Elbow Neural Entrapments & Injuries

radial nerve splits into

posterior interosseous nerve (motor) & superficial radial branch (sensation)

a posterior IO nerve problem will show

weakness

a superficial branch of radial nerve will show

pain/loss of sensation

median nerve branches into anterior interosseus nerve to innervate

deep flexors (FPL; OK symbol)

Neural “Entrapment” is neural compression leading to inflammation phase (2-3 wks). Prolonged compression or tension can result in

sensitization of neural structures

Distributions in axoplasmic flow

Distributions in blood supply

Neural “Entrapment” Difficult to diagnose, What is commonly used but usually only shows late signs of issue?

EMG studies (a (-) does not imply lack of neural problem)

Highly specific, Low sensitivity

Thorough clinical examination is essential

The consequences of prolonged neural compression starts w/ inflammation, then vascular changes, then nutritional disruption, then altered flow. What is seen to be lost first?

sensation, motor is lost last

intermittent ischemic nerve problem that does not typically lead to long term damage. This focal demyelination or ischemia is

Neuropraxia

Long term damage to connective tissue in nerve:

Epineurium

Perineurium

Endoneurium

Axonotmesis

neurodynamic testing is better than EMG for determining

neural injury (not specific)

what is complete transection of nerve?

neurotmesis (complete loss of sensation & motor)

Axonotmesis may present with

loss of sensation, maybe some motor weakness

Wallerian Degeneration is retrograde degeneration of axon after nerve injury; 90% of axons damaged at site of injury, when does regeneration process begin?

1st 7 days after injury new axonal sprout growth will begin

Ulnar Nerve (C8-T1) innervates

Motor: FCU, FDP, Instrinics of hand

Sensation: Medial side of hand

Entrapment sites for the ulnar nerve

Arcade of Struthers

Cubital Tunnel (#1)

Flexor Carpi Ulnaris

ulnar nerve entrapment sensory changes are common (affects medial 1½ fingers); motor sxs include

Weakness/atrophy of FCU or medial ½ of FDP

Intrinsic of hand; palmar interosseous

Maybe weakness/atrophy of hypothenar eminence

Cubital Tunnel (Funny Bone) has ulnar nerve pass posterior to medial epicondyle. Taut at

90° of flexion

On slack w/ full extension

Cubital Tunnel Ulnar Nerve Entrapment causes include prolonged flexion of elbow, trauma to medial elbow, repeated trauma as in leaning on elbow, Inflammation of nerve; as well as a

cubitus valgus deformity (pitchers, Oly lifters), ↑ carrying angle

s/p misaligned healed fx may create tension along nerve

Recurrent dislocations of nerve out of cubital tunnel may be reason for neuritis

Entrapment may also occur between 2 heads of FCU (roof of cubital tunnel) (flexion & ulnar deviation can be MOI)

Cubital Tunnel Syndrome presentation sxs includes pain at the

medial elbow, Numbness & tingling into medial forearm + 4th & 5th digits

Muscle weakness in FCU or Instrinics

Muscle wasting or Claw deformity in severe cases

Cubital Tunnel Syndrome diagnostic tests

Elbow Flexion Test (3-5 mins, may not take that long)

Pressure on cubital tunnel

Tinel’s sign (hypersensitivity)

Neurodynamic test for ulnar nerve

Nerve conduction velocity tests

The Arcade of Struthers for ulnar nerve entrapment consists of a fibrous tunnel that is 8cm above the

medial epicondyle. Ulnar Nerve penetrates medial intermuscular septum

Palpation of region should reproduce sxs→ distally

if a pt has pain above medial epicondyle rule out what before going to arcade of struthers?

c-spine, TOS, cubital tunnel

Ulnar Nerve Interventions include Rest & avoid

repeated or excessive elbow flexion, trauma to area (resting elbow on desk, sleeping w/ elbow flexed)

Modalities for inflammation or desensitization: cortisone injections

ulnar nerve transposition surgery used as last resort (move ulnar nerve closer to median nerve). Moves nerve where?

anterior to medial epicondyle & stabilize it in CT (“anterior transposition”)

Excision of medial epicondyle

Divide tendinous insertion of flexor carpi ulnaris (arcuate lig.)

Median Nerve (C5-T1) innervates

Motor:

Anterior forearm

Thenar muscles

Lumbricals of lateral hand

Sensation: Palm & anterior 1,2,3rd & half of 4th digits

Common Entrapment Sites for median nerve

Ligament of struthers

Lacertus Fibrosus

Pronator Teres Syndrome

Flexor digitorum Superficialis

Ligament of Struthers is only present in 1% of population (Genetic). Testing will show all median nerve issues, includes sxs reproduced w/

resisted elbow flexion at 110-120°

Palpation of region

Lacertus Fibrosus is a fascial continuation of Biceps Tendon (bicipital aponeurosis), allows for bicep to be strong supinator. It is also an entrapment site for median nerve which can be compressed as it runs under its medial edge. What will test this site of entrapment?

Holding forearm in full pronation. have them supinate & adding elbow flexion

Pronator Syndrome (2nd most common entrapment) is compression of median nerve proximal to where the

AIN branch is given off between 2 heads of pronator teres

Pronator Syndrome presentation shows ↑ sxs w/ pronation. Motor involvement includes FCR, Palmaris longus, FDS. What are the 3 muscles affected by AIN syndrome?

FPL, FDP, PQ (OK sign)

Sensory: Lateral 3 1/2 fingers (median nerve)

(+) pinch grip & weak wrist flexion, finger flexion, sensory changes

Pronator Syndrome sxs can be elicited by

passive or active pronation

Pronator Syndrome testing

Resisted pronation while arm is in full supination

+Palpation of the pronator

Anterior Interosseous Nerve (AIN) entrapment will spare

lumbricals, superficial group of flexors

Anterior Interosseous Nerve (AIN) arises from median nerve at lower border of cubital fossa at Pronator Teres Muscle. It traverses distally along interosseous membrane between

FPL & FDP to reach pronator quadratus muscle. Ends by supplying sensory fibers to wrist

AIN Entrapment can occur between the

2 heads of pronator teres

Unclear etiology

AIN Entrapment presentation muscle involvement

FPL: Lateral ½ of FDP, Index & middle finger

Pronator quadratus

Pinch deformity evident: (+) pinch grip test: can’t flex DIP, Difficulty picking things up

No cutaneous sensory function at wrist

FDS entrapment of median nerve is concomitant w/ Pronator syndrome. resisted FDS performed w/

fingers in extension

Radial Nerve (C5-T1) innervates

Motor:

Posterior compartment of arm & forearm

Sensation:

Posterior arm, Dorsal Forearm, Dorsal of hand

radial nerve entrapment sites

Fibrous bands at radial head

Leash of Henry

The ECRB

Arcade of Frohse

Supinator

Radial Nerve (Tunnel) Syndrome sx presentation includes Diffuse lateral elbow pain, esp w/

gripping

Aching at night

Dorsal wrist pain

5 cm distal to lateral epicondyle: Irritation of this nerve may be concomitant w/ LE

Superficial Radial Nerve

PIO: motor weakness

OA or fibrous bands anterior to radiocapitellar jt or synovitis of radiocapitellar can impact what potential radial nerve compression site that may lead to RTS?

the lateral elbow jt in radial head

if a pt has a spiral groove fracture what muscles innervated are affected?

triceps & brachioradialis, ECRB (radial deviation & elbow extension affected)

Posterior Interosseous Nerve is a branch of radial nerve in forearm can become entrapped between

the 2 heads of the supinator

Posterior Interosseous Nerve MOI is result of trauma to the area

Presentation:

Motor: Extensor muscles of wrist

No sensory: but may have local pain

C6 radiculopathy, lateral epicondylalgia, radial tunnel could all be differential diagnosis for

lateral elbow pain

Acute Forearm Compartment Syndrome can be from

Supracondylar fx

Distal radial fx or direct trauma

IV line malfunction

Infections, Insect bites

Forearm Compartment Syndrome presents w/ the 5 ps

Pain

Pallor

Passive stretch pain

Paranesthesia

Pulselessness

An arcade of anastomosing branches of recurrent radial artery at radial neck can impact what potential radial nerve compression site that may lead to (sensory) RTS?

the Leash of Henry

The leading/medial proximal edge of ECRB can impact what potential radial nerve compression site that may lead to (sensory) RTS?

fibrous edge of ECRB

The proximal edge of superficial layer of supinator muscle can impact what potential radial nerve compression site that may lead to (not sensory) RTS?

the Arcade of Frohse

The distal edge of supinator muscle can impact what potential radial nerve compression site that may lead to (not sensory) RTS?

distal edge of radial tunnel