Interosseous Nerve Compression

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PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

Synonym: Kiloh-Nevin syndrome I (anterior interosseous nerve compression)

The anterior interosseous nerve is a branch of the median nerve. It arises from the median nerve just distal to the antecubital fossa, about 5.5 cm distal to the medial epicondyle of the humerus.[2] It passes along the interosseous membrane between the ulna and radius. It terminates in the pronator quadratus muscle around the level of the wrist. It is largely a motor nerve. It supplies the flexor pollicis longus, the lateral half of the flexor digitorum profundus (ie to the radial two digits) and the pronator quadratus.

Compression of either the anterior or posterior interosseous nerves is uncommon. Anterior interosseous nerve injuries account for only 1% of all nerve injuries affecting the upper limb.[3] 

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  • A deep head of pronator teres.
  • An enlarged bicipital tendon bursa may impinge on the nerve.
  • An aberrant or thrombosed radial artery branch in the mid-forearm.
  • A thrombosed ulnar artery.
  • Tendinous bands.
  • Aberrant accessory muscles in the deep palmar compartment - eg, Gantzer's muscle, the accessory head of the flexor pollicis longus.
  • Fractures and trauma.
  • One study reported a case of spontaneous anterior interosseous compression secondary to Churg-Strauss syndrome (small and medium vessel vasculitis).[4]
  • The main problem with this lesion is weakness and difficulty moving the index and middle fingers.
  • There may be pain in the proximal forearm.
  • There is weakness on flexion of the interphalangeal joint of the thumb due to weakness of the flexor pollicis longus.
  • There is weakness on flexion of the distal interphalangeal joints of the index and middle fingers due to weakness of the flexor digitorum profundus.
  • Normally, when someone pinches something between the index finger and thumb, the metacarpophalangeal and interphalangeal joints of the thumb and index finger are flexed and a circle is formed. With this nerve deficit, the terminal phalanges of the thumb and index finger are extended or hyperextended.[1]
  • There is no sensory loss.
  • Isolated neuropraxia of the branch to the flexor pollicis longus secondary to partial anterior interosseous nerve palsy has been reported.[5]
  • A lesion of the lateral cord of the brachial plexus.
  • Avulsion of the flexor digitorum profundus or of the index profundus tendons.
  • C8 radiculopathy (rare).
  • Physical examination is important in diagnosis.
  • X-ray may be helpful to exclude fracture, dislocation, healing callus or tumour.
  • MRI is sometimes used.[6]
  • The anterior interosseous nerve is deep, as are the muscles it supplies. Hence, neurophysiology and electromyogram (EMG) studies are difficult.[1] EMG, however, can be very useful in determining the severity of the condition and whether treatment should be conservative or surgical.[7]
  • Rest and immobilisation using splinting may help.
  • Non-steroidal anti-inflammatory drugs (NSAIDs) and steroid injections may have some value.
  • Nerve release and/or repair may be needed for anterior interosseous nerve lesions.[8] However, one study of young patients with spontaneous palsy did not use surgical decompression and showed that recovery occurred within 12 months with conservative management.[9]

This is a deep motor branch of the radial nerve. After emerging above the elbow between the brachioradialis and brachialis muscles, the radial nerve divides into the superficial radial nerve and the posterior interosseous nerve (PIN) at the level of the lateral epicondyle.[10] The PIN passes through the supinator muscle as is goes from the anterior to the posterior surface of the forearm.[11] It supplies the extensor carpi radialis brevis and supinator before entering the arcade of Frohse (a fibrotendinous structure below the supinator muscle, present in 30% of adults, that may develop secondary to repeated rotational movements of the forearm). The PIN supplies all of the extrinsic wrist extensors except for the extensor carpi radialis longus.[11]

The radial tunnel is commonly described as the area where the radial nerve exits between the brachioradialis and brachialis muscles to the area where it enters the arcade of Frohse.

There are two syndromes that can occur when the PIN is entrapped/compressed: radial tunnel syndrome and posterior interosseous syndrome.

Radial tunnel syndrome

  • Pain over the anterolateral proximal forearm, maximal four fingers' breadth distal to the lateral epicondyle.
  • Extension of the elbow and pronation of the forearm intensifies symptoms.
  • Resisted active supination and extension of the middle finger also causes pain.
  • There is not usually any motor weakness or sensory loss.

Posterior interosseous syndrome[12] 

  • Proximal forearm pain (not a primary symptom). Pain can be reproduced on resisted supination and sometimes on resisted pronation of the forearm. It can also be reproduced on wrist flexion and with resisted extension of the middle finger.
  • There may be tenderness over the lateral epicondyle and the arcade of Frohse.
  • There is no sensory deficit.
  • There is partial-to-complete motor paralysis of the wrist extensors BUT brachioradialis, extensor carpi radialis longus and extensor carpi radialis brevis and supinator muscles may be spared because they are innervated by more proximal branches. Any wrist extension that remains will have radial deviation.
  • The patient will be unable to extend the thumb or other digits at the metacarpophalangeal joints. Interphalangeal joint extension will be possible.

PIN palsy can occur secondary to both mechanical (including local tumour compression, trauma and iatrogenic injuries) as well as non-mechanical events.[13] 

Radial tunnel syndrome

  • May be a result of overuse.
  • May represent an early posterior interosseous syndrome.
  • Sites of compression may be:[14][15][16]
    • Fibrous bands attached to the radiocapitellar joint.
    • Radial recurrent vessels.
    • Tendinous origin of the extensor carpi radialis brevis.
    • Tendinous origin of supinator.
    • Fibrous thickenings within and at the distal margin of supinator.

Posterior interosseous syndrome[12]

  • Radiocapitellar joint synovitis.
  • Tumours (eg, lipomas, ganglions).
  • Congenital tightness of ligamentous arcade of Frohse.
  • Poorly placed screws for fracture fixation.
  • Monteggia fractures.
  • Idiopathic compression syndrome.
  • Radial recurrent vessels.
  • Iatrogenic injury - one study reported a case of posterior interosseous syndrome resulting from friction massage.[17]
  • C7 radiculopathy (will produce weakness of the triceps and wrist flexors, unlike a PIN lesion).
  • Lateral epicondylitis (will not show tenderness about 4 cm distal to the lateral humeral epicondyle).
  • Extensor tendon rupture.
  • Physical examination is important in diagnosis.
  • X-ray may be helpful to exclude fracture, dislocation, healing callus or tumour.
  • MRI is sometimes used.
  • Electrodiagnostic tests are normal in radial tunnel syndrome.
  • Nerve conduction studies and EMG studies are abnormal in posterior interosseous syndrome and can be helpful to identify the site of compression.
  • Injection of local anaesthetic four fingers' breadth distal to the lateral epicondyle will result in temporary PIN palsy and will result in temporary relief of pain if there is PIN compression syndrome.[12]
  • Conservative treatment is usually enough in radial tunnel syndrome but surgery may be needed if there is still pain at 12 weeks.[14][15][16]
  • Conservative treatment includes:
    • Rest and immobilisation using splinting.
    • NSAIDs and steroid injections.
    • Soft-tissue-based management, neural gliding and rehabilitation may be helpful, especially in cases not involving paralysis or denervation.[18]
  • The surgical treatment of radial tunnel syndrome is controversial. The success rate of decompression surgery in radial tunnel syndrome is between 10-95%. The combined treatment, releasing both the PIN and the superficial branch of the radial nerve, shows more consistent success rates compared with releasing the PIN alone. However, one study reported satisfactory results after decompression of the superficial branch of the radial nerve only.[19]
  • Surgery should be used in posterior interosseous syndrome after 12 weeks if there is no improvement with conservative treatment or if there is deterioration in symptoms/signs.
  • If nerve entrapment has only caused mild damage to the nerve, recovery will be quicker.
  • The outcome after surgery depends on the degree of damage to the nerve pre-operatively.
  • If affected muscles have atrophied/fibrosed before the patient seeks medical help, tendon transfers may be needed at the same time as nerve decompression for a satisfactory outcome.
  • Early operation tends to produce good recovery.

Further reading & references

  1. Anterior interosseous nerve; Wheeless' Textbook of Orthopaedics
  2. Tubbs RS, Custis JW, Salter EG, et al; Quantitation of and superficial surgical landmarks for the anterior interosseous nerve. J Neurosurg. 2006 May;104(5):787-91.
  3. Dunet B, Pallaro J, Boullet F, et al; Isolated anterior interosseous nerve deficit due to a false aneurysm of the humeral artery: an unusual complication of penetrating arm injury. Case report and literature review. Orthop Traumatol Surg Res. 2013 Dec;99(8):973-7. doi: 10.1016/j.otsr.2013.07.018. Epub 2013 Nov 6.
  4. Ochi K, Horiuchi Y, Tazaki K, et al; Spontaneous anterior interosseous nerve palsy with Churg-Strauss syndrome. Mod Rheumatol. 2010 Oct;20(5):514-7. Epub 2010 May 12.
  5. Haflah NH, Rashid AH, Sapuan J; Partial anterior interosseous nerve palsy: isolated neuropraxia of the branch to Hand Surg. 2010;15(3):221-3.
  6. Dunn AJ, Salonen DC, Anastakis DJ; MR imaging findings of anterior interosseous nerve lesions. Skeletal Radiol. 2007 Dec;36(12):1155-62. Epub 2007 Oct 16.
  7. Alexandre A, Alexandre AM, Zalaffi A; Considerations on the Treatment of Anterior Interosseous Nerve Syndrome. Acta Neurochir Suppl. 2011;108:247-250.
  8. Kim DH, Murovic JA, Kim YY, et al; Surgical treatment and outcomes in 15 patients with anterior interosseous nerve entrapments and injuries. J Neurosurg. 2006 May;104(5):757-65.
  9. Seki M, Nakamura H, Kono H; Neurolysis is not required for young patients with a spontaneous palsy of the anterior interosseous nerve: retrospective analysis of cases managed non-operatively. J Bone Joint Surg Br. 2006 Dec;88(12):1606-9.
  10. Tubbs RS, Salter EG, Wellons JC 3rd, et al; Superficial surgical landmarks for identifying the posterior interosseous nerve. J Neurosurg. 2006 May;104(5):796-9.
  11. Posterior interosseous nerve; Wheeless' Textbook of Orthopaedics
  12. Posterior Interosseous Nerve Compression Syndrome; Wheeless' Textbook of Orthopaedics
  13. Kohyama K, Sugiura H, Yamada K, et al; Posterior interosseous nerve palsy secondary to pigmented villonodular synovitis of the elbow: case report and review of literature. Orthop Traumatol Surg Res. 2013 Apr;99(2):247-51. doi: 10.1016/j.otsr.2012.11.015. Epub 2013 Mar 9.
  14. Henry M, Stutz C; A unified approach to radial tunnel syndrome and lateral tendinosis. Tech Hand Up Extrem Surg. 2006 Dec;10(4):200-5.
  15. Ferdinand BD, Rosenberg ZS, Schweitzer ME, et al; MR imaging features of radial tunnel syndrome: initial experience. Radiology. 2006 Jul;240(1):161-8.
  16. Stanley J; Radial tunnel syndrome: a surgeon's perspective. J Hand Ther. 2006 Apr-Jun;19(2):180-4.
  17. Wu YY, Hsu WC, Wang HC; Posterior interosseous nerve palsy as a complication of friction massage in Am J Phys Med Rehabil. 2010 Aug;89(8):668-71.
  18. Saratsiotis J, Myriokefalitakis E; Diagnosis and treatment of posterior interosseous nerve syndrome using soft J Bodyw Mov Ther. 2010 Oct;14(4):397-402. Epub 2009 Dec 16.
  19. Bolster MA, Bakker XR; Radial tunnel syndrome: emphasis on the superficial branch of the radial nerve. J Hand Surg Eur Vol. 2009 Jun;34(3):343-7. Epub 2009 Mar 12.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Michelle Wright
Current Version:
Peer Reviewer:
Dr John Cox
Document ID:
1229 (v23)
Last Checked:
24/02/2015
Next Review:
23/02/2020

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