Posterior Interosseous Nerve Syndrome
Roberta Kern
Richard A. Okragly
BasicsDescription
-
Compression/entrapment of the posterior interosseous nerve under the extensor carpi radialis longus that presents with variable weakness to loss of function of finger and thumb extensors
-
Initially pain and weakness may have been noted about the elbow and/or forearm.
Epidemiology
-
Dominant arm is involved twice as much as the nondominant arm
-
Predominant gender: Male > Female (2:1).
Risk Factors
-
Repetitive pronation and supination (usually strenuous activity)
-
Trauma
-
Monteggia fracture
-
Synovitis
-
Soft tissue masses:
-
Thickened arcade of Frohse
-
Lipoma
-
Neuroma/ganglia
-
Fibroma
-
-
Tight arm bands, eg, holding a rifle sling wrapped around the forearm for prolonged periods, as seen in military recruits
General Prevention
Avoidance of preventable risk factors
Etiology
-
The posterior interosseous nerve is a continuation of the motor branch of the deep radial nerve, tracking distally across the surface of the abductor pollicis longus and yielding branches to the extensor pollicis longus (EPL) and adductor pollicis longus (APL) and the extensor indicis.
-
Nerve roots, mainly C6, C7, and C8, with main contribution from C7
Commonly Associated Conditions
-
Direct trauma to the nerve, as with laceration
-
May be associated with synovitis of the radiocapitellar joint
-
Entrapment of the fibrous edge of the extensor carpi radialis brevis (ECRB)
-
Compression of the radial recurrent artery
DiagnosisHistory
-
Weakness or inability to extend the wrist and digits
-
Pain in the deep exterior muscle group distal to the radial head:
-
Can be dull or sharp pain
-
Not a primary complaint
-
May precede the weakness
-
-
No sensory deficits
Physical Exam
-
Sensation intact
-
Radial deviation of the hand on wrist extension owing to paralysis of the extensor carpi ulnaris muscle
-
Intact extensor carpi radialis longus and brevis, which are innervated distal to the posterior interosseous nerve
-
Unable to extend digits at the metacarpophalangeal joint
-
Tenderness on deep palpation along proximal radius
Diagnostic Tests & Interpretation
Imaging
-
Plain radiographs: Obtained to exclude fractures, dislocations, healing callus, arthrosis, or tumor as causes of the symptoms
-
MRI/CT scan/US:
-
To detect soft tissue masses (such as lipomas and ganglions) as well as aneurysms
-
Also to look for rheumatoid synovitis
-
-
Electromyelography (EMG)/nerve conduction studies (NCSs): See next section.
Diagnostic Procedures/Surgery
Electrodiagnostic testing: Typically need to wait 17 days to see electrophysiologic response to Wallerian degeneration of motor fibers.
-
Normal sensory nerve action potentials (SNAPs)
-
Drop in compound muscle action potential (CMAP) amplitude or conduction when stimulated between brachialis and brachioradialis muscles and recorded proximal to extensor indicus proprius
-
Needle examination reveals membrane instability (positive sharp waves) in muscles distal to supinator muscle.
-
Triceps, brachioradialis, and extensor carpi radialis longus and brevis are spared.
-
Supinator muscle may or may not be affected.
-
Serial exams can document recovery (every 3–6 mos).
P.485
Differential Diagnosis
-
Other radial nerve injuries, including:
-
Radial nerve palsy
-
Radial tunnel syndrome
-
Wartenberg syndrome
-
-
C7 radiculopathy
-
Lateral epicondylitis (tennis elbow)
-
Rupture or dislocation of any of the extensor tendons
Treatment-
Conservative management that includes:
-
Rest
-
Ice
-
Anti-inflammatory medications
-
Immobilization
-
-
Time frame for conservative treatment varies from 1–6 mos.
ED Treatment
Immobilize with a cock-up wrist splint.
Medication
First Line
NSAIDs [C]:
-
Use for 4–6 wks.
-
Help with pain relief
-
If no resolution of symptoms, then may proceed to steroid injection.
Second Line
Corticosteroid injection [C]:
-
Place injection ∼4 cm distal to lateral epicondyle.
-
Doses and types of corticosteroids vary but can include 1 mL of local anesthetic with 1 mL of corticosteroid.
Additional Treatment
Physical therapy that includes:
-
Range-of-motion exercises that increase strength, endurance, and postural awareness
-
Progressive strengthening and modified work simulated tasks
-
Application of heat and/or US
-
Massage
-
Duration of therapy varies from 1–6 mos.
-
Done in adjunction with treatment with medications
Referral
-
Refractory cases (3 mos without improvement)
-
Progressive symptoms despite treatment
Additional Therapies
-
If severe, a dynamic splint is needed to hold the fingers in extension.
-
Occupational therapy consult
Surgery/Other Procedures
Surgical decompression may be necessary in refractory cases.
Ongoing CareFollow-Up Recommendations
-
Will need close follow-up with a surgeon after surgery to prevent any postoperative complications (eg, flexion contracture at the elbow)
-
It is important to start physical therapy/rehabilitation ∼7–10 days postoperatively to prevent contractures and stiffness.
Additional Reading
Alba CD. Therapist's management of radial tunnel syndrome. In: Mackin E, Callahan A, Skirven T, et al. eds. Rehabilitation of the hand and upper extremity 5th ed. Philadelphia, PA: Mosby, 2002.
O'Connor FG, Ollivierre CO, Nirschl RP. Elbow and forearm injuries. In: Lillegard WA, Butcher JD, Rucker KS, eds. Handbook of sports medicine 2nd ed. Boston: Butterworth Heinemann, 1999:150–151.
Stern, Mark. Radial Nerve Entrapment. www.emedicine.com. September 2, 2009.
Wheeless III, Clifford R. Posterior Interosseous nerve compression syndrome. Wheeless Textbook of Orthopaedics. www.wheelessonline.com. Updated Janurary 3, 2010.
CodesICD9
354.3 Radial nerve lesion
Clinical Pearls
-
Function usually returns with conservative therapy in a few weeks.
-
Surgery is rarely necessary.