Biomechanics of Anatomy: Ribs and their Articulations

00:00 We're going to change course now and talk about biomechanics. How do the ribs move, how do their articulations matter and what difference does this make? Because the costochondral joint is a joint and where the ribs attach to the sternum is going to have motion. It might be a cartilaginous joint and it's hyaline cartilage, it is an articulation that has 2 ends to it so it's a bone that’s moving at both ends and it’s got a lateral end that has cartilage that then attaches to the sternum. So it's a unique joint that is found in the front, found in the back. It is covered by periosteum that then helps it move, helps smooth out the motion and it is an interlocking joint that’s lock to the sternum and lock to the rib. Let me get to rib motion, because if you watch somebody breathe. If they’re breathing comfortably, if they’re healthy it's normal. You take a deep breath in, the rib cage expands. Pump handle motion where the rib comes up in the front, bucket handle motion where it expands, diaphragm goes down, lung gets expanded and it looks like it's nice fluid motion. It should be symmetrical but it's also something where you are going to notice that there are changes that are not easily apparent. There are changes in the ribs and how they connect to the spine and the thoracic vertebrae and their role in breathing and how the angulation of the head of the rib is going to affect how deep a breath you get and how much you are able to breathe and how much you are able to expand your thorax. So in looking at the costovertebral articulations and ligaments, we do know the articulations are pretty strong, they are pretty extensive and they tend to cover the tubercles and the head of the ribs so you can see it. Rib 1, 10, 11 and 12 are false ribs. They only articulate with their own corresponding vertebral level, so the motion will not be as limited when people are sick. So you may have 1 primary rib lesion initially that then spreads but you're still going to have motion in ribs that don't require and are not attached to 2 vertebrae. So that's why you're still going to get expansion of the rib cage. It's just going to be unequal expansion and the interosseous ligaments that are between the 2 demifacets are going to move comfortably when a person is healthy. When a person is ill, you're going to start seeing limitations and you're going to start to see compensatory changes in both the ribs and the vertebrae. When you do the exam and you check rib levels, you will generally notice tenderness both above and below the area of dysfunction. One of the things we also tend to look at is a problem 1 rib or multiple ribs. Is it 1 vertebra or multiple vertebrae? It’s usually a different muscle group that's affecting it. If it's multiple ones or it is also possible that it’s 1 primary that then caused a ripple effect to affect the ribs above it. When we look at the ligaments, there are 3 bands that attach the rib to the vertebrae and you want to look at the head of the rib that is attached to the vertebrae and the intermediate level and the inferior level. So, again it's tightly bound to the vertebrae. Here’s another picture of the ligamentous bonding and ligamentous attachments and this is meant to show you how extensive. So if you're dissecting it you're not going to see the ribs easily where they attach because they're going to be covered and really obscured by ligaments and I just wanted to share the nerves there as well. While most of the injuries we see tend to be in the thoracic outlet, there are pains that are usually more minor and more fleeting but they are at every rib level and people are going to get chest pain from sitting from long periods of time, from using their ribs in an asymmetric manner, from being twisted and staying in that position for too long, sitting at a desk too long. All of those are going to get some feedback from the autonomic nervous system of the thorax that may limit rib motion. I just wanted to focus a little bit on the vertebrae so you can see where the ribs are attaching and realize again the head is attaching to one vertebra and then the transverse process is attaching at the level above as a separate vertebra. So, again the motion is determined by multiple vertebrae and the attachment to the ribs. Another picture with the articulations showing the tubercle attached, showing the ligaments attached and showing that it is going to be multiple levels that are involved with every motion of the rib. We also have to realize that you have muscles multifidus, rotatores small usually go 1 segment as well as the longer muscles and thicker muscles, longissimus, iliocostalis on multiple levels that are going to be affecting your breathing and affecting the motion. We also have the interosseous areas, the nucleus pulposus annulus fibrosus, that are going to be involved and have some effect on ribs. So when you have an intervertebral issue, the ribs are more likely to start developing tenderness, pain problems and need to be paid attention to as well and may actually need treatment secondary to the main problem which is often the vertebral issue. So, just take a look at the ligaments. Again, you have the interosseous, the posterior and the superior that are important to note. Just pointing out that as we go down from rib 1 to 10 the ribs get bigger and we are going to see a smaller angle so you are still going to have bucket handle motion below and pump handle motion above and that's going to be determined by the angle and by the flexibility and the ability of the ribs to move. It is three-dimensional motion, it is the curvature that is changing and lifting the chest wall where the typical ribs will have both pump handle and bucket handle and again focus on how the thoracic spine is involved with breathing because it is one structure. In looking at the sternoclavicular motion, it is triaxial motion that is a saddle joint. You are going to have motion occurring in multiple directions and the synovial joint that is part of the sternomanubrial junction is also going to affect motion and the back in the scapula are going to feel it as well and that's just something to be aware of. So, the sternoclavicular joint actually has 2 synovial joints in it, anterior and inferior. So you'll have 2 fluid sacs in there to help the motion occur in different levels. The rib motion in top tends to be pump handle, it is an anterior-posterior motion and it's more prominent in the upper ribs. That is something you need to know and that is high yield.

07:24 Pump handle motion describes motion in the sagittal plane, so it's anteroposterior motion and more prominent in the upper ribs particularly ribs 2 and 3. Bucket handle is motion that is up and down, expands the chest wall cavity, seen in the most lateral aspect at the lower end of the ribs that are then being brought up so that they are even and more on par with the front and the back of the ribs and even though it's still coming down you'll see it and it will follow easily. So, again bucket handle motion is the ribs are coming down and they're coming up in order to increase the chest wall cavity, increase intrathoracic pressure, pull the diaphragm down and allow the motion to occur and that is more prominent in the lower ribs. Again, the rib motion is something we're going to have to focus on. During inspiration, you're going to see the bucket handle motion and you want to make sure that you see it expand and relax for all of inspiration and all of expiration and you want to see it come down fully. If not, then you may have a rib that is stuck and not allowing for the optimal expansion of the chest wall cavity and breathing. Pump handle and bucket handle motion occur together. You're going to see it at the same time. We tend to separate it out for evaluation but the change in the shape of the chest cavity is really what’s happening and both motions together are what are affecting it. Rib 11 and rib 12 that don't have attachments to the front of the cavity are going to have what's called caliper motion and caliper motion is really motion at the edges more so than in the thoracic spine. So that's only 11 and 12 but without sternal attachment it's just the distal end that is coming anteriorly but does not quite make it anteriorly and it's muscle attachments that are separate that are causing it. So the muscle functions are important for the false rib motion and for the caliper motion and they will move somewhat posteriorly and inferiorly going in an opposite direction, again helping the expansion of the chest wall cavity.