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Structure, definition, muscles, boundaries and contents of the adductor canal.
Hey everyone! It's Nicole from Kenhub, and welcome to our tutorial on the adductor canal. As we work our way through this tutorial, we’re going to be covering a few things. Firstly, what is the adductor canal? We should definitely get this question straight before we begin. So, once we settle that, we’ll review some muscles of the anterior and medial thigh compartment, specifically, the muscles that contribute in some way to the adductor canal. Then, we’ll look at the boundaries of the adductor canal, and finally, we’ll see what’s actually in the canal itself.
So, let’s begin with our first question, what is the adductor canal?
The adductor canal, which is also called the subsartorial canal or Hunter’s canal, is an intermuscular passageway for nerves and vessels to travel through the thigh. It courses mostly lengthwise, superior to inferior, but it also runs a bit diagonally, too. The nerves and vessels that travel through the adductor canal are involved in supplying a small portion of the thigh, but the vessels especially are mostly trying to get to and from the leg – and we’ll have a few more details on this a little bit later.
Let’s now have a brief review of some of the muscles in the anterior and medial thigh – the muscles that contribute to the adductor canal, of course – and beginning with the anterior thigh, the muscles from this compartment that we’ll have a look at are the sartorius and the vastus medialis. For more details on the rest of the anterior thigh compartment, be sure to check out that video, and remember that these muscle are innervated by branches of the femoral nerve and, generally, as a group they extend the leg at the knee joint.
So, the first muscle we’re going to be looking at is this muscle highlighted in green, which is the sartorius. And in this image, we’re looking at the right thigh from an anterior view. Superiorly over here is the hip bone and, inferiorly, we have the knee joint. The sartorius muscle is the longest muscle in the body and has quite a distinct trajectory. It originates superiorly and laterally on the anterior superior iliac spine and travels along the thigh inferomedially to insert on the medial aspect of the tibia, which is a similar path to what we said the adductor canal takes. So, don’t forget to keep that in mind.
The other muscle in the anterior compartment relevant to the adductor canal is the vastus medialis, which we can now see highlighted in green. In this image, the sartorius has been removed, so we can see a little bit more of the vastus medialis. And this muscle is one of the four parts of the quadriceps femoris muscle group and is the most medial muscle of the anterior compartment.
Next, we’re going to be identifying relevant muscles of the medial thigh compartment – and these are the pectineus, the adductor longus, and the adductor magnus. For more details on the rest of the medial thigh compartment, be sure to check out that video, too.
So over here, we have the pectineus highlighted in green, and in this image, most of the anterior thigh compartment muscles have been removed. So, we can see the femur quite well, and we’ve also exposed the medial thigh compartment muscles as well. The pectineus muscle is a relatively small muscle of the thigh that is actually part of both the anterior and medial compartments.
The muscle we can now see highlighted in green in this image is the adductor longus, and this muscle as its name suggests, adducts the thigh at the hip joint, and this muscle is the most anterior muscle of the medial thigh compartment, so it’s in close contact with the vastus medialis.
And finally, the last muscle to familiarize ourselves with in this tutorial is the adductor magnus muscle, which is now highlighted in the image on the screen. And this is a large adductor of the thigh as evidenced by its name, magnus which in Latin means “grand”. The adductor magnus is part of both the medial and posterior compartments of the thigh, so it has the characteristics of both. And medially, it is an adductor of the thigh while posteriorly, it acts as a hamstring muscle.
So, what we can see in this image is that once we reached the inferior border of the adductor longus which is here, the adductor magnus becomes the most anterior muscle of the medial thigh in this portion of the thigh. At this inferior end of the adductor magnus, there’s a space or hiatus within the muscle called the adductor hiatus. And this hiatus is between the more medial fleshy insertion of the adductor portion of the muscle and the more lateral tendinous insertion of the hamstring portion of the muscle.
Okay, so, now that we’ve identified all the relevant muscles of the anterior and medial compartments of the thigh, we should be able to put them together and discover the boundaries of the adductor canal itself. So in the next few slides, we’re going to be looking at the proximal end, the distal end, and the walls of the adductor canal.
So, the adductor canal begins at this point here, and this is also the apex of the femoral triangle, and the femoral triangle is this area over here where the femoral artery, the femoral vein, and the femoral nerve can be found. So, two of the boundaries of the femoral triangle are muscles that we’ve identified already in this video, and this over here is the proximal end of the sartorius, medially we have the adductor longus, and superiorly, we have a structure called the inguinal ligament. And to remember these borders, you can use the mnemonics SAIL – S standing for sartorius, A standing for adductor longus, and IL standing for the inguinal ligament. And the apex of this triangle which we’ve identified already is the proximal end of the adductor canal.
So in terms of how the adductor canal ends, the adductor canal ends inferiorly and medially when it meets the adductor hiatus. And remember that the adductor hiatus is a space in the adductor magnus muscle between the fleshy adductor insertion and its tendinous hamstring insertion – so between the apex of the femoral triangle and the adductor hiatus. There’s one more question we want to ask which is, what muscles make up this intramuscular passageway?
In this image, the sartorius muscle has been removed so we can actually see the length of the adductor canal, and again here is the apex of the femoral triangle and over here is the adductor hiatus. So, this is the adductor canal. Let’s talk a little bit about the walls of the adductor canal, and there are three walls of the adductor canal and we can see two of them in this image. The posterior wall is made up of two muscles, and along the proximal part of the adductor canal, the adductor longus makes up the posterior wall. As we travel distally and the adductor longus ends, the adductor magnus is the posterior wall. The anterolateral wall is made up of one muscle, and that is this muscle over here, the vastus medialis.
The remaining wall is the medial wall or the roof of the adductor canal, and this is formed by the sartorius muscle, which we can see as it’s placed back into anatomical position in this image. Since the canal runs deep to this muscle, it is sometimes referred to as the subsartorial canal.
This image is a cross-sectional image of the thighs, and remember when looking at a cross-sectional image, you have to imagine that you’re looking up at the structure from the patient’s feet. So, over here is the posterior aspect and over here is the anterior side. So that makes this the right thigh, and over here, we have the left thigh.
So this whitish structure, sort of in the center of the thigh, is the femur, and anteriorly, we have the anterior compartment muscles; over here, we have the posterior compartment muscles, and finally over here, we have the medial compartment muscles of the thigh. The muscles highlighted on this image are the vastus medialis muscles on each thigh, and remember that they make up the anterolateral wall of the adductor canal.
Now what we can see highlighted is the posterior wall of the adductor canal, and this is in the proximal portion of the thigh, so this muscle is the adductor longus muscle. And finally, the muscle that’s highlighted is the sartorius muscle, and this makes up the medial wall or the roof of the adductor canal. And, of course, the reason we’re looking at these walls is to find the adductor canal itself which is here, running between those three muscles.
So, now that we know what the adductor canal is and where it is, let’s have a look at what travels within it. And over the next few slides, we’re going to be taking a look at the femoral artery, the femoral vein, and the femoral nerve.
So, the femoral artery travels the entire length of the adductor canal, and do you remember when we saw it in the femoral triangle? When it reaches the apex of the femoral triangle, and therefore, the beginning of the adductor canal, it begins to travel more medially and distally through the adductor canal itself.
In this image, the femoral artery is again highlighted in green, but now we can see its whole path through the side. And the vastus medialis and the other anterior compartment muscles have been removed, so what we can see is the posterior wall of the adductor canal made by the adductor longus proximally and the adductor magnus distally.
Over here, we have the adductor hiatus – which means this is the end of the adductor canal – and the femoral artery passes through the adductor hiatus to the posterior aspect of the lower limb and becomes the popliteal artery within the popliteal fossa.
So, following the same path as the femoral artery is the structure we now see highlighted in green which is the femoral vein. And in this image, the vastus medialis has been removed, and we can see the whole course of the femoral vein. It arises as it passes through the adductor hiatus from the popliteal vein travels through the adductor canal and into the femoral triangle.
The final two structures that travel within the adductor canal are branches of the femoral nerve. And as you can see in this image, the entire femoral nerve is highlighted in green, and we can see in the femoral triangle that the femoral nerve splits quite a lot as it gives off branches to innervate the anterior thigh muscles, and the branches of the femoral nerve that have to travel a greater distance to get to their final destinations travel through the adductor canal.
The first branch is the one we can see highlighted in green just now, and this is the nerve to the vastus medialis. It travels along the vastus medialis within the adductor canal and gives off small branches to innervate that muscle along its length.
The second branch of the femoral nerve that travels through the adductor canal is the saphenous nerve – and we can now see that nerve highlighted in green. The saphenous nerve is a cutaneous sensory nerve that innervates the skin on the medial side of the leg, the ankle and the foot, and once it passes through the adductor canal, it reaches the medial side of the lower limb and it travels superficially to reach the skin.
So, that covers it for the anatomy of the adductor canal. We’ll now have a look at the clinical correlates of these anatomical sites.
So for various surgeries of the lower limb, it’s sometimes necessary to block the femoral nerve. Traditionally, the nerve block is performed in the femoral triangle which would result in the paralysis of the entire anterior compartment of the thigh; however, it isn’t always necessary to do so for the respective surgery, and in that case, an adductor canal block is performed. And by blocking the femoral nerve within the adductor canal, most of the motor nerves are left alone. And don’t forget that when we get into the adductor canal, the only motor nerve traveling through it is the nerve to the vastus medialis, and by blocking the femoral nerve within the adductor canal, the quadriceps femoris muscles are much less affected and patients can begin moving sooner after surgery.
And now, you’re an expert on the adductor canal. Before I let you go, let’s have a quick review of what we looked at today.
To begin, we looked at the muscles of the anterior and medial thigh compartments that contribute to the adductor canal; and in the anterior compartment, we looked at the sartorius and the vastus medialis muscles. In the medial compartment, we identified the pectineus, the adductor longus, and the adductor magnus muscles. Next, we looked at the boundaries of the adductor canal including where it begins proximally at the apex of the femoral triangle and where it ends distally – at the adductor hiatus.
The walls of the adductor canal are formed by some of the muscles we previously identified. So, the posterior wall is made up of the adductor longus proximally and of the adductor magnus distally, the anterolateral wall is made of the vastus medialis muscle, and finally, the medial wall or the roof is made of the sartorius.
And the final important piece of the adductor canal was identifying what structures travel through it. And there are four structures in all – the femoral artery, the femoral vein, the nerve to the vastus medialis, and the saphenous nerve – both of which are branches of the femoral nerve.
And to wrap up, we chatted about performing an adductor nerve block to reduce paralysis of the quadriceps femoris when needing to block the femoral nerve.
So that brings us to the end of our tutorial on the adductor canal. I hope you enjoyed it and thank you for joining me.