Anatomy Lec 10 08 14 25

from the last lecture. We have distal radius and ulna. Here the distal radius will have styloid process. The distal ulna will have styloid process. The radius will have two little articulations with couple of bones that we like lot which is the scapoid or the scapoid if you like and the luminate couple of carpal bones. so we discussed this just briefly last time. And then you all know we'll articulate with the radius here at the distal radial joint. All right. So this is cool this is actually kind of cool picture here where they've got the wrist basically snapped off where the radius and the ulna would be. So they this is look like you're looking down the barrel of the radius where you can see the two facetses here for the skoid and the lunate. and then you would get little bit of pocket of cartilage that would fit into this space where the laser is right now. It's called the triangular fibroartilage complex. It's it's basically no yield for our our purposes now, but we'll talk about it next when we do the clinical imaging and it can be relevant for some things. So, distal to our our distal forearm, we'll see our carpal bones. There are eight carpal bones, which we'll actually deal with lot. They're very clinically relevant. Distal to that, we'll see some metacarpals and they're named just like the digits are are named or should say numbered like the digits are numbered one through five. So you have metacarpal one, two, three, four, five, just like that. And then felanges. So the fanges we have proximal, middle or intermediate and distal fanges. The thumb only has two fanges. It's little shorter. So it's missing one joint. So you just have proximal and distal veins in the thumb with just one interfallangial joint. Remember in your fingers you have proximal interfallangial joint and distal interfallangial joint. So, we got little bit more range of motion there. All right. you also, this is not ones we would try to label, but something you might in X-ray. Every last one of us in here has couple of what we call sesimoid bones. Maybe new term. sesimoid bones are bones that form inside of tendons. So, everyone's got them in the thumb. No one escapes these, but there's lots of places in the body where they might have some. Some people might have them, other people might not have them. So if you see hand or wrist radioraph, you normally catch couple of these sesimoid bones which are literally just living inside of the tendon of some muscles. All right, that's good strong start. Let's zoom in on the carpal bones and talk about this. So we've done we've done some x-rays, done little bit of x-raying so far. We looked at the shoulder, look at the elbow, and today we're going to look at the carpals. So you can do wrist x-rays or you do hand x-rays. There's different, you know, series has its own, you know, views that you would collect. so in wrist x-ray, you're going to get usually PA X-ray. So, you can see the the X-rays would hit posterior first, actually, normally, and we'll illuminate hopefully all of our little bones here so we can evaluate them. If we've had, you know, patient come in, they have some sort of trauma or something like this, having pain in and around the wrist. You know, there's lots of indications for why one may order this kind of X-ray. So, we can see the the radius here. Here's the styloid on the radius. Over here we see the ulna and the styloid on the ulna. This cartilage. It's kind of triangle shape. That's why they call it the triangular fibroartilage complex right there. And then distal to that we see our our carpal bones. So we'll start like to think there's eight of them. So think of them as two rows of four. The first two start with the first two. like to start with these because it helps me remember that they articulate with the sc with the radius. So the two that articulate with the radius directly are the scafoid or scaffoid and the lunate bone. Scaffoid lunate. Scaffoid is Greek that means boat. So it's kind of like little boat shape like this. Scaffoid lunate. And notice I'm working medially medially toward the pinky. Medial side pinky side. this is the thumb. So this would be lateral, right? The radius is also lateral and the ulna is medial. So that would be another clue. So see scafoid lunate and then over here see two bones. see the triquetum here and then can see the be sitting anterior to the triquetum immediately anterior to it is this this hyperdense signal here is the pisoform. Popform means p-shaped. So it's kind of shaped like like Everyone knows what is your parents make you eat these growing up. I'm sorry. So for So that's the first that's the first row. scaffoid lunate triadum pisopform. jump up to the next row. Now can see one here with usually kind of bright circle almost oval in it. This is hook feature on this bone called the hammade. So if you look at the hammade here, you can see it has little hook hanging off like that. go lateral to that see the big captain in the middle. This is the capitate and the trapezoid. And finally resting over here on the thumb see the So this trapezium thumb. All right. And little memory device for this one that like to use is down here. So, so long the pinky, here comes the thumb. So, starting where we started, skateboard, lunate, triune, piece of form. So, long the pinky, jump up to the hammade. Here comes the thumb. This can kind of in your mind organize them. Make sure you account for all of them. And would be able to ID these on wrist x-ray. Just make sure you can pick these out. that's good kind of just outline them in there and you get lot of this this is great example when when think of superimposition and X-rays my my first thought is probably to these two bones. So remember X-rays are all compressed onto one two-dimensional image. So as clinician or practitioner of anatomy of some kind you should know that the pisopform bone and the the trium are just superimposed the right signal there. couple clinical correlations with this and these are these are important clinical correlations. one is distal radius fracture. So distal radius fracture they come in different flavors and probably the most famous one is collie fracture. Anyone familiar with this? You ever heard of collie fracture? Anyone have had collie fracture? They're very very very common. So any any kind of fallen outstretched hand can elicit can challenge the radius here distally and it likes this it likes to snap off right there. Okay. So colleague's fracture is distal radius fracture and dorsal angulation of the distal radius fragment giving the individual what they call dinner fork deformity like this. So kind of arm kind of comes up and makes little hump like this kind of like the shape of the outside of fork. Another important clinical correlation is scapoid or scaffoid fracture. So, scaffoid fractures are super duper common. They're there. It's so common that if you order if you're clinician, you ordered wrist X-ray. You're mean, that is the first thing that you're worried about is is skateboard fracture. Of course, you can fracture other little bones in there, but man, this guy likes to break. It likes to break. It's kind of shaped like peanut. It's got like fat front end, an anterior pole, and bit of fatter back end, and little narrow waist. So, it's kind of shaped like peanut shape. And at that waist, it really likes to fracture. So, if you fall, an outstretched hand like you see here, you your radius here, remember, is articulated the lunate and the scafoid. So, they're going to get it. They're going to get lot of that force and you you can fracture the scaffoid. Very common. Now, that in and of itself necessarily isn't so bad because they can go in, they can put some pins in it or whatever. what can happen is very common outcome of of scoid fractures is the development of aseptic necrosis or avascular necrosis. And this is because the scafoid's blood supply is super tenuous here. So, what happens is as the radial artery is coming into the hand, it gives off blood vessel that will go onto the scaoid and you can see it actually recurs. it actually kind of has to loop around backwards like this. So often times since the artery is coming through and the arter and it's giving off its branch and recurs backwards like this. Oftentimes this more proximal element of escapeoid will lose its blood supply and it's it's so bad that it just becomes sclerotic and necrotic literally. So they have to deal with this. They have to deal with this. You'll get really bad arthritis and stuff that sets in. So, avascular of the skateboard. All right. All right. So, just to review, we we talked about this some yesterday because you kind of have to talk about how your fingers and your wrists move in order to understand forearm muscles and what they're doing. But just as reminder so with the wrist, we have flexion extension. So, I'm in flexion now. go into extension here. Flexion extension. Your fingers. We did this. We practiced this yesterday, right? fingers just flexion extension. They can also abduct and adduct. So remember abduction up here at the shoulder, abducting away, aducting is adding it back. So you can do the same thing at your at your hand, but in the hand the the midline that we use to establish the midline for abduction and adduction is the middle finger. So the middle finger is the midline. So if you're moving away from the middle finger, you're abducting. And if you're finger moving back toward the middle finger, then you're you're aducting. Not too bad. Okay. and we we discussed this yesterday, so just kind of reinforcing this point. So you you know, all these things combined, including the thumb actions, can give us some pretty cool and different recognized grips. So precision grip's important one. Power grip's important one, but you know, we're creative. We use all kinds of different grips. All right, so let's start taking the skin off the hand. So we'll just start skinning the hand and work our way down. So we we make an incision across the hand here. see that the the palmer aspect of the hand may have little bit more superficial fascia. Recall yesterday we discussed the dorsom of the hand doesn't really have very much superficial fascia. You would just go mean you just barely peel the skin off. There's really very little thickness of fatty layer. You go straight into the bones and the the tendons and stuff. So if you were to skin the palm of the hand and like said yes the palm of the hand is is lot. It's lot. That's why we have whole lecture for it. So we just crack it open here just slowly and look on the underside. We see this sort of guess triangleshaped fascia called the palmer aponurosis. So the palmer aponurosis is this triangle shape. It's immediately under your skin on your palm and it's covering up lot of the goods there. Okay? It's covering up lot of the vessels and stuff. You can see them poking out hiding there underneath like that. on either side of the palmer achonosis, you'll see some muscular prominences. So if you're over here on the thumb side, you would see big wad of muscles called the phenar eminence. Remember the for your thumb. And then over here on the pinky side, you would actually see the hypoththenar eminence. The hypoththenar eminence dedicated to the pinky and the theore imminence dedicated to the thumb. before you saw that, you might also see little tiny guy, no yield really, but completion set little tiny muscle called pomeis brevis and we'll talk more about palmaris brevis and just like doing this so we'll talk more about palaris brevis here we'll talk about this this muscle in your neck guess if you ever do this like are you kind of like you know this muscle you probably you use it right it's called the platisma muscle you use it to like pull your skin tight it's actually inside of your skin it's in it's like inside of the superficial fascia of your skin it's not under deep fascia like your biceps Well, palmeris brevis is kind of the same way honestly. So those those muscles, the platisma muscle, pomeis brevis and some others, they're remnants of what's called the paniculus carnosis. So if you're if you're familiar with like if you've been around cows or horses or anything or if you've been here long enough and you just drive down the highway, you'll see some horses out in the field or whatever and you see them twitching their skin. You watch them long enough, you'll just those kind of they're doing that to kind of shoot the flies away. It's because they're covered in muscle just like this. They have all like platisma over their whole body. No yield. Okay, I've gone too far. That's that's just fun story. All right, so moving on. Let's dive into these eminences. So remember for the thumb the thumb we have the thear imminence or the thear compartment. And there are three muscles in the thear compartment that are just dedicated just thumb movement only. Here we'll have muscle for flexion. This is flexor policus brevis. Remember policus is thumb term here referring to the thumb. So we saw flexor policus longus in the anterior forearm. So here's the brevis. You'll see an abductor. So this is abductor policus brevis. These two. So flexor policus brevis abductor policus brevis. And in lab what would do is would cut this tendon of the abductor policus brevis like this. And would flip it back kind of like they've done here. And underneath you can see the opponent's policus. and opponents as you might could deduce is helping you with opposition of the thumb. So opposition is remember that combination movement with your thumb where you swing your metacarpal around and you can ab and flex at the same time. So it's big combination movement. So the pad of your thumb is facing your palm. So this this this is opposition. So we have dedicated muscle for that as well. All right. So these three muscles of the theorinance are innervated by the recurrent median nerve. We like this one. The recurrent media nerve is super duper important nerve and it's branch of the median nerve. In fact, can see lot of these little nerves entering the palm of the hand here. Most of them except for this one over here. They're just derived from the median nerves and more on that later. And very important branch our eminence is is that recurrent branch. again recurrent because it's coming back from where it came. So the media nerve will be passing through the carpal tunnel spraying off these sensory branches and it'll throw branch that goes backwards into the theor compartment. it's often referred to as the milliondoll nerve milliondoll nerve going to the thumb. It's called the million-dollar nerve because if you're hand surgeon and you accidentally cut your patients for current media nerves, you're going to be paying them million dollars because they're going to be disabled. Like losing losing access to most of your thumb movements would be life it would be for anybody doing anything. you would just not be the same anymore. So it's not it's not huge nerve. would say it's about as as big around as this cable right here. Actually the recurrent branch of the media nerve. It's not that big. All right. So another little sidebar on here just emphasizing the thumb. Look at this. Any any guesses about what this this guy may be? Yeah. wouldn't say Dr. or something. Don't tell him said that, but you're right. It is an orangutan chimpanzeee over here. so we can see that their thumbs are Yeah, mean, this one maybe little more prominent, but yeah, they're tiny. They got these tiny little tiny phenomenances like that. And just didn't I'm not trying, but just want you to have look at my thumb. Now, that that is thumb, buddy. That is thumb. If you look at your thumb, you can see this big mass, this dedicated giant muscle mass that we have down here for moving our thumb around. So, it's super important, you know, and that the&r imminence is actually what's making up all that bulk right there. And the reason kind of talk about the apes here for second is for clinical reason actually because damage to the median nerve, if you leion the media nerve or if you specifically lesion the recurrent branch of the media nerve, then you would lose those muscles. And after muscles go for while and they're not getting neural signal, then they'll atrophy. They go undergo disuse atrophy like this and they'll just die. They'll start to die off and shrink like this. so that happens and they call this injury apan because it makes it makes your hand kind of look kind of like flat unnarrinence like we saw on the orangutang just minute ago. Yeah. Since the chimpanzees and their and the apes the chimpanzees and the orangutans, they're thumb is like smaller. Can they still have the same movements we can? that's actually good question. don't know if they have if every one of these species all have the same musculature as we do. They do not have the same same range of motion and they're very very poor opposers of their thumb. So, don't know if they have muscle that's called opponent's policy. Maybe they did. don't know. Because it's smaller, they can't do that. Smaller, weaker. So, they're very hook grip like oriented. They they'll just hook like this. Their thumbs are kind of just along for the ride. given the ability to oppose, make like precision grip. Yeah, that's that's something we would be lot better at. Yeah. have question. This is just kind of my own curiosity. my thumbs are not super they only go this far because of traumas in my hands from volleyball. And so was just curious when we talk about opposing it's talking about this but like how like if there's constant trauma on it will that is that more of like muscular issue or like it's hard to say. mean if your theorem look okay but they're still pretty bulky. Yeah. Bigger though. Yeah. mean don't know. Maybe it is mix then. would be surprised if he had nerve damage from that. Maybe it is joint related or some sort of stiffness or something like that that's limiting your range of motion in your joints. don't know. That's just my that's my guess. guess from 10 feet away. That's my guess. don't know though. It's good question. Could be little bit both. Who knows? okay. So with with the APAN, so just just remember median nerve injury. Median nerve injury or so of course if you leion the media nerve way up here in your elbow, this person will develop an apand, right? because the recurrent branch which is downstream of that will be affected. but it could just be an iatrogenic you're in the and you or whatever and you develop this. And this is not as common anymore particularly in in places where people have great access to health care because if they have persistent carpal tunnel and it's you know in in areas where they healthcare is abundant and easy to access they're likely to go get that treated right that median nerve lesion in the carpal tunnel treated and they wouldn't develop this. But mean definitely definitely people could develop this if you just went on with chronic carpal tunnel syndrome and media nerve compression. it would would end up being the same kind of injury. so that is that's the big takeaway. So atrophy the theorem minutes and the the thumb will also kind of fall out of line. So it loses its tone. It may fall kind of back like this. So it's more in line like like an apam. Yeah. So long story short, if you get into any kind of guess physical competitions with orangutans or chimpanzees, it would need to either be longdistance running or better longdistance runners. That's that's kind of our jam or thumb warp. That would be the those are the only those are the only two physical competitions you can beat at Champion. All right. Pretty good. All right. So, let's move on to hypothenance. So, the hypotheorance is dedicated for the pinky. And if you notice carefully, the name scheme for these three muscles of the hypoththenar eminence are actually mirroring the name scheme for the three muscles in the thear. So remember in the theorinance we had flexor for the thumb flexor policus we have an abductor and we have muscle of opposition where you actually have the same thing over here for the pinky you have an abductor digy miniame for the little digit you have flexor digy mini brevis although there is no longest and muscle of opposition an opponent's digy mini right abductor flexor opponents and this is dedicated to the little dig so you can't oppose your little digit as well not not quite as well but you're able to swing the metacarpal for the fifth the fifth digit around like this to kind of oppose the thumb. So they call this opposition. Now unlike the other the media nerve the recurrent branch of the media nerve intervating that theor nerve is actually getting in getting in on some of these. So the nerve specifically the deep branch of the ular nerve will intervate this trio in the hypoththenar compartment. You don't know this is all my like you know like all my social references are slowly dying and have to replace them with more and more relevant things. All right. All right. So we've done it. So we've gone through the theorem eminence. We went through the hypoththenar eminence. Let's look at some deeper muscles in in the palm. So you you can see lot of the musculature and even some of the arteries and everything have been dissected away. And can see the media nerve is revealed inside of the carpal tunnel. this little tunnel here and can see they've illustrated in its recurrent branch remember that's associated remember the hypoththenar eminence over here is associated with the deep branch of the owner so let's trace the owner up here's owner owner owner it's traveling with its artery goes up up like this and you would see the owner have deep branch which goes down and kind of curves you can see it hooking into the deep hand and along the way the owner nerve the deep branch of the owner nerve would intervate these hypothear muscles You'll also intervate muscle that's all the way over here on the thumb side of things. Now, this is thumb muscle, but it's not an athenar muscle. So, there's bit of distinction. this is muscle that's involved in adducting the thumb. So, this is adductor policus and it is innervated by the deep branch of the nerve. So, don't get confused. Even though it is policy and it is over here on the thumb side, it actually doesn't get that recurrent media nerve. It just gets the deep branch of the nerve. So if you're in an abducted position kind of like this, you would use adductor policies just to bring the thumb back to neutral position. Sorry. Other things you'll see in the palm, you'll see what are called inter oi muscles. This is good name for it. So inter means between. Oius referring to the bones. So these are literally between the bones in your palm. so the interosi muscles there are three palmer interosi and uhated by the deep branch of the nerve as well. So what are these interosi muscles up to? think it's easiest to think about them all at one time. so for the the two sets of interosi muscles you have set on the front there's three on your palm. So palmer interosi then you have four actually on the back side dorsal interosi. So what do they do? So the the memory device for remembering their function is dab and pad. Dab and pad. So dorsal interosi abduct and palmer interosi dd duct. So if we go back could figure. So here's our thumb. It kind of makes sense that on your second finger here, if you're going to duct this back toward the middle finger adding, remember the middle finger is the midline here in the hand. that this palmer interi would pull this proximal face toward the middle finger. Okay. Similarly for these for four and five. So pulling it toward the middle finger. So there, if you're in an abducted position with your fingers like this and you're going to add these digits back toward the midline, you would use those palmer interosi. And on the other side, on the flip side of things, these are on the back of your hand. And you can you can palpate these. These are easy to feel. These are really the only muscles that you have on the back of your hand, but you can feel like big wad right there. that's the first dorsal interosius muscle. You can feel any kind of soft tissue in between your bones. Those are all dorsal interosia. So the dorsal interosi are doing just the opposite. You have one dedicated for the second digit here which will pull the index finger away from the middle finger into abduction. The middle finger actually is too dorsal interosi. And the reason is it's abducting. The middle finger is is by definition the midline guess you could say. So it's only ever abducting. It's only ever moving away from the midline. so you have two one on either side of those that would from side to side. and then finally fourth one way over here for your fourth digit. Okay. So that would be the abductor for your fourth digit. And then you have an abductor for your little digit. Abductor digit minime. But remember the abductor digit minim is component of the hypoththenar compartment which hangs off the side of your hand. So you can test the owner nerve this way. So this is actually not an uncommon clinical test. You can sort of isolate the function of the nerve knowing that the nerve intervates the dorsal and palmer interosi by asking them to like grip like this. Grip piece of paper or even spread their fingers against your resistance. So if you were to kind of fingers like this and give them little bit of resistance say okay spread your fingers as wide as you can then you're testing and also at the same time testing the nerve which intervates them. All right, almost there. There's lots lots of muscles in the hand. Lots of muscles. but these are cool. These are interesting muscles and they have cool clinical correlation here. The lumbercal muscles. So, lumbercale is Latin that means worm worms. So, whenever you dissect the hand, the lumbal muscles, they do gen they genuinely look like little earthworms in between your tendons. You have four lumbrical muscles. And what's what's interesting about the lumbal muscles is their origin, okay? where they're pulling from is actually the tendon of the flexor digitorum profundus. So remember that from the last lecture flexor digitorum profundus flexing these digits down. So the these four muscles will actually arise from the tendon of flexor digtorum profundus they wrap up your fingers just little ways you see here and they'll insert onto that extensor expansion on the back of your finger. So kind of an interesting little muscle. something to note about them, some of them are unipinate, meaning they're just like one feather muscle. Some of them are bipenate, looking kind of like you know, two feathers muscle if you will. and very very important point, the most important point probably is that they're they receive different intervations. So the first and second lumbar muscle are innervated by the median nerve. Lumbricles three and four are innervated by the ulner nerve. So what do the lumbrical muscles do whenever? So they're pulling from the flexor digtor profundus tendon. They're wrapping around and inserting onto this extensor expansion. Remember what we talked about yesterday? The extensor expansion actually works by splitting into different slips. So you have this central slip that will go over the top of your proximal interfallangial joint and then you have these little collateral slips that go over the top of your distal interfallangial joint. But you can see that the lumbar's tendon is actually crossing the MCP joint or the metacarpo felangial joint in the front. So if you think about the physics of this if you will whenever the lumbar lumbrical muscle is pulling it actually flexes your MCP joint because it's crossing on the anterior vententral surface of it. But since the extensor expansion via its two slips here crawls over the backside of the interfallangial joints, it will actually extend your interfallangial joints. It's weird to think about. So it's one muscle having opposite actions on different joints. so this is good picture to kind of understand what the lumbercles are up to right here. So if you're doing just this where you're flexing at the MCP joints but your IP joints are extended like this not flexed but extended then you're you're simulating the action of the lumbar muscles. Okay we remember dual intervation here lumble one and two median lumble three and four is lot so big muscles that we have in the palm of our hand. couple of things I'll point out is the ner nerve man. Wow just coming in clutch here. So all this is owner. Two of our lumbical muscles are owner like this. So when think about intrinsic hand function, intrinsic meaning the muscle begins and ends in your hand. It's not coming from your forearm and in you know going into the end. When think about intrinsic hand muscles, my first thought is owner nerve. mean the owner nerve is the heavy heavy hitter here. What do is just try to remember the outliers. So the outliers here are the first two lumbricals are the median, right? And then the thear muscles. So the theor muscles are also medium. There's nice patterns to be picked up on there. All right, we did. So we talked about the muscles. Let's move on to the arteries. So the arteries in your hand, we have two arteries in the forearm. As you remember from the last lecture, artery on the medial side, radial artery on the lateral side. the hand they actually will form two loops or arches, two arterial arches. So the artery will come up up up up like this. And if you were to carefully dissect away that palmer aponurosis, that little triangle fascia that we saw up front. If you carefully dissected that away, then you would reveal the superficial palmer arterial arch. That's what we see here. So the superficial palmer arterial arch you can see is got some contribution from but you actually have the radial artery giving some contribution like this and and most people unless you have incomplete arch will have complete little arch of blood supply here. Now coming off the arch you have what's called common palmer digital arteries. So common palmer digital arteries the name common should sort of trigger your thinking it's about to split into something. The common palmer arteries will split onto adjacent fingers as proper palmer digital arteries. So tag up here on the finger bone is proper palmer digital and know the adjacent fingers proper palmer digital. They both came from common palmer digital down here. Okay. So that's the that's the arrangement for how this works. Getting the blood all the way out to the tips of your digits. this is dissection where you can see the thear eminence here laterally hypoththenar eminence here and can see some of the tendons maybe some of the flexor digtorum tendons in there and they've injected the arterial system with latex so you can see this bright red your arteries don't really look like that unfortunately it'd be nice if they did because it'd be easier to tell them from veins but but they injected it with red latex to exaggerate that superficial palmer arterial arch so you can see coming away from those like this one for example would be common polymer digital and can just barely see actually right here's good one can see the split into adjacent proper palmer digitals right there little tin nerves the median nerve branches there all right so why is this important so one reason it could be important is Allen's test anyone heard of Allen's test been in around the clinic or prescribed or something you may have heard of this so Allen's test is test of your collateral blood flow and its integrity. So don't know if the sound is on here. We'll see. The sound is not on. So I'll I'll I'll narrate here. He's talking. Let's go back. Sorry people on the other side of the wall. It's coming. belly. Maybe let's try this. So, he's going to explain what this is. And what this is is you testing the the integrity of the arch on the inside of your hand from both the and the radial perspective. So, if you compress the radial and the artery at the same time, your hand will just blanch, right? It's not getting any blood supply. but if you wanted to test, for example, to see if the ulner artery has good blood flow and it's patented, it doesn't have big blockage or, you know, make sure your arch is complete, you can leave your finger on the radial and just take it off the ner and the whole hand should bl right because there's an arch. There's like giant anastmosis between the two. So, the hand is the and radial arteries are compressed. is there's not much blood flow because the hand is pale release nicely indicating sufficiency of the artery system. Cool. And this is pretty common thing they'll do before anesthesia will do this beforehand. If you have heart procedure, they'll do this beforehand because if they want to access your radial artery, which is not uncommon if you have heart procedure or something like that, they're going through your vessels and they want to play around with this radial artery. They can't off your radial artery for, you know, clinical purposes that your artery is not going to help diffuse your hand, right? The artery's got to be there to back it up. So, reasons why it may not back it up, one is like thrombus. So, if you had thrombus or something in there that's blocking the artery, of course, that would that would compromise your blood flow to your hand. Another reason why you may have compromised blood flow in that case is if you had an incomplete arch. see this lot in the lab, like in the anatomy lab. if the arch doesn't come fully together and connect then they're technically separate entities. You have radial artery profusion and an artery profusioned. So you can see in this in this individual they have an incomplete arch. So you can see they're compressing the owner artery and it's only but the radial artery is still filling but only part of the hand right and then just the opposite. Does that make sense? So they do this they do this lot actually. Balance test is quite common. Okay. digging more carpal tunnel. So carpal tunnel is high yield area in the wrist and hand. We have to be familiar with this. We we talked we alluded to it little bit yesterday talking about the tendons of some of these muscles. So what is the carpal tunnel? So the carpal tunnel is tight little space that's basically bound by your carpal bones. So all you remember your carpal bones that we just went over. So along the pinky here comes the thumb. They are. And they kind of curl like this. say kind of they they actually curl lot. So whenever you're in the lab, you can stick your if you get the tendons out, you can feel your carpal tunnel is deep pocket, buddy. mean, is it is deep deep pocket. Still, unfortunately, not enough space to go around in there. And the carpal tunnel is covered on top by the flexor retinacculum. So this flexor retinacculum would sort of act as the roof over the carpal tunnel. So what's going through the carpal tunnel? So what's going through the carpal tunnel is nine tendons and one nerve. Nine tendons and one nerve. And can see them packed right in there. Okay? They shouldn't be any arteries. So you have the four tendons of flexor superficialis flexor digitorum superficialis the four tendons of flexor digitorum profundus and flexor policus longus if you remember that one flexing the thumb. So these these nine tendons collectively pass through the carpal tunnel and they do so along with the median nerve. So that's actually how the median nerve enters the hand. It does so under the flexor retinacculum and through the carpal tunnel just like this. The nerve on the other hand is not. It actually passes over the top of the flexor retinacculum. So if you had carpal tunnel syndrome any problem in there where you don't have enough space to breathe in there the nerve would be it would be fine. It would be unaffected. so of course the the syndrome here is carpal tunnel syndrome. So with carpal tunnel syndrome, you can see this cross-sections been cut right right across the carpal bones and the flexor retinacculum. Here's the flexor retinacculum. Here's our nine tendons like this. And you would have the median nerve tucked in there with it. So little more anatomically accurate would be something like this. So there's the carpal tunnel. There's little extension here of tissue that goes over the top. It's not part of carpal tunnel here. It's different tunnel that the owner nerve will enter. It will be over the top of the plexor redneck and we call it geon's tunnel. So gon's tunnel is how enters the hand and then there's little side passage for flexor carpy radiialis actually. So the carpal tunnel syndrome so this is very very common. So the patient history could be relevant. So this person they may have some sort of job where they're you using their fingers and digits lot. Classic way to be to be written is you know there's some sort of it's there's typing lot. So it could be anyone taking lot of notes or you know something like something like this. Maybe you guys you're taking lot of notes. So so so try to lay out the note takingaking maybe that's the recommendations but it's super common. It's the one of the most common msk complaints is carpal tunnel syndrome. So what happens if with this overuse in there the synenovial usually what happens is the synenovial lining on the inside it gets irritated. So all of this kind of blue stuff, remember they're surrounded by the synovial lining, gets irritated and invites lot of swelling and immune response in there and you just don't have any room anymore. And the tendons, mean, your tendons are still going to work and they produce lot of force, but in there anymore, your nerve does not like it. So your nerve can get squished. And if you had median nerve lesion right here, lesion, guess, is good word for this. then you're going to expect downstream media nerve symptoms which as you know may affect the thear imminence. So they may have some amount of thumb weakness. the most common complaint is sensory loss or sensory disturbance guess you would say. And remember that would be over the median nerve distribution in the hand. So the cutaneous distribution of the median nerve in the hand remember is money. Remember median is money. So it'd be over the anterior surface of your thumb, first and second digit on the front side, and then maybe down into the palm here, maybe little bit. Palm's oftentimes spared in carpal tunnel syndrome for for reasons. There's little tiny there's actually little tiny nerve branch that jumps off of it. I'll draw it in. So before it goes into the tunnel, it actually gives off little branch like this that goes into your palm skin. So sometimes your palm is spared. All right. So just consider that patient profile. They come in, you got their history, you know what they do for living, you got their major complaint here, sensory loss, you know, maybe some thumb problems. You can eliminate nerve, you can eliminate radial nerve. You're worried about the median nerve. So what about the nerve? So the nerve goes through tunnel or the tunnel here and we talked about it giving off its deep branch earlier and we know the deep branch of the nerve is the heavy hitter for intrinsic hand muscles. When you think intrinsic hand muscles, your next thought is deep branch of the ular nerve. And you just remember the exceptions to that rule, which are the the median nerve. also importantly is you'll have some cutaneous branches. So the cutaneous branches of the ular nerve, recall we'll do the fifth digit and the medial half of the fourth digit along with the medial palm as well. so this part of your hand here, this is the palmer surface of your hand, fifth digit, half your fourth digit, and the medial aspect of the palm. All done by All right. So mean you got carpal tunnel lesions and you can get gillon tunnel lesions as well. So these are little less common but they do they do pop up. mean they are pretty bore relevant. They're in DRS and mean you'll see them out there. So it's good one to be familiar with. So Gon's tunnel here you can have similar kinds of issues maybe thickening of the retinacculum or something like this that can cause nerve enttrapment inside of Gon's tunnel. very very common way to to to see this in clinical presentation is actually if you have been leaning your leaning the medial aspect on something for long time. so we have we have student now was first year student think probably has this from based on what he describes taking. So sitting at his desk he was like guess the way he was leaning on his desk the medial part of his hand here was just compressing and just nerve symptoms. So they you can also call this handlebar neuropathy. of cyclists sometimes will complain of this because they rest their the the medial aspect of their wrist against their handlebars and that just compresses the nerve in in the thumb. So what if you have proximal nerve lesions? So if you have proximal nerve lesion or lesion that's up higher maybe nerve lesion in the cubital tunnel or something like this that can happen as well. That's another issue you could have. So if you have neuropathy like this, you might you might or you might not get super super bad symptoms. mean, if you had if you had like full nerve lesion, of course, everything downstream of the nerve, motor and sensory would be affected, but these are usually little little bit more transient. if you had more violent nerve injury, maybe you had medial epicondile fracture and the cubital tunnel was compromised and the nerve was severed like this and you lost all then you you would end up like this. So they call this the owner claw. The owner claw. And the owner claw kind of looks like the sign of benediction from yesterday. kind of looks like the sign of benediction, but it's little different in that the it's not an active. So, you wouldn't have to say, "Okay, patient, make fist." And that would give you the sign of benediction. You're associating that with media nerve injury. The patient would upon receiving this, if they just fresh out of the car accident, their older nerve is just less. They would just show up like this. They would show up. If you notice the difference here, there's slight hyperextension of the MCP joint. So, the MCP joint is hyperextended little bit. whereas the sinoid you know you asking them to flex down. So this why does this happen? So the reason this happens is because the lumbal muscles remember told you that was important. So the the medial two lumbrical muscles three and four which are dedicated to digits four and five are denervated because you you leion the nerve right and whenever this happens the extensor digitorum muscle is pulling unopposed. It's pulling unopposed. So, it has no other tonic kind of competitors. So, if were to ask you, just just think with me here for second. If were to ask you to use your extensor digtor muscle on the back of your forearm, the one that goes out to the back of your digits to extend them. If were to ask you to show me what you think that does whenever it fires, show me what you think it would do. Anyone? Extend. Extend. So, extensor digtorum. These are good guesses. Yes, this is totally reasonable. So, extending the digits is where you might go with this, right? And that's that's not bad. That's that's pretty big what it actually does if you were able to fire extensor dig digittorm all by itself is you would make just claw like this. You need lumbercles to do that. Yeah, you need lumber. It's an intrinsic hand function. So, getting from here to here, you need lumbercles. All right. And this is the explanation for the the clinical signs and symptoms that you see in clawing. So if you lose lumbercles four three and four associated with the ring finger and the fifth digit the instant your nerve gets cut and your digits like this then there's nothing to keep them from clawing like that on on four and five. Does that make sense? So that's clawing. Any kind of nerve lesion could could end up this way. this also explains if you remember all the way back clunky's claw remember the lower brachial plexopathy. So remember you had the herbs palsy with C5C6. So clunky's pulsey was full claw hand. Remember so these babies they come out and have this little claw. That's because C8 and T1 are the spinal levels that go into all the lumbercles. So in that in those babies they lose all their lumbercles like this. Other signs and symptoms you may see in this patient. If they damage their owner nerve upstream and it's busted, what kind of sensory symptom would this person complain of? Good. Yeah. You could also take the same person if you're suspicious of big lesion here and say, "Okay, can you feel this?" They they wouldn't, right? If it was full lesion, they could not feel that. And then the medial half of their fourth digit. You could also test some other intrinsic hand muscle. You'd probably be convinced at this point, but just in case, you could you could you could test the resist my fingers. So, abduction against resistance. Remember the interosi muscle also owner nerve. So, lots of different potential pieces to put together. If they were like to put their hand on the desk, like they wouldn't feel that at all like for the for the last digit. Yeah. So, if they so they would have no cutaneous sensory information at all. So any kind of pain any temperature changes so thermal receptors would be gone propriceptive would be gone you know for all that. So yeah right cooler clawing any questions on claw right we're getting there we're getting there the last few slides are summary slides to more or less help you prepare for some of these nerve injuries so almost done with the hand. So we talked about the superficial palmer arch one coming from the ulner and one coming from the radial here to make our superficial palmer arch. Just for completion sake there is deep palmer arch. So essentially whenever the two coming together like this to make the superficial palmer arch they really split twice. They really make kind of two connections. One arch is superficial and the other arch is deep. So you can see in this image the deep palmer arterial arch. The deep palmer arterial arch is little more proximal in the hand and it's deeper as the name implies and the way it's formed is actually from the radial artery which enters the snuff box. So it's about to enter the snuff box right here right the the anatomical snuff box passes behind so the dorsal surface of the thumb and the radial artery will actually terminate by giving off dedicated vessel for your thumb. It's called princeps policis and one for the lateral side of your second is and you can see that part of it just continues on to make one continuous loop with the ulner artery. So at the end of the day and radial making two loop connections superficial palmer arterial arch and then deep palmer arterial arch. Recall that the superficial palmer arterial arch would be the one that generates the proper polymer digitals and ultimately the common or excuse me common polymer digitals and ultimately the proper polymer digitals. So this is an angiogram here. So you can see this. So here's our superficial arch and here's the deep arch. Yeah. So someone that has something like this, that arch isn't made. It's incomplete. Yeah. Yeah. Actually see lot in lab. It's not it's not terribly uncommon. So guess this is why the Allen test is so important because it is very prevalent. It's not the majority morphology, but it is very significant minority of people will have this. All right. All right. So, that's really it about take the last few slides to maybe prime you to start studying little bit. think the nerves are probably the hardest part of the exam. They are think in MSK. Let's do little bit of quick recap on some of the nerves, where where to where to look through them, where to pay attention. These are great summary slides for some of these. So, starting with median. So, we'll start with the median nerve and we'll just address some of these points that they're passing through. So, remember the the median nerve is going to be coursing in the bicipital groove here. So it's going to be coursing in the bicipital groove coming down entering the cubital fossa. So it's going to be entering the cubital fossa and there should be the brachial artery. so it travel with the brachial artery in the little bicipital groove. So just behind the biceps muscle it enters the cubital fossa. So remember the median so player in this tant relationship tendon artery nerve. So that's the nerve biceps tendon brachio artery median nerve. it's invating lot of these muscles in the anterior forearm. So all of not all of but almost all of our wrist flexors and lot of our finger flexors are done by the median nerve. It would it would provide so it would continue on go through the carpal tunnel. So it goes through the carpal tunnel like this. Remember it's going to intervate the phenar muscles and you can even see better illustrated the first two lumbricals. So there they are. So done by the median nerve and remember median is money. Median is money. So this is the cutaneous sensory distribution of the median nerve. So ears are always up for cutaneous sensory findings. It it's very it's exclusive to the nerve, right? It can't be any other nerve is doing this. And our important clinical correlations that we mentioned for the media nerves the sign of Benediction. The anterior interosius syndrome. Remember trying to make the okay sign. Okay remember this would be flat if you have an anterior interosius nerve lesion. carpal tunnel syndrome of course and then the then the apan the median nerve also does come out to these digits here and does your nail beds. So if you actually look at the the median nerve distribution here kind of curls over and does your nail bed. All right, so that's median. What about So kind of like median, the nerve is just basically passing through your arm to get to your forearm. So the owner nerve is passing behind the elbow joint through the cubital tunnel if you remember coursing in the cubital tunnel between the medial epicondile and the electronon. It gives off couple of muscles here. So remember the flexor digtorum profundus gets is dually invated. Remember that dual intervation for muscle is kind of rare but the medial two digits done by the nerve here for flexor digtorum for fundus and also flexor cararpis for the nerve. The older nerve continues on like this. It doesn't do any just like the media nerve. It doesn't do any sensory intervation over the forearm. None. It's just passing into the hand here. Heavy hitter for intrinsic hand muscles, right? Huge. So the the the deep branch of the nerve is doing most of your intrinsic hand muscles and along with the cutaneous distribution here. So it does the medial side of the hand both the back and the front digit five on the back and the front and about half digit four on the back and the front. All right. So nerve and couple of couple nerve clinical coralates here. So this is nice little summary. So we got nerve or sorry cubital tunnel entrapment some sort of cubital tunnel problem clawing like we see here. bunny bone of course is kind of fun one. Gon's tunnel. So you got issue in gon spinal and handlebar neuropathy. So patient their their history can be relevant often times with your differential. So radial nerve distribution radial nerve is wrapping around the humorous. Remember it's wrapping around the midshaft of the humorris not shown here. We associate that with the wrist drop injury. it's wrapping around the lateral epicondile kind of like candy cane stripe. Splits into superficial and deep branch. The superficial branch of the radial nerve will go all the way to the hand here and provide cutaneous sensory intervation. So this is the territory of the radial and there would be little seam here where the ular nerve would take over. Recall the deep branch of the radial nerve will intervate couple of muscles most of the muscles back here. The continuation of the deep branch of the radial nerve which is the posterior interosius nerve. so all of that would be kind of immaterial if you had lesion for example like right here. If you get lesion like way up here or you midshaft hummeral fracture or something like that, everything downstream of that is going to get it. All right, so that's radial. this is just summary slide showing you the hand. So you can see the the cutaneous sensory distribution over the forearm or the distal forearm and then the hand. So palmer surface of the hand remember medium here in yellow on the medial side still on the medial side on the dorsome of the hand and then radial on the lateral dorsome of the hand. Okay, just another summary. One way to think about the forearm form needs more love think. But so this is this little if you were to take section through the forearm like this. You took section just like that. This is essentially draw this little PowerPoint shape. So there's three cutaneous nerves for the forearm. You'll have this if this is anterior and this is posterior. You have lateral antracutaneous nerve and medial antibrachial cutaneous nerve. So lateral will be here in green. That's derivative of muscularcutaneous and medial from the the medial cord. Then you have posterior antrachial cutaneous nerve which comes from radial and that would be on the back side. So if you slice all the way through the forearm just like this. You have these three nerves covering the that's just the skin territory, right? That's just the skin the muscles on the inside. that's different story. All right. So we'll play one game together really quick and I'm keeping little bit. this is but this is just just follow me. Just let this wash over you here one time. So talk lot about these maps, right? These cutaneous nerve maps. And say if you're good at this, then you know you know what you're doing. And that's that's true. If you are and you have and you're dealing with peripheral nerve lesions, then you do know what you're doing. You're doing okay. but remember talked about dermatones as well. Remember this the zebra stripe kind of pattern. So how do you know when to use one or the other? When is when is the peripheral nerve chart relevant? When is the dermatone chart relevant? So let's do thought experiment together here. So let's consider nerve the muscularcutaneous nerve. The muscularcutaneous nerve via the mixing of the brachial plexus is derived from C5, C6 and C7. Remember three musketeers assassinated. Yeah. So the three musketeer. So from C5, C6 and C7 they mix together via the brachio plexus. There's lot to be said about that part, right? And they form the muscularcutaneous nerve. But said what does the muscularcutaneous nerve do? go you would say its motor branch would go to the biceps brachi, to brachaiialis and the brachiialis muscle. Biceps would do flexion of the elbow and supenationalis would do little bit of flexion at the elbow maybe little little bit. It's not that much. And then the brachiialis muscle would do flexion of the elbow exclusively. Okay, so that would be the muscle's job. And you should also know the muscularcutaneous nerve has that lateral antirachial nerve. lateral interracial cutaneous nerve branch coming off of it there in green. So it does little bit of cutaneous sensation as well. So if you put lesion you put lesion in the periphery you lesion peripheral nerve this is what you would expect to see. patient comes in, you've damaged biceps, coral brachiialis, and brachiialis. Where their injury is at could be relevant, right? They just come in with this giant laceration or something. They're like, "Okay, what's in the periphery?" if they come in and they're, in this case, their elbow flexion is nearly busted. They would have basically no elbow flexion. Maybe little bit of brachio radiialis, but not really. mean, so if you were to do both sides, you wouldn't have to do both sides. Just like one side is going to be absolutely busted, zero elbow flexion. And you can test their you can test their forearm. You can say, "All right, can you feel this on the medial side?" "Yeah, it's okay. What about this on the lateral side?" can't feel that." "Okay, what about your thumb?" "Yeah, can can feel that." That would be median nerve, right? Okay. So, then you you've isolated that. You pin that down on the muscular cutaneous nerve. In this case, knowing the peripheral nerve cutaneous chart helps you. That's good. You want to know that. Now, let's just drive the lesion up higher. Let's say you have C6 nerve root lesion. You may say, "Well, how do you get C6 nerve root lesion? Where's the C6 nerve root? That is like in here. Like it's all the way up against your spinal cord, right? So, how would you get this lesion from what you know? Fracture. Yeah. So, you have cervical fracture. the one we mentioned in lecture, the one that comes up lot is the discs, right? So, in Yes. Intervertebral disc herniation, that's usually that's usually the one. But yeah, mean, if you got spine tract or even tumor growing off your spinal cord or something like that, it would that would that could possibly affect it. So, With this in mind, then if you leion C6, think if you leion C6, could this person flex their elbow at all? Well, you could be. Yeah, because C5 and C7 would be helping little bit with that, right? So, would it be weakened? Yeah, little bit. It would be weak. Maybe you do both sides and you're like, "Okay, little bit weak there." What the dead giveaway would be about their root lesion would actually be the dermatome chart. Yes. Yeah. So if you say this is isolated at C6 and you are savvy with the dermatome chart you say okay patient can you feel along here where's your sensory disturbance coming from where's the complaint at right along this distribution man all the way out remember spockan so C6 would be along the thumb so this helps you localize this lesion from from an MSK standpoint. So practice this practice this got little bit of time got to run got my next meeting and we'll do lab on Tuesday. Elena will be helping us with lab and we'll set up review session as well. That way you're you're building up with confidence. All right. Thanks for your time.