Neuropathic Joint and Osteomyelitis in Diabetes

Michele Murray, M.D.

James Stevan Nagel, M.D.

10/24/89

Case Presentation:

A 72 year-old male presented with a long standing history of diabetes and clinical suspicion of osteomyelitis of the right great toe.

Findings:

A three-phase Tc-99m bone scintigram was performed and showed increased blood flow to the right great toe on flow images and increased activity in the right great toe, right lateral foot, left great toe, left lateral foot and left midfoot on delayed images (plantar, right medial, left lateral). Subsequent Gallium-67 imaging showed hyperintense uptake in the right great toe consistent with osteomyelitis (plantar, right medial). There was also less intense but increased uptake in the left midfoot. Plain radiographs of the right foot showed no radiographic evidence of osteomyelitis. Plain radiographs of the left foot showed bone destruction and fracture fragmentation of the left tarsal bones (arrow) consistent with a neuropathic joint (diabetic osteodystrophy). As this patient was going to receive systemic antibiotics for the osteomyelitis of his right toe, differentiating septic from nonseptic osteoarthropathy in the left midfoot was not necessary. However, this question is often raised in diabetic patients with osteodystrophy.

Discussion

Diabetes mellitus can present physicians with difficulty in differentiating cellulitis, osteomyelitis, and osteoarthropathy. All of these most often involve the lower extremities and osteoarthropathy can cause a warm and swollen extremity even without concomittant infection. Plain radiographs of osteomyelitis may show destructive changes, osteosclerosis, periosteal new bone formation, and even occasionally fracture. Plain radiographs of osteoarthropathy may demonstrate subluxation, fracture fragmentation, subchrondral osteoporosis, sclerosis in adjacent bone, and periosteal new bone formation. Differentiating the two radiographically can be difficult.

Bone scintigraphy is quite sensitive to bone pathology, but not very specific as it can be positive with fracture, primary and metastatic neoplasms, heterotopic ossification, arthritis, osteomyelitis, and osteoarthropathy.

Gallium-67 imaging localizes in inflammatory lesions and can add diagnostic specificity. Its intense concentration is thought to indicate osteomyelitis. It may show mildly increased uptake in nonseptic diabetic osteoarthropathy, but has been reported by Glynn to occasionally show marked accumulation adding further confusion to a difficult problem.

Indium-111 labeled white blood cells have been found to be very specific for acute osteomyelitis and have been found to be quite helpful in the differentiation of nonseptic from septic osteoarthropathy in diabetic patients.

Maurer, et al performed a retrospective study of thirteen diabetic patients in whom Indium-111 leukocyte studies were performed for possible osteomyelitis. The patients also had radiographic evidence of osteoarthropathy. Three-phase scintigraphy was performed in all patients and showed increased uptake in both septic and nonseptic osteoarthropathy with a sensitivity of 75% and a specificity of 56% for osteomyelitis. Leukocyte imaging had the same sensitivity but was most helpful for excluding infection with a specificity of 89%.

Schauwecker, et al studied the use of bone imaging, leukocyte imaging, and gallium imaging in the setting of suspected osteomyelitis superimposed upon other diseases causing increased bone turnover. In-111 leukocyte imaging had a sensitivity of 100% in acute osteomyelitis and 60% in chronic osteomyelitis with a specificity of 95%. Gallium-67 was excellent for ruling out osteomyelitis when it was a normal study or ruling it in when it showed hyperintense uptake compared with bone imaging or had a different distribution from the bone images. This situation occurred in 28% of the patients studied.

Splittgerber, et al. studied six diabetic patients with radiographic findings of osteomyelitis, osteoarthropathy or both using leukocyte and bone imaging. Three patients actually had osteomyelitis. Bone images showed increased uptake in all six patients studied while leukocyte imaging showed increased uptake only in the three patients with osteomyelitis.

In conclusion, Indium-111 labeled leukocyte imaging may add further specificity in differentiating septic from nonseptic diabetic osteoarthropathy in patients with increased uptake shown on bone and/or gallium images.

References:

1) Clouse ME, et al. Diabetic osteoarthropathy. Clinical and roentgenographic observations in 90 cases. AJR 1974; 121(1):22-34.

2) Glynn TP. Marked gallium accumulation in neurogenic arthropathy. J Nucl Med. 1981; 22(11):1016-7.

3) Splittgerber GF, et al. Combined leukocyte and bone imaging used to evaluate diabetic osteoarthropathy and osteomyelitis. Clin Nucl Med. 1989; 14(3):156-60.

4) Schauwecker DS, et al. Evaluation of complicating osteomyelitis with Tc-99m MDP, In-111 granulocytes, and Ga-67 citrates. J Nucl Med. 1984; 25:849-53.

5) Maurer AH, et al. Infection in diabetic osteoarthropathy: Use of indium-labeled leukocytes for diagnosis. Radiology 161:221-225.

________________________________________________________

J. Anthony Parker, MD PhD, jap@nucmed.bih.harvard.edu