Hand Anatomy - The Carpal Tunnel - Dr Gill

[Music] foreign you've joined myself Dr James Gill for another clinical skills video today we're going to be doing a deep dive into the carpal tunnel examination and actually what goes on when somebody has carpal tunnel syndrome so in order to grasp what we've done in our carpal tunnel syndrome demonstration which you should be able to see our previous video over there um we need to have a look at the anatomy so the carpal tunnel is a passageway in the wrist that allows connection between the forearm and the hand and it's called the carpal tunnel because it's comprised on the base of the carpal bones and across the top of it we've got something called the flexor retinaculum a thick fiber sheath that essentially stops everything inside from bowing out when the hand moves and it's called the carpal tunnel because the carpal bones say make them the largest proportion of this tunnel the flexor retinaculum over the top connects at four Anchorage sites to the carpal bones so when it comes to the carpal tunnel we have the carpal bones forming the base across the top is the flexor retinaculum and that's held on in four positions we've got the scaphoid PC form the hook of the hamate and the trapezium at the base of the thumb these form the anchors for the flexor retinaculum over the top and I've kind of worked that one backwards thinking that the flexor retinaculum is a trapezium shaped bit of tissue and that just helps me anchor where my first Anchor Point is and then move on around from there um once we've grasped where the carpool tunnel is we need to understand why it's important so if we have a look at the flexor retinaculum here covering over the carpal tunnel it gives us an idea of the contents so we have eight tendons from the flexor digitorum superficialis and flexor digitorum profundus they're involved in flexing the fingers at the metacarpal Foundry or joint and also flexing at the interfangial joints the other um ligament that we have running through there is a ligament to flexus pulses longus and The crucial bit within the carpal tunnel is the median nerve the median nerve will supply sensation to the lateral uh three and a half fingers we say lateral because when we're standing in the anatomical position obviously our index will be on the upside so we've got the lateral three and a half fingers and the thumb it's going to provide Innovation to the thinner Eminence and that's really really crucial to explaining why patients have difficulties picking things up doing buttons and generally how carpal tunnel will have a huge impact on a patient's activities of daily living so let's have a look at those muscles now so with the carpal tunnel we're obviously going to pay a lot of attention to the thinner muscles and it makes sense if we know what they're called so in terms of these we've got a little acronym FAO so we're going to bring all issues with the with the median nerve with the carpal tunnel for attention of the thinner Eminence so those muscles very simply are the flexor pulsis brevis the abduct of policies brevis the abductor and then underneath that we've got the opponent's policies if we have a flexor pulsis brevis makes sense that we have an extensive pulse brevis however that is not contained within the carpal tunnel so it's not something we need to be concerned about today with regard to the carpal tunnel as we said you can see the muscles of the thinner Eminence and the median nerve is going to provide Innovation there hence if it's been squashed by arthritis or osteophytes or inflammation or just general irritation for example working at a desk and repetitive strain injury the median nerve compression will lead over time to wasting at the thinner Eminence having a big impact on a patient's ability to move their thumb at the end of the day we have to remember that our opposable thumbs are the things that allowed us to be the humans we are so it's all very well and good understanding the names of the muscles but to help us with that we need to appreciate the movements of the thumb so with the thumb in the same plane as the rest of the fingers we can abduct the thumb and we can adduct the thumb we can Flex the thumb and we can extend the thumb we can also bring it round in opposition and those muscles are going to do as they say so it makes a lot more sense for you when you realize that the thumb is also called the polysis so flexor pollicis brevis will Flex the thumb over abduct or pulses brevis well abduct the thumb a b duction going away we'll also have opponent policies now that will oppose the policies oppose the thumb but it does need to work in concert with flex or policies brevis to bring the thumb around and over as opposed to flexors pulses brevis just bringing the thumb down hopefully you can see there why a problem here at the carpal tunnel has a such significant impact on your ability to move and do things with the hand it can often be a bit of a challenge for students to grasp the sensory distribution from the median nerve however if we look at the anatomy it becomes very clear so we have the median nerve coming out of the carpal tunnel and it splits off to the thumb the index the middle and we can literally follow it up here half of the ring finger whereas the other half of the ring finger is effect it is innervated by the ulnar nerve and is very much not part of the carpal tunnel is not affected by the flexor retinaculum there so with that in mind literally just seeing what it is that we're talking about often makes life an awful lot easier and if you can keep the anatomy in mind then you should be able to easily understand how the sensation changes when we have compression at the carpal tunnel here hence when patients have paresthesia pins and needles numbness or pain we're going to get the thumb the index the middle and half of the ring finger affected there is an off-branching of the nerve that comes out just before the flexor retinaculum so it is possible that we can retain sensation at the base of the thumb and we do have carpal tunnel syndrome well I hope that's been a good overview of carpal tunnel for you please consider subscribing and liking the channel because it tells the YouTube algorithm we're here and that might help other people to see this video please drop a comment Down Below on any other areas you'd like us to look at focusing on I think one of the things that seems to be coming through loud and clear is the temporal mandibular joint issues so we're going to be trying to have a look at that in the next couple of weeks with that in mind take care we'll see in the next one cheerio [Music]