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Clavicle

Structure of the clavicle seen from anterior, inferior and superior views.

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Transcript

Hey everyone! It's Nicole from Kenhub, and welcome to our tutorial on the clavicle.

In this video, we’re going to be looking at the clavicle and its bony features. To get a good grasp on the clavicle, we’re going to be looking at a few different parts of the clavicle, starting off with the articulations and their associated articular surfaces. We’re also going to be looking at the bony features of the clavicle and the clavicle’s orientation including the superior versus inferior aspect, the lateral versus the medial aspect, and the anterior versus the posterior aspect of the clavicle. And, lastly, we’ll have a look at a relevant clinical correlation.

Let’s begin first by having a talk about what the clavicle is.

So, what is the clavicle and where can we find it? The clavicle, or the collarbone, as it’s often called, is an elongated S-shaped bone that lies horizontally across the upper rib cage. And here in this image, we can see the clavicle highlighted in green. As we can see, the clavicle articulates medially with the sternum and laterally with the acromion process of the scapula to form the pectoral girdle which is also called the shoulder girdle.

So, the clavicle plays an essential role in everyday functional movement serving as the connection between the axial skeleton and the upper limb, and it’s the only bony connection between these two parts of the body. Because of this, the clavicle acts as a brace for the shoulder allowing weight to be transferred from the upper limb to the axial skeleton. It also helps to protect neurovascular structures as they travel between the trunk and the upper limb.

Now, let’s take a minute to look at the joints that the clavicle helps to form.

So, the names might seem a little bit scary at first but it helps to remember that these joints are named simply because of the structures that form them. So, the clavicle articulates with different structures on either of its ends, forming two joints, and these are the sternoclavicular joint and the acromioclavicular joint. We’ll also briefly look at the articular surfaces which includes the sternal articular surface and the acromial articular surface. Let’s begin by looking at the joints.

Medially, we’ll find the sternoclavicular joint, which is what we can see in this image. So, this synovial joint is formed by the sternal end of the clavicle and the manubrium of the sternum, and it’s through this joint that the clavicle connects the upper limb to the axial skeleton. The sternoclavicular joint is a strong joint but also allows for significant mobility of the upper limb.

The lateral joint of the clavicle which we can see here is the acromioclavicular joint, and we can see it highlighted in this image of the anterior right shoulder. The acromioclavicular joint is a plane type synovial joint and it’s formed by the articulation of the acromial end of the clavicle with the acromion process of the scapula and this joint functions to keep movements of the scapula separated from the trunk when the arm is moved in various ways.

Both the sternoclavicular and the acromioclavicular joints are surrounded by a number of ligaments that acts to strengthen and stabilize the joints – and you can actually see some of the ligaments on this image.

So, let’s take a closer look at the articular surfaces of the clavicle that help form these joints.

In this image, we’re looking at two right clavicles. The one at the top of the screen is an inferior view and the one below it is a superior view. The area we see highlighted on these clavicles is the acromial articular surface, and this surface as you can see is small and oval in shape and is at the most lateral aspect of the clavicle. And this allows it to articulate or connect with the acromion process of the scapula.

In this same image of the right clavicle, the sternal articular surface is the highlighted feature, and the surface is quadrangular in shape and is at the most medial aspect of the clavicle where it articulates with the manubrium of the sternum.

Between the two articular ends of the clavicle is simply the body of the clavicle, which we can now see highlighted in green.

So now that we’ve looked a little closer at these structures, let’s move on to the rest of the bony features.

There are four bony features between the two articular surfaces of the clavicle and we’re going to be looking at each of them moving from the medial or sternal end to the lateral or acromial end, and these features are the impression for the costoclavicular ligament, the subclavian groove, the conoid tubercle, and the trapezoid line. And we’re going to start off by talking about the impression for the costoclavicular ligament.

So, the most medial bony feature which we can see in this image is, as we mentioned, the impression for the costoclavicular ligament, and this impression as the name suggests allows for the attachment of the costoclavicular ligament which connects the clavicle to the first rib. As you may have noticed on the image, we can only see this feature on one surface of the clavicle and this is the inferior surface. And we know that this impression has to be on the inferior surface because the ligament is running to the first rib which is inferior to the clavicle.

The feature we can see highlighted right now is the subclavian groove, and similar to the impression for the costoclavicular ligament, it can only be seen on one surface which is the inferior surface. In this image on the right, we’re now looking only at the inferior aspect of the clavicle with the subclavian groove still highlighted. And the subclavian groove, as you can probably guess from the name, is the attachment site for the subclavius muscle, which is as the name suggests, is underneath or inferior to the clavicle. And, in this image, you can see the right subclavius muscle.

Moving more towards the lateral or the acromial end, we’ll come across this highlighted feature which is known as the conoid tubercle. And the conoid tubercle is a rough eminence where the flat body of the clavicle meets the bulkier acromial end of the clavicle. It serves as an attachment point for the conoid ligament which is involved in the coracoclavicular ligament – ligament between the coracoid process of the scapula and the clavicle. And in this image, we’re looking at the anterior aspect of the right shoulder girdle, and over here we have the clavicle, over here we have the scapula, and over here we have the humerus. The conoid ligament of the coracoclavicular ligament runs from the inferior surface of the clavicle, the conoid tubercle to the superior aspect of the coracoid process of the scapula which is right here.

The final bony feature that we’re going to be talking about today is the feature that we can see highlighted in green, and this is the trapezoid line. So, similar to the conoid tubercle, it’s an attachment site for a ligament and the ligament that attaches here is called the trapezoid ligament. So, we can see the trapezoid ligament highlighted on this image right now and we can tell that this ligament is the lateral part of the coracoclavicular ligament. And like its conoid counterpart, it also runs from the inferior aspect of the clavicle to the coracoid process of the scapula.

And that’s it for the bony features of the clavicle. As we mentioned before, let’s take a little bit of a look at orientation of the clavicle.

So, often when looking at a clavicle on its own, it can really be difficult to orientate yourself and work out if it’s the left or right clavicle because they do just look like a piece of bone. But in this tutorial, we’re going to work through some ways to help figure out what you’re looking at starting by looking at a general image of a clavicle. So, in this image that you can see on your screen, the first question we want to ask is, how do we know if we’re looking at a right or left clavicle, or perhaps we’re looking at one of each?

As with orientation for all bones, we need to determine three things. So, number one, if we’re looking at the superior or inferior aspect of the bone; number two, which side is the lateral aspect and which side is the medial aspect; and number three, which side is posterior and which side is anterior.

So, to identify whether we’re looking at a clavicle from the superior or inferior aspect, we can use the presence of bony features which we talked about throughout this tutorial as a clue. And all four bony features that we talked about today are present on the inferior aspect of the clavicle, so that’s going to help us a lot with identifying our superior and inferior aspects.

So, most medially on the inferior surface, we have the impression for the costoclavicular ligament, and here again, we have the subclavian groove which is, if you remember, an attachment for the subclavius muscles. Over here we have the conoid tubercle, and remember that this is an attachment point for the conoid ligament of the coracoclavicular ligament. And, finally, over here, we have the trapezoid line, where the other part of the coracoclavicular ligament attaches known as the trapezoid ligament. And all four of these features are attachment sites for structures that run inferior to the clavicle. So, anytime you can see the highlighted structures clearly, you know that you’re looking at the inferior view of the clavicle.

Alright, moving on, we wanted to next then identify whether we’re looking at the lateral end or the medial end. So, in order to do that for the clavicle, we want to be looking at its articular surfaces. So, the acromial articular surface – the small oval-shaped facet over here, is our lateral end. The sternal articular surface which is the quadrangular-shaped facet is our medial end. And if we’re looking at the inferior aspect and can identify the bony features of the clavicle, these two can help determine which end is lateral and which side is medial.

As we mentioned earlier, the impression of the costoclavicular ligament is on the medial end since that ligament runs to the first rib and the trapezoid line and the conoid tubercle being involved with the ligaments running to the scapula are at the lateral end of the clavicle.

Now, let’s look at how to identify the anterior and the posterior parts of the clavicle. The main feature that we can use to determine which aspect is posterior is where the conoid tubercle is. And it’s quite a prominent projection and it’s always pointing posteriorly.

So now that we know all of that, let’s see if we can now identify whether we’re looking at a right or left clavicle.

So, we can see the bony features we identified today. So, the impression for the costoclavicular ligament, the subclavian groove, the conoid tubercle, and the trapezoid line. So, therefore, we’re looking at the inferior aspect of the clavicle. Alright, so, here is the sternal articular facet and the impression for the costoclavicular ligament, so this must be the medial end.

Using what we’ve learned before, let’s now have a look at what are the anterior and posterior parts and so, in this image, we can see that the conoid tubercle is over here. So, this way is posterior. With all of these clues, we can imagine that we’re looking at this clavicle from the feet of a person who’s lying on their back and therefore in the supine position, therefore, we must be looking at a right clavicle.

Alright, so thanks for sticking with me throughout this tutorial. Before I let you go though, let’s have a look at a clinical correlate of the clavicle. And the clavicle is the most frequently fractured bone of the body. Some causes of clavicular fractures are one, a direct fall onto the shoulder so forces applied medially and results in a fracture, and two, if someone falls on an outstretched hand, the transmission of force from the upper limb to the shoulder can result in a fracture of the clavicle.

Due to the attachment of the sternocleidomastoid muscle on the medial portion of the clavicle, the medial fragment of a fractured clavicle will be elevated in a patient. So, the lateral fragment would end up being depressed because the weight of the upper limb is no longer able to be transmitted to the trunk. And, usually, with the use of a shoulder sling, clavicular fractures can heal on their own.

So, now, you’re an expert on the clavicle.

Before I let you go, let’s have a quick run through of what we looked at today. So, we began by looking at where the clavicle is in the body and we also looked at its role in attaching the upper limb to the axial skeleton, transferring weight and protecting neurovascular structures that run between them. We then looked at articulations the clavicle makes at the sternoclavicular joint and the acromioclavicular joint. And, next, we had a look at the bony features of the clavicle which included the two articular facts, the body, and the attachment sites of various ligaments and muscles. We then looked at how to use these bony features as clues to determine if we’re looking at a right or left clavicle. And, finally, we looked at fractures of the clavicle, how they can be caused, and what a patient with a fractured clavicle might look like.

That brings us to the end of our tutorial on the clavicle. I hope you enjoyed it. Thanks for joining me!

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