Why does the nerve thicken?
The common plantar digital nerve passes between the heads of the metatarsal bones, which divides and goes to adjacent toes. Above it is the transverse intermetatarsal ligament. With transverse flatfoot, the forefoot widens, the heads of the bones move closer together with each step, and the nerve becomes pinched between the bone and the ligament. Constant irritation causes swelling and then the growth of dense connective tissue around the nerve. It is this thickening that is called a neuroma, although it is not a tumor.
- Chronic compression of the nerve between the metatarsal heads
- The third intermetatarsal space is the most common location
- Fibrous thickening, not tumor
- Bilateral form is rare
Causes and risk factors
The main external factor is shoes: a narrow toe shifts the bones, a heel higher than 5 centimeters transfers weight to the forefoot. Therefore, Morton's neuroma is several times more common in women. Internal causes are related to the structure of the foot: transverse flatfoot, hallux valgus, hammertoes, excessive joint mobility. Additional stress comes from running, standing for long periods of time at work, excess weight, as well as squats and calf raises when playing sports.
- Narrow shoes and high heels
- Transverse flatfoot
- Hallux valgus and hammertoes
- Running and long walking on hard surfaces
- Work on the feet
- Overweight
- Previous forefoot injuries
Symptoms
A typical complaint is a burning or shooting pain in the ball of the foot, radiating to two adjacent toes. Many people describe feeling as if there is a pebble in their shoe or a sock that has become wrinkled. There is often numbness or tingling in the fingers. The pain appears after some time of walking, makes you stop, take off your shoes and stretch your foot - after that it becomes easier. Over time, attacks become more frequent and occur even in soft shoes. Externally, the foot is usually unchanged, there is no swelling or redness.
- Burning and shooting in the forefoot
- Sensation of a foreign body under the pad
- Numbness and tingling of two adjacent fingers
- Increased pain in tight shoes and high heels
- Relief after removing shoes and foot massage
- No visible swelling or redness
Diagnostics
The diagnosis in most cases is made clinically. The doctor presses on the space between the toes and at the same time squeezes the foot from the sides: with a neuroma, pain occurs, and sometimes a click is felt. Check the sensitivity of the fingers and the condition of the arches of the feet. Soft tissue ultrasound is an available method that shows nerve thickening and can distinguish it from bursitis. MRI of the foot is used for questionable results or before surgery. An X-ray itself does not show a neuroma, but is needed to rule out a stress fracture of the metatarsal bone and arthrosis.
- Forefoot compression test
- Testing finger sensitivity
- Ultrasound of the soft tissues of the foot
- MRI of the foot with an unclear picture
- X-ray of the foot bones to rule out a fracture
- Examination by a neurologist for numbness of the entire foot
Treatment and prevention
Treatment begins with unloading the nerve. Shoes are changed to models with a wide toe, a hard back and a heel no higher than 3 centimeters. Custom insoles with a metatarsal pad spread the metatarsal heads and relieve pressure. Reduce running loads, add exercises for the foot muscles and stretching of the calf muscles. Physical therapy - ultrasound, shock wave and laser therapy - can help reduce pain. If the effect is insufficient, the doctor may suggest glucocorticoid injections or sclerotherapy. If the pain persists for several months and interferes with walking, an operation is performed: dissection of the ligament or removal of the altered section of the nerve; After removal, there remains an area of numbness between the fingers.
- Shoes with wide toes and low heels
- Custom insoles with metatarsal pad
- Temporary restrictions on running and long walking
- Shock wave and ultrasound therapy
- Foot exercises and calf stretches
- Injections as prescribed by a doctor
- Surgery for persistent pain for more than 3–6 months