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Overview of the bones of the hand and wrist.
You already know that you use your hands for a lot of different activities like writing, communicating, and, of course, dissecting, and if you’ve been using our website, you may even be familiar with the muscles, nerves, and arteries that are involved in helping you perform each of these actions. But for this tutorial, we’re going to be diving a little deeper – as deep as you can go, in fact!
Join me as we venture past all the muscles on neurovasculature as we explore the bones of the hand!
Our first stop on our journey through the twenty seven bones of the hand will be this proximal cluster of eight small bones called the carpal bones, also sometimes referred to as the wrist bones. Next, we’ll move a little more distally and explore the five metacarpal bones which help form the bulk of the structure of the palm of your hand. This will then take us to our last stop, the fourteen phalanges which form the fingers, and to make learning these bones a little easier, we’ll divide them up into proximal, middle, and distal groups. We’ll then look between these various bones to name some important articulations that are found in the hand. At the end of the video, we’ll use what we learn and apply it to a relevant clinical scenario that relates to the bones of the hand.
Let’s begin our journey with the bones of the wrist, otherwise known as the carpal bones. And to avoid any confusion, let’s first get oriented.
Here we have an anterior or palmar view of the wrist and the hand. This means that this side – the pinky side – is medial and the thumb side is lateral. You’ll also see this respectively described as the ulna and radial aspects of the hand. Keep this in mind as we move forward. The last thing you want at this journey is to get disoriented.
Now that we know what we’re looking at, we can delve into the bones themselves. As we mentioned earlier, the carpals are a group of eight bones located at the proximal aspect of the hand. This cluster of small bones can be delineated into two rows – one proximal and the other distal. Grouping them off like this may make it easy to study them.
Let’s quickly run through the carpal bones of the proximal row moving from lateral to medial.
The most lateral bone of the proximal row is the scaphoid bone. It is named after the Latin word for “boat” which, I guess, makes sense because if you squint your eyes and tilt your head, it sort of looks like a small boat. The scaphoid bone has just one prominent landmark – the tubercle of the scaphoid bone – which is found on the palmar surface of the bone. Medial to the scaphoid is the crescent-shaped lunate bone. Its name is derived from luna referring to its crescent moon-like shape.
Medial to the lunate is the triquetrum or triquetral bone. The name is a little bit funny and hard to say, but it refers to this bone’s three corners giving it a somewhat triangular or pyramidal appearance. The fourth and final carpal bone of the proximal row all the way on the medial side is the pisiform form. I guess some anatomists long ago thought this little round bone looked like a pea since the word pisiform literally means pea-shaped. The pisiform is a sesamoid bone, meaning it forms within a tendon of another muscle – in this case, the flexor carpi ulnaris muscle.
So now that you’re a master of the proximal row of the carpals, we’re ready to move on to the remaining four carpal bones found in the distal row. Moving back to the lateral aspect of the carpals, we’ll first find the trapezium bone situated in between the scaphoid and the thumb. It has a quadrilateral appearance, meaning that it has four sides. To remember this bone in its location, you can think of the thumb swinging on the trapezium like a trapeze artist. Next is the shorter trapezoid bone, which is the smallest member of the distal carpal row and its named after its – you guessed it – trapezoid shape.
Medial to the trapezoid and smacked dab in the middle of the wrist joint is the largest of all the carpal bones, the capitate bone. The word capitate comes from the Latin word caput which means “head”, so you can think of the largest carpal bone being the head of the family. The eighth and final carpal bone is the hamate bone. It has a wedge-shaped appearance and beyond being the most distal and medially located carpal bone, you can identify this bone by its trademark feature, the hook of the hamate. Sometimes, however, this hook is not fused with the rest of the hamate bone and is then referred to as the os hamuli proprium.
Don’t forget, all of these carpal bones can also be seen from the posterior view as well, and if you remember their order from the anterior view, then all you have to do is flip it round and you’re good to go. See if you can work your way through it before I revealed the answers.
How did you go? I’m sure you did great. But you know, it’s pretty understandable if recalling the eight carpal bones is a little difficult since some of their names are pretty hard to pronounce. Fortunately, you can use a fairly simple mnemonic to help you remember their name and their order, and this mnemonic is Sam Likes To Push The Toy Car Hard. Hopefully, remembering this simple sentence can help you remember the names of all eight carpal bones.
Before we move on, it’s worth mentioning that each of these bones have their own unique bony features and articular surfaces. We won’t be covering every detail of these bones in this video, but if you’re curious, go ahead and check out our video dedicated to all things carpal bones.
Moving distal to the carpals will take us to this group of five bones called the metacarpal bones. Fortunately, you won’t have to learn any Latin while studying their names since they’re simply numbered one to five with the first metacarpal bone being the most lateral on the thumb side. And these long bones form the bulk of your hand as they span between the wrist and the fingers. Anatomists do like to fancily refer to this region as the hand proper.
The metacarpal bones themselves have a few bony features that are worth mentioning to. The first of which is the base of the metacarpal bones which is found at the proximal end of each metacarpal bone. This is the most variable part of this group of bones, meaning the base of each metacarpal bone looks different from the next. We’ll see later on that this bony feature plays an important role in articulating with the carpal bones.
Extending distally from the base are the bodies or the shafts of the metacarpal bones. This the long slender part of the metacarpal that gives it its characteristic long bone appearance and its palmar surface tends to be concave longitudinally. The third and final bony feature of the metacarpals that we’ll look at today are the heads of the metacarpal bones. Located all the way at the most distal end of the bone, the head of the metacarpal is responsible in articulating with the fingers or digits forming an important joint that we’ll look at in just a minute.
Okay, so now we can move on to our final group of bones found in the hand which are the phalanges. These fourteen long bones are what gives structure to your digits or fingers, and despite their small size, they are still technically considered long bones as each contains a proximal base, a body or a shaft and a distal head, but more on that in just a moment.
To make learning these little guys a little easier, we can divide them into three groups. Located most proximally are the appropriately named proximal phalanges. As you can see, there are five of these bones, one for each digit. These are the largest and longest of the phalanges. If we move a little bit further down the finger, the next bones we come across are the middle phalanges. Notice how there are only four middle phalanges with the thumb lacking in this case. And, finally, our journey ends all the way at the tips of the fingers with the distal phalanges. The thumb rejoins the group so that all five fingers contain a distal phalanx bone, and these are the smallest and the shortest of the phalanges.
Similar to what we saw with the metacarpals, each proximal, middle, and distal phalanx also has a base at the proximal end. Immediately distal to that, we see the base tapering into a slender body or a shaft, although you notice that the body of the phalanges is much shorter than what we saw with the body of the metacarpals. Lastly, located most distally at the end of each phalanx is the head of the phalanx. In the case of the distal phalanges, this is also known as the tuft of the distal phalanx.
Alright, great! Now that we’ve identified each bone of the hand and some of their bony features, let’s identify a few important joints that we find between these bones. The first joint that we’ll look at is the radiocarpal joint. Even though you could probably already guess which bones form this joint based on its name, let’s zoom in a little and look at this articulation in a little more detail. Alright, that’s a little bit better. Now, we can clearly see that this joint is formed by the distal end of the radius with the carpal bones, specifically the scaphoid and the lunate bones. This joint permits abduction and adduction at the wrist joint, also known as radial and ulnar flexion or deviation as well as flexion and extension at the wrist joint.
As for the carpal bones, there are several small joints formed between adjacent bones, however, these are collectively referred to as intercarpal joints. Most important of these is the midcarpal joint. As the name suggests, this joint is found right in the middle of the carpal bones between the proximal and distal rows that we looked at earlier. Also occurring at this joint are the flexion, extension, adduction, and abduction movements that we saw earlier with the radiocarpal joint.
Each of the five bases of the metacarpals that we talked about earlier articulate with the carpal bones to form five individual carpometacarpal joints. Like the metacarpal bones themselves, these joints are simply numbered one to five, with the first carpometacarpal joint found laterally on the thumb side. Along with the other two joints that we looked at so far, the carpometacarpal joints also permit flexion and extension at the wrist.
Moving distally, this takes us to the next set of joints called the metacarpophalangeal joints, and as you can see, these joints are formed by the heads of the metacarpal bones and the bases of the proximal phalanges. This joint allows you to flex and extend your fingers as if you are waving bye-bye to your friends after a long study session.
And, of course, we’ll find the last joint all the way at the fingers. These are the interphalangeal joints and they are found between the proximal, middle, and distal phalanges that we looked at earlier. Specifically, between the proximal and middle phalanges are the proximal interphalangeal joints while between the middle and distal phalanges is where you would find the distal interphalangeal joints. The thumb, meanwhile, only has one interphalangeal joint since it only has the two phalanges, and collectively, these interphalangeal joints allow your fingers to flex and extend, as if you’re making and releasing a fist.
Okay, so with the bones and the joints of the hand having been covered, we’re ready to move on and look at some of the anatomy in a clinical context.
So although each and every bone that we learned about today could potentially sustain an injury, we’re going to zero in on the very first bone that we talked about – the scaphoid. In particular, we’ll investigate the clinical considerations of a fracture to this bone.
So the scaphoid is most vulnerable during what’s called a FOOSH injury, and FOOSH is simply an acronym for falling on an outstretched hand, which describes the mechanism of injury, which is exactly what’s about to happen to our friend here. By reaching out his hand to break his fall, he’ll be directing all the force of his body weight right onto his wrist specifically his scaphoid bone. Ow!
The most common symptom of a scaphoid fracture are pain, swelling, and bruising over the wrist and thumb. This makes it kind of difficult to diagnose initially since it’s hard to distinguish a scaphoid fracture from just a badly sprained wrist. If a physician suspects a scaphoid fracture, they’ll likely order an x-ray to confirm the diagnosis. So, can you use your anatomical intellect to identify the fractured scaphoid bone? Remember that the scaphoid is the proximal row of carpal bones and is located laterally. Okay, so if you were able to pinpoint the fractured scaphoid here, then nice job! I think you’re pretty on your way to being a successful radiologist.
Treatment for a scaphoid fracture depends on how severe it is, and most mild fractures can be treated by immobilizing the wrist with the use of a cast. More severe fractures may require surgical interventions to repair the fracture with the use of pins or screws. Repairing the fracture in a timely manner is critical and this is because a fracture to the scaphoid could also damage the small artery that supplies it. If the blood supply to the fractured bone is compromised, this could lead to avascular necrosis or tissue death, and this causes a whole other list of problems that you certainly would rather avoid.
And on that happy note, we’re done! Go ahead and give yourself a big hand. You’ve made it through the bones of the hands tutorial.
Before we call it a day, let’s take a minute and review what we learned today.
So, we started off by identifying the carpal bones and remember that this group of eight short bones can be separated into proximal and distal rows. Next, we looked at five metacarpal bones which are the long bones that are located in the palm of the hand and remember that these bones don’t have unusual Latin names like the carpals, they’re just simply numbered one to five from lateral to medial.
In studying these bones, we learned that they have a base located most proximally which tapers and elongates into the body and ends distally as the head. We then moved on to the bones of the fingers called the phalanges and we saw that there are fourteen in total including five proximal phalanges. And just distal to the proximal phalanges are the four middle phalanges and remember that the first digit or the thumb does not have a middle phalanx. And, finally, we reach the fingertips which are comprised of the five distal phalanges.
After learning about the bones themselves, we studied the articulations that can be found between them starting with the radiocarpal joint, which is the articulation between the distal end of the radius with the scaphoid and lunate bones. Then we moved a little distally and saw the midcarpal joint found between the proximal and distal row of the carpal bones. The carpometacarpal joint was next, which is the joint formed by the distal row of carpal bones with the bases of the five metacarpals. The heads of the metacarpals, meanwhile, articulate with the proximal phalanges to form the metacarpophalangeal joints.
Finally, between all the individual phalanges, we study the interphalangeal joints which we broke up into proximal interphalangeal joints occurring between the proximal and middle phalanges and distal interphalangeal joints which are found between the middle and distal phalanges. And remember that since the first digit only has two phalanges, it only has one interphalangeal joint.
Finally, we examined the clinical implications of the scaphoid fracture and this included looking at the FOOSH mechanism of injury with pain and swelling as the key symptoms and we identified what this injury looks like on an x-ray and discussed immobilization and surgery as potential treatment options to help heal the fracture and prevent avascular necrosis.
And there you have it! I hope you’ve enjoyed your tour through the bones of the hand. Happy studying and see you next time!