By Jo Nova
It’s a fantastic piece of engineering
Henry Gray (1918) Anatomy of the Human Body
Last week my EPL tendon went snafu. For no reason, my left thumb just stopped doing what it always has. It didn’t hurt, but it didn’t work. It was rather disconcerting. I wondered if it was the first sign of some hideous degenerative nerve condition that would put me in a wheelchair. But after searching with the dreaded Dr Google, I figured out I’d just torn the EPL tendon. Who knew tendons can wear away painlessly and break? Who knew we can diagnose these things without an xray, just with an eyeball? So, I had surgery in hospital yesterday to fix it.
I looked at anatomy drawings and it dawned on me, we can see all the tendons on the back of our hands if we flex them the right way in the right light. And by golly, my right thumb had two tendons, but my left only had one. It was so obvious. Have a look at your own hand. We have two long tendons running down the back of your index finger and pickie* (though these look like one single tendon on our fingers, the two are obvious on our thumbs). Essentially, one tendon pulls on the top knuckle, and one pulls on the one below. These cords run down our hands through tunnels that keep them neat — like rolling over pulleys. They run right over our wrists and connect to muscles attached to the long bones of our forearm. Every time you wiggle your fingers, muscles are tugging from somewhere deep in your forearm, a long way from your hand.
Somehow as babies we all learn which muscle moves each knuckle to get full finger control. No wonder it takes months to learn fine motor skills…
Look at your tendons
The classic test for the torn long thumb tendon, apparently, is to place your hand on the desk and lift up your thumb. So this is me, trying to lift my left thumb. Nothing. No action. No cord under the skin. I’d never paid attention to the ridges that flowed before. But it’s so cool…
When the EPL Tendon is missing, the thumb can’t rise off the desk. | Click to enlarge.
Hardware, now gone.
Tendon breaks can occur with a long delay after a bone injury. I broke my arm two years ago iceskating. As the tendon stretched over the wrist, either the screws or bone scars abraded the tendon. Apparently they can’t be repaired easily after being shredded. Obviously, I needed to take out the metal hardware in my wrist too, lest it degrade the replacement.
On Monday I casually sent an email with my self-diagnosis to the surgeon who fixed my broken wrist two years ago. I must have been very convincing because 30 minutes later I got a phone call from his secretary saying I was booked in for surgery “Thursday”! That was a shock. Pandemonium hit my diary. So, yesterday I had the plate and screws removed, and a tendon graft and an overnight stay. The surgeon took one tendon from the index finger to restore control of the thumb. Apparently we don’t miss the extra extension on the finger as much as we do on the thumb — the ultimate prehensile tool — as I keep explaining to my cat. My arm is in a half cast. I’m typing slowly. I started this post a week ago.
And naturally after the secretary called, I sought second opinions. I was lucky enough, as a writer in the underworld of science, to get free advice from a GP, an orthopedic surgeon and an anesthetist. How rich am I?
For the next 3-6 weeks I’ll be typing less. Posts will be shorter. Sorry. I’ll do my best…
*Corrected. I thought we had two tendons on each finger, but it is not so — the middle two fingers only have one. For some reason we must need slightly more control with two tendons on the index and pinkie finger.