Rotator Cuff | 3D Anatomy Tutorial

hi this is Peter from Anatomy zone and in this detour we're going to take a look at the anatomy of the rotator cuff the rotator-cuff are a group of four small muscles within the shoulder which originated from the scapula and detached to the humerus to provide dynamic stability at the glenohumeral or shoulder joint these muscles are found deep within the shoulder so here you can see the pectoralis major deltoid trapezius and latissimus dorsi muscle which are some of the large muscles involved in moving our shoulder underneath these we can find the rotator cuff muscles so our shoulder joint is made up of the head of the humerus which sits within the shallow glenoid fossa at any one time there was only about one third of that humeral head sitting in the glenoid fossa this configuration allows lots of mobility of the joint but in return the shoulder joint sacrifices stability to regain stability we have for rotator cuff muscles which can be remembered by the acronym sits supraspinatus infraspinatus teres minor and on the anterior surface of the scapula the sub scapula in this title will discuss each one of these muscles in turn the supraspinatus originates any supraspinous fossa as with many anatomical terms the name of the muscle itself gives you a clue about where it's located Supra refers to above and spine ATIS refers to the spine of the scapula so the supraspinatus sits in the supraspinous fossa above the spine of the scapula the supraspinatus then passes underneath the acromion to attach on to the greater tuberosity on its superior facet in terms of its action the supraspinatus muscle in isolation creates abduction of the humerus the muscle is innervated by this suprascapular nerve the next muscle is the infraspinatus so from its name we can tell that it's located below the spine of the scapula and it sits within the infraspinous fossa the infraspinatus muscle inserts onto the greater tuberosity of the humerus on its middle facet just below the insertion of the supraspinatus muscle in isolation the infraspinatus muscle performs lateral rotation or external rotation of the humerus it's worth noting that the supraspinatus and infraspinatus share a nerve supply derived from the suprascapular nerve which comes off the superior trunk of the brachial plexus to supply both of these muscles next we have the teres minor muscle the teres minor muscle is located just inferior to the infraspinatus on the lateral border of the scapula it then inserts onto the greater tuberosity of the humerus on its inferior facet so just to recap we've looked at three rotator cuff muscles so far the supraspinatus infraspinatus and teres minor which all insert onto the greater tuberosity on the superior middle and inferior facets respectively in isolation the teres minor muscle performs external or lateral rotation of the humerus the nerve supply to the teres minor muscle is derived from the axillary nerve the final muscle to talk about is the subscapularis the subscapularis muscle sits on the anterior surface of the scapula if we now remove the ribcage we can take a closer look at this muscle the subscapularis originates in the subscapular fossa which is this depression occupying almost all of the anterior part of the scapula from its origin on the scapula the subscapularis muscle inserts onto the lesser tuberosity of the humerus which you can see here the subscapularis is the largest and strongest rotator cuff muscle accounting for approximately 50% of the cuff strength output when you isolate this muscle it performs medial or internal rotation of the humerus the subscapularis is innervated by the subscapular nerves which is comprised of the upper subscapular nerve and the lower subscapular nerve both these nerves originate from the posterior cord of the brachial plexus so that's an overview of the basic anatomy of the rotator cuff muscles just to finish off this tutorial I would like to go through a few clinically relevant points relating to this muscle group we've described the individual movements of the rotator cuff when each muscle is in isolation however in reality the rotator cuff muscle works as a collective unit to provide dynamic stability at our shoulder joint while we're moving on so when you're thinking about describing the action of this group of muscles they in essence give the head of the humerus in contact with the glenoid fossa during movement they work to provide compression and depression of the humeral head at this joint because of the complexity of the shoulder joint and the relative weakness of this group of muscles they are easily injured there are many injuries which involved this group of muscles which are commonly referred to as rotator cuff syndrome this essentially is an umbrella term which refers to a variety of conditions affecting the rotator cuff sometimes this might be an acute strain or tear of the rotator cuff tendonitis which is common in younger athletes so in sports which require repetitive overhead movements like bowling and cricket or pitching in baseball certain occupations like painting and decorating where there's a lot of overhead arm use can also predispose to tears of the rotator cuff the Communists of which would be a supraspinatus tear the reason this is the most commonly torn is because if you look here at the acromion which is essentially like a roof above the supraspinatus tendon as it passes underneath to insert onto the greater tuberosity of the humerus when you elevate your arm this space narrows meaning it can get pinched inflamed and consequently tear in middle-age and onwards the blood supply which is already poor to this muscle group can deteriorate even further meaning chronic overhead use over years causes a degenerative tear which can be thought of kind of like how an old rope phrase over time and so again the supraspinatus is often most vulnerable to this injury and both of these would present with pain and reduced power with abduction of the shoulder whilst there are several others the other common conditions you might hear talked about a sub acromial impingement syndrome this condition relates to problems arising within this area here called the sub acromial space common pathologies in this area includes supraspinatus tendon itis from overuse or a sub acromial bursitis this here is the sub acromial bursa a burst was just a fluid-filled sac they reduced friction between surfaces and we have many of them throughout the body which served the same purpose so in either of these conditions what is happening is that because the supraspinatus tendon is inflamed or the bursa is inflamed it creates a narrowing of the sub acromial space meaning that when we elevate our arm the inflamed structure the tendon or the bursa gets pinched and this causes pain sometimes neither of these pathologies are the cause of pain and it can be small bony spurs projecting of the acromion which pinches the bursa or tendon below it the hallmark feature of this condition is the painful arc where maximal pain is felt between 60 and 120 degrees of abduction the pain is worst at this range because this is where the subacromial space is most marrow but as any physiotherapist will tell you a lot of shoulder injuries require rehabilitation of the entire rotator cuff particularly in something like impingement syndrome a strengthening the cuff means the humeral head will be better compressed and depressed against the glenoid so you can get more clearance between the humerus and acromion during movement of your arm so I hope that this tutorial has given you a good overall understanding of the anatomy of the rotator cuff if you've enjoyed this detour please give us a thumbs up don't forget to subscribe and we'll see you in the next tutorial

Channel: AnatomyZone

Views: 4,496,517

Keywords: rotator cuff, shoulder, anatomy, muscular, supraspinatus, infraspinatus, teres minor, subscapularis

Id: RaIt79pPfgE

Length: 10min 26sec (626 seconds)

Published: Sun Nov 17 2019