Benign fibrotic thickening of a plantar digital nerve due to irritation

Aetiology

• Plantar interdigital nerves (from the medial and lateral plantar nerves) overlying the intermetatarsal ligaments can be subjected to repeated trauma
• Irritated nerves can become inflamed and swollen (forming a neuroma)
• The third interspace nerve is most commonly involved followed by the second

Risk factors

• Age - mean age 45-50
• Obesity
• Female - women are four times more commonly affected and the wearing of high heels has been implicated as a cause

Clinical features

Symptoms

• Burning pain and a tingling that radiates to the affected toes
• Pain exacerbated by footwear, and relieved by removal of shoe, massaging foot and changing footwear

Signs

• Loss of sensation in the affected webspace
• Mulder's click test - medio‐lateral compression of the metatarsal heads (exerted by squeezing the forefoot with your hand) may reproduce symptoms or produce a characteristic 'click'

Investigations

• Imaging:
  • X-ray (AP/LAT/oblique WB) to rule out MSK pathology
  • Diagnostic US - swollen nerve (poor specificity if <6mm in diameter - risk of false positive)

Management

• Conservative management ****involves RICE, stretching calf muscles, the use of a metatarsal pad or offloading insole, weight loss if appropriate and activity modification/management advice