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Monoarthritis case study. Would you do a SFA and if so what?

Discussion in 'General Issues and Discussion Forum' started by Mart, Dec 8, 2010.

  1. Mart

    Mart Well-Known Member

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    I want to canvass opinion regarding suitable approach for patients presenting with newly diagnosed foot monoarthritis.
    Case in point was 50 YO lady I saw this morning.
    Some questions about this case;
    What investigations would you do for this lady and why?
    Would you do a SFA and if so what?
    If not why not?
    Do you do in office SFA?
    If not; how do you transport what will likely be a few drops of SF to lab for SFA

    Case history and PE.
    She was referred by primary care physician for undiagnosed metatarsalgia – 5 years duration gradual onset and worsened recently, no prior workup. She reported being in good general health, no other joint pain, denied recollection of a traumatic event or foot surgery, denied rest pain, no weight-bearing pain on rising from bed in morning, pain worsened with increased activity, improved with rest, VAS 4: (visual analogue pain scale range 0-10; moderate pain which interferes with tasks). Episodic radiating pain into 2nd toe. No suspicion for reactive arthritis or TB.

    PE; no signs of swelling, erythema, heat or skin lesions, tenderness to palpation at dorsal 2nd metatarso-phalangeal joint margins and generally at 2nd and 3rd metatarsal heads, Provocative testing with double limb stance heel raise resulted in plantar 2nd metatarsal head pain. She had hallux valgus, no hallux limitus, attenuated plantar plate stiffness of lesser digits, reducible flexible flexion deformity of all lesser toes, no pain or crepitation with passive dorsiflexion or plantarflexion of metatarso-phalangeal joints or active resistance of toe flexors.

    Diagnostic ultrasound exam was significant for slightly inhomogeneous 2nd metatarso-phalangeal joint effusion and very hyperintense signal with power Doppler imaging within synovial envelope. No evidence of “Mortons neurona” but evidence of inter-metatarsal space bursa enlargement adjacent to plantar digital nerve. 2nd and 3rd plantar plates were mildly degenerated at proximal phalanx. There was evidence of a double contour sign at 2nd metatarso-phalangeal joint (a “double contour” is the US sign associated with intercritical or acute gout. It is an extra hyperechoic line representing a visible surface layer of MSU crystals in addition to the normal single hyperechoic subchondral contour). Plantar fibro-fatty pad @ metatarsal heads was unremarkable for edema and no signal with power Doppler imaging.

    My ranked differential diagnosis was one or more of;
    Inflammatory osteo-arthritis 2nd metatarso-phalangeal joint
    Crystal deposition disease (US evidence of intercrititical gout)
    Plantar digital neuritis.
    plantar fibro-fatty pad overload
    plantar plate defect
    early rheumatoid or sero neg arthritis
    haematogenous septic arthritis.
    So my immediate problem is the monoarthritis. I believe it is perhaps only pain generator but may be layered on top of prior chronic injury
    It is impossible to know how long this has been present and there was no prior radiographic exam.
    Her joint effusion warrants an arthrocentesis, this may show MSU.
    The literature without exception rightly states that presence of MSU in synovial fluid (SF) doesn’t rule out septic arthritis (SA).
    So therefore it is implied that SFA with WBC and possibly culture if WBC is elevated (which would be with gout) should be approach.
    I have done medical literature search to find incidence of haematogenous SA in adult foot joints and could find no data published. I have never knowingly seen this or heard anecdotes for this scenario.
    I have ordered radiographic exam, and serum uric acid which will have limited value given clinical presentation – more importantly an athrocentesis with SFA for crystals next week or immediately if clinical signs for SA ensue.

    The St. James Foot Clinic
    1749 Portage Ave.
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918

  2. Griff

    Griff Moderator



    Given the multi-national audience you may want to confirm your abbreviations


  3. Mart

    Mart Well-Known Member

    Sorry Ian, I thought I had defined these with the text

    SFA synovial fluid analysis
    MSU monosodium urate (crystals)


  4. Griff

    Griff Moderator

    Ah that makes more sense, MSU means mid-stream urine where I come from... :eek:

    Cheers mate

  5. David Smith

    David Smith Well-Known Member


    Does this attached document help?


    Attached Files:

  6. Mart

    Mart Well-Known Member

    Hi David
    Thanks for posting the paper; I think that Chokkalingham et al reiterate most of what I have read and understand about acute monoarthritis.

    The issues I am concerned about are these:

    Most chronic metatarsalgia associated with joint effusions which I see in my practice are explained by osteo-arthritis which is often inflammatory; demonstrating synovitis with diagnostic ultrasound exam (US). This is obvious because of clinical presentation but often not suspected without US because the sensitivity of physical examination of small foot joints for joint effusion is low.

    Quite often optimising foot mechanics with foot-wear and foot orthoses is inadequate and pain control is successful then only with intra-articular corticosteroid injection.

    I have yet to find any statement in the medical literature which doesn’t categorically state that joint effusion “deserves” SFA. This is because of need to rule out non OA inflammatory arthritis.

    Also if SF has elevated WBC and/or crystals I have yet to find any statement in the medical literature which doesn’t categorically state that culture is needed to rule out SA.

    I have come across a couple of cases of undiagnosed gout in 1st and 2nd metatarso-phalangeal joints. There were no expected clinical signs of redness and heat. There was evidence of a double contour sign, inhomogeneous joint effusion and signal with power Doppler imaging with diagnostic ultrasound exam. They were +ve for SFA MSU. They did not get WBC or culture because there is no community testing arrangement for this locally.

    Recently I have initiated an attempt to get access to hospital based SFA testing which as far as I can tell is only route here for this investigation.
    I may need to present an argument to justify this and I want to “pick the collective mind” of podarena to see what happens elsewhere and also test the strength of my argument.

    It seems that the advice, which is unequivocal in the medical literature, is largely ignored in practise.

    I have yet to find a patient with acute non ankle foot monoarthritis which turned out to be gout actually get an arthrocentesis except if I do it and check for crystals myself. Always a serum uric acid is ordered by primary care physician if gout is suspected and this is often confusing.

    Perhaps there are a couple of bits of basic research which need to be done to improve the algorithm which Chokkalingham et al used.

    An important question might be

    What is the incidence of haematogenous SA in the adult mid tarsal or forefoot joints? I did a literature review recently looking at papers which classified sites of SA, non included foot joints other than ankle. It was impossible to explore that question from meta-analysis.

    I suspect the incidence is extremely low, perhaps zero but that the question has not been investigated.
    If this proves to be true is there then need to perform a culture if there are no acute signs of SA and no history of local wound even if crystals are present and/or WBC is elevated in a non ankle foot joint?

    I would argue no.

    However, until we can answer those questions it seems that as Chokkalingham et al state:

    with elevated SFA WBC regard as septic arthritis until proven otherwise
    i.e. we need SFA culture.



    The St. James Foot Clinic
    1749 Portage Ave.
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918

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