 Hi, this is Dr. Srijita Ghosh from Kolkata. Today's tutorial is made in a background of the corona pandemic which is going on across the world. I work in Apollo Glennigal's Hospital, Kolkata, in a very close-knit department which unfortunately is running in shift duties. It seems ages since we have worked together all of us, had our famous hangouts and have gone for conferences where not only have we studied but have had so much fun together. I was just going through my Facebook pictures, found a nice one. The picture was taken in my dear friend Dr. Surabhi's wedding a few years back. Hello everyone, today's tutorial is a very short tutorial on the MRI anatomy of the rotator cuff. The basic things that you need to know mainly as a beginner if you are starting to report MRI shoulder. Before we go to the anatomy of the MRI part, we need to know a little bit of things of the gross anatomy of the muscles of the shoulder joint. The rotator cuff is actually a group of four small muscles in the shoulder which originate from the scapula and attach to the humerus to provide dynamic stability at the glenohumeral joint. Without the rotator cuff, the humeral head would actually ride up partially out of the glenoid fossa, lessening the efficiency of the deltoid muscle. These rotator cuff muscles, they lie deep in the shoulder underneath the stronger muscles namely the pectoralis major, deltoid, trapezius and latissimus dorsi. Now, we have to understand one very important thing that the head of the humerus articulates with the glenoid fossa in such a way that at one point only one-third of the humeral head sits in the glenoid fossa. This allows a lot of mobility but at the cost of stability. Herein lies the importance of the rotator cuff muscles which provide strength to this otherwise unstable glenohumeral joint. The four rotator cuff muscles that we need to know are commonly remembered by the acronym SITS6, S for supraspinatus, in for infraspinatus, T for teris minor and S for subscapularis. While SIT these are the muscles which come from posterior aspect of the scapula, the subscapularis comes anterior to the scapula, coming to each of these muscles separately in isolation. The supraspinatus as name suggests originates in the supraspinus fossa. That is why the name has come supraspinatus. It traverses towards the greater tuberosity of the humerus going underneath the acromion and it finally attaches to the greater tuberosity in the superior facet. In isolation the main action of this muscle is abduction. After this we go to the next muscle infraspinatus. As the name suggests again it originates from the infraspinus fossa. Again it traverses towards the greater tuberosity of the humerus and attaches in the middle facet. In isolation the main action of this muscle is lateral rotation. It has to be remembered that both these supran infraspinatus they have a common nerve supply the suprascapular nerve originating from the superior trunk of the brachial plexus. Why we need to know this? If there is an injury only to the suprascapular nerve we will find denervation edema only in these two rotator cuff muscles which will give us an idea as to which nerve issue we have to look into. Then comes tyrosminus this is a very small muscle inferior to the infraspinatus along the lateral board of the scapula and it gets attached to the greater tuberosity in the inferior part. So superior middle inferior facet the tyrosminus attaches in the inferior part its nerve supply is separate axillary nerve and it helps in lateral rotation. So before we go on to subscapularis we'll just recap so the greater tuberosity of the humerus has insertion of three muscles supraspinatus superior facet infraspinatus middle facet tyrosminus inferior facet. Now comes the anterior muscle subscapularis. The subscapularis is the strongest muscle which originates from a depression in the anterior surface of the scapula the subscapular fossa and traverses underneath the coracoid process and gets attached to the lesser tuberosity. The main action is internal rotation or medial rotation. The nerve supply is the subscapular nerve which has two branches actually the upper and lower. They are from the posterior cord of the brachial plexus. Now coming to the MRI appearance of the rotator cuff muscles. Before we go to each of the muscles we have to remember few things. Proton density non-fat sequence is the best sequence to study anatomy of the muscles and tendons. Each of these muscles have to be studied in all planes. Each sequence has to be studied right from the beginning to the end and not only in that part where the pathology is. At certain planes each rotator cuff muscle or any particular part is best evaluated. So we have to note in which plane we have to see which part of which rotator cuff muscle. Now let's see the structures as we scroll the various sequences one by one. Slowly we'll go through the main rotator cuff structures and few of the important landmarks because this tutorial is based only on the rotator cuff. So starting with the coronal sequence anteriorly the muscle belly that we see is the subscapularis. We also see the important to bony landmarks here is the coracoid process. Short head of biceps is attached to it. We also see the bulky muscle superficially which is the deltoid. Here clavicular attachment of the deltoid can be seen. We also see the musculotendinous junction of the subscapularis. The subscapularis reversing under the coracoid. The musculotendinous junction actually at the level of the bony glenoid. How do we know that as we go posteriorly? We will find that at the level of the musculotendinous junction of the subscapularis is the bony glenoid which is coming when we are scrolling posteriorly. Here is the bony glenoid which is coming to form the glenohumeral joint. We can see the axillary recess here. Now we also see the supraspinatus muscle gradually forming the musculotendinous junction underneath the acromion. See how the musculotendinous junction is looking like. It is the area where we see linear hypo intent structures starting to form the jet black structure which is the tendon proper. As we move further we are gradually seeing the concentrating on the tendinous attachment in the greater tuberosity of the humerus to form what is called the footprint. We have to remember one thing though anatomy laboratories claim that SSD footprint is very large but recent orthopedic literature feels that actually the supraspinatus footprint is a very small triangular footprint and it is more importantly the larger anterior portion of the supraspinatus muscle which smalls a smaller cross-sectional area of footprint predisposing these anterior articular fibres to most strain and tear propagation. As we go further backwards coming the last muscle that we see the infraspinatus we also see the acromion here so nicely and finally the infraspinatus tendon and this kind of completes our entire coronal viewing right from anterior to posterior. Tearous minor muscle is seen better in sagittal sequence and we'll see it here after. Next we come to the sagittal section we start from the area of the muscle belly and gradually go towards the rotator cuff tendon attachment side. See how the muscles are looking all voluminous no fatty infiltration, normal signal intensity, good volume, gradually we also see the multi-pinate structure of the subscapularis, the supraspinatus, muscular tendinous junction appearing gradually underneath the acromioclavicular joint, then the area of conjoined tendon which is interdigitating fibres of both supran infraspinatus which we call the conjoined tendon and finally the infraspinatus tendon we can also see the tearous minor muscle actually over here so the humeral head, acromion and underneath is the entire what is called the rotator cuff snugly hugging the humeral head, subscapularis, supraspinatus, conjoined tendon, infraspinatus and here tearous minor. In the sagittal section we also see a specific area called the rotator interval just beneath the coraca humeral ligament above the subscapularis. This is the area where we see early changes of adhesive capsulitis, this area will be separately dealt in a different tutorial. So this is how we view the structures sagittal sequence section right from muscle belly to the rotator cuff finally we come to the axial sequence from top to bottom this is the acromioclavicular joint now the muscle belly that we have seen here superficially is the deltoid this structure is the supraspinatus and parallel to the axis is the supraspinatus tendon showing hypointense signal of a normal tendon this is the coracoid process this is actually the area of the rotator interval the SGHL area seen a little intraarticular biceps is seen in that region actually. Now as we go further down we are seeing the muscle anterior to the scapular blade which is a subscapularis muscle followed by the jet black hypointense subscapularis tendon posteriorly is the supraspinatus muscle and the infraspinatus tendon also going towards the humeral head and the bicepital groove holding the biceps in its place. So axial is the best sequence to mainly see the subscapularis see the appropriate location of the biceps see the infraspinatus as we further go towards the axilla we can see the signal void of the axillary vessels the strong superficial muscles of the shoulder is continuously seen throughout which is the deltoid so this shows you how to see the rotator cuff muscles in all the sequences in continuity from muscle belly to tendon and back again back and forth. Before I actually end my talk a little bit of how these tendons actually look arthroscopically I have a few pictures from my orthopedic coli arthroscopic picture from the posterior viewing portal we have to remember that arthroscopically in the intraarticular location the tendons are not delineated as separate structures due to the capsule but if we view carefully we can understand that the anterior fibers and the posterior fibers can be seen and they can understand where the supraspinatus is and where the infraspinatus begins. We have to remember that this picture where the rotator interval is the tight big structure which we have seen along the boundary is the subscapularis in this picture we also see the intraarticular biceps and the pony glenoid this is the area where we expect the intact supraspinatus and infraspinatus remember this is the area of the footprint per se the footprint will be only exposed when there is a tear so before we end our tutorial the salient points that a beginner has to remember firstly we have to have an understanding of the normal anatomy the gross anatomy of these structures before we know the MR appearance PD non-fact sequence is the best sequence to study anatomy we have to study each structure in all the planes and each sequence has to be run right from the beginning till the end and not only focusing only on the area of pathology remember this is very important then we also have to know how a normal muscle looks like how a normal muscular tendinous junction looks like how a normal tendon looks like what is the normal signal intensity then only we can differentiate what is tendinosis what is the tear so for that we have to keep seeing normal cases to understand the abnormal and lastly this is a request before interpreting the MRI please have an idea about the clinical features of the patient the orthopedic examination finding if necessary talk to the consultant orthopedician as to what he feels because he has examined the patient and please have a look at the old radiograph if the patient has before starting the MRI interpretation thank you