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So welcome back to our discussion.

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This is shoulder week, also known as shark shoulder week.

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Kind of like shark week.

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We're drilling into the shoulder

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and we're going to drill further.

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Earlier on we were talking about the locations

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medially, laterally of rotator cuff injuries.

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We began with footplate or footprint

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injuries that may or may not penetrate bone.

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So-called rim rent configuration

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tears that are concealed or hidden.

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Either word is fine.

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And when they're somewhat linear and small, we

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refer to them as CIDs, concealed interstitial

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delaminations, with or without rim ring component.

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Then, if you have involvement of the rotator cuff,

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right over top of this yellow area, say right

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here, you'd say there's a small undersurface tear

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along the bare area of the intra-articular space.

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A partial thickness tear, as long as it doesn't communicate.

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But we're not into a discussion of depth just yet.

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Then if you have a tear over here, it would be in

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the articular surface, uh, or the articular surface

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region of the humeral head, either the lateral

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articular surface, the apex, or the medial portion.

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But you're also going to describe the tear not only

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by its relationship to the humeral head, whose anatomy

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now you know in excruciating detail, but also by its

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relationship to the muscle, the myotendinous junction,

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the cable, the crescent, and the footplate or footprint.

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So that takes us to our next

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discussion of the supraspinatus.

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And secondarily, we can extrapolate it to the infraspinatus.

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That takes us to the sagittal projection.

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So, believe it or not, we're still on

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the basic discussion of rotator cuffs.

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We haven't gotten to all the crazy names and

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all the other crazy stuff we're going to cover.

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And I made my sagittal humeral head really big.

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It's because I'm not a great drawer.

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And we'll call this A, anterior.

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And this P, posterior.

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My P isn't very good.

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I better make my line a little bit thinner.

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And now let's get our, let's get our

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rotator cuff going here in purple.

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Here's the supraspinatus portion of the cuff.

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And then the supraspinatus portion of the cuff is

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connected to the infraspinatus portion of the cuff.

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Right at about, just past the apex of the humeral head.

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Is about usually where they transition.

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We'll make our infraspinatus, well, green.

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Here's our infraspinatus.

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And this area here, which is connected

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by a small fibroelastic membrane.

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Which can be very short.

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Can be congenitally longer.

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Or it can be acquired.

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Stretch out.

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So it can become longer from front to back over time.

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When you tear either one of these, you're going to look at

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depth, which we're going to discuss in a few minutes, but

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right now I want to concentrate on the concept of length.

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When you're looking at depth and length, this concept

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really resonates more when you're dealing with flat tendons.

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So, depth is obvious.

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It's going to be this.

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Length is A to P in the shoulder.

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So if you tore this entire structure from front to back,

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and you had nothing here, you would say, there's a complete,

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and if it goes all the way through, full thickness, and

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then you use the coronal to describe the retraction.

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If it's just the anterior half, then you'd

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say, anterior. And you'd give them the length.

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So the length might be something like this,

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if the tear is this long, from here to here.

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If you're missing the whole supraspinatus,

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you'd say it's complete, and it has X length.

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If it goes into the infraspinatus, you'd say it's got

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the anterior fibers of the infraspinatus, all the fibers

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of the supraspinatus, and now it's 4 centimeters A to P.

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We'll talk about depth in a moment.

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We're talking simply about completeness.

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And then if it goes all the way around back, it's got

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the entire infraspinatus, the entire supraspinatus, it's

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a complete infraspinatus, it's a complete supraspinatus.

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We'll say it's a full-thickness tear, the entire thickness

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of both tendons, and the length is five centimeters.

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And the humeral head is now bald.

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And we use that term, bald humeral head.

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This little spot right here, this fibroelastic membrane

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in light blue. Maybe we need another color, like red.

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In red, we say it can be a little bit longer.

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It can stretch out.

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You can be born with a longer one.

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But this area is prone to microtrauma, microseparation,

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and because it's very thin and membranous, diffusion.

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So if you're going to get some diffusion of

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synovial fluid and fluid into the rotator cuff

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muscles, it's often going to come from right here.

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And it'll come out of here as a little tiny thing

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that you can hardly even see or you cannot see.

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Because it's a diffusion event.

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And then it'll go into the muscle and it'll

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balloon as it tracks from medial to lateral.

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And that's known as a cystic tear.

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And as they balloon, if they trumpet from medial

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to lateral, let's say it comes out and it gets

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in the muscle and it does something like this.

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It's called a sentinel cystic tear.

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In other words, it has a little blowhole at the very end.

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The little hole where it comes

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out of is very difficult to see.

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Sometimes you see it, sometimes you don't.

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Very rarely will something like this be a true

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ganglion that arises from the tendon in the

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muscle but has no communication with the joint.

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90 percent of the time, it came from the joint.

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From a small rotator cuff or rotator interval injury.

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And we said there are other intervals.

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There's an anterior interval, right here.

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That's the space between the supra and

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the subscapularis, which we will make

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now, in blue. We'll make it a lot thicker.

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Here's our subscapularis.

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And the subscapularis, unlike these other tendons, that

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fan out and flatten out and blend together and make

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a mesh, of low signal intensity, almost like a net.

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The subscapularis doesn't do that.

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The subscapularis usually has four or five

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dominant tendons inside it, which you can

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see, that divides it up into various segments.

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So, you don't have to say which segment it is.

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You just should probably say upper third, upper fourth,

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you know, middle third, you know, second fourth, whatever.

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Just be descriptive.

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The clinician really only cares about generalities here.

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The upper half of it is ruptured.

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The lower half of it is ruptured.

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It's a partial-thickness tear.

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It's an interstitial tear.

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It's a concealed tear.

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We're going to get to that as a separate subject when we get

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into subscapularis tears, but that's an introduction to it.

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And one of the best sequences to diagnose

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subscap tears is the sagittal projection.

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Because you're absolutely perpendicular to

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this structure and it's a rather complex

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structure as we'll see in a few moments.

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We also have another interval.

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That other interval is the deep posture interval

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between the infraspinatus and the teres minor.

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We'll make the teres minor some pretty color like orange.

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Now the good news here is it's a

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little like politics and US Congress.

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Nothing ever really happens here.

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So you don't have to be, you don't

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have to be too concerned about it.

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Nothing ever really happens in the terries,

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and not much happens here except one thing.

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you're doing an arthrogram or an MR arthrogram.

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It's very safe.

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It's easy to get into.

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There's no important structures here that

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are of biblical or political significance.

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So you can get in here without a lot of worry, and if you

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miss, the consequences are usually nonexistent or nominal.

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This is also a great projection to assess

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where your pits or pseudocysts are.

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And, you know, they look somewhat like this.

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Either irregularity or you actually

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see subchondral or subcortical cysts.

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And they tell you kind of what's going on

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physiologically and pathoanatomically with the shoulders.

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So if a lot of these changes are in the

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front, let's pick another color like pink.

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If a lot of these cystic changes are in the front,

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you know that there's going to be contact of the

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humeral head with the subacromial arch and the acromion

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when the patient's arm is forward and over the head.

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Kind of anterior.

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This is called external impingement.

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Whereas if most of the pits and irregularities and

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pseudocysts are in the back, near the infraspinatus,

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remember this is posterior, here's our P, then Most of

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the contact is going to occur in the cocking position.

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This is called internal impingement.

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And there's another one.

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If a lot of these pits and irregularities are deep to

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the subscap, then there's a pretty good chance you're

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dealing with subcoracoid far anterior arch impingement.

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Which is the least common of the three.

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And there's another one called anterior superior

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impingement, which is a story for another day.

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So I'm going to stop right now

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regarding the sagittal projection.

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You know, that is my story for the sagittal projection.

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It's the introductory story, but yet, it's pretty complex.

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Because the shoulder is a ball and socket joint.

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And ball and socket joints are the toughest ones to assess.

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Let's take a breather.

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You take a breath.

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And then we'll come back and we'll

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continue on with our diagrams.