Should I consider a steroid injection for Morton's neuroma and what are the risks of having a steroid injection for Morton's neuroma?
Patients often ask our Centre about steroid injections for the treatment of Morton's neuroma. There is some evidence that Morton's neuroma can be treated in the short term by steroid injections but the evidence for long-term benefit is limited. Furthermore, there are a number of recognised risks with steroid injection which the patient needs to carefully consider and be counselled on, before having an injection for Morton's neuroma.
The main risk of steroid injection for Morton's neuroma includes skin de-pigmentation which can be distressing for some patients. The de-pigmentation is more likely to show up in patients who have a darker skin type. This is difficult to treat and may not resolve. Another complication from a steroid injection for Morton's neuroma is fat atrophy which effectively means that the fat breaks down between the metatarsals and sometimes underneath the metatarsals. Because the foot is dependent on an amount of fatty padding for normal function, fat atrophy can have a negative effect and potentially cause other kinds of forefoot pain. Clearly, if the patient already has a foot with minimal natural fat padding then the effects from a steroid injection for Morton’s neuroma can be more dramatic. A single injection can cause a fairly significant degree of fat atrophy but severe atrophy is mostly seen in patients who have undergone multiple injections and this is one reason why The London Podiatry Centre would not advocate more than one or two injections. Another risk associated with steroid injection for Morton's neuroma is associated damage to the soft tissue ligaments and joint capsule. If the steroid is positioned too close to the proximity of ligaments or the joint capsule then there is some evidence that this can cause disruption and damage to these structures, particularly if they are already compromised. For example, if a patient has a Morton's neuroma with a hammer toe which has weakened the ligaments around the joint, then the additional steroid may cause further damage to the hammer toe and worsen its position.
Patients may also suffer a steroid flare which is usually temporary, lasting no more than 40 hours, although there may be rarer exceptions. There are also rarer complications associated with steroid injection including allergy and there is a reported case in The Journal of Foot and Ankle Surgery (available online dated 21st of January 2016 and currently in press) which reports de-pigmentation along lymph vessels of the foot following a cortisone steroid injection for interdigital neuroma.
The adverse effects of steroid injection, together with the short term benefit in most instances leads The London Podiatry Centre to advocate cryosurgery as an alternative and preferred option. Although cryosurgery is not free of risk of complication, the aforementioned complications associated with steroid injection have not been noted in relation for cryosurgery for Morton’s neuroma. The London Podiatry Centre has seen no evidence of fat atrophy, discoloration or significant soft tissue damage associated with cryosurgery for Morton's neuroma.
In summary, patients who are at greater risk from the side effects of steroid injection for Morton's neuroma include:
1) Those patients with "bony feet", where this is very little natural padding under the foot.
2) Patients who are prone to various types of allergic reaction and particularly those who may have had an adverse effect from steroid injections in the past.
3) Those patients who have had a number of previous steroid injections for Morton's neuroma.
4) Those patients who have noted significant wastage and depigmentation from a single injection for Morton's neuroma in the past should not have further injections.
5) Those patients who already have weakness and some degree of displacement from the toes in association with Morton's neuroma. (For example claw, mallet or hammer toes).
6) Patients who are generally concerned about the use of steroids and who may have had multiple injections with steroids for other reasons.
7) Patients who have conditions which already place the joints at greater risk should be cautious about having steroid injections for Morton's neuroma (i.e. unstable joints due to rheumatoid arthritis.