Multimodality imaging of osteomyelitis

Current opinions on the mechanism, classification, imaging diagnosis and treatment of post-traumatic osteomyelitis

Post-traumatic osteomyelitis (PTO) is a worldwide problem in the field of orthopaedic trauma. So far, there is no ideal treatment or consensus-based gold standard for its management. This paper reviews the representative literature focusing on PTO, mainly from the following four aspects: (1) the pathophysiological mechanism of PTO and the interaction mechanism between bacteria and the body, including fracture stress, different components of internal fixation devices, immune response, occurrence and development mechanisms of inflammation in PTO, as well as the occurrence and development mechanisms of PTO in skeletal system; (2) clinical classification, mainly the etiological classification, histological classification, anatomical classification and the newly proposed new classifications (a brief analysis of their scope and limitations); (3) imaging diagnosis, including non-invasive examination and invasive examination (this paper discusses their advantages and disadvantages respectively, and briefly compares the sensitivity and effectiveness of the current examinations); and (4) strategies, including antibiotic administration, surgical choices and other treatment programs. Based on the above-mentioned four aspects, we try to put forward some noteworthy sections, in order to make the existing opinions more specific.

RIB OSTEOMYELITIS: A RARE COMPLICATION OF VARICELLA

Objective:

To report a case of varicella complicated by acute osteomyelitis in order to remind of a rare and potentially serious complication of a very common pediatric disease.

Case description:

A previously healthy 3-month-old female infant with 10-day history of varicella was admitted to the hospital for fever, groan and prostration. The initial laboratorial evaluation was compatible with bacterial sepsis. By the third day after admission, a swelling of the seventh left rib had developed. The ultrasound and scintigraphy evaluation suggested rib osteomyelitis. Blood cultures were negative. The patient completed six weeks of antibiotics with favorable clinical, laboratorial and imaging evolution.

Comments:

Varicella is one of the most frequent exanthematic diseases of childhood and it is usually self-limited. The most frequent complication is bacterial infection of cutaneous lesions. Osteoarticular complications are rare, and rib osteomyelitis is described in less than 1% of cases. The main route of dissemination is hematogenic, and the most frequent etiological agent is Staphylococcus aureus. The prognosis is generally good and depends on early detection and antibiotic initiation.

Scintigraphic Patterns of Indium-111 Oxine-Labeled White Blood Cell Imaging of Gram-Negative versus Gram-Positive Vertebral Osteomyelitis

OBJECTIVE

The goal of the study was to investigate whether or not gram-negative organisms that secrete antichemotactic factors cause the nonaccumulation pattern of 111In-oxine-labeled white blood cell (111In-WBC) scans.

MATERIALS AND METHODS

Staphylococcus aureus (gram-positive) (group 1) was injected into 25 rabbits and Escherichia coli (gram-negative) (group 2) into another 25 to induce infection in the lumbar vertebrae or left thigh bone (femur). Sixteen successfully infected and surviving rabbits from each group were used for imaging and analysis. Of the 16 rabbits, each group included 8 with vertebral infection and 8 with femur infection. For imaging, each rabbit was injected intravenously with 11.1 MBq (300 μCi) 111In-WBC, and images were acquired 24 h later. Microscopic histopathology was performed after decalcification to confirm osteomyelitis.

RESULTS

The 111In-WBC accumulation was observed in 7 (87.5%) of the 8 rabbits infected with S. aureus in the vertebrae and thigh bone. Of the rabbits infected with the gram-negative vertebrae, 1 (12.5%) showed little accumulation of 111In-WBC. Of the 8 rabbits with gram-negative-infected femurs, 1 had high accumulation and another had low accumulation of 111In-WBC, while the rest did not show any uptake. Osteomyelitis was confirmed by histopathology in all the successfully infected rabbits used for imaging.

CONCLUSION

In the majority of the gram-positive-infected rabbit vertebrae there was high accumulation of 111In-WBC. However, no accumulation of 111In-WBC was observed in most of the vertebrae infected with gram-negative organisms, which release antichemotactic factors that prevent adequate accumulation of WBC at the infected area.

Inflammation

Inflammation was described as early as 3000 BC in an Egyptian papyrus [1] and is still a common problem despite continuous advancements in prevention and treatment methods. The delineation of the site and extent of inflammation are crucial to the clinical management of infection and for monitoring the response to therapy [2].

A Rationale for the Use of F18-FDG PET/CT in Fever and Inflammation of Unknown Origin

This review focuses on the diagnostic value of hybrid F18-FDG Positron Emission Tomography/Computerized tomography (PET/CT) in fever of unknown origin (FUO) and inflammation of unknown origin (IUO). Due to the wide range of possible causes both FUO and IUO remain a clinical challenge for both patients and physicians. In addition, the aetiology of IUO shows the same variation in diseases as the FUO spectrum and probably requires the same diagnostic approach as FUO. There are numerous historically used diagnostic approaches incorporating invasive and non-invasive, and imaging techniques, all with relative high specificity but limited sensitivity. This hampers the generalization of these diagnostic approaches. However, recently published reports show that F18-FDG PET/CT in FUO and IUO has a high sensitivity and a relative non-specificity for malignancy, infection and inflammation. This makes F18-FDG PET/CT an ideal diagnostic tool to start the diagnostic process and to guide subsequent focused diagnostic approaches with higher specificity. In addition, F18-FDG PET/CT has a relative high negative predictive value. Therefore F18 FDG PET/CT should be incorporated in the routine diagnostic work-up of patients with FUO and IUO, preferably at an early stage in the diagnostic process.

Modern spinal instrumentation. Part 2: multimodality imaging approach for assessment of complications

Radiologists frequently encounter studies demonstrating spinal instrumentation, either as part of the patient's postoperative evaluation, or as incidental to a study performed for another purpose. It is important for the reporting radiologist to identify potential complications of commonly used spinal implants. Part 1 of this review examined both the surgical approaches used and the normal appearances of these spinal implants and bone grafting techniques. This second part of the review will focus on the multimodal imaging strategy adopted in the assessment of the instrumented spine and the demonstration of imaging findings of common postoperative complications.

Tc-99m Labeled HMPAO white Blood Cell Scintigraphy in Pediatric Patients

OBJECTIVE

(99m)Tc labeled hexamethylpropylene amine oxime (HMPAO) white blood cell (WBC) scintigraphy is a frequently used option for acute infection, particularly in pediatric patients. This scintigraphy is applied to detect sites of infection/inflammation in patients with fever of unknown origin, to find and follow up osteomyelitis, and to detect suspicion of acute appendicitis. The aim of this retrospective study was to evaluate the value of (99m)Tc-HMPAO labeled WBC scintigraphy in pediatric patients.

MATERIAL AND METHODS

The study was conducted between January 2006 and December 2008 and included 13 patients (5 boys, 8 girls; mean age 6.9±6.2 years). Those patients who had suspicion of bone infection (n=7), fever of unknown origin (n=3), and suspicion of acute appendicitis (n=3) were evaluated retrospectively. (99m)Tc-HMPAO labeled WBC scintigraphy imaging was performed to all patients. Diagnosis was done according to operation and pathological results or clinical follow-up.

RESULTS

(99m)Tc-HMPAO labeled WBC scintigraphy has been found to be true positive in 6 cases, true negative in 6 cases, and false negative in one patient who had fewer unknown origin. The false negative case has been found to have encephalitis with MRI.

CONCLUSION

Leukocyte scintigraphy has been described as a useful diagnostic tool in the diagnosis of suspicion of bone infection, fever of unknown origin and suspicion of acute appendicitis. (99m)Tc-HMPAO labeled WBC scintigraphy is a rapid and very accurate method for detecting those pathologies. Our results showed that WBC scintigraphy might be reliably used for diagnosis of suspected bone infection and acute appendicitis, fever of unknown origin, and acute appendicitis, in pediatric patient population.

CONFLICT OF INTEREST

None declared.

PET and SPECT in osteomyelitis and prosthetic bone and joint infections: a systematic review

OBJECTIVE

To review the literature on diagnostic accuracy and clinical value of single-photon emission computed tomography (SPECT) and positron emission tomography (PET) for imaging of bone and joint infections.

METHODS

The PubMed/MEDLINE and Embase (OvidSP) literature databases were systematically searched for publications on SPECT and PET on osteomyelitis and prosthetic bone and joint infections using specific guidelines with MeSH-terms, truncations, and completion using cross-references.

RESULTS

In 44 original articles (15 for SPECT and 29 for (18)F-fluorodeoxyglucose [FDG]-PET) on osteomyelitis and prosthetic bone and joint infection, 1634 patients were included (580 patients SPECT, 1054 patients FDG-PET). Level of evidence (Oxford criteria) was 2-3b. For SPECT, the highest diagnostic accuracy of 95% for diagnosis of bone and joint infections is achieved with combined (111)In-WBC and (99m)Tc-sulfur colloid. Acceptable diagnostic accuracy was also obtained with (99m)Tc-WBC or (111)In-WBC combined with (99m)Tc-methylene diphosphonate ((99m)Tc-MDP). FDG-PET is useful for diagnosis of osteomyelitis with a sensitivity and specificity generally over 95%. In patients with orthopedic implant infections, sensitivity varies widely from 28% to 91% and specificity from 9% to 97%. This variation in FDG-PET performance in orthopedic implant infections depends largely on the (use of different) criteria to diagnose infection. Determination of the best criteria is still a matter of debate.

CONCLUSIONS

SPECT/computed tomography (CT) with (111)In-WBC combined with (99m)Tc-MDP or (99m)Tc-sulfur colloid seems to be the best imaging technique for diagnosis of bone and joint infections. FDG-PET is also useful for diagnosis of osteomyelitis with improved spatial resolution over SPECT imaging, allowing more accurate localization. Localization can be further improved by adding CT. Diagnosis of orthopedic implant infections with FDG-PET depends strongly on the localization of the implant and the criteria used to diagnose infection. Confirmation of well defined criteria to diagnose infection on FDG-PET in patients with metallic implants is thus of paramount importance for optimal diagnosis.

Role of modern imaging techniques for diagnosis of infection in the era of 18F-fluorodeoxyglucose positron emission tomography

During the past several years, it has become quite evident that positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) imaging can play a major role in the management of patients with suspected infection. Particularly, several groups have demonstrated that this powerful imaging methodology is very effective in the evaluation of osteomyelitis, infected prostheses, fever of unknown origin, and AIDS. In view of its extraordinary sensitivity in detecting disease activity and the ability to quantitate the degree of FDG uptake, PET might prove to be an appropriate modality for monitoring disease activity and evaluating response to therapy. FDG-PET has many advantages over existing imaging techniques for the diagnosis of infectious diseases. These include feasibility of securing diagnostic results within 1.5 to 2 h, excellent spatial resolution, and accurate anatomical localization of sites of abnormality. The availability of PET/computed tomography as a practical tool has further enhanced the role of metabolic imaging in many settings. In the future, this modality is very likely to be employed on a routine basis for detecting, characterizing, and monitoring patients with suspected and proven infection.

Reliability of white blood cell scan in the follow-up of osteomyelitis

INTRODUCTION

The question of whether antibiotic treatment does or does not affect reliability of white blood cell scan (WBCS) to detect disease activity in clinical practice is still unanswered. Our aim was to study the relationship between scintigraphic findings of WBCS and antibiotic therapy in a group of patients affected with osteomyelitis (OM).

METHODS

We retrospectively reviewed 57 scans, performed in 18 patients affected by OM and who were on antibiotic treatment. The number of therapy weeks was calculated for each antibiotic. A comparison of results obtained during and after discontinuation of the antibiotic treatment was made. Overall sensitivity, specificity and accuracy of WBCS were calculated and compared with those obtained in patients undergoing therapy.

RESULTS

Forty-seven scans were performed during treatment and 10 scans after discontinuation of treatment. The scintigraphic results obtained during and after discontinuation of treatment were as follows: TN 14 and 8, TP 31 and 2, FN 2 and 0, FP 0 and 0, respectively. Sensitivity, specificity and accuracy of WBCS, calculated in all patients, were 94.3%, 100% and 96.5% respectively. In patients receiving antibiotic therapy, the same parameters were 93.9%, 100% and 95.7% respectively. In patients treated with antibiotics that can decrease leukocyte function, there were 10 TN, 14 TP, 2 FN and 0 FP, while in patients treated with antibiotics that have not effect on leukocyte function there were 4 TN, 17 TP, 0 FN and 0 FP.

CONCLUSION

The reliability of WBCS in the detection of disease activity during antibiotic treatment does not change significantly. It can be assumed that the influence of antibiotic therapy on labelled leukocyte behaviour is negligible.

Imaging of osteomyelitis: current concepts

Osteomyelitis frequently requires more than one imaging technique for an accurate diagnosis. Conventional radiography still remains the first imaging modality. MRI and nuclear medicine are the most sensitive and specific methods for the detection of osteomyelitis. MRI provides more accurate information regarding the extent of the infectious process. Ultrasound represents a noninvasive method to evaluate the involved soft tissues and cortical bone and may provide guidance for diagnostic or therapeutic aspiration, drainage, or tissue biopsy. CT scan can be a useful method to detect early osseous erosion and to document the presence of sequestra. PET and SPECT are highly accurate techniques for the evaluation of chronic osteomyelitis, allowing differentiation from soft tissue infection.

Nuclear medicine imaging of bone infections

The inflammation and infection of bone include a wide range of processes that can result in a reduction of function or in the complete inability of patients. Apart from the inflammation, infection is sustained by pyogenic microorganisms and results mostly in massive destruction of bones and joints. The treatment of osteomyelitis requires long and expensive medical therapies and, sometimes, surgical resection for debridement of necrotic bone or to consolidate or substitute the compromised bones and joints. Radiographs and bone cultures are the mainstays for the diagnosis but often are useless in the diagnosis of activity or relapse of infection in the lengthy management of these patients. Imaging with radiopharmaceuticals, computed tomography and magnetic resonance are also used to study secondary and chronic infections and their diffusion to soft or deep tissues. The diagnosis is quite easy in acute osteomyelitis of long bones when the structure of bone is still intact. But most cases of osteomyelitis are subacute or chronic at the onset or become chronic during their evolution because of the frequent resistance to antibiotics. In chronic osteomyelitis the structure of bones is altered by fractures, surgical interventions and as a result of bone reabsorption produced by the infection. Metallic implants and prostheses produce artefacts both in computed tomography and magnetic resonance images, and radionuclide studies should be essential in these cases. Vertebral osteomyelitis is a specific entity that can be correctly diagnosed by computed tomography or magnetic resonance imaging at the onset of symptoms but only with radionuclide imaging is it possible to assess the activity of the disease after surgical stabilization or medical therapy. The lack of comparative studies showing the accuracy of each radiopharmaceutical for the study of bone infection does not allow the best nuclear medicine techniques to be chosen in an evidence-based manner. To this end we performed a meta-analysis of peer reviewed articles published between 1984 and 2004 describing the use of nuclear medicine imaging for the study of the most frequent causes of bone infections, including prosthetic joint, peripheric post-traumatic bone infections, vertebral and sternal infections. Guidelines for the choice of the optimal radiopharmaceuticals to be used in each clinical condition and for different aims is provided.

Acute osteomyelitis as a complication of varicella

Varicella is a common viral infection in childhood, and acute osteomyelitis is one of the rare but serious complications. We report two cases of osteomyelitis as a complication of varicella. The possibilities and limitations of the different imaging modalities are discussed, as well as imaging findings during the course of this condition.

Hematogenous Vertebral Osteomyelitis Due to Staphylococcus aureus in the Adult: Clinical Features and Therapeutic Outcomes

OBJECTIVE

Staphylococcus aureus is the most common cause of hematogenous vertebral osteomyelitis in adults. To better define clinical features and therapeutic outcomes, the charts of 40 adult patients with S aureus hematogenous vertebral osteomyelitis were retrospectively reviewed.

METHODS

Retrospective chart review using standardized data collection form.

RESULTS

S aureus hematogenous vertebral osteomyelitis commonly occurred in the settings of recent invasive procedures (55% of patients), insulin use (28%), and hemodialysis (20%). Ten percent of patients had S aureus bacteremia or vascular catheter infection within the preceding 6 months. Median time from first symptom to diagnosis was 51.3 days. A portal of entry for S aureus was identified in 13 patients (32.5%); intravenous catheters were the likely origin in 9 of those 13 patients. Concurrent endocarditis was present in 4 patients. Forty-eight percent of patients had neurologic abnormalities and 60% of patients had an epidural, paraspinous, or psoas abscess demonstrated by neuroimaging. S aureus was isolated through fine-needle aspiration in 17 of 23 patients (74%) and from blood cultures in 23 of 34 patients (68%). Infection was due to methicillin-susceptible S aureus in 67.5% of patients. All patients received intravenous antibiotics for a mean duration of 58.6 days; 36 of 40 (90%) also received concomitant rifampin. Twenty-seven percent and 12.5% of patients underwent surgical debridement and CT-guided drainage of abscesses, respectively. After intravenous therapy, 19 of 30 eligible patients received oral continuation treatment. The mean duration of total antibiotic therapy was 142.2 days.

CONCLUSIONS

Cure of infection was achieved in 83% (24/29) of evaluable patients, but 50% of those achieving cure still had infection-related sequelae. Intravenous antibiotic therapy for at least 8 weeks was the only clinical factor associated with cure (P = 0.05, two-tailed Fisher exact test).

What is the role of bone scintigraphy in the diagnosis of infected joint prostheses?

AIM

To analyse the role played by bone scintigraphy in the diagnosis of infected joint prostheses.

METHODS

The study included 77 patients, aged 32-77 years, in whom infection of a joint prosthesis (48 hip, 29 knee) was suspected. In all patients the following examinations were performed consecutively: a two-phase Tc methylene diphosphonate (Tc-MDP) bone scan, a Tc hexamethylproplyene amine oxime (Tc-HMPAO) labelled white blood cell (WBC) scan, and a Tc microcolloid bone marrow (BM) scan. The minimum interval between examinations was 48 h. The diagnoses were based on data obtained from bacteriological cultures.

RESULTS

The bone scan was positive in all patients and 28 of them had an infection (sensitivity 100%, specificity 0%). The WBC scan was positive in 61 patients but only 27 had an infection. The WBC scan was negative in 16 patients, and the possibility of infection was discarded in 15 of these cases (sensitivity 96%, specificity 30%). The results of the bone marrow scan were not compatible with those of the WBC scan (suggestive of infection) in 27 patients: 26 of them had prosthesis infection. The results of both examinations were compatible in the other 34 patients and the possibility of infection was discarded in 33 of these patients (sensitivity 92.8%, specificity 98%). The addition of a BM scan to a WBC scan decreased the sensitivity from 96% to 92.8% but increased specificity from 30% to 98%. The addition of a bone scan to this dual combination did not alter the results.

CONCLUSIONS

When infection of a prosthesis is suspected the diagnostic procedure should start with a WBC scan followed, if positive, by a BM scan. This procedure reduces the cost, the time required for a diagnosis, and the dose of radiation received by the patient.

Imaging of osteomyelitis and musculoskeletal soft tissue infections: current concepts

The diagnostic imaging of osteomyelitis can require the confluence of multiple imaging technologies. Conventional radiography should always be the first imaging modality. Sonography is most useful in the diagnosis of fluid collections in a joint or in the extra-articular soft tissues but is not useful for evaluating presence of osseous infection. CT scan can be a useful method to detect early osseous erosion and to document the presence of sequestrum, foreign body, or gas formation but generally is less sensitive than other modalities for the detection of bone infection. Nuclear medicine and MRI are the most sensitive and most specific imaging modalities for the detection of osteomyelitis. Nuclear medicine is particularly useful in identifying multifocal involvement, which is common in children. MRI provides more accurate information of the local extent of the soft tissues and possible soft tissue abscess in patients with musculoskeletal infection.

Detection of metallic implant-associated infections with FDG PET in patients with trauma: correlation with microbiologic results

PURPOSE

To prospectively evaluate the value of positron emission tomography (PET) with fluorine 18 fluorodeoxyglucose (FDG) in the detection of metallic implant-associated infections in patients with trauma.

MATERIALS AND METHODS

Twenty-nine partial-body FDG PET scans in 22 patients suspected of having metallic implant-associated infections were obtained prior to surgery. In two of the 22 patients, data were acquired with a combined PET-CT in-line system. Soft-tissue and bone infections were evaluated. PET scans were analyzed by two experienced nuclear medicine physicians first separately and then in consensus. Disease status was defined on the basis of the results of microbiologic evaluation of surgical specimens together with intraoperative findings. Sensitivities, specificities, accuracies, interobserver variability (determination of kappa values), and receiver operating characteristic curves were obtained.

RESULTS

Of 29 PET scans, 14 were true-positive, 14 were true-negative, and one was false-positive. Sensitivity, specificity, and accuracy were 100%, 93.3%, and 97%, respectively, for all PET data; 100%, 100%, and 100%, respectively, for the central skeleton; and 100%, 87.5%, and 95%, respectively, for the peripheral skeleton. The degree of overall interobserver concordance was high (kappa = 0.96).

CONCLUSION

FDG PET appears to be a sensitive and specific method for the detection of infectious foci due to metallic implants in patients with trauma.

Radionuclide three-phase whole-body bone imaging

PURPOSE

To describe the radionuclide three-phase whole-body bone imaging (TPWBBI) technique and discuss the usefulness of its application.

MATERIALS AND METHODS

TPWBBI was performed after a single intravenous injection of 555 to 925 MBq (15 to 25 mCi) Tc-99m MDP. Whole-body arterial flow (phase one) followed by blood-pool and tissue perfusion (phase two) images were obtained with the moving detector head speed set at 150 cm/minute and 40 cm/minute, respectively. Conventional whole-body static bone images (phase three) were obtained 3 hours later.

RESULTS

When 542 consecutive TPWBBI results were reviewed, 394 (166 extraskeletal and 228 skeletal) abnormalities were detected during phases one and two. The 166 extraosseous lesions included vascular diseases: abdominal aortic aneurysms and peripheral vascular diseases and renal abnormalities, liver abnormalities, ascites, and pleural effusions. Many of these were incidentally detected clinically significant findings and would not have been identified on conventional static bone images. It helps to differentiate among acute and chronic fractures, active and inactive inflammatory diseases such as arthritis or osteomyelitis, and Paget's disease.

CONCLUSIONS

With a single injection of Tc-99m MDP, whole-body images obtained in the arterial phase, the blood-pool and tissue perfusion phase, and the static bone phase can identify many clinically significant skeletal and soft tissue abnormalities. TPWBBI can differentiate between active and inactive phases of different disease processes and thereby provide a diagnosis that is more specific than a conventional single-phase bone scan. It may be applicable as a tool for nuclear physical examination.

Comparison of Tc-99m methylene diphosphonate, Tc-99m human immune globulin, and Tc-99m-labeled white blood cell scintigraphy in the diabetic foot

PURPOSE

The aims of this prospective study were to evaluate the contribution of Tc-99m methylene diphosphonate (MDP), Tc-99m human immune globulin (HIG), and Tc-99m white blood cell (WBC) to the diagnosis of osteomyelitis in the diabetic foot and to evaluate the surgical or medical therapy with Tc-99m HIG and Tc-99m WBC scans.

METHODS

Twenty patients (15 men, 5 women) with suspected pedal osteomyelitis were included in the study. All patients had type II diabetics. Three- and four-phase bone scintigraphy (3P-MDP, 4P-MDP), early (e) and late (l) HIG, and WBC scans were completed within 1 week in all patients. The lesion-to-background ratios were calculated for early and late images of the feet for all scans and named as the indices. Eight weeks after the end of medical or surgical therapy, Tc-99m HIG and Tc-99m WBC scans were repeated in 10 patients. The difference in indices between 3P-MDP and 4P-MDP for osteomyelitis and indices for osteomyelitis, cellulitis, and inflammation in Tc-99m HIG and Tc-99m WBC in early and late scans were tested for significance.

RESULTS

In 20 patients, 53 lesions were investigated. Among these 53 lesions were 25 sites of proved osteomyelitis, 6 sites of cellulitis, and 22 sites of inflammation confirmed by radiography, microbiologic culture, and clinical evaluation. 4P-MDP was more specific than 3P-MDP for detecting osteomyelitis (50% and 67%, respectively). There was also a significant difference between the mean indices of 3P-MDP and 4P-MDP (P < 0.000). The index values were increased in 4P-MDP scans. There was no significant difference between the indices of early and late Tc-99m HIG scans for inflammation, cellulitis, and osteomyelitis. Early and late Tc-99m WBC scans did not show a significant difference in differentiating osteomyelitis. However, Tc-99m WBC scans could differentiate aseptic inflammation from infection (P < 0.031) in early and late scans. There was a significant difference of index values between pre- and post-treatment Tc-99m HIG and Tc-99m WBC scans. The best combination of scans for detecting osteomyelitis was 4P-MDP with WBC scans, with an accuracy rate of 92%.

CONCLUSIONS

These results show that four-phase bone scintigraphy with early Tc-99m WBC scanning is preferred for detecting osteomyelitis of the diabetic foot. To evaluate the response to therapy, Tc-99m WBC scans are the preferred method, but if this is not available, Tc-99m HIG scanning can be used.

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.

Differentiating osteomyelitis from bone infarction in sickle cell disease

This brief review discusses one possible approach to evaluating the sickle cell patient with bone pain. The major differential diagnoses include osteomyelitis and bone infarction. Based on previous studies, we provide an approach to assessing and treating patients with the possible diagnosis of osteomyelitis. An algorithm has been provided, which emphasizes the importance of the initial history and physical examination. Specific radiographic studies are recommended to aid in making the initial assessment and to determine whether the patient has an infarct or osteomyelitis. Differentiating osteomyelitis from infarction in sickle cell patients remains a challenge for the pediatrician. This algorithm can be used as a guide for physicians who evaluate such patients in the acute care setting.

Nuclear medicine imaging in early vertebral osteomyelitis: still of clinical utility

A case is presented of vertebral osteomyelitis in an elderly confused patient with poorly localizing signs. The lesion was not diagnosed on the initial MRI study of the spine due to poor targeting. The abnormality was detected on a bone scan the following day. This was confirmed with a gallium scan 3 days later, and also a repeat MRI study 11 days after the first MRI, using an optimized protocol over the region of interest established by the bone scan.

A prospective study of soft-tissue ultrasonography in sickle cell disease patients with suspected osteomyelitis

AIM

A prospective study was done to assess the accuracy of soft tissue ultrasonography in patients with sickle cell disease (SCD) presenting with suspected osteomyelitis.

MATERIALS AND METHODS

Thirty-one SCD patients had soft tissue ultrasonography on 38 occasions (18 men, 13 women; mean age 8.2 years). The initial ultrasonographic signs and diagnosis were compared with the final clinical diagnosis, which was based on clinical progress and scintigraphy.

RESULT

The overall sensitivity of ultrasound in diagnosing osteomyelitis was 74% with a specificity of 63%. The principal ultrasonographic finding of subperiosteal fluid was present in 14 (74%) patients with osteomyelitis and seven (37%) patients without infection. A finding of a subperiosteal fluid depth of 4 mm or more was significantly associated with osteomyelitis (P < 0.01).

CONCLUSION

Ultrasonography should be the initial investigation in SCD patients if osteomyelitis is suspected clinically. In such a clinical setting, a finding of 4 mm depth or more of subperiosteal fluid appears to be diagnostic. Previous statements that the presence of any subperiosteal fluid indicates infection are shown to be inaccurate. Patients with less than 4 mm of subperiosteal fluid require further imaging or aspiration to establish the diagnosis of osteomyelitis.

Orthopedic pathology of the lower extremities: scintigraphic evaluation in the thigh, knee, and leg

Radionuclide imaging (RI) of the osseous and nonosseous structures of the thigh, knee, and leg provide important diagnostic and prognostic information upon which the orthopedic surgeon can base treatment planning and management decisions. 99mTc-MDP scintigraphy is essential in overuse injuries such as stress fractures and shin splints. RI is important in assessing complications of trauma. It is the only imaging modality able to assess the magnitude of physeal stimulus caused by femoral fractures and to predict a favorable or unfavorable outcome of leg length by semiquantitative analysis; SPECT imaging can detect and locate decreased metabolism associated with posttraumatic closure of the physeal plate to predict growth arrest and deformities. Three-phase bone imaging (TPBI) is essential to differentiate hypervascular from avascular nonunions and follow delayed union. In osteonecrosis of the knee, bone scintigraphy precedes radiography changes even in stage l of the disease. 99mTc-MDP and 99mTc-HIG imaging are powerful tools in determining the outcomes of osteoarthritis and rheumatoid arthritis, respectively. Bone scintigraphy can also detect chronic ligament and acute and chronic meniscal lesions. The combined use of TPBI, gallium-67 citrate imaging, and indium-111 or 99mTc-HMPAO labeled leukocytes is important to diagnose and differentiate acute from chronic osteomyelitis, and to detect infected knee prostheses. Thallium-201 chloride imaging and 99mTc-sestamibi imaging have an important role in the assessment of tumor response to chemotherapy and in the quantification of tumor viability.

Hip and knee arthroplasty infection. In-111-IgG scintigraphy in 102 cases

We studied indium-111-labeled immunoglobulin G (In-111-IgG) scintigraphy for evaluation of total hip and knee arthroplasty infection in 100 patients (102 arthroplasties) where infection was suspected (85 total hip and 17 total knee replacements, 23 of which proved to be infected, all but 2 late infections). The sensitivity of In-111-IgG scintigraphy for infection was 1.0, for hip and knee arthroplasties the specificities were 0.8 and 0.5, respectively. False-positive results for infection occurred in cementless total hip arthroplasties up to 14 months after implantation. Aseptic inflammation due to formation of ectopic ossification and foreign-body response, following wear of the polyethylene socket, was responsible for false-positive results. The images should be read in conjunction with radiographs, which reduces the rate of false-positive results. In-111-IgG is a highly sensitive and fairly specific tool for detecting of late infection of total hip and total knee arthroplasties.

Three- to five-dimensional biomedical multisensor imaging for the assessment of neurological (dys) function

This report describes techniques and protocols implemented at the Geneva Canton University Hospitals (HUG) for the combination of various biomedical imaging modalities and sensors including electromagnetic tomography, to study, assess, and localize neurological (dys) function. The interest for this combination stems from the broad variety of information brought out by (functional) magnetic resonance imaging, magnetic resonance spectroscopy, computed tomography, single-photon emission tomography, positron emission tomography, and electromagnetic tomography. Combining these data allows morphology, metabolism, and function to be studied simultaneously, the complementary nature of the information from these modalities becoming evident when studying pathologies reflected by metabolic or electrophysiologic dysfunctions. Compared with other current multimodality approaches, the one at the HUG is totally compatible with both clinical and research protocols, and efficiently addresses the multidimensional registration and visualization issues. It also smoothly integrates electrophysiology and related data as fully featured modalities.