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The joints between the ribs and the vertebrae.
Ribs. Wait, no. I meant these ribs. What if I told you that these long, thin lightweight bones could possibly be considered one of the most important group of bones in the entire body? Yes, we all know that these bones form the thoracic cage providing protection for our heart and lungs. But did you know that without our ribcage, our lungs would not be able to take even a single breath of air? I’ll explain why this is another day, but for now, let’s just agree that these twenty-four bony rods are some of the most underestimated members of the human skeleton.
Although the curved form and ability to flex makes each of the rib bones resistant to fractures, like whole bones, a rib will break if it’s hit hard enough. In fact, fractures to these bones are commonly seen in trauma-related incidents such as motor accidents, sports-related injuries, assault, or simply undergoing a hard fall. Interestingly enough though despite rib fractures being common, one thing that is not commonly seen is a dislocated rib. Yes, despite whatever your internet searches might tell you, dislocation or subluxation of a rib is actually an extremely rare event even among the types of incidents mentioned a moment ago.
Why is this? What kind of joints connect the ribs to the rest of the body and why are they so robust? Well, we’re going to find out the answer to this and much more right now as we explore the costovertebral joints.
We all know that the vertebral column is formed from a series of rather irregular bones known as vertebrae, each of which articulate or form joints with its immediate neighbor above and below at intervertebral joints. One feature which specifically sets the thoracic vertebrae apart from other members of the vertebral column is the fact that they possess additional articular surfaces which are present in order to form articulations or joints with the ribs. This joining of the thoracic vertebrae with the ribs as a whole allows for the formation of the thoracic cage.
In our tutorial today, we’ll be working systematically through the anatomy of the joints found between the thoracic vertebrae and ribs, first looking at the bony framework followed by the supporting ligaments. We’ll have a look at the joints in both typical arrangements and atypical arrangements as there are some variation at different thoracic levels. And finally, we’ll finish up with some clinical points on the costovertebral joints.
Before we start, let’s have a quick look at this illustration to introduce ourselves to these joints and I do say joints because there are actually two joints that are formed when the ribs articulate with the vertebrae and these are the joints between the vertebral body and the head of the rib here and the joint that the tubercle of the rib makes with the transverse process of the vertebra over here. Now don’t be overwhelmed by all the terminology here. We’ll be looking at these again later on, but it’s worth keeping in mind at this point that there are two very separate joints that we’re going to talk about. So let’s get started with the bony elements to provide some structure.
So we’ve established that there are two bones which play a role in the formation of the costovertebral joints, and these are the thoracic vertebrae and as we’ve mentioned before, the ribs. So let’s take a look at the vertebrae first.
So here we’re looking at a typical thoracic vertebra from a superior view and we can see some characteristic features to tell us that this is indeed a member of this particular vertebral series. Firstly, let’s focus on the largest and most anterior part of the vertebra here which is the vertebral body. In this particular example, we can tell that this is indeed a thoracic vertebra by the somewhat heart-shaped appearance of the vertebral body and the fact that it is moderately sized relative to the rest of the bone. For comparison, I’ll show you an example of a typical cervical vertebra and a lumbar vertebra, just so you can appreciate the proportions here.
So you’ll notice that the cervical vertebra has a relatively small vertebral body while the lumbar vertebra has a much larger body relative to the rest of the bone. Between each vertebral body is an intervertebral disc which acts as a sort of shock absorber to the vertebral column as a whole and immediately posterior to the vertebral body is a space or canal known as the vertebral foramen. This is the conduit for the spinal cord and associated structures, and in the thoracic region, it tends to be round in shape.
Either side of the foramen are the pedicles, and moving a little more posteriorly or laterally, we come to the transverse processes. We can see them here in our lateral view here too. They project posterolaterally from the vertebral body. And just to orient ourselves here, this is a lateral view of the vertebral column and so we can see a variety of structures. The ribs adjacent to the bottom two vertebrae are in situ here. Posterior to each transverse process are the laminae of the vertebral arch which meet to form the spinous process here at the most posterior part of the bone which is the knobby piece of bone palpable in the back.
So let’s go back to the superior view to have a look at some other important bony features of the thoracic vertebrae – the articulation points – known as facets or fovea. So let’s begin first with the superior articular facet which is this superior-facing protrusion of bone highlighted here. So when the ribs are stacked on top of one another like they are here when seen from a posterior view, the superior articular facet of one vertebra forms a synovial plane joint known as the zygapophyseal or facet joint with the inferior articular facet of the vertebra above it. And though these are not specifically related to the costovertebral joints, it’s worth remembering that they’ll contribute to the movement of the thorax, too.
The remaining articulation points which we’re going to be looking at are involved in the costovertebral joints, so be sure to make special note of them as we work through them now. So first stop is this structure which is called the costal fovea or the costal facet, and the entire costal fovea is comprised of two separate demifacets – a superior costal fovea located on the superolateral border of the vertebral body and an inferior costal fovea on the inferolateral border of the vertebral body immediately above it.
The word fovea means a pit or depression and these surfaces have a concave shape to them to fit nicely with the head of the rib and to allow for multiplanar movement which we will see shortly. If we look at our lateral view, we can see that the head of the rib articulates with not one but two vertebral bodies and this means that there are three bones involved in most costovertebral joints. And these bones are of course, the rib, and its corresponding vertebrae. For example, if we look at the fourth rib, we can see how it articulates with the fourth thoracic vertebra as well as articulating with the vertebra above which is, of course, T3.
This one last final articular surface on most of the thoracic vertebrae that we need to talk about and that is this one here, the transverse costal fovea, also known as the transverse costal facet. It’s located on the anterior surface of the distal end of the transverse process and we’ll learn more about this in just a short while. In the meantime, let’s have a quick look at some of the bony landmarks on the rib and see how these structures fit together.
For the purposes of this tutorial, we’re going to just look at this part of the rib, the proximal or posterior part, but if you’re curious, you can check out our website to learn more about the osteology of the entire rib.
So we’re looking now at a proximal end of the rib and the proximal end of the rib is made of three distinct features. These three features are the head, the neck, and the tubercle. So starting at the head of the rib, we can see that there are two distinct articular facets separated by a crest, and these two articular facets will fit into the demifacets of the vertebral bodies that we saw earlier to make up the first of our costovertebral joints. The neck of the rib is the space between the head and the tubercle and is of variable length depending on the rib while the tubercle is this bony protrusion or eminence located between the neck and the body of the rib and is divided into two distinct parts.
Quite simply, the articular surface is the bony surface which, true to its name, is the part of the tubercle which articulates with the transverse process of the vertebra and then the nonarticular part has an equally important function. It’s rough in texture and acts as an anchor for the supporting ligaments of the costotransverse joint which we’ll come to a little bit later.
Okay, so that’s it for the bones that are involved in the costovertebral joints. Let’s have a look at how they fit together and the ligaments that supports these joints.
So as I said before, there are two joints that make up the costovertebral articulation and these are the costocorporeal joint located here between the vertebral body and the head of the rib and the costotransverse joint which is found here located between the transverse process of the vertebra and the tubercle of the rib. And let’s dive right in and look at the specifics of the costocorporeal joint first.
So the first question I can hear you ask is costo- what? I know it’s a bit of a mouthful, but anatomy usually has some pretty logical nomenclature, so let’s break this down to make some sense of it. So, costo- is a prefix that we hear often when talking about the ribs so costal cartilages, the intercostal space, and it translates from Latin to mean coast or edge. The -corporeal part of this term refers to the body of the vertebra as “corpus” is the Latin word for body. And understanding the roots of complicated terms like this one can sometimes help us remember their names.
Okay, so terminology lesson done, let’s get back to the anatomy. So over here we have our costocorporeal joint and it’s composed of three articular surfaces, all of which we have already identified. So, one, an inferior costal fovea which we said is located at the inferolateral margin of the vertebral body immediately above the rib in question. Two, we have the superior costal fovea located on the superolateral margin of the vertebral body, adjacent to the rib. And, three, of course, we have the head of the rib in question.
So, for example, the third rib articulates with the superior costal fovea of T3 and the inferior costal fovea of T2 above. And there are a couple of exceptions to this arrangement, but we’ll come to them once we have our head around the typical joints.
So the superior and inferior aspects of the head of the rib each have their own articular surfaces that fit nicely besides the vertebral bodies and though there are two very distinguishable parts of this joint, it’s all contained within one joint capsule and supporting ligament and is therefore considered to be just one joint. Within the joint, we can see that there are two distinct synovial cavities here separated by the intraarticular ligament and this is attached to the crest of the head of the rib and the intervertebral disc. So this is the first of our costovertebral joints. So to sum up, the costocorporeal joint is the first of our costovertebral joints and the costocorporeal joint is sometimes alternatively known as the joint of the head of the rib.
So there’s a second joint between the rib and the vertebra and as you might have guessed from the illustration, it involves the transverse process, and it’s called the costotransverse joint and is an articulation between the prominent landmark on the posterior border of the rib, the tubercle, and the transverse costal facet which we looked at earlier, hence, costotransverse.
Before we move on to the ligaments, let’s have a look where there are some atypical joints. Okay, let’s highlight the vertebral bodies T1 to T12 to remind ourselves where the rib should be. Okay, so if we look closely at the first thoracic vertebra or T1 over here, we can see that there is no inferior costal facet on the C7 vertebra. So this means that the first rib will only articulate with its own vertebral body. So that’s of course our first atypical arrangement. Rib one articulates only with its corresponding vertebral body.
If we move further down the spinal column to T11 and T12, we noticed two differences here. So, similar to T1, ribs eleven and twelve articulate exclusively with their own vertebral bodies as there’s no inferior articular facet on the vertebra above contributing to these joints. We can also see here that there’s no costal fovea on the transverse process of T11 and T12 either, meaning that there’s no costotransverse joints at these levels. Instead, the ribs pass anterior to and independent of the transverse processes.
Okay, so that’s it for the bones of the costovertebral joints.
Let’s have a look at the ligaments that hold these articulations together. So let’s start with some ligaments that support the thoracic vertebrae which in turn provides support to the thoracic cage as a whole. So looking at this lateral view, we can see a ligament that is attached to the anterior aspect of the vertebral bodies. This is the anterior longitudinal ligament. It transverses the anterior aspect of the vertebral bodies and the intervertebral discs from the base of the skull to the sacrum and works to reinforce and support the intervertebral joints.
The intertransverse ligaments also support the spinal column and they run from the inferior surface of one transverse process to the superior surface of the transverse process immediately below and they support the spinal column during lateral flexion. They are thick and sturdy in the thoracic region and they run perpendicular to the transverse processes which will help us distinguish them from some other ligaments close by.
Okay, so let’s move on to the ligaments supporting the joint of the head of the rib. And there are two ligaments here, one of which we’ve already seen. So this one here, the intraarticular ligament, holds the rib close to the vertebral body and it runs from the crest of the head of the rib to the intervertebral disc.
The second ligament supporting this joint is located outside of the joint capsule and this is called the radiate ligament and covers the anterior surface of the head of the rib. It forms a firm attachment to both of the vertebral bodies contributing to the joint.
Both of these ligaments contribute greatly to the robustness of the costocorporeal joint and ensure that the rib stays firmly attached to the vertebral bodies preventing it from dislocation. That being said, it does allow the head of the rib to rotate to a certain degree within the joint and it is this rotational movement that allows us to elevate and expand our ribcage on inhalation.
There are another three ligaments that support the costotransverse joint or called the costotransverse ligaments and oddly enough, they are the superior costotransverse ligament, the lateral costotransverse ligament and another commonly known as the costotransverse ligament. And for simplicity’s sake, let’s start with the lateral ligament.
So the lateral costotransverse ligament covers the costotransverse joint and extends laterally to the tip of the transverse process. On the rib, it is attached to the roughened nonarticular surface of the tubercle that we say earlier. So the main movement of this joint is a sliding motion in a superior to inferior direction which happens as the head of the rib rotates in the costovertebral joint. And this ligament protects the costotransverse joint and prevents excessive movement.
Next, we can see another ligament medial to the one we just looked at which is located in a region known as the costovertebral foramen which is this space here between the neck of the rib and the transverse process of the adjacent vertebra, running from the costocorporeal joint to the costotransverse joints.
Now it make a lot more sense for this to be perhaps called the medial costotransverse ligament, but it’s not. It’s most often just called the costotransverse ligament. However, some textbooks might refer to it as the inferior costotransverse ligament. It supports the position of the rib alongside the transverse process by creating a ligamentous attachment between the posterior aspects of the neck of the rib with the anterior surface of the transverse process of the adjacent vertebra. And this ligament prevents over-rotation and anterior displacement of the rib.
And the last ligament of interest for us today is the superior costotransverse ligament which we can see partially in this illustration and it is attached to the superior border of the neck of the rib and extends from the superior surface of the neck of the rib to the inferior border of the transverse process of the vertebra immediately above. This is the only costotransverse ligament to extend across two vertebral levels – the other two connect the rib and the vertebra of the same level.
And that’s it for the ligaments of the costovertebral joints. I hope you have a good idea now of why the costovertebral joints are so robust and strong. So we’ll summarize all of the costovertebral anatomy shortly to remind ourselves what we’ve learned today, but first, let’s have a look at a clinical condition affecting these joints.
So I mentioned briefly the movements of the costovertebral joints – the rotation at the head of the rib and gliding of the costotransverse joint – which are essential movements to allow for expansion and elevation of the ribcage during breathing.
Ankylosing spondylitis is a chronic autoimmune condition that affects the costovertebral joints and often other joins in the body, too. Inflammation of the costovertebral joints lead to pain and stiffness, often presenting as general back pain, and progression of the disease leads to a reduced mobility in the back and enforced expansion of the lungs. And what’s happening with disease progression is the degradation and fusion of the costovertebral joints that we discussed and the intervertebral joints between the intervertebral bodies.
So prognosis is dependent on disease severity, however, there are a number of treatment strategies pursued in clinical practice. For all sufferers of this condition, medications such as nonsteroidal antiinflammatory drugs commonly known as NSAIDs are used to relieve inflammation, pain, and stiffness. Other medications include TNF or tumor necrosis factor blocker or interleukin-17 inhibitor, both of which have a role in the inflammatory process in the body. This can help to prevent or delay progression of the disease. And physical therapy is also an important treatment which helps with pain relief in addition to promoting improved joint strength and flexibility. And finally, in severe cases, clinicians may recommend surgery for those with severe pain and joint damage.
Okay, so that’s it for the costovertebral joints. Let’s quickly remind ourselves of what we talked about.
So we started with the osteology of the vertebral bodies, looking at the vertebral body, the transverse and spinous processes, the pedicle, and the vertebral foramen in the middle. We also saw the articular surfaces of the thoracic vertebrae, the superior and inferior articular facets forming the intervertebral joints, the superior and inferior costal fovea located on the body of the vertebra, and the transverse costal fovea seen here on the transverse process.
We also looked at the morphology of the proximal or posterior portion of the rib and we pointed out the neck, the tubercle with its articular and nonarticular paths, and the head which has a superior and inferior surface and the crest in the middle. We then looked at the joints made up by the articulation of these two bones. The costocorporeal joint, also known as the joint of the head of the rib, which in most cases involve three separate bones – the rib and the corresponding vertebral body and the vertebral body above. The head of the rib forms a joint with two separate joint capsules.
The inferior border of the head of the rib shares a synovial bursa with the superior articular fovea of the same vertebral body and the superior border of the head of the rib shares one with the inferior articular fovea of the vertebral body above it.
This joint had two supporting ligaments – the intraarticular ligament between the crest of the head of the rib and the intervertebral disc and the radiate ligament encapsulates the entire joint. We saw that the costotransverse joint is formed by the transverse process of the vertebra and the posterior border of the rib and it’s supported by three ligaments – the lateral costotransverse ligament, the superior costotransverse ligament, and the costotransverse ligament.
Okay, so that’s all you need to know about the costovertebral joints. Don’t forget to check out the related atlases and quizzes to solidify and test your knowledge. Thanks for watching this video and happy studying!