Morton's Neuroma: Does Size Matter?
When it comes to the treatment of Morton's neuroma, does size matter when results are measured between steroid injection and injection of just a numbing agent? Another way to pose the question is to ask: is there any difference in results when treating Morton's neuroma with steroid injection versus an analgesic (like novocaine)? Does size make any difference?
Interdigital neuroma (sometimes called a Morton's neuroma) is the medical term for a painful growth in the forefoot. The pain is most commonly felt between the third and fourth toes but can also occur in the area between the second and third toes.
The most common cause of pain is thought to be irritation on the nerve. The chronic nerve irritation is believed to cause the nerve to scar and thicken, creating the neuroma. Many foot surgeons feel that the problem may arise because the metatarsal bones squeeze in on the nerve, and the ligament that joins the two bones irritates, or entraps, the nerve. Entrapment of the nerve that is in the space between the toes is thought to lead to the chronic irritation and pain.
The pain occurs most often in the ball of the foot when weight is placed on the foot. Many people with this condition report feeling a painful catching sensation while walking, and many report sharp pains that radiate out to the two toes where the nerve ends. There may be swelling between the toes or a sensation similar to having a rock in the shoe. This can feel like electric shocks, similar to hitting the funny bone of the elbow.
Treatment usually begins with changes in shoe wear. Sometimes simply moving to a wider shoe will reduce or eliminate the symptoms. A firm, crepe-soled shoe may help. The firm sole decreases the amount of stretch in the forefoot as the affected person takes a step. This lessens the degree of irritation on the nerve.
Also, an injection of lidocaine and cortisone into the area may help temporarily relieve symptoms. This is usually short-lived (days to weeks) and is mainly useful to help the doctor make a diagnosis. A study in Scotland was done to test out whether a corticosteroid injection is more effective than an anesthetic injection.
Half of the 131 patients (85 per cent women, 15 per cent men) were given a single injection of methylprednisone (a corticosteroid antiinflammatory) combined with an anesthetic (numbing agent) directly into the neuroma. Ultrasound was used to guide the needle into the neuroma. The other half received the same treatment but with just the anesthetic (lignocaine). Results based on pain, function, and patient opinion of their own general health were measured one- and three-months later.
Tools used to measure results included a Foot Health Thermometer (used to record general foot health), the Manchester Foot Pain and Disability Schedule, and the Multidimensional Affect and Pain Survey (MAPS). Combined together, these patient-surveys provided information on pain, work and activity levels, walking, sense of well-being, emotional pain, rating of general health, and quality of life.
They found a significant difference (greater improvement in the corticosteroid group) one month and three months after treatment. The ultrasound showed how large the neuromas were so the researchers could use that information to see if size matters. It turns out that size did NOT make a difference. Patients with small to large neuromas received the same amount of relief and improvement with the corticosteroid injections. For the most part, results favored the use of corticosteroid injection. Complete pain relief was not reported in either group.
In summary, surgery to remove painful neuromas (which is often unsuccessful or causes other complications) may not be needed. The success of corticosteroid injections may be better than previously reported. At least according to the authors of this randomized, controlled trial, the use of methylprednisolone can provide effective relief of painful symptoms for at least three months. Longer follow-up will be conducted to see the long-term results as well.
Colin E. Thomson, BSc (Hons), PhD, et al. Methylprednisolone Injections for the Treatment of Morton Neuroma. In The Journal of Bone and Joint Surgery. May 1, 2013. Vol. 95A. No. 9. Pp. 790-795.