 Hello everyone and welcome to another musculoskeletal radiology session on the Indian Radiologist YouTube channel. I am Dr. Chaitali Parekh and today the topic that we are going to discuss on is a simple but a crucial topic and that is cruciate ligaments imaging. Simple because the cruciate ligaments are large enough and well visualized on MRI so obviously the pathologies are well seen. Simple because as radiologists we have a pivotal role in deciding the further management for the patients so we help the orthopods in deciding whether the patient needs a surgical or a conservative management and whether the patient needs an immediate surgery or the patient can wait for a couple of weeks before he is operated on. Also in my personal experience I have realized that anti-recruciate ligament injuries are over-reported and there is often a confusion between the ACL injuries and mucoid T-generation. So if you want to solve all these queries in your mind then please look at the video. Thank you. So the outline for today's session is first we will discuss the normal ACL anatomy followed by ACL trauma or injuries. So this is the flow chart for today's session. In ACL we will discuss the normal anatomy acute and chronic injuries, what are the ancillary findings in ACL injuries and this is particularly important when you are in a dilemma whether the ACL is injured or not, other commonly associated soft tissue injuries and what should be a reporting checklist for a patient with ACL trauma. So anti-recruciate ligament is an intra-articular but an extra synovial ligament. This is the posterior cruciate ligament and this is your tbl attachment of the PCL which is posteriorly. Now normally on an MRI so these are three different sequences of MRI that is T2FS, proton density and T1 weighted images and if you will see you can appreciate the ligament fibers very well on both T2 fat saturated images as well as proton density images but it is difficult to differentiate the ligament fibers from the adjacent intra-articular fluid within the joint and hence it is also difficult to identify injuries and mucord degeneration of this ligament. So per se T1 weighted imaging does not have an important role in ACL trauma or mucord degeneration imaging. Now this is your femoral footprint in the intercontilar notch which is of the ACL and this is the tbl footprint of the ACL. Now one thing to note is that the femoral footprint is smaller as compared to the tbl footprint and as a result of this there is spanning out of the ligament fibers. So if you will see if you will appreciate on this sagittal image the fibers are tightly bound at the femoral attachment but as they come to the tbl attachment there is a gap or there is a space between the ligament fibers and there is insunation of normal intra-articular fluid and the synobium within between these fibers as a result of which it has an intrinsic hyper intense signal at the tbl attachment and this should not be mistaken for a low grade sprain or a low grade injury to the ligament. This is the normal appearance which is mainly because of the spanning out of the ligament fibers. Now anterior cruciate ligament comprises of two bundles that is the anterior medial bundle and posterior lateral bundle. Now it is important to identify both these bundles individually because single bundle injuries of the ACL can occur and they are often seen. So how do you remember what bundles belong to ACL and I am telling this because even posterior cruciate ligament has two bundles. So now you can just remember the word ampoule okay which is for the ACL bundles. So AM is your anterior medial bundle and PL is your posterior lateral bundle. So this is how you will remember the bundles of the anterior cruciate ligament. Now again this is our axial image and you can see this is your one bundle and this is your another bundle of the anterior cruciate ligament. So you can very very differentiate the two bundles separate from each other on an axial images and this anterior one is the anterior medial bundle and the posterior one is the posterior lateral bundle. Similarly on tbl attachment this is your anterior medial bundle and this is your posterior lateral bundle. Now for the labelling of these bundles what is the anterior and posterior is on the basis of the femoral attachment. So whatever is anterior is the anterior medial bundle and whatever is posterior is the posterior lateral bundle. Medial and lateral is on the basis of the tbl attachment. So here you can see that this is your wide shape, a wider medial meniscus and a smaller lateral meniscus. So this is your medial compartment and so this is your medial bundle and this is your lateral bundle. So that's why you have an anterior medial bundle that is anterior and medial bundle and you have a posterior and lateral bundle. Now on sagittal images this is the medial femoral tbl compartment and you can identify it from the triangular shaped appearance of the medial tbl content. This is your posterior horn of the medial meniscus. Now as you go from medial compartment towards the midline, the first structure that you see is a jet black ligament which is posteriorly and this is your posterior cruciate ligament. Now as you go further medially you begin to see the tbl attachment of the anterior cruciate ligament and then you can very well appreciate the entire anterior cruciate ligament fibers. Now here again you can see that there is some intrinsic hyper intense signal towards the tbl attachment of the anterior cruciate ligament and as we have discussed this is a normal appearance. This should not be labeled as a low grade sprain or a low grade injury of the ligament and this appearance is mainly because of the fanning out of the fibers from the smaller femoral attachment to a wider tbl attachment. And here you can see the jet black appearance of the femoral attachment which is because of the narrow attachment and a tightly bound fibers. Now on the coronal images this is your anterior coronal image where you can see that this is the medial femoral tbl compartment and this is the anterior horn of medial meniscus. Now as you go posteriorly you begin to see first is the tbl attachment of the anterior cruciate ligament and as you go further posteriorly this is your ACL and here you can see this is the inter-condylar notch of the femor laterally in the inter-condylar notch the ligament that you see is the anterior cruciate ligament. Medially you see another jet black ligament and that is nothing but the posterior cruciate ligament and you can very well appreciate the difference in the signal intensities of the two ligaments that is because the ACL has a fanning out fiber pattern whereas in PCL the fibers are tightly bound and here you can see that this is your femoral attachment and the femoral attachment has a jet black appearance because the fibers are tightly bound. So on axial images now this is your anterior cruciate ligament at the femoral attachment as you go from superior to inferior you can appreciate the two bundles very well so this is your anterior medial bundle this is your posterior lateral bundle and as you go further inferiorly this is the posterior cruciate ligament in the medial aspect of inter-condylar notch and here this is your tibial attachment of the anterior cruciate ligament so this is the one. So one important thing I want to stress upon is please look at the ligament in all the three planes the two bundles are difficult to differentiate on a sagittal image they can be differentiated on a coronal image but they are best seen on axial images so please make sure that you look at all the three planes particularly when you are in a doubt whether there is an injury or not some people do take a t2 oblique image for along the ACL but in my personal experience if you have a habit of looking at all the three planes you do not need another special sequence for the ACL imaging. So we've finished the normal anatomy now let's talk about the anterior cruciate ligament trauma. Before we discuss the mechanism of injury of ACL first let us discuss the functions of the ACL. So ACL limits excessive anterior translation of tba and external and internal rotation of tba over femur. Now there are two types of mechanisms of injury one is a non-contact injury and other is a direct contact injury now in non-contact injury there is no direct impact or an external impact on the knee or the leg it is a more common mechanism and commonly it is a valgus injury where there is internal rotation of tba relative to the femur it is commonly seen when there is a change in direction while running or whenever there is a rapid deceleration and it is seen in sports like basketball, football and skiing. In direct contact injury there is a direct impact on the knee joint it is a less common form of injury and because of the direct impact the knee goes into hyperextension. This kind of injury is associated even with posterior cruciate ligament injuries. So in this player you can see that there is twisting of the knee there is no direct impact on the knee and because of this twisting the femur and the tba they rotate in opposite directions and this results into tear of the ligament. So whenever there is a ligament tear the tba translates anteriorly and the posterior lateral tba impacts against the anterior lateral femur and hence you get this classical bone marrow edema pattern in ACL injury which is of the anterior lateral femur with the posterior lateral tba. So when you are actually imaging the patient the tba has come back in its normal position and this is the edema pattern that you will see in these patients. Now in ACL trauma can be a acute or a chronic one in acute injuries you need to look at the marrow edema pattern you need to look at the sulcus terminalis and paction injury which we will discuss in a while and you need to look at the ligament itself whether it is completely tow or there is a partial tear single bundle injury or osceous avalanche. So let's look at each of these individually. So as we've already discussed the bone marrow classic bone marrow edema pattern is the anterior lateral femur and posterior lateral tba. That's on the lateral compartment similarly on the medial compartment there is impaction and hence you get a edema in the peripheral medial femur and posterior medial tba. Now you need to remember that all the four edema are not seen in a single patient. You may get various permutations and combinations sometimes edema can only be in the lateral compartment sometimes only in the medial compartment sometimes you can also only get edema in the tba and nothing in the femur. But just remember that whenever you see edema in any of these sites your antenna should go up and you need to look at ACL for ACL injury. Now in ACL trauma the second thing that you need to look for in an acute injury is the sulcus terminalis impaction injury. Now what exactly is sulcus terminalis? So it is that portion of the anterior lateral femur which is just anterior to the anterior horn of lateral meniscus. So this is the anterior horn of lateral meniscus border and just anterior to it this anterior lateral aspect of femur this is the sulcus terminalis. Now if you will see that the sulcus terminalis is normally very straight but in patients with ACL injuries there can be a sulcus terminalis depression and this happens mainly because the posterior lateral tba goes and impacts against the sulcus terminalis and so you can see that here normally it was straight but in this patient you can see a depression and even on the fat saturated images you can see that there is a sub cortical fracture which is nothing but a trabacular fracture with a lot of marrow edema. So this is what is the sulcus terminalis impaction injury or depression and whenever you see this this acts like an ancillary finding and you need to look at the ACL for ACL injury. Importance of sulcus terminalis impaction injury is for in the radiographs. So whenever you get x-rays for reporting this is what is the so this is a lateral radiograph of bilateral needs and this is the normal site you can see that the sulcus terminalis is normal here but in this patient you can see that there is a depression in the sulcus terminalis right. So you can see that there is this depression over here and this is nothing but your sulcus terminalis impaction injury and if you pick this up on a radiograph you can actually advise the orthoport for further imaging to look at the ACL ligament itself and so your report will be you will have an edge over your peers in the report. Next thing what you need to look at is the ligament itself. Now whenever you are describing an ACL injury in an MRI report you need to mention the site of the injury and the grade of the injury. By site of the injury I mean whether the injury is at the feverell attachment, proximal throat, mid substance or tibial attachment. So let's look at one of all of these. So this is your normal ligament where there is a jet plaque feverell attachment and a slightly hyper intense tibial attachment. Here you can see that you cannot appreciate any feverell attachment and in fact if you see that all the fibres they are lying over the tibial plaque. So this is a feverell attachment tear again you cannot see any feverell attachment on the coronal as well as the edgyal images. In this patient you can appreciate the feverell attachment but there is a full thickness tear in the proximal throat of the fibres. Similarly on the coronal and the edgyal images you can see that there are fibres at the at feverell attachment but proximal throat there is a full substance tear. Here there is a complete mid substance tear which can be again appreciated on all the three planes and this is particularly important from the prognostic point of view. So this is your auspicious evolution at the tibial attachment. Now this is very important to mention in the report and whenever you mention an auspicious evolution you need to mention two things. One is the size of the fragment that is evolved okay. So this is your ap dimension and this is your lateral dimension. So you need to mention that you need to mention the superior translation of the auspicious fragment relative to the underlying tibia. So how much has the auspicious fragment displaced superiorly and the second thing that you need to mention is what is the status of the ligament itself whether it is intact whether there is just some contusion or a low grade injury or the ligament itself is also torn. Now why this is important whenever there is an ACL injury and there is bone marrow edema the surgeon will wait for six weeks for the edema to settle down and then go for an ACL reconstruction but whenever there is an auspicious evolution and if the bone piece is a big one particularly that it can be fixed back with the screw the patient will go for an urgent or immediate surgery because he needs to fix the bone back before the bone undergoes auspicious remodelling. That's why one thing is you need to identify the auspicious evolution. You need to mention the size of the fragment because he needs to decide whether the fragment can be fixed back or not and the third thing is what is the ligament status itself. Now if the ligament is intact he will fix back the auspicious fragment but if the ligament itself is injured then the orthopod may actually think of going ahead with the reconstruction later on. So this is a t-well attachment auspicious evolution and these auspicious evulsions can also be very well seen on radiocrats. So here you can see that this is an evolved bone piece over here from the anterior interpondyla remnants of tibia and this is your auspicious evolution on the AP view as well. Now sometimes the auspicious evulsions can be smaller ones and because of the edema it is very difficult to sometimes pick up these auspicious evulsions. In such cases radiographs can be really helpful. So always make sure to look at the auspicious evolution of the ACL when you get an x-ray for reporting and also to look at the x-rays when you get an MRI for reporting because they're really helping. So we look at the entire spectrum you have a femoral attachment injury, proximal third injury, mid-substance injury and a t-well attachment auspicious evolution. The next thing what you need to look at is the grade of the injury whether it is a full thickness tear, partial thickness tear or a single bundle injury. So here you can see that this patient has got a full thickness tear this patient you can see that there is injury but there are some intact fibers as well and when you look on the axial images you can very well see that the central fibers are injured the peripherally fibers look intact. So this is a partial thickness tear. Again in this patient you see that there is some injury but some of the fibers are intact and when you look on the axial images what you identify is that the anterior medial bundle looks intact but the anterior the posterior lateral bundle is injured. So important to notice whether it's a partial thickness injury or a tear versus a single bundle injury you cannot differentiate them on a sagittal image but when you look on the axial images you can very well identify what kind of injury it is. So always make it a point to look at the injury in all the three planes particularly when it is not a full thickness tear and you are in a dilemma whether the ligament is injured or not and what is the extent of injury. So now we have discussed the acute injuries and what things you need to look out in acute injuries the second thing what you need to know now is the chronic injuries. So again in chronic injuries the first thing you look at is the sulcus terminalis depression but in chronic injuries you may not see the bone marrow edema pattern unless the patient had another acute event over a chronic injury. So only what you will appreciate is that there is a depression of the sulcus terminalis. Now why that is important because if you see that depression you know that there had been an ACL injury in the past. Now anterior cruciate ligament tends to heal or remodel and sometimes the ligament remodels so well that on a follow-up MRI you will not identify that this ACL was injured in the past unless you see ancillary findings like a sulcus terminalis depression. Next thing you need to look at is the ligament itself so it can be a remodeled ACL or it can be that there is no significant healthy ligament fibres now because of the chronic injury. So this is a poorly remodeled ACL you can see that the ACL fibres are continuous but they are looking very fuzzy you cannot identify the fibres strands very well. Similarly on the femoral attachment you know that this fiber has not healed well. In this patient you can see that the fibres are trying to heal they have healed better as compared to this patient but again the femoral attachment does not look that good. So this is a partially remodeled ACL and in this patient there is no significant ACL that is left. So this patient does not have a healthy ACL remaining at all. Now important class of patients is this partially remodeled and a well remodeled. Now well remodeled ACL will look just like a normal ACL so you will not identify that this patient had injury in the past unless you have a previous imaging or you see some ancillary findings or you get a good history from the patient. So particularly this is important because sometimes what happens is that you only have reported the previous imaging and you have mentioned that there was a full thickness tear or a partial thickness tear and when the patient comes for a follow-up you are not aware that you had reported a previous scan and you will give a normal ACL and that will be a big blunder. So always remember to get a good history and to always look at the old imaging always ask for the patient whether there is an old imaging and if yes please look at the old imaging so that you don't make such silly mistakes. What are the ancillary findings? They are other soft tissue injuries and bone injuries which will help you to come to a conclusion that yes this ACL is injured. So one is obviously a bone marrow edema pattern, sulcus terminalis, infection injury. The third thing is your anti-gay translation of TBR. So normally when you can draw what you do is you draw a line tangential to the lateral femoral contile and tangential to the lateral tBR. There is not much of a gap between these two lines but whenever there is an anterior translation you can see that there is an increased gap between these two tangential lines and whenever this gap is more than 7 millimeters it is confirmed to be as an anterior translation of tBR and this usually happens with ACL injury. You can also do stress radiographs. So these are natural radiographs. This one is without stress and this is with stress. Now the point to note is the red line is along the posterior cortex of lateral femur and the yellow line is along the posterior cortex of lateral tBR. Now without stress you can see that the yellow line is behind the red line but whenever this patient is put in stress and the radiograph is taken you can see that the yellow line is actually come anterior to the red line. This is because the tBR has translated anteriorly. So even stress radiographs can help you to identify whether this patient has an anterior ligament laxity or a knee laxity and thus you can know that this ACL is done in this patient. The next thing you look at is the hyperbuckle TCL. Now this is a normal smooth appearance or a smooth curvature of the TCL whereas in patient with ACL injury you have this hyperbuckle TCL or a question mark kind of appearance. The next is fibular collateral ligament is seen in a single plane. Now first let us understand what is the appearance of a fibular collateral ligament in a normal patient. So here this is your femoral attachment of the fibular collateral ligament. This is the lateral compartment because you can see the fibula over here and you can only see proximal one third of the ligament. The rest of the ligament is not visualized. When you go posteriorly you can appreciate the mid substance of the ligament and further posteriorly you can appreciate the fibular attachment. So fibular collateral ligament normally has an oblique course and the entire ligament can be visualized on sequential images. But whenever there is an anterior cruciate ligament injury there is anterior translation of TBR and as a result of this you can see the entire fibular collateral ligament on a single image. So when you see this go back to your ACL and just see if there is a ACL injury or if there is a remodeled ACL. Next you look out is for the sagons fracture which is nothing but the anterolateral ligament osteosurgery. So this is the coronal image you can see that this is your medial compartment and there is a high grade medial collateral ligament injury in this patient. Now this small flimsy structure which is seen just anterior to your popliteous tendon this is your anterolateral ligament and you can see that there is a bone piece that has been ever stopped at the TBR attachment and this is nothing but your sagons fracture. Now sometimes the sagons fracture is so small that it can be missed on an MRI but you can very well appreciate the sagons fracture on an X-ray. So make sure to look at the X-ray in these patients. Sometimes there won't be an osteosurgery at the TBR attachment but there will be an injury at the femoral attachment. So this patient has an intermediate grade injury at the femoral attachment of anterolateral ligament whereas here you can see that there is a high grade injury at the femoral attachment. Now sagons fractures need to be dealt with and if possible they'll be fixed back if it's a large osteosurgery fragment because they result into persistent nilacity which can further result into graft retail. But how important is a ALL injury, ligament injury for sale is a question of debate because the ligament is so thin and flimsy that such a thin ligament actually resulting into a niligament laxity which can result into a pair of the entire graft is something which is still a question of debate. But nevertheless if you see it you can put it in the report but don't miss sagons fractures and look at the X-rays because X-rays has been seen by the orthoport. He knows that there is a sagons fracture and if you miss it on an MRI you are making a big planter. So whenever you get ACL injury patients please try and get your radiographs and look at any small fractures in the bones. Another similar small fracture is your arcuate fracture which is at the arcuate ligament complex attachment and so this usually occurs at the posterior aspect of the fibular head. So this is your arcuate fracture and again if you will see it's a very small fracture. So this is your arcuate fracture this is a very small fracture piece and they are easily missed on an MRI but if you correlate them with the radiograph they can be easily picked up. So again key point please look at the radiographs in patients with ACL injuries so that you can pick up such small fractures. What are the other soft tissue injuries that you need to be aware of in ACL patients is in medial compartment look out for ramp lesion. So ramp is nothing but a longitudinal tear which is occurring at the posterior medial meniscocapsular junction. Look out for bucket handle tears medial collateral ligament injuries. In the lateral compartment look for Drisberg rib tear which is nothing but a peripheral longitudinal tear in the posterior horn of lateral meniscoces adjacent to the ligament of Drisberg attachment. Look for other injuries like bucket handle tear lateral collateral ligament tear and obviously look out for your posterior lateral corner and lateral ligament injuries. So you need to look at all these injuries and put them in your report in an ACL injury patient because if these injuries are not addressed it can result into a graft failure. Now clinically whenever the patient goes to the orthopod he will do a lachman test and an anterior drawer test and if the ACL is torn the tests are going to be positive. So even the orthopod knows that there is an ACL injury then why do we need to do an MRI. So one is in an acute setting when there is a lot of bone marrow confusion and it is difficult to test the patient because obviously of the contusions and the joint effusion. Second is to look whether there is bone marrow edema or not because if there is bone marrow edema the surgeon will not take the patient immediately for a ligament reconstruction. Instead he will wait for about six weeks for the edema to go down and this is important because in ligament reconstruction the surgeon needs to drill tunnels in the femur and the tibia. If there is bone marrow edema and the bone is weak it can result into fracture of the bone. So once the bone has healed completely the surgeon will take the patient for a ligament reconstruction. Obviously you need to mention any oscious avalgene because such patients need to go for surgery immediately and you need to mention what is the fragment size and the superior displacement of the oscious fragment and what are the other associated soft tissue injuries like MCL or a bucket handle tear. Now whenever the patient has a ACL tear and along with that there is a bucket handle tear sometimes the lathment test will come negative that is because the meniscal fragment has now come in the intercontinental notch and is providing some amount of stability to the joint. So often these patients will come as a lathment test negative or the surgeon may get some lathment test positive but with a firm endpoint. So this is again where he needs to do an imaging to confirm whether a ACL is injured or not. So these are all the points that you need to put in your report for an adequate report of an ACL injury patient. First you need to mention the bone marrow edema pattern what is the status of ACL itself the site and grade of injury and the size and displacement of the oscious fragment in case of an oscious avalgene. There are the ancillary findings so you can obviously you don't need to put the fibular collateral ligament in one plane and all of those stuff in your report but sulcus terminalis, impaction injury, arcuate ligament injury, sagons fracture all of these you need to mention in your report. Where the other soft tissue injuries like your meniscal injuries and collateral ligament injuries. In chronic patients important thing to mention in the report is the cartilage status of the patient. If these patients are known to develop lateral compartment osteoarthrosis more commonly than medial compartment osteoarthrosis and whenever the patients develop OA the treatment management may change and the surgeon may consider other options. So when you put all of these things in your report your report is complete all the questions of the orthoport will be answered. I hope you guys have liked the video on the ACL injuries time to relax your brains and absorb whatever you gained from this video and we'll be coming up soon with the video on mucoid degeneration of ACL as well as posterior cruciate ligament pathologies. In the meantime if you've liked the video please hit the like button and type in your comments and your queries in the comments section and we'll get back to you. Thank you and stay tuned.