When is advanced imaging necessary for guiding one’s decision-making on the treatment of a lower-extremity wound? How reliable are radiographs when clinicians suspect osteomyelitis? Should you employ magnetic resonance imaging? Does nuclear medicine imaging have particular value in managing wounds? Our expert panelists tackle these questions and more in the following discussion.
Q: What role do you see advanced imaging playing in the management of foot and ankle wounds?
A: Molly Judge, DPM, says advanced imaging is unnecessary when it comes to clean, uncomplicated wounds that have a clear chance of resolving with local wound care. Lawrence Ford, DPM, concurs, noting it is limited to difficult cases in which clinical findings and standard X-rays are inconclusive.
However, when patients have longstanding wounds (with or without a history of infection), Dr. Judge says it is “prudent to pursue some form of imaging” in order to confirm the absence of an underlying pathology that can confound the existing clinical condition.
When local ulcerations fester long enough, Dr. Judge says these patients are at risk for a secondary bacterial infection, which can result in deep sinus formation, abscess and possibly osteomyelitis.
“These are the complicating conditions that mandate advanced imaging to delineate the location and extent of infection,” emphasizes Dr. Judge. “This imaging will ultimately lend credence to the proposed wound care plan or prompt a change in the treatment plan altogether.”
According to Thomas Zgonis, DPM, there are a variety of imaging techniques one can use to help confirm osteomyelitis. These imaging techniques include plain radiographs, nuclear imaging, magnetic resonance imaging (MRI), computerized tomography (CT) and diagnostic ultrasound. However, Dr. Zgonis cautions that each test has its limitations and one must carefully assess the patient’s comorbidities before ordering expensive and possibly unnecessary tests.
When it comes to diagnosing osteomyelitis, in addition to the clinical assessment, Dr. Zgonis says one may need an imaging study to confirm and further assess the extent of deep soft tissue and bone involvement. However, he says the bone biopsy remains the gold standard for a definitive diagnosis of osteomyelitis. If the results from imaging are inconclusive, Dr. Zgonis says one should obtain sterile bone cultures if one has a high index of suspicion for underlying osteomyelitis. He adds that histopathologic analysis is necessary to confirm the diagnosis of osteomyelitis.
Q: If a chronic wound “probes to bone” but has normal X-ray findings, how do you treat this?
A: Citing a study by Grayson, et. al., Dr. Zgonis says the ability to probe to bone in the base of an infected pedal ulcer with a sterile blunt steel probe had a positive predictive value of 89 percent and a negative predictive value of 56 percent for osteomyelitis.1 He notes the researchers also concluded that if one palpates bone upon probing, specialized roentgenographic and radionuclide tests are unnecessary in diagnosing osteomyelitis.1
Dr. Zgonis says one should employ this test in the assessment of all acute and chronic foot ulcers that appear infected. He adds that this test may “obviate further advanced imaging to confirm the diagnosis of osteomyelitis.” Probing to bone and the presence of clinical and systemic signs of infection are “still the most reliable indicators of underlying osteomyelitis,” according to Dr. Zgonis.