thanks for tuning in please like subscribe and check out my instagram for cool science and not science stuff welcome back to anatomy and physiology on catalyst university my name is kevin tokoff please make sure to like this video and subscribe to my channel for future videos and notifications in this video we're going to be discussing the biomechanics of lateral flexion and rotation in the cervical spine and if you want the more basic movements of flexion and extension go back and watch the previous video we'll start off by talking about lateral flexion which is often called side bending now of course lateral flexion is named based on which side you're bending toward so in this picture we're looking at a posterior view of a person's neck and this person is bending to the right again they're putting their right ear in the direction of their right shoulder so this would be right side bending or right lateral flexion now when we start thinking about the biomechanics of this movement it's really more helpful to think about the movements of the lower cervical spine remember from a previous video that the upper cervical spine is really just defined as these upper two joints the lino occipital joint so between the occiput or c0 and the atlas c1 and the linoaxial joint which is between the atlas and the axis or c2 everything below that so basically from the c2 c3 segment down to the c7 t1 segment or some people will actually just say c6 c7 and not count this segment but basically when we start talking about lateral flexion and rotation it's more helpful to think about the biomechanics first with the lower cervical spine so between segments c2 c3 down through maybe c6 c7 okay now when we laterally flex to the right notice what's happening here on either side the left side and the right side of the cervical spine which side has more space or becomes longer well the left side in this case becomes longer if you actually look at this distance from here to here it's longer on the right side so the side that you're bending toward it becomes shorter and you should be able to see that with the distance here okay so the left side is getting longer and becoming more open and the right side is becoming smaller and more closed and so you can imagine what that's going to do with the set joints and with up sloping and down sloping so let's first consider the ipsilateral side now in this example of laterally flexing to the right that's our right side but we're going to generalize it by saying the ipsilateral side so if you think about what's happening with these facet joints they're down sloping now in general they're going more into their close pack position because these set joints are coming closer and closer together right so they're down sloping and remember what down sloping means it means that the vertebra above so the superior vertebra moves inferiorly and posteriorly relative to the vertebra below so for example if we consider the c3 c4 segment on the right side where we have down sloping c3 is actually gliding a little bit inferiorly and posteriorly relative to c4 and this throughout this entire segment leads to some effects for example on the right side again the facet joints are going more into a closed pack position but also those intervertebral foramina or neural foraminas are often called get narrower so there's less space for the spinal nerve roots to come out and so if you have an individual potentially with a radiculopathy where the nerve roots compressed on the right side they may not like to go into right lateral flexion because those intervertebral foramina are becoming more closed leaving less space for the nerve root now on the contralateral sides in this case the left but generally contralateral we're getting up sloping and there's more space here so those facet joints are becoming farther apart for up sloping it's where the superior vertebra moves both superiorly and anteriorly relative to the vertebra below so for example the c3c4 segment we would say that for up sloping c3 glides superiorly and anteriorly relative to c4 and again with the combined upsloping on this side we see a bunch of different effects those facet joints become more in their in their open pack position and the intervertebral foramina are going to gap they're going to become larger more space for that nerve root so for example if an individual has a radiculopathy or where nerve roots compressed on the left side they may actually like right lateral flexion because it opens the left side so we can basically say a general statement here for this example if we bend the head to the right it causes right down sloping and left up sloping or even more generally when we go into lateral flexion or side bending it causes ipsilateral down sloping and contralateral up sloping now what's important to understand here about the lower cervical spine c23 and down is that when we laterally flex to the right we're also going to get a little bit of cervical rotation to the right so lateral flexion and rotation you really can't have one without the other okay if i laterally flex to the right as i'm doing here i'm going to get a little bit of rotation to the right now the reason this occurs in the lower cervical spine where we have right lateral flexion and a little bit of right rotation is because in the lower c-spine we have what's called type 2 mechanics in type 2 mechanics lateral flexion and rotation occur in the same direction okay that's what we see in the lower cervical spine here's a short explanation as to why when we have lateral flexion we can't help but have a little bit of rotation to the same side and by that logic we're talking about the lower cervical spine and this explanation actually works for any region of the spine that follows type 2 mechanics doesn't work for type 1 works for type 2 but luckily that's most of the spine so for this explanation i've got these books right here these each represent a vertebra so this one right here in green this biochemistry textbook this one is the inferior vertebra this one p450 the black book is the superior vertebra now obviously i can flex i can extend i can do a lot of things here okay this is the left side this is the right side and over here is anterior which means closer to me is posterior now we're going to talk about lateral flexion first and let's consider a lateral flexion or side bending to the right side okay so that would look something like this if we're looking at the osteokinematic movement but here we're going to neglect the actual side bending and just talk about the upsloping and down sloping because that explains it okay so if we side bend to the right what did we say happens on the ipsilateral side which in this case would be the right side we have down sloping also on the contralateral side so that would be the left side we have up sloping so upsloping on the left in this example down sloping on the right in this example so what is downsloping remember downsloping is inferior and posterior glide of the superior vertebra relative to the vertebra below so if this gets a little bit of posterior inferior glide really just consider that posterior part this right side is going to glide a little bit posteriorly you may already be able to see where this is going the left side has up sloping when i laterally flex to the right contralateral up sloping so up sloping is anterior superior glide of the superior vertebra relative to the vertebra below so if we have that anterior superior glide focus on the anterior this glides a little bit anterior we'll look at that the superior vertebra just rotated relative to the vertebrae below that's why when we laterally flex to one side we can't help but have rotation that follows it to the same side assuming we've got type 2 mechanics and that has to do with those arthrokinematic movements but really on an anatomical level it has to do with the orientation of the facet joints when we start talking about the upper cervical spine that has type 1 mechanics this is where lateral flexion and rotation occur in opposite directions the way to remember type 1 versus type 2 mechanics is type 1 one is an odd number so that means that lateral flexion and rotation are at odds with one another so they're in opposite directions type two is even number so again same direction so coming back here in the upper cervical spine if i laterally flex to the right there's actually going to be left rotation and again that's just in those upper two segments at the atlanta occipital joint and eleno axial joint okay so type 1 mechanics in the upper c-spine means that lateral flexion is associated with contralateral rotation now before we go any further let's look at the range of motion of lateral flexion up here i've had is about 35 to 40 degrees you can see that in the table down here side bending 35 to 40 degrees the vast majority of the contribution to lateral flexion range of motion is from the lower cervical spine it contributes 30 to 35 degrees of that notice at the atlanta axial joint so c1 c2 there is no side bending that occurs and then the atlanta occipital joint between the occiput and c1 that contributes 5 degrees of that lateral flexion but none occurs at the aleno axial joint now let's talk about rotation so again it's more helpful to think about the movements of the lower cervical spine so let's take a look at this this individual is rotating their neck to the right again think about it just which direction you're turning towards so this is right rotation the ipsilateral side is going to undergo down sloping and the contralateral side is going to undergo up sloping what that means is if a person rotates their head to the right so cervical rotation to the right the right side down slopes and the left side up slopes so let's consider the ipsilateral facet joints first they're going to downslope so that means on the with this person rotating to the right the right side downslopes this is going to be superior vertebra moving inferiorly and posteriorly on the vertebra below so in other words if we consider that c3c4 example on the right side or ipsilateral side here that means c3 is going to glide both inferiorly and posteriorly relative to c4 okay now because there's down sloping on the ipsilateral side here in the lower c spine that means that the facet joints are going to close or they're going to become more into their close pack position and also those intervertebral foramina are going to be narrower so if a person has a radiculopathy a compressed nerve root on the right side they're not going to want to rotate their neck to the right because again if we think about rotation to the right that closes or narrows the intervertebral foramina here so there'd be less space for the nerve root causing more irritation potentially all right now on the left side here or generally contralateral side the facet joints upslope in the lower cervical spine so we have the superior vertebra moving superiorly and anteriorly again if a person had a radiculopathy or compressed nerve root on the left side they may actually like right rotation because on the left side during right rotation these intervertebral foramina are going to open up and that's because we have that up sloping so maybe c3 would glide both superiorly and anteriorly relative to c4 that creates more space there in the intervertebral foramina and more space for the nerve root okay so think about those biomechanical factors now in this example rotating the head to the right causes right down sloping and left up sloping but again we can make a blanket statement here that when you rotate your head so cervical rotation you get ipsilateral down sloping contralateral up sloping and again in the lower cervical spine it follows type 2 mechanics so lateral flexion and rotation are going to occur in the same direction okay so with right rotation we can't help but get a little bit of right lateral flexion okay just like back here we couldn't have lateral flexion without a little rotation here we can't have rotation without a little bit of lateral flexion and in the lower c-spine they occur in the same direction so if this person rotated their head to the left we'd get a little bit of left lateral flexion let's do another explanation here of why when we do rotation of the lower cervical spine we also have lateral flexion to the same side again as before this is going to have to do with those arthrokinematic movements the up sloping and down sloping okay so again this black book right here i've got my superior vertebra this green one down here is my inferior vertebra now just to orient you with what we're looking at i want you to imagine that right here this is the anterior surface of the vertebral body so you're looking at an anterior surface so we have to go according to the patient so over here is left over here is right okay so this movement right here just to orient you this would be left lateral flexion because this is over at the left this would be right lateral flexion because this is the right side this would be left rotation and this would be right rotation okay so let's imagine for a moment let's imagine right rotation okay we're going to really neglect the rotational part and just talk about the up sloping and down sloping but again remember we're doing rotation to the right so based on what we just talked about where would lateral flexion occur in the lower cervical spine well if we have rotation to the right we can't help but have a little bit of lateral flexion to the right okay so if i rotate to the right over on this side does this side up slope or down slope well it's ipsilateral down sloping right this is down sloping what is downsloping it is where the superior vertebra translates posteriorly and here's the key inferiorly okay over on the left side what happens over here on this side we have this is the contralateral side because we're rotating to the right so on the left side we have up sloping right what is up sloping it's where the superior vertebra translates or glides superiorly and anteriorly the key i want you to remember is inferior glide on this side superior glide on this side what would that look like it would look like this okay because if i have inferior glide on the ipsilateral side that's part of the down sloping superior glide on the contralateral contralateral side that's part of the up sloping look what just happened as i rotate to the right i get a little bit of right lateral flexion so hopefully that makes sense to you and again this has to do with those arthrokinematic movements and ultimately at an anatomical level the orientation of those facet joints but again the upper c-spine follows type one mechanics where one is an odd number so lateral flexion and rotation are at odds with each other they're going in opposite directions so in the upper c-spine when it undergoes right rotation there's actually a little bit of left lateral flexion okay or we can say that when we rotate the neck there's contralateral lateral flexion or contralateral side bending now before we conclude the video let's take a look again at the rotation range of motion you can see that for rotation combined it's about 65 to 75 degrees now notice here the lower cervical spine contributes almost half of that 30 to 35 degrees but the atlanta axial joint c1 c2 contributes 35 to 40 degrees of rotational range of motion that's actually a little more than half of the contribution is just coming from the atlanta axial joint a little bit less than half is from the lower c spine but again notice the atlanta occipital joint so between the occiput and the atlas does not allow rotation just like the atlanta axial doesn't allow side bending or lateral flexion leno occipital doesn't allow rotation and a little bit more than half of that rotation is through the atlanta axial joint so hopefully this video made sense to you and gave you a good understanding of lateral flexion rotation in the cervical spine please make sure to like this video and subscribe to my channel for future videos and notifications thank you