radial nerve injury, wrist drop, anatomy of the radial nerve. 

Anatomy of the radial nerve, radial nerve injury , wrist drop
Educational video describes the course of the radial nerve and areas of its injury.
The posterior cord of the brachial plexus gives the Axillary and Radial nerves.
Radial nerve compression or injury may occur at any point along the course of the nerve, such as:
- Axilla: Very high radial nerve palsy.
- Upper arm to elbow: High radial nerve palsy.
- Below elbow: low radial nerve palsies.
- Wrist: Wartenberg’s syndrome.
1- Very high radial nerve palsy(axilla): all motor and sensory function below the axilla will be affected with injury at this level, with injury to the radial nerve at the axilla, there will be loss of function to the triceps and weak elbow extension, the patient will experience wrist drop due to loss of function associated with the extensor carpi radialis longus and extensor carpi radialis brevis muscles., there will also be a loss of finger extension, put the wrist in extension and ask the patient to extend the fingers, sensory loss will also be seen in the distribution of the superficial branch of the radial nerve.
Causes of compression or injury to the radial nerve at the axilla:
1. Saturday night palsy: alcohol could be a factor as the person falls a sleep with the back of their arm is compressed by a chair back, bar edge, etc.
2. Honeymoon palsy: from another individual sleeping on one’s arm overnight, compressing the nerve.
3. Crutch palsy: compression on the nerve from walking with crutches.
2- High radial nerve palsy (upper arm to elbow): compression or fracture causing injury to the radial nerve within the spiral groove, fracture of the distal third of the humerus, all motor and sensory function will be affected below the level of this injury.
The radial nerve is vulnerable usually due to a fracture of the humerus at the spiral groove. Injury may also occur below the spiral groove when there is a fracture in the distal third of the humeral shaft.
Holstein-Lewis Fracture: injury to the nerve at this level will cause wrist drop as well as weakness of finger extension; sensory loss will also be seen in the distribution of the superficial branch of the radial nerve.
3- Low radial nerve palsy (below elbow):
1. Entrapment of the posterior interosseous nerve at the “Arcade od Frohse”: the arcade of frohse is a site of radial nerve entrapment which may cause paralysis of the posterior interosseous nerve, with this injury; patient will experience difficulty with extension of the fingers only.
2. Fracture dislocations around the elbow: motor function below this area will be affected; the posterior interosseous nerve is purely motor and no sensory loss.
Montiga Fracture, which is a fracture of the proximal third of the ulna/ radius with dislocation of the radial head:
- Compression of the radial nerve is secondary to fracture.
- Neurovascular examination is important.
- Nerve injury, especially involving the posterior interosseous nerve, is not uncommon (observe).
- The patient will have loss of finger extension.
Wartenberg’s syndrome:
- Compression of the superficial branch of the radial nerve.
- The pain is located 8cm proximal to the radila styloid.
- Wearing a wrist watch may irritate the area.
- Pain and paresthesia on the dorsum of the hand.
- Positive Tinel’s sign.al animated video describes locations of injury involving the radial nerve.
special thanks for NATHAN ELKINS FOR HIS CONTRIBUTION TO THIS VIDEO