has a tip and a base and here is the body now if you look at the part here these are the superior articular facets which are directed actually more laterally and they are kept horizontally this is the lateral mass the for a man transversarium in the transverse process and this is the inferior articular facets now by definition if I go by just the anatomical definition if this is the superior articular facet this is the inferior articular facets so this is the parse this is the parse interarticular is what is the pedicle the one which connects the centrum with all the posterior elements so this becomes the centrum that is more you know side with the superior articular facet but I think most of the literature says that that this part is the pedicle this is the part and here's a pedicle now if you look at this symbology of the axis actually develops from the center we say from the sclerotome five six and seven the occipital sclerotomes are four so it's the five six seven which are c1 c2 and c3 the first cervical second and the third now they say that it's put the sclerotomes as x y and z so the x gives rise to the tip of the dense the y as the base of the dense and z segment gives rise to the centrum of the axis so there is a temporary intervertebral disc which actually is seen between the y and z which fuses later in life and if the x does not fuse with y and z it's a condition that is os terminal and if the x y complex does not fuse with the z is os odontidium or it's like the dentosentral syncontrosis still persist and any abnormalities in this region can give rise to the CVJ abnormalities this is just to show you the vertebral artery on the posterior arch of the atlas how it is related coming to the ligamentous anatomy we have anterior longitudinal posterior longitudinal ligamentum phlegm the capsular ligament the interspinus and the supra spinus ligaments now the anterior longitudinal ligament which extends from sacrum to C2 and beyond that it is continuing actually as the anterior atlantoexial and the atlantooccipital membrane and it is broader caudally and thicker more on the cervical and the lumbar region because in the extension it gets stretched and the tensile strength of this ligament is greatest at the high cervical lower thoracic and the lumbar region now looking at the opposite the bodies and the intervertebral disc it's thicker opposite the vertebral bodies than the intervertebral disc and it's tightly adherent here whereas it is loosely adherent and tries to fill the concavity between this put in three layers superficial intermediate and deep the superficial can span more than three to four vertebral levels intermediate two to three and deep are just connecting the adjacent vertebras it's a stronger ligament stronger than PLL because PLL is actually will be stretched in the flexion and along with that there all the posterior ligaments which are behind like ligamentum flower interspinus will be stretched in the flexion is only the anterior longitudinal ligaments but is stretched in the extension we can see that here I have already shown now posterior longitudinal ligament also extends from the sacrum to the C2 and beyond C2 the posterior longitudinal actually continues as the membranar tictoria which finds its attachment to the clivus here just above the margin of the foremen magnum in the lumbar region it is very thin and resistance to actually axial tension is lesser than the anterior longitudinal ligament maybe because it's closer to the the IAR the instantaneous axis of rotation stressed inflection and extend ligamentum flower which is actually connecting the adjacent lamina the ventral surface of the cordal lamina to the dorsal borders here of the rostral lamina and this continues as the posterior atlantoxapital membrane forms the posterior smooth surface of the vertebral canal now this actually is you know is in the segments it is not a continuous ligament and in the midline it shows a cleavage plane through which the veins can communicate like their internal and the posterior external vertebral venous flexes and also it can give a surgical entrance to the epidural space it extends laterally to cover the articular capsule now this is the only ligament which has a very high amount of elastin and it can be stretched up to 80% without damage it's strongest in the lower thoracic, lumbar and weakest in the mid cervical when we look at more posteriorly now between the ALL and PLL which were now here at here atlantoxapital and membranar tectoria in this region we have some additional ligaments anterior to the membranar tectoria we have the cruciform ligament which has a vertical and a horizontal component and this horizontal component we can see here is the transverse ligament membranar tectoria cut through you can see the transverse ligament which actually is stronger than the dense transverse ligament is stronger than the dense it is said that dense usually fractures before even the ligament rupture so it is that stronger ligament and it has a fibrocartilage surface of which the dense can glide over the ailer ligaments are from the sides and we have the apical ligament from the tip of the dense. Ailer ligaments are slightly weaker in fact a combined head flexion and rotation may avoid sometimes both I mean one or both the ailer ligaments the inter spinous and the supra spinous ligaments now if you look at the concept of the spinal stability the two column and three column concepts have been proposed where the dorsal and the ventral columns that is the anterior column so the dorsal column is where the posterior elements and the ligament is complex and the associated complex anterior column is vertebral body the inter vertebral disc and the anterior longitudinal ligament but the three column concept by Dennis says adds a middle column to this posterior column remains the same and it's the anti the anterior column which is split so the anterior column has the ventral part of the body ventral annulus fibrosis and the ALL whereas the middle column has the dorsal part of the body the dorsal part of the annulus fibrosis and the PLL may be this is to explain some of the fractures in which the different components the columns are involved.