Commentary:    The diagnostic imaging of osteomyelitis (bone infection) can require the combination of diverse imaging techniques for an accurate diagnosis and clinical staging .(1)   Conventional radiography should always be the first imaging modality to start with, as it provides an overview of the anatomy and the pathologic conditions of the bone and soft tissues of the region of interest.  However, since the specificity of plain x-rays for detection is higher than its sensitivity, other, more reliable methods of imaging are necessary.(2 – 4)   Ultra-sonography is most useful in the diagnosis of fluid collections, periosteal involvement, and surrounding soft tissue abnormalities and may provide guidance for diagnostic or therapeutic aspiration, drainage and/or tissue biopsy. Computed tomography (CT) scans can be a useful method to detect early osseous erosion and to document the presence of sequestra, cloacae, foreign bodies, or gas formation; nevertheless, they are generally is less sensitive than other modalities for the detection of osteomyelitis.(3)   Magnetic resonance imaging (MRI) is the most sensitive and most specific imaging modality for the detection of infection in bone (Sens /Spec = 82%-100%/ 75%-95%), provides superb anatomic detail and gives more accurate information of the extent of the infectious process in bone and soft tissue.(3 -5)    Although nuclear medicine imaging (technetium-99 bone scans and Indium-111 white blood cell scans) is particularly sensitive in identifying multifocal osseous involvement, they are rather nonspecific.(6)   

Since no one study is able to definitively confirm the presence of absence of infection, cross-sectional imaging modalities such as CT and MR scanning are now considered the gold standard in diagnosing osteomyelitis, giving excellent anatomic delineation of the infected area and the surrounding soft tissue envelope.   In our protocols, all methods of used, selectively: (7) plain radiographs  to reveal internal hardware, axial alignment, fracture patterns and instability; nuclear scans  to correlate  cellular activity with radiographic change and assess for  poly-osseous disease;  CT scans to delineate sequestra, cloacae, bone volumes, and the extent of fracture healing (union vs non-union);  MRI and PET/CT scans to define the zone of injury/inflammation, disclose skip-lesions and highlight necrotic foci.   

Bibliography:  (1) Haas DW, McAndrew MP. Bacterial osteomyelitis in adults: evolving considerations in diagnosis and treatment. Am J Med, l996; 101:550-561.  (2)  Pineda C, Espinosa R, Pena A. Radiographic imaging in osteomyelitis: the role of plain radiography, computed tomography, ultrasonography, magnetic resonance imaging, and scintigraphy.   Semin Plast Surg, 2009 May; 23(2):80-9.  (3) Termaat MF, Raijmakers PG, Scholtein HJ et al. The accuracy of diagnostic imaging for the assessment of chronic osteomyelitis: a systemic review and meta-analysis. J Bone Joint Surg Am, 2005; 87:2464-2471.  (4) Mahnken AH, Bucker A, Adam G, Gunther RW. MRI of osteomyelitis: sensitivity and specificity of STIR sequences in comparison with contrast-enhanced T1 spin echo sequences. RöFo, 2000; 172” 1016-1019.  (5) Littenerg B, Mushlin AL. Technetium bone scanning in the diagnosis of osteomyelitis: a meta-analysis of test performance. J Gen Intern Med, l992; 7:158-163.  (6) Cierny III, G., Pennick, JJ, Mader, JT, A Clinical Staging System for Adult Osteomyelitis, J. Clinical Orthopaedics and Related Research, Number 414, pp 7-24, September 2003 .  (7)  Cierny G, DiPasquale D. Adult Osteomyelitis. Chapter 16 in Orthopaedic Knowledge Update : Musculoskeletal Infection. Amer. Acad. Orthop. Surg, Rosemont, IL, 2009. pp 135-155.

 6/22/2010:   The Hoka Hey Challenge (race) is on! 

Eric made it to the first check point in 25^th place.   He remains salty (the heat!) and unscathed, despite a 4-bike accident along the way.   They’re now in Mississippi, heading north —– hopefully out of that brutal heat.   GC

Article review:   Bhavan KP, Marschall J, Olsen MA, et al:  The Epidemiology of hematogenous vertebral osteomyelitis: a cohort study in a tertiary care hospital.  BMC Infectious Diseases, 2010: 10: 158doi: 10.1186/1471-2334-10-158  (Published 7-7-2010).

Dr. Cierny’s comments:  this article describes the epidemiology and early management of hematogenous vertebral osteomyelitis (anatomic types I and IV) in 70 patients over a 2-year period at Barnes Hospital in Missouri (a retrospective, cohort review).  A microbiological diagnosis was made in only two-thirds the cases.  S. aureus was the most common causative organism.

Results – The mean age was 59.7 years with 54% male. Predisposing factors included: B-hosts with diabetes (43%) or renal insufficiency (24%); in the 30 days prior to admission, an indwelling catheter (30%), bacteremia (19%) or skin/soft tissue infection (17%).  Back pain was the most common symptom (87%), followed by weakness (56%) and fever (46%); seven patients presented with paraplegia.  48% had a normal WBC but 95-98% had either an elevated ESR or CRP. 

The lumbar spine was the most common anatomic location (47%): thoracic (29%); cervical (24%).  Among the 46 (66%) patients with a microbiological diagnosis, the most common organisms were MSSA (33%) and MRSA (22%).  Among the 44 (63%) patients who had a diagnostic biopsy, open biopsy was more likely to result in pathogen recovery [14 (93%) of 15 with open biopsy vs. 14 (48%) of 29 with needle biopsy; p=0.003].   Surgery was required during the initial hospitalization in 23% of patients: decompression laminectomy 14%), laminectomy /fusion (7%) and corporectomy (1%).  Treatment outcomes were not included.