So I'm going to jump in and give a few minutes of kind of background as to nerve transfers and why we're here. You can see my relevant disclosures up on the screen. Probably nobody would be here if they weren't familiar with the concept of nerve transfers. It's the sacrificing of a less desirable donor nerve to reinnervate a more desirable recipient nerve. This concept is very similar to tendon transfers, so we're all familiar with at least tendon transfers. And like tendon transfers, you really want to look for a donor nerve that is redundant, or you just really don't care about losing that particular function. Like tendon transfers also, in some situations, in extreme situations, you still have to make a hard decision, and you may have to sacrifice a function that you'd rather not sacrifice, but in the scheme of things is probably the best for the patient. When nerve transfers work, they do tend to be more natural in function than tendon transfers, and we'll talk about in a few minutes some differences in the rehab. So nerve transfers are not a new concept. They've actually been around for many decades. So historically, they were really used in situations where you didn't have a proximal stump. You can see it's a picture of nerve root avulsions. There's nothing to fix if I don't sacrifice another nerve in a situation like that. Scenarios such as a C5, C6 avulsion, spinal accessory suprascapular nerve, medial pectoral intercostals, to musculocutaneous nerve, these transfers really have been around for a long time. What is new is taking this concept and using it in situations where conventional repair is possible. So the emphasis is shifting towards how do we more effectively restore function as opposed to how do we restore anatomy. And the reason for that is obvious to everybody here. The results from major peripheral nerve injuries, especially more proximal ones, are terrible. I'm not going to go through all the numbers up on the screen, but you could scan them and see they're all low. The results of conventional repair for these types of injuries really are not very good. And related to a lot of factors, certainly included in that is long regeneration lengths, which equals long regeneration time. And what happens with long regeneration time? You get denervation atrophy of the muscle. The contractile proteins change. It becomes fibrotic. It loses the ability to ever regain contractibility. This idea has actually been around for a while, though it really seems to be getting more traction lately. The idea that nerves also suffer from denervation. I'll call it atrophy. But changes, time-associated changes with a distal nerve stump. With time, the Schwann cells become less supportive. There's loss of axon guidance signals. And even the endoneural tubes seem to fill up with proteoglycans and get clogged. You throw in there a big gap size, and now you've got to do a graft. And the problem with grafts is that they don't support regeneration like native nerves do. You get axon misdirection, particularly with larger gaps. And as well as the two suture lines, you're going to lose axons at each suture line. You may have to put the graft in a less favorable zone of injury. And then just looking at the data, grafts longer than 10 centimeters, we know that the chance of those working really decrease. What do we gain if we're going to do nerve transfers? We actually can potentially address a lot of these situations. We can shorten the regeneration length quite a bit. We can make it so that there's a direct shot right in the muscles, so we control some of that axon misdirection. We could go from two suture lines to one suture line. We could specifically, potentially, just get motor axons if we're trying to restore just motor function, so you get better specificity. And we could even avoid bad zones of injury. So a lot of potential areas where we can correct all the problems that we see with conventional nerve repair in the correctly chosen nerve transfer. Christoph Oberlin is going to get the credit as doing, really, the shift in the paradigm when he described the transfer that was subsequently named after him, where some fascicles of the ulnar nerve were taken and transferred over to the motor branch of the biceps. We know that, compared to those terrible results that I showed you just a few minutes ago, we can go to 90% M4 recovery is what he reported after that transfer. Garg did a meta-analysis and also showed a mid-80% success rate with nerve transfer versus around 55% with conventional repair for restoring elbow flexion. So if the slides were working at all, I'd be showing you a picture of a Oberlin transfer and showing you, really, how beautiful it is, how close we're getting the repair to the muscle to see whether or not the direct shot, you cut down regeneration length significantly. And it's one of the reasons why it works so well. If you want to take a different transfer to compare, we'd say contralateral C7, where I'm not, in no way am I saying that that's a transfer that should never be done, but the results compared to the Oberlin are much, much, much inferior, that you get poor muscle recovery, maybe some protective sensation. And if we try to look at and understand why it is that that happens, it's because we've not gained any of the advantages I just talked about that you see with the Oberlin transfer, right? You're doing it to long transfer. You have to go from one side of the neck to the other side of the neck. It's a mixed motor nerve. You have a complete loss of synergies so that the person, if they say you take the contralateral C7 and transfer it to the musculocutaneous, for the person to then bend their elbow, they may have to straighten out their donor side. So that's good for parvo tricks, but not very good to be used in daily function. So again, all the things that make the Oberlin so good are some of the reasons why this other transfer, and I'm not saying you can't ever do it, but some of the things that make that other transfer not quite so good. So like any type of surgery, there's going to be risks and benefits to taking the approach of doing nerve transfers. Some are going to be better than others. The better ones are going to be the more intuitive ones, the ones that have a proven track record, the ones that are more straightforward. Hopefully, you don't have to burn bridges when you do the transfer. Though often, you need to be prepared that you have burned bridges by choosing nerve transfer versus tendon transfer. And because of that, nerve transfer is not always the right choice. You have to kind of look at how good of a nerve transfer it is compared to your other repair options. Certainly, conventional repair has, in many situations, is still the right choice. And interestingly, there's a study out there, and this makes a lot of sense to me, that you can do your nerve transfers and do a conventional repair. And what happens is the other muscles that you would have ignored get some reinnervation, and those results have actually been shown to be better. But certainly, there are situations where nerve transfer can be done or transfer with tendon transfers, tendon transfer alone. Just remember, it's one tool. It's not the only tool, and you need to use it in the context of your situation.

nerve transfers

reinnervating

tendon transfers

peripheral nerve injuries

Oberlin transfer