Footmed - Footmed Foot and Ankle Clinics

What is wrong with my foot?

Morton's Neuroma is a pathological condition of the common digital nerve, most frequently between the third and fourth metatarsals (third inter-metatarsal space). The nerve sheath becomes abnormally thickened with fibrous (scar) tissue. A diagnostic ultrasound may be ordered to confirm this.

Pain most commonly in the ball of the foot and affecting one or two of the lesser toes (usually the third and fourth).

 Pain can sometimes radiate to the top of the foot

• The pain may can be intermittent in nature - it may disappear as quickly as it came
• Pain is often sharp, burning, or cramping in nature
• Pain may radiate into the tips of the toes or up the foot/ leg
• Aggravated by tight shoes and prolonged weight-bearing
• Removing the shoe often relieved the pain

Why has this happened?

The exact cause is not fully understood. A neuroma most often affects women over 50 years of age and aggravated by tight or high-heeled shoes. Faulty foot mechanics is thought to play a role.

The condition seems to occur in response to irritation, pressure or injury to one of the nerves that lead to your toes. The neuroma is part of your body's response to the irritation or injury. In some cases, Morton's neuroma may result from abnormal movement of your foot, caused by bunions, hammertoes, flatfeet or excessive flexibility.

Do I have to have an operation?

Pads, rest, ice, anti-inflammatory medication can help improve comfort. Wide shoes with foot orthoses and cortisone injections may resolve the pain in some people (3). If the neuroma is small in size a course of 5-6 injections of local anasthesetic around the neuroma can also be helpful. No long-term studies are available. However, surgery is indicated if these measures are ineffective and the problem continues to interfere with your quality of life.

What will the operation involve?

The operation involves removing the enlarged nerve by a cut made on the top of the foot. The deep transverse metatarsal ligament suspected of causing some of the constriction above the nerve is released. The thickened nerve is then isolated from the surrounding tissue and cut where the nerve trunk appears normal again. An inflamed intermetatarsal bursa is often present and this is also removed. The specimen is sent for a pathology examination.

How successful is the operation?

This operation (neurectomy) by a dorsal approach has shown good to excellent patient satisfaction rates (78-84%) in two good studies (1,2). The Coughlin & Pinsonneault (1) study is a long term follow up after 11 years.

 Are there any risks associated with the operation?

• Infection (smoking increases by 16X)
• Stump neuroma can occur when little sproutlets of nerve from the cut end of the nerve starts to grow again. These sproutlets can grow into a ball that hurts like (or more than) the original neuroma and this requires further surgery to rectify.
• Wound problems (slow to heal)
• Scar sensitivity
• Nerve Injury (Nerves can be bruised which resolves but you can be left with permanent numbness)
• CRPS = Complex Regional Pain Syndrome (Rare <1%)
• Deep Vein thrombosis (clot in deep vein in the legs)

The underneath of the foot can remain tender for about 3-4 months after surgery. This is likely to resolve on its own without treatment. An orthotic will also help.

References:

(1) Coughlin & Pinnsonault. (2001). Operative Treatment of Interdigital Neuroma. A Long term follow up study. Journal of Bone & Joint Surgery (Am)

(2) Giannini S, Bacchini P, Ceccarelli F, Vannini F (2004). Interdigital neuroma: clinical examination and histopathology results in 63 cases treated with excision. Foot & Ankle International

(3) Saygi B, Yildirim Y et al (2005). Morton Neuroma: Comparative Results of Two