hello everybody and welcome back to another anatomy tutorial today we're going to be looking at the anatomy of the elbow joints specifically on elbow radiographs i'm going to show you how you can approach the elbow in a stepwise methodical manner and then look at a couple of clinical examples to show you why knowing this anatomy in depth and in detail is in fact important in our clinical practice now this is kind of core foundational knowledge that should just be second nature to you it's going to come up over and over again in your clinical practice as well as coming up all the time in your anatomy exams so let's start by having a look at the bones that make up the elbow we've got three long bones we have our humerus coming down to our forearm bones our radius laterally and our ulna medially now there are three joints that are seen in the elbow joint itself we have our ulnar humeral joint here which is a hinged joint it allows for flexion and extension of the elbow there's no lateral medial movement here it's just flexion and extension of the elbow then we have a pivot joint here which is our radiocapitela or radiohumeral joint we can see the head of the radius here has got that nice shallow fossa that articulates with this rounded surface of the capitellum here this is the lateral portion the lateral distal portion of our humerus this is a pivot joint because it allows for supination and pronation of our forearm if you were to actually hold your electron on here and then supinate and pronate your forearm you'll see that the electron on the ulna doesn't move at all it's this radius that's rotating there and that brings us to our third joint which is our radial ulnar joint which is where our radius and our ulna come together here approximately this is actually our proximal radial on the joint and there's a radial notch in this armor that allows for that radial head to rotate smoothly there so we have a hinge joint a pivot joint and our radial ulnar joint there within the elbows it's not actually a single joint we allow flexion and extension and supination and pronation here two different movements in the forearm we can look laterally just to see our from our lateral x-ray we can see our humerus coming down here it kind of becomes uh shallower as we get more distal then we have our radius here and our owner here which actually you can see wraps around posteriorly there allowing for flexion and extension now there's only three bones that make up the elbow joint but each of those bones have different sections that we need to know about and they generally follow the ossification centers of the elbow now i'm going to be making a specific video focusing purely on the ossification centers and the order in which they appear but those ossification centers eventually ossify fuse and make up this complex anatomy of the joint which we can look at here now first looking at the shafts of the long bones before you look at the joint is really important just now you are focusing all your attention on the joint and there's a big lucent lesion here with like a pathological fracture that you miss that's really embarrassing when you have your reports and you're missing a big lesion when you're focusing solely on the joint so it goes without saying let's look at the shafts of these long bones as well as looking at the joint itself now if we go to the distal humerus we know that we are lateral on this side the side of the radius this is our lateral epicondyle here and the larger bigger medial epicondyle on the other side now that middle epicondyle you can really feel and if you kind of push into this space here you can get that funny bone sensation of our ulna nerve running underneath that medial epicondyle then i've mentioned we have this rounded capitellum capitellum small head if you look at a gross anatomical sample of the humerus you'll see this kind of sphere-shaped capitalism a really smooth surface and you can see how that would um articulate really nicely with that radial head because you've got that shallowed out kind of diverted circle appearance of the radial head so we can then say that this section here is our radial head we've got our radial neck coming into our radial shaft you can see this tuberosity here as well which is our radial tuberosity our biceps brachy heads from the bias from our humerus down into the radius inserts onto that radial tuberosity and allows for supination of our forearm there so as it contracts it's because it's onto that medial aspect of the radius it supinates our forearm and you can actually feel your bicep brachy contracting when you supinate your forearm there let's go across to the ulna as we rotate around this image we can see that we've mentioned earlier our radial notch of the ulna with our radial on the joint then we have this process coming up like that this is what's called a coronoid process we can see on the lateral portion here it's superimposed on this radius coming here but our coronoid process comes up like that and as we flex our arm that coronoid process will come into this space which called our coronoid fossa there so that coronoid process comes into the coronoid fossa we can see then that the humerus has this groove here and this section of the humerus here is called our trochlea and the part of the ulna this rounded part of the ulna that articulates with that chocolate is called the trochlear notch now trochlear meaning pulley we've got our trochlear nerve our trochlear muscle in the eye coming around that pulley system here we've got the same thing we've got a circular grooved surface here a circular trochlea got that groove allowing for the trochlear notch to articulate with the chocolate so our trochlear notch of our ulna and our trochlea of our humerus posteriorly we see this process here which is called our olecranon of the ulna and as we extend our elbow that olecranon will then come into this fossa which is our olecranon fossa so we can see even though there's only three bones within the elbow there's multiple different sections our capitalim our trochlea olecranon and coronoid fossa and our medial and lateral epicondyles of the humerus then we have our radial head radial neck radial tuberosity and radial shaft and then on our ulna we've got our olecranon posteriorly our trochlear groove or trochlear notch coming through into our coronoid process and then our on the shaft as well as our radio on the joint our radial notch of the ulna so knowing these features are really important especially in children when those sensors haven't yet ossified but also in understanding the alignment of the elbow which we'll go over in a second so i mentioned to you that we have an olecranon fossa here it's a larger fossa posteriorly because we've got this large electron on as we extend our elbow that that olecranon needs to go into here and anteriorly we've got our coronoid fossa slightly smaller fossa there and these fossils are actually filled with fat so we don't want important structures that can become impinged as the olecranon goes into that fossa so we have fat filling those fossa that allow us to flex and extend and allow that coronoid and electron to fall into those fossa as needed without impinging say nerves or arteries in that space so those are what make up our anterior fat pad here and a posterior fat bed here we also have one more fat pad whereas as we flex our arm this radial head as well will go into a little groove here and there's a small piece of fat and that's our radial fossa which allows our radial head to fit into that fossa and there's a small piece of fat within that fossa there now i want to mention a couple of the ligaments that make up the elbow joint and this kind of becomes more important when we go through an elbow mri and i want to mention it here so that when we get to that over mri lecture you're comfortable with how these ligaments run so we have a medial collateral ligament complex and a lateral collateral ligament complex let's start on the medial surface because it's a bit easier we have two ligaments that extend across the joint we have an anterior band that comes from the slightly anterior surface of this medial epicondyle and heads towards our coronoid process so that's running slightly anteriorly and then we have a posterior band that heads slightly more posterior from this medial epicondyle and heads towards our medial surface of the olecranon then we have a band that doesn't necessarily cross the joint but provides a little bit of elbow stability that comes from the olecranon itself and wraps around to the coronoid process so it's actually staying on the iron it comes from the electron wrapping around to that coronoid process we can see it on the lateral x-ray if we were to draw a ligament from the electron and wrap it around to that coronoid process it kind of allows for uh stability in the lower joint by not allowing that trochlea to dislocate from the trochlear notch so you have an anterior band a posterior band and this middle band that's otherwise known as cooper's ligament or transverse ligament of the medial collateral ligament complex now the lateral collateral ligament complex is a little bit more complicated firstly we have a ligament that wraps around the radial head it's called the annular ligament it wraps around the radial head goes posteriorly there it's got an attachment slightly anterior on the ulna here wraps around the radial head and attaches slightly more posteriorly on that ulna that allows for that pivot that rotation of the radial head without that radial head becoming dislocated away from the ulna then just posterior to that posterior attachment of the annular ligament we have a ligament that extends out from the ulna wraps around posteriorly and attaches to this lateral epicondyle of the humerus that's what's called our ulnar collateral ligament our lateral ulnar collateral ligament coming from the ulna wrapping around posteriorly and attaching to the lateral epicondyle of the humerus then lastly we have slightly anterior to that attachment our radial collateral or our lateral collateral ligament of the elbow that extends and then actually just inserts into this annular ligament here so we've got a really complex lateral collateral ligament complex holding this radial head in place not allowing the radial head to dislocate that way not allowing the ulna to dislocate that way and not allowing this radial head to separate from the ulna itself perhaps most importantly when looking at the elbow is looking at the alignment of the elbow and the two lines that we're going to go over here that are crucial in understanding whether the elbow has its correct alignment or not now you can see with the elbow x-ray there's a lot of superimposition we've got our ulna here and our humerus overlapping here we've got our radius and humerus overlapping here and we have our ulna radius overlapping same on the lateral we've got a lot of humerus that's overlapping itself our coronoid process and our radial head are also overlapping what this does is it makes it difficult to see small fractures because of the superposition of our anatomy and there are a couple of other views that we can do to try and isolate specific bones but often we don't see a fracture itself we just see mull alignment of the various structures so first line that becomes really important when looking at a elbow radiograph is the anterior humeral line so if we were to draw a line along the anterior surface of the humerus through the elbow joint that should intersect the capitellum so if we draw a line around our capitalim here this anterior humeral line should intersect the middle third of this capitellum now often if someone falls on an outstretched arm this radial head will smack into our capitellum and push it posteriorly we'll get a fracture happening here and that capitellum will head posteriorly and this anterior humeral line as we'll see in the case now will not intersect that middle third of the capital it may miss the capitellum or just touch the anterior surface of the capitellum it's really important to look at that anterior humeral line especially if we're looking for a supercondylar fracture here now the second line is our radiocapitellar line we draw a line through the radial neck so if i was to look at what the radial neck here would be through the center of the radial neck is here we can see that radial neck oh let me get that line straight is there it's not our radial shaft which is coming like this it's our radial neck and that should intersect our capitellum our radiocapitellar line that line there should intersect our capitellum the same on the lateral we've drawn our capital m here we can see our radial neck is here shaft angle is maybe slightly different but there's an angle change at the neck that's the line we want for our radiocapitellar line and that should intersect our capitalim there so we have our anterior humeral line and our radiocapitellar line they become really important lines to learn and these actually come up in part ones so often so it's really important to know so let's look at one or two pathologies here we look at our alignment we can see our radiocapitellar line if we go through the neck of the radius not the shaft the neck we can see it misses our capitalim the same on this ap view we've got a radiocapitellar line just clipping it's not going through the center of that capitalim here we've got a radial head dislocation now always when you have a radial head dislocation you need to look at that forearm look for say an ulnar fracture because a radius and ulna form a ring and now whenever in the body a bone forms a tight ring like that if there's one fracture or disruption of one part of that ring often there can be another fracture the same in the pelvis if we see one fracture we often need to look for another fracture because when we disrupt the ring it's often two points of interest that are broken that's just an fyi here we can look at our anterior humeral line if i draw it down here we can see that it misses our capitalim here and here we've got a supracondylar fracture that capitellum has been displaced posteriorly and this is sometimes a bit more obvious in this case but this is sometimes the only sign that you'll see is that that anterior humeral line doesn't intersect with our capitellum and we should then go and investigate further for a supracondylar fracture now here you can see our anterior fat pad and you can see the posterior fat pad up here now i said because that posterior fat pad is deep in that electron fossa we should never see that fat pad this is an indication that there's an effusion in this joint that's pushing those fat pads out of the fossa so if we have a look at that it's what's known as the sail sign here's another x-ray we can see that our anterior fat pad is here and our posterior fat bat is here and what we have is a big joint effusion here that's pushing those fat pads away the fat pads are extra capsular so when we get fluid or blood in that joint it lifts those fat pads out of the coronoid and electron fossa and we can actually then see it on our radiograph sometimes easier to see on a ct how that's worked you can see this posterior fat pad here if i outline it that was sitting within this fossa has now been pushed out by this large effusion here and the same on the anterior side this large effusion has pushed out those fat pads and this is what's known as a sail sign if we think of a mast on a ship here and we've got our two sails coming off known as the sail sign you can see the fracture here through the distal humerus you can see this patient actually has a back slab on so that's it that's the elbow anatomy on an elbow radiograph i've mentioned some ligaments i've mentioned the type of joints and some of the signs and the alignment lines that we need to know and this talk is the first of a couple of lectures on the elbow we're going to look at the ossification centers of the elbow as well as looking at an elbow mri where we can see some more soft tissue detail as well as the bones that make up the album so if you've enjoyed these style of lectures please subscribe to the channel like the video to let me know that you've enjoyed it and as always let me know which anatomy topics you would like to let me cover my list is getting longer and longer and it's perfect i want to make this library of free anatomical content that you can follow along prepare for your exams prepare for your clinical practice and use as a reference whilst you're practicing as a radiologist or a radiographer in the future so i hope that helped and i'll see you all in the next talk goodbye everybody