Roundtable Insights On Imaging For Foot And Ankle Wounds

Volume 18 - Issue 5 - May 2005
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Other Key Points On Nuclear Medicine Leukocyte Imaging

When using nuclear medicine leukocyte imaging (NMLI), Molly Judge, DPM, says it is critical to use this imaging prior to any surgical manipulation of soft tissue, muscle, bone or joint.

Surgical manipulation distorts normal anatomic compartments, changes local anatomy and, most importantly, causes direct tissue damage that can mimic infection when using some NMLI techniques, according to Dr. Judge.

NMLI techniques such as 99mTc-HMPAO, combination imaging with 99mTc-MDP and Indium-labeled leukocytes and Neutrospec imaging are “all viable methods for pre-surgical assessment of chronic wounds.”

When treating noncompliant patients, Dr. Judge says NMLI can be particularly useful in ruling out indolent infection. Using NMLI can help document if there is no infection at the time of treatment, according to Dr. Judge. She adds that this can help counter any potential argument of misdiagnosis or delayed diagnosis in the event of limb loss despite the best of efforts.

She adds that the radiologist’s reading of NMLI is an important aspect of medical/legal documentation.

“If there is any unusual area of positivity in the extremity, there will be a caution in the radiologist’s report suggesting that this may represent an infectious process,” notes Dr. Judge.

When it comes to osteomyelitis (as shown above), there are a variety of imaging techniques one can use to help confirm the diagnosis, according to Thomas Zgonis, DPM. (Photo courtesy of Robert Snyder, DPM)

Here is a radiograph that reveals osteomyelitis. In regard to an initial radiolucency, Dr. Zgonis says underlying osteomyelitis requires five to seven days to manifest radiographically. (Photo courtesy of Lawrence Karlock, DPM)

This MRI STIR technique identifies the region of a loculated abscess formation that rests immediately beneath the remnant of cuboid bone. Note the intermedullary edema indicated by the increased signal intensity within the adjacent osseous structures of t

As one can see, the 99mTc-MDP study reveals the extent of degenerative bone in a “burned out” Charcot foot while the indium 24-hour image fails to reveal a focus of infection in that same patient with Charcot neuroarthropathy. (Photos courtesy of Molly Ju

Roundtable Insights On Imaging For Foot And Ankle Wounds

Author(s):

Clinical Editor: Lawrence Karlock, DPM

Additionally, if there is infection within the medullary component of bone, Dr. Judge notes the MRI can show a very extensive degree of this inflammatory change that is often far out of proportion to what one sees clinically. Dr. Judge explains that when any infection propagates into normal regions of bone, it causes an inflammatory front that shows the body has promoted a road block to the degenerative process.

“The problem here is that the MRI cannot distinguish between benign and infectious inflammatory change, and ultimately shows one large region of increased signal change that can overestimate the actual extent of pathology,” points out Dr. Judge.

Dr. Judge also notes that MRI is precluded in cases of retained foreign bodies such as stents, staples and internal fixation devices.

Dr. Karlock (pictured) is a Fellow of the American College of Foot and Ankle Surgeons, and practices in Austintown, Ohio. He is a member of the Editorial Advisory Board for WOUNDS, a Compendium of Clinical Research and Practice.

Dr. Ford is the Residency Director of the San Francisco Bay Area Foot and Ankle Residency Program at Kaiser Permanente in Richmond and Oakland, Ca. He is a Fellow of the American College of Foot and Ankle Surgeons.

Dr. Judge is a certified nuclear medicine technologist and is a Fellow of the American College of Foot and Ankle Surgeons. She is board-certified in foot, ankle and reconstructive rearfoot and ankle surgery by the American Board of Podiatric Surgery. Dr. Judge has private practices in Toledo and Port Clinton, Ohio. She is the official foot and ankle physician for the Jamie Farr Owens Corning LPGA Classic sponsored by Kroger.

Dr. Zgonis is an Assistant Professor within the Department of Orthopaedics/Podiatry Division at the University of Texas Health Science Center in San Antonio. He is an Adjunct Assistant Professor at the College of Podiatric Medicine and Surgery at Des Moines University in Des Moines, Iowa. Dr. Zgonis is also a Visiting Clinical Professor of Surgery within the Department of Orthopaedics and Traumatology at Thriasion General Hospital in Athens, Greece. He is an Associate of the American College of Foot and Ankle Surgeons.

References:

1. Grayson ML, Gibbons GW, Balogh K, Levin E, Karcmer AW. Probing to bone in infected pedal ulcers: A Clinical sign of underlying osteomyelitis in diabetic patients. JAMA 1995; 273:721-723.
2. Bonakdarpour A, Gaines VD. The radiology of osteomyelitis. Ortop Clin North Am 1983; 14:21.
3. Wheat J. Diagnostic strategies in osteomyelitis. Am J Med 1985;78:218-224.
4. Devillers A, Garin E, Polard JL, Poirier JY, Arvieux C, Girault S, et al. Comparison of Tc-99m-labelled antileukocyte fragment Fab' and Tc-99m-HMPAO leukocyte scintigraphy in the diagnosis of bone and joint infections: a prospective study. Nucl Med Commun 2000;2:747-53.
5. Larcos G, Bron ML, Sutton RT. Diagnosis of osteomyelitis of the foot in diabetic patients: value of 111 In-leukocyte scintigraphy. AJR 1991;157:527-531.
6. Zgonis T, Jolly GP, Buren BJ, Blume P. Diabetic foot infections and antibiotic therapy. Clin Podiatr Med Surg. 2003;20:655-69.