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| hold the humerus in place so the larger muscles (pectoralis major, deltoid, and latissimus dorsi) can do their work |
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| Elbow Joint (Three Joints) |
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Humeroulnar: hinge
Humeroradial: ball and socket
Radioulnar: pivot |
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| Wrist and Hand impt anatomuy |
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Wrist joint mostly with radius, scaphoid, and lunate
Carpal bones form an arch (carpal tunnel) |
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| transfers most of the force across the wrist to the radius |
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| Scaphoid (Eight carpal bones form an arch) |
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| Radial and ulnar arteries form |
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| medial cubital vein for venipuncture and brachial artery for blood pressure |
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| lateral rotation of the shoulder |
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| Infraspinatus/teres minor |
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| medially rotates the shoulder |
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Abductor pollicis brevis
Flexor pollicis brevis
Opponens pollicis (deep) |
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| With respect to the hip, the shoulder joint has |
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| A more shallow socket, a looser joint capsule, and greater range of movement |
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| Which movements are allowed at the humeroulnar joint? |
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| Weight is transferred from the hand to forearm by the |
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| The brachial artery divides into radial and ulnar branches where |
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| T/F In the event of occlusion of the radial artery at the wrist, blood flow to the hand can be maintained from the ulnar artery through the palmar arterial arches. |
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| At the cubital fossa the brachial artery is |
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| Medial to the biceps tendon |
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| The thenar muscles, supplied by the recurrent branch of the radial nerve, are critically important in positioning the thumb for grasping. Which muscles are in this group? |
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Opponens pollicis
Flexor pollicis brevis
Abductor pollicis brevis |
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| The brachial plexus is formed by the ventral rami of spinal nerves from |
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What does weakness in both elbow and wrist extensors suggest?
What does the brachioradialis muscle do? |
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So that indicates some sort of radial nerve issue because the radial nerve supplies the entire posterior compartment of the arm and the forearm. So that's the triceps. And then all those extensor muscles in the forearm, so that indicates that it's some sort of radial issue, radial nerve issue. wrist drop. So again, the person is unable to extend their wrist because there is a mismatch between the weakened extensors and the stronger flexors.
So in that position you're isolating almost completely the brachioradialis muscle which flexes the forearm of when you're in that mid-prone supinated position. And that's also innervated by the radial nerve. |
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The shoulder is medially rotated because the lateral rotators are weak. What supplies them?
There are deficits in more than one compartment. What does that suggest?
Why is the forearm pronated? Hint: What are the two supinators? |
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range of the brachial plexus actually? It goes from that C5 to C-- T1.
when we think of abduction of the shoulder what muscles do we think about? So we think about the deltoid, which is supplied by the axillary nerve. And then we also think that the supraspinatus muscle, which would be supplied by the suprascapular nerve?
Suprascapular. Excellent. And do you remember what route levels those are supplied by? Those muscles? I think those two again, C5--C5 and C6
We also see weakness in inflection of the elbow. What muscle does that, Tim? That would be mostly the biceps. OK. And the-- and its nerve supply? Musculocutaneous. (C5-C6)
And the change in posture, is it the shoulder is medially rotated. So that implies that the medial rotators are stronger than the lateral rotators. What's the main lateral rotator of the shoulder? The infraspinatus muscle? And it's supplied by the Suprascapular nerve.
forearm is pronated. So the forearm is in this position, and that's a change in posture as well. That means that there's a imbalance between the supinators and the pronators.
So what do you think is going on there? Which-- how is that-- how does that come to be? Tim? So it would probably be, again, with the biceps because it actually also supinates. Yeah, the biceps is a powerful supinator. |
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| carpal tunnel thenar atrophy due to |
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| So examining and comparing right hand and left hand, you see that the thenar eminence is smaller. And she has weakness on thumb-- so we said that one of the thenar muscles, the abductor pollicis brevis abducted the thumb. So if you have her hold her thumb and say, abduct, abduct, compare right to left that she's not very good at abducting with her left hand. And she has difficulty making an a-OK, which is a classic sign of what the muscles of the thenar eminence do. why is there thenar atrophy? Well, if a muscle is deprived of its input, it will eventually lose mass. So if part of the nerve isn't reaching the muscle, these bits of muscle will lose their innervation, and they'll atrophy. So that's a reason for the atrophy. |
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| muscle actions of the thenar eminence |
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| to make the a-OK sign we had to abduct our thumb. We had to flex it. And we had to oppose it. |
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| carpal tunnel why can hold piece of paper between fingers |
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| means that the ulnar nerve, which supplies the muscles that abduct and adduct the fingers are intact. So that narrows the problem down to the median nerve, and eliminates, for the most part, the consideration that it might be the ulnar nerve as well. |
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[image]
-humeral ulnar joint=hinge joint, flexion and extension
-radiohumeral joint can also pivot, supinate and pronate and flex and extend, almost a ball in socket joint
-joint at radius and ulna is a pivot joint |
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[image]
-carpal bones form an arch, transverse carpal ligament crosses it, carpal tunnel goes through the arch
So the carpal bones are important in transferring the weight of the fingers to the wrist, but are also important in organizing the passage of tendons and the median nerve as they pass to the hand.
So to summarize then, the eight carpal bones form an arch. And the scaphoid transfers most of the weight of the hand to the radius. And as such, it places it at risk for injury.
Now, we can see a pin that has been placed in the scaphoid because of what's called ischemic non-union. Besides transferring most of the force because of its fragile vasculature, the scaphoid is prone to nonunion, or failure to fuse after a fracture, and may need to be pinned. |
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[image]
So the blood supply of the shoulder and arm comes from the subclavian artery, which we can-- which we can see here, from the right subclavian from the brachiocephalic trunk and the left subclavian directly from the arch of the aorta. And then the artery retains its name until it passes inferior to the clavicle. It enters the axilla and becomes the axillary artery. And then as it travels, it continues, it travels into the arm. As it passes inferior to the tendon of the teres major it becomes the brachial artery.
So we think about branches around the shoulder, we think of a number of branches, important ones the therocromial artery is one branch of the axillary artery because it supplies the pectoralis major, an important muscle. And a little more inferiorly here, we see the subscapular artery, which, as its name implies, supplies the scapula and related muscles on the posterior back.
And then there's another vessel, the posterior humeral circumflex artery, which passes around the neck of the humerus. Whenever we see the word circumflex, we know that it travels around something. And it supplies, among other things, the deltoid muscle, which is important to us.
And then continuing inferiorly, we see a profunda brachial, or in more simple terms, the deep brachial artery, just as we saw a deep femoral artery in the thigh. And it travels around and supplies posterior arm. |
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[image]
Then as we continue distally, just distal to the elbow, the brachial artery divides into radial, radial branch, and an ulnar branch. But just as we saw in the knee, we have collateral pathways that provide alternative routes around the joint. These are collateral vessels descending, which are joined from below by recurrent branches, which ascend. And these allow for blood flow to have several routes to reach the distal part of the extremity if need be. |
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[image]
Now at the wrist, obviously, we're interested-- these are pulse points-- we're interested in the radial artery at the wrist and the ulnar artery at the wrist. But what we see here in the hand is a very important, and in many ways, unique anastimosis. We recall an anastimosis, this is where two vessels meet and potentially supply the same territory.
The radial and ulnar arteries meet in the hand in two arches, the superficial and deep palmar arterial arch. What this means then is that blood flow-- if blood flow to the ulnar artery is obstructed here, blood flow to the fingers can be maintained through the arch through the radial branches.
Similarly, this passes-- it can work the other way. In fact, quite commonly, if someone is putting in a line for arterial blood gases, it's done through the-- it's done at the radial artery. And it's important to know in case that artery becomes damaged in the procedure that there is an intact arch coming from the ulnar. So what this means then is that the hand which is, because of its exposure to dangers, is preserved in a unique way that allows a blood flow to be maintained if one of the two main blood supplies is interrupted. |
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[image]
Another important region here because of the fact that you'll do procedures is the cubital fossa. And first, superficially, just in the lower limb as we saw a greater and lesser saphenous vein, we have two superficial veins that begin on the dorsum of the hand-- the cephalic vein, which travels up the radial border of the arm, and the basilic vein, which travels up the ulnar border. These are superficial veins unaccompanied by arteries. And they're connected one to the other at the elbow by the median cubital vein.
And this is a site for us because we can draw blood from this region here. And if we cause a problem here, blood still has a free route to travel up in that direction. So this is an anastimosis, which is common in veins, but we can take advantage of to draw blood. |
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[image]
Now if we go a little bit deeper now and take away the superficial fascia here, we see some more detailed anatomy. We see the biceps tendon here, and we see the brachial artery. So this is where you'll be measuring blood pressures and taking-- and sometimes taking pulses. And the advantage of this, as always, is that we use things that we can find easily-- the tendon of the biceps-- and if we go just medial to that, we'll be able to feel the brachial artery.
So this is, again, like the femoral triangle, a place where we do procedures and we feel for pulses and we need to pay a little bit of extra special attention to these structures as they pass the joint. |
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supraspinatus
If we go now to one of our rotator cuff muscles, we see a very important muscle, the supraspinatus muscle, which abducts the shoulder.
And as we see here, it passes right here under the spine of the scapula, the acromion in particular. And as it passes through there, it's at risk for injury, because it's a narrow passage.
So weakness in supraspinatus and damage of the tendon is a consequence of its course as it passes out to the humerus. |
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| We're looking now at a posterior view of the shoulder. It's the scapula here. We see two muscles arising from the posterior surface of the scapula. They go around to the posterior aspect of the humerus. And these are lateral rotators. The infraspinatus and the teres minor. |
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subscapularis
We now view the anterior surface of the scapula. We see the subscapularis muscle, which passes anterior to the shoulder joint to insert on the humerus. And when it contracts, it's a medial rotator.
But recall, when all of these rotator cuff muscles act together, they stabilize the shoulder joint. |
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deltoid muscle
strong muscles, the deltoid muscle, which abducts the shoulder. As you can see here, it has some anterior fibers. But it also flexes the shoulder. |
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pectoralis major
Pectoralis major here is large muscle, a large chest muscle, the muscle of the bench press. And the pectoralis major adducts the shoulder, meaning it brings the humerus closer to the midline.
And it has three heads. It has a clavicular head, a sternal head, and a costal head? |
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latissimus dorsi
And posteriorly, we see the latissimus dorsi muscle, which extends the shoulder. And it's that muscle that gives swimmers their V shaped back, like Michael Phelps or Missy Franklin, because of the large amount of time they've spent in the water pulling their arm through the water using their latissimus dorsi. |
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We come now to the biceps. The biceps flexes the elbow. And it also supinates the forearm. And that's probably an important secondary function. That's one you should probably know, cause it both flexes and supinates. It flexes the elbow and supinates the forearm.
And it's a muscle that interests us for a number of reasons. One of them is, we can see it. We can feel it. We can test its function by having the patient resisting the patient's efforts to flex. It has a tendon that we can hit. So it should be high on our list of muscles to know about. |
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So if we begin with the trapezius muscle, it's a posterior muscle that has a long extent along the spine and the head. It goes to the scapula.
And you can see it has downward fibers, and it has upward fibers. It has medial fibers. And we could fuss about which fibers did what. But from your point of view, you're going to test the muscle by asking the patient to shrug their shoulders.
So you're going to be concerned about these fibers. And unless you're a physical trainer, you shouldn't care very much about the other fibers. |
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| Similarly, the triceps extends the elbow. And it has a tendon that we can hit. And just as we're interested in the biceps for flexion of the elbow, we're interested in the triceps for extension, another muscle which you should pay some attention to. |
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flexor digitorum
In the forearm we have a bunch of muscles. Flexor muscles. Flexor digitorum that flexes the fingers. We have flexor carpi radialis, flexor carpi ulnaris that flex the wrists. |
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[image]
On the dorsum of the hand, we have extensor digitorum. We've got extensor carpi radialis longus and brevis, extensor carpi ulnaris.
In the hand, though, we become very interested in a set of muscles. These are the thenar muscles, the muscles of the thenar eminence. And they're extremely important because these muscles are absolutely vital in grip.
If we want to grip something, we need to, first of all, pull our thumb away so we can fit it in that space. We need to flex our thumb. And then we need to pull it over so we can firmly grasp something.
There are three muscles in the thenar eminence responsible for that, the abductor pollicis, which abducts the thumb, the flexor, which flexes it, and the opponens, which pulls it over.
These are the three muscles of the thenar eminence. These muscles are controlled by a branch of the median nerve, a branch called the recurrent branch of the median, which we see here. And it's a very important branch of the median nerve.
We see here the median nerve passes through the carpal tunnel. And compression of the nerve as it passes under the tunnel here is going to affect the strength of the thenar muscle group, and affect sensation on the index, middle, and part of the ring finger.
So these symptoms, tingling in the radial hand, and weakness in the thenar eminence are signs of what's called carpal tunnel syndrome, which I'm sure you'll study in considerable detail in your neurology courses. |
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[image]
We're interested principally in the ones that supply muscles, muscles that we care about. So the nerves that we care about are the super scapular nerve, which supplies the supraspinatus and infraspinatus, two very important members of the rotator cuff. We're interested in the axillary nerve, which supplies the deltoid and also the teres minor, and the muscular cutaneous nerve, which supplies the biceps.
And we should see that all of these nerves so far are supplied by C5 and C6 spinal nerves. And we should also note in comparison to muscles that we'll look at in the minute that these are all proximal muscles. So one of the generalizations we can draw here is that C5 and C6 tend to innervate muscles which are closer to the central axis as opposed to other nerves. |
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| shoulder replacement reverse prosthesis |
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