 Good day everybody. This is Dr. Sanjay Sanyal, professor department chair. This is going to be a demonstration of the bones of the foot, more specifically the tarsal bones. Before I go to the tarsal bones, first let me divide the foot. The foot is divided into a forefoot and a midfoot and hind foot and the line dividing them is this line here. This is the torso metatarsal line, the junction between the tarsal bones and the metatarsal bones. In the actual living foot, the lateral margin, the midpoint of the lateral margin and the midpoint of the medial margin. If you join them, that forms the torso metatarsal line. So therefore the portion anterior to that is the forefoot, which includes the metatarsal bones and the phalanges. And the portion behind that includes the midfoot and the hind foot. The midfoot and the hind foot is also further subdivided by an S-shaped line. And that S-shaped line can be seen in this view, this line and this line. This is called the transverse tarsal line, also called the Chopa line. This is the line between the talus, navicular, calcaneus, cuboid. This S-shaped line, the transverse tarsal line divides the posterior part of the foot into a further posterior two-thirds, which is the hind foot and an anterior one-third, which is the midfoot. This is the next way of the foot torso planter view to show the torso metatarsal line and the transverse tarsal line. So therefore to summarize, the hind foot consists of talus and the calcaneus. The midfoot consists of the rest of the tarsal bones, which I shall mention just now. Forefoot includes the midtarsal and the phalanges. Having seen these classification of the foot, now let's take the tarsal bones one by one. Let's start with the talus. So this is the talus. This is the only bone which does not have a tendons attached to it or any muscles attached to it. This is the one which forms the ankle joint or the talocrual joint. So this is the body of the talus and this surface is the trochlear surface of the body of the talus. This is the one which articulates in the TBO fibular mortis to form the ankle joint. Then we have the neck of the talus, this groove. And this is the head of the talus, which articulates with the navicular bone. And we can see if you turn it, this portion of the talus is resting on this projection of the calcaneus. This shelf-like projection from the medial side of the superior border of the calcaneus is called the sustentaculum tali because like a shelf, it sustains the talus. If you want to take a look at the posterior aspect of the talus, you will find that there is a groove here. This groove is caused by the grisser-halus' longer tendon and that groove divides the posterior part into a lateral portion which is called the lateral tubercle of the talus and a smaller medial portion which is called the medial tubercle of the talus. This is an X-ray of the ankle, lateral view to show the parts of the talus and its articulation to the calcaneus and the navicular bones. Now let's mention a few clinical correlations pertaining to the talus. If, while driving a car, we suddenly press on the brakes very hard and we hypodorsiflex our foot, anterior-inferior edge of the tibia, impinges against the neck of the talus where my finger is located and it can lead to fracture of the neck of the talus. This is an X-ray of the ankle to show the lateral view, showing fracture of the neck of the talus as shown by the arrow. The second point which I want to mention is that in an X-ray, sometimes in a lateral X-ray, we can see an extra bone behind the talus. That is referred to as Ostrigonum. This Ostrigonum is actually formed in one of two ways. Either the ossification center of the lateral tubercle of the talus face to fuse with the rest of the talus or after it is fused, it can get evolved off in sports injuries, in which case we can see a separate bone behind the body of talus. And that separate bone which is actually a remnant of the lateral tubercle of talus where my thumb is located right now, is referred to as Ostrigonum. This is an X-ray lateral view of the ankle to show an extra bone called Ostrigonum behind the talus. Having mentioned the talus, now let's come to the calcaneus. The calcaneus is the largest bone and it's also referred to as the heel bone. And this is the portion which is in contact with the ground. The posterior part is called the tuberosity of the calcaneus. If you go to click a look, we will see the inferior surface. There is a medial tubercle, a lateral tubercle and an anterior tubercle. When we are standing, it's the medial tubercle which is in contact with the ground. Pustia part, the tuberosity, gives attachment to the tendo-calcaneus, which is one of the most powerful tendons in the human body. This is the one which articulates above with the talus. And the portion, you can see that this is the place which is called the tarsal sinus. And therefore, this is the subtalus joint. This subtalus joint has got two parts. The posterior part is the anatomical subtalus joint and the anterior part is referred to as the talo-calcaneal part of the talo-calcaneunavicular joint. And the two of them together constitute the surgical subtalus joint, which is the place where inversion and aversion takes place. This X-ray was already shown earlier. This time we would like you to notice the subtalus joint, the surgical anatomical and the tarsal sinus. I've already mentioned this projection is called the sustentaculum tali. And from here, there's a very strong ligament projecting across like this to the navicular bone. That is called spring ligament or the calcaneunavicular ligament. This is one of the most important components which maintains the longitudinal arch of the foot and it supports the head of the talus. And that's what constitutes the TCN joint, the talo-calcaneunavicular joint. If you were to take a look on the lateral surface of the calcaneus, we see this projection here. This is referred to as the fibular trochlea. And above that, there's the shallow groove and below that, there's the shallow groove. Fibular trochlea separates the fibularis brevis from the fibularis longus tendons. The fibularis longus tendon goes like this and it grooves the lateral side of the cuboid bone and then goes under it. The fibularis brevis goes like this and it gets attached to the tuberosity of the fifth metatarsal. Attached to this fibular trochlea is a fascia which acts like a pulley which allows the fibularis brevis and the flumbus tendons to act. Anteriorly, the calcaneus articulates with this bone here. This is the cuboid. So this is the calcaneo cuboid joint. Let's mention some important clinical correlations pertaining to the calcaneus. When a person lands hard on his heel from a height, calcaneus fracture is not very uncommon. And I can quote that from not only my clinical experience but also from my personal experience. The calcaneus is composed of cancellus bone inside and it crushes and fractures into multiple fragments, usually community fractured like an axial. These are x-rays to show fracture of the calcaneus. I would like you to notice the buular angle which is considerably decreased. And the way to diagnose it in x-ray is to see an angle on a lateral view. So for that I'm going to turn this. In an x-ray, we draw a line joining this part of the calcaneus with this part and project this line. So this is one line and the other line again take the second part of this line and join it with this line and extend it. So there is one line like this and another line like this and the angle between the two that is referred to as the buular angle which normally is between 20 to 40 degrees. If it becomes less than 20 degrees that indicates calcaneus fracture. This is an x-ray of the ankle lateral view to show buular angle and its normal value. The person has got a calcaneus fracture. Even after the calcaneus fracture is healed the person will have a little bit of lifelong disability in terms of slight flattening of the foot, a slight inversion deformity and pain while running. And I can quote all these three things from my own personal experience. So that is about the calcaneus. Now let's take the next bone. The talus articulates with a navicular bone. This is a boat-shaped bone that's what it's called navicular. And this medial projection that we see here this is called the tuberosity of the navicular bone. Normally this tuberosity is not in contact with the ground because of the longitudinal arch of the foot. Sometimes if this tuberosity is very large it can produce medial side foot pain. Navicular bone in turn articulates with the medial, intermediate and lateral cuneiforms. So therefore this is the talum navicular joint and these are the joints of the mid-tarsal bones. This is the cuboid. It is shaped roughly like a cube and this is the one which I said articulates with the calcaneus. And the cuboid in turn anteriorly articulates with the fourth and the fifth metatarsal bones. It also articulates with the lateral cuneiform bone. This is the calcaneo cuboid joint. On the lateral surface of the cuboid and on the inferior surface of the cuboid there is a groove. And that groove is formed by the fibularis-longus tendon as it goes across like this and it gets inserted onto the lateral aspect of the medial cuneiform and the base of the metatarsal. So this is the course of the fibularis-longus. At this juncture I can digress for one second to let you know that these same two bones the medial cuneiform and the metatarsal the medial side gives attachment to the tibialis anterior tendon. That was just to show the relationship. So that is the cuboid. Three cuneiform bones the medial, intermediate and lateral they respectively articulate with the base of the first, second and third metatarsals and the cuboid articulates with the base of the fourth and the fifth metatarsal. So therefore this segment constitutes the lateral longitudinal arch of the foot and this segment constitutes the medial longitudinal arch of the foot and the cuneiform bones they are called cuneiform because they are wedge-shaped. That means the dorsal surface is wide and if you were to look at the ventral surface the planter surface you'll find that they're very narrow. So they're a wedge shape and this is because of a purpose. This is what constitutes the transverse arch of the foot. The transverse arch of the foot is formed by the mid-tarsal bones and they are formed by these bones which we mentioned just now navicular the cuneiforms and the cuboid and they are maintained in place by means of two strong tendons. One of that is the fibrillaris longus which runs from lateral to medial and the other one is the tbls posterior which has got an extensive insertion on the calcaneus, cuboid, navicular, cuneiforms and the bases of the second, third and fourth metatarsals that exerts traction from the medial side. So therefore by the pull of these two strong tendons in opposing direction they help to maintain the transverse arch of the foot. So these are some of the points which I wanted to mention to you about the tarsal bones and their relationships and a few quick words about the longitudinal and the transverse arches of the foot. More will follow in the next video. Thank you very much for watching. 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