“You then realised have important your feet are until they hurt”
Pain in the ball of the foot is a common presentation. Although Morton’s neuroma is easily remembered, on account of its special name, it is in fact a relatively rare cause of metatarsalgia.
Metatarsalgia describes the pain but is not a diagnosis. The word literally means foot ache and therefore is no more precise than the analogous term headache.
The three most usual diagnoses causing metatarsalgia are:
- Inflammation and synovitis from the second toe knuckle joint (metatarsophalangeal joint). The cause of this usually relates to mechanical overload of the second toe either because of a big toe problem or because of a tight Achilles tendon. Synovitis and pain (sometimes called capsulitis) are the first stage in the development of a hammer toe.
- Stress fracture. Here the clue is in the history. Change in activity levels or increased body weight increases demands upon the bone. The second metatarsal is the most commonly affected. This is sometimes called a March fracture because of its association with new army recruits endlessly practising drill on the parade square. Tenderness and swelling are seen proximal the toes. The area can be red and hot leading to a frequent miss diagnosis of cellulitis.
- Morton’s neuroma refers to bursitis around and/or swelling of the interdigital nerve. It is most commonly seen between the middle and fourth toes and also between the second and middle toes. There may be altered sensation of the toe and the symptoms are aggravated by tight shoes. The pain is often burning in nature. There is no visible swelling.
If symptoms are of recent onset, a pragmatic course of action may be appropriate. Wide fitting firm supportive shoes, a metatarsal dome orthotic, weight loss and stretching exercises for a tight calf muscle all play a part.
If these first line treatments are not sufficient then further investigation is recommended. Standing X-rays and MRI are both useful, but ultrasound has the added benefit of being able to proceed to injection if appropriate.
SECOND LINE TREATMENT
For Morton’s neuroma a targeted injection into the affected webspace is useful. It is important to ascertain the initial benefit of the injection (when the local anaesthetic has selectively numbed the area) for diagnostic purposes. If there is no improvement in this phase then it is likely that the source of pain is not the nerve. Sometimes the longer-term benefits of cortisone produce lasting improvement but for a proportion of patients the pain eventually comes back.
At this stage, traditionally, a further cortisone injection might be considered or else discussion veer towards surgical treatment. Surgery to remove the Morton’s neuroma carries a long recovery period and carriesl risks. For these reasons alternative treatments are appealing.
MINIMAL ACCESS TREATMENT TO AVOID SURGERY
Some years ago there was interest in nerve ablation with ethanol injections. This has subsequently been proven ineffective.
Cryotherapy aims to reduce pain by freezing the nerve. This treatment is not widely available in the UK and the recovery period extends to many months.
Radiofrequency ablation is a minimally invasive technique used in a variety of musculoskeletal contexts (most notably the spine).
The procedure is performed under ultrasound guidance using local anaesthetic to numb the area. A radiofrequency needle is then passed into the bursa and used to shrink and denervate the area. There are no skin stitches to heal and recovery is much more rapid than after surgical neurectomy. Some patients do experience temporary swelling and discomfort.
Experience at the London Foot and Ankle Centre shows that fewer than 20% of patients who have radiofrequency nerve ablation subsequently require surgical treatment. The treatment can be effective in cases of “stump neuroma” that complicate surgical excision.
In the small number of patients who to resort to surgery later there are no difficulties from having had the radiofrequency treatment first.