 Good day everybody, this is Dr. Sanjay Sanyal, Professor Department Chair. We are going to demonstrate the back of the leg, the bones, the muscles, the fascia, the neurovascular structures. So you're seeing the left back of the leg be in front of you. We will start right from here and it will go all the way the back of the leg and we will end the region of the ankle. First let's take the fascia. The cruel fascia is attached to the posterior intermuscular septum which is attached to the posterior margin of the fibula and it goes all the way around and gets attached to the medial border of the tibia. So that is the posterior aspect of the cruel fascia and this forms a tight osteoficial compartment bounded anteriorly by the fibula, the introsius membrane and the tibia itself, all the posterior aspect. So once we have the cruel fascia then we have a septum in the middle of the cruel fascia in the posterior compartment. That's called the transverse intermuscular septum. This stretches from the posterior intermuscular septum to the medial border of the tibia and that divides the posterior compartment into superficial and deep. There are several important clinical functional aspects of this cruel fascia. What is because of the tight osteoficial compartment? It acts as a calf pump. So when the muscles contract they squeeze the venous blood up because normally the venous blood is under extremely low pressure and they need assistance to go up to the heart. If this fails then we get deep vent thrombosis and because it's a tight osteoficial compartment any blunt trauma in this region can lead to swelling of the muscles and lead to compartment syndrome which can be limbs threatening and therefore such conditions we may have to do what is known as a fascia otomy. The muscles are attached in two layers but we shall describe them in three layers. So first let's take a look at these attachments which are already colored in front of us. Just to bring up to speed blue refers to insertion, red refers to origin. We see this line here this is the solial line. This gives attachment to the solius muscle. Solius muscle gets attached in an inverted U-fashion on the back of the tibia. Then between the tibia and the fibula there's a small fibrous bridge that is known as the tenderness arch of solius and then the solius gets attached a little bit on the fibula. So this is the U-shaped inverted attachment of the solius. Let's remove the solius then let's take a look at what else is attached deep. We see this line here this is the vertical line on the back of the tibia. This acts as a demarcation between muscles which are attached to the back of the tibia. Medially we have because this is the left side so this is the medial this is the left side. Medially we have attached the flexor digitalum longus then we have the tibialis posterior and attached to the back of the fibula and the introsius membrane we have the flexor halusis longus. So the way to remember it is D, T, H. D is flexor digitalum longus, T is tibialis posterior and H is flexor halusis longus. These three tendons then come down the tibialis posterior being the strongest muscle here it makes a groove on the back of the medial malleolus and just here it crosses under the flexor digitalum longus and in the region of this place this is called the torsal tunnel. The relationship changes from anterior to posterior we have T, D, H. Tibialis posterior, flexor digitalum longus, flexor halusis longus and this place is called the torsal tunnel because it is bridged over by the flexor necrolum of the ankle joint extending from the medial malleolus to the calcaneus and of course we have the neurovascular structures going through which I shall mention later. Now let's take a look at the next muscle which I have not mentioned yet which is the most superficial muscle of the group and that is the gastrocnemius. The gastrocnemius is a two joint muscle that means it crosses the knee joint it crosses the ankle joint. The gastrocnemius has got two bellies this is the attachment of the medial belly of the gastrocnemius it is a slightly larger than the lateral belly it's attached just above the medial cordial of the femur and this is the attachment of the lateral belly of the gastrocnemius and the two bellies then unite somewhere in the middle of the back of the calf and immediately become a thick tight aponeurosis which rapidly narrows down and merges with the tendon of the soleus which I mentioned earlier and becomes the tendocalcaneus which goes down and gets attached in this region of the calcaneus we can see in blue here so approximately half the length of the calf is occupied by the aponeurosis and the tendon of the tendocalcaneus earlier it was called tendo achilles between the soleus and the gastrocnemius we have yet one more very small muscle and we can see the origin of that here this is the origin of the plantaris it's a very small muscle it looks like a mouse the muscle is only this big it goes from lateral to medial between the gastrocnemius and the soleus and after that immediately it becomes a long thin shiny white silvery colored tendon and this tendon then runs and it also merges with the tendocalcaneus this muscle does not have much functional use therefore this tendon is used for tendon rafting this can snap during sports and that is known as tennis leg and this can be mistaken for the t-bell nerve by a junior person that's why it used to be called the fresh man's nerve the medial head the gastrocnemius as I said is slightly larger than the lateral head and the medial head the gastrocnemius can also rupture in the condition known as tennis leg medial head of the gastrocnemius can also entrap the popliteal artery here in the condition known as popliteal artery entrapment syndrome the popliteal artery entrapment syndrome is a complex syndrome comprising of six subdivisions one of them is by the abnormal origin and compression of the medial head of the gastrocnemius I mentioned something called the tendinous arch of soleus here where the soleal line bridges over in the form of a fibrous arch from the tibia to the fibula as the popliteal artery passes through the tendinous arch of soleus under the tendinous arch of soleus exactly at that point it divides into a posterior tibial and an anterior tibial the anterior tibial goes to the anterior compartment through an opening in the introsius membrane that's a smaller of the terminal divisions posterior tibial is the larger exactly at that point the popliteal artery can get entrapped so that is also another site of entrapment of the popliteal artery the tibial nerve is descending down vertically across the popliteal fossa and it runs on the posterior aspect in the deep compartment that is deep to the transverse intramuscular septum the two of them the posterior tibial artery and the tibial nerve they run in the deep compartment accompanying the posterior tibial artery we have the venae cometantes which is the calf pump which I mentioned earlier which is responsible for pushing blood up thrombosis of that can lead to deep vein thrombosis and pulmonary embolism with potentially life threatening consequences now let's take a look at a few fractures of the tibia and the fibula the tibia is weakest at the junction of the upper two thirds and the lower one third so therefore this is the common site of fracture the problem with tibial fractures is twofold number one this surface the meter surface of the tibia is subcutaneous so therefore tibial fractures quite often become compound that means they pierce through the skin other aspect of a tibial fracture is that it can also quite often be associated with fibular fractures people who wear calf length boots sometimes they can get a fracture above that limit of the boot and that is known as the boot top fracture this is an x-ray of the leg to show both bones fracture tibia and fibula this is called a boot top fracture sometimes we can have a flexible fracture of the tibia and a segment of tibia can undergo sequestration and loss in which case we may require to replace it with a vascularized bone graft from the fibula we take the vascularized bone graft from the opposite leg because the fibula has its own individual blood supply by means of the fibular artery which is a branch from the posterior tibial artery and the nutrient artery from the fibular artery is taken as the vascular pedicle and the segment of fibula from the opposite side is removed with the vascular pedicle and it is nastomost by means of micro vascular nastomosis and the lost segment of the tibia is replaced so that is the clinical significance of the fibula we can get fractures of the lateral malleolus which is the lower end of the fibula we can get fractures of the medial malleolus that is called the pot's fracture dislocation we shall talk more about these fractures when we come to the foot and the ankle joint this is an x-ray to show fracture the lateral the medial malleolus and dislocation of the ankle in the condition called pot's fracture dislocation fracture of the neck of the fibula is also not very uncommon this can happen from a springing action like i am doing now if i press here there is a springing force exerted onto the neck of the fibula just under the head and that can lead to fracture of the neck of the fibula and winding lateral to the neck of the fibula is the common fibular nerve the common fibular nerve is the smaller terminal division the post axial division of the sciatic nerve it runs like this under cover of the biceps femoris it goes behind the head of the fibula and then it winds around the neck of the fibula and goes to the anterior and lateral compartment as the deep and the superficial fibular nerve the common fibular nerve can get injured here that can lead to foot drop this is an x-ray to show fracture the head the neck of the fibula where common fibular nerve can be injured before i conclude though it is more in the relation to the ankle joint in the ankle we have already mentioned that relationship is tibialis posterior flexor digitrum longus flexor helosus longus now let's put the artery and the nerve in place we have a mnemonic for this we call it tom dick bloody nervous harry from anterior to posterior he stands for tibialis posterior d stands for flexor digitrum longus bloody stands for posterior tibial artery which passes under this and then it divides into medial and lateral planter arteries then nervous refers to the tibial nerve which also passes and then divides into medial and lateral planter nerves edge harry stands for flexor helusus longus so that is tom dick bloody nervous harry the tibial nerve can get entrapped under this flexor reticulum and that is known as tarsal tunnel syndrome in which there will be severe heel pain because the tibial nerve gives calcaneal branches and additionally there'll be weakness of the muscles of the sole of the foot but we should talk more about that when we come to the sole of the foot so these are some of the points which i wanted to mention to you about the muscles the neurovascular structures attachments fascia in the back of the leg especially with their clinical implications thank you very much for watching Dr. Sanjay Sanyal signing out please like and subscribe if you have any questions or comments please put them in the comment section below have a nice day