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Diagnostic ultrasound exam of inter-metatarsal space

Discussion in 'General Issues and Discussion Forum' started by Mart, Feb 4, 2008.

  1. Mart

    Mart Well-Known Member


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    I recently had a case of MRI confirmed inter-metatarsal neuroma 2/3 inter-metatarsal space which I missed with Diagnostic ultrasound exam.

    Studies show good sensitivity for neuroma with US and this suggests my skills need improvement.

    The patient had no mulder sign and symptoms were not usual for neuroma.

    I find this US exam difficult, the echodensity of the inter-metatarsal space is murky, I have seen a couple of cases which I regarded as well defined US suspicious for neuroma but I still lack confidence.

    I am curious about the idea of careful infiltration of 1% lidocaine around the nerve with the intention of creating fluid engorged fatty tissue around the neurovascular bundle and creating better definition of any fibrous tissue which may be present.

    I have been unable to find anything in the literature about this.

    My questions are

    Anyone tried doing this, if so how did it work?

    Anyone have any thoughts about if this is likely to work. Would it be reasonable to expect infiltration of lidocaine to create a “halo” around the NV bundle or would it more likely diffuse evenly acroos the entire volume?

    Cheers


    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    Phone [204] 837 FOOT (3668)
    Fax [204] 774 9918
    www.winnipegfootclinic.com
     
  2. Admin2

    Admin2 Administrator Staff Member

  3. drsarbes

    drsarbes Well-Known Member

    Mart:
    Please don't take this the wrong way...........but an MRI for Morton's Neuroma???

    I think a Morton's neuroma should be rather easily Diagnosed by a specialist (or astute Primary care) via clinical examination (and History of course)

    MRI's for these is a case of over utilization.
    Perhaps we get away from a thorough exam because we have this technology to fall back on!

    My take is.......if you have to look THAT hard to find a Neuroma it's most likely not the underlying cause of the patient's symptoms.

    Steve
     
  4. Mart

    Mart Well-Known Member



    Steve

    You raise an important point which also occurred to me, and have not taken this “the wrong way” ;)


    I spoke to the Orthopedic Surgeon today who ordered the MRI to get his broader impressions of this case and his clinical reasoning.

    I questioned the finding somewhat given unusual site (2/3 IMS), lack of mulders sign, no radiating digital symptoms, no provaction of pain in any way with 2nd or 3rd MPJ motion but also felt somewhat defensive given that I had missed a positive US finding.


    Anyhow ,we had a rather turse conversation, he told me that the MRI showed 7mm dia neuroma at 2/3 IS and would likely need surgery.

    Pt has fairly severe subluxation of lesser MPJs, elevated PPs and FTIs under MTH 2 and 3 bilateraly and is starting to develop similar symptoms on contralat side. US shows PPlate in tact but thickened.

    All points to mechanical overload, which has been significantly reduced but not elliminted with offloading FO.

    So I tend to agree with you – however my concern regarding improving US reliability is still on my mind.

    Cheers

    Martin


    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    Phone [204] 837 FOOT (3668)
    Fax [204] 774 9918
    www.winnipegfootclinic.com
     

  5. Mart:

    First of all, I wouldn't trust most orthopedic surgeons to be able to accurately diagnose intermetatarsal neuromas. Secondly, I wouldn't trust an MRI scan to be able to be accurate 100% of the time since MRIs are often wrong. Since I don't use ultrasound, you probably know better than I do about its accuracy in detecting neuromas.

    I agree with Steve, an intermetatarsal neuroma should be a clinical diagnosis without the need for ultrasound or MRI. An intermetatarsal neuroma should be directly palpable or detected via the "Mulder's sign" in skilled hands. They will generally cause a decrease in sharp/dull sensation in the affected plantar interdigital space, patients will report the pain as being anything from aching, to burning, to tingling and patients often find relief wearing looser shoes or being barefoot. Patients often report that rubbing the foot with the neuroma makes the pain better. Intermetatarsal neuroma must be differentiated from injury or inflammation of the metatarsophalangeal joint and from the transient neuritis that is often caused by localized edema about a plantar plate tear that seems to be related to irritation of the adjacent plantar nerve from the inflammatory process within the metatarsophalangeal joint.

    In addition, in my experience, here in the States, most pathologists will call any interdigital nerve removed by a foot surgeon a "neuroma", regardless of whether it looks like a neuroma or not under the microscope. Surgeons don't like being told by anyone that they surgically excised a perfectly normal nerve from a patient that they believed to have a "neuroma".
     
  6. Mart

    Mart Well-Known Member

    Thanks for input Kevin.

    This has been one of my problem cases over period of approx 2yrs. I find Tx of metatarsalgia sometimes difficult and this has been one of them.

    If I am unsuccessful treating what I regard as mechanical problem with basic common sense approach guided by HX , S&S and P/E then I will start challenging my assumptions from my toy shop. I can report this pays off sometimes but still leaves me scratching my head at others.

    I get the impression that problem cases of overload are often from multiple causes and improvement may also require lessening of a cause of compensation rather than a primary target, a very tricky thing to identify from P/E, and to be sure of even if it seems to be consistent with several bits of evidence.

    This is more of a hunch then I would really like.

    I guess that’s what can make our work interesting . . . . . . but little consolation for the patient.

    Will post an outcome if anything worthwhile happens

    Cheers

    Martin




    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    Phone [204] 837 FOOT (3668)
    Fax [204] 774 9918
     
  7. drsarbes

    drsarbes Well-Known Member

    Gentlemen......and there you have it. Like I always said "to a man with a hammer everything looks like a nail" - If you perform surgery for a living you can usually find a reason for getting out the 10 blade!

    I don't want to belittle your Orthopedic colleague, most are very well trained and do a very good job. BUT (big but here) I cannot for the life of me account for the change in the level of care when it comes to the foot. I realize this wasn't the original topic here, but it may play a role in this case.

    The normal standards for medical and surgical decision making seem to go out the window when it's a foot. For instance, do you think an Orthopedic Surgeon would open a wrist or shoulder based only on a possibly insignificant MRI finding - especially if it was not collaborated by clinical evidence? Absolutely not.

    My other take on this entire case is the fact that it is most likely repeated thousands of times across the country. A chief complaint that probably should have been adequately diagnosed and treated via good history and clinical examination and classic decision making. Instead, an MRI is used as the safety net
    under poor clinical skills and possibly a wrong diagnosis and unnecessary surgery is performed.

    If feel better for having gotten THAT of my chest!

    Steve
     
  8. Amen to that, Brother Steve!......:good:
     
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