Chronic osteomyelitis examined by CT

CT examination of 25 patients who had acute exacerbations of chronic osteomyelitis allowed for the correct identification of single or multiple sequestra in 14 surgical patients. Plain radiographs were equivocal for sequestra in seven of these patients, because the sequestra were too small or because diffuse bony sclerosis was present. CT also demonstrated a foreign body and five soft tissue abscesses not suspected on the basis of plain radiographs. CT studies, which helped guide the operative approach, were also useful in treating those patients whose plain radiographs were positive for sequestra. We review the potential role of CT in evaluating patients with chronic osteomyelitis.     

Disease activity in osteomyelitis: role of radiography

To determine the impact of radiographic findings on the interpretation of bone and gallium scans of patients with active osteomyelitis, the authors reviewed the medical records and radiologic examinations of 104 patients. The only diagnostic finding of active disease on radiographs was the presence of a sequestrum (three patients). Other findings--such as erosion, soft-tissue swelling, and periosteal reaction--proved nonspecific and did not differentiate active from inactive disease. Furthermore, these findings did not significantly change the sensitivity or specificity of the bone and gallium scans, either in detecting or in excluding the presence of active disease.     

Bacterial osteomyelitis: findings on plain radiography, CT, MR, and scintigraphy

Early detection of osteomyelitis is essential if appropriate therapy is to be started before bone devitalization. Although the 99mTc-methylene diphosphonate (MDP) bone scan may signify the possibility of osteomyelitis days or weeks before osseous changes are apparent on standard radiographs, the radiographic changes may provide important diagnostic clues. The 67Ga-citrate scan augments the diagnostic value of the 99mTc-MDP scan, and the 111In-labeled WBC scan is useful for detecting abscesses. CT aids in the detection of sequestra, and MR imaging is useful in defining the extent of the inflammatory process and in distinguishing osteomyelitis from cellulitis. In this article, we review and correlate the changes of bacterial osteomyelitis shown by these imaging methods.     

Detection of acute osteomyelitis with indium-111 labeled white blood cells in a patient with sickle cell disease

A young patient with sickle cell disease (SCD) and multiple hospitalizations for crisis was admitted because of suspected osteomyelitis. Initial laboratory work, radiographs, and bone images were not contributory. An In-111 white blood cell (WBC) study demonstrated two areas of increased radionuclide uptake consistent with osteomyelitis. One of these had associated soft tissue infection. No other areas of active osteomyelitis were visualized, in spite of the presence of several additional infection sites. Imaging with In-111 WBC is probably not justified for routine diagnosis of acute osteomyelitis in areas free of previous disease, where conventional bone images are highly efficient. In-111 WBC imaging, however, may be helpful in detecting osteomyelitis in selected patients with SCD in whom Tc-99m bone images and radiographs are usually abnormal and difficult to interpret due to previous bone infarcts. Localization of the infection focus is very important in choosing the aspiration site for bacteriologic studies. A negative study, however, should be interpreted cautiously.     

Computed tomography as a diagnostic aid in diabetic and other problem feet

Determining whether osteomyelitis is present in patients with foot infections represents a significant diagnostic challenge. As bone uptake with nuclide scans can be affected by soft tissue infection, we performed computed tomography (CT) on seven patients to see if marrow or bone abnormalities could be seen and used to predict the presence or absence of osteomyelitis. The CT scans correctly predicted the presence or absence of osteomyelitis in all seven patients. Four patients had osteomyelitis and three patients did not. Nuclide bone scans had one false-positive and one false-negative result. In this small series, CT proved helpful in evaluating foot problems.     

Osteomyelitis of the foot in diabetic patients: evaluation with plain film, 99mTc-MDP bone scintigraphy, and MR imaging

Diagnosis of osteomyelitis of the foot in diabetic patients may be difficult because of the coexistence of chronic cellulitis, vascular insufficiency, and peripheral neuropathy. This study compared the diagnostic accuracies of plain films, bone scans, and MR imaging studies in diabetic patients with suspicion of osteomyelitis of the foot. Twenty-nine plain radiographs, 20 bone scans, and 30 MR studies were obtained in 24 patients. Twenty-nine bones from 14 patients were pathologically proved either positive (25 bones) or negative (four bones) for osteomyelitis. Another 15 bones (10 patients) studied with MR had no pathologic proof, but the bones healed with only local wound care and/or a short course of oral antibiotics. These patients had trauma, cellulitis, or unhealed ulcers. The sensitivity and specificity of plain films were both 75%. Bone scans had a very low specificity (100% false-positive rate). A negative bone scan should strongly exclude the probability of osteomyelitis. Unlike the findings in previous reports, MR had much higher sensitivity and specificity than bone scans in detecting osteomyelitis in diabetic patients. When the 10 patients without pathologic proof (those who presumably had neuroarthropathy, vascular insufficiency, and/or cellulitis) were included, the sensitivity and specificity of all three techniques decreased. Our experience with this small group of patients suggests that MR is a useful imaging technique for diagnosing osteomyelitis of the foot in diabetic patients.     

Chronic osteomyelitis: bone and gallium scan patterns associated with active disease

Bone and gallium scans are used to assess osteomyelitis patients with prior bone disease. To refine the criteria for interpreting these scans, the data from 136 consecutive patients with clinically suspected osteomyelitis were reviewed. Active osteomyelitis was diagnosed with surgery or biopsy and culture in 49 patients, excluded with the same criteria in 16, and excluded by clinical follow-up for at least 6 months in 71. Five different scintigraphic patterns were found. The true-positive and false-positive ratios, the likelihood ratios, and posterior probabilities for active osteomyelitis in each pattern were calculated. Only one pattern (gallium uptake exceeding bone-seeking radiopharmaceutical uptake) was indicative of active disease. Other patterns slightly raised or decreased the probability of disease. The extent of these changes varies directly with the prior probability of disease, determined from patient-specific factors (e.g., clinical data, laboratory data, findings on plain films) known best by the referring clinician.     

Acute osteomyelitis in children: combined Tc-99m and Ga-67 imaging

This retrospective study was done to determine the value of combined bone (technetium-99m methylene-diphosphonate) and gallium-67 citrate imaging in selected children with complicated clinical situations. Thirty-one children were evaluated for suspected osteomyelitis by bone scan followed within 4 days by a gallium scan. These 31 children represented a subpopulation in whom the Tc-99m scan is known to be potentially unreliable in diagnosing acute osteomyelitis. Eight children had acute osteomyelitis by strict criteria, while 23 did not. The bone scan successfully identified five of the eight with osteomyelitis but was positive in ten of the other 23. The gallium scan correctly identified all eight with osteomyelitis but was positive in seven of the other 23. The gallium scan was significantly less specific when the suspected lesion was in the extremities compared with central locations; causes of false-positive gallium scans included fracture and juvenile rheumatoid arthritis. Combined gallium and bone scanning increased accuracy of the scintigraphic diagnosis of acute osteomyelitis. Both tests may, however, be abnormal in conditions other than osteomyelitis. These findings emphasize the importance of correlating all imaging studies in detection of osteomyelitis.     

Role of scintigraphy in musculoskeletal and spinal infections

Clinical findings are still the mainstay for suspecting the diagnosis of musculoskeletal infections, especially osteomyelitis. No single complementary imaging technique has 100% specificity and sensitivity for every case of musculoskeletal infection. Depending on the age of the patient, presence of orthopedic hardware, location of infection, underlying bone, and systemic conditions, the choice of imaging modalities must be tailored to the patient's condition. Plain radiographs are performed first and may be sufficient. In children, bone scan is highly accurate to diagnose osteomyelitis. Labeled leukocytes with complementary bone or bone marrow studies are recommended for orthopedic hardware or diabetic foot. Finally, gallium scanning is useful for the diagnosis of vertebral osteomyelitis. Current radiopharmaceuticals used for diagnosing infection also label inflammation. Newer products, as Infecton, should in the future allow better differentiation between infection and sterile inflammation.     

Exclusion of chronic osteomyelitis with F-18 fluorodeoxyglucose positron emission tomographic imaging

PURPOSE: Excluding the diagnosis of chronic osteomyelitis is often difficult with noninvasive techniques, especially when bone anatomy and structure have been altered by trauma, surgery, or soft-tissue infection. It has been reported that fluorodeoxyglucose (FDG) positron emission tomography (PET) has excellent potential to diagnose osteomyelitis. In this study, the accuracy of FDG PET in the diagnosis of chronic osteomyelitis was determined. METHOD: Twenty-two patients with possible osteomyelitis (5 in the tibia, 5 in the spine, 4 in the proximal femur, 4 in the pelvis, 2 in the maxilla, and 2 in the feet) who underwent FDG PET imaging and on whom operative or clinical follow-up data were available were included in this analysis. The final diagnosis was made by surgical exploration or clinical follow-up during a 1-year period. RESULTS: FDG PET correctly diagnosed the presence or absence of chronic osteomyelitis in 20 of 22 patients. Six had chronic osteomyelitis and 16 proved to be free of osteomyelitis. FDG PET correctly identified all six patients with chronic osteomyelitis but produced two false-positive results. This study had a sensitivity rate of 100%, a specificity rate of 87.5%, and an accuracy rate of 90.9%. CONCLUSION: FDG PET is a highly effective imaging method to exclude osteomyelitis when a negative scan result is obtained. However, positive results can be caused not only by true osteomyelitis but also by inflammation in the bone or surrounding soft tissues as a result of other causes. Overall, FDG PET may prove to be the preferred study in the management of patients with possible chronic osteomyelitis.     

Chronische Infektionen des Skelettsystems Bildgebende Diagnostik

The diagnosis of chronic osteomyelitis is made on the basis of clinical, radiologic and histologic findings. The role of imaging in patients with known chronic osteomyelitis is to detect and to delineate areas of active infection. To correctly interpret the imaging findings, it is essential to take both the individual clinical findings and previous imaging studies into account. Reliable signs of active infection are bone marrow abscess, sequestra and sinus tract formation. Only the combined evaluation of bony changes together with alterations of the adjacent soft tissues provides good diagnostic accuracy. Projection radiography gives an overview of the condition of the bone, which provides the basis for follow-up and the selection of further imaging modalities. Computed tomography can be used to evaluate even discrete or complex bony alterations and to guide percutaneous biopsy or drainage. Magnetic resonance imaging achieves the best diagnostic sensitivity and specificity and provides superior contrast as well as anatomical resolution in both bone marrow and soft tissues. In this paper the features and clinical relevance of imaging in primary chronic osteomyelitis, posttraumatic osteomyelitis, tuberculous spondylitis and osteomyelitis of the diabetic foot are reviewed, with particular respect to MRI.     

Chronic complicated osteomyelitis of the lower extremity: evaluation with MR imaging

Preoperative magnetic resonance (MR) imaging examinations were performed with a 1.5-T superconducting magnet in 14 patients who had extensive deformities of the bones and soft tissues of the lower extremities due to previous trauma, surgery, and chronic infection. This retrospective study assessed the diagnostic performance of MR imaging in determining the presence and extent of active bone and soft-tissue infections. The presence and extent of active osteomyelitis were confirmed by reviewing the clinical, surgical, histologic, and microbiologic records of all patients. Of the 14 MR imaging examinations, 11 were true-positive, two were true-negative, one was false-positive, and none was false-negative. In the indium scans obtained in this group of patients, five were true-positive, three were true-negative, none was false-positive, and three were false-negative. In two amputated extremities, close correlation was found between the extent of disease seen on surgical and pathologic examination and that demonstrated by MR imaging, which could delineate the course of sinus tracts. MR imaging was therefore helpful in assessing the activity of chronic complicated osteomyelitis and beneficial in surgical planning for these patients.     

Multiple myeloma: evaluation by CT

Although patients who have multiple myeloma usually have straightforward clinical symptoms and corroborative radiographs, in some instances, these patients will present atypically, with symptoms suggesting active disease but radiographs that are normal or nonspecific. We reviewed the records of 32 patients who had documented multiple myeloma and had undergone CT examinations, assessing the value of those examinations. Although CT is not indicated in all patients who have multiple myeloma, it is especially useful in patients who have bone pain and normal or nonspecific radiographs. CT provided confirmatory information in all cases in which lesions were seen on radiographs. CT also frequently demonstrated a greater extent of disease than could be appreciated on the radiographs.     

Chronic osteomyelitis: monitoring by 99mTc phosphate and 67Ga citrate imaging

Thirteen patients with chronic osteomyelitis, treated for 6 months with rifampin, had serial 99mTc phosphate and 67Ga scans to determine their value in assessing response to treatment. In patients who responded to treatment, gallium scans were deemed more accurate than 99mTc phosphate bone scans. The gallium scans, although still abnormal at the end of 6 months of antibiotic therapy, showed an improvement trend in all the responders except one in whom fracture recurred. Worsening or lack of improvement on gallium scans predicted active bone infection in five of six "clinical-failure" patients who had documented active bone infection. 67Ga scans eventually became normal in all patients who remained asymptomatic (excluding one with recurrent fracture). 99mTc phosphate scans became normal in only one of five clinical responders. All nonresponders had persistently abnormal scans, although after 6 months of therapy only four of seven showed worsening or no improvement on the scan. Therefore, 67Ga is preferred over 99mTc phosphate bone scans in the assessment of response to therapy in chronic bone infection. Clinical utility of the gallium scan is most significant in patients whose clinical assessment is uncertain, but routine use of this technique does not appear to be warranted. Gallium images are most valuable when obtained over a period of time, so that the trend of improvement versus nonimprovement is evident.     

Direct radiographic magnification in bone infections

An experimental model of bacterial osteomyelitis was used to investigate the correlation of direct radiographic magnification and histopathologic changes in the femora of rabbits. The histopathologic changes demonstrated a severe chronic state of osteomyelitis. The extent of radiographic changes was more clearly recognizable with direct radiological enlargement (up to 15-fold) than on normal radiographs: this applied to destruction of marrow and cortical bone, formation of sequestra, and (frequently) extraosseous extension. Histopathologic findings were in agreement with the changes revealed by direct radiographic enlargement.     

Evaluation of infectious diabetic foot complications with indium-111-labeled human nonspecific immunoglobulin G.

Osteomyelitis of the foot is a well-known complication of diabetes mellitus. In this study, the validity of 111In-labeled human nonspecific immunoglobulin G (IgG) scintigraphy was studied in 16 diabetic patients with foot ulcers, gangrene or painful Charcot joints. In all patients, plain radiographs, conventional bone scan images and 111In-IgG images were recorded. The results were verified by histologic examination of surgical specimens in patients who did not respond to antibiotic treatment within 2-3 wk (10 lesions) or long-term clinical follow-up of at least 6-mo (16 lesions). On the bone scans, all seven osteomyelitic foci were detected. However, 19 additional foci not due to osteomyelitis were seen. The absence of true-negative bone scans in this study resulted in a specificity of 0%. On the plain radiographs, four of seven osteomyelitis foci were detected; for 111In-IgG scintigraphy, six of seven (sensitivity 57% and 86%, respectively). Plain radiographs correctly ruled out osteomyelitis in 15 of 19 lesions, 111In-IgG scintigraphy in 16 of 19 (specificity 79% and 84%, respectively). All imaging procedures gave false-positive results in penetrating ulcers over the calcaneus in two patients and in one patient with a Charcot joint, most likely due to recent fractures. A false-negative 111In-IgG study was observed in a patient with severe arterial angiopathy. Accurate estimation of probable osteomyelitis was not possible from the results of soft-tissue cultures, since in only 6 of 12 positive cultures, osteomyelitic foci could be proven. Indium-111-IgG scintigraphy can contribute to adequate evaluation of osteomyelitis in diabetic foot complications because it improves specificity when compared to bone scan and radiographic findings and improves sensitivity in comparison to plain radiographs.     

Imaging of osteomyelitis in the mature skeleton

Diagnosis of acute osteomyelitis is often challenging but can be made by plain radiograph, bone scan, or MR imaging. This diagnosis may be more problematic in small bones, in diabetic or immunocompromised patients, those partially treated, post-traumatic, previous surgery, or with pre-existing marrow conditions and associated soft tissue infections. CT is the modality of choice for revealing sequestra and cortical erosions in chronic osteomyelitis. Nonenhanced and enhanced STIR or fat-saturated sequences are essential to reveal the marrow abnormality and its extension for diagnosis of subtle cases with neuropathic or other associated conditions. Combined radionuclide scintigraphy becomes necessary in complicated situations.     

Vertebral osteomyelitis: assessment using MR

Thirty-seven patients who were clinically suspected of having vertebral osteomyelitis were prospectively evaluated with magnetic resonance (MR), radiography, and radionuclide studies. These findings were correlated with the final clinical, microbiologic, or histologic diagnoses. Based on the results of these latter studies, 23 patients were believed to have osteomyelitis. MR examinations consisted of at least a sagittal image (TE = 30 msec, TR = 0.5 sec) and an image obtained at TE = 120 msec, TR = 2-3 sec. All patients underwent radiographic and MR examinations, 36 underwent technetium 99m-HDP bone scanning, and 20 patients underwent gallium 67 scanning. Nineteen patients underwent both bone and gallium scanning. The imaging studies were reviewed independently by investigators blinded to the final diagnoses. MR had a sensitivity of 96%, specificity of 92%, and accuracy of 94%. Combined gallium and bone scan studies (19 cases) had a sensitivity of 90%, specificity of 100%, and accuracy of 94%. Bone scans alone had a sensitivity of 90%, specificity of 78%, and accuracy of 86%. Plain radiographs had a sensitivity of 82%, specificity of 57%, and accuracy of 73%. The MR appearance of vertebral osteomyelitis in this study was characteristic, and MR was as accurate and sensitive as radionuclide scanning in the detection of osteomyelitis.     

Rapid normalization of osseous FDG uptake following traumatic or surgical fractures

It is known that following a traumatic fracture or surgical intervention, bone scintigraphy reveals positive results for an extended period of time, posing a challenge when evaluating patients for possible malignancy or superimposed osteomyelitis. Previous reports indicate that acute fractures can also result in increased fluorine-18 fluorodeoxyglucose (FDG) accumulation and therefore cause difficulties when patients are evaluated for other indications by FDG-PET. The purpose of this study was to assess the pattern and time course of abnormal FDG uptake following traumatic or surgical fracture. A total of 1,517 consecutive patients who underwent whole-body FDG-PET imaging were retrospectively studied. A history of fractures or orthopedic intervention was obtained from an interview prior to scanning. The FDG-PET results were compared with the results of other imaging studies, including bone scans, radiographs, CT, and MRI, as well as surgical pathology reports. Thirty-seven patients with a known date of traumatic or surgical fracture were identified. Among these, 14 had fractures or surgery within 3 months prior to FDG-PET, while 23 had fractures or surgical intervention greater than 3 months prior to FDG-PET. FDG-PET showed no abnormally increased uptake at the known fracture or surgical sites in 30 of these patients. Notably, in the 23 patients with fractures more than 3 months old, all but one showed no abnormally increased uptake. Furthermore, the positive FDG uptake in this exception was a result of complicating osteomyelitis. In the 14 patients with a history of fracture less than 3 months old, only six had abnormally increased FDG uptake. Following traumatic or surgical fractures, FDG uptake is expected to be normal within 3 months unless the process is complicated by infection or malignancy.     

The role of computed tomography in the detection of bone metastases in breast cancer patients

Computed tomography (CT) of bone was carried out in 20 patients with breast cancer, all of whom had abnormal radionuclide uptake on skeletal scintigrams but normal conventional radiographs. Twenty-eight sites were examined and 13 showed metastases in 11 patients. Five of these patients had no evidence of extra-skeletal recurrent disease. Follow-up at eight of these sites showed healing, sclerosis or progression, all of which correlated well with clinical findings. CT showed benign causes of radionuclide accumulation in three patients (7 sites) but no abnormality in six patients (8 sites). None of these patients has subsequently developed bone metastases. CT is superior to conventional radiographs in the diagnosis of skeletal metastases and should be carried out when skeletal scintigraphy is positive and conventional examinations are normal.