#22 How to Inject the Carpal Tunnel - Tutorial1st February 2012
What is the Carpal Tunnel Syndrome and how to inject the Carpal Tunnel to release tension in the tendons of the hand tutorial presented by Mr. Adrian Richards of Aurora clinics. If you are a medical practitioner and you would like more information on our Minor surgery training courses, please call us on 0800 328 5743
Hello, my name’s Adrian Richards. I’m a plastic and cosmetic surgeon and the Surgical Director of Aurora Clinics. This is one of a part of a series of videos I’m going to be doing on common hand pathology, particularly instructing you on how to do injections to cure the common problems you get in the hand or the trigger finger, carpal tunnel syndrome, and De Quervain’s tenosynovitis.
The first one I’m going to be doing today is carpal tunnel syndrome. Now, I couldn’t, unfortunately, find anyone in the office who was happy to have their hand treated. So I’ve got a rubber hand here, and I’m going to be showing you on the rubber hand how to inject the carpal tunnel.
First of all, let’s just look at some anatomy on the wrist. This tendon here, which is on the base of the thumb on the thumb side of the wrist is called the flexor carpi radialis. That’s the FCR tendon. This tendon on the ulnar side of the wrist is called the flexor carpi ulnaris. It’s here. That’s the tendon you when you grip you can really feel it tense up here. That’s the FCU.
In the middle here is the palmaris longus. Not everyone has a palmaris longus. About 20% of people do not have this tendon. The way you test for this tendon is you ask people to grab between their thumb and little finger and bend their wrist. Can you see here, can you see my palmaris longus is sticking out? I don’t know if you can see that. That’s my flexor carpi radialis, ulnaris over there, and then when I do that can you see that tendon sticking out? That is the palmaris longus. As I said, 80% of people have that.
Moving on, flexor carpi radialis here. Flexor carpi ulnaris on the other side. Palmaris longus, which you may or may not have. Now the median nerve comes between the flexor carpi radialis, palmaris longus, moves in there. Moves up into the hand. As we know, the median nerve supplies the thumb, index, middle, and half of the ring finger, the thumb half of the ring finger. It supplies sensation to there, and it also supplies the nerve supply, the muscle supply to the thenar eminence, which is this bit of muscle here, which apparently, if you are a cannibal, this apparently is the tenderest muscle to eat in the human body. I’m not suggesting you do that, but that apparently is the case.
The median nerve comes up here. It gives a motor branch here which supplies this muscle. It supplies the sensation here. If it’s squashed, it’s squashed in the carpal tunnel. The carpal tunnel lies between here and here. Basically, the carpal bones are arched, and then all the tendons and nerves that go to the fingers go through this tunnel. To keep them all down, you’ve got a layer over the carpal tunnel, and that’s called the flexor retinaculum. That keeps everything down nicely. The flexor retinaculum lies in this position here.
The nerve, which is going to all these fingers here, the median nerve is squashed here. As it passes through the wrist to here, it’s squashed. That’s what gives you carpal tunnel syndrome, which is characterised by tingling in the hand, particularly at night. Relieved by shaking. Also, if it’s squashed for a long time, you can get a weakness in the muscle here. This muscle can flatten out. What you need to look for is a flattening out in this area, a depression in that area, rather than a big, round, full thenar eminence, a bit of a depression here.
Where are you going to inject to relieve carpal tunnel syndrome? We’re going to inject a small amount of steroids. I would normally inject 1 mL of lidocaine, plain lidocaine, and 1 mL of 10 mg per mL of triamcinolone. You can either inject that way or you can inject that way. My preference is to inject that way because if the patient pulls their arm away suddenly, they’re going to pull it that way, and you’re not going to go into the nerve. If the steroid gets under the fascia in this layer, it’s going to spread down to the carpal tunnel. I’ll be showing you how to do that injection in a second.
The first stage is to mark where you want to inject. I’m going to inject between the flexor carpi radialis and the palmaris longus. So really just that. Next stage, clean the skin with an alcohol swab. Okay, so everything’s sterile. Then you want to do this with a no-touch technique, because you don’t want to get any potential bugs in the carpal tunnel.
I like to just give a little bleb of local anaesthetic first into the skin because it’s a little bit tender during the procedure. I would just go through the skin with my lidocaine and just a little bleb where you’re going to inject. That is going to reduce the pain when you actually have the injection because there will be no sensation through the skin.
I always like to do it with the orange needle, because I think the smaller needle you can do that with the better. Less painful, less trauma for the patient. I’ve got two mLs in there, one mL of the local anaesthetic lidocaine, one mL of triamcinolone 10 mg per mL. Doesn’t really matter what steroid you use. Just use whatever is familiar to you.
Bevel of the needle up. Numbers on the syringe towards you. Gloves on, sterile skin. All ready to go. Just pop through here. If you just pop through, you go through the skin and then you feel the next layer is under the fascia of the forearm. If you get any pain going up the fingers or any twitching in the fingers, it’s likely you’ve hit the nerve, so pull out. As you pop through, you should just pop through, and this fluid should go in really, really easily. If there’s any resistance, you’re in the wrong level. Basically, it’s a tunnel with things going through it. It’s a potential space. The fluid should go in really easily.
Now it won’t go in very easily, because this isn’t a real hand. Basically, you pop in, make sure there’s no twitching, no pain. If you get twitching and pain, you’re in too far. So don’t do that. Then inject the fluid nice and gently. It should go in really, really easily, although it won’t in this hand because it’s a false hand.
Then reject out, pressure on there, elevate the hand for the patient. Always, with any hand procedures, elevate the hand. There will be less bruising and swelling there. Wait a couple of minutes, talk to the patient. Ask them to move their fingers to disperse the local anaesthetic up and down the carpal tunnel. That’s it, really.
You’ll probably get relief pretty much immediately because of the local anaesthetic. That’s only going to last an hour, and then for the next couple of days, they won’t notice too much because the steroids take a little bit of time to work. But the next few days they should notice a decrease in the swelling of the synovium around the tendons. Basically, the steroids reduce the inflammation, reduce the swelling around the tendons, and then, by reducing that swelling, they make more room in the tunnel so they relieve the pressure on the carpal tunnel.
I really recommend that you do carpal tunnel injections three times. No more than that. If it comes back after three times, you need to consider surgery.