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Ultrasound · Foot

Morton's Neuroma Injection (Dorsal Approach)

footmorton's neuromametatarsalweb space

Treats

  • Interdigital neuralgia (Morton's neuroma)
  • Intermetatarsal bursitis

Contraindications

  • Active local skin infection at entry site (absolute)
  • Known allergy to local anesthetic, steroid, or antiseptic prep
  • Therapeutic anticoagulation — review case-by-case
  • Uncontrolled diabetes (relative)

Pre-procedure checklist

  • Confirm patient identity (two identifiers)
  • Confirm procedure, side, and TARGET WEB SPACE — mark with patient awake
  • Review allergies and anticoagulation
  • Confirm informed consent
  • Pre-scan: identify the neuroma in the target web space; perform Mulder's maneuver to confirm; identify the deep transverse intermetatarsal ligament; Doppler deep plantar metatarsal vessels
  • Time-out immediately before needle entry

Positioning

  • Supine; foot resting on table; toes slightly flexed
Positioning

Probe

  • High-frequency linear probe (6-13 MHz)
Probe

Landmarking — find the view

  • Mulder's Maneuver: Squeeze the forefoot transversely (medial-lateral compression of the metatarsal heads) while simultaneously applying plantar pressure on the suspect interspace. Watch in real-time for the hypoechoic neuroma to 'pop' dorsally between the metatarsal heads — this is the sonographic Mulder's click and confirms target identification.
  • Transverse Scan: Identify the target web space (usually 2nd-3rd or 3rd-4th).
  • Identify the hypoechoic 'dumbbell' or round mass as it 'pops' dorsally during compression.
  • Identify and avoid the intermetatarsal bursa, which often sits just superficial to the neuroma.

The correct ultrasound view

  • Hypoechoic mass in the intermetatarsal space; metatarsal heads on either side.
The correct ultrasound view

Needle corridor

  • Dorsal in-plane approach directly into the intermetatarsal space, traversing the deep transverse intermetatarsal ligament to reach the neuroma plantar to it.
Needle corridor

Avoid

  • Deep plantar metatarsal vessels
  • Adjacent (non-target) digital nerves in neighboring web spaces. Note: target IS the common plantar digital nerve — aim for PERI-NEURAL placement around the hypoechoic mass, not intraneural.

Steps

  1. 1Advance dorsal-to-plantar under real-time US.
  2. 2Feel for a subtle 'pop' as the needle traverses the deep transverse intermetatarsal ligament.
  3. 3Target the peri-neural space around the hypoechoic mass.
  4. 4Inject 0.5-1 mL total (lidocaine + steroid premixed); watch for fluid surrounding the neuroma.
  5. 5STOP IMMEDIATELY if the patient reports electric, shooting, or paresthetic sensations into the toes.

Tips

  • Dorsal approach is safer and avoids painful plantar weight-bearing skin.
  • Larger volumes risk spread to adjacent interspaces and plantar fat pad atrophy.
  • Limit to 2-3 injections per site per year.
  • If color Doppler shows a deep plantar vessel in the planned path, abandon and re-plan.

Resident pearls

  • Mulder's = medial-lateral squeeze + plantar push. Don't rely on plantar-only pressure.
  • The neuroma sits PLANTAR to the deep transverse intermetatarsal ligament. From a dorsal approach, feel for a subtle 'pop' through the ligament and confirm tip is deep to it. Stopping above the ligament deposits steroid in the intermetatarsal bursa instead of around the neuroma.
  • Identify and avoid the intermetatarsal bursa, which may also be inflamed.
  • Steroid in the plantar fat pad can cause atrophy — the dorsal approach minimizes this risk.

Supplies

  • 3 mL Syringe
  • 25G 1" or 1.5" Needle (use ≥ 25G if injecting triamcinolone — 27G can clog with particulate suspension)
  • 18G Drawing Needle
  • 1% Lidocaine (0.5 mL)
  • Dexamethasone 4 mg (PREFERRED — non-particulate, no clog risk, lower fat-atrophy risk) OR triamcinolone 20 mg
  • Alcohol Swabs (vial tops)
  • Betadine/Chloraprep
  • Sterile Gloves
  • Sterile 4x4 Gauze Pads
  • Sterile Towels & Drapes
  • Adhesive Bandage (Band-Aid)
  • Washcloth/Towel (gel cleanup)
  • Needle Disposal Safety Cap
  • Sterile probe cover & gel

Post-procedure

  • Apply a clean dressing; remove after 24 hours.
  • Local anesthetic relief for 1-4 hours; steroid begins 24-72 hours.
  • Steroid 'flare' in 2–10% — manage with ice and acetaminophen.
  • Post-injection neuritis: transient burning or aching in the toes for 24-72 hours is well-recognized after interdigital nerve injection — counsel the patient before the procedure.
  • Rest the foot 24-48 hours; avoid tight footwear and wear cushioned shoes.
  • Return immediately for: spreading redness, swelling, fever, disproportionate pain, OR new toe numbness or color change.
  • Diabetics: expect 50-100 mg/dL glucose rise for 3-5 days.
  • Maximum 2-3 injections per site per year.