 Welcome to noon conference hosted by MRI online noon conference connects the global radiology community through free live educational webinars that are accessible for all and as an opportunity to learn alongside top radiologists from around the world. We encourage you to ask questions and share ideas to help the community learn and grow. You can access the recording of today's conference and previous noon conferences by creating a free free MRI online account. Today, we are honored to welcome back to the noon conference stage Dr. Samir Ranega for a lecture entitled Thoricolumbar spine injury at CT, a systematic search pattern. Dr. Ranega serves as a staff radiologist at University Hospital in Muscat, Oman and is a dedicated faculty member in the radiology residency training program. With an interest in various subspecialties, he blends his clinical skills with a strong interest in medical education. He's involved in teaching medical students, residents, fellows and practicing radiologists in India and Oman and participating in international educational programs. He's a member of the annual meeting program planning committee for RSNA for the emergency radiology subspecialty and our viewer of the educational exhibits for RSNA. We're glad he's here today to share his expertise. At the end of this lecture, please join him in a Q&A session where he will address questions you may have on today's topic. Please remember to use the Q&A feature to submit your questions so we can get to as many as we can before our time is up. With that, we are ready to begin today's lecture. Dr. Ranega, please take it from here. Thank you. So, let me share my screen. Okay. You can see my screen, right? Yes. Okay. Okay. So, thank you, Ashley, for this invitation and for the introduction. I'm Sameer Ranega. I work at the University Hospital, Makka, Oman. It's evening in Oman, 8 p.m. So, good evening to all of you from different time zones. And, well, the noon conference of MRI is one of the best online accessible resource available during the pandemic and after the pandemic. And I would like to thank MRI online for stepping up during the pandemic to make this radiology education accessible to all. This was my second known conference, the first one I gave in 2021. And in next 45 or 50 minutes, we are going to learn about the role of imaging in thoracolumbar spine trauma assessment with emphasis on CT and systematic search pattern. I do not have any conflict of interest to disclose. The, some of the amazing illustrations which I'll be going to use in this presentation were prepared by Matt Skalski. Matt is a, we collaborated on several projects, but the article which we published in 2016, Radiographics. Matt prepared this, some of the illustrations and we are going to use it. There'll be few abbreviations which I'll be using during my presentation. So, motor vehicle collision and fall from height are some of the commonest mechanism for the thoracolumbar spine trauma and fractures. And almost two-third of the spine fractures occur in this region. Among thoracic and lumbar region, the T2 to T10 is relatively uncommon fracture. Majority of fractures occur between T10 and L2 because this thoracolumbar junction is biomechanically transitional zone and susceptible zone to fractures. Lumbar sacral spine is relatively less commonly involved. These fractures are important because up to one-third of these fractures result in neurologic injuries, some form of, at least 30% of the fractures are associated with some form of abdominal or other associated injuries. 15% of the fractures are non-contiguous fractures so that when you see fracture in thoracolumbar spine, there is possibility that the other spine is also involved in at least one in eight patients. And quite often these fractures are delayed and diagnosis or they are missed completely altogether. So, in this presentation, what we are going to do is, my learning objective is to use the CT search pattern to detect the fractures. Once fracture is detected, how to describe it using the terms which are understandable by our surgical team and we use the uniform same terms. We'll learn how to discriminate different similar looking injuries on imaging, particularly with the CT scan and how not to miss these fractures on imaging. At last, we will understand that how this information is useful to our treating trauma surgeons to decide which patient will go to operating room, which patients will go for non-operative management. So, this is the outline of my talk. I'll start with some of the concepts important for spine trauma. Then we will understand how to approach a CT using a systematic search pattern. I will show you plenty of cases and examples, some spot images and some state of images to show the pattern recognition we are going to learn during this presentation. And last but not the least, throughout this presentation, I'll show you or I will share a lot of practical tips which will be useful in day to day reporting. So, as far as concepts are concerned, we'll learn about three important issues, the anatomy and biomechanics, the imaging appropriateness and spine trauma and fracture morphology and the classification. So, quickly understand the biomechanics and anatomy of the spine relevant to the spine trauma. And this is what is described as the motion segment of the spine, which is a basic motion unit of the spine and it's the smallest functional unit. The spinal column can be divided into anterior and posterior column. Anterior column is vertebral body, ALL, the disc and the PLL. The posterior column is neural arch and all the ligaments which connects the neural arch which is called posterior ligamentus complex. The posterior tension band is important to understand and posterior tension band consists of neural arch which are the bony structures which includes pedicle, superior and inferior articular vertebrae, the lamina, the spinous process, the facet joints and the transverse process. The ligament which connects these different structures from cranial to caudally, in constitute what is known as posterior ligamentus complex or PLC. And they include the facet joints, inter-spinus ligament, supra-spinus ligament and ligamentum flava. So, all of this four ligament together are called the posterior ligament complex. As we can see, the supra-spinus ligament connects the tip of the spinous processes. The inter-spinus ligament connects the adjacent spinous processes. The ligamentum flava connects the lamina to the upper and the lower vertebrae body contiguously and they are seen in continuation with the inter-spinus ligament. And facet joint capsules trend under facet joint. All of these ligaments are very critical in restraining the translation, rotation and flexion movement. And this is the main component of the tension band working like a cable in a lifting crane. When it comes to imaging appropriateness, CT is often used as a first-line imaging in all high-velocity trauma. Radiographs are used as a screening modality in low-risk patients. However, any abnormality you see on radiographs or even suspicious abnormality on radiographs, CT should be done as the next imaging. And even when radiograph is normal, if clinical suspicion is high for fine trauma, CT should be done in this patient as well. MRI is complementary to CT in high-risk patients. MRI is the imaging modality of choice if x-rays are normal or x-ray shows osteoporotic compression factor. And any patient who has a neurologically positive fine trauma, MRI is something which is done in all the patients. As far as the classification of the spine trauma is concerned, the whole idea of classifying the spine trauma is to unify the description of the injury. This is what happens between the radiologist and the referring team to decide whether the spine trauma is stable or unstable based on the degree of the injury that happens. And last but not the least is that any spine trauma classification should guide the treatment and it should improve the outcome if it's appropriately used. So all the spine trauma classification which are used historically, all of them are imaging based. Earlier it was based on radiograph and later on they are based on the CT scan. The early classification system were more qualitative and mechanistic. That means they are pattern based which describes the fracture morphology and different patterns which we are going to learn. Injury mechanisms like flexion, like rotation, like distraction, so on and so forth. And last is instability, whether the fracture pattern which is seen on the x-ray or a CT scan will result in instability or not. The recent classification system are more numeric. They are based on the fracture pattern severity plus soft tissue injuries as can be determined on CT or MR along with the presence or absence of the neurological symptoms. So if you start from the beginning, it started with 1932 Bowler and then the Watson given 1938, Nicole in 1949. But one of the most important classification was given in 1963 by Holtzwerth at that time only a cancer available and he described the spine of a vertical two column. The anterior column is vertical body disc and the ANL PLN. The posterior column was the neural arch and the posterior ligamentus complex. Even the first guy who came up with that posterior ligaments are important tension bands. Then Dennis in 1983 came up with the three column classification. The classification they divide the anterior column into anterior and middle column. Then McAfee in 1983 came up with another classification. The major classification was the original OA classification which came in 1995, which was one of very difficult classification to use. And so, Vokero in 2005 came up with the stillit classification which he himself updated the OA in 2030. So let's understand the three column concept of Dennis, which is very important to understand and still makes a good portion of many classifications. So Dennis divided the anterior column of the Holtzwerth into two parts. So the anterior column can be divided into anterior and the middle column. The anterior column consists of the anterior two-third of the vertical body, anterior two-third of the disc and the ANL. The middle column consists of the posterior one-third of the vertical body, posterior one-third of the disc and the PLN. And everything behind the PLN was the posterior column. What Dennis believed that the middle column is very important in the stability and he proposed that fracture or injury of any two contiguous column will result in the instability of the spine. So either anterior and middle column fails that will result in unstable spine or if middle or posterior column will fail it results in the unstable spine. Of course, if all the three columns are injured it will definitely result in unstable spine. So we will learn a little bit later on all of this unstable or unstable spine needs some form of surgical correction in order to make the spine stable again. McAfee in 1983 came up with this classification which was based on the pattern and he used some of the descriptive terms like wedge compression, stable burst, unstable burst, flexion destruction, joint translation, and so forth. However, in current time two most widely used classification system, both of them were proposed by the Vakaro et al. In 2005 the spine trauma group came up with CLICS which is the thoracolumbar injury classification system which is based on the fracture morphology and the neurology. And this classification was point based and it determines what will be the treatment of these fractures. In 2013 the same group along with the OA modified the AO classification and that is what is called the updated AO classification or AO TILICS classification which again is based on the morphology which is simplified clinical behavior and some of the modifier as we will learn detail in the next few slides. So in TILIC classification injury morphology can be of four types compression injury will get one point burst injury will get two points rotation or translation injuries will get three points and destruction injuries will get four points. TILICS is the first group which comes up with the importance of the posterior tension bent and they say that if posterior ligament is complex is injured that will get an additional three points. If the posterior ligament is complex is intact that will be zero point and if it's indeterminate it will get two points. If you total the morphology points and the PLP integrity point you will come up with a score. So the score is less than four that means one to three these patients are operated nonoperatively they are not operated they are conservatively treated. If the score is more than four this patient has surgically treated because those fines are unstable. However if the point score is exactly four then the choice to treat by surgery or by nonoperative is based on the surgeon's own choice. In 2013 the updated AO classification again has similar morphology of injury so in compression injury is called A type of injury. It involves primarily the anterior column that means the anterior plus middle column and it has total five types A0 to A4. A0, A1 and A2 are compression fractures A3 and A4 are different types of burst fracture so compression plus burst all of them comes under the group A. The destruction injuries or the B injuries which primarily involve the flexion tension bend or extension tension bend. Most of the patients the destruction injury occurs in the flexion bend which is the posterior ligament complex or the posterior tension bend. And there are three types B1 and B2 involves the posterior group and B3 involves the anterior group. The anterior tension bend injuries are extremely rare in the absence of the fused or ankylospine. So we will not go into detail of the B3 however B1 and B2 are very very important injuries which we learn. And last but not the least is the translation injuries where one vertebral body moves in relation to the other vertebral body and that is called C type of injury and there is one C type so either translation is present or absent. So A and B1 injuries are single level injury are called monoostotic injuries while B2 and C are adjacent level injuries. So what we will do today is we will try to learn the basic principles of systematic search pattern on CT without going into the detail of this classification. However this morphology what we will learn will help us to use any of the classification system your surgeons are using. So based on the morphology so fracture morphology depends upon the failure mode of the final column and fracture morphology can be compression fracture which primarily involves the anterior columns burst fracture which involves anterior plus middle column. Distraction injury it is a tension bend injury it can involve posterior tension bend or anterior tension bend as I told you that the anterior tension bend injuries are extremely rare. Only seen in patients who have entylones with the fused spine so majority of the tension bend injury you will see in your practice involves the posterior tension bend which is called distraction injury. And last but not the least is the translation injuries where all three columns anterior middle and posterior columns are involved. So basically at the end of this presentation you will be able to confidently decide the morphology of the fracture into one of these four types based on how they are seen on the CT side. So let's see four different types of fractures the most severe is the fracture dislocation as I told you that in this one vertebral body moves or the spinal column moves in front of the vertebral body which is injured. So this is translation injury and this translation injury can be vaginal plan can be coronal plan or axial plan so most severe type of injury. The second most severe type of injury is what is called flexion distraction it used to be called a chance type of fracture and this is the type of injury where the posterior column failed due to the tension. So it's called tension failure due to distraction because the parts get separated from each other vertically get separated that is what is distraction force is. Compression forces will bring the part together so it will result in the collapse of the vertebral body while distraction forces will separate the parts either at the legamentus level or bony level and that is what we are going to learn. The third type of fracture which is the least severe type of fracture which is called compression injury and it primarily involve the anterior vertebral body and it only involves the anterior column. And the fourth type of injury which is the burst fracture which is primarily due to axial load and flexion injury which involves both anterior and middle column of the tennis. So in terms of severity the translation injuries are more severe than the posterior column that is a distraction injury then the burst injuries and the least severe injuries are the wedge compression fracture. So when you are looking at the CT you can start with the burst injury and then go to the next burst injury then the bad injury and then the not the bad injuries right. So that way you can go ahead or you can go the reverse where you start with the best injuries and then you go to the more severe injury more severe and the worst injuries. So let's see how to look at it okay. So first thing is when you have a CT what I do is that the coronal and sagittal reconstruction bone windowing and we look at the 2.5 mm section and first we look for the alignment and alignment is looked for to diagnose type C injury which is the translation injury in the a o classification. So how to look for the alignment of the sagittal by looking at this smooth curved arc type of lines which connects the anterior vertebral body which is called anterior vertebral line. The green one is the posterior vertebral line the red one is the pinolemina line and the last one is the intraspinus line. So we look at this four line where is the miller to what we see in cervical spine. In terms of alignment on coronal images we look at this lateral vertebral line which connects the lateral part of the vertebral bodies and this will help you to decide whether there is a translation in the coronal plan or not. So this is how we look at the translation injury in a systematic pattern on a VD. How do we look at the distraction of the posterior column so distraction of the posterior column involves the posterior vertebral arch and as you can see it here. So it involves the neural arch so one is the pedicle two is the past interarticular is three is the superior articular process four is the inferior articular process. This is the lamina and this is the spinal process so any fracture involving any of this three six structure which has a transverse orientation. So if this fractures are horizontally oriented which can be seen on the sagittal CT or can be seen on a coronal CT those are the signs of the distraction injury. So distraction injuries can be bony or ligamentus or mixed when it's a bony injury any of the six structures of the neural arch can fail because of the transverse fracture because there is a distraction process. What else can happen apart from this fracture the because of the ligamentus injury the facet joint capsule ligament when injured it will result in the diastasis sublegation or dislocation of the facet joint and facet joints are seen best on the sagittal or the axial images. The other ligament when the intraspinus or supraspinus ligament is disrupted that will result in the widening of the intraspinus distance how to look for intraspinus distance widening. So suppose this is the index level where you are looking at the widening what you have to do is that you have to measure the intraspinus distance above the level of the index and you have to measure the index the intraspinus distance below the level of the index and then you have to average out. So suppose this is 10 this is 12 average will be 11 so if at the index level if this is more than 11 that is the sign of the intraspinus widening and it is an indirect feature of the posterior ligamentus complex. The third type of injury which is the wedge compression injury which involves the anterior column we look for five signs which is called clerotic line parallel to the vertebral end plate so those clerotic line are seen somewhere here. Then we look at the depression or the wedging of the vertebral body seen by the loss of height we look for the deformity of the vertebral end plate and I will show you the example of it we look for discontinuity cortical step. How to look for the burst fracture burst fracture is the compression fracture of the middle column. So what you have to do for whenever there is a burst fracture the fracture line which was seen adjacent to the vertebral end plate extend to the posterior cortex so whenever fracture line extend to the posterior cortex that is the definition of the burst fracture. So this posterior cortical line once extend you can see on the sagittal image you can see on the axial image as you can see here normally the posterior cortex is very smooth and slightly concave. So when you see loss of this smooth outline or there is loss of this normal concavity sign of a burst factor when burst factor is severe you can get two other signs and that one sign is widening of the inter particular distance. How to measure inter particular distance again the same rule if suppose this is the index level you have to measure the inter particular level above it and inter particular distance below it you average it out and if at the index level same example 10 and 12 so average is 11 if at the index level your inter particular distance is more than 11 it is a sign of an inter particular distance widening that is one of the signs of a severe type of burst fracture which you will learn. And last but not least burst factor can also involve the neural arch however unlike distraction injuries in burst fracture the injury which happens in the neural arch has more vertical oriented unlike in distraction injuries where the orientation of the neural are fracture is more horizontal and we are going to see the examples of both of them as we move ahead. So this is about how to look for this injuries on a CT and now we look at in detail so four types of injury I will start from the most severe and go to the list of your vice versa. So let's start with the lead severe type of injury and that injury is called compression injury in AO classification this injury has been given grade A1 or A2. So let's see how it looks like. So what we see the several times we have to look for is dense clerotic line so you can see this nice dense clerotic line there is a depression how to look for the depression. So again same way if you look at the vertebral body height below it and if you see that the vertebral body index level is lower than the vertebral body height below it it is probably depressed so that is a depression deformity as you can see superior end plate is deformed. And you can see that there is a buckling of the cortex and there is a discontinuity of the cortex as you can see on the axial images coronal images and vaginal images. Now you have to remember that one of the characteristic feature of burst fracture of one of the characteristic feature of the compression fracture is that the fracture line does not extend to the posterior cortex. So the line stops somewhere before the posterior cortex is reached and so use a smooth posterior cortical line on the axial images is present. Let's see an example on this video. Okay, so look at this video. So what we are seeing here is this nice clerotic line there is loss of vertebral body height loss how many levels you see this clerotic line so you can see multiple level. This vertebral body is abnormal this vertebral body is abnormal this vertebral body is abnormal there is a step here there is a deformity here there is a superior end plate compression is there. However none of this place is this line is extending you can see that this line does not extend to the posterior cortex and that is the characteristic features of this compression injuries and this are described as A1 slash A2. The A2 compression injuries will have a vertical split so if you see vertical split which is coronally oriented like this that will call pincer type of fracture or A2 type of fracture. Again A2 type of fracture is relatively rare so most of the injuries what you see is A1 type of fracture. The second type of injury what we have to describe is the burst fracture. Burst fracture occurs due to axial loading and flexion in different combination and what does it do a burst fracture will result in compression of the anterior column and quite often it can result in either compression or distraction of the posterior column. So everything in the spine the morphology depends upon three things one is the vector the force vector so the force vector how much magnitude of the force vector fulcrum of the force vector and the direction of the force vector. So if the fulcrum is in the vertebral body anteriorly fulcrum is in the central part fulcrum in this in the posterior part of fulcrum is much anterior to the vertical body. With the same magnitude different morphology of the injury happens but having said that burst fracture is where the axial loading injury predominates. The burst fracture is a type of a compression fracture axial load and flexion 90% of the burst fractures occur in T9 to L5 with more than 50% occur at the thoracolumbar junction. What is the AO definition of burst fracture burst fracture is when end plate is fracture plus posterior cortex extension of the fracture is there posterior cortex can buckle can retro pulse or just do nothing. So let's see the example okay so in this example you can see that there is a wedging compression so this is a normal vertebral body and this vertebral body height is reduced. There is a cortical step and there is this fracture line which is this clerotic line so there is a type of injury compression injury. A1 and A2 if this line does not extend to the posterior cortex however in this patient that this line is extending to the posterior cortex and as I told you normally the posterior vertebral body is moved or slightly concave. However here you can see that the posterior vertebral cortex is convex button like a pregnant belly appearance and this is very characteristic feature of a burst fracture. What does AO suggest? AO suggests that you will call something as a burst fracture when end plate is involved so here in this case superior end plate is involved plus posterior cortex. So superior end plate plus extension of the fracture to the posterior cortex is enough to classify it into A3, A4. However once the fracture extend to the posterior cortex the posterior cortex may buckle, posterior cortex may fragment, posterior cortex may retro pulse lot of things will happen and that is where the severity of fracture comes into place where A3 can be differentiated from A4. When you look at the axial the burst fracture is a characteristic feature of the combination so you can see that multiple vertebral body is not only compressed there is a combination and this commuted fragments are radially displayed that's another. I showed you previously the normal posterior vertebral cortex here you can see that the posterior cortex is irregular and this is again a characteristic feature of burst fracture on axial images. Previous years when sagittal images were not available people used to rely on the axial images to diagnose nowadays we hardly look at the axial images, sagittal is everything what we need to know will tell you. So burst fracture is the fracture involving vertebral end plate plus posterior cortex and there is posterior cortex buckling and loss of smooth posterior cortex. So what are the spectrum of the burst injury so as per AOS I told you burst fracture is when either superior or inferior end plate is involved plus posterior cortex is involved. However there are other features of burst fracture as well like a compression fracture which I showed you so vertebral body shows compression variable type level of compression fracture extend to the posterior cortex which you already described. Lots of posterior vertebral body height loss so as you can see in this example on your left the posterior vertebral body height is not significantly lost. However in this example the posterior vertebral body height is significantly lost so this is where the severity of burst is coming into place and how we differentiate A3 from A4 in AO classification. Then what happens is that I told you that retropulsion of the posterior cortex or posterior cortex buckles if it's more severe there is retropulsion. Communicated fracture with centrifugal displacement I showed you all the centrifugal displacements to the best centrifugal displacement will be seen on the axial images. Neural arch can also fracture however the venereal arch is fracture it has a vertical orientation of the fracture unlike the fracture injury which has more of a horizontal orientation of the fracture. And vertebral body on coronal plant quite often split in sagittal plan so sagittal split is one of the characteristic features of axial loading not necessary burst fracture but burst fracture is a prototype of axial loading. So whenever I see sagittal split in the vertical body I know that in sagittal splitting is best seen on coronal images. So when we see the sagittal splitting of the vertical body you know that the axial loading has happened so vertical body split into two part right and left half. And last but not the least inter-particular distance is wider which I already explained you how to look for it is inter-particular distance above the level of the index below the level of the index averages out and wider. Just a practical tip it's very difficult to measure a two level and then to average out a lot of hard work. So what I do in numbers find as we know that as we go from top to bottom inter-particular distance normally wider. So if the index level inter-particular distance is wider than the vertebral level below it it is an indirect or it is one of the signs that inter-particular distance is wider. So you don't have to measure a two level and then to average out because it's not possible in a busy trauma center to go through all of this. So just look at easily the inter-particular distance at the index level the level below if it's wider than the level below it's a sign of a severe burst. So what does burst fracture? The burst fracture is end plate fracture plus posterior cortex extension. End plate fractures now we come to how to differentiate A3 from A4. So if only one end plate is involved it is A3. If both the end plates are involved it is A4 and we'll see the example. Of course it goes to the posterior cortex it goes to the combination of the fracture with centrifugal displacement. Whenever you see inter-particular distance widening and the vertical laminar fracture which I showed you they are quite often seen in severe burst and A4 type of burst. And burst fracture can also have a posterior column distraction which we are going to learn shortly. So let's see an example of how burst fracture looks like. So let's see the images as I can show you here. So you can see that in this patient there is a loss of height of this vertebral body as you can see it here. The anterior cortex has buckled here. The fracture is involving the superior end plate and the vertebral body and you can see that compared to the vertebral body above vertebral body below. Now we'll go more coronally and here you can see that this fracture line is not only extending to the posterior cortex there is a... So as I told you on sagittal images your posterior cortex should be smooth straight line or slightly concave line like this. Whenever you see this pregnant belly like buckling of this. So what I tell my resident if you see like distal radius torus fracture like fracture of the posterior cortex of the vertebrae that is the spine of a burst fracture. So this is one of the mild type of burst fracture as you can see here the inferior plate is bent. So this fracture is only involving the superior end plate. This is an example of A3 type of a burst fracture. Let's see how it looks on the coronal. So as you can see on the coronal images the fracture is involving the superior end plate fracture is involving the posterior cortex which is not very well seen. The inter-particular distance at the index level is not wider than the inter-particular distance below it and there is no vertical laminar fracture. So this is a very classic example of a mild type of burst fracture. On axial when you look at this you will see this nice smooth posterior cortex at non-fracture level compared to the at the level of fracture where you see this posterior cortex has been wagging and irregular with all this centrifugal displacement of the combinated vertebral fractures. This is another example of a more severe type of a burst fracture. You can see that there is a significant loss of vertebral body height superior end plate is involved. The fracture is extending to the posterior cortex. The posterior cortex is also broken and there is this buckling or the torus like deformity of the posterior cortex. I'm going more vertically down and now at this level you can see that the fracture is also involving the inferior cortex and the posterior vertebral body height is also lost. So what are the characteristic features of A4 type of a burst fracture in AO classification? Few findings. First of all it involves both the vertebral end plate. How to look for both vertebral end plate involvement? The best is to look on the coronal. So when you go coronal you will see that the both vertebral end plate you will see this through and through fracture here. So that is the involvement of both superior and inferior vertebral end plate. You will see that the posterior vertebral body height will be lost compared to the A3 type of burst where the posterior vertebral height is reduced or often normal or slightly reduced however here you see the significant loss of posterior vertebral body height loss. There will be a significant retropulsion and when you look at the posterior column you will see the inter-pedicular distance widening as well as the widening as well as the vertical laminar fracture. So let's see what are the signs what you saw. So this was a fracture which was extending the posterior cortex so it is at least burst, at least A3. There was retropulsion. There was this combination and axial plan with centrifugal distribution. Posterior vertebral height was lost. Then the fracture was extending the posterior cortex and then you can see that both superior and inferior end plates were involved. So burst is not a single fracture. So tillic says burst has two points and single fracture, AO says that burst is A3 and A4. But even A3 has a spectrum, even A4 has a spectrum. The burst can be said as stable versus unstable, incomplete versus complete, mild versus severe. In tillics it is just burst. In AO it's A3 and A4. And in AO the burst has a third component which is called burst with PLC plus which we will learn little bit later how to look at it. So in A3 only single end plate is involved with posterior wall. In A4 both end plate vertical laminar fracture, inter-pedicular widening. Though inter-pedicular widening and vertical laminar fractures are not the described findings in A4. So AO says that if both end plates are involved you call it A4. However, whenever there is an A4 you will invariably see vertical laminar fracture inter-pedicular widening. So let's see an example. So the example on your left shows a mild burst. How do you know that? So because fracture is extending to one end plate and posterior end plate as I said. There is some posterior height loss but not significant compared to that of the vertical about. However, you can see the severe burst both end plate and superior and inferior end plates are involved. There is a significant loss of posterior height. There is a significant retro-pulsion. When you do the coronal you will see the superior and inferior end plate extension. When you look at it you will see the widening of the inter-pedicular distance. The inter-pedicular distance at the index level is wider than the level below. It is a sign of a widening and then you see this vertical laminar fracture which is a sign of an A4. So now we are clear how to differentiate A3 from A4. So burst again has multiple phases single versus both vertical end plate, posterior vertebral height loss variable, more retro-pulsion, more combination, posterior column involvement inter-pedicular widening. So this is what is described as vertical laminar fracture. It is one of the characteristic features of the burst. What does it signify? It suggests that this burst fracture is severe. There is a possibility of a dural tear because this dura might pinch inside this fracture. However, you have to remember that whenever you see this vertical laminar fracture, don't call this burst fracture as a three column fracture. It doesn't make it a three column. Three column fractures are the more severe fracture in terms of instability. However, in this patient with vertical laminar fracture, the posterior column has failed in compression. When posterior column fails in the distraction when the tensile failure occurs, that is the time you call it a three column fracture. However, this becomes more of a three column injury but it is not as unstable injury as we will learn in the three column injury. So this does not optimize the lot of reports of radiology different places where they say that burst fracture with posterior column fracture. So it's a three column, very highly unstable injury, which is a wrong way of putting it in. Burst fractures are operated primarily not because they are unstable, primarily because they cause neurological instability and we'll learn a little bit later on in our session. So what to report when there is a burst fracture? First of all, call it a burst fracture, at least a three, how to call it and place the posterior cortex. Then you describe how committed the fracture is, how retro-pulsed the posterior cortex is, how much is the central canal compromised, how much fragments are displaced, whether the fragments are rotated or not. And we'll just see an example of reverse particle sign and what is happening to the posterior ligamentus complex. So this is what is called reverse particle sign. And what has happened is that this fragment has, so this is an A4 type of burst fracture and this fragment has gone inside the spinal canal called significant spinal canal stenosis. However, this fragment has rotated 180 degrees. So the cortex in the front, which should be on the posterior part and the trabicular bone is behind. So this is the sign of a reverse particle sign, extremely important sign to mention in a burst fracture. It suggests posterior ligamentus disruption, PLL, posterior longitudinal ligament disruption. This patient needs to be approached by the anterior approach, decompression, corpectomy needs to be done and Cajun graft needs to be put in this patient, unlike the other birth fracture which can potentially be treated from the posterior approach as well. Again, we will leave this to the spine trauma team how to do that. Okay, look at this, this is how the fracture is retro-pulsed, in retro-pulsed, but the posterior cortex is still posterior. So you can see that the posterior cortex is still posterior, this is normal. However, here you can see that the posterior cortex what you see this Zagat margin and the, here is the cortex. So this is called reverse. So this will flip 180 degrees, a very important sign to describe in your report about reverse particle sign. It is a lot of surgical implications. Burst can also occur with posterior column distraction. So far I showed you vertical laminar fracture which was an injury of the compression injury. However, burst can also have a posterior ligament complex injury as you can see here, anteriorly birth, but posteriorly you can see that if that's a joint thervide and there's a transverse fracture through the spinal process. So this are the hybrid type of birth and that we will learn more in the fracture dislocation, in the fracture distraction, the chance type of fracture. So what have we learned about burst? Burst is not a single type of fracture at till expansion. Burst is a heterogeneous group of injuries. Even AO could not categorize into more than two types because A3 is a spectrum, A4 is a spectrum. Burst is commonly considered as a mechanically unstable. However, it's not always the case. Burst is treated not because it's unstable, but primarily because it causes the neural spinal canal compromise. And there is another classification for burst fracture which is important. If you are working with a lot of spine trauma people, you should be learning about this load sharing form which we are not going to discuss today. And central canal compromise is a dynamic process and not a static process. Our bursts are managed. So the burst can be divided basically into two types. Burst with neurology, they are biologically treated. Our burst without neurology, A4, severe A4 are treated surgically quite often. A3 are often treated non-surgically. A4 with reverse particle sign is invariably treated surgically with the anterior approach. When there is a significant spinal canal compromise, some surgeons treat this even without neurology. A4 with B injury, any posterior ligament complex distraction are unstable, fine and those patients are treated surgically. And typhosis or progressive typhosis on follow-up imaging these patients are treated. So these are the signs which I described. These signs are the signs of mechanical instability while neurological whenever it's present they need to be. So what is the important thing to learn that each injury morphology is not black and white. It is a spectrum of injury and spectrum of severity. A3 is a spectrum, A4 is a spectrum. Describe them rather than just giving them a name. So give them a name at the end but describe them well in the body of your report. The third type of injury which is now we are moving to the more unstable injury which is called a flexion distraction injury which are given B1 and B2 in the AO classification. So basically distraction injury will separate the final column vertically so bones or ligaments will move away from each other tearing them apart. As I told you because of the biomechanics most of the time the tension failure occurs in the posterior compartment and quite often this posterior compartment tension failure is associated with the compression injury of the anterior compartment. So what you will see is anterior compartment has A type of injury and posterior compartment has B type of injury and we are going to see it. So flexion distraction are called chance or chance like fractures, C to B fracture, posterior column fails in distraction, anterior middle column fails in flexion. So there is a difference of chance or chance like fracture occurs at thoracolumbar junction and almost one-third to one-half of the fractures have associated intra-abdominal injury. Now you have to remember that the chance described this fracture in 1948 much before the CT and his paper in British Journal of Radiology is consist of one and half page. Only three injuries and he said that this are the pure bony injuries however there were no CT scan or MRI available to say that what he told was actually bony injury or ligaments injury. Because quite often in real life we see very rarely pure bony chance which are B1 injuries. So majority of real life chance injuries are B2 injuries which are ligamentous injury or mixed injury and that is why they are called chance like fractures or chance variance. So posterior tension bed failure which is the AO type B can occur to the bone which is a transverse fracture of the posterior element which is called B1 or it apples to the ligament which is called B2 or it involves both bones and ligament in which case is also called B2. So either pure ligamentous or bony plus ligamentous is called B2 while pure OCS injuries are called B1 which are extremely rare or relatively rare. There is one M1 modifier in AO classification and same way there is a modifier in T-Leaks as well where we are not sure even after doing a CT even after doing an MR if you are not sure whether the PLC is injured or not you call it indeterminate PLC or M1 modifier so just put M1. We'll learn how to do that. And injury can be wedging or burst any type of A1, A2, A3 or A4. So posterior tension bend injury when there is a bony chance CT is better than MR. For ligamentous chance my personal preference I prefer to look at the CT for ligamentous injury and we will see how to look on the CT for ligamentous injury. MRI you can directly see the ligament however quite often you see edema which makes it indeterminate. So my personal preference is CT is better than MRI in describing the ligamentous injury of the posterior ligamentous complex. MRI will overestimate the ligamentous injury so the edema is not equivalent to ligamentous disruption. So B1 the bony is monopregmental injury it involves single segment B2 is mixed or ligamentous injury is involved to adjacent segment and anterior posterior injuries can at a different level. So how to look for this? So on fractures you have to look for horizontal fractures of the neural arch. For ligament what are the signs of the posterior ligamentous complex injury? If you see a local kyphosis more than 40 if you see regional kyphosis more than 25. Pessage joint diastasis is double edging location increase intraspinus distance or if you see MRI edema fluid and dyspentry let's see all of this one by one. So first of all how to measure the regional kyphosis? So regional kyphosis is measured if this is the index vertebrae you go to the one vertebral level above superior end plate and one vertebral level below inferior end plate and you measure the angle between these two which is called cobs angle. If this cobs angle is more than 25 it is an indirect evidence that this can happen only if the posterior ligament are distracted. Let's see the example. So you can see that there is a significant the regional kyphotic angle is more than 25 degree. So even if this looks like a burst this happens only when the posterior ligaments are distracted and there is a PLC injury. Same way you can see that there is a vertebral body height loss or vertebral body height loss of more than 40% in a patient with normal bone density. So I think this is very very important thing to know that all of the signs are useful when the bone density is normal. So these rules do not apply to osteoporotic compression fractures in which you can have a much worse kyphotic angle with preserved posterior complex or much worse loss of height with preserved posterior complex. However in young patients with MVC if you will see the local kyphotic angle regional kyphotic angle of more than 25 or if you see the vertebral body height loss of more than 40 degrees that is a sign of a posterior ligament complex indirect injury. This is the local kyphotic angle how to measure it from the superior vertebral end plate to inferior vertebral end plate. If this angle is more than 40 degrees that is a sign of posterior ligament complex. Look at some of the signs what are the other signs we look at for the inter spinous distance widening again inter spinous distance at the index level is wider than the average of the above and below. And same way if you see any horizontal fracture of the neural arch as you can see in this patient horizontal fracture of the parz intraarticularies horizontal fracture through the lamina horizontal fracture into the the spinous process and widening of the inter spinous ligament. Pessage joint dialysis as you can see in this patient is a sign of Pessage Joint Publicization is a sign Pessage Joint Dislocation is a sign of this and any horizontal fracture to the posterior column is a sign of a posterior ligamentous injury. So when you are reporting what to report first of all mention whether it's the bony with the single level or B2 mixed with adjacent level CT the fracture you look for the fracture and the displacement MRI you look for edema fluid or discontinuity if you are not sure at M1. And always describe the vertebral body wedging or burst described separately in A081 to A4 and we'll see some examples. So let me two examples of in this patient. So what's happening in this patient as you can see here. This patient has a significant loss of vertebral body height anterior vertebral body height lost is more than 40% if I measure a kyphotic angle it will be more than 25 degree that is a sign of a posterior column destruction. You can see this superior vertebral end plate has a fracture which is extended to the posterior cortex so that will make it A3 which is this vertebral body this vertebral body is L1 so you describe L1 and A3 so that means L1 vertebral body has A3 type of a fracture. You go behind what you see here you can see that there is a significant widening of the inter spinal distance. What you do next you go and you can see that there is a transfer fracture through the pedicle and the posterior element. So there is a B1 component, bony component, there is a ligamentus component, so it's a mixed component it will go to B2. Let's look at the coronal what's happening in the coronal anteriorly you will see that there is a A3 type of a fracture of the of the of the vertebral body and as you go behind you can see transverse fracture through the pedicle lamina and there is a distraction and there is an inter spinous widening. This level is called the T12L1 so what you write in AO classification you write T12L1 P2 and then you say L1A3 so this is how the final report of you will look like if you are losing a AO classification otherwise you will just say that there is a distraction injury at T12L1 with bony and ligamentus component and there is the first fracture predominantly involving the superior end plate without significant retropulsion. So just to provide the first fracture whatever way it works with your fine surgeons if they are using AO classification this is what you write. So B2 fracture is always adjacent level B1 fracture or A fracture is monoostotic single level I hope this is clear. So again look at the same example inter spinous widening, transverse fracture through posterior column, transverse fracture through the posterior column, anterior there is a significant loss of height, kyphotic angle is more than 25, again transverse fracture through the posterior column and the coronal transverse fracture through the posterior column transverse fracture and widening with inter spinous system. So that is what you say so if injury morphology has a spectrum of severity and goal is to describe them rather than to name them and remember that you can have more than one type of injury present. So reporting tips is that injury morphology are often mixed more than one injury morphology is quite frequent when there are combined mechanisms each injury should be classified separately with more severe injury return first. So in the previous case B is more severe than the A so write about the B first and then the A if multiple level of injuries are involved different level each level injury is assessed independently and separately. And T-lix so in T-lix if more than one injury is present the single injury with the largest score is used but in previous patient what you will say distraction injury and PLC plus okay so three point for distraction injury and three points for PLC plus six points in AO you will write exactly what we say T12 L1 B2 and then T and L1 as A3 so that is what you do in the AO. So this is another example probably not go through it is a very similar example what I showed you last type of fracture pattern is fracture dislocation or the translation type of injury which is the most severe injury. It is described as AO type P and in T-lix also it is described as one of the worst injury what happens the one vertebral level vertebrae entirely as a collar move in front of the other. So you can see that there is a translation of this vertical body over the anterior translation of more than 50% here so this is the fracture dislocation P type of fracture on sagittal plan. Here there is a coronal plan translation and here there is an axial plan translation so these are the different types of translation injuries some of the most severe type of injury. What are the other features which will always be there in fracture dislocation so you will have either a facet joint dislocation or path fracture or facet articulate facet fracture posterior column quite often distracted and ALL and PLL have quite often the stripping type of injury so all of these are one of the severe most type of injury you will see in your day to day life so there is a path fracture or all the superior and facet fracture and ALL and PLL stripping or the aversion injuries are there. Multilegamentals, multi-segmental it's a very severe injury most of these patients have a severe neurology as well. Now my residents quite often like I tell them that translation pitfall is not so don't mistake the retropulsion with the translation. In this example the vertebral body is fractured and it is moving back style so it looks like this vertebral body has moved in front of this vertebral body so quite often when you start interpreting you call it entrolysis of 5, 4, 3, 2, 1, L, T12 over L1. However if you ignore the injured vertebra and draw the smooth curve you can see that the T12 and L2 vertebral body are normally aligned. And only the L1 vertebral body has retro pulsed so this is retropulsion which is not equivalent to translation retropulsion is less severe injury compared to translation. In translation what should happen ignore the vertebral body which is injured draw a line below the injured vertebral body and draw a line above the injured vertebral body and see whether the spinal column above the injured and below the injured ignoring the injured vertebral body are aligned or not then that is the sign of a translation injury. So retropulsion is not retrol excessive quite often when retropulsion is there it looks like this vertebral body has moved in front of others but that is not the case. So when to do an MRI, MRI is done with any spine trauma who has a positive neurology. In the absence of neurology when do we do MRI, translation injuries which is very unlikely because translation injuries will invariably have a neurology. If you see any distraction injury on CT we invariably do MRI so both B1 and B2. When you see severe compression injury A4 we usually do the MRI to upgrade it to the PLC which will be B grade and all patients who are going for surgery we invariably do PR study we invariably do the MRI. What we look for an MRI we look for the spinal canal the spinal canal should have the nose and the CSF anything other than that so if you see the bone inside the spinal canal if you see blood in that inside the spinal canal that's abnormal. Product cord or nerve root compress is abnormal if cord is compressed and it shows abnormal signal that's also abnormal. We look for the ligaments on the spine MRI and ligaments can have edema discontinuity of fluid and as I told you that the CT is far better than MR looking for the bony injury it is quite good for ligamentous injury as well. And presence of edema is not equivalent to ligament injury so MRI quite often does not contribute that much or MRI quite overestimates the injury. And so you have to take the MRI finding the pinches on and MRI can show you that it's injury so look at the example so this is a nice example of normal posterior ligament complex so this is very useful MRI. If you are not sure on the CT or PLC and you do an MRI MRI shows this jet black type of posterior ligament is complex I'm very sure that this ligaments are normal. If I see edema on the posterior ligament it doesn't take me anywhere it goes to the indeterminate. In TILIX I say 0.22 point that's indeterminate in AO I say M1 modifier indeterminate. If I see fluid that is a sign that this ligament is injured if I don't see a ligament where I should be seeing it's a sign of an injury that makes it a ligamentous injury. You can see that multi ligamentous injury in this translation type of fracture with this injury as well. So I think approach to MRI in a spine injury is a different topic altogether and probably hopefully sometime later we'll do a separate session on how to approach a systematic search pattern of MRI in spine trauma. But today my main concern was CT scan and that is what we did. So what we do at the end of your presentation my presentation. CT look for it first look for the sagittal coronal axial plan for list thesis. If the list thesis is present it's a type C fracture fracture dislocation. If alignment is normal look for the posterior column distraction present then it's B type of fracture decide whether B1 or B2. No distraction look for the retropulsion or the involvement of the posterior cortex. If it's present it will make it burst which is A3, A4 and if it's absent it makes it A1, A2. The take-home points are systematic search pattern and checklist based approach to depict, describe and differentiate different type of fracture. Each morphology has a spectrum of severity. Describe it well before you name it. Understand that which CT features will predict PLC injuries including typhosis including vertebral body height loss including the posterior neural large fractures and the widening of the distances. Understand when to use CT. CT is used pretty much in every high velocity injury patients. As a first-line imaging MRI use when there is a neurology, neurologically patient is unstable when the legaments are expected to be injured or as a problem solver. Radiographs are used as a screening in low-risk patients low-velocity injury and they are used quite often as a post-op follow-up to look for the worsening of the typhosis. I recommend all of you to go through my paper, our paper in 2016 about thoracolumbar spine injury and all of these principles are described there well and I would be happy to take the questions. Thank you so much. Thank you so much Dr. Reniga for that awesome lecture. Appreciate it so much. We will open the floor to questions now so if you've got those please place them in that Q&A feature. Do you have CT examples of fractures? I think I have already shown the examples of fractures, right? Okay, excellent. Thank you. Well, I don't see much of the presentation. So a lot of compliments. Yeah, they're just compliments. Okay. Okay, so there's one question. No history or prior images. Can you share features to differentiate acute versus chronic compression fractures? No MRI available? Well, this was honestly not the goal of my presentation so I did not describe it so well but there are well described features to differentiate acute for chronic compression fractures but most of those fractures occur in osteoporotic setting, low velocity, low risk type of patients. So we start with X-rays and then on X-ray we look for the sharp definition of the vertebral end plates. I see all the vertebral end plates really clearly. Usually those are the chronic fractures. If you are not sure MRI is something which is a problem solver in this type of patient. So quite often if patients have acute pain and fall and if I'm not sure. So when I look at the radiographs I describe my findings in three ways. Sometimes I'm quite sure this is a remote or old fracture. Sometimes I'm quite sure this is an acute fracture and sometimes I'm not sure. I'll just call it indeterminate and we do in MRI. Yeah, thank you Swaroop. Okay, no history, no prize. Okay, fine. So I think I'm just looking at them. Okay, a disc spondylitis. How can we diagnose it? Well, again, this was not for spondylitis or the disc infection. So probably we'll keep it some other day. Why T-Lix gives three points to translation if it's more severe than the despair? Yeah, I think they are a little bit, I completely agree. So T-Lix has added that additional injury morphology which they call it rotation. And this translation and rotations are not very easy to differentiate on morphology. And that is where T-Lix has poor inter and intra-observer reliability. So T-Lix has this problem particularly in this point three and point four, which to call translation and which to call rotation and they say rotation is worse than translation. However, the AO has removed that part completely and as we now know that most of the translation have rotation component. So quite often you have compression injuries which are A type of injury, distraction injuries which are B type of injury and then you have translation rotation. So that's where AO made it a little simplified to make it slightly better, reliable classification. But I completely agree with you. I struggled to put three versus four when to call it rotation and made to call it a translation. I am with you like so that's the problem with the T-Lix. Would Kaifo Plasti or Vartio Plasti be advised in patients having such injuries or cruises? Well, that's a very good question. And the people have tried using Kaifo Plasti and Vartio Plasti in some of the mild birth fracture with pain and some of the even severe birth fracture also. But as far as it is still more of an experimental majority of the centers still do some form of spinal instrumentation. If at all, surgical intervention needs to be done and majority of the center still uses the posterior instrumentation with or without fusion. And sometimes they use anterior or mixed type of it, but I agree with you. People have started doing Kaifo Plasti for even traumatic compression fractures as well. Yes, but it's still not the literature is not in a huge quantity or probably I haven't come across, but I agree with you that the people have started doing that. Causes of stir hyperintensity. Okay. How to differentiate causes of stir hyperintensity and end plate due to modic changes of fracture. Well, that is so quite often the anterior end plate practice. I'm very sure on the CT scan and it will be a bit of a challenge to differentiate if the patient had modic type one changes. And at the same time trauma to differentiate it confidently all the time. Having said that the modic type changes occurs more in the central end plate with the anterior cortex and the superior end plate anteriorly posterior intact. If the CT scan shows the fracture which involves the anterior corner or end to superior corner. Those are more likely to be related to the fractures. So I told you density, this depression, discontinuity, all those five days. If those five days are there probably that is the sign that this was a compression factor. And but honestly, I haven't come across a patient who had a modic type one change and fracture at the same level and we had this issue to differentiate. Posterior tension band, can you please repeat the component anatomy wise and where it is relevant. So the tension band has two component one is called posterior tension band, which is everything behind the posterior ligamentus injury posterior tension posterior ligamentus complex posterior leg up longitudinal ligament. So posterior tension band has two component the bony component which is a neural arch, which includes pedicle, parcentral articular is superior articular facet inferior articular facet lamina and final processes and transverse processes. Neural arch plus posterior longitudinal posterior ligament complex PLC together makes a posterior tension band. So this ligaments include facet joint capsule inter spinous ligament supra spinous ligament and the the ligamentum flavor. So this four ligament and this seven neural arch component together 11 things together makes a posterior tension band. The posterior tension band is important because because of the spine biomechanics quite often it happens that the anterior column fails in compression while the posterior column opens up in distraction. And so when posterior tension band is injured they are described as type B injuries in AO. And those are the severe unstable injuries and quite often this patient undergoes a surgical intervention. Whether you call it retrolysis or entrolysis that's a good question. So spine is the only place where we describe the movement of the proximal spine in relation to the distal spine. I don't call so if a spine has if L3 has more in front of L4 I call it entrolysis of L3 over L4 rather than retrolysis of L4 over L3. So unlike rest of the extremities so in extremity factors and dislocation the displacement of the distal part is described in relation to the proximal part. However traditionally in spine the displacement of the proximal part is described in relation to the distal part. That's number one. When a single vertebral body is collapsed and moves inside the spinal column I don't call it retrolysis I call it retropulsion. So that's just the word to describe it but when I say retropulsion I know that I'm describing just the movement of the injured vertebral body rather than the movement of the entire spine. So retrolysis and entrolysis is when the entire spinal column moves in relation to the spinal column below. While if only injured level is moving we call it retropulsion that makes it easier and at the end of the day you have to talk with your spine surgeons and what their understanding is and try to tailor or report based on their understanding and you try to make sure that what you understand is exactly what you understand. When you call it retropulsion. Okay. Okay. Thank you. Oh, thank you. Do you mention the percentage of vertebral body height loss and compression factor? Yes, we do. So how do we do it? The anterior vertebral height loss, what I do is that anterior vertebral height loss at the index level compared to the anterior vertebral height level above, below and average. So for example, if the level above is 20, level below is 30, average of both of them is 25. And if my index level is supposed 10, so 10 in a percentage of 25 is whatever percentage loss of height I just calculated. Sometimes with eyeballing, as I told you in a busy trauma center, you may not have time to look at this. So you basically know what constitute around 40%. So basically anything you describe above 40% doesn't make a big sense. So two things to look for. First is whether the bone density is normal or not. If bone density is normal, any vertebral body height loss more than 40% is slightly less than half. Like slightly less than half, more than 40% is a time that the posterior column must be distracted. So that means that when anterior vertebral body compressed, you will imply that most likely the posterior ligament complex is distracted or injured and there is a tensile failure. We do that in our report. With continuity to above question list, this is always described above with the vertebra. But if the index fracture body is considered a nomenclature would change. So yes, as I told you, we say retro pulsion, not to create confusion with retro list, this is our entrolus. And how do you differentiate between PLL disruption versus PLL lifting? No, okay. So that's a very good question. Other than fracture dislocation, PLLs are very uncommonly disrupted ligaments. They are one of the very strong ligaments. Most of the time PLL has a stripping from the vertebral body. So as I told you that MRI search pattern is a different topic altogether and today I did not have enough time to concentrate on what to look for an MRI. But hopefully we'll do it sometime later. However, having said that majority of the patient with anterior compression injury, you will see that the PLL view will see in continuity. But that is stripped off from the posterior vertebral cortex, except for the translation injuries where you will see that there is a discontinuity of the PLL. The second thing is I told you about the reverse cortical sign which I described in the birth factor. And they say that when you see that reverse cortical sign, that's an indirect evidence of PLL discontinuity. So that's a very important sign to describe. And quite often you will not see this PLL discontinuity even on MRI. For reverse cortical sign is the only sign which will be present, which will tell you that there is possible PLL disruption. Okay, in your system, the gold standard for classification? Well, that's a very good question. Unfortunately, none of the classification is better than the other classification system. It all depends upon how you unify your language and communicate your finding to your surgeon. So at the end of the day, you have to understand how much your surgeons understand this classification. So if your surgeon is using a particular classification, for example, T-leaf or AO, then you try to use those classification systems. Having said that more and more people are moving towards using AO T-leaf. So as I told you, 2013 modification of AO, which is given by the same group which gave the T-leaf in 2005. So this 2013, it is called AO T-leaf classification. And I think that is probably currently available classification system. It is the best available system. However, it all depends upon so many places in North America, they have started using AO system. The hospital where I work, they don't use the AO classification. So I try to describe my findings based on if this was an AO classification, how I would have described that without ultimately giving that numbers like P-12, L-1, B-2 and then D-L-1, B-3 and A-3 and things like that. I don't give those numbers, but then I put in description what exactly that mean by putting it. So places where they use the AO classification system in structured report and impression. At the impression, they just put like this T-12, L-1, B-2, L-1, A-3 and that's it, everyone understand. And then if there is a modifier, they put M-1. So the spine surgeons understand, but if your trauma surgeons do not use it, they are not using it, then probably better not to give them these numbers and don't confuse them. Then in that case, give them more description, fit with them and tell them what they are looking for and try to answer this question. And putting it simply, injury of PLC is a distraction, absolutely. This is exactly the simplest way of putting it is that injury of PLC is distraction injury. Our distraction injury has three components. One is pure bony, which used to be called chants, bony plus ligamentus, which is mixed or pure ligamentus, which is B-2. So pure ligamentus B-2 and bone plus ligamentus B-2 are called the distraction injury or the PLC injury or the tension band failure. All of these are synonyms. Having said that, I must tell you that B-1 injury is what chants describe, which we are not sure whether he actually described B-1 or not. But we are presuming that he described B-1 based on the x-rays available that time and only three patients. So we say that in our real life, I hardly ever see a B-1 fracture. All of my B-1 fractures are actually B-2 fractures. So they always have ligamentus component, very rarely pure B-1 fracture. But what you are understanding is correct, but it can have a bony component also. Okay, thank you Yasir. Thank you. Retro-pulsion on cranial epidural sec. How you assess the prognosis? Well, again, as I told you that retro-pulsion, you have to say how much is the retro-pulsion and what this retro-pulsion is causing to the spinal canal. So what you have to say that while moderate figure, if you can arbitrarily divide that retro-pulsion or you say that retro-pulsion with spinal canal compromise less than 50% or more than 50% or you say that minimum spinal canal AP diameter is this much. So either you put it, either you put it at percentage based on the spinal canal diameter level above and level below, or you say that spinal canal diameter is reduced by approximately this much percentage, or you say that the minimum spinal canal diameter at the level of the worst retro-pulsion is this much. Now, at this point, I must tell you that retro-pulsion what you see in image is not the actual retro-pulsion which happened at the time of trauma. The actual retro-pulsion which happened at the time of trauma is quite often much worse than what you see on images. And then there is an elastic recoil of the tissues and this retro-pulse fragment comes back, they recede. And so the retro-pulsion what you see on images quite often underestimates the actual retro-pulsion which you will see on, which happened at the time of the fracture. So you will see that some patients have mild retro-pulsion and those patients have neurology positive and some patients have moderate to severe retro-pulsion without neurology. Simply because retro-pulsion what you see is not a static but it's a dynamic and we will never be able to tell how much was the retro-pulsion which happened at the time of injury before the elastic recoil of the tissues take in. Yeah, thank you. So, yeah, I think, okay, there's one more. Could you please explain how to measure the percentage of height loss in multi-level adjacent compression fracture in trauma for each level should we use the average? Yes, so that that's a bit of a problem. So what we are trying to do is that if you have a multiple contiguous level fractures which are involved in that case the height loss measurement will be a bit of a challenge. In which case you have two things what you can do is you can go one level above the level. So like suppose if three contiguous levels are involved then you go one level above the three levels and one level below that three levels. So suppose L12 and three are involved you go to T12 and L4 and try to figure out what is the percentage loss height of L1, L2 and L3. It's a bit of a erroneous result but those cases are not one of the straightforward cases. But having said that these things happen quite often that compression fractures occur at multiple adjacent levels. However the eyeballing is sometimes quite useful and you will know that what constitutes 40% and what doesn't. Now having said all of these things let me tell you one thing the height loss was more important when the CT was not there. The height loss was primarily described for plane radiographs. So once CT came you are going to see the indirect evidence of the posterior ligament complex injuries like fractures or widening of the interpinus ligament or the widening of the facet joint capsule or other findings. So in that case height loss is not that much of a problem this was main of an issue in radiographs. We use primarily height loss when we are describing the radiographs rather than the CT because CT are going to see the indirect evidence of the direct evidence of the height loss or the typhotic deformity which is the posterior ligament complex. Dr. Rinnig I think you got them all. Yeah, transaction can be accessed by CT no we cannot assess the transaction by CT MR needs to be done. Yeah, thank you. So we are almost there. Thank you so much. Thank you. Thank you Ashley. Yeah, thank you. Thank you for the lecture and for being so gracious with your time answering those questions. We appreciate it. Thank you. The learners appreciate it. Thank you. Thank you. And for everyone else. Yeah, yeah, you can stop sharing for everyone else participating. Thank you so much for all your fantastic questions and for being here. Thanks for the access and recording of today's conference and all our previous new conferences by creating a free MRI online account. You'll also receive a recording of this in your email if you registered for today's new conference. Be sure to join us next week on Thursday, March 28 at 12pm Eastern where Dr. Attis Zahir will deliver a lecture entitled cystic lesions of the pancreas. You can register for that at MRI online calm. 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