Acute bone marrow edema of the hip: role of MR imaging

Feasibility of bone marrow edema detection using dual-energy cone-beam computed tomography

BACKGROUND

Dual-energy (DE) detection of bone marrow edema (BME) would be a valuable new diagnostic capability for the emerging orthopedic cone-beam computed tomography (CBCT) systems. However, this imaging task is inherently challenging because of the narrow energy separation between water (edematous fluid) and fat (health yellow marrow), requiring precise artifact correction and dedicated material decomposition approaches.

PURPOSE

We investigate the feasibility of BME assessment using kV-switching DE CBCT with a comprehensive CBCT artifact correction framework and a two-stage projection- and image-domain three-material decomposition algorithm.

METHODS

DE CBCT projections of quantitative BME phantoms (water containers 100-165 mm in size with inserts presenting various degrees of edema) and an animal cadaver model of BME were acquired on a CBCT test bench emulating the standard wrist imaging configuration of a Multitom Rax twin robotic x-ray system. The slow kV-switching scan protocol involved a 60 kV low energy (LE) beam and a 120 kV high energy (HE) beam switched every 0.5° over a 200° angular span. The DE CBCT data preprocessing and artifact correction framework consisted of (i) projection interpolation onto matched LE and HE projections views, (ii) lag and glare deconvolutions, and (iii) efficient Monte Carlo (MC)-based scatter correction. Virtual non-calcium (VNCa) images for BME detection were then generated by projection-domain decomposition into an Aluminium (Al) and polyethylene basis set (to remove beam hardening) followed by three-material image-domain decomposition into water, Ca, and fat. Feasibility of BME detection was quantified in terms of VNCa image contrast and receiver operating characteristic (ROC) curves. Robustness to object size, position in the field of view (FOV) and beam collimation (varied 20-160 mm) was investigated.

RESULTS

The MC-based scatter correction delivered > 69% reduction of cupping artifacts for moderate to wide collimations (> 80 mm beam width), which was essential to achieve accurate DE material decomposition. In a forearm-sized object, a 20% increase in water concentration (edema) of a trabecular bone-mimicking mixture presented as ∼15 HU VNCa contrast using 80-160 mm beam collimations. The variability with respect to object position in the FOV was modest (< 15% coefficient of variation). The areas under the ROC curve were > 0.9. A femur-sized object presented a somewhat more challenging task, resulting in increased sensitivity to object positioning at 160 mm collimation. In animal cadaver specimens, areas of VNCa enhancement consistent with BME were observed in DE CBCT images in regions of MRI-confirmed edema.

CONCLUSION

Our results indicate that the proposed artifact correction and material decomposition pipeline can overcome the challenges of scatter and limited spectral separation to achieve relatively accurate and sensitive BME detection in DE CBCT. This study provides an important baseline for clinical translation of musculoskeletal DE CBCT to quantitative, point-of-care bone health assessment.

Differentiation between subchondral insufficiency fractures and advanced osteoarthritis of the knee using transfer learning and an ensemble of convolutional neural networks

PURPOSE

Subchondral insufficiency fractures (SIF) and advanced osteoarthritis (OA) of the knee are usually seen in conjunction with bone marrow lesions (BMLs) and their differentiation may pose a significant diagnostic challenge. We aimed to develop a convolutional neural network (CNN) ensemble which could successfully differentiate between these two entities.

MATERIALS AND METHODS

A total of 212 knees with SIF and 102 knees with advanced OA with BMLs were retrospectively included. Coronal fat suppressed PD-w images were augmented, resized and normalized, reaching a total of 1174 images. Data was used to fine-tune three ImageNet-pretrained CNNs (VGG-16, InceptionV3 and Inception-ResNet-V2). Agreement of at least two networks was recorded as the decision of the network ensemble. Ensemble performance was compared to that of two MSK radiologists on the validation set. Receiver operating characteristics (ROC) curves and the respective areas under the curve (AUC) were used to evaluate human and machine performance.

RESULTS

InceptionV3 achieved the highest AUC (93.68%) and VGG-16 the lowest AUC (82.18%) among individual CNNs. CNN ensemble achieved the highest overall performance with an AUC of 95.97%. The first of the two MSK radiologists achieved a performance similar to the ensemble, reaching an AUC of 91.95%. The second radiologist achieved lower AUC of 82.76% which was lower than both the other specialist and the ensemble (P < 0.001).

CONCLUSION

A CNN ensemble was highly accurate in differentiating between SIF and OA, achieving a higher or equal performance to MSK radiologists.

Transient regional osteoporosis of the hip with extensive bone marrow edema (BME): Dramatic improvement after three months of Alendronate therapy

Transient osteoporosis of the hip, also termed transient bone marrow edema, is a painful condition often occurring after trivial trauma. It can be diagnosed with MRI in patients whose radiographs are negative or inconclusive. In this case report we describe a 39-year-old female patient with this rare entity, who was successfully treated with oral Alendronate, active vitamin D and calcium supplementation combined with avoiding of weight bearing on the affected hip. She improved clinically within three months and on contrast enhanced MRI studies, as performed before and after treatment, complete regression of bone marrow edema was shown already after three months of treatment. The literature was reviewed regarding the pathophysiology of transient osteoporosis of the hip and the beneficial effects of Alendronate in this domain. The report is important because it will increase the awareness among clinicians and radiologists about this entity, as in neglected cases transient regional osteoporosis of the hip may progress to avascular necrosis with complete loss of hip function.

How We Manage Bone Marrow Edema-An Interdisciplinary Approach

Bone marrow edema (BME) is a descriptive term for a common finding in magnetic resonance imaging (MRI). Although pain is the major symptom, BME differs in terms of its causal mechanisms, underlying disease, as well as treatment and prognosis. This complexity together with the lack of evidence-based guidelines, frequently makes the identification of underlying conditions and its management a major challenge. Unnecessary multiple consultations and delays in diagnosis as well as therapy indicate a need for interdisciplinary clinical recommendations. Therefore, an interdisciplinary task force was set up within our large osteology center consisting of specialists from internal medicine, endocrinology/diabetology, hematology/oncology, orthopedics, pediatrics, physical medicine, radiology, rheumatology, and trauma surgery to develop a consenus paper. After review of literature, review of practical experiences (expert opinion), and determination of consensus findings, an overview and an algorithm were developed with concise summaries of relevant aspects of the respective underlying disease including diagnostic measures, clinical features, differential diagnosis and treatment of BME. Together, our single-center consensus review on the management of BME may help improve the quality of care for these patients.

[Differential diagnoses of osteonecrosis of large joints]

Subchondral insufficiency fractures and idiopathic bone marrow edema syndrome are the most important differential diagnoses to be distinguished from osteonecrosis because they have a deviating and as a rule more favorable prognosis and also different therapeutic strategies. Osteochondritis dissecans represents a different entity in many respects, which should not be confused or unified with osteonecrosis. Based on recent knowledge intractable subchondral insufficiency fractures may be the underlying cause of rapidly destructive osteoarthritis at least in some cases. Septic involvement of bone and joints can eo ipso cause severe articular damage due to direct destruction but also secondary to septic vascular occlusion resulting in septic osteonecrosis. Whereas bone marrow infiltrating systemic diseases and the therapeutic regimens can lead to osteonecrosis, bone tumors or tumor-like diseases, rarely pose a differential diagnostic problem with respect to the differentiation from osteonecrosis.

Painful transient edema in the tibial diaphysis: the challenges and the essence of biopsy in treatment

BACKGROUND

Some patients experience a non-traumatic pain in the tibial diaphysis similar to that in the clinical and radiological findings of a tumor, an infection or a stress fracture and cannot be definitively diagnosed even after biopsy. In this study, our aim was to exhibit the challenges in the diagnosis of this patient group and to evaluate this type of patients with a limited population in the literature.

METHODS

Eighteen extremities of 16 patients, whose complaints of non-traumatic pain in the tibial diaphysis were evaluated by our tumor council and T2-weighted MR scans of the medullary bone had shown hyperintense signal changes or tumor-like appearances, were evaluated with histological, radiological, and clinical results.

RESULTS

Lesions were detected in 18 extremities of the 16 patients (seven males, nine females; mean age 23 [range 7 to 51] years). Four of the lesions were in the right tibial diaphysis, ten were in the left, and two were bilateral. Laboratory findings of the patients were normal. Based on the decision of the tumor council, biopsy was performed on 12 patients. All patients' complaints were gone and MRI findings decreased during the follow-up period. The complaints of the three patients who did not have a biopsy decreased after a mean period of three months.

CONCLUSIONS

Medullary stress syndrome has been reported in the literature in various forms and in a limited number of cases, including longitudinal stress fracture and transient medullary edema of the bone. In light of our findings, we deduced that biopsy of the diaphyseal lesions in this patient group is essential and that the complaints of this patient group declined in the earlier term in comparison to the patients who were not performed biopsy.

MRI of the hip: current concepts on bone marrow oedema

Bone marrow oedema (BME) is commonly found in hip MR imaging. BME is a nonspecific finding which can be related to a wide variety of diseases. However, there are cases where its existence or its pattern can narrow the differential or even point to a specific diagnosis. Therefore, deep understanding of its pathophysiology is of utmost importance for clinicians and radiologists in order to avoid diagnostic pitfalls. We hereby present currently established knowledge on BME related to adult hip pathology, aiming to raise physicians' suspicion and to highlight that it is mandatory to combine specific imaging patterns with the history, clinical and laboratory findings in order to achieve accurate diagnosis.

Transient Bone Marrow Edema Syndrome versus Osteonecrosis: Perfusion Patterns at Dynamic Contrast-enhanced MR Imaging with High Temporal Resolution Can Allow Differentiation

Purpose To prospectively evaluate the perfusion patterns at quantitative dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging of transient bone marrow edema syndrome (TBMES) and avascular osteonecrosis. Materials and Methods Institutional review board approval and written informed consent were obtained. Thirty-two patients (21 men, 11 women; mean age, 48 years; 26 hips, 10 knees) underwent conventional MR imaging and a dynamic contrast-enhanced three-dimensional spoiled gradient-echo sequence at 3 T. Parameter maps for mean transit time (MTT) and plasma flow (PF) were evaluated qualitatively and quantitatively. Differences in perfusion patterns were analyzed by using the Fisher exact test. Regions of interest were drawn in areas of high PF and long MTT on each parametric map. Mean, median, standard deviation, minimum, and maximum values were determined. TBMES and osteonecrosis were compared statistically by using the Mann-Whitney U and Wilcoxon signed-rank tests, with a P value of less than .05 considered indicative of a significant difference. Results Nineteen joints with TBMES and 17 joints with osteonecrosis were evaluated. TBMES joints showed a subchondral elongated area of high PF and low MTT that was surrounded by an area of long MTT and low PF. Osteonecrosis joints showed a subchondral area with low or no detectable PF and MTT adjacent to the joint surface, which was surrounded by a rim of high PF and intermediate MTT. Patterns for TBMES and osteonecrosis did not overlap. A significant difference (P < .001) in PF in the immediate subchondral area was found between TBMES and osteonecrosis; in joints with osteonecrosis, this was comparable to background noise, and therefore, could not be quantified. In the circumscribed rim of high PF and intermediate MTT, which was only found in joints with osteonecrosis, mean ± standard deviation PF was 18.9 mL/100 mL per minute ± 11.0 and mean MTT was 213.3 seconds ± 56.8. No significant difference between TBMES and osteonecrosis was found for MTT (P = .09) and PF (P = .75) in the surrounding area. Conclusion Parameter maps derived at dynamic contrast-enhanced MR imaging with high temporal resolution can allow differentiation of osteonecrosis from TBMES in hip and knee joints. ^© RSNA, 2016 Online supplemental material is available for this article.

Simultaneous Bilateral Transient Osteoporosis of the Hip without Pregnancy

Transient osteoporosis of the hip (TOH) is a rare disorder characterized by acute severe coxalgia and temporary osteopenia in the proximal femur. Although most cases were unilateral or staged bilateral TOH, some authors reported that the pregnant patients simultaneously had TOH in their bilateral hips. However, there has been no report of simultaneous bilateral TOH in the patient without pregnancy. A 25-year-old Japanese woman without pregnancy had acute simultaneous bilateral hip pain. Plain X-ray of the bilateral hips did not show a periarticular osteopenia. However, magnetic resonance image obtained one week after the onset demonstrated increased T2-weighted signal intensity and decreased T1-weighted signal intensity in the bilateral femoral heads. She was treated conservatively, and follow-up magnetic resonance image at seven weeks after the onset returned to normal bone marrow signal intensity. Her bilateral coxalgia subsided gradually. At one year after the onset, she had no sign of symptomatic flair. Our experience with this case indicates that recognizing the possibility of simultaneous bilateral TOH is important unless the patient is pregnant, and magnetic resonance image is predictable test to make a diagnosis of TOH, even in the absence of abnormal finding on plain X-ray.

Osteonecrosis detected by whole body magnetic resonance in patients with Hodgkin Lymphoma treated by BEACOPP

OBJECTIVES

The purpose of our retrospective review of prospectively acquired Whole Body Magnetic Resonance (WB-MRI) scans was to assess the incidence of osteonecrosis in patients who received different chemotherapies.

METHODS

We evaluated the WB-MRI scans performed on 42 patients with Hodgkin Lymphoma treated by three chemotherapy regimens (6ABVD, 2ABVD + 4BEACOPP, 2ABVD + 8BEACOPP), excluding patients with the main risk factors for osteonecrosis.

RESULTS

Six out of seven patients (86 %) who received eight BEACOPP and one out of five patients (20 %) treated by four BEACOPP presented osteonecrosis, with a statistically significant difference of frequency between the two groups of patients (p < 0.05); no injury has been reported in patients treated by only ABVD. Among a total of 48 osteonecrotic lesions observed, 48 % were detected in the knee; multifocal osteonecrosis were detected in six out of seven patients (86 %).

CONCLUSIONS

The development of osteonecrosis is strictly related to the chemotherapy protocol adopted and the number of cycles received, with a strong correlation between the dose of corticosteroids included in the BEACOPP scheme and this complication. WB-MRI can be considered as a helpful tool that allows detecting earlier osteonecrotic lesions in patients treated with corticosteroids.

KEY POINTS

• Osteonecrosis is a possible complication of patients with Lymphoma treated by chemotherapy. • Osteonecrosis is related to the corticosteroids included within the BEACOPP protocol. • WB-MRI allows detecting osteonecrotic lesions in patients treated with corticosteroids.

Pitfalls in whole body MRI with diffusion weighted imaging performed on patients with lymphoma: What radiologists should know

The technological advances in radiological imaging and the relevance of a diagnostic tool that may reduce radiation-induced long-term effects have led to a widespread use of whole body magnetic resonance imaging (WB-MRI) with diffusion weighted imaging for oncologic patients. A lot of studies demonstrated the feasibility and reliability of WB-MRI as an alternative technique for lymphoma staging and response assessment during and after treatment. In this paper, taking advantage of our 2years of experience using WB-MRI for lymphoma, we discuss the main pitfalls and artifacts radiologists should know examining a WB-MRI performed on this typology of patients in order to avoid images misinterpretation.

[Bone marrow edema and joint injuries]

BACKGROUND

The development of bone marrow edema in body regions adjacent to joints can have many causes and a differentiation is not possible using magnetic resonance imaging (MRI).

DEFINITION

Bone marrow edema is not necessarily an indication for microfractures. The definition of bone marrow edema is a purely radiological description. There is no uniform classification of bone marrow edema. The clinical significance, therapy and course are heterogeneous; therefore, there are no uniform recommendations for therapy.

DIAGNOSTICS

A bone marrow edema visible in MRI does not always lead to certain inferences regarding the pathogenesis. In order to be able to detect fractures it is necessary to carry out a biopsy and a histological examination.

CONCLUSION

The interpretation of MRI results and the derivation of a therapy in every case need a balanced assessment of the MRI results, medical history, clinical investigations and clinical symptoms.

Fast sequences MR imaging at the investigation of painful skeletal sites in patients with hip osteonecrosis

BACKGROUND

Multiple osteonecrotic foci can be clinically silent when located in metaphyses and becomes painful when it affects juxta-articular areas. The purpose of this study was to assess the value of fast MR imaging to depict the underlying pathology in cases with skeletal pain other than the already diagnosed hip osteonecrosis.

METHODS/DESIGN

Between 2008 and 2013, 49 patients with already diagnosed hip osteonecrosis reported symptoms of deep skeletal pain in an anatomical site different from the affected hip joint. All patients after thorough history & clinical examination underwent evaluation with x-rays and a single fat suppressed sequence with MR Imaging applying either T2-w TSE or STIR-TSE at the painful site. False positive and false negative findings were recorded for the conventional x-rays and compared to MRI.

DISCUSSION

Forty four (89.8%) patients were positive for osteonecrotic lesions in this study and 76 symptomatic osteonecrosis lesions were revealed at 14 distinct anatomic sites. The agreement between the x-ray findings and the MR imaging regarding osteonecrosis was 46.9%. Plain x-rays showed 43.4% sensitivity, 100% specificity, 100% positive predictive value and 10.4% negative predictive value. Fast MR imaging with fat suppressed sequences is necessary and adequate as a single method for the investigation of painful skeletal sites in patients with already diagnosed hip osteonecrosis. It allows early diagnosis of the potentially debilitating multiple juxta-articular lesions and consequently their prompt management.

[Aseptic osteonecrosis in children and adolescents]

BACKGROUND

Aseptic osteonecrosis (AO) in children and adolescents has been described in all parts of the skeleton. The disease is presumed to be caused by local blood circulation disorders, the reasons for which are multifactorial and occur more often in times of stronger growth intensity.

DISEASE SEQUELAE

The disease leads to bone catabolism which can affect the epiphyses, metaphyses, apophyses, carpal and tarsal bones of the hands and feet. The more stretched the form alteration of the bone at the end of the diseases is, the earlier arthritic alterations occur due to the incongruence of the corresponding joint partner. If a growth plate is affected, a growth disorder can be the result.

DIAGNOSTICS AND THERAPY

The diagnostics and therapeutic measures are oriented to the site and extent of the disease and the age of the child. For early forms of AO magnetic resonance imaging (MRI) is the imaging method of choice. In recent years the medicinal therapy of AO has been described as an additional option. The disease lasts at least several months up to years and more commonly affects boys than girls with the exception of necrosis of the foot tarsals.

CONCLUSION

The early diagnosis and immediate initiation of adequate therapy which must take the age and stage of the disease into consideration, can reduce a possible joint destruction. Prostaglandin therapy, as an off label use, leads to a reduction of pain and improvement in mobility.

Evaluation of transient osteoporosis of the hip in magnetic resonance imaging

Transient osteoporosis is a relatively rare condition of unknown etiology that causes temporary bone loss. The syndrome is characterized by self-limited course and spontaneous resolution after 6 to 12 months. The pathogenesis of transient osteoporosis is not fully understood but several hypotheses that have been proposed include trauma, neurovascular dysfunction and transient hyperemia. Clinical manifestations include sudden onset of pain in the hip that usually worsens with weight bearing and leads to functional disability involving the affected extremity. Radiographs are frequently unremarkable, but may reveal periarticular osteopenia 3-6 weeks after the onset of clinical symptoms. There is no radiographic evidence of demineralization during the early phase of syndrome, as a result advanced imaging is required. Magnetic resonance imaging is the most sensitive and predictable test for an early diagnosis and monitoring of disease progression.

Accuracy and limitations of diagnostic methods for avascular necrosis of the hip

INTRODUCTION

Femoral head avascular necrosis (FHAVN) is the result of irreversible anoxia of the subchondral bone. The death of bone cells can cause articular collapse and pain, and in turn usually leads to degenerative arthritis. FHAVN is a common disorder, affecting mainly young male adults. Reliability, accuracy and prognostic value of any classification system are important in evaluation and treatment of FHAVN.

AREAS COVERED

Although in the past, scintigraphy and CT and more recently PET have been used for diagnosing AVN, currently the most important imaging methods included in the most widely used classification systems, consist of radiographs and magnetic resonance imaging (MRI). The latter is used in major classification systems for early detection (pre-radiographic stage) of FHAVN and for assessing lesion size and location before collapse of the articular surface occurs. The purpose of this review is to present the current data regarding the accuracy of the X-rays and MRI in diagnosing, monitoring and postoperative evaluation of FHAVN.

EXPERT OPINION

The author's opinion is that MRI may contribute to improve staging, investigate radiologically occult collapse, depict other causes of disability and pain, assess prognosis and evaluate treatment. Newer MRI techniques, such as diffusion-weighted imaging and perfusion imaging, have not yet provided additional and clinically useful information.

Transient osteoporosis of the hip, complete resolution after treatment with alendronate as observed by MRI description of eight cases and review of the literature

Transient osteoporosis of the hip (TOH), also referred to as transient bone marrow edema syndrome, is most common in middle-aged men and often after trivial trauma or sport-related injuries. Diagnosis is usually made by eliminating other possible causes of hip pain. Magnetic resonance imaging (MRI) plays an important role in diagnosis and demonstrates a typical pattern of bone marrow edema (BME) in the form of diffuse low signal on T1-weighted images and high signal on T2 fat-suppressed or short T1 inversion recovery images. No consensus exists about the management of TOH, as it may progress to avascular necrosis. We describe eight cases of TOH treated with alendronate resulting in improvement of pain and function and complete resolution of BME on MRI. The literature is reviewed regarding TOH and the relationship with bone marrow edema syndrome, avascular necrosis of the hip, and regional migratory osteoporosis. To our knowledge, this is the first report describing the improvement of this condition after of alendronate with documented radiological improvement on follow-up MRI.

Use of gamma correction pinhole bone scans in trauma

(99m)Tc-hydroxydiphosphonate (HDP) bone scanning is a classic metabolic nuclear imaging method and the most frequently performed examination. Clinically, it has long been cherished as an indispensable diagnostic screening tool and for monitoring of patients with bone, joint, and soft tissue diseases. The HDP bone scan, the pinhole scan in particular, is known for its ability to detect increased, decreased, or defective tracer uptake along with magnified anatomy. Unfortunately, however, the findings of such uptake changes are not specific in many traumatic bone disorders, especially when lesions are minute and complex. This study discusses the recently introduced gamma correction pinhole bone scan (GCPBS), emphasizing its usefulness in the diagnosis of traumatic bone diseases including occult fractures; cervical sprains; whiplash injury; bone marrow edema; trabecular microfractures; evident, gaping, and stress fractures; and fish vertebra. Indeed, GCPBS can remarkably enhance the diagnostic feasibility of HDP pinhole bone scans by refining the topography, pathologic anatomy, and altered chemical profile of the traumatic diseases in question. The fine and precise depiction of anatomic and metabolic changes in these diseases has been shown to be unique to GCPBS, and they are not appreciated on conventional radiographs, multiple detector CT, or ultrasonographs. It is true that MR imaging can portray proton change, but understandably, it is a manifestation that is common to any bone disease.

Transient bone marrow edema of the foot and ankle and its association with reduced systemic bone mineral density

BACKGROUND

Transient bone marrow edema in the foot and ankle is an uncommon condition that should be distinguished from early avascular necrosis, stress fracture, or bone bruise. The diagnosis is based on the clinical presentation of pain with weightbearing without a history of trauma, combined with typical findings on magnetic resonance imaging. The etiology is not known, but recent case reports have suggested a possible link to systemic osteoporosis. This study examined the relationship between transient bone marrow edema of the foot and ankle and low systemic bone mineral density.

MATERIAL AND METHODS

Over a period of 2 years, ten patients (eight women and two men) who were referred to our foot and ankle clinic were diagnosed as having transient bone marrow edema. Their mean age was 59 years. All underwent dual energy X-ray absorptiometry (DEXA) scan and were tested for serum vitamin D levels. The patients were treated with either a controlled ankle motion (CAM) walker or a stiff-soled postoperative shoe and all recovered in 5 to 10 months.

RESULTS

Four patients were found to have osteoporosis and five had osteopenia. Only one patient had normal bone density. Serum vitamin D levels were low in nine patients, and normal in one.

CONCLUSION

Our study found a strong association with transient bone marrow edema in the foot and ankle and low systemic bone mineral density, which appears to be due to a vitamin D deficiency. We recommend that, when TBME is diagnosed, patients should be referred for assessment and treatment of their bone mineral density.

Role of MRI in hip fractures, including stress fractures, occult fractures, avulsion fractures

MR imaging plays a vital role in the diagnosis and management of hip fractures in all age groups, in a large spectrum of patient groups spanning the elderly and sporting population. It allows a confident exclusion of fracture, differentiation of bony from soft tissue injury and an early confident detection of fractures. There is a spectrum of MR findings which in part is dictated by the type and cause of the fracture which the radiologist needs to be familiar with. Judicious but prompt utilisation of MR in patients with suspected hip fractures has a positive therapeutic impact with healthcare cost benefits as well as social care benefits.

Bilateral transient bone marrow edema or transient osteoporosis of the knee in pregnancy

Transient osteoporosis or transient bone marrow edema is an uncommon self-limiting condition of unknown etiology. The most commonly affected joint is the hip, followed by the knee, ankle, and the foot. Simultaneous involvement of both hips has been reported exclusively in pregnant women. Bilateral knee involvement during pregnancy seems to be extremely rare. We present a case of bilateral transient bone marrow knee edema during pregnancy with complete resolution of symptoms and radiological findings after 10 months.

Diagnostic performance of MR imaging in the assessment of subchondral fractures in avascular necrosis of the femoral head

OBJECTIVE

A prospective study was conducted to determine the accuracy of routine magnetic resonance (MR) imaging in correctly identifying subchondral fracture in avascular necrosis of the femoral head without apparent focal collapse on standard radiographs.

MATERIALS AND METHODS

Spiral computed tomography (CT) with coronal and sagittal reformations and routine MR imaging with spin-echo T1WI and fat-suppressed spin-echo T2WI coronal, axial, and sagittal images were performed in 28 hips of 25 patients (M/F = 20:5; age 16-76 years) suffering from early-stage avascular necrosis of the femoral head on standard radiographs. The MR images were reviewed by a musculoskeletal radiologist and a general radiologist in blinded fashion. Using CT as the standard of reference, the accuracy of MR imaging in diagnosing subchondral fractures in avascular necrosis was evaluated.

RESULTS

When the diagnoses of the two readers were compared with each other, only 16 of the 28 diagnoses (57.5%) agreed. Seventeen of the 28 MR imaging readings (60.7%) made by the musculoskeletal radiologist and 15 of the 28 (53.5%) made by the general radiologist agreed with those of the CT standard. False-positive diagnosis (that is, diagnosis of fracture when no fracture could be seen on CT) was more common than false-negative diagnosis.

CONCLUSIONS

The accuracy of routine MR imaging in the evaluation of subchondral fracture is not satisfactory. False-positive diagnosis is not uncommon. Interpretation of routine MR imaging readout should be guarded.

Bone marrow edema syndrome

Bone marrow edema syndrome (BMES) refers to transient clinical conditions with unknown pathogenic mechanism, such as transient osteoporosis of the hip (TOH), regional migratory osteoporosis (RMO), and reflex sympathetic dystrophy (RSD). BMES is primarily characterized by bone marrow edema (BME) pattern. The disease mainly affects the hip, the knee, and the ankle of middle-aged males. Many hypotheses have been proposed to explain the pathogenesis of the disease. Unfortunately, the etiology of BMES remains obscure. The hallmark that separates BMES from other conditions presented with BME pattern is its self-limited nature. Laboratory tests usually do not contribute to the diagnosis. Histological examination of the lesion is unnecessary. Plain radiographs may reveal regional osseous demineralization. Magnetic resonance imaging is mainly used for the early diagnosis and monitoring the progression of the disease. Early differentiation from other aggressive conditions with long-term sequelae is essential in order to avoid unnecessary treatment. Clinical entities, such as TOH, RMO, and RSD are spontaneously resolving, and surgical treatment is not needed. On the other hand, early differential diagnosis and surgical treatment in case of osteonecrosis is of crucial importance.

Acute nontraumatic adult knee pain: the role of MR imaging

Acute nontraumatic pain in the adult knee can be seen in many settings, such as transient bone marrow oedema syndrome (TBMOS), regional migratory osteoporosis (RMO), spontaneous osteonecrosis (SONK) and insufficiency fractures. Early differentiation among them is crucial to avoid unnecessary treatment. TBMOS and RMO are considered to be self-limiting conditions without longterm sequelae. On the other hand, the clinical course of SONK is thought to be dependent on the size of osteonecrosis. Recent data suggest the term SONK is misleading one and should be replaced. Insufficiency fractures may demonstrate a similar clinical syndrome without a history of a single traumatic injury. The imaging pathway for knee pain has evolved considerably with the advent of magnetic resonance (MR) imaging, which is very sensitive in the early depiction of bone marrow oedema. Therefore, in patients with acute nontraumatic knee pain whose radiographs are negative or inconclusive, MR imaging is the method of choice for further evaluation. This article discusses the potential aetiologies and reviews MR imaging findings of the most common disorders afflicting the subchondral knee-joint area.

Transient osteoporosis of the hip

Transient osteoporosis of the hip is an uncommon cause of hip pain, mostly affecting healthy middle-aged men and also women in the third trimester of pregnancy. We present a case of transient osteoporosis of the hip in a 33-year-old non-pregnant female patient. This case highlights the importance of considering a diagnosis of transient osteoporosis of the hip in patients who present with hip pain.

Transient osteoporosis

Transient osteoporosis is characterized primarily by bone marrow edema. The disease most commonly affects the hip, knee, and ankle in middle-aged men. Its cause remains unknown. The hallmark that separates transient osteoporosis from other conditions presenting with a bone marrow edema pattern is its self-limited nature. Laboratory tests usually do not contribute to the diagnosis. Plain radiographs may reveal regional osseous demineralization. Magnetic resonance imaging is used primarily for early diagnosis and monitoring disease progression. Early differentiation from more aggressive conditions with long-term sequelae is essential to avoid unnecessary treatment. Clinical entities such as transient osteoporosis of the hip and regional migratory osteoporosis are spontaneously resolving conditions. However, early differential diagnosis and surgical treatment are crucial for the patient with osteonecrosis of the hip or knee.

Regional migratory osteoporosis in the knee: MRI findings in 22 patients and review of the literature

OBJECTIVE

Acute non-traumatic bone marrow edema (BME) in the knee is a common clinical problem. The aim of the present study is to present the MR imaging findings of the uncommon transient migratory pattern of this syndrome.

MATERIALS AND METHODS

Twenty-two patients (21 men, 1 woman, age range 35-73 years, mean 49.4+/-7.6) who presented with pain in the knee joint (ranging from 2 weeks to 6 months) and BME in the MR imaging examination, were included in the study. In all cases, the knee joint BME was either preceded or followed by another site of BME in the same or another joint. All patients were studied with plain X-rays and MR imaging at presentation and with MR imaging after resolution of symptoms.

RESULTS

The eight patients with initial involvement in the knee showed migration either intra-articularly (5), or/and in the contralateral knee (2) and only 1 case showed migration to the ipsilateral hip joint. In two patients the BME shifted from the hip first to the foot and then to the knee. The median migration period was 4 months for the second involvement in all patients and 3 months for the third involvement (10 patients).

CONCLUSIONS

The present study reports the largest series of patients with regional migratory osteoporosis involving the knee. In most of the cases, shifting of BME remains in the joint or moves to the contralateral knee. In only one case the BME shifted from the knee elsewhere. All lesions were transient.

Acute non-traumatic marrow edema syndrome in the knee: MRI findings at presentation, correlation with spinal DEXA and outcome

PURPOSE

The aim of the study was to present the MRI findings of non-traumatic edema-like lesions presented acutely in the adult knee and to correlate them with the 3-year outcome and the bone mineral density (BMD) in the spine.

MATERIALS AND METHODS

Ninety-eight patients (40 men, 58 women, mean age 60.1+/-11 years, age range 27-82 years), were followed up clinically as well as with MR imaging, when indicated, for at least 3 years. Patients were classified according to presentation in 3 groups (A: bone marrow edema (BME), B: BME and subchondral fracture, C: BME and articular collapse) and according to outcome in 2 groups (A: reversible BME, B: articular collapse). BMD measurements of the spine were carried out in males over 70 and females over 60 years old using DEXA.

RESULTS

The isolated BME pattern was observed in 64.3% (Group A), subchondral fractures without articular collapse in 11.2% (Group B) and articular collapse in 24.5% (Group C). Significant differences were found among the 3 groups at presentation, regarding the age, sex, BMD, affected area and duration of symptoms prior to imaging (p<0.05). Localization of the lesions in the weight-bearing areas of the knee was shown in 100% of C, in 90.9% of B and in 50.8% of A. The duration of symptoms prior to imaging was longer in C (7.6+/-2.8m) than in A (2.5+/-1.7m) and B (4.0+/-3.2m) (p<0.05). Group B progressed to articular collapse in 45.5%, the rest demonstrating a favourable outcome. Group C showed clinical improvement in 75% and persistent symptoms that required knee arthroplasty in 25% of cases. Articular collapse was the final outcome in 29.6% and transient BME in 70.4% of patients. These two groups showed significant differences regarding the age (p approximately 0), sex (p=0.002), low BMD (p=0.004), affected area (p approximately 0), presence of subchondral sparing (p approximately 0), duration of symptoms prior to imaging (p approximately 0), time from onset of symptoms to the final outcome (p approximately 0) and need for arthroplasty (p=0.001). None of the patients with transient BME syndrome eventually progressed to articular collapse.

CONCLUSION

In the context of acute non-traumatic knee BME, the age and sex of the patient, the duration of symptoms before imaging, the pattern of BME, and the BMD appear to correlate with the final outcome.

Bone marrow edema syndromes of the hip: MRI features in different hip disorders

The objectives of this study were to describe the essential magnetic resonance imaging (MRI) features of bone marrow edema syndromes affecting the hip joint. In addition, to evaluate the role of MRI in the assessment of hip joint involvement in different clinical settings that may share similar clinical findings. Thirty-four patients who complained of hip pain were studied consecutively. Of these, 21 were men (61.8%) and 13 were women (38.2%). After clinical assessment of possible hip disease, plain radiograph and MRI study of both hips were performed. The literature was searched using keywords: bone marrow edema, hip, and MRI. All patients had antalgic gait and limping. Initial clinical examination revealed painful limited internal and external rotation of the affected hip/hips suspect for hip disease. Unilateral hip involvement was identified in 31 patients (91.2%), and bilateral hip involvement was found in three patients (8.8%), with a total of 37 hips evaluated by MRI. The final diagnoses in our patients were: reactive arthritis (1), transient osteoporosis (7), avascular necrosis (10), osteoarthritis (2), tuberculous arthritis (4), septic arthritis (2), osteomyelitis (2), sickle cell anemia (2), lymphocytic leukemia (1), and femoral stress fracture (3). Bone marrow edema affecting the hip is neither a specific MR imaging finding nor a specific diagnosis and may be encountered in a variety of hip disorders due to different etiologies. MR imaging is the modality of choice when clinical examination is suspect for hip disease and plain radiographs are normal or equivocal. Early diagnosis and treatment is important in many of the disorders. The literature is reviewed regarding bone marrow edema of the hip.

Femoral head osteonecrosis: volumetric MRI assessment and outcome

Effective treatment of femoral head osteonecrosis (FHON) requires early diagnosis and accurate assessment of the disease severity. The ability to predict in the early stages the risk of collapse is important for selecting a joint salvage procedure. The aim of the present study was to evaluate the outcome in patients treated with vascularized fibular grafts in relation to preoperative MR imaging volumetry. We studied 58 patients (87 hips) with FHON. A semi-automated octant-based lesion measurement method, previously described, was performed on the T1-w MR images. The mean time of postoperative follow-up was 7.8 years. Sixty-three hips were successful and 24 failed and converted to total hip arthroplasty within a period of 2-4 years after the initial operation. The rate of failures for hips of male patients was higher than in female patients. The mean lesion size was 28% of the sphere equivalent of the femoral head, 24+/-12% for the successful hips and 37+/-9% for the failed (p<0.001). The most affected octants were antero-supero-medial (58+/-26%) and postero-supero-medial (54+/-31%). All but postero-infero-medial and postero-infero-lateral octants, showed statistically significant differences in the lesion size between patients with successful and failed hips. In conclusion, the volumetric analysis of preoperative MRI provides useful information with regard to a successful outcome in patients treated with vascularized fibular grafts.

Osteonecrosis of the femoral head: etiology, imaging and treatment

Osteonecrosis of the femoral head is a disabling clinical entity affecting young adults that usually leads to destruction of the hip joint. A high index of suspicion is necessary for the diagnosis due to the insidious onset of the bone infarcts and the lack of specific clinical signs at the early stages. Many etiology-associated factors have been identified reducing thus the number of idiopathic cases. A number of joint salvaging treatment options are available if early diagnosis can be achieved. MR imaging has been proved to be a highly accurate method both for early diagnosis and for staging of the disease. Replacement of the hip joint is the last resort for pain relief and function, although non-desirable because of the young age of the affected population.

Imaging of the hip in patients with rheumatic disorders

Hip joint abnormalities are commonly encountered in patients with rheumatic disorders. Although conventional radiography remains the mainstay for diagnosis of joint damage and subsequent follow-up, magnetic resonance imaging and, to a lesser extent, ultrasound have afforded the ability to detect early signs of articular involvement (i.e., synovitis and bone erosions), and to assess disease activity in treated patients. In more advanced stages of rheumatic disorders, magnetic resonance imaging and ultrasound are both useful in assessing paraarticular involvement (i.e., bursitis and synovial cysts).