Morton Metatarsalgia

Morton metatarsalgia is forefoot pain from perineural fibrosis of a common plantar digital nerve (Morton neuroma). It occurs most often in the third intermetatarsal space (about 65%), then the second (about 30%).

At these sites the nerve is tethered by the deep transverse metatarsal ligament and receives a branch from both the medial and lateral plantar nerves. It is not a true tumour but a degenerative, ischaemic nerve change from repeated compression and traction.

• It is 5 to 8 times more common in women, and peaks at 40 to 60 years.
• Narrow, pointed, high heeled shoes (which compress the metatarsal heads and hyperextend the toes) are the main risk factor.
• Other risk factors: running and sports with forefoot loading (dancers, runners, racket sports), flat or high arched feet, hallux valgus, hammertoes and tight calf.
• Bilateral disease occurs in about 15%.
• Asymptomatic neuromas are found on imaging in 30 to 35% of people, so imaging must be matched to symptoms.

• Burning, sharp or electric pain in the forefoot between the metatarsal heads, radiating into the toes, with numbness and tingling of the adjacent sides of the third and fourth toes (or the second and third).
• A sensation of walking on a pebble, a fold in the sock or a bunched up sock.
• Symptoms are worse in tight shoes, high heels, on hard surfaces, during prolonged walking, and standing on tiptoe, and relieved by removing the shoes and massaging the foot, wide shoes and rest. Night pain is unusual.
• Examination: tenderness in the affected web space (pressure from the plantar surface between the metatarsal heads).
• Reproduction of pain and a palpable click when the forefoot is squeezed from the sides while pressing the web space (a palpable, painful click as a neuroma moves between the heads).
• Reduced sensation between adjacent toes, toes splayed (Sullivan sign), and no joint swelling or limited metatarsophalangeal movement.
• Differential diagnosis: metatarsalgia from other causes, metatarsophalangeal joint synovitis or instability (plantar plate tear), stress fracture of a metatarsal, Freiberg infraction, intermetatarsal bursitis, tarsal tunnel syndrome, peripheral neuropathy (diabetic, alcoholic, B12 deficiency), S1 radiculopathy, rheumatoid arthritis, gout, ganglion, and tumour.
• Red flags: fever, rest or night pain, sudden swelling, bilateral symptoms with systemic features, weakness, and loss of sensation over a wider area.
• Complications: chronic pain, altered gait, fear of walking, and secondary metatarsalgia.

• Clinical, based on the pain in a web space and the click on the squeeze test. Assess the neurovascular status of the foot.
• Ultrasound (dynamic, with a high frequency probe) shows an oval, hypoechoic mass between the metatarsal heads, with a sensitivity of about 80 to 95% for lesions of 5 mm or larger, and guides injection.
• MRI shows a low T1 and variable T2 oval mass and excludes other causes, and is used when ultrasound is inconclusive. Lesions smaller than 5 mm are often asymptomatic.
• X-ray (weight bearing foot) excludes stress fracture, arthritis, and deformity.
• Blood tests (HbA1c, B12, CRP, urate) and nerve conduction studies when a generalised neuropathy or radiculopathy is suspected.
• Diagnostic injection of lidocaine 1% (1 to 2 mL) into the interspace with relief of symptoms supports the diagnosis.

• Footwear and offloading, first line for 6 to 12 weeks:
  • Wide, deep toe box, low heel (below 3 cm), and a firm, cushioned sole. Avoid high heels and pointed shoes.
  • A metatarsal pad (dome) placed just behind (proximal to) the metatarsal heads, so it spreads the heads and offloads the nerve, or a custom orthosis with a metatarsal dome.
  • Rocker sole shoes for forefoot offloading.
  • Toe spacers and avoidance of toe hyperextending activities.
  • Weight loss when overweight.
• Analgesia: paracetamol 1 g orally 6 hourly. NSAIDs (ibuprofen 400 mg 8 hourly with food, or naproxen 500 mg 12 hourly) for 1 to 2 weeks, with limited benefit. Topical diclofenac 1% gel.
• Neuropathic pain agents for persistent burning: gabapentin 300 mg at night increasing to 900 to 1800 mg daily, pregabalin 75 mg twice daily, or amitriptyline 10 to 25 mg at night.
• Corticosteroid injection for symptoms persisting after 4 to 6 weeks of footwear changes: methylprednisolone acetate 20 to 40 mg or triamcinolone acetonide 20 mg with lidocaine 1% or bupivacaine 0.25% 1 to 2 mL. Inject from the dorsal approach into the intermetatarsal space (preferably under ultrasound guidance).
• About 30 to 60% have relief lasting months.
• Risks: fat pad atrophy, toe instability or dislocation (injection near the plantar plate), skin depigmentation, and a rise in glucose for 3 to 5 days in diabetes.
• Limit to 2 injections, at least 3 months apart.
• Alcohol sclerosing injection: ethanol 4% (a dilution with bupivacaine 0.5%) 0.5 to 1 mL into the interspace under ultrasound guidance, weekly for 3 to 7 sessions, with about 60 to 85% success (evidence limited and technique dependent). Pain after injection is common.
• Other options with limited evidence: radiofrequency ablation (pulsed or thermal), cryoneurolysis, and extracorporeal shock wave therapy.
• Surgery for failure of 3 to 6 months of treatment: excision of the neuroma (neurectomy) through a dorsal or plantar incision, with about 75 to 85% good results.
• Complications: permanent numbness of the toe sides, stump neuroma (about 5 to 10%, with recurrent pain), and wound problems.
• Intermetatarsal ligament release (neurolysis) is an alternative with preserved sensation. Revision surgery for a stump neuroma has lower success.
• Special groups:
  • Pregnancy: wide shoes, metatarsal pads and paracetamol. Avoid NSAIDs after 20 weeks.
  • Diabetes: neuropathy can mimic or coexist with neuroma, so test sensation and avoid injection if the circulation is poor.
  • Athletes and dancers: footwear changes, forefoot padding, and graded return.
  • Elderly: check circulation and sensation.
  • Renal impairment: reduce gabapentin and pregabalin doses.
• Follow up: review at 6 weeks and 3 months. Refer to podiatry, orthopaedics or foot and ankle surgery for no improvement by 3 to 6 months, diagnostic doubt, or consideration of sclerosing therapy or surgery.