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Anterior Interosseous Nerve Syndrome

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Other Names

  • Kiloh-Nevin Syndrome
  • AIN Compressive Neuropathy
  • AINS
  • Anterior Interosseus Nerve Syndrome




  • Represents <1% of upper extremity neuropathies[1]


  • General
    • Typically presents with forearm pain, weakness in the FPL, FDP of the index finger
    • Sensation is intact
    • Diagnosis is aided by EMG, MRI
    • Symptoms are typically self limited, surgery is indicated if symptoms don't resolve spontaneously


  • Pathoanatomy
    • Most common site of compression is the tendinous edge of the deep head of the Pronator Teres
    • Also must consider
      • Proximal edge of the Flexor Digitorum Superficialis arch (the FDS arcade)
      • Gantzer's muscle (accessory head of the FPL muscle)
      • FDS or FDP accessory muscles
      • Arterial thrombosis (radial or ulnar artery have been implicated)
      • Lacertus fibrous
  • Etiology of the disease is controversial[2]
    • Traumatic etiologies:[3]
      • Supracondylar fractures,
      • Penetrating injuries and stab wounds
      • Cast fixation
      • Venipuncture
      • Complication of open reduction and internal fixation of fractures
    • Spontaneous etiologies:
      • Brachial plexus neuritis
      • Compartment syndrome
      • Compression neuropathy
  • Martin-Gruber Anastomosis
    • Anatomical variant in which AINM gives off branches to ulnar nerve, patients can then present with symptoms in ulnar nerve patterns


Associated Conditions

Risk Factors

  • Needs to be updated

Differential Diagnosis

Differential Diagnosis Wrist Pain

Differential Diagnosis Forearm Pain

Other Considerations

Clinical Features

  • History
    • Poorly localized pain from forearm to anticubital fossa
    • The patient will not report any parasthesias
    • Inability to make "OK" sign
  • Physical Exam: Physical Exam Wrist
    • This disease is characterized by motor deficits only, there are no sensory deficits
    • Weakness of index and thumb pincer movement
  • Special Tests
    • Pinch Test: Patient unable to hold sheet of paper between thumb and index finger



  • Standard Radiographs Wrist
    • 3 View radiographs typically acquired to evaluate for other etiologies
    • No role in diagnosis of atraumatic disease


  • Sensory nerve conduction studies of median nerve should be normal
  • Can help differentiate neuralgic amyotrophy verse a compression neuropathy


  • Identifying compression of the AIN on MRI can be difficult[4]
    • Entrapment may not be visualized
    • Enhancement within the muscles affected by the nerve root entrapment


  • N/A



  • Most patients improve with 6-12 weeks of relative rest and conservative care
  • Relative rest, especially from provocative activities
  • Splint elbow at 90° flexion
  • Physical Therapy
  • Medications including NSAIDS


  • Indications:
    • Failure of conservative measures
  • 75% of patients improve following surgery if clear space occupying lesion(need citation)
  • Procedure:
    • Surgical decompression of AIN

Return to Play

  • Needs to be updated


  • Motor weakness
  • Chronic pain

See Also



  1. Berger RA. Hand Surgery. Lippincott Williams & Wilkins. (2004) ISBN:0781728746
  2. Tyszkiewicz T, Atroshi I. Bilateral anterior interosseous nerve syndrome with 6-year interval. SAGE Open Med Case Rep. 2018;6:2050313X18777416.
  3. Akhondi, Hossein, and Matthew Varacallo. "Anterior Interosseous Syndrome." StatPearls [Internet]. StatPearls Publishing, 2018.
  4. Aljawder, Abdulla, et al. “Anterior Interosseous Nerve Syndrome Diagnosis and Intraoperative Findings: A Case Report.” International Journal of Surgery Case Reports, vol. 21, 2016, pp. 44–47. PubMed, https://doi.org/10.1016/j.ijscr.2016.02.021.
Created by:
John Kiel on 14 October 2019 18:05:24
Last edited:
27 April 2023 08:25:26