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Median Nerve at the Pronator Teres Injection

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Other Names

  • Median Nerve at the Pronator Teres Injection

Background

Course of the median nerve at the elbow[1]
US depicting the median nerve at the level of the pronator teres muscle: axial A) and sagittal B) views. RP Hum = superficial (or humeral) head of the pronator teres muscle. RP Hum = deep (or ulnar) head of the pronator teres muscle. AR = radial artery, AU = ulnar artery. The median nerve (in green) courses between the humeral (RP Hum) and the ulnar (RP Ul) heads of the pronator teres muscle, beneath the division of the brachial artery into its ulnar (AU) and radial (AR) branches. [2]

Key Points

  • High frequency, linear transducer is used
  • Use a 25 to 27 gauge needle, in plane approach
  • Careful identification of anatomy and neurovascular structures is key
  • Can be therapeutic and/or diagnostic

Anatomy of the Median Nerve

Palpation Guidance vs Ultrasound Guidance

  • This procedure can not be safely performed without ultrasound guidance

Indications


Contraindications

  • Absolute
    • Anaphylaxis to injectates
    • Overlying cellulitis, skin lesion or systemic infection
  • Relative
    • Uncertainty in diagnosis
    • Can be treated with less invasive means
    • Hyperglycemia or poorly controlled diabetes
    • Lack of symptom improvement with previous injection

Procedure

Long axis view of the procedure. Long arrow represents angle of entry. Note change of echogenecity from the two smaller arrows[5]
Needle and probe position for long axis approach[5]
Needle approach for short axis view[5]
Needle and probe position for short axis view[5]

Equipment

  • Sterile including chloraprep, chlorhexadine, iodine
  • Gloves
  • Needle: typically 21-25 gauge, 1.5 inch
  • Syringe: 5-10 mL
  • Gauze
  • Ethyl Chloride
  • Bandage
  • Injectate
    • Local anesthetic
    • Corticosteroid
  • Sterile probe cover

Ultrasound Findings

  • Best visualized in short axis
  • In severe cases, enlargement of the nerve may be seen proximal to the compression
  • Follow in short axis until it dives posteriorly to pronator teres
  • The probe can be rotated 90 degrees to see the median nerve in long axis as well

Long Axis, In Plane

  • Patient Position
    • Seated or supine
    • Forearm supinated, elbow neutral
  • Transducer Position
    • Long axis view of median nerve, distal to AC fossa
  • Needle Approach
    • In plane
    • Distal to proximal
  • Target
    • Median nerve between the heads of the pronator teres
  • Pearls and Pitfalls
    • Carefully identify the nerve prior to initiating the injection
    • Use doppler to confirm nothing is intravascular
    • Use caution around the nerve, taking care not to fenestrate

Short Axis, In Plane

  • Patient Position
    • Seated or supine
    • Forearm supinated, elbow neutral
  • Transducer Position
    • Short axis view of median nerve, distal to AC fossa
  • Needle Approach
    • In plane
    • Lateral to medial
  • Target
    • Median nerve between the heads of the pronator teres
  • Pearls and Pitfalls
    • Carefully identify the nerve prior to initiating the injection
    • Use doppler to confirm nothing is intravascular
    • Use caution around the nerve, taking care not to fenestrate

Aftercare

  • Patient should be counseled on
    • Duration of anesthetic
    • Loss of motor function of extensor muscle groups

Complications

  • Intravascular injection
  • Residual motor block
  • Local trauma

See Also


References

  1. Löppönen, Pekka, Sina Hulkkonen, and Jorma Ryhänen. "Proximal median nerve compression in the differential diagnosis of carpal tunnel syndrome." Journal of clinical medicine 11.14 (2022): 3988.
  2. Meyer, Philippe, et al. "The median nerve at the carpal tunnel… and elsewhere." Journal of the Belgian Society of Radiology 102.1 (2018).
  3. Fuss FK, Wurzl GH. Median nerve entrapment: pronator teres syndrome. Surg Radiol Anat. 1990;12(4):267–271.
  4. Wertsch JJ, Melvin J. Median nerve anatomy and entrapment syndromes: a review. Arch Phys Med Rehabil. 1982;63(12): 623–627.
  5. 5.0 5.1 5.2 5.3 Malanga, Gerard, and Kenneth Mautner. Atlas of ultrasound-guided musculoskeletal injections. McGraw-Hill, 2014.
Created by:
John Kiel on 1 December 2023 20:32:37
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Last edited:
3 December 2023 14:35:23
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