When a person receives a limb donation, how do surgeons “wire up” the nerves so that the recipient can use the limb and feel sensation from it?

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When a person receives a limb donation, how do surgeons “wire up” the nerves so that the recipient can use the limb and feel sensation from it?

In: Biology

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Anonymous 0 Comments

I had a sheet of glass fall on me at work last year, they wouldn’t intubate me for the repair surgery fearing they would need the machines for covid patients.
spent about 3 hrs watching two “micro plastic surgeons” (I think that was their titles) they literally cut my wound wider and used a metal clamp to hold the it open. then used a combination of methods to stitch and glue my nerves an tendons back together…. the craziest event out of it all was feeling my nerves “recalibrating”. I spent an entire night in bed unable to sleep, it felt like my hand was possessed an moving around wildly, yet I was watching it sit there perfectly still, wrapped tight in a fiberglass splint.
the sensations came and went for about a week and now about a year later I would say I’m pretty much recovered other then some numb spots on my palm.

Anonymous 0 Comments

I didn’t lose a limb but came very close to it. I ripped a slightly larger than an adult male’s fist, sized hole out of my forearm, exposing the bone and severing nerves and tendons to some of my fingers and my hand.

From what my dad told me, the surgeons cut my arm open wider and using microsurgery, stitched the nerves and tendons back together and I got a skin graft over the gaping hole in my arm, from my thigh.

The hardest part was lots of physio later, but they were so amazing and I was playing guitar and piano a little after a year. All the while realising how easily that it could have been my head (accident was on a mountain bike and impacting a Roughcast wall)

Anonymous 0 Comments

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Anonymous 0 Comments

I’ve known about this since a young age.

My dad when he was 16 worked in a factory. It had a shop saw that would automatically come down and make 3 cuts.

One unfortunate day the chop saw caught his shirt and sliced his arm in 3 right at the elbow. The saving grace was that it went right at the elbow and couldn’t slice through the elbow as easily as the rest of his arm.
He basically had to constrict it and call 911 himself as several of his coworkers fainted when they saw what happened, and that his arm was literally hanging by skin.

When this happened to him it was early 70s in Toronto 1972/1973. They had very very very very limited experience with this procedure(he was one of the first 3-5 people they had done it on, but never for pretty much an entire arm) and for the first year of his recovery they honestly didn’t know if they had connected all the nerves and tendons back properly and if it was “wired” correctly.

He was very fortunate and they did manage to do that so he infact got full use and mobility of his arm back after about 2 full years of recovery(it took 1 year for the tendons and everything to heal properly before he could fully start rehab).

He has 3 insanely gnarly scars in succession on his arm. One right above his elbow one directly on it and one directly below it.

one of the nerves is so exposed on the back of his elbow that if he would normally hit his funny bone as one does it literally buckles him over in pain. (There were a couple times as a young child(4-6) where I thought it was funny and would go for that nerve when we were play wrestling, I would hit that nerve and feel like the David defeating Goliath, but when I was 6 and did it I saw how much pain I caused my dad while he was just trying to have fun and play wrestle and never intentionally did it again).

Considering how insanely vulnerable that nerve is I’m both surprised and impressed with how few times I’ve seen him tap it. But I guess it’s like Achilles protecting his week spot, he knows it’ll take him down so he’s extra cogniscent of it.

Anonymous 0 Comments

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Anonymous 0 Comments

I cut my left thumb nearly clean off, and had it reattached by a plastic surgeon. Took two surgeries.

They hook the nerves together with sutures. They are expected to regenerate sensitivity at a rate of 1 mm per month.

With my thumb, there are still numb areas 43 years after the operation. It doesn’t always work 100% evidently.

Anonymous 0 Comments

I didn’t have a transplant but I cut my finger off and feel reattached it. Their are a dozen or so vein clamps and nerve clamps in there. They told me they basically pull the nerves and vein together and the clamp it with the clamps to hold it and either stitch it together or do something else. I can post a pic of my x-ray and you can see the hardware in there.

Anonymous 0 Comments

A subject I have personal experience with!

I broke my humerus playing roller derby a few years back and the fracture severed my radial nerve, meaning I lost the ability to lift my wrist and extend my fingers.

As other posters have noted your nerves are protected by a myelin sheath, which is basically a tube around the actual nerve. If you think about your cell phone charging cable the nerve is like the metal wire inside that carries the electrical current and the myelin sheath is like the materials covering and insulating it.

When a nerve is damaged the entire portion of the nerve from the point of damage to the termination (or “end”) dies as well. As long as the myelin sheath remains intact or heals properly the nerve will begin to regrow from the point of damage to the termination point.

So when performing a transplant or reconstructive surgery all the surgeons can do is connect these tubes and wait for the nerve to regenerate within.

Nerves grow very slowly, about 1 inch per month. The radial nerve which I severed in my accident invenerates the hand muscles at the top of your forearm. There was approximately six inches between this point and the damage site so it took about six months to fully regain control of my hand functions.

As far as I know this only applies to nerves branching off the spinal column. The spinal nerve itself will not regenerate or heal itself in most circumstances, which is why spinal injuries usually result in permanent disabilities.

But long story short, we can’t directly correct the nervous system through surgery or other intervention, we can only manipulate the tubes in which the nerves reside and wait for the nerves to repair themselves.

Anonymous 0 Comments

It slightly depends on the level (I.e. wrist/forearm etc).
Recently I reattached an amputated arm at mid-humerus level (about halfway through where the bicep is).
At this level there are a few named nerves that everyone has. The main three are the median, ulnar and radial nerves. So we find these and stitch them together using a microphone to try and line them up as well as we can. Then, as others have said, we hope the nerves grow down the sutured nerves.

If we’re lucky enough the nerves will grow across the join and down into the hand to give sensation and motor function

Anonymous 0 Comments

They don’t. Not directly. The correct nerve end on the recipient’s remaining limb is attached directly to the nerve fibres of the donor limb, but this doesn’t ‘rewire’ the nerve. Instead, the recipient’s nerves then use the donor nerve as a kind of scaffold, and will grow down the same path over many months, gradually connecting with muscles and skin as they go. This is an extension of what nerves do all the time.

For example, when you exercise and your muscles get stronger, one of the ways they do this is by increasing how strongly a muscle receives a signal from a nerve. This isn’t about sending a stronger signal – its the same signal, but our nerves grow in response to being used, and create more nerve endings, meaning the signal is repeated multiple times along the same muscle fibre. Nerves and muscles will shrink by default, but will grow if the brain keeps asking them to do things. In the case of a severed limb, the brain is still asking for information on that area but not getting it, and it’s still trying to send movement signals to that area, so the nerves will still try and grow. In the case of our fully developed nerves, for example the nerves on your hand right now, the brain is getting all the information it asks for, so there’s a balance between the brain saying ‘stretch out and tell me stuff’ and the nerves saying ‘relax and stretch less, so we use fewer resources’.

The challenge is that it takes time for nerves to regrow. They grow at a rate of around 2mm a day. For a hand transplant, this means it takes roughly 2 years for the nerves to reach all the different muscles and skin surfaces. In a larger transplant, it takes even longer. However, when muscles aren’t used, our body breaks them down and absorbs them – this is called atrophy. In the case of a full arm transplant, the muscles would fully atrophy long before the nerves reached them. This is the same issue with spinal cord injuries. The nerves can and do regrow naturally, but so slowly that muscle atrophy outpaces them.