 Hello everyone and welcome again for another video on musculoskeletal imaging in the Indian radiologist channel. I am Dr. Chaitali Parekh and I am a consultant musculoskeletal interventional radiologist. Firstly, I would like to thank Ognito for their association with Indian radiologist. Today we will be discussing on imaging in acromuclavicular joint injuries. I know it's a less talked about joint but with an increase in dedicated imaging in sports injuries, we see ac joint injuries more often and that's when we start biting our nails and thinking that what really does the orthopod want. So what are you waiting for? Let's find out. Acromuclavicular joint is a superficial joint that is particularly injured in contact sports and depending upon the type of injury the management can vary from conservative to a surgical one. So let's discuss about the ac joint injuries. In today's session, we'll discuss the normal anatomy of the ac joint, normal radiographic views and x-ray appearances, normal MRI anatomy of the joint, mechanism of injury, rockwood classification, abnormal MRI and radiographic appearances. So first let's discuss the normal anatomy of the acromuclavicular joint. The ac joint is stabilized by static and dynamic stabilizers. The static stabilizers are the ligaments and the dynamic stabilizers are the muscle attached into the clavicle. The ligaments are named depending on the bones that they connect. So you have the acromuclavicular ligament and you have the coracoclavicular ligament. Acromuclavicular ligaments are two-in number superior and inferior. The dynamic stabilizers consist of the deltoid and the trapezius that attach to the lateral end of the clavicle. Now the most important and strongest stabilizer of the ac joint is the coracoclavicular ligament. As I said acromuclavicular ligament are superior and inferior. They are present along the joint capsule and they cannot be differentiated from the joint capsule. It is more of a horizontal stabilizer which means it reinforces the joint in small degrees of distraction. So whenever there is injury to this ligament, there'll be widening of the joint space. On the other hand, coracoclavicular ligament is the strongest stabilizer. It has two components the conoid and the trapezoid components where the medial one is the conoid and the lateral one is the trapezoid and the two components are separated by a fat or bursa. It is more of a vertical stabilizer which means it prevents superior or inferior translation of the clavicle. So whenever there is an injury to the coracoclavicular ligament, the clavicle can dislocate superiorly which is more often and also inferior. Deltoid and trapezius are dynamic stabilizers which are important when the ligaments are torn. So this is a graphic representation of the normal shoulder girdle. So as you can see this is the humerus that is articulating with the glenoid and this is the entire scapula. This is the coracoid process that is the acromion process which is coming posteriorly from the spine of the scapula and this is the clavicle. This is the acromoclavicular joint with the joint capsule. Now normally the acromion clavicular joint is about 2 to 3 millimeters. The ac ligaments are along the joint capsule as you can see here and they are 2 in number. So it's a superior and an inferior ac ligament. The next is the coraco-clavicular ligament which has got two components. The medial one is the conoid and the lateral one is the trapezoid. It is actually not important to differentiate between the two components. In fact you just need to remember that there is a ligament known as the coraco-clavicular ligament which connects the coracoid process to the clavicle. The third is the coraco-acromion ligament. Now this is not a stabilizer of the AC joint. The reason why I have put this ligament I'll discuss it later and this is the line joining the inferior border of the acromion and the clavicle. Normally the inferior border of the acromion and the clavicle they lie in the same plane. When they are not in the same plane it indicates that there is a ac joint subluxation or dislocation. There are variations in the superior border of the acromion and the clavicle. They may or may not be in the same plane normally. So it is the inferior border which is important. Now let's look at the normal radiographic views and x-ray appearances of the ac joint. So this is the normal radiograph of the ac joint in the AP view that is the lateral end of the clavicle that is the spine of the scapula forming the acromion process. This is the acromio-clavicular joint. This is the humerus that is articulating with the glenoid and just above the glenoid this here is the coracoid process. Now this is the normal coraco-clavicular distance which is about 11 to 13 millimeters and this is the normal acromio-clavicular distance which is nothing but the joint space which is about 2 to 3 millimeters and as I've told you the inferior borders they lie in the same plane whereas the superior border may or may not be in the same plane normally. So as far as the radiographic views is concerned the first one is the AP view of bilateral ac joints. So this is the AP view which is showing the bilateral ac joints and that is the coraco-clavicular distance on both the sides. Normally the coraco-clavicular distance is same on both the sides. This radiograph is useful to compare the coraco-clavicular distance on the injured side with the normal side. If the coraco-clavicular distance is increased on the injured side it indicates that there is a acromio-clavicular joint injury on that side. Now this is the ac distance on both the sides and as you can see they are same on both the sides. If there is a widening on one side then it indicates that there is a ac joint injury on that side. In case of ac joint sprain weight bearing x-rays can be done where you can hold weights in both the hands and then the x-ray is taken. So normally when there is an ac joint sprain the ac joint distance may remain normal but when you take weight bearing x-rays there will be widening of the ac joint distance on the injured side and that's how you can diagnose a ac joint sprain or a lower form of ac joint injury. Now next is the Zanka's view which is more specific for the ac joint. So in this case the x-ray beam is directed 10 degree kephalad and as a result of which you get this picture of the ac joint. So ac joint is seen well in profile and it is not overlapped by the spine of the scapula or any other osteo structures. And the third one is the axillary lateral view. So this is how the axillary lateral view is taken and as you can see this is the humerus articulating with the glenoid that is the clavicle and that is the acromion process and that is the coropoid process that is overlapping over the clavicle. So this is how the x-ray would look like. It is as if you are looking on the ac joint from the top right. So here you can see this is the clavicle and this is the acromion and that's the acromio clavicular joint. Now this x-ray is particularly useful in identifying posterior dislocation. So where the clavicle will shift posteriorly. So posterior dislocation of the ac joint injury. Besides that you can also identify fractures of the acromion process and of the lateral end of the clavicle. So in this patient you can see that there is a well corticated body with a radio lucency and this doesn't look like an acromion fracture in fact this is an os acromion. So be careful before you report os acromion as an acromion fracture in younger individuals less than 23 to 24 years old. In them just make sure that there could be an os acromion which is present. Now let's look at the normal MRI anatomy of the ac joint. So as far as the MRI protocol is concerned you do not need a separate protocol for ac joint. Ac joint should always be included as a part of the routine MRI shoulder study. Use a small FOV so don't scan till the distal humerus as in that case the ac joint will be seen as a miniature and you won't understand the head and tail of the joint. So this is what is a normal FOV for a shoulder MRI should be where you can see the shoulder joint very nicely the tendons very nicely as well as it should cover the acromion clavicular joint. Have maximum of 3 millimeter thickness images with 0 millimeter slice gap and proton density images are good for visualization of tendons and ligaments. So now we look at the normal MR anatomy this is the coronal image and we'll be going from anterior to posterior and this is a graphic representation just to help you with the anatomy. So anterior most coronal image shows the coracoid process with the short head of bicep stenten attaching to the coracoid process. As you go posteriorly you start to see the clavicle with the trapezius attaching to the superior aspect of clavicle and the deltoid attaching to the inferior aspect of clavicle. Now in the next section you can see a thin hypo intense structure that is arising from the coracoid and this is nothing but the coraco-clavicular ligament. So as you go posteriorly you can actually trace this ligament and you can see now that there are two components the medial one is the conoid and the lateral one is the trapezoid but as I told you you don't need to remember them and you can see that there is fat between the two components very nicely appreciated and as you go posteriorly you can see that this ligament goes and attaches to the under surface of the clavicle. Now I'll just go back and I told you about another structure which is nothing but the coraco-acromia ligament. So this is the coraco-acromia ligament and if you trace it you see that it goes and attaches to the under surface of the acromion process. Now this ligament is not a stabilizer of the ac joint but it is important because whenever there is a CC ligament injury and if the CC ligament is not seen you can mistake the coraco-acromia ligament for an intact coraco-clavicular ligament. So whenever you see any ligament make sure you trace both the ends of the ligament before diagnosing a ligament injuries present or not. Again as we go posteriorly you start to see the clavicle and the acromion and this is nothing but the superior acromia clavicular ligament and this is the inferior acromia clavicular ligament and that is the acromia clavicular joint space. So this is about the anatomy on the coronal images. Now let's look at the sagittal images. Now you're going from lateral to medial and what you see is the humeral head, the rotator cuff tendons above the humeral head and above the rotator cuff tendon lies the acromion process. So as you go further medially you see there is a jet black structure that arises from the acromion and if you trace this this goes and attaches to the coracoid process over here right. So this is again nothing but the coraco-acromion ligament which forms the coraco-acromion arch above the supraspinitis tendon. So again don't mistake this ligament for the coraco-clavicular ligament. Now as you go further medially you start to see the lateral end of the clavicle. This is the acromion and this is the ac joint space that's the superior acromion-clavicular ligament and that's the inferior acromion-clavicular ligament and another structure that you see is the coracoid process with the short head of bicep tendon attaching to the coracoid process. As you go further medially you start to see the coraco-clavicular ligament. So here you can see a ligament that is arising from the under surface of the clavicle and as you go further medially you can see it goes and attaches to the coracoid process. So that is the normal coraco-clavicular ligament and this structure is the coraco-acromion ligament. So please don't confuse between the two. It is the coraco-clavicular ligament which is really important for the ac joint. Now let's discuss the mechanism of injury. So ac joint injuries can occur from direct or indirect forces. Direct forces is nothing but a direct trauma onto the ac joint. Indirect forces consist of like a fall on the outstretched hand where the humerus impacts against the acromion process. So in case of direct forces you can have a direct blow to the acromion process. Now whenever there is a direct blow to the acromion process the acromion process will shift inferiorly which will result into tearing of the acromion-clavicular ligaments. With further force or with more stronger force there will also be an inferior force acting on the scapula and the coracoid process. So the entire scapula with the coracoid process will start to shift inferiorly which would result into tearing of the coraco-clavicular ligaments. And now if you see the lateral end of clavicle is free to dislocate. Now normally the clavicle is oriented slightly superiorly as you go from medial to lateral which means the lateral end of the clavicle is slightly superior as compared to the medial end and because of this orientation the clavicle often tends to dislocate superiorly. So this is what happens in an ac joint injury. It can also happen from a fall on the shoulder as shown in this image. The mechanism is same there is again a downward force that is acting on the acromion and the scapula. Now let's look at the rockwood classification. So this is the crux of the MRI reporting in ac joint injury and if you understand the classification well the entire reporting becomes pretty easy. Now I know this classification looks very huge and very confusing but don't worry I'll try to make it as simple as possible. So as per the rockwood classification there are six types of ac joint injuries and which are predominantly classified on the basis of these four things that is ac ligaments, cc ligaments, deltoid and trapezius muscles and the dislocation of the clavicle. So let's just look at each of the types individually. Before we go to the individual types the just one point to note is that the most important structure in this entire classification is the coraco-clavicular ligament why we'll see that. So in type one the ac ligaments are sprained and rest everything is intact. So this is nothing but the type one where there is no dislocation of the clavicle. In type two your ac ligaments are disrupted as a result of which there is widening of the joint space your cc ligaments are sprained but they are not toned. Okay so there can be some increase in the coraco-clavicular distance which is usually less than 25 percent of normal. Now in type three there is ac joint injury as well as there is coraco-clavicular joint injury and so there is a ac joint dislocation. Besides that you can also have injury to the deltoid and the trapezius attachments to the lateral end of clavicle. Now in this scenario the cc distance is increased but 25 to 100 percent of normal which means that the cc distance is either less or up to twice of normal. It is not more than twice of normal right. So in type three the cc distance is less or up to twice of normal and this is obviously you can see that there is a ac joint dislocation the inferior borders are not a number. Let's discuss type five. So I have skipped type four we'll discuss type four later. So in type five again everything is injured the only difference is in this case the cc distance is more than 100 percent or it is more than twice the normal right. So in this case if you see this is your normal cc distance. This is type three where if you see that the cc distance is increased but it is less than twice the normal and this is now type five where obviously the cc distance is obviously more than twice the normal. So this is what is type five injury and again it's obviously dislocated. Now we come back to type four so in type four also everything is injured but important thing to note is that the clavicle dislocates posteriorly. So in type three and type five the clavicle dislocated superiorly whereas in this case the clavicle will dislocate posteriorly and the cc distance may vary it can be marginally increased it can be markedly and in type six what happens is following the ligament injuries the clavicle dislocates inferior to coracoid and this is very rare form of injury. So again now this chart we've pretty much simplified we know what each type is. Now there are two landmarks in this classification which is between type two and type three and between type three and the rest of the types and that is because of the management. So in type one and two we have a conservative management. In type four five six you have a surgical management whereas in type three the management is controversial. So for elderly or sedentary people a conservative management is preferred whereas people who are into sports athletics or into gymming or laborers who have to use their arms violently often for them a surgical approach is preferred. So your orthopore is not interested in knowing whether it is type one or type two either of the type he knows that it is a conservative management but you need to differentiate between type two and type three because that is where the management will change and you need to differentiate type three from the rest of the types because again if it is rest of the types then you know that it is more unstable injury and the patient will more often will go for a surgical management. So this is how your orthopore is interested in knowing that what type of injury it is and now how do you judge what type it is. So as I told you the most important structure is the CC ligament. So if your CC ligament is toned I'm not talking about sprain it should be toned in that case it is type three and above. If it is not toned if it is intact or sprained it is type one and type two. So that's how you differentiate two from three. For differentiating which type it is from three to six you actually require a radiograph of the AC joint and on the radiograph if there is a posterior dislocation of clavicle it is type four if it is inferior dislocation of clavicle it is type six if it is superior dislocation then it can either be type three and type five. In type three the CC distance is less than or up to twice the normal whereas in type five the CC distance is more than twice the normal. So that's how you can differentiate that which type of injury it is. Now let's look at some abnormal cases. So in this patient you can see that there is distal clavicular edema. There is some edema along the AC ligament but it does not appear toned. If you see that the superior ligament is more injured or sprained as compared to the inferior one on the sagittal image and on this sagittal image you can see that the coraco-clavicular ligament is intact in fact you can also appreciate the fat between the two components. So this is nothing but sprained AC ligament intact CC ligament which is nothing but type one. Now in this patient you see that the ligaments are in fact toned so at least the superior ligament is toned on this coronal image and on this coronal image you find that even the inferior ligament is toned so both the ligaments look bad and in this sagittal image you can see that the coraco-clavicular ligament is intact but it is bulky and edematous. So it is sprained but it is not disrupted. So this is nothing but toned AC ligaments sprained CC ligament which is type two. So here you'll see that there is high grade injury to the afternoon clavicular ligaments they don't look that great and on the sagittal image you'll see there is a discrete tear of the coraco-clavicular ligament towards the coracoid attachment and also there is edema in the deltoid towards the clavicular attachment. So in this is nothing but a type three injury where there is injury to the acromio-clavicular ligaments and there is tearing of the coraco-clavicular ligament. Now for the next two cases try to frame in your mind which type it is and see if you can identify it correctly. So in this patient again there is tear of the acromio-clavicular ligaments. Here you can see that there is a discrete tear of the coraco-clavicular ligament towards the clavicular attachment. Also there is some tear of the deltoid attachment to the clavicle with edema in the deltoid muscle. This patient also had a fracture of the acromion process and if you'll see this is the lateral end of clavicle and they are pretty much in the same plane and also there is a auspicious evulsion fracture at the capsular attachment of the lateral end of the clavicle. So which type it is? There are ligament injuries, there are bone fractures, there is muscle injury. Don't get confused when you start to see additional findings like an acromion fracture or a clavicle fracture. Just go back to your basics and identify which ligaments are injured and identify which type of injury it is. So though this patient has multiple findings yet it is nothing but a type 3 injury with obviously additional acromion fracture and a capsular evulsion fracture at the lateral end of clavicle. Now again identify which type it is. So here you can see that the ac ligaments are injured and if you'll see the cc ligament is intact but you cannot identify the internal architecture of the fibres inside. So it is intact but it is sprained. So obviously this is nothing but type 2 injury. Now let's look at the abnormal radiographic appearances. So this patient you'll see that the inferior borders are not aligned but it is not dislocated completely. So this is nothing but an ac joint subluxation which can happen in type 2 and in this patient you can see that the cc distance is actually more than twice the normal. So this is the normal side and there is a obvious ac joint dislocation. Now since this cc distance is more than twice the normal and it has dislocated superiorly this is nothing but type 5 ac joint injury. Now before we finish the talk let's discuss something about distal clavicular stress which is commonly seen in weight lifters. So because of repeated weight lifting there are multiple micro fractures that happen in the clavicle which can result into just some marrow edema in the lateral end of clavicle which is called as stress edema or it can also cause development of stress fracture. So you can see this hypo intense line which is not seen in this patient or because of repeated micro fractures there can be osteolysis of the lateral end of the clavicle which is called as distal clavicular osteolysis. So you can see that there is widening of the joint space which is because of the osteolysis or the resorption of the lateral end of clavicle and along with that this patient has a control body within the joint space and if you'll see the lateral margin of the clavicle is very irregular which is because of the osteolysis and this distal clavicular osteolysis is also known as weight lifters shoulder. Okay whenever you do an MRI in a suspected ac joint injury first look at the ac ligaments if it is intact there is no ac joint injury. If the ligaments are injured which can be either sprained air whatever look at the cc ligaments. If the cc ligament is not toned in that case if it is completely intact it is type one if it is sprained it is type two. If the cc ligament is toned then you need to see the x-ray for the direction of clavicle dislocation. So if the clavicle is dislocated superiorly look at the cc distance if the cc distance is less than or up to twice the normal it is type three and if it is more than twice the normal it is type five. Type four is where there is posterior dislocation of clavicle and type six is where there is inferior dislocation of clavicle. So if you follow this flow chart your reporting will become very easy and now by looking at this flow chart you know what important things we need to mention in your report. So again take home points coraco-clavicle ligament is the strongest stabilizer of ac joint and an important ligament to look in any ac joint injury. Classify the ac joint injury as per the rockwood classification. It is important to differentiate type two from type three that is what your orthopod wants and coraco-clavicle ligament is helpful in doing that and it is important to differentiate type three from type four five six again that is what your orthopod wants and again radiographs will be helpful in differentiating them. Thank you for watching the video and if you've liked the video please hit the like button and subscribe to the channel so that you don't miss on any future videos and if you have any queries or comments please feel free to write them in the comment section and I'll get back to you. Keep safe distance stay safe and stay healthy.