Ultrasound of Tendon Tears - HD

Introduction

Thank you, Bill.

I decided to tone down the lecture a little bit from tendon ruptures to tendon tears.

So next few minutes, we're gonna be talking about tendon tears.

Anatomic Considerations

I wanted to start out with a few anatomic considerations since it's good to know the anatomy and how to scan tendons and look at what normal and abnormal look like.

Okay. It's important to recognize that tendons are really a very densely packed hierarchy of collagen sorting from basic elements of collagen fibers surrounded by ground substance.

And then you see this hierarchy of tendon fibers and fascicles at the various levels, ultimately to be condensed into a very highly densely packed colinear structure, surrounded ultimately by a synovial lined sheath or a fiber adipose connective tissue.

This confers very high tensile strength to these structures.

The second important thing to recognize is that most of the tendon tears that we're gonna see really occur near the sites where tendons insert on bone and tendons insert on bone through a fibrocartilaginous avascular zone going onto the bone surface.

And typically we see these tendons insert onto bone next to a very convex surface usually consisting of bone or articular cartilage or soft tissue.

And this has the property of redistributing the stress load on the tendon actually producing a property known as stress shielding, whereby the tensile load on the tendon is actually reduced by compressive forces along these convex surfaces.

So that can be predictive to some extent, but it also can produce tendon damage as we'll talk about it in a few minutes by continuous repetitive loads.

Tendon Strength and Tears

So we spoke about tendons being very strong structures, and as a result of that, it's extremely uncommon to have a rupture of a tendon in any otherwise normal tendon.

We do see it occasionally in traumatic incidences, but it's very rare.

We generally see tendon tears in the setting of tendinopathy as opposed to tendonitis, which is more of a misnomer.

But this is the major cause of tears.

It's really a degenerative phenomenon rather than an inflammatory one.

And these are generally seen in the setting of overuse injury due to repetitive tensile and compressive loads on the tendons as well as the eccentric load distributions.

Pathophysiology of Tendinosis

So what happens when a tendon becomes tendinotic?

Well, you go from this type of scenario, which is a highly organized distribution of collagen and tenocytes to something more like this, where there's degeneration and dropout, disorganization of the collagen.

There's increased ground substance.

There's increased calcification, tendon cell death, tenocyte death due to apoptosis as well as chondrometaplasia with little or no inflammatory cells ever seen in the setting.

Predisposing Factors

There are a number of predisposing factors associated with tendon degeneration.

As we get older, unfortunately, we lose collagen.

We have collagen depletion, we have cellular apoptosis, and we have diminished blood flow.

So it's harder to get older, as we all know.

In addition, genetically there is a upregulation of matrix metalloproteinases, which are a form of collagenase that breaks down the collagen in our tendons.

And unfortunately, many tendons also have inherent critical zone or hypovascular zone within them that adds to that complexity.

When we are losing blood flow, those critical zones in fact increase in size.

And of course, for those among us who are smokers or patients who are obese, those are predisposing factors as well and concomitant drug uses.

I've had a number of patients who are on fluoroquinolones who have ultimately gone and developed tendinosis and tendon rupture.

So these are all things that we need to be aware of.

Scanning Tendons

Well, how do we scan tendons?

Well, generally speaking, these are linear, superficial structures.

We're gonna approach 'em similar to other superficial structures.

We're gonna use a high frequency transducer, and of course that frequency will depend on both anatomic location as well as depth and body habitus.

Proper positioning of an extremity can be very useful in order to improve acoustic access.

So this would be, for instance, a relaxed position in the shoulder if we're looking for the supraspinatus tendon.

But this is true regardless of where we're looking.

And of course, provocative maneuvers are always very helpful to help accentuate the tendon pathology and something we can use to our advantage.

And we'll talk about that in more in a few minutes.

Normal Tendon Appearance

So what does a normal tendon look like?

Well, regardless of where you are in the musculoskeletal system, tendons because of that arrangement of extracellular collagen will have this sort of hyperechoic fibrillar look.

So this appearance, so this is the flexor pollicis longus tendon in the thumb.

This is the Achilles tendon in the back of the heel.

So they're hyperechoic, they're fibrillar, they display a property known as anisotropy that we'll talk about in a few moments.

And of course, they may be surrounded by either synovial lined sheath or fibroadipose connective tissue.

Anisotropy

So what do I mean by anisotropy?

Well, if you look at this little inset over here, if the beam is perpendicular to the long axis of the tendon, we get maximum back scatter off the tendon.

So the tendon will appear bright.

Alternatively, if we're coming in on an angle relative to the tendon long axis, and that could be as little as five degrees, the tendon becomes progressively hypoechoic.

This becomes particularly important when we're looking tendons going around curved structures or curvilinear surfaces, such as the rotator cuff is one good example of that.

So when the beam is perpendicular here, you notice essential portion of the tendon appears more echogenic.

And in order to see the more distal portion of the tendon, I need to rock my transducer in order to intonate more perpendicular to the fiber orientation.

Now why is this important?

Well, tendinosis typically appears as either hypoechoic or heterogeneous on ultrasound, we lose that fibrillar architecture, so we don't want to artifactually do that by scanning incorrectly.

Tendinosis Appearance

The tendon may appear at large, there may be indistinct margin, cystic degeneration, abnormal calcification or ossification.

And we may see infiltration of abnormal vascularity in the form of angiofibroblastic proliferation, which is really just a fancy way of saying granulation tissue invests the tendon.

So this is a typical example of what this would look like.

This is an Achilles tendon, which is diffusely enlarged and homogeneous with areas where there's complete loss of that normal fibrillary architecture that we spoke about before.

This is independent of where we are looking in the musculoskeletal system.

So this would be in the rotator cuff, and this would be the example in the common flexor tendon of the elbow where you actually see a little bit of dystrophic calcification.

Now those calcifications could be punctate or it could be more extensive.

So this is an example of another patient with a bad Achilles tendinosis.

But look at all the diffuse calcification that we see in both long and short axis here.

It's really quite extensive.

Vascularity is another feature that we need to be aware of, and that is usually indicative of that granulation tissue we spoke about.

And it could be quite extensive sometimes.

And the important thing to realize is in a normal tendon, there's very little or no vascularity that we see on color flow imaging.

So anything of this order is clearly very abnormal.

So it's something we should keep track of.

Tendon Tears

Now, having spoken about tendinosis, let's start talking about tears.

Well, if ideally the primary sign of a tear would be in this diffusely abnormal tendon, you see a discretely marginated hypoechoic abnormality.

Well, unfortunately, life is not always that easy and in those situations we have to rely on a number of secondary signs, which can help us identify a tear in certain situations.

And of course, when you do see a tear, the important thing is to be aware of, and the things you should report about are where the tear is located, the extent of the tear and to give its dimensions.

So here we have a tendon, Achilles tendon, in which we see a discretely marginated hypoechoic defect entirely within the substance of the tendon.

So this is an example of an intrasubstance tear that we see here.

This is a high grade partial thickness tear along the deep surface of the Achilles tendon here in a diffusely tendinotic tendon in the so-called critical zone where there's diminished vascularity.

So this is a typical place where we would look for partial thickness tearing in an Achilles tendon, for instance.

Now, when you have a complete tear, you expect to have retraction of the torn ends.

And what we see really depends on whether or not the tendon is situated with an intact peritenon or tendon sheath.

So in this case, we have a complete tear, we have retraction of the two ends, but the peritenon is intact and we can still see this hypoechoic column of soft tissue or fluid corresponding to organizing hematoma or seroma within the intact peritenon.

Alternatively, when we have disruption of that containing structure, you expect to see herniation of the adjacent soft tissue into the defect.

So here's another complete rupture of an Achilles tendon, actually from a fight that we can see retracted approximately, and we see fluid over here, but we see herniation of the fat, the retrocalcaneal fat into that defect where the tendon used to be.

Now, we may not always be able to identify where the torn tendon is.

And one of the things that we can use to our advantage is this refraction artifact.

Typically because the acoustic properties of the tendon are significantly different adjacent to the soft tissue, whether it be seroma or muscle, you notice that as in this case of this hamstring tendon rupture, you have this dense refractile shadow on one side, and I can really tell you exactly where the tendon is situated.

So we can use this sometimes as a very helpful feature when we're scanning and we're not sure if we're seeing the tendon end.

Well again, dynamic scanning.

And what I mean by that is performance of provocative maneuvers can be very helpful.

So if you look at this Achilles tendon's diffusely abnormal, but you'd be hard pressed to say exactly where the tear is or how extensive it is.

But when we use simple plantar flexion of this tendon, you can actually see this is distal, this is proximal, and you can see this gap opening up and the proximal portion is not moving at all.

So you can actually see that this is actually a complete rupture of the tendon, where the torn ends are rarely in close apposition to one another.

And the dynamic maneuver can be very helpful in terms of identifying that.

Tears at Sites of Weakness

Now, tendon tears also occur at the site of weakness.

So we remember tendons are very strong structures.

So if you're dealing with a child, and this was an example of a high level gymnast who had acute onset of pain in the retrocalcaneal area during a floor exercise, it may not be the tendon itself that ruptures, but in a child in particular, the weak point is in fact the growth plate.

And in this case, you could see the tendon pretty much is intact attached to bone, but the apophysis is actually ruptured off.

And there's really a fracture through the growth plate over here.

And that's really the site of where the rupture occurred.

Secondary Signs for Tears

Now, tendon tears may also be filled with complex soft tissue, granulation tissue, scar tissue, and it can be sometimes difficult to see them.

Well, in some cases we have secondary signs that help us, particularly in the rotator cuff.

This so-called cartilage interface can be very helpful, where you have complex of fluid granulation tissue filling the defect, almost making it look like an intact tendon.

But you notice the conspicuity of the articular cartilage is significantly increased in this situation due to the difference in acoustic attenuation between the normal tendon and the complex fluid.

So it increases the reflectivity and that can be very helpful, particularly if you're looking in the shoulder.

Distribution of Tendon Tears

The distribution of the tear distribution, where to look at the tendon to some extent depends on the activity, where the forces are located as well as anatomic factors, whether there be hypovascular zones or whether the anatomy of the tendon itself, whether it be a simple single tendon or multiple tendons that are conjoined.

So this would be an example of a jumper's knee, which tends where the force concentration tends to be along the inferior pole of the patella along the deep medial surface.

So here we have that, we see that in this MR as well as in the ultrasound and tennis players.

It tends to be a chronic supination and hyperextension injury, which tends to cause compressive forces along the lateral epicondyle.

So we see the sort of typical distribution of tendon tears along the deep fibers of one tendon.

In particular, the extensor carpi radialis brevis tears that occur along that extend along bony eminences usually due to pressure along those bony eminences.

An example of that would be typical of patients who have in the foot and ankle.

So this patient has pain along the medial aspect of the ankle.

You see this is the posterior tibial tendon with the T2 bright linear area within the tendon.

The corresponding ultrasound we see over here is this hypoechoic defect.

And this is typical of what we see in these types of tendons, typically appearing as linear split tears.

Same thing we see in the lateral aspect of the ankle, usually due to pressure from the peroneus longus as it sits on the peroneus brevis along the lateral malleolus, you have this typical appearance where the pressure effects of the peroneus longus along the peroneus brevis tendon against this hard bony surface cause a central split.

And you'll see displacement of the two ends of the peroneus brevis with usually central herniation of the peroneus longus.

Shoulder and Rotator Cuff Anatomy

Now finally, we talk about shoulder as an example of complex anatomy.

And this is probably one of the more complex, one of the most common ultrasounds we were asked to do.

And I'm sure it's true at Wash U where Bill is, and we know it's a common source of pain affecting as much as 40% of the population.

But the anatomy is really quite complex.

It's really multi-layered.

So let's take a look at that briefly.

Well, there are actually five layers that constitute the rotator cuff.

There's a superficial layer is a superficial extension of the coracohumeral ligament.

Then we have the supraspinatus infraspinatus tendons adjacent to one another.

Then we have a deeper layer corresponding to the so-called rotator cuff rotator cable, which is really the inferior extension of the coracohumeral ligament.

And then we have the joint capsule.

So it's not as simple as we would think.

And then in addition that both the supraspinatus and infraspinatus tendons are bilaminar structure.

So there's actually a bursal and articular lamina associated with that.

So we see this reflected in the types of tears we see.

So in partial thickness tears, we can have either the articular bursal lamina affected, or we can have actually a delaminating tear occurring between those two structures.

And when we see full thickness tears, that can either involve portions of a tendon complete involvement of a tendon or as well as being massive.

Examples of Rotator Cuff Tears

So let's take a look. A few examples to finish off.

So this would be an example of a high grade partial thickness tear involving the articular lamina of this patient.

An entirely delaminating tear between both the superficial and deep lamina in this particular patient where you can see the high signal area going through the tendon here, as well as the corresponding low hypoechoic area within this between the bursal and articular lamina and the supraspinatus tendon.

And of course, this is an example of a full thickness tear involving the supraspinatus tendon over the anterior facet, superior facet involving the full tendon and going full thickness all the way to the bursal surface.

Take Home Points

So if you take home points, what to look for, remember tendinosis appears as a hypoechoic or heterogeneous abnormality, you lose the fibrillar architecture.

You may see calcification or that angiofibroblastic response.

When we're looking for tears, it usually ideally appears as a discreet hypoechoic defect within tendon.

But there are secondary signs that we can use to take advantage of to help us identify the tendon.

If it's not quite clear exactly where the tendon is located, perform ultrasound is dynamic.

You should always perform provocative maneuvers in order to enhance the appearance of the tendon.

And remember, tendon tears often occur in fairly predictable patterns.

Thank you very much.