[Nonspecific osteomyelitis in childhood and adolescence. The contribution of imaging diagnosis].

Nonspecific osteomyelitis in children and adolescents can be diagnosed in patients 2 to 16 years old and may present as acute, subacute or chronic. During the last 9 years, 40 pediatric patients (aged 2 to 16 years) affected with extra-axial inflammatory bone lesions were examined. The series of cases was then reviewed. This work was aimed at investigating the role of various imaging modalities: conventional radiology (CR), bone scan with technetium-99 methylene diphosphonate (99mTc-MDP), scintigraphy with technetium-esamethylpropylenaminoxima labelled leukocytes (99mTc-HMPAO), computed tomography (CT) and magnetic resonance imaging (MRI) were used to detect the lesions, to make a differential diagnosis and to assess different disease stages. As for acute osteomyelitis (6 patients), CR showed a lytic lesion, periosteal new bone and soft tissue swelling in 4/6 patients; no abnormalities were demonstrated in the other two. Bone scan, CT and MRI depicted bone involvement. CT and MRI also showed inflammatory lesion spread to surrounding soft tissue. 99mTc-HMPAO scintigraphy was not performed in acute osteomyelitis, because of technical difficulties in performing the exam promptly; thus, the early diagnosis of lesion nature was made with bone biopsy. As for subacute osteomyelitis (23 patients), 99mTc-HMPAO scintigraphy was performed in 8/23 patients and proved to be a highly sensitive method, showing cell clusters and confirming the diagnosis of inflammatory lesion. MRI showed a focal area of intermediate-low signal intensity on T1-weighted sequences, with small focal intralesional areas of low intensity, a low-signal perifocal rim and diffusely low signal of surrounding bone marrow. T2-weighted images showed high signal intensity in both the abscess lesion and bone marrow, the latter probably due to edema. In 5 patients, a paramagnetic contrast agent (Gd-DTPA) was administered during MRI and showed inhomogeneous enhancement of both the inflammatory lesion and surrounding bone marrow. As for chronic osteomyelitis (7 patients), MRI was performed in 5/7 patients. In 4 patients the lesion appeared as a low-signal area on T1-weighted images while T2-weighted images showed an inhomogeneous high-signal area. In the same patients, 99mTc-HMPAO scintigraphy was always positive. In patient 5, the lesion was represented by a low-signal area on both T1 and T2-weighted images, while 99mTc-HMPAO was negative. Therefore, in chronic osteomyelitis, both MRI and 99mTc-HMPAO were useful in detecting both spinal and peripheral bone involvement, which was in some cases asymptomatic at first observation CR, CT (3/4) and MR (4/4) findings extra-axial localizations were similar to those in subacute-chronic forms.