The condition that we now know as Morton’s neuroma was first described by Queen Victoria’s foot doctor, Lewis Durlacher. In 1883 Durlacher suspected the forefoot pain was being caused by a tumour of the nerve and as such, he recommended and performed excision. Since the time of Durlacher, Morton’s neuroma have been cut out, a process known as excision or neurectomy. The procedure described by Durlacher is still performed by many in almost an identical fashion today.
Is a Victorian treatment the best answer for today’s Morton’s sufferer?
Well, simple the answer is no, because Durlacher was mistaken about the true nature of Morton’s neuroma. The nerves in the forefoot causing pain, are not ‘true’ neuromas or neuromata (plural).
Technically speaking, the term Morton’s neuroma is a misnomer. In other words, it is not a ‘true neuroma’ because it is not a malignant or benign tumour of the nerve and it has not resulted from amputation or trauma to the nerve.
The irony of using a surgical technique normally reserved for ‘true neuromata” on a Morton’s neuroma is that the surgery can actually cause a true neuroma or more accurately a ‘stump neuroma’. The pain from a stump neuroma is often of a much greater intensity than a Morton’s neuroma, and is often present at rest as well as weight-bearing. Such pain can disrupt sleep and overall has a much greater disabling effect than a Morton’s neuroma.
Nerve transplant surgery appears to be the only glimmer of hope for the seemingly incurable condition of stump neuroma.
What do we know about stump neuroma?
We now think that everyone that has excision surgery will develop a stump neuroma. The end of the nerve that was cut forms a swollen, bulbous, disorganised bundle of nerve fibres. Put simply, a stump neuroma is a normal physiological response to the nerve being cut. However, the current thinking is that about 20-30% of such stump neuroma become painful.
Why are stump neuroma so painful?
It is thought by some that it is because the stump forms in a weightbearing part of the foot subject to sheering and compressional forces. Others recognise that stump neuroma can form even in non weight-bearing areas of the foot and the pain could simply result from the disorganised repair of the nerve fibres.
The rates of painful stump neuroma are hard to estimate as most patients who undergo excision surgery are discharged 3-4 months post-operation. Painful stump neuroma can form within 3-4 months post-op, but many take as long as 12-18 months, sometimes even longer. This is most likely why studies that report on Morton’s neuroma excision outcomes generally report better outcomes if the follow up is conducted within the first few months of surgery. The studies that follow patients up over a 5-10 year period tend to show poorer patient outcomes and higher rates of painful stump neuroma formation.
So, what exactly is a Morton’s Neuroma and how best should it be treated?
Technically it is a perineural fibrosis. Let’s break it down. ‘Peri’ derived from the Greek word ‘around’, ‘neural’ (nerve) ‘fibrosis’ (scaring). So, in plain English a Morton’s neuroma is a nerve that has developed scar tissue around the nerve sheath. Normally, an interdigital nerve in the forefoot measures anywhere between 1.8 – 2mm in diameter. As the scar tissue around the nerve accumulates, the nerve increases in diameter. In our experience at The Barn Clinic treatment centres, when the nerve exceeds 4mm, patients will start to experience intermittent symptoms of burning and numbness. As the nerve increases in diameter, the symptoms become more pronounced. In extreme cases the nerve diameter can exceed 10mm. Such enlargements of the nerve cause a ‘V’ shape splaying of the toes called ‘diastasis’, and an annoying, distracting, clicking sensation felt when the thickened nerve moves up and down when walking.
Why is cryosurgery preferable to neurectomy or decompression surgery?
Cryosurgery triggers a process known as Wallerian degeneration. Wallerian degeneration results in a breakdown of the perineural scar tissue. The scar tissue is absorbed by white blood cells called macrophages. Four days after cryosurgery the macrophages have done their job and the nerve begins the repair process.
Typically, three months later the treated nerve will have fully recovered. The nerve will also have regained normal sensation, (even when the nerve had previously lost its sensation).
The main benefit is that the nerve has not been cut and therefore there is no risk of stump neuroma, for which there is currently no real cure.
If after cryosurgery being pain free without numbness isn’t good enough, there is yet another huge benefit to cryosurgery. The nerve also returns to a normal thickness. This means that the annoying clicking sensation felt when the nerve moves up and down disappears too.
As the nerve has returned to a normal diameter of 2mm there is no need for decompression of the nerve either. Decompression of the nerve involves cutting into healthy surrounding structures, such as ligaments in order to make room for the enlarged nerve. Cutting the main transverse ligament in the forefoot can cause problems such as instability and pre-dislocation syndrome.
Decompression surgery can sometimes result in scar tissue formation at the site where the ligament was cut. Such scar tissue will then in turn re-compress the neuroma.
The benefits of decompression are often short lived because the ligament will eventually heal and again re-compress the neuroma.
Is cryosurgery safe?
Being the first clinician in the UK to pioneer, develop and perfect cryosurgery for the treatment of Morton’s neuroma and with 10 years of experience, I can now honestly say that I regard cryosurgery to be even safer than a steroid injection.
How does the recovery process and complication rate from neurectomy compare to cryosurgery?
Surgical shoe or orthopaedic boot:
- Following neurectomy (excision surgery): You will have to wear a surgical shoe for 2 weeks followed by wide fitting shoes for 2 months. Some studies suggest that 71% patients following neurectomy surgery will experience lifelong issues using normal footwear.
- Following cryosurgery: You should wear a roomy shoe or sandal on the day of treatment. Normal footwear can be worn again after 24 hours.
- Following neurectomy (excision surgery): The use of crutches is required for 4 weeks.
- Following cryosurgery: No crutches are required.
- Following neurectomy (excision surgery): You will unable to drive for approximately 2 weeks.
- Following cryosurgery: You can drive after 3 days.
- Following neurectomy (excision surgery): Stitches are in place for 2 weeks and the foot needs to be kept dry to avoid infection.
- Following cryosurgery: No stitches or sutures are used. The foot needs to be kept dry for 3 days. Showering is permitted at 3 days.
Dressings and bandages:
- Following neurectomy (excision surgery): Dressing and bandages need to use for approximately 4 weeks.
- Following cryosurgery: A small dressing and bandage needs to be kept in place for 3 days.
- Following neurectomy (excision surgery): Most patients will experience permanent numbness in the toes and ball of the foot, with some partial improvement seen at 9 months.
- Following cryosurgery: Patients will experience temporary numbness for 3 months, followed by a return of full sensation from 4 months onwards.
- Following neurectomy (excision surgery): The foot can be swollen anywhere from 6-12 months.
- Following cryosurgery: The foot will look completely normal with no visible swelling
- Following neurectomy (excision surgery): A plantar scar on the sole of the foot can be painful to walk on if the scar is not localised to the recess between the metatarsals. On rare occasions the scar from Morton’s neuroma neurectomy surgery can become infected and develop long-term discolouration as seen below or keloid scaring.
- Following cryosurgery: Leaves no scar at all.
- Following neurectomy (excision surgery): Vitamin E and a moisturiser should be applied to the scar for 3-4 weeks after the removal of the sutures.
- Following cryosurgery: As there is no scar, so no action is required.
- Following neurectomy (excision surgery): 5% infection rate.
- Following cryosurgery: 0 cases in 5000 performed over the last 10 years.
Complex regional pain syndrome also known as reflex sympathetic dystrophy syndrome.
Complex regional pain syndrome (CRPS) is estimated to occur in 1-2% of all nerve excision surgery. It is a poorly understood condition that often results in high levels of pain, altered blood flow, mental health issues such as depression and in extreme cases, amputation of the foot or leg. It is thought to be an abnormal response to trauma caused to the nerve. The average duration is of CRPS is 36 months. To date worldwide, there has not been one single reported case of CRPS following cryosurgery for Morton’s neuroma. Interestingly at The Barn Clinic treatment centres, we have used cryotherapy to successfully treat CRPS that resulted from excision surgery.
Mr Robin Weaver: The Barn Clinic treatment centres in London & Sheffield