MORTON’S NEUROMA RFA
Morton’s neuroma (MN) is a painful condition affecting the ball of the foot. The symptoms are commonly sharp, burning pain perhaps with numbness in some cases. There is often radiation to the adjacent toes. The most common spot to develop a MN is between the 3rd and 4th toes, however they are also common between the 2nd and 3rd toes.
The neuroma is not a tumour, despite the -oma which is usually reserved for tumours, but rather the gradual development of fibrosis (collagen) around one of the nerves leading to the two adjacent toes. There are several theories about why these lumps grow and these include increased friction, repetitive weight loading from increased activity and poor footwear, reduced blood supply to the nerves, and suboptimal foot biomechanics or foot deformity. Often there is an improvement by making simple changes such as lower heeled shoes, less time on one’s feet and podiatry treatments including orthotics.
When there is no improvement from trying these simple measures, it is time to visit your GP to discuss the next options. The semi-invasive options include a trial corticosteroid injection (short-medium term relief possible), ethanol ablation and radiofrequency ablation (longer term relief possible). Surgical treatment of neurectomy is also an option and therefore a consultation with a foot surgeon may be appropriate in the correct setting.
Before undergoing an intervention for MN it is important to confirm the diagnosis with ultrasound or MRI scan. Xray is also helpful to assess for structural deformities and rule-out other problems such as stress fracture or arthritis.
Procedure of RFA
The radiologist will first numb the skin at the top of the foot using local anaesthetic before placing a cannula from the top of the foot towards the MN between the toes. This is correctly positioned using ultrasound guidance. An electrode (wire/cable) is then placed through the cannula and dissipates heat/energy directly into the MN for about 3 minutes. This process is not painful and is well tolerated due to the local anaesthetic.
The most important aspect is to have adequate rest following the procedure for 48 hours. Rest, ice and elevation are crucial in order to have a relatively pain free recovery. You can return to most normal activities by day 3, but vigorous exercise should be delayed 2 weeks (specific instructions vary depending on the circumstances). The painful symptoms usually improve gradually over a 6–8-week period. Occasionally pain can continue for longer however this is uncommon. Surgical treatment can still be undertaken if necessary, when there is persistent pain, however the probability of requiring surgery after RFA is about 5-10%.