Some people have bone or nerve structures that are slightly different to those found in the ‘typical’ human model. These features are often inherited and can cause a neuroma to form. We have described examples of these common ‘anatomical’ causes of Morton’s neuroma below.
Metatarsals that are too close together
Several studies have shown that people whose metatarsals are situated close together are more likely to develop Morton's neuroma. In these cases, the neuroma may be more likely to recur after treatment. It may also be more resistant to conservative treatments like orthoses.
Lack of fibro fatty padding
Some people are more "bony" and lack natural padding under their feet. For others, the fat pad may have wasted away because of multiple steroid injections (which is why we discourage multiple injections).
For people who have these characteristics and suffer from Morton’s neuroma, the main treatment is to reduce focal force to a more normal level. This is measured with our kinetic pressure system, and treatment comes in the form of prescription orthoses and footwear change. Whilst there are also various "fillers" that can be injected under the ball of the foot, we do not endorse this procedure. This is because most "dermal fillers" break down and are absorbed by the body relatively quickly. Similarly, we do not advise longer-acting fillers such as silicone, as the long-term risks are not currently known.
Morton's foot type
This foot type is characterised by a first metatarsal that is shorter than the others. The result is that the second, third and fourth metatarsals take more pressure, which leads to overload, metatarsal shear and, often, the formation of a neuroma.
In cases of Morton’s foot type, we will initially attempt to achieve normal loading across the metatarsals by non-surgical means, and treat the neuroma through techniques such as cryosurgery. Where symptoms persist, Mr McCulloch may offer surgery to correct the length of the metatarsals.
Abnormal thickening of the 3-4 interdigital nerve
The nerve between the third and fourth toes may be anatomically thicker than the nerves between the other toes. This naturally-occurring thicker nerve may be at risk of developing a neuroma, especially if other risk factors, such as increased pronation, are present.