Radial Nerve

From: www.wheelessoneline.com

– See:
– Posterior Interosseous Nerve Syndrome :
– Radial Nerve Palsy Associated w/ Humeral Shaft Frx:
– Radial Nerve Block
– Tendon Transfers for Radial Nerve Palsy:

– Anatomy:
– three posterior divsions of brachial plexus form posterior cord: (C5 , C6 , C7, C8, T1)
– radial nerve (C5, C6, C7 , C8 , and T1 ) is largest of & most frequently injured branch of both the posterior cord (as well as the brachial plexus);
– in axilla, it gives off:
– posterior cutaneous nerve of arm;
– branch to long & medial heads of triceps;
– between axilla & spiral groove of humerus:
– it distributes a branch to the lateral head of the triceps;
– nerve may or may not travel in spiral groove and is often separated by the humerus by 1 to 5 cm of muscle;
– course of nerve through the intermuscular septum;
– nerve travels from deep to the lateral head of the triceps, piercing the intermuscular septum;
– after piercing lateral intermuscular septum, the nerve comes to lie between the brachialis and brachioradialis, and goes on to pass in front of elbow:
– radial nerve emanates from the spiral groove approximately 10 cm proximal to the lateral epicondyle;
– branch to brachioradialis & ECRL ;
– nerve remains anterior relative to the humerus, and passes along the lateral column of the distal humerus;
– reference: One-third, two-thirds: relationship of the radial nerve to the lateral intermuscular septum in the arm.
– each of motor branches, arising from radial nerve & passing to lateral head of triceps, is accompanied closely by a branch of profunda brachi artery and vein;
– as noted by Gerwin et al (JBJS Am. 1996 Nov;78(11):1690-5.), the nerve crosses the posterior aspect of the humerus at 20-21 cm proximal to the medial epicondyle and 14-15 cm proximal to the lateral epicondyle;
– posterior interosseous nerve :
– it divides in front of radial head, w/ deep branch (PIN) passing backward thru supinator (arcade of Froshe) to supply 9 muscles on extensor aspect of forearm;
– because of the numerous branches into which the deep radial nerve breaks up at the lower border of the supinator, surgical repair of the nerve here is difficult;
– remaining part PIN, runs downward parallel to posterior interosseous artery to supply all of deeper lying extensor muscles & ends as a twig to wrist joint;
– in this course, it passes superficial to long abductor & EPB of thumb, but its terminal branch to wrist joint passes deep to EPL & EIP;

– Sensory Branch:
– superficial branch of radial nerve passes into forearm deep to brachioradialis muscle;
– approx 8 cm from tip of radial styloid, nerve emerges from under tendon of BR between tendon of BR & tendon of ECRL;
– sensory branch passes downward emerging dorsally from beneath BR tendon about 5 cm proximal to radial styloid;
– it lies just deep to the superficial veins; – distally, it provides sensation to dorsum of thumb, excluding subungual region which is supplied by branches of median;
– superficial branch innervates dorsal aspect of first web space & hand as far ulnarward as middle of ring finger & as far distally as proximal interphalangeal joint.
– references:
The radial sensory nerve . An anatomic study.
The superficial branch of the radial nerve: an anatomic study with surgical implications.
Transfer of sensory branches of radial nerve in hand surgery.

– Physcial Exam:
– signs of a radial nerve lesion include:
– inability to exten thumb, proximal phalanges, wrist or elbow;
– hand is pronated and the thumb adducted.
– termainal branches of superficial radial nerve are palpable in the anatomic snuff box where they cross EPL;
– paralysis of PIN will result in total loss of extension of fingers &, though rare occurrence, must be entertained in diff dx of extensor tendon rupture (w/ the R.A. pt):
– exam for brachial plexus injury:
– brachioradialis (C5-6)
– supinator (C5-C6)
– ECRB (C6-C7)
– triceps (C6-8)

– Radial Tunnel Compression Syndrome:
– compression of the radial nerve at the elbow can involve the PIN or the superficial branch;
– radial tunnel syndrome refers to the syndrome of forearm pain without muscular weakness;
– it is often misdiagnosed as resistant tennis elbow or PIN syndrome;
– unlike tennis elbow, there is tenderness about 4 cm distal to the lateral humeral epicondyle;
– sites of compression:
– fibrous bands anterior to the radial head at the entrance of radial tunnel;
– radial recurrent vessels;
– tendinous origin of ECRB
– tendinous proximal border of supinator (arcade of Frohse)
– this is the most common location of nerve compression in radial tunnel syndrome;
– distal edge of the supinator at exit;
– exam:
– look for tenderness over the radial tunnel;
– pain may be experienced when the long finger is extended against resistance;
– active supination from a pronated position (tightening supinator) along w/ wrist flexion (which tighens the ECRB) may reproduce the patient’s symptoms;
– also consider differential injection of the deep radial nerve;

– treatment:
– as noted by Jebson and Engber et al 1997, about 2/3 patients with radial tunnel syndrome had good to excellent results, however, complete pain relief and return to normal activities is not always predictable;
– treatment includes division of the fibrous edge of the supinator muscle (most common reason for impingement), and division of the medial border of the ECRB;
– reference:
– Radial nerve entrapment at the elbow: surgical anatomy.
– Radial tunnel syndrome caused by ganglion cyst: Treatment by arthroscopic cyst decompression

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Lateral Femoral Cutaneous Nerve

From: www.wheelessonline.com 

– Anatomy:    

– LFCN, as its name suggests, is purely sensory;    
– it arises from L2 and L3, travels downward lateral to the psoas muscle, crosses the iliacus muscle (deep to fascia), passes either thru or underneath the lateral aspect of the inguinal ligament, and finally travels onto innervate the lateral thigh;
– it divides into anterior and posterior branches and supplies skin on lateral aspect of thigh;
– in the study by Hospodar et al (JTO 1999), the course of the nerve was variable, but was most commonly found at 10-15 mm from the ASIS and as far medially as 46 mm from the ASIS;
– in no specimen did the nerve pass lateral to the ASIS (eventhough historically the nerve is thought to pass lateral to the ASIS in 10% of population);
– in all specimens the nerve passed underneath the ilioginal ligament and anterior to the iliacus muscle; 

– Meralgia Paresthetica: 

– entrapment syndrome of the lateral femoral cutaneous nerve causing burning, numbness, and paresthesias down the proximal-lateral aspect of the thigh;
– may be idiopathic, be a result of trauma, previous operations, and in some cases may arise from Perthes Disease abduction splints;
– in idiopathic cases, the nerve may be encased in bone by the growing apophysis of the anterior superior iliac spine, or may be entrapped in fascia either proximal or distal to the ASIS;    
– diagnosis is made by:           
– reproduction of the pain by deep palpation just below the anterior superior iliac spine and by hip extension;           
– relief of pain by localized injection of lidocaine;    
– treatment: when diagnosis is not in doubt and the symptoms are severe, consider operative decompression at the site of constriction;

EMG and NCS

Electromyography (EMG) and nerve conduction studies (NCS) are tests that measure the electrical activity of muscles and nerves. Nerves send out electrical signals to make your muscles react in certain ways. Nerves also send signals from your skin to your brain, which then processes the signals, so you can experience a variety of skin sensations.

  • An EMG Test looks at the electrical signals your muscles make when they are at rest and when they are being used.
  • A Nerve Conduction Study measures how fast and how well the body’s electrical signals travel along your nerves. EMG and nerve conduction studies are used to help diagnose a variety of muscle and nerve disorders and to quantify the severity of your condition.


An EMG test helps find out if muscles are responding the right way to nerve signals. Nerve conduction studies help diagnose nerve damage or disease. When EMG tests and nerve conduction studies are done together, they help doctors tell if your symptoms are caused by a muscle disorder or a nerve problem. With EMG and NCS studies, your doctor can next select the best therapeutic option to help you.