Morton’s Neuroma
What is Morton’s Neuroma? Morton’s Neuroma is a common and painful condition of the ball of the foot. It comes about when the small nerve running between the long bones of the forefoot (metatarsals) is squeezed, just before its entry into two of the toes. This is usually between the third and fourth metatarsals and toes. This site is pictured in the adjacent diagram. Less commonly, it occurs between the second and third toes and rarely between the fourth and fifth toes. It is not usually found in the first interspace, meaning the space between the 1st and 2nd metatarsals. In the diagram, you can see that the nerve divides into two parts between the metatarsal heads, at the point where the space between the bones is narrower. If the nerve is repeatedly damaged by being compressed between the bones, the nerve will thicken, forming a mass on the nerve at this point. The larger the nerve becomes, the greater the likelihood of it being trapped between the bones and so the problem can get progressively worse.
What are the symptoms of Morton’s Neuroma?
Morton’s Neuroma pain occurs almost exclusively when wearing shoes. This is because there is less space between the metatarsal bones the tighter the shoes are. People generally use words like ‘electric shock’, ‘burning’ and ‘searing pain’ to describe their experience. The pain is felt in the ball of the foot but also extending into two toes. There may also be a clicking sensation that occurs at the time of the compression, known as a Mulder’s click. This happens as the swollen nerve is squeezed so hard between the bones that it ‘pops out’ either the top or the bottom, depending on whether it is the dorsal or plantar nerve that is entrapped.
What causes a Morton’s Neuroma?
Morton’s Neuroma comes about when there is not enough room for the nerve in the inter-metatarsal space. Poorly fitting shoes can squeeze this space in obvious ways. Less well known is that rolled in, or pronated, feet can also be implicated in the problem. Pronation makes a difference because the metatarsal bones are deeper than they are wide. When the foot is in a good position, the bones are at their thinnest. When the foot slumps in, the bones rotate about their long axis and take up more room side to side.
How do you treat Morton’s Neuroma?
The progression of treatment is as follows:
- Footwear: For some people, changing shoes may be all that is required.
- Making more space between the metatarsal bones. Padding can be used to spread the toes apart or to lift up one metatarsal of the colliding pair.
- If this padding is not sufficient, orthotics can be used to straighten the whole foot and therefore rotate the metatarsal bones to their thinnest position.
- Injections: Glucose injections can calm the nerve and reduce its size. These are done simply by your podiatrist and are usually well tolerated. They can be done from the top surface of the foot which is less painful than from underneath. Corticosteroids can also be done in the clinic, though generally these are done from below after using a local anaesthetic. Corticosteroids generally could be expected to have a more rapid reduction in pain than glucose. There are pros and cons to discuss before going down this treatment path.
- Radio Frequency ablation is a relatively simple alternative to surgery. It involves inserting a probe into the nerve and heating the probe to kill the tissue. There are fewer complications with this treatment when compared to surgery. This procedure is offered by some radiologists. It is essentially the same as nerve ablation procedures offered for spinal nerve pain syndromes.
- Surgery is rarely used as the simple treatments are very effective for this condition. The surgery would be performed by a podiatric surgeon or orthopaedic surgeon.
- Alcohol Ablation is sometimes used. This involves injection of alcohol into the neural tumour. There are risks involved with this treatment, mostly related to the difficulty of containing the infiltrate to the area of the neuroma. It is not frequently performed.