Ulnar Nerve Transposition (Cadaver)

CHAPTER 1

My name is Asif Ilyas. I'm a professor of orthopedic surgery and the program director of hand surgery at the Rothman Institute in Philadelphia at the Thomas Jefferson University. Today, we'll be talking about ulnar nerve transposition. Now ulnar nerve transposition is used to manage symptomatic cubital tunnel syndrome - also known as ulnar neuropathy of the elbow. That's when the ulnar nerve is under compression as it traverses the cubital tunnel behind the medial epicondyle at the level of the elbow. There's two broad ways to manage cubital tunnel syndrome. One is with a cubi- an in situ cubital tunnel release, and the other is with an ulnar nerve transposition. In this surgical video, we'll be looking at ulnar nerve transposition. A transposition can be performed in a few ways, including subcutaneous, intramuscular, and submuscular. I'll be demonstrating both the subcutaneous as well as the submuscular technique. As we go through the procedure, I'll show you some tips and tricks and hazards to avoid. We'll also discuss postoperative management and rehab.

CHAPTER 2

Okay, so now we're going be addressing ulnar neuropathy of the elbow, also known as cubital tunnel syndrome. You'll notice the arm is flexed slightly, externally rotated. I'm looking at the posteromedial - posteromedial aspect of the elbow. The ulnar nerve is going to be right behind the medial epicondyle, and it is palpable in the specimen here. Now to manage, surgically, ulnar neuropathy of the elbow, you have two ways you can approach this; you can do what is called an in situ cubital tunnel release or an ulnar nerve transposition with neurolysis. Either way, the incision is placed in this aspect of the elbow, behind the medial epicondyle. So I'm going to mark out both incisions to kind of share - to discuss how we go about this. So if you're doing an ulnar nerve transposition, you bring the elbow straight. You'll feel the epicondyle here. The tendency is to bring the incision anterior to the epicondyle, but recognize that you'll be away from your - your nerve and also increase the odds of injury inadvertently to the branches of the medial antebrachial cutaneous nerve. So with the elbow extended, I find it helpful to make a relatively straight incision. Behind the elbow, which is the path of the ulnar nerve. If I'm doing an ulnar transposition, centered on the medial epicondyle, my incision will go anywhere from 6 to 8 cm distally - and similarly, about 6 to 10 cm, proximally. If I'm doing a cubital tunnel release, I can use the same incision. However, I can also make a smaller incision - what I refer to as the mini open technique. And I'll use the same location on my incision, but I'll flex up the arm a little bit more to get a sense of where it is. And I place the incision directly behind the medial epicondyle like so. If I'm taking the transposition, I'll go the full length.

CHAPTER 3

We do a long, longitudinal incision as marked out. Again, notice how the incision is fairly posterior, intentionally, to allow for easier exposure of the nerve as well as to decrease the odds of injuring or having to expose branches of the medial antebrachial cutaneous nerve.

CHAPTER 4

And we'll start proximal. Tissue is easier to manage and more viab- and, safer. Cauterize vessels as you go in. I do this procedure under - with the patient asleep - and with a sterile tourniquet. The nerve is readily found proximal to the medial epicondyle, like so.

CHAPTER 5

It's mobilized and released. What you're releasing is the arcade that envelops it proximally. There's vessels that travel with the nerve, and you try to maintain as many of them as - as you can. I'm never grabbing the nerve; I just push the nerve. That's what I'm doing right now. Then I'll switch to using either a Penrose drain or an equivalent drain to help kind of control the nerve. So here's my nerve. I'm going to expose distally next. Okay, I'll try to use some retractors if possible. Let's see how they do. So much bigger exposure than a cubital tunnel release. Again, this is a cadaver, so I'm cutting through some of these structures. But, you want to absolutely make sure they're not a nerve or a vessel. If they're a nerve, and you - you cut it by accident, you want to cauterize it, so as to not cause any painful neuromas. And if it's a vessel, you similarly want to cauterize it. So the nerve is fairly well mobilized, proximally. So I'm going to take that nerve release, distally, and you'll see it start to get tethered within the medial epicondyle. We want to mobilize that. The first branch we'll come across is the articular branch to the joint. And that you can readily cauterize. And the first, most important branch you'll get to are the motor branches to FCU. So we're traversing the cubital tunnel right here. There's adventitial tissue that holds it together. And here you'll see the fascia between the two heads of FCU covering the nerve. So I will release that fascia in line with the nerve, like so. But I want you to appreciate that there is also a deep investing fascia as well that can also put some compression on the nerve, and you just spread through it. So, once mobilized, kind of gently pull away. As we do this, those first branches will become evident. Right here is probably the first motor branch of FCU - right there. Now the question often comes up, what do you do with them? Well if you can maintain them, that's the optimal thing to do. If you can't, then it's reasonable to take the first or second branch and cauterize it. The ulnar nerve innervates the FCU the entire length of the arm, so if you take a branch or two, it will not result in any meaningful, denervation of the muscle - but avoid them if you can. Now you can see how loose the nerve is altogether.

CHAPTER 6

So we want to transpose this anteriorly. So let's look at this now. So now that the nerve is released, we can transpose this in one of two ways; we can transpose this in a subcutaneous or a submuscular fashion, and I will demonstrate both.

Either way, irrespective of which transposition you elect to do, the main structure you need to confirm is decompressed - or removed rather - is the intermuscular septum. The intermuscular septum is often considered a constricting element to the ulnar nerve, but frankly it's more of a constricting structure to the ulnar nerve post-decompression. And I'll show you what I mean by that. So, here we go. So here is the intermuscular septum right here, and I'll expose it a little better for you so you can see it. It's this structure, right here, it comes off of the epicondyle, and it's quite palpable. And post-transposition, it can readily cause compression on the nerve, like so. So, it should be removed. So you can do this sharply, or you can do it with cautery. There are some bleeders back there, so cautery is a reasonable way to do this, but we'll use a knife here. You take it right off of the medial epicondyle. Again, there's a lot of bleeding structures back here. So, I tend to cauterize very generously in this region. Again, with a cadaver limb, we don't have that sense of the bleeding that can occur. Once I'm exposed enough, I just excise a centimeter segment of that intermuscular septum. So now, what you'll notice, epicondyle's here, and there's a bare, supracondylar ridge, like so. So then when the nerve is transposed, it sits over that ridge without any kind of external structures bothering it.

So let's transpose this and see how it looks. So if we transpose this anteriorly in a subcutaneous fashion, we see we're being tethered by this first branch of the ulnar nerve. So we have to make a decision if we want to keep that or not. Like I mentioned, there are many branches of the ulnar nerve to the FCU. So I'll often cauterize that first base. So here I'll just cut it. I'll cauterize it, and that really helps to mobilize this nerve even further. Once you transpose this anteriorly, the nerve's actually in more tension and extension than in flexion, which is the opposite of normal. So you can see how it drapes over top. It can be under some tension. This patient's very thin, so you notice there's very little tension on the nerve. But you'll also notice when I flex how the nerve crimps up and has absolutely not tension on it. And most of us spend most of our time with some amount of elbow flexion. So you'll notice how there's no tension on the nerve once it's in this position. Now how do we stabilize this? Well there's a few ways to stabilize this nerve, and I'll show you the subcutaneous technique first, and then the submuscular technique with a z-plasty.

CHAPTER 7

So when doing a subcutaneous transposition, the nerve moved anteriorly, the intermuscular septum taken down, I recommend two things to stabilize the nerve anteriorly. The first thing is to actually close the cubital tunnel so that you prevent any inadvertent re-subluxation of the nerve back behind the epicondyle, because if it does, it will be trapped there. So what you do is you take your posterior tissues, mostly some triceps extension right here, and you just - you come across your epicondyle, and you just close that interval. So typically, two sutures are more than sufficient. I use two figure-of-eights to close the interval down. And again, this is so that the nerve does not inadvertently re-sublux into the cubital tunnel. So that's the first thing. So once that's done, the second thing you want to do to stabilize the nerve, anteriorly, is you want to place some kind of fascial sling to hold it in place. So once the cubital tunnel has been closed with some of the fascia of the triceps, you need a fascial sling to hold the nerve anteriorly. So I just take a little bit of the posterior aspect of the fascia of FCU and come across like so. Leave it attached to its origin on the epicondyle and then tease it back. And then this then is subsequently repaired. Repaired to here. Looking for a second pickup - here we go. So using a 2-0 Vicryl or equivalent, repair like so. And what that does with this repaired, it prevents the nerve from translating posterior - it acts as a - a post or a bolster to prevent it from slipping back, as such.

CHAPTER 8

Alternatively, a submuscular transposition can be done. And I will actually translate the nerve posteriorly, temporarily. And to do this with a z-plasty, the orientation you want to have is basically like so. Okay? So we also already did some of it, like so. And then we come across. It's a little short, but that's okay. And we come across like this to complete the rest of it. Now how deep you take this is what defines whether this is an intramuscular or a submuscular. Obviously, this requires significant dissection and splitting of the FCU muscle belly. This is not my preferred way to do transposition, but it is a very effective way to do it. And I'll use this technique in revision cases or cases where I need to bury the nerve a bit - maybe a complaint of neuritis or what have you, a thin patient - and that way it allows me to make the nerve less palpable. And then these two ends - I'll show you the orientation again. They start like this, and then once we're done, it's like this. So let's move that nerve into this space here. Actually, I'm going to release some of this fascia here first. I have to stay close the epicondyle as the medial - median nerve is not far from here. So I don't want to wander too far away. I'm just staying on the supracondylar ridge. The nerve then just moves over to here, anteriorly. We have this branch here. This leaflet here and this leaflet here is then repaired end-to-end, like so. One or two figure-of-eight sutures will do the trick. You have to be mindful not to cause a new site of constriction of the nerve. I'll just do one for the sake of demonstration, but obviously, you can do more as needed. Like so. Once done, you'll now have a submuscular - or intramuscular - transposition of the ulnar nerve. And let's take a look at that. So here's our bridge. It's been lengthened with a z-plasty. The nerve is below. You want to make sure you absolutely have plenty of room for the nerve. You want to check your nerve deep. Make sure it's satisfied and not tight. Here you'll find a little bit of residual tension of that deep investing fascia that I had mentioned. I'll release that a little bit further. So here's that deep investing fascia. The nerve is deep to me. There's that fascial layer. I'll just release that a little bit further. Once released, you'll notice the nerve is very loose. I can easily pull it in either direction with no tension on it. Like so.

CHAPTER 9

I then again take the nerve through an active range of motion to confirm that there is no tension on it. Again, no tension.

CHAPTER 10

At this point, I typically drop the tourniquet as there's typically quite a lot of bleeding because of all of the cutting of the FCU - I'm sorry, the flexor pronator mass musculature. So I'll cauterize that until satisfied. I do no more additional deep closure. I just close the skin with 3-0 Vicryl or an equivalent, and a running 4-0 Monocryl, and then a glue for the skin, or a nylon for the skin.