 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 articulated skeleton of the right side. Just to bring up the 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. It is said that this is the x-ray of the wife of Rungin, the discoverer of x-ray, though this has not been verified. So, let's focus on the carpal bones on the right side. We see this one here. This is the PC form. Under that, we see the next bone. That is the triquetra. Then we have the lunate. Then we have the scaphoid. Then we have the trapezium. Then we have the trapezoid. Then we have the capitate. The habit. This is the planing x-ray of the right hand to show the carpal bones which have been labeled. And this is the coronal MRI of the hand to show the carpal bones which also have been labeled. I'm going to repeat these carpal bones again on the left side. So, now I have shifted to a skeleton of the left side. Here, again, you can see this is the ulnar side. This is the little finger and this is the thumb. Here, we can see only the carpal bones. Just to regard for the time being, these beads here, these have been there just to hold the bones in place. This is the PC form. The triquetral. The lunate. Scaphoid. Trapezium. Trapezoid. Capitate. Hamate. So, these are the carpal bones that we can see on the left side. This is an enlarged x-ray of the left hand to show the carpal bones. They have not been labeled. It is for you to label them. Now, let's come back to the previous skeleton. The PC form. It is like a seed that's why it's called PC form like a seed. This is, in effect, a sesamoid bone within the tendon of the flexor carpal ulnaris. The flexor carpal ulnaris comes like this. This bone is inserted within that tendon and extending from this PC form bone, there is a ligament, which goes from the PC form bone to the hook of hamate and that is called the piezo-hamate ligament. Therefore, the piezo-hamate ligament can be considered as an extension of the tendon of insertion of the flexor carpal ulnaris. Piezo-hamate ligament incidentally forms the boundaries of a small canal, approximately an inch or so, which I shall mention later, which is called the caeons canal. So this is the PC form bone. It's a small seed like bone. Under that, we have the trichotron. This is roughly shaped like triangular pyramid. That's why it is called trichotron. To understand the shape, I will again take you back to the previous one. This is the other skeleton and you can see that this is the trichotron and it looks somewhat like a triangular pyramid. Then we have the lunate. I'm showing the other skeleton, the one on the left hand. Lunate means like half a moon. And you will see, if I turn it, you'll see that it looks like a half a moon. This is the view of the half a moon. That's why it is called lunate. Then we have the next moon. This is the scaphoid. The scaphoid has got a narrow portion in the middle and that is called the waist of the scaphoid. So therefore, this is the distal portion, this is the proximal portion. We can have some important clinical correlations pertaining to the lunate and the scaphoid. If a person falls on his hand, he can have dislocation of the lunate into the carpal tunnel and that can produce carpal tunnel syndrome. So that is one important point to be remembered about the lunate. Similarly, if a person falls on his outstretched hand, he can have a fracture through the waist of the scaphoid. The blood supply to the scaphoid comes from distal to proximal and it is supplied by the palmar carpal branches of the radial artery. So therefore, if there's a fracture through the waist of the scaphoid, the proximal portion, the portion which articulates with the radius, that undergoes avascular necrosis and then it can never unite with the rest of the bone and that can produce permanent wrist disability to the groove. That is a groove and that is called the flexor carpal radialis tunnel. The flexor carpal radialis goes through that and it's partially inserted onto the trapezium and it gets inserted onto the second metacarpal bone. That's the primary insertion and there may be a small insertion on the third metacarpal bone. So this is the groove for the flexor carpal radialis, the flexor carpal radialis tunnel. The trapezoid, both of these are like a trapezium. This is a smaller one, that's why it is called trapezoid. Capitate, this is the largest bone and it's like a head, that's why it's called capitate and the hamate is like a hammer and it's got a very prominent projection and that's called the hook of the hamate. This hook of the hamate can be fractured, especially if a person falls on his hand. Moreover, this hook of hamate also forms the boundary of the gion canal which I mentioned earlier. In either of these situations, it can produce distal ulnar nerve neuropathy and can produce ulnar claw hand. This is a clinical picture of a patient with distal ulnar neuropathy producing ulnar claw hand. Having mentioned these points, now let me mention to you some important attachments of the flexor retinaculum here. So for that, I'm going to come back to the previous skeleton. Again, this is the busy form bone. There's a tough ligament which extends across the carpal bones and that is called the flexor retinaculum. It's also called the transverse carpal ligament. It is attached medially to the busy form bone and to the hook of hamate, roughly rectangular in shape. Laterally, it is attached to the tubercle of the scaphoid, tubercle of the trapezium. So therefore, it stretches across like this and therefore, it converts this concave surface into a tunnel and that is referred to as the carpal tunnel. As a result of this carpal tunnel, we have the four tendons of the flexor digital superficialis with their sinavir sheath and the four tendons of the flexor digital profundus, also the same common sinavir sheath. These combined sinavir sheath is incidentally referred to as the ulnar bursa. And then there's the tendon of the flexor polisus longus which goes in its separate sinavir sheath that is called the radial bursa. So therefore, these nine tendons and also passing through the carpal tunnel is the main trunk of the median nerve which goes through the carpal tunnel and it supplies the muscles of the thinar evinence. So therefore, in carpal tunnel syndrome, there can be hundreds of causes of carpal tunnel syndrome, median nerve can get compressed and it can produce weakness of the thinar muscles and numbness, tingling and peristicia of the lateral three and a half digits. But the palmar skin will be spared because the skin of the palm is supplied by a separate branch which goes outside the carpal tunnel. So that is about the carpal tunnel. Having mentioned that, now let me come back to this and mention a few quick words about the guion canal. The guion canal is a small, approximately 3.5 or 4 centimeter canal which extends like this. It is bounded medially by the pisiform bone and the pisohamet ligament. So proximal medially, it is the pisiform bone and pisohamet ligament. Distrolaterally is the hook of hammet. The floor is formed by the transverse carpal ligament and the roof is formed by the volar carpal ligament and that is called the guion canal. And that is the one which gives passage to the ulnar nerve. Remember the ulnar nerve does not go through the carpal tunnel but it goes through the guion canal. And after it passes through, it divides into a deep branch which supplies the muscles of the hand. So peristia branch which supplies the skin of the medial one and a half digits in the palm and it gives a communicating branch to the median nerve. So therefore in the guion canal, the ulnar nerve can be compressed and that is called the guion canal syndrome. Another condition is called handlebar neuropathy. People who are riding motorcycles for long hours, they can compress the nerve in this region and that is called handlebar neuropathy. So these are some of the points which I wanted to mention to you about the skeleton of the wrist, the carpal bones, the carpal tunnel syndrome and the guion canal syndrome and the associated pathologies. Thank you very much for watching. Dr. Sanjay Sanyal, Sanyao. 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