Hello everyone,nice to meet you all again.i hope you all have had read my previous posts.as we are in process of learning about major nerves.previously we have learnt about musculo cutaneous nerve and axillary nerve and its clinical aspects.now we are going to learn about largest nerve of brachial plexus is RADIAL NERVE.
it is a branch of posterior cord of brachial plexus and its root value is C5,C6,C7,C8,T1.
It supplies posterior compartment muscles(extensors of arm) i.e., TRICEPS MUSCLE
and extensors of forearm i.e., EXTENSOR MUSCLES OF FOREARM.
The radial nerve originates from posterior cord of brachial plexus and enter into axilla.
In axilla
It supplies - long head of triceps and medial head of triceps.
Then it enters into spiral groove of humerus bone which is located in posterior side.when it is passing through spiral groove it supplies two muscles.
In spiral groove
It supplies - Lateral head of triceps and medial head of triceps
Then the nerve gives two branches before it gets divided in the arm itself on lateral side.
Lateral side of arm
It supplies - Brachioradialis and extensor carpi radialis longus
Then it pass through on the lateral epicondyle and then in forearm it gives two branches - superficial branch and deep branch - Posterior interosseous nerve
Superficial branch supplies skin of dorsum of hand of lateral 3 and half fingers except nail beds which are supplied by median nerve.
Posterior interosseous nerve pass through supinator muscle and it goes posteriorly and supplies extensor muscles of forearm.
This is the course and supply of radial and i made a digital schematic diagram for this for easy understanding.
We have to take the schematic diagram again to understand this
You can observe that now i marked "×" with red color on the course of nerve denoting site of injury.so there are four major sites of injury of radial nerve.
It is divided into higher lesions and lower lesions.sites 1 and 2 are higher lesions and 3 and 4 are lower lesions.
Higher lesions
Site 1 - in the axilla
The lesion in this site called crutch palsy.
Signs - flexed elbow,wrist drop,finger drop and sensory loss of the dorsum of hand.
In the above image the 1st one who is using clutches causes crutch palsy due to injury to the radial nerve in axilla and the 2nd one who is sitting in chair after drinking alcohol at weekend causes saturday night palsy due to injury to radial nerve in spiral groove.
Site 2 - in spiral groove
The lesion in this called saturday night palsy.
Signs - weakness of extension at elbow,wrist drop,finger drop,sensory loss
"Wrist drop"
Image source
Lower lesions
Site 3- at lateral epicondyle
Signs - finger drop and sensory loss.no wrist drop because ECRL muscle is spared.
Site 4 - injury to posterior interosseous nerve
Signs - no wrist drop,now sensory loss(sensory branch is spared),finger drop is present.
Hope you all understand radial nerve and next post i will come with remaining two nerves.
Thanks for reading,
