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Foot & Ankle: Introduction
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Foot & Ankle: Introduction
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Language: EN.
Segment:0 .
MATTHEW CONTI: Hello, my name is Matthew Conti and I'm an Orthopedic Surgeon with a focus on foot and ankle orthopedic surgery. Today we are focusing on an introduction to foot for this module. We will focus on the bony anatomy of the ankle and foot, and the muscular and nerves of the anterior compartment, lateral compartment and posterior compartment. All right, let's get started. So the ankle joint is made up of the tibia, fibula and the talus.
MATTHEW CONTI: So the tibia comprised, is comprised of the medial malleolus, the posterior malleolus and then the fibula makes up the lateral malleolus and this articulates with the talus in the foot to allow the foot to dorsiflex and plantar flex. The ankle joint is a hinged joint. So there's the motion primarily through the ankle is up and down or dorsiflexion plantar flexion. When the foot is everting or inverting or there's accommodation on uneven ground,
MATTHEW CONTI: this motion comes through the subtalar joint. So the subtalar joint is made up of the talus and the calcaneus and typically this allows your foot to accommodate on uneven ground and evert or invert, depending on, depending on how uneven ground takes you. The next joint, the more distally in the foot is the talonavicular joint. The talonavicular joint is obviously made up of the talus and the navicular.
MATTHEW CONTI: There is some rotational motion through this joint, and you also actually have some dorsiflexion and plantar flexion through the talonavicular joint. So if someone, if a patient has an ankle fusion where the ankle no longer moves, they actually are able to move up and down through the talonavicular joint in their foot. The talonavicular joint also has inversion and eversion motion for the foot.
MATTHEW CONTI: And so this is the navicular bone here and then, this again is the talus. Moving more distally, the midfoot is made up of the medial cuneiform, the middle cuneiform, the lateral cuneiform and the cuboid. So if you can see on the model, the medial cuneiform articulates with the base of the first metatarsal, and this creates the first tarsometatarsal joint. The middle cuneiform articulates with the base of the second metatarsal, and this creates the second tarsometatarsal joint
MATTHEW CONTI: and the lateral cuneiform articulates with the base of the third metatarsal, and this creates the third tarsometatarsal joint. And so you can see that for each cuneiform there's one metatarsal base that's associated with it but when we get to the cuboid, the fourth and fifth metatarsals at their base, they actually articulate with the cuboid and this creates the fourth tarsometatarsal joint and the fifth tarsometatarsal joint. The bone,
MATTHEW CONTI: these bones of the foot, as we've kind of already discussed, are the metatarsals. So you have the first, the second, the third, the fourth and the fifth metatarsals. While the first three metatarsals are rigid and that really allows you to push off. The fourth and fifth metatarsals are very flexible at the fourth and fifth tarsometatarsal joints and so this allows the foot to accommodate, again allows your foot to accommodate on uneven ground
MATTHEW CONTI: and is one reason why we actually never fuse the fourth and fifth tarsometatarsal joints, because they need to be flexible to allow your foot to accommodate. While the first three tarsometatarsal joints can all be fused with little functional compromise to the foot. Then, as we move more distally, we have the first metatarsophalangeal joint or the hallux metatarsophalangeal joint, and the hallux is just the name for the big toe.
MATTHEW CONTI: And so this is the joint where you think about a bunion or you can get arthritis at this joint where the joint doesn't move as well. And so this is an important joint in the, in the foot and we can sometimes we fuse this or we have to correct a bunion deformity. That's a little bit beyond the scope of what we're talking about here but again, this is the first metatarsophalangeal joint.
MATTHEW CONTI: And then we have your lesser metatarsophalangeal joints, the second, third, fourth and fifth metatarsal phalangeal joints. And then finally we have the phalanxes. So you have the proximal phalanx for each foot and then a distal phalanx for the, for the hallux and then for the, for the other toes, they have a middle and distal phalanx except for the fifth toe, which sometimes doesn't have a middle phalanx.
MATTHEW CONTI: And so that, that's the primary bony anatomy of the foot. So let's talk about just the muscle, the muscular anatomy of the foot. So the anterior, there's four compartments around the foot. There's an anterior compartment. There's a lateral compartment and there's two deep posterior compartments of the or a deep and superficial posterior compartment in the foot.
MATTHEW CONTI: And so the idea is that the anterior compartment of the leg really allows the foot to dorsiflex and so it's your extensor so your tibialis anterior or your long extensors to your toes. All are in the anterior compartment. So if you just think when your foot dorsiflexes or moves up the tibialis anterior muscles pulling your foot up and then when your big toe flexes, the extensor hallucis longus brings your big toe up
MATTHEW CONTI: and that's also in the anterior compartment. And then the lesser toes are moved by the extensor digitorum longus. As we move to the lateral compartment for the musculature of the lateral compartment, the lateral compartment primarily is composed of the peroneal tendons. And so you have your peroneal brevis tendon. And that tendon comes right behind the fibula and inserts on the base of the fifth metatarsal here.
MATTHEW CONTI: And that primarily everts the foot right? So your brevis comes in here and then through your talonavicular joint. Your foot everts and moves outward. And then you have right behind that the longer tendon is the peroneus longus tendon and that actually comes all the way underneath the foot and inserts all the way at the base of the first metatarsal. And so that muscle helps to actually plantar flex your first metatarsal bone there.
MATTHEW CONTI: And then finally, in the posterior compartments, you have your gastrocnemius muscle, which leads your gastrocnemius muscle and your soleus muscle come together and they form your Achilles tendon and that allows you to plantar flex your foot. We've all heard of Achilles tendon ruptures. Those are very important in sports and even in normal activity.
MATTHEW CONTI: And that typically occurs in the mid substance and that is that tendon again is comprised of the gastrocnemius and soleus muscles. And then you have the tendons of the foot that plantar flex the foot and the toes. And so you have your flexor digitorum longus and your flexor hallucis longus, which do exactly what they sound like. The flexor hallucis longus comes around and it flexes your big toe down.
MATTHEW CONTI: The flexor digitorum longus flexes your toes. And so actually the flexor digitorum tendon is closer right behind the medial malleolus, almost right behind the medial malleolus. And then the flexor hallucis longus is actually a little bit more lateral. But then when they come into the foot, in the middle of the foot at the knot of Henry actually, they cross and so your flexor hallucis longus goes to your big toe and is coming kind of like this way
MATTHEW CONTI: and and your flexor digitorum longus is coming more this way towards your lesser toes. And so an easy way to remember the tendons in the foot where they go right by the medial malleolus is Tom, Dick, and a very nervous Harry. And so Tom is your posterior tibial tendon. We haven't talked about that yet, but that is really intricately associated with the medial malleolus comes around and then inserts right here on the navicular.
MATTHEW CONTI: And so for patients with flat feet, often that tendon is overworked because the job of that tendon is to hold up your arch when you push yourself forward. That's the posterior tibial tendon. And then right behind that, that's Tom. Dick is the flexor digitorum longus tendon which runs right behind that again goes under the foot and flexes the toes down. A very nervous Harry is the artery, artery vein and tibial nerve.
MATTHEW CONTI: And then Harry is your flexor hallucis longus and actually the flexor hallucis longus sometimes on the back of the talus, there's an extra piece of bone called an os trigonum, which is an extra extension of bone so that can be back here. And what you can imagine is that as the flexor hallucis longus is running right around here, sometimes it gets pinched right along that extra piece of bone
MATTHEW CONTI: and often that happens in ballet dancers because they go on pointe or they do relevé where they go up on their foot and they really plantar flex their foot, and that everything gets caught in the back of their ankle. Now let's move on. Now that we've talked about most of it. Now that we've talked about the muscles and the tendons and the foot and the ankle, let's briefly go over the nerves and the arteries.
MATTHEW CONTI: And so again, going back to the anterior compartment, you have the anterior tibial artery and then you have the deep peroneal nerve. And so the anterior tibial artery comes down and then goes across the foot. Then you have the superficial peroneal nerve in the lateral compartment. So the superficial peroneal nerve comes in is in the lateral compartment.
MATTHEW CONTI: It helps to innervate the peroneal tendons both the brevis and the longus and then it actually crosses about 10 centimeters from the distal tip, 10 to 12 centimeters from the distal tip of the fibula, and it crosses across the foot. And so one interesting thing is that while the dorsalis while the deep peroneal artery, while the deep peroneal nerve comes all the way down and it's sensory innervation is the first web space, the superficial peroneal nerve, while starting in the lateral compartment, crosses the fibula and then goes to the front of the foot and then actually supplies the innervation to the top and the inside and the top medial part of the foot.
MATTHEW CONTI: And so what happens is that if you have an ankle fracture, that's a little bit higher. Sometimes when you're doing your approach to the ankle, the superficial peroneal nerve can be in your way 10 to 12 centimeters above the distal tip of the lateral malleolus. And then it actually crosses your field and sometimes when you're doing work in the midfoot or even on the bunion, the superficial peroneal nerve can be in the way because it comes across
MATTHEW CONTI: and there's actually a branch called the dorsal medial cutaneous nerve that comes all the way across the foot and innervates right over the bunion, or medial eminence of the medial part of the foot, medial part of the hallux MP joint here, and supply sensation here. So the superficial peroneal nerve supplies a lot of sensation to the top of the foot.
MATTHEW CONTI: And then finally in the posterior compartment where you're going to think about the tibial nerve, which is running and innervating all of the muscles of the posterior compartment, and then running and innervating and causing and allowing sensation to the bottom of the foot. And then you're going to have your posterior tibial artery, which is also running in that location. And that's part of the and a very and a very nervous Harry.
MATTHEW CONTI: And so your nerve is the tibial nerve and your artery is the posterior tibial artery. The other two sensory nerves that you have to think about in the foot and ankle are the sural nerve and so the sural nerve is innervating kind of the very lateral border of the foot and runs kind of very posteriorly here. Sometimes when we're doing Achilles tendon repair, the nerve can be in the way because it can cross the Achilles tendon and be kind of has a variable course.
MATTHEW CONTI: And then also sometimes when we're cutting, sometimes we cut the calcaneus for different procedures and it's often right in the way on the lateral side of the foot so you have to think about that. And then finally, the other nerve that you have to think about that sensory is called the saphenous nerve and it comes all the way down the leg and then innervates really the very medial aspect of the ankle here.
MATTHEW CONTI: And so that can be in the way if you have a medial malleolus fracture for an ankle as part of your ankle fracture, sometimes when you do your approach there, the saphenous nerve can be in the way and there can be branches there. So I think that covers the bony anatomy, the muscles and tendons, as well as the neurovascular structures in the foot and ankle that are important as an introduction. And so I think we'll go to, we can go to a dissection
MATTHEW CONTI: now and we can look at what the ankle looks like from an anterior approach to the ankle. Thank you. [VIDEO ENDS]