Gadolinium-DOTA enhanced MRI of painful osseous crises in children with sickle cell anemia

The many faces of sickle cell disease in children: complications in the appendicular skeleton

Sickle cell disease (SCD) is a hereditary red cell disorder with clinical manifestations secondary to sickling or crescent-shaped distortion of the red blood cells. Musculoskeletal complications of SCD are often the main causes for acute and chronic morbidities in children with manifestations including osteomyelitis, osteoporosis and osteonecrosis. This article aims to familiarise the paediatric radiologist with appendicular skeletal complications of SCD in the paediatric population and their imaging appearance.

Management of Salter-Harris Type 1 Fracture Complicated with Osteomyelitis in a Sickle Cell Disease Patient: A Case Report and Review of Literature

Salter-Harris fractures may occur due to a single injury or repetitive stress fractures on the extremities. Type I to III fractures are managed medically, while types IV and V, which are rare, are treated surgically. In the pediatric population, Salter-Harris I fractures of the distal tibia are commonly seen, and management of such fractures are well established in the literature. Despite the availability of a wide range of treatment for such fractures, osteonecrosis or avascular necrosis of the proximal femur can subsequently develop. Avascular necrosis is cell death secondary to metabolic disturbances, trauma, adverse effects of certain medications, or sickle cell disease. Avascular necrosis commonly affects the talus, humerus, or tibia in addition to the femoral head. Radiographic images are essential for prompt diagnosis and to minimize negative health outcomes in these patients. However, Salter-Harris I fracture in sickle cell patients can be very challenging due to these patients' vulnerability to bone infections and sickle cell crisis. In this case report, our patient with a history of sickle cell disease and with a diagnosis of Salter-Harris I fracture was treated with surgical intervention as type V, which is discussed in this article, and responded well to treatment. Thus, this case suggests a new approach to managing Salter-Harris I fractures complicated with osteomyelitis in sickle cell patients.

Frontal Bone Infarctions Masquerading as Bilateral Orbital Cellulitis in a Patient with Sickle Cell Disease

Repeated vaso-occlusive crises (VOCs) are the hallmark of sickle cell disease (SCD). These repeated crises can lead to bone infarcts, necrosis, and, over time, degenerative changes in the bone marrow. Orbital complications in SCD patients are infrequent and usually present as orbital cellulitis. We report the appearance of orbital bone infarction intraoperatively in the case of an 18-year-old Saudi male patient who has been diagnosed with SCD and presented with severe headaches and generalized body aches. He was admitted with a case of SCD with acute VOC and started on the hospital sickle cell protocol. During the admission, the patient developed bilateral periorbital swelling and left inferior dystopia secondary to bilateral frontoparietal bone infarction, which was evident on the magnetic resonance imaging.

Characteristics and outcomes of osteomyelitis in children with sickle cell disease: A 10-year single-center experience

BACKGROUND

Patients with sickle cell disease (SCD) are at increased risk for osteomyelitis (OM). Diagnosis of OM in SCD is challenging as the clinical presentation is similar to a vasoocclusive crisis (VOC) with no diagnostic gold standard. We report characteristics and outcomes of OM in SCD patients treated at our center over 10-year period.

DESIGN/METHOD

We conducted a retrospective analysis of patients with SCD who were treated for OM at our center over a 10-year period (2006-2016). Cases were identified utilizing radiology data mining software. Radiology reports and medical charts of potential OM cases were reviewed.

RESULTS

Twenty-eight children with SCD were treated for OM at our institution. Patients treated for OM were largely similar to patients treated for a VOC. However, patients treated for OM had significantly higher C-reactive protein (10 mg/dL vs 5.58 mg/dL, P = 0.03) and erythrocyte sedimentation rate (60 mm/h vs 47 mm/h, P = 0.02). Magnetic resonance imaging (MRI) findings were consistent with OM in 18 (64%) patients and indeterminate in the remaining. Based on clinical, laboratory, and radiological findings, the diagnosis of OM was considered confirmed in 3 patients, probable in 6 patients, and presumed in 19 patients. Nontyphoidal Salmonella was isolated from cultures in 9 (32%) patients, while no organism was identified in 19 (67%) patients. All patients were treated with antibiotics. Six patients (21%) required surgical interventions.

CONCLUSIONS

OM continues to pose diagnostic challenges. Most patients are treated for OM without definitive confirmation. Nontyphoidal Salmonella was the only organism identified in our cohort.

The challenge of differentiating vaso-occlusive crises from osteomyelitis in children with sickle cell disease and bone pain: A 15-year retrospective review

PURPOSE

The paediatric sickle cell disease (SCD) osteomyelitis (OM) incidence is 0.3% to 12%. Differentiating vaso-occlusive crises (VOC) from OM is a diagnostic challenge, with limited evidence guiding management. We present a 15-year review of a paediatric sickle cell cohort. We aim to identify OM incidence and provide a management protocol for these children presenting with bone pain.

METHODS

A prospective database of children with haemoglobinopathies (2002 to 2017) was analyzed for temperature, C-reactive protein (CRP) and white cell count (WCC) on admission as well as imaging, treatment and cultures. OM diagnosis was supported by imaging and blood cultures. VOC was defined as bone pain that improved without antibiotics.

RESULTS

Over 15 years, 96 children with SCD presented 358 times to hospital. Empirical antibiotics were given in 308 presentations. There were five cases of OM (1.4%); two acute and three chronic. In all, 50 presentations of VOC were identified. No significant differences in age were noted between the OM and VOC group. Temperature and CRP were significantly elevated in the OM group with no significant difference in WCC. Cultures were only positive in the chronic OM admissions. There were no cases of septic arthritis. No surgical intervention was required.

CONCLUSION

In children with SCD presenting with persistent bone pain, fever, elevated CRP and WCC, OM should be suspected and prompt antibiotic treatment started. Our treatment pathway was successful avoiding OM in 98.6% and septic arthritis in 100%. Further research on novel biological markers distinguishing OM from VOC should be investigated.

LEVEL OF EVIDENCE

III.

Utility of unenhanced fat-suppressed T1-weighted MRI in children with sickle cell disease -- can it differentiate bone infarcts from acute osteomyelitis?

BACKGROUND

Children with sickle cell disease (SCD) are at risk of bone infarcts and acute osteomyelitis. The clinical differentiation between a bone infarct and acute osteomyelitis is a diagnostic challenge. Unenhanced T1-W fat-saturated MR images have been proposed as a potential tool to differentiate bone infarcts from osteomyelitis.

OBJECTIVE

To evaluate the reliability of unenhanced T1-W fat-saturated MRI for differentiation between bone infarcts and acute osteomyelitis in children with SCD.

MATERIALS AND METHODS

We retrospectively reviewed the records of 31 children (20 boys, 11 girls; mean age 10.6 years, range 1.1-17.9 years) with SCD and acute bone pain who underwent MR imaging including unenhanced T1-W fat-saturated images from 2005 to 2010. Complete clinical charts were reviewed by a pediatric hematologist with training in infectious diseases to determine a clinical standard to define the presence or absence of osteomyelitis. A pediatric radiologist reviewed all MR imaging and was blinded to clinical information. Based on the signal intensity in T1-W fat-saturated images, the children were further classified as positive for osteomyelitis (low bone marrow signal intensity) or positive for bone infarct (high bone marrow signal intensity).

RESULTS

Based on the clinical standard, 5 children were classified as positive for osteomyelitis and 26 children as positive for bone infarct (negative for osteomyelitis). The bone marrow signal intensity on T1-W fat-saturated imaging was not significant for the differentiation between bone infarct and osteomyelitis (P = 0.56). None of the additional evaluated imaging parameters on unenhanced MRI proved reliable in differentiating these diagnoses.

CONCLUSION

The bone marrow signal intensity on unenhanced T1-W fat-saturated MR images is not a reliable criterion to differentiate bone infarcts from osteomyelitis in children.

Safety and efficacy of gadoteric acid in pediatric magnetic resonance imaging: overview of clinical trials and post-marketing studies

BACKGROUND

Gadoteric acid is a paramagnetic gadolinium macrocyclic contrast agent approved for use in MRI of cerebral and spinal lesions and for body imaging.

OBJECTIVE

To investigate the safety and efficacy of gadoteric acid in children by extensively reviewing clinical and post-marketing observational studies.

MATERIALS AND METHODS

Data were collected from 3,810 children (ages 3 days to 17 years) investigated in seven clinical trials of central nervous system (CNS) imaging (n = 141) and six post-marketing observational studies of CNS, musculoskeletal and whole-body MR imaging (n = 3,669). Of these, 3,569 children were 2-17 years of age and 241 were younger than 2 years. Gadoteric acid was generally administered at a dose of 0.1 mmol/kg. We evaluated image quality, lesion detection and border delineation, and the safety of gadoteric acid. We also reviewed post-marketing pharmacovigilance experience.

RESULTS

Consistent with findings in adults, gadoteric acid was effective in children for improving image quality compared with T1-W unenhanced sequences, providing diagnostic improvement, and often influencing the therapeutic approach, resulting in treatment modifications. In studies assessing neurological tumors, gadoteric acid improved border delineation, internal morphology and contrast enhancement compared to unenhanced MR imaging. Gadoteric acid has a well-established safety profile. Among all studies, a total of 10 children experienced 20 adverse events, 7 of which were thought to be related to gadoteric acid. No serious adverse events were reported in any study. Post-marketing pharmacovigilance experience did not find any specific safety concern.

CONCLUSION

Gadoteric acid was associated with improved lesion detection and delineation and is an effective and well-tolerated contrast agent for use in children.

Contrast-enhanced magnetic resonance imaging in pediatric patients: review and recommendations for current practice

Magnetic resonance imaging (MRI), frequently with contrast enhancement, is the preferred imaging modality for many indications in children. Practice varies widely between centers, reflecting the rapid pace of change and the need for further research. Guide-line changes, for example on contrast-medium choice, require continued practice reappraisal. This article reviews recent developments in pediatric contrast-enhanced MRI and offers recommendations on current best practice. Nine leading pediatric radiologists from internationally recognized radiology centers convened at a consensus meeting in Bordeaux, France, to discuss applications of contrast-enhanced MRI across a range of indications in children. Review of the literature indicated that few published data provide guidance on best practice in pediatric MRI. Discussion among the experts concluded that MRI is preferred over ionizing-radiation modalities for many indications, with advantages in safety and efficacy. Awareness of age-specific adaptations in MRI technique can optimize image quality. Gadolinium-based contrast media are recommended for enhancing imaging quality. The choice of most appropriate contrast medium should be based on criteria of safety, tolerability, and efficacy, characterized in age-specific clinical trials and personal experience.

Dilemma in differentiating between acute osteomyelitis and bone infarction in children with sickle cell disease: the role of ultrasound

BACKGROUND

Distinguishing between acute presentations of osteomyelitis (OM) and vaso-occlusive crisis (VOC) bone infarction in children with sickle cell disease (SCD) remains challenging for clinicians, particularly in culture-negative cases. We examined the combined role of ultrasound scan (USS), C - reactive protein and White blood counts (WCC) in aiding early diagnosis in children with SCD presenting acutely with non-specific symptoms such as bone pain, fever or swelling which are common in acute osteomyelitis or VOC.

METHODS

We reviewed the records of all children with SCD who were discharged from our department from October 2003 to December 2010 with a diagnosis of osteomyelitis based on clinical features and the results of radiological and laboratory investigations. A case control group with VOC who were investigated for OM were identified over the same period.

RESULTS

In the osteomyelitis group, USS finding of periosteal elevation and/or fluid collection was reported in 76% cases with the first scan (day 0-6). Overall 84% were diagnosed with USS (initial +repeat). 16% had negative USS. With VOC group, USS showed no evidence of fluid collection in 53/58 admissions (91%), none of the repeated USS showed any fluid collection. Mean C-reactive protein (CRP), and white cell count (WCC) were significantly higher in the OM.

CONCLUSION

The use of Ultrasound in combination with CRP and WCC is a reliable, cost-effective diagnostic tool for differentiating osteomyelitis from VOC bone infarction in SCD. A repeat ultrasound and/or magnetic resonance imaging (MRI) scan may be is necessary to confirm the diagnosis.

Tuberculous spondylodiscitis in a patient with a sickle-cell disease: CT findings

Background:

Although sickle-cell anemia (SCA) is common in black Americans, Sub-Saharan Africa and in the Mediterranean area, the disease is rare in the temperate climate zone. The manifestations of the disease are related mainly to the production of abnormal hemoglobin that leads to organ ischemia and increased susceptibility to infection caused by functional asplenia.

Case Report:

The authors present CT findings in a 39-year-old black woman diagnosed due to abdominal pain, lymphadenopathy and fever. CT of the thorax and abdomen demonstrated changes in the liver, spleen, and skeletal system suggestive of SCA complicated with spondylodiscitis in the thoracic spine.

Discussion:

Hepatomegaly and small calcified spleen are typical findings in older homozygotic patients with SCA. The lesions in the skeleton may be related either to intramedullary hematopoiesis or osteonecrosis and osteomyelitis. In the latter case, diffuse osteosclerosis and H-shaped vertebrae are most typical. Tuberculous spondylodiscitis is characterized by the location in the thoracic region, preferential involvement of anterior elements, relative sparing of intervertebral discs, and cold abscesses.

Gd-DOTA administration at MRI in children younger than 18 months of age: immediate adverse reactions

BACKGROUND

There is a paucity of evidence with regard to the safety of contrast medium administration at MRI in neonates and infants.

PURPOSE

To assess immediate adverse reactions in children younger than 18 months of age during routine clinical utilization of gadoteric acid (Gd-DOTA) in a cohort of patients with nonselected indications.

MATERIALS AND METHODS

One hundred and four neonates and infants were enrolled in a postmarketing survey with Gd-DOTA (Dotarem, Guerbet, Roissy, France) from a single pediatric hospital. A standardized questionnaire was used to collect the patient information.

RESULTS

All included children, ages 3 days to 18 months, received one injection of Gd-DOTA (volume 0.6-4 ml). No immediate adverse event was reported.

CONCLUSION

This postmarketing study involving neonates and infants suggests a favorable safety profile of Gd-DOTA in routine practice.

Musculoskeletal manifestations of sickle cell anaemia: a pictorial review

Sickle cell anaemia is an autosomal recessive genetic condition producing abnormal haemoglobin HbS molecules that result in stiff and sticky red blood cells leading to unpredictable episodes of microvascular occlusions. The clinical and radiological manifestations of sickle cell anaemia result from small vessel occlusion, leading to tissue ischemia/infarction and progressive end-organ damage. In this paper we discuss and illustrate the various musculoskeletal manifestations of sickle cell disease focusing primarily on marrow hyperplasia, osteomyelitis and septic arthritis, medullary and epiphyseal bone infarcts, growth defects, and soft tissue changes.

Bone-seeking probes for optical and magnetic resonance imaging

In clinical practice the imaging of bone tissue is based almost exclusively on x-ray or radiochemical methods. Alternative methods, such as MRI and optical imaging, can provide not only anatomical, but also physiological information, due to their ability to reflect the properties of body fluids (temperature, pH and concentration of ions). In this article we review bone targeting probes for MRI and fluorescence imaging. As bone targeting is mainly associated with phosphonate and bisphosphonate derivatives, we also focus on their sorption behavior. Also discussed in detail is the limitation of using bone-targeting probes for MRI and optical imaging mainly due to their long-time retention in bone tissue and the low permeability of tissues for light.

Magnetic resonance imaging of medullary bone infarction in the early stage

Medullary bone infarctions, which are believed to arise due to arterial obstructions in the bone, are usually asymptomatic and are noted incidentally in roentgenograms or bone scans performed for other reasons. We present two cases of acute bone infarctions that were found accidentally by magnetic resonance imaging (MRI). In both cases, conventional radiographs could not demonstrate any findings and the cases were clinically asymptomatic. The current two cases suggest that MRI shows various findings in bone infarctions.

Bone marrow edema of the femoral head and transient osteoporosis of the hip

The current article of this issue aims at defining the generic term of bone marrow edema of the femoral head as seen at MR imaging. It must be kept in mind that this syndrome should be regarded, not as a specific diagnosis, but rather as a sign of an ongoing abnormal process that involves the femoral head and/or the hip joint. We aim at emphasizing the role of the radiologists in making a specific diagnosis, starting from a non-specific finding on T1-weighted images and by focusing on ancillary findings on T2-weighted SE or fat-saturated proton-density weighted MR images.

Yersinia enterocolitica-associated generalized microinfarctions of bone and spleen in a child

We report a case of unusual extraintestinal yersiniosis in a 16-year-old girl with generalized microinfarctions of the bone and spleen. For the past 2 years she had been repeatedly admitted to our hospital with reactive arthritis, erythema nodosum and iridocyclitis of unknown aetiology. Ultrasound showed multiple round hypoechoic lesions in the spleen that were shown to have low T2 signal on MRI. MRI also showed disseminated nodular lesions of the skeleton that were low T1 and high T2 signal and demonstrated inhomogeneous contrast enhancement. The patient is currently in good health on low-dose nonsteroidal immunosuppressive therapy. This is a unique case of microinfarctions of the skeleton and spleen caused by a severe postinfectious autoimmune reaction following extraintestinal Yersinia enterocolitica infection.

Acute bone crises in sickle cell disease: the T1 fat-saturated sequence in differentiation of acute bone infarcts from acute osteomyelitis

AIM

To prove the hypothesis that acute bone infarcts in sickle cell disease are caused by sequestration of red blood cells (RBCs) in bone marrow, and to evaluate the unenhanced T1 fat-saturated (fs) sequence in the differentiation of acute bone infarction from acute osteomyelitis in patients with sickle-cell disease.

MATERIALS AND METHODS

Two studies were undertaken: an experimental study using in-vitro packed red blood cells and normal volunteers, and a retrospective clinical study of 86 magnetic resonance imaging (MRI) studies. For the experimental study containers of packed RBCs were placed between the knees of four healthy volunteers with a saline bag under the containers as an additional control, and were scanned with the pre-contrast T1-fs sequence. Signal intensity (SI) ratios were obtained for packed RBCs:skeletal muscle and packed RBCs:saline. For the clinical study, the SIs of normal bone marrow, packed RBCs, bone and/or soft-tissue lesions, and normal skeletal muscle of 74 patients (86 MRI studies) were measured using unenhanced, T1 fat-saturated MRI. The ratios of the above SIs to normal skeletal muscle were calculated and subjected to statistical analysis.

RESULTS

Fifty-one of 86 MRI studies were included in the final analysis. The ratios of SIs for normal bone marrow, packed red cells, bone infarction, acute osteomyelitis, and soft-tissue lesions associated with bone infarct, compared with normal skeletal muscle were (mean+/-SD) 0.9+/-0.2, 2.1+/-0.7, 1.7+/-0.5, 1.0+/-0.3, and 2.2+/-0.7, respectively. The difference in the ratio of SIs of bone infarcts and osteomyelitis was significant (p=0.003). The final diagnoses were bone infarction (n=50), acute osteomyelitis (n=1), and co-existent bone infarction and osteomyelitis (n=2). Seven patients who had suspected osteomyelitis underwent image-guided aspiration.

CONCLUSION

Acute bone infarcts in sickle cell disease are caused by sequestration of red blood cells in the bone marrow. The unenhanced, T1-fat-saturated sequence alone is diagnostic for acute bone infarcts. Contrast enhancement aids in the diagnosis of acute osteomyelitis. MRI can thus help in early diagnosis, specific treatment, and preventing empirical antibiotic therapy.

Gadolinium-enhanced MR Images of the Growing Piglet Skeleton: Ionic versus Nonionic Contrast Agent

PURPOSE

To determine whether there are differences in the distribution of ionic and nonionic gadolinium-based contrast agents by evaluating contrast enhancement of the physis, epiphyseal cartilage, secondary ossification center, and metaphysis in the knees of normal piglets.

MATERIALS AND METHODS

Following approval from the Subcommittee on Research Animal Care, knees of 12 3-week-old piglets were imaged at 3-T magnetic resonance (MR) imaging after intravenous injection of gadoteridol (nonionic contrast agent; n = 6) or gadopentetate dimeglumine (ionic contrast agent; n = 6). Early enhancement evaluation with gradient-echo MR imaging was quantified and compared (Student t test) by means of enhancement ratios. Distribution of contrast material was assessed and compared (Student t test) by means of T1 measurements obtained before and at three 15-minute intervals after contrast agent administration. The relative visibility of the physis, epiphyseal cartilage, secondary ossification center, and metaphysis was qualitatively assessed by two observers and compared (Wilcoxon signed rank test). Differences in matrix content and cellularity that might explain the imaging findings were studied at histologic evaluation.

RESULTS

Enhancement ratios were significantly higher for gadoteridol than for gadopentetate dimeglumine in the physis, epiphyseal cartilage, and secondary ossification center (P < .05). After contrast agent administration, T1 values decreased sharply for both agents-but more so for gadoteridol. Additionally, there was less variability in T1 values across structures with this contrast agent. Gadoteridol resulted in greater visibility of the physis, while gadopentetate dimeglumine resulted in greater contrast between the physis and metaphysis (P < .05).

CONCLUSION

The results suggest different roles for the two gadolinium-based contrast agents: The nonionic contrast medium is better suited for evaluating perfusion and anatomic definition in the immature skeleton, while the ionic contrast medium is better for evaluating cartilage fixed-charge density.

Douleurs osseuses fébriles chez l’enfant drépanocytaire : apport de l’IRM

PURPOSE

The aim of this study was to report the MRI findings that can suggest a vaso-occlusive crisis in cases of febrile osseous pain in children suffering from sickle cell disease.

MATERIALS AND METHODS

MRI (T1 and T2 weighted sequences and T1 weighted sequence with fat saturation before and after gadolinium injection) was performed in 10 children with sickle cell disease, presenting with febrile osseous pain. The diagnosis of vaso-occlusive crisis was made after fast improvement due to symptomatic treatment and negative bacteriological result.

RESULTS

MRI was abnormal in all cases. A multifocal localisation was found in 2 cases. Bone marrow abnormalities were constant. In 10 cases, high T1 and T2 signal and metaphyso-diaphysial lesions were noted. Heterogeneous medullar enhancement with "ink stain" feature was constant. Early periosteal abnormalities were noted in 8 cases with inflammatory or stratified features. Cortical thinning was found in 1 case. Soft tissue abnormalities were observed in 5 cases with inflammatory features in 4.

CONCLUSION

Multifocal synchronous localisation, medullar abnormalities resulting from hemoglobin degradation, heterogeneous enhancement, early periosteal abnormalities and associated soft tissues swelling are MRI findings suggesting acute vaso-occlusive disease.

Bone involvement in sickle cell disease

Bone involvement is the commonest clinical manifestation of sickle cell disease both in the acute setting such as painful vaso-occlusive crises, and as a source of chronic, progressive disability such as avascular necrosis. Management of these problems is often difficult because of the diagnostic imprecision of most laboratory and imaging investigations and because of the lack of evidence for most surgical procedures in sickle cell disease. This review first discusses the acute problems related to bone involvement in sickle cell disease, with particular reference to differentiating infection from infarction, and then describes the long-term effects of sickle cell disease on bone mineral density, growth, and chronic bone and joint damage.

Orbital involvement in sickle cell disease: a report of five cases and review literature

PURPOSE

To present five cases of orbital infarction in sickle cell disease and review relevant literature.

METHOD

We reviewed the hospital records of 5 patients with sickle cell disease who developed a periorbital swelling during a vaso-occlusive crisis and were managed at our hospital between April 1992 and June 2000.

RESULTS

The 5 patients (4 with homozygous sickle cell disease and 1 with sickle cell-beta-thalassaemia disease) were aged 6-15 years with a history of multiple admissions for vaso-occlusive crises. The periorbital swelling spread to the orbit in 4 cases and resulted in proptosis (2 cases), restriction of ocular motility and visual impairment. In all 4 cases, computed tomography and/or magnetic resonance imaging of the orbits showed a mass adjacent to the orbital wall. In 2 cases the mass was identified as a haematoma. Orbital wall infarction was demonstrated in 3 cases by bone/bone marrow scintigraphy. Epidural haematomas were detected by computed tomography in one case. All patients received intravenous fluids, analgesics, broad spectrum antibiotics and steroids, as well as simple or exchange transfusion, and responded well to medical management.

CONCLUSIONS

Infarction of orbital bones during vaso-occlusive crises in sickle cell disease presents acutely with a rapidly progressive periorbital swelling. Haematomas frequently complicate the condition and, along with the inflammatory swelling, may lead to orbital compression syndrome. The condition is therefore sight-threatening, and necessitates prompt diagnosis and appropriate management for resolution without adverse sequelae. Imaging techniques are invaluable in the evaluation of patients. The majority of cases resolve with conservative treatment that includes steps to combat the vaso-occlusive crisis and use of systemic steroids under antibiotic cover.

Sickle cell anemia

Sickle cell anemia (SCA) is a disease caused by production of abnormal hemoglobin, which binds with other abnormal hemoglobin molecules within the red blood cell to cause rigid deformation of the cell. This deformation impairs the ability of the cell to pass through small vascular channels; sludging and congestion of vascular beds may result, followed by tissue ischemia and infarction. Infarction is common throughout the body in the patient with SCA, and it is responsible for the earliest clinical manifestation, the acute pain crisis, which is thought to result from marrow infarction. Over time, such insults result in medullary bone infarcts and epiphyseal osteonecrosis. In the brain, white matter and gray matter infarcts are seen, causing cognitive impairment and functional neurologic deficits. The lungs are also commonly affected, with infarcts, emboli (from marrow infarcts and fat necrosis), and a markedly increased propensity for pneumonia. The liver, spleen, and kidney may experience infarction as well. An unusual but life-threatening complication of SCA is sequestration syndrome, wherein a considerable amount of the intravascular volume is sequestered in an organ (usually the spleen), causing vascular collapse; its pathogenesis is unknown. Finally, because the red blood cells are abnormal, they are removed from the circulation, resulting in a hemolytic anemia. For the patient with SCA, however, the ischemic complications of the disease far outweigh the anemia in clinical importance.

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.

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.

The diagnostic role of gadolinium enhanced MRI in distinguishing between acute medullary bone infarct and osteomyelitis

The objective of the study was to evaluate the diagnostic utility of contrast enhanced magnetic resonance imaging (MRI) for distinguishing between acute medullary bone infarct and osteomyelitis. There were 11 patients (age 6-34 years) presented to our institution between December 1994 and February 1998 with a clinical differential diagnosis of acute bone infarct versus osteomyelitis and inconclusive radiographs were imaged using MRI. All but one received i.v. gadolinium. Nine of the patients had homozygous Sickle Cell disease (SCD) and two had Systemic Lupus Erythematosus (SLE), the latter requiring chronic methylprednisolone. Osteomyelitis was confirmed either by biopsy alone or by the combination of Gallium(67) scan in conjunction with positive blood cultures and clinical resolution following antibiotics. Infarcts without osteomyelitis were confirmed either by biopsy or resolution of symptoms without antibiotic therapy. All patients had at least six months clinical follow-up. The results found that seven of nine patients with SCD had acute infarct only. One patient with SCD had osteomyelitis only. Three patients (two SLE and one SCD) had both acute-on-chronic infarcts and superimposed osteomyelitis, one with an adjacent soft tissue abscess. Accurate distinction between infarct and osteomyelitis was impossible for one patient with SLE who did not receive contrast. All other cases were correctly diagnosed prospectively based on distinct patterns of MRI contrast enhancement. In all adult patients, acute infarcts demonstrated thin, linear rim enhancement on MRI while osteomyelitis revealed more geographic and irregular marrow enhancement. Two of four cases of osteomyelitis also demonstrated subtle cortical defects with abnormal signal traversing marrow and soft tissue. The single pediatric patient demonstrated elongated, serpiginous central medullary enhancement with periostitis. We concluded that the pattern of MR contrast enhancement may allow accurate distinction between acute infarct and osteomyelitis, or recognition of osteomyelitis superimposed on bone infarction.

Update on imaging of orthopedic infections

Although the diagnosis of infection is only a small part of the orthopedist's job description, it is a important part. This article discusses the fundamentals of orthopedic infections and highlights the refinements on this topic from a radiologic perspective. In addition to reviewing the imaging appearance of musculoskeletal infections in bone and the surrounding soft tissues, we focus on the advantages and disadvantages of five imaging methods: radiography, sonography, CT, scintigraphy, and MR imaging. Finally, we review three specific situations that have garnered substantial attention in recent medical literature: chronic recurrent multifocal osteomyelitis, musculoskeletal infections in AIDS patients, and pedal infections in diabetic patients.