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Are podiatrists in NZ allowed to inject LA into inter-metatarsal space for the purpose of diagnosing Mortons Neuroma?

 

You are allowed to inject LA, so why not?

BUT, how do you diagnose a Mortons neuroma by injecting LA?

 

I think a general assessment (mets through ROM, medial/lateral compression of mets, mulders sign) would generally be enough to diagnose an individual with mortons neuroma. LA merely confirms diagnosis and is a form of treatment. So I think my question was rather whether we could provide LA as a treatment option if conservative measures fail.

 

How? An LA is going to anesthetize everything where you inject. How will that tell you it is a neuroma?

 

How about MSU for Dx?

Diagnosis vs Treatment is different question.

 

Are you trying to narrow down ddx for persistent insidious onset metatarsalgia which is non responsive to mechanical measures so you can revise a treatment plan??

As Craig stated, an inter-metatarsal space injection is not that specific a test. What it will infer, if you serially selectively block the plantar digital nerves, is the peripheral nerve distribution of nociceptic root of pain.

So for example if the clinical picture suggests multiple etiology including plantar digital neuritis of 3rd inter-metatarsal space and injecting that space has no effect on present ambulatory pain you should consider that as useful evidence to relegate that idea. If it has partial effect you might consider that it is contributory and if resolving problem then highly probable as root of problem. The difficulty with this, as Craig mentioned, is that all nociception distal to nerve block will be affected. If MTP pathology is suspected then the joint should be injected first since this will localize diagnosis to joint nociceptors including the plantar plate. Another confounding issue is the nerve distribution to plantar fibro-fatty pad, which is likely variable in the population. I find with some individuals a single inter-metatarsal space block will eliminate pain without causing anaesthesia to plantar foot or toes. Other than placebo this is best explained by likelihood of intercommunication between plantar metatarsal nerves and possibly variable acuity for pain where there is crossover in distal nerve fibres. These factors must be interpreted in context.

To diagnose a so called “Morton’s neuroma” from a inter-metatarsal space injection is questionable. However if clinical signs and imaging suggest space filling plantar digital neuritis as possible you can test that idea if it remains ambiguous particularly if suspecting multiple etiologies fro metatarsalgia. This is particularly important if both 2nd and 3rd spaces are suspected and you want to test if pain is associated with either or both before corticosteroid injection or surgery.

I am curious; why you would use lidocaine therapeutically?

hope that helps

Cheers

Martin

Foot and Ankle Clinic
1365 Grant Ave.
Winnipeg Manitoba R3M 1Z8
phone [204] 837 FOOT (3668)
fax [204] 774 9918
www.winnipegfootclinic.com

 

Are podiatrists in NZ allowed to inject LA into inter-metatarsal space for the purpose of diagnosing Mortons Neuroma?

It's a good question.

What does it mean that you are allowed to inject LA?

Can you only inject it in those sites and for the specific conditions you have been taught. In britain this usually meant for nail surgery. Therefore student think/thought that its use was confined to nail surgery.

I don't think that the parameters of the use of LA are clear either in Britain, Newzealand or in Australia.

When can you use LA?

How many podiatrists use LA for the management of anything other than Nail surgery?

How many use it for the debridement of neurovascular corns or in the management of chilblains for example?

Bill