 Good day, everybody. This is Dr. Sanjay Sanyal, Professor, Department Chair. This is going to be a demonstration of the carpal bones and their associated joints. So you're seeing the skeleton, the articulated skeleton of the right side. Just to bring up to speed, this is the ulna. This is the radius. This is the radiocarpal joint, and these are the carpal bones. These are the metacarpals. So this is the metacarpal of the thumb, second, third, fourth, and fifth, the little finger, and these are the phalanges. Is this the x-ray of the hand of Rungin's wife when he first discovered x-rays? Having mentioned these points about the carpal bones, now let me mention a few quick words about the joints themselves. If you notice that this is the lower end of the radius. The lower end of the radius is the only one which articulates with the carpal bones. The ulna does not articulate in the carpal with the carpal bones. Therefore, the wrist joint is formed essentially by the radiocarpal joint, and which are the two bones, only the lunate and the scaphoid. Only these two bones participate in the joint. PC-Pomp-Riguitra does not participate, and the distal-row of carpal bones, of course, they participate only in the carpal metacarpal joint, which I shall mention just a little later. This is the x-ray of the rest of the child showing the radiocarpal articulation. Note the distal epiphylluses of the radius and the ulna. The reason why the ulna does not articulate is because there is a triangular ligament, also called the articular disc. The X of the triangular ligament is from the ulna's dilate process, and the base is attached to the radius. Therefore, this articular disc separates ulna from the carpal bones. This articular disc not only holds ulna and the radius together, but it also plays a very important role in the pivot movement of the pronation, which I have mentioned in a separate video. This is the coronal MRI of the wrist joint to show the carpal bones, the radiocarpal articulation, and the articular disc between the ulna and the carpal bones. Having shown the bones of the radiocarpal joint, the wrist joint, now let me demonstrate some important clinical functional aspects of the movements of the wrist joint. So this is the neutral position of the wrist. This is extension of the wrist, also called dorsiflexion. This is flexion of the wrist, also called just flexion. This is ulna deviation of the wrist or adduction. This is radial deviation of the wrist or abduction of the wrist. So let's take a look at which are the muscles which are acting. When we do flexion of the wrist, it's a combined action of the flexor carpal radialists and the flexor carpal ulna wrist. And you can see the tendon standing up here. When we do extension of the wrist, it's a combined action of the extensor carpal radialists longest and previous, which are inserted onto the second of the third metacarpal bones and the extensor carpal ulna wrist, instead of the fifth metacarpal bone. So this is how we do extension and this is how we do flexion. What about abduction of the wrist? This is achieved by the combined action of flexor carpal radialists and the extensor carpal radialists longest and previous. And what about adduction of the wrist? This is achieved by the combined action of the flexor carpal ulna wrist and the extensor carpal radialists. So that brings us to a very important clinical aspect. Each of these muscles, if you notice, they are supplied by different nerves. So therefore, when we are doing a flexion of the wrist, flexor carpal radialists is supplied by the median nerve, the flexor carpal ulna wrist is supplied by the ulna nerve. When we are doing extension of the wrist, all the muscles are supplied by the radial nerve. Therefore, if a person has got paralysis, injury of the radial nerve, especially in the region of the elbow, then the person will not be able to do extension of the wrist and the wrist will fall down by gravity and the person will not be able to elevate the wrist against resistance or against gravity and that is called a wrist drop. That is one abnormality that is very well known. What happens if a patient has got injury of the ulna nerve in the elbow? One attempted flexion, flexor carpal ulna wrist cannot work. Only the flexor carpal radialists will work. So therefore, on attempted flexion, the hand will deviate towards the radial side. Contrary wise, if a person has got an injury of the median nerve in the region of the elbow, flexor carpal radialists will not work. So therefore, when the person tries to flex the wrist on attempted flexion, the hand will deviate towards the ulna side because of the unilateral action of only the flexor carpal ulna wrist. So these are the points which I want to mention to you about the functional aspect of the movements of the wrist and the effect of lesion of each of these three nerves. There is a ligament extending from the radial styloid process to the first metacarpal bone and that is the radial collateral ligament. Similarly, there is a ligament extending from the ulna styloid process to the femuricarpal bone. There is an ulna collateral ligament of the wrist joint. If this radial collateral ligament is torn, that is called bull rider's thumb. It is seen in those who ride mechanical boots or those who use bull riding as a sport. Let me mention now a few quick words about the carpometacarpal joint itself. Carpometacarpal joints, the first carpometacarpal joint, the fourth and the fifth, these are biaxial tidal joints. And you can see that if you hold a pencil, like for example, imagine this is a pencil and I am holding it here. When I am holding it loose, it is straight. But when I hold it tightly, it bends. I am going to do it again. When I am holding a pencil loose, it is straight. When I tighten it, it bends. Loose, tight. This is because of the rotary movement of the fifth and the fourth carpometacarpal joints, which are biaxial saddle shaped joints. The first, fourth and the fifth are biaxial saddle joints. Now let's take a look at the metacarpophalangeal joints. The metacarpophalangeal joints are between the heads of the metacarpals and the basis of the phalanges. These are also biaxial. These are condyloid joints. They are capable of movement in two axes, but there is also possibility of circumduction. So therefore, when we look at the thumb and the fingers, we can see that we can do flexion extension, we can do abduction adduction and we can do circumduction also. So that's why they are called biaxial condyloid joints. The heads of the metacarpals are the ones which form the knuckles. If you hit a hard surface with your knuckle accidentally while you are punching, you can have a fracture of the neck of the metacarpal bone and then the knuckle will be depressed and that is called a dropped knuckle. The digital bones, the phalanges, as we all know, the thumb has got only two. Others have got three. The flexor digital and superficialis gets inserted onto the middle phalanges and the profundus goes through the split portion and gets attached to the distal phalanges. So therefore, to test for the FDP, we have to keep the middle phalanges straight and then ask the patient to flex the distal phalanges. We can get a condition called skier's thumb. When a person is skiing and he accidentally falls, he hyper abducts his thumb and that leads to dislocation of the first metacarpal phalangeal joint, the joint between the metacarpal bone and the first digit of the thumb. And therefore, there's a tear of the ligament, the first metacarpal phalangeal joint, there can be a version fracture of the head of the metacarpal bone, the thumb will be hyper abducted and that condition is known as skier's thumb. So these are some of the points which I wanted to mention to you about the skeleton of the hand, the wrist, the palm, the carpal bone, so constituted pathologies. Thank you very much for watching. Dr. Sanjay Sanyal signing out. If you have any questions or comments, please put them in the comment section below. Please like and subscribe. Have a nice day.