Osteomyelitis: Making the Diagnosis

Osteomyelitis – Making the Diagnosis

By Ben Cooper MD
Chief Resident, UTSW / Parkland Memorial Hospital

Edited by Alex Koyfman MD (@EMHighAK) and Stephen Alerhand MD

Patient Case

A 55 year-old male with diabetes status-post left trans-metatarsal foot amputation presents to the ED with a 3-week history of a progressive foot ulcer. He has lost feeling to his lower extremities, but denies purulent drainage from the wound. There have been no systemic symptoms. His vitals are all within normal limits, and physical exam reveals a 3 cm diameter ulcer overlying the prior amputation site. A plain film is obtained and shown below.

osteo xray

The x-ray is read as no focal demineralization to suggest osteomyelitis. Laboratory results reveal an ESR of 81, CRP 5, and WBC 8K. The patient was admitted for concern for osteomyelitis, which a subsequent MRI study confirmed. The patient was started on Doxycycline and Augmentin, then instructed to continue taking these antibiotics for 6 weeks with regular podiatry appointments. Ultimately, the patient had a femoral-femoral bypass and continues to struggle with serial infections.

Background

This is an all-too familiar scenario in patients with diabetic foot ulcers. Lack of sensation and poor vascularity creates a nice culture agar, and osteomyelitis seems imminent. This article will explore the tools that the Emergency Physician has to make the diagnosis and potentially save a limb.

In the patient population at Parkland, osteomyelitis (OM) usually results from direct extension of adjacent soft tissues (i.e. diabetic foot ulcers, or sacral decubitus ulcers), but can also result from hematogenous spread or direct inoculation as a result of trauma or surgery. Given the lack of sensitive physical exam findings, and the unavailability of time-consuming imaging modalities in the ED (magnetic resonance and/or bone scintigraphy), OM can be a difficult and sometimes elusive diagnosis to make in the ED setting.

foot ulcer

Physical Exam

The physical exam is of somewhat limited value versus expected when evaluating patients with suspected OM. Probing to bone of diabetic foot ulcers has been found to have a sensitivity of 66%, and a specificity of 85% in a prospective study of 76 cases (1). An ulcer area larger than 2 cm2 makes OM more likely (LR 7.2), while an ulcer less than 2 cm2 makes it less likely (LR 0.48). The presence or absence of inflammatory signs such as erythema, edema, or purulence does not contribute to the probability of disease (10). All of these findings can aid the provider in making the diagnosis, but none have sufficient sensitivity to rule out disease.

Stage 1Stage 2

Stage 3Stage 4

(http://www.aotinc.net/aoti_diabetic_ulcer.html)

Imaging/Labs

With the limitations of physical exam in OM, plain film imaging and serum inflammatory markers are commonly obtained to aid the diagnosis. Findings suggestive of OM on radiography include cortical erosion, periosteal reaction, mixed lucency, and sclerosis. These signs may not be evident for up to 2 weeks into the infection (2). Sensitivity of plain radiographs (XR) has been reported between 43%-75% (2-5) for OM due to diabetic foot ulcers, but may be much less for other areas of OM (6).

Inflammatory markers including WBC, ESR, and CRP are routinely obtained for the evaluation of suspected OM. A review of the literature (for OM due to contiguous foot/ankle ulcers) found three studies that reported the sensitivity of ESR between 68-90% for varying cut-off values between 60 and 70 mm/hr, two that reported the sensitivity of CRP as 85% for cut-off values of 1.4 and 3.2 mg/dL, and two that reported the sensitivity of WBC as 41% and 75% for cut-off values of 11K and 14K, respectively (7-9). The largest of these studies included 34 patients with confirmed OM.

The sensitivity of MRI has been reported from 82 to 100%, and this is the diagnostic modality of choice (2) unless bone cultures can be obtained expeditiously – the gold standard. Typically, this is not something available in the ED for this diagnosis, and admission would be warranted.

Management

If the provider’s suspicion of OM is high, antibiotics are often initiated immediately in the ED prior to obtaining bone and/or wound cultures. Blood cultures are frequently obtained prior to the initiation of antibiotics despite low yields (11). If the patient is stable and does not meet criteria for sepsis, the provider should consider delaying antibiotics until obtaining wound and/or bone cultures.

Despite attempted conservative approaches to management of OM (i.e. antibiotics, surgical debridement), ultimate treatment often involves amputation. If antibiotics are initiated in the ED, consider coverage for MRSA, coagulase-negative staphylococci, and gram negatives (including pseudomonas). A typical regimen may be Vancomycin + Ciprofloxacin, and treatment is likely to span several weeks.

Summary

In summary, osteomyelitis is a difficult diagnosis to make. Certainly there are specific tests – i.e. probing to bone, findings on x-ray in the right clinical setting – but no test is sensitive enough to rule out. Inflammatory markers can again aid in raising suspicion, but are insensitive to rule out. Keep a high index of suspicion, and either admit for MRI, or secure good follow-up for patients with diabetic foot ulcers that present acutely or subacutely.

 

References / Further Reading:

  1. Grayson ML, Gibbons GW, Balogh K, Levin E, Karchmer AW. Probing to bone in infected pedal ulcers. A clinical sign of underlying OM in diabetic patients. JAMA. 1995;273(9):721.
  2. Pineda C, Espinosa R, Pena A. Radiographic imaging in OM: the role of plain radiography, computed tomography, ultrasonography, magnetic resonance imaging, and scintigraphy. Semin Plast Surg. 2009; 23(2): 80-89.
  3. Shults DW,Hunter GCMcIntyre KEParent FNPiotrowski JJBernhard VM. Value of radiographs and bone scans in determining the need for therapy in diabetic patients with foot ulcers. Am J Surg. 1989 Dec;158(6):525-9.
  4. Yuh WT,Corson JDBaraniewski HMRezai KShamma ARKathol MHSato Yel-Khoury GYHawes DRPlatz CE, et al. OM of the foot in diabetic patients: evaluation with plain film, 99mTc-MDP bone scintigraphy, and MR imaging. AJR Am J Roentgenol. 1989 Apr;152(4):795-800.
  5. Larcos G, Brown ML, Sutton RT. Diagnosis of OM of the foot in diabetic patients: value of 111 In-leukocyte scintigraphy. AJR Am J Roentgenol 1991;157: 527–31.
  6. Tumeh SS, Aliabadi P, Weissman BN, McNeil BJ. Disease activity in OM: role of radiography. Radiology. 1987;165(3):781.
  7. Michail M, Jude E, Liaskos C, Karamagiolis S, Makrilakis K, Dimitroulis D, Michail O, Tentolouris N. The performance of serum inflammatory markers for the diagnosis and follow-up of patients with OM. Int J Low Extrem Wounds. 2013 Jun;12(2):94-9. doi: 10.1177/1534734613486152. Epub 2013 May 9.
  8. Fleischer AE, Didyk AA, Woods JB, Burns SE, Wrobel JS, Armstrong DG. Combined clinical and laboratory testing improves diagnostic accuracy for OM in the diabetic foot. J. Foot Ankle Surg. 2009; 48 (1): 39–46.
  9. Kaleta JL, Fleischli JW, Reilly CH. The diagnosis of OM in diabetes using erythrocyte sedimentation rate: a pilot study. J. Am. Podiatr. Med. Assoc. 2001; 91: 445–50.
  10. Butalia B, et al. Does this Patient with Diabetes Have Osteomyelitis of the Lower Extremity? JAMA. 2008; 299(7):806-13.
  11. http://www.acepnow.com/article/blood-culture-testing-send-samples-selectively-lower-costs-medico-legal-risk/
  12. http://www.ncbi.nlm.nih.gov/pubmed/22224154
  13. http://www.ncbi.nlm.nih.gov/pubmed/19380041
  14. http://www.ncbi.nlm.nih.gov/pubmed/12563584

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FFP Vs. PCCs for Warfarin Reversal – Special Advertising Supplement

It is generally well-known, the advantages of Prothrombin Concentrate Complexes over Fresh Frozen Plasma.  They are a smaller-volume infusion, more rapidly reverse the anticoagulant effect, and lack some of other disadvantages of hemostatic product use.  This study, therefore, a Phase 3b open-label trial of PCCs vs. FFP for anticoagulation reversal before urgent surgery, is essentially of questionable utility.  Is it emergency surgery?  Then use the immediate reversal agent.  Is it semi-elective?  Well, why not wait a bit?

So, why even run a trial for the use of PCCs in the non-emergent realm?  Well, it rapidly becomes clear how this study was conceived by review of the “Role of the funding source”:
This research was funded by CSL Behring. A steering committee of academic medical experts and representatives of the funder oversaw the design and conduct of the study. The funder participated in the selection of the board members. The funder was responsible for data collection, management, and analysis of the data according to a predefined statistical analysis plan. Preparation and review of the Article and the decision to submit for publication was done by a publication steering committee that included academic medical experts and representatives of the funder. Medical writing assistance was paid for by the funder. JNG and RS had full access to all the data in the study and took responsibility for the integrity and accuracy of the data analysis.
The goal: “indication creep” – an entirely obvious corporate landgrab, essentially sponsored, conducted, and written by CSL Behring to expand the use of PCCs beyond emergency reversal.  Indeed, it’s hard to even dignify this Lancet content with a summary.  The exclusion criteria were extensive.  The trial was modified after a letter from the FDA.  Some of the reported outcome numbers in the paper don’t match their ClinicalTrials.gov entry.  Almost all the differences in outcomes were subjective or surrogates for patient-oriented measures.  The authors conclusion:
“[T]hese data show that 4F-PCC is an effective and superior alternative to plasma in terms of haemostatic efficacy and rapid INR reduction for the rapid reversal of VKA therapy before urgent procedures.”
But, despite all these differences “favoring” PCCs, the surgical hemostasis was identical in practical terms – the difference in blood loss between cohorts was only 12 mL on average, only a handful of patients in each cohort required any sort of transfusion, and the total number of units transfused was nearly identical.  In fact, half of the FFP patients never had full INR reversal – with apparently no clinically important consequence.  Surgical cases went to the OR much faster with PCCs – so, as above, in an emergent or semi-emergent instance, PCCs are a great option.  Absent such a rush, however, ignore this Special Advertising Supplement masquerading as science in a supposedly reputable journal.

“Four-factor prothrombin complex concentrate versus plasma for rapid vitamin K antagonist reversal in patients needing urgent surgical or invasive interventions: a phase 3b, open-label, non-inferiority, randomised trial”
http://www.ncbi.nlm.nih.gov/pubmed/25728933

#FOAMed Review 37th Edition

By Michael Macias

By Michael Macias

Welcome to the thirty-seventh edition of the #FOAMed Review! The idea of the FOAMed review is to give you a digestible selection of reliable content from the online EM/CC world that you can fit into your busy weekly schedule. Each review will include highlights from the highest yield blog, podcast, video and web sources around. Over a year's span we will be sure to include topics from all core EM content areas...even the ones that may not be the coolest. Check out our indexing section #FOAMED REVIEW which allows you to view previous weekly reviews by edition or by selecting from CORD curriculum categories.


Onto the FOAMed. 


HIGH FLOW NASAL CANNULA FOR APNEIC OXYGENATION [BLOG]: With new promising literature becoming available, Josh Farkas discusses the novel use of HFNC in respiratory failure. Pulm Crit 

THE FUTURE OF ULTRASOUND [PODCAST]: Must listen from SMACC 2014 about what to expect from ultrasound as it becomes more engrained in EM culture. This is the future! Ultrasound Podcast

THE CASE OF DUBIOUS SQUIRE [BLOG]: EM Nerd discusses the shortcomings of BNP and the fact that it may not add much to physician's clinical judgement. 

DIY: INTRANASAL ATOMIZER [VIDEO]: 

The SMACC evo competition is boasting some pretty amazing procedural videos! Check out the rest here, and hopefully we will see you at SMACC Chicago!


More FOAMed. 

CARDIOVASCULAR DISORDERS   

DELIRIUM & PHYSOSTIGMINE [BLOG]: Dr. Smith provides us with yet another great tox ECG case and some literature on the maybe not so deadly use of physostigmine. Dr. Smith's ECG Blog

PEDIATRICS 

PEDIATRIC SHOCK INDEX [BLOG]: The struggle is real for seeking out the sick kid in your ED. Sean Fox provides us with some pediatric pearls on clinical signs to be aware of in shock and the utility of the shock index. Pediatric EM Morsels 

NEUROLOGY

UNUSUAL STROKE PRESENTATIONS [BLOG]: Stroke presentation can be subtle, atypical and in fact only involve sensation (and all those patients you sent home with bilateral finger tingling). A nice review of the varied presentations of stroke to the ED hereEM Docs

EMERGENCY MEDICINE

WHAT YOU DO MATTERS [VIDEO]: First shown at EEM 2014, this video of remembering Hank Gathers, a start college basketball player who died from sudden cardiac death 25 years ago, is inspiring and definitely worth a watch. Hippo EM


See you next week.