Osteomyelitis: Keys To Diagnosis And Treatment
- Volume 25 - Issue 12 - December 2012
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It is therefore important to evaluate MRI studies carefully for subtle differences that can lead to a correct diagnosis. Infection is favored as the diagnosis if bone marrow edema is localized within one specific area or bone. Underlying sinus tracts, subchondral cysts, diffuse bone marrow abnormalities or erosions of the bone will also support a diagnosis of bone infection. Osteomyelitis and Charcot neuroarthropathy will demonstrate hypointense signal intensity of bone marrow with T1-weighted images and hyperintense signal intensity with T2-weighted images. When bone edema concentrates to articular surfaces and edema spans multiple joints, Charcot neuroarthropathy is the more likely diagnosis.
Fluorodeoxyglucose (FDG) positron emission tomography (PET) scanning. Although FDG-PET would not be a typical study for evaluation of a simple case of osteomyelitis, the test does offer some distinct advantages when attempting to differentiate osteomyelitis from Charcot neuroarthropathy. The FDG-PET has the ability to differentiate these diagnoses on the basis of glucose metabolism. Infection results in higher glucose uptake. Charcot disturbances typically have standardized uptake values of approximately 2 or lower whereas bone infection will result in much higher standardized uptake values in the range of 3 to 7. The FDG-PET scans produce focal, distinct areas of uptake in the individual with osteomyelitis and more diffuse uptake in an individual with Charcot neuroarthropathy.28
One can reliably evaluate patients with metal implants with FDG-PET without complicating artifacts to obscure views, as one would see with MRI. At least one study has found ring PET to be more reliable than hybrid (dual head gamma camera) PET in at least one study since the resolution of ring PET scans is higher than hybrid PET scans.27,28 Ring FDG-PET offers a higher sensitivity and specificity in differentiating Charcot foot from infection in comparison to MRI results.27,28
Physicians rarely utilize FDG-PET clinically, although the benefits are arguable in rare situations. A significant limitation of this imaging modality is its expense, which can range from $2,000 to $8,000 depending on the institution. Ionizing radiation exposure and limited availability of this technology outside of a tertiary care setting are also limitations that can preclude its routine use. Time will tell if this diagnostic modality’s usage will increase. With improvements in practitioner awareness, cost effectiveness and accessibility, its future utility may be invaluable.
What The Research Reveals About Antibiotic Beads And Polylactic Acid Microspheres
One can often treat acute hematogenous osteomyelitis with antibiotics alone. Chronic osteomyelitis traditionally requires irrigation and debridement of necrotic, infected tissue and bone. Adequate surgical debridement can result in large areas devoid of bone. Drug eluting antibiotic beads can fill in these voids.
One of the most commonly utilized materials for antibiotic beads is polymethylmethacrylate (PMMA). One of the disadvantages to using PMMA is that a second surgery is always necessary to remove the beads as they are not absorbable in vivo. Pharmacokinetic profiles of PMMA beads are not ideal as the maximal elution is on day one with a subsequent drop occurring over the following three to four weeks. At this time, insufficient concentrations occur locally. Some evidence exists to support the usage of vancomycin and clindamycin with PMMA beads as levels continue to remain above minimal inhibitory concentration (MIC) at 28 days.29,30 Benefits to these beads include an absence of drainage from the surgical site.