A clinicopathologic study of transient osteoporosis of the hip

Presence of subchondral fracture in cases diagnosed as transient osteoporosis of the hip: a retrospective independent reader-based study

OBJECTIVE

Transient osteoporosis of the hip (TOH) is an uncommon, typically self-limited diagnosis of uncertain etiology. We hypothesize that TOH represents an underlying subchondral fracture, and a discrete fracture line can often be detected on high-resolution MRI.

MATERIALS AND METHODS

A retrospective PACS query identified patients meeting imaging criteria for TOH with intense bone marrow edema (BME) in the femoral head on MRI. Those with poor quality studies, other underlying pathologies, or antecedent trauma were excluded. Three musculoskeletal radiologists independently reviewed each case for presence of a definite subchondral fracture line on small field of view (FOV) MR images of the affected hip. Extent of BME, reciprocal acetabular BME, and joint effusion size were also recorded. Binomial logistic regression was performed to determine statistically significant predictors of subchondral fracture.

RESULTS

Fifty patients met inclusion criteria (29 females, 0 pregnant). Mean age was 62±12 years (range 35-84). Average duration of symptoms before MRI was 102±135 days. Ten patients had bone densitometry within 2 years of MRI, six demonstrating osteopenia or osteoporosis. Subchondral fractures were unanimously identified in 44/50 (88%). Interclass correlation coefficient with absolute agreement was 0.73, 95% CI (0.57-0.84), indicating near-excellent agreement. Most cases demonstrated a large joint effusion (23/50, 46%) and acetabular BME (31/50, 62%). Increasing size of joint effusion was a statistically significant predictor of subchondral fracture (p=0.05), with 6.9 higher odds. There was a strong correlation with osteopenia/osteoporosis and fracture (p<0.001).

CONCLUSION

Discrete subchondral fractures were identified unanimously on small FOV imaging in the majority of TOH cases.

Pathological femoral neck fracture in a male patient due to non-simultaneous bilateral transient hip osteoporosis: A case report: Statements and Declarations

We report a case of a 31-year-old man who developed a non-simultaneous bilateral transient hip osteoporosis (THO) complicated with an atraumatic undisplaced pathological femoral neck fracture (FNF) of his left hip. He was successfully treated with internal fixation on the left hip, and a follow-up Magnetic Resonance Imaging evidenced satisfactory resolution on the right side. Diagnosis and management of THO are usually challenging as symptoms before pathological FNFs might be misdiagnosed. This case highlights the importance of suspecting pathological FNFs when pain persists despite conservative treatment. Finally, surgical treatment is strongly recommended if a pathological FNF is confirmed.

Level of evidence

Level IV.

Deep Learning for the Differential Diagnosis between Transient Osteoporosis and Avascular Necrosis of the Hip

Differential diagnosis between avascular necrosis (AVN) and transient osteoporosis of the hip (TOH) can be complicated even for experienced MSK radiologists. Our study attempted to use MR images in order to develop a deep learning methodology with the use of transfer learning and a convolutional neural network (CNN) ensemble, for the accurate differentiation between the two diseases. An augmented dataset of 210 hips with TOH and 210 hips with AVN was used to finetune three ImageNet-trained CNNs (VGG-16, InceptionResNetV2, and InceptionV3). An ensemble decision was reached in a hard-voting manner by selecting the outcome voted by at least two of the CNNs. Inception-ResNet-V2 achieved the highest AUC (97.62%) similar to the model ensemble, followed by InceptionV3 (AUC of 96.82%) and VGG-16 (AUC 96.03%). Precision for the diagnosis of AVN and recall for the detection of TOH were higher in the model ensemble compared to Inception-ResNet-V2. Ensemble performance was significantly higher than that of an MSK radiologist and a fellow (P < 0.001). Deep learning was highly successful in distinguishing TOH from AVN, with a potential to aid treatment decisions and lead to the avoidance of unnecessary surgery.

Bone Marrow Edema: Overview of Etiology and Treatment Strategies

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Bone marrow edema (BME) is a nonspecific but relevant finding, usually indicating the presence of an underlying pathology.

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The gold standard technique for detecting BME is magnetic resonance imaging (MRI), as it allows for a correct diagnosis to be made, which is extremely important given the heterogeneity of BME-related diseases.

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Depending on the severity of painful symptomatology and the MRI evidence, different treatment strategies can be followed: physical modalities, pharmacological options, and surgical therapy.

Radiomics and Machine Learning Can Differentiate Transient Osteoporosis from Avascular Necrosis of the Hip

Differentiation between transient osteoporosis (TOH) and avascular necrosis (AVN) of the hip is a longstanding challenge in musculoskeletal radiology. The purpose of this study was to utilize MRI-based radiomics and machine learning (ML) for accurate differentiation between the two entities. A total of 109 hips with TOH and 104 hips with AVN were retrospectively included. Femoral heads and necks with segmented radiomics features were extracted. Three ML classifiers (XGboost, CatBoost and SVM) using 38 relevant radiomics features were trained on 70% and validated on 30% of the dataset. ML performance was compared to two musculoskeletal radiologists, a general radiologist and two radiology residents. XGboost achieved the best performance with an area under the curve (AUC) of 93.7% (95% CI from 87.7 to 99.8%) among ML models. MSK radiologists achieved an AUC of 90.6% (95% CI from 86.7% to 94.5%) and 88.3% (95% CI from 84% to 92.7%), respectively, similar to residents. The general radiologist achieved an AUC of 84.5% (95% CI from 80% to 89%), significantly lower than of XGboost (p = 0.017). In conclusion, radiomics-based ML achieved a performance similar to MSK radiologists and significantly higher compared to general radiologists in differentiating between TOH and AVN.

High-energy focused extracorporeal shock wave therapy for bone marrow edema syndrome of the hip: A retrospective study

The objective of this retrospective study was to evaluate the efficacy of high-energy focused extracorporeal shock wave therapy (HF-ESWT) on painful bone marrow edema syndrome (BMES) of the hip and shorten the natural course of disease.Thirty-four consecutive patients with BMES of the hip were treated with HF-ESWT in our department between August 2017and July 2018. The progression and treatment results of BMES were evaluated by imaging examination and clinical outcomes. The clinical outcomes include hip pain and function which were measured using the visual analog scale (VAS) and Harris hip score (HHS), respectively, and the VAS and HHS of all patients were calculated and evaluated before treatment (s0), at 1 month (s1), 3 months (s2), 6 months (s3)post-treatment. Imaging examination including Pelvic radiographs and frog views and double hip magnetic resonance imaging (MRI) were also obtained and scheduled before treatment, at 1, 3, 6, and the final follow-up post-treatment to exclude avascular necrosis and other pathology.All patients successfully completed the treatment and follow-up. Compared with pretherapy, the pain was alleviated to varying degrees and the HHS was significantly improved, and the VAS was significantly reduced at S1-2 (1- and 3-months post-treatment) after therapeutic intervention (P < .05). The mean improvements were strongly statistically significant between S0 and S1 and between S1 andS2 (P < .0001) and less significant between S2 and S3 (P < .01). The mean improvement between 6 months (S3) and final follow-up (more than 12 months) was not statistically significant. The MRI findings demonstrated that the diffuse BMES in the femoral head and neck disappeared completely.HF-ESWT is a safe, effective, reliable, and noninvasive treatment in patients with painful BMES of the hip, and it can accelerate the recovery of BMES of the hip, shorten the treatment time and course of disease, improve hip joint function and the quality of life of patients.

[Imaging and classification of avascular femoral head necrosis]

Avascular femoral head necrosis (AVNFH) is difficult to diagnose on plain radiographs in early stages of the disease. Since early stages are often clinically occult, early use of MRI is required to rule out or verify a clinical suspicion. MRI and, in some cases, additional CT are the cornerstones of AVNFH diagnosis and classification. Anteroposterior radiography of the pelvis and a second plane of the involved hip remains the primary basic imaging examination for follow-up and to rule out other pathologies. Correct staging of adult disease has been shown to be the key factor in therapeutic decision-making. According to the German S3 guideline on diagnosis and treatment of AVNFH, use of the ARCO classification is recommended for staging. This paper presents the current status of diagnosis and classification of adult AVNFH. The criteria for ascribing disease to a particular ARCO stage are defined and critically discussed.

Nomenclature of Subchondral Nonneoplastic Bone Lesions

OBJECTIVE. The purpose of this article is to summarize the nomenclature of nonneoplastic conditions affecting subchondral bone through a review of the medical literature and expert opinion of the Society of Skeletal Radiology Subchondral Bone Nomenclature Committee. CONCLUSION. This consensus statement summarizes current understanding of the pathophysiologic characteristics and imaging findings of subchondral nonneoplastic bone lesions and proposes nomenclature to improve effective communication across clinical specialties and help avoid diagnostic errors that could affect patient care.

Single Dose Therapy of Zoledronic Acid for the Treatment of Transient Osteoporosis of Hip

Objective

To shorten the natural course of transient osteoporosis of hip (TOH), which is a self-limiting idiopathic condition and requires 6–12 months for the resolution of symptoms, various therapies including treatment with bisphosphonates have been attempted. There exist fewer case reports evaluating the effect of bisphosphonates in TOH and most of them lack radiographic evidence of resolution of disease. The present study was carried out with an aim to evaluate the clinical and radiological outcomes of TOH patients subsequent to treatment with a single dose of zoledronic acid.

Methods

Data of 19 adult male and non-pregnant female patients with TOH treated with zoledronic acid were included in the study. Efficacy was assessed using changes in clinical signs and symptoms, visual analogue scale pain score, and changes in bone marrow edema (BME) in magnetic resonance imaging (MRI).

Results

Mean age of the patients was 42.1 years, 17 being males. The mean time of onset of symptom was 4 weeks. Subsequent to treatment, the patients were pain-free and had no limp within an average of 2.8 weeks (range, 2–5 weeks) and remained asymptomatic at a mean follow-up of 35 months (range, 6–54 months). The post-treatment MRI showed resolution of BME in approximately 84% (16/19) of patients at 3 months. No major adverse events were reported. None of the patients progressed to avascular necrosis at their last follow-up.

Conclusion

Intravenous single dose administration of zoledronic acid provides early pain relief and complete reversal of TOH. Consequently, zoledronic acid is proposed as a new paradigm in the management of TOH.

TRANSIENT OSTEOPOROSIS: CLINICAL SPECTRUM IN ADULTS AND ASSOCIATED RISK FACTORS

Objective: We aimed to describe the natural history of the rare clinical syndrome of transient osteoporosis (TO) and ascertain potential risk factors. Methods: Retrospective cohort study of adults with TO at Mayo Clinic, Rochester, Minnesota, over 15 years. Adults with acute-onset joint pain worsened by weight bearing and bone marrow edema on magnetic resonance imaging were included; exclusion criteria were trauma, tumors, rheumatic diseases, avascular necrosis, infection, and hyperesthesia. Results: Thirty-three patients with TO were identified: 20 males, median age at diagnosis 47 years, and median body mass index 28 kg/m². Median time to diagnosis was 2 months, and time to symptom resolution was 4 months. All cases involved the lower extremity, with the majority affecting the hip. Most patients (79%) had at least one possible identified risk factor. The most frequent risk factor was low bone mineral density (BMD) in 13 patients (39% of cohort). Of the 16 patients with BMD measure, 8 had low BMD at a site other than TO. The next most frequent risk factors were sudden limb overuse and more than one episode of TO, observed in 30%, followed by a disorder of bone and mineral metabolism in 27%. Conclusion: TO affects middle-age men more than women, primarily involves weight-bearing joints, and usually resolves with conservative management. Its etiology remains unclear; however, the common presence of risk factors, abnormalities in bone and mineral laboratories, and decrease in BMD suggest that systemic factors may be important in its development. Abbreviations: AVN = avascular necrosis; BMD = bone mineral density; DXA = dual-energy X-ray absorptiometry; MRI = magnetic resonance imaging; TO = transient osteoporosis.

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.

Radiological morphology variances of transient osteoporosis of the hip

BACKGROUND

Although several morphological abnormalities or variances of the hip joint have been proposed to be associated with hip joint degeneration, few studies have investigated any radiological features in patients with transient osteoporosis of the hip (TOH). The purpose of this study is to evaluate the morphological variances of the hip joint in TOH patients radiographically.

METHODS

The TOH group consisted of 31 hips in 31 patients. Age- and gender-matched asymptomatic hips in patients with unilateral osteonecrosis of the femoral head were served as controls. Radiographs and MRI were utilized to examine the following parameters: acetabular dysplasia, acetabular overcoverage, acetabular retroversion, and asphericity of the femoral head-neck junction. Also, localization of the main bone marrow edema (BME) lesion was investigated.

RESULTS

TOH patients had a significantly higher incidence of acetabular retroversion (52% with a positive cross-over sign and 29% with posterior wall deficiency) than the controls (13%, P = 0.0023; 6%, P = 0.043, respectively), which was also confirmed by smaller acetabular anteversion angles on axial MRI. In addition, TOH patients tended to show asphericity of the anterior femoral head-neck junction compared to controls (39% vs. 13%, P = 0.040). In 90% of the TOH patients, the main BME lesion was located in the subchondral area of the superior portion of the femoral head, and 77% of the lesion were recognized as a band-like pattern in MRI.

CONCLUSIONS

Acetabular retroversion and asphericity of the femoral head-neck junction were more commonly observed in TOH patients compared to controls. The main BME lesion was most frequently located in the superior portion of the femoral head.

Transient osteoporosis of the hip: review of the literature

Transient osteoporosis of the hip (TOH) is a temporary clinical condition of unknown etiology which usually resolves with conservative therapy though may be complicated by fracture or progression to avascular necrosis (AVN). TOH may be slightly more prevalent in men but when it occurs in women, it is most often seen in the latter part of pregnancy. Though fracture is a rare complication of TOH when it occurs, it is most often associated with TOH occurring in pregnancy. Magnetic resonance imaging (MRI) is the best method to diagnosis TOH. Low signal intensity on T1-weighted images, high signal intensity on T2-weighted images, and homogenous pattern of edema (the femoral head and/or neck) with normal subchondral area are in favor of TOH. A shortened course to recovery is reported by use of bisphosphonates, calcitonin, or teriparatide. Based on reported cases, core decompression is not superior to medical therapy. Transient osteoporosis of the hip, which often has no known etiology, usually resolves with conservative therapy but may predispose the patient to fracture or avascular necrosis. Diagnostic method of choice is magnetic resonance imaging. Bisphosphonates, calcitonin, or teriparatide are reported as a useful approach to reduce duration of recovery.

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.

Clinical and basic research on steroid-induced osteonecrosis of the femoral head in Japan

BACKGROUND

Steroid (glucocorticoid)-induced osteonecrosis of the femoral head (ONFH) in young adults has been a challenging disorder due to frequent incidence of collapse of the femoral head and resulting dysfunction of the hip joint and impairing quality of life. In Japan, the working group on ONFH in the Specific Disease Investigation Committee under auspices of the Japanese Ministry of Health, Labor and Welfare was founded in 1975, clinical and related basic research on ONFH have been continued for more than 40 years.

EPIDEMIOLOGY AND CLINICAL COURSE

A national epidemiologic survey in 2004 estimated that 2200 new patients per year would be diagnosed with ONFH in Japan. ONFH was associated with steroid intake (51%), heavy alcohol intake (31%), both (3%), and neither (15%). The male-to-female ratio was 5:4, and the peak decades of age at definitive diagnosis were the 40s in male patients and the 30s in females. MRI studies revealed that ONFH would have occurred in early phase after start of steroid administration and no expansion of necrotic lesion within the femoral head in spite of continued steroid use. To standardize ONFH diagnosis and treatment strategy, the Committee established validated diagnostic criteria, a radiological staging system, and type categorization.

TREATMENT OPTIONS

Most symptomatic patients with collapse of the femoral head require various surgical procedures. Joint preserving surgery, such as transtrochanteric rotational osteotomy and curved varus osteotomy, should be the treatment choice for young patients with healthy areas without severe collapse of the femoral head.

CLINICAL AND RELATED BASIC RESEARCH

Clinical and basic research has been performed to determine the pathogenesis of steroid-induced ONFH. Low hepatic CYP3A activity has been reported to significantly contribute to the risk of steroid-induced ONFH. Several gene polymorphisms related to steroid metabolism were shown to be associated with the occurrence of ONFH.

S3-Guideline non-traumatic adult femoral head necrosis

INTRODUCTION

The treatment of adult non-traumatic avascular necrosis of the femoral head (AVN; N-ANFH) within an estimated incidence of 5000-7000 cases per annum in Germany remains a challenge. Risk factors include steroids, alcohol abuse, chemotherapy and immunosuppressive medication, but a genetic predisposition has been suggested. Early diagnosis of this often bilateral disease process is essential for successful conservative or joint preserving surgical management. In this review, we present the update German consensus S3 guideline "diagnosis and management for N-ANFH" as a concise summary.

MATERIALS AND METHODS

This systematic review is based on the published literature from January 1, 1970 to April 31, 2013 (German and English language). Inclusion criteria were systematic reviews, meta-analyses and relevant peer review publications. We identified a total of 3715 related publications, of which 422 were suitable according to the SIGN criteria, but only 159 fulfilled our inclusion criteria.

RESULTS AND CONCLUSIONS

Clinical suspicion of N-ANFH mandates radiographic evaluation. If radiographs are normal MRI scans are recommended, which should be evaluated according to the ARCO-classification. Differential diagnoses include transient osteoporosis, bone bruise, insufficiency fracture and destructive arthropathy. Untreated, subchondral fractures commonly occur within 2 years, during which the risk for contralateral involvement is high-thereafter unlikely. Conservative management with Ilomedin and Alendronat can be tried, but other pharmacological or physical treatments are inappropriate. No specific joint preserving procedure can be recommended, but core decompression should be considered in early stages if necrosis is <30 %. In ARCO stages IIIc or IV total hip arthroplasty (THA) should be contemplated, which offers similar outcome compared to osteoarthritis. Young age is the main risk factor for higher revision rates after THA for N-ANFH.

Transient osteoporosis of the hip in a non-pregnant woman

Transient osteoporosis of the hip is a rare, self-limiting condition, occurring most commonly in middle-aged men, but also sometimes in women, usually in late pregnancy. It is characterised by gradual onset of hip pain aggravated by weight bearing without any associated history of trauma and systemic illness. It is usually of unknown aetiology, but pregnancy is a recognised risk factor for women. Other conditions that can mimic transient osteoporosis of the hip on MRI are osteonecrosis, osteomyelitis and neoplasms. We present a case of a 38-year-old non-pregnant woman with transient osteoporosis of the hip, managed conservatively, leading to a full recovery. Treatment is conservative, including protected weight bearing, physical therapy and non-steroidal analgesics. The patient was completely painless and symptom free at 2-year follow-up.

Intractable bone marrow edema syndrome of the hip

There is a need for an effective and noninvasive treatment for intractable bone marrow edema syndrome of the hip. Forty-six patients with intractable bone marrow edema syndrome of the hip were retrospectively studied to compare the short-term clinical effects of treatment with high-energy extracorporeal shock wave therapy vs femoral head core decompression. The postoperative visual analog scale score decreased significantly more in the extracorporeal shock wave therapy group compared with the femoral head core decompression group (P<.05). For unilateral lesions, postoperative Harris Hip Scores for all hips in the extracorporeal shock wave therapy group were more significantly improved than Harris Hip Scores for all hips in the femoral head core decompression group (P<.05). Patients who underwent extracorporeal shock wave therapy also resumed daily activities significantly earlier. Average overall operative time was similar in both groups. Symptoms disappeared significantly sooner in the extracorporeal shock wave therapy group in patients with both unilateral (P<.01) and bilateral lesions (P<.05). Hospital costs were significantly lower with extracorporeal shock wave therapy compared with femoral head core decompression. The intraoperative fluoroscopy radiation dose was lower in extracorporeal shock wave therapy than in femoral head core decompression for both unilateral (P<.05) and bilateral lesions (P<.01). On magnetic resonance imaging (MRI), bone marrow edema improved in all patients during the follow-up period. After extracorporeal shock wave therapy, all patients remained pain-free and had normal findings on posttreatment radiographs and MRI scans. Extracorporeal shock wave therapy appears to be a valid, reliable, and noninvasive tool for rapidly resolving intractable bone marrow edema syndrome of the hip, and it has a low complication rate and relatively low cost compared with other conservative and surgical treatment approaches.

MR imaging of transient osteoporosis of the hip: an update on 155 hip joints

PURPOSE

Transient osteoporosis of the hip (TOH) presents with acute onset pain and bone marrow edema (BMe) on MR imaging. The purpose of this study is to revise the MR imaging characteristics of TOH by analyzing the data derived from 155 hip examinations. We also sought to explore the relationship between the duration of symptoms and the presence of sparing and subchondral fractures.

MATERIALS AND METHODS

MR images of 155 hips (141 TOH patients) were retrospectively evaluated for the presence of insufficiency fractures and the morphology of BMe. Sparing of the medial bone marrow of the femoral head was recorded together with demographic and clinical data. Progression to regional migratory osteoporosis (RMO) and postpartum cases were also recorded.

RESULTS

Our population consisted of 76.4% male and 23.6% female patients. RMO progression was recorded in 19.4% and 4 postpartum cases displayed bilateral disease. Sparing of the medial bone marrow was present at 87.7% of patients and disappeared as the disease progressed (P=0.005). BMe was restricted within the femoral head in 11.0%, extended to the femoral neck in 40% and to the femoral shaft in 49% of the cases studied. Subchondral fractures were present at 48.7% of the hips.

CONCLUSION

This study describes TOH patient characteristics, the MR imaging findings (BMe pattern, microfractures), their association with symptom duration and the chance of progressing to RMO.

Bone marrow lesions: A systematic diagnostic approach

Bone marrow lesions on magnetic resonance (MR) imaging are common and may be seen with various pathologies. The authors outline a systematic diagnostic approach with proposed categorization of various etiologies of bone marrow lesions. Utilization of typical imaging features on conventional MR imaging techniques and other problem-solving techniques, such as chemical shift imaging and diffusion-weighted imaging (DWI), to achieve accurate final diagnosis has been highlighted.

Idiopathic transient osteoporosis of the talus: a cause for unexplained foot and ankle pain

A 53-year-old woman was investigated for several neoplastic, inflammatory, and infective conditions for her left foot, and ankle pain associated with swelling, which she developed unexpectedly without history of trauma or infection. Gross osteopenia in the talus raised the possibilities of several differential diagnoses, but a magnetic resonance imaging scan showed diffuse bone marrow edema in the talus. With negative infective and inflammatory markers, the condition was ultimately labeled as "transient osteoporosis." She was reassured and followed up regularly. At the end of 12 months, she was completely asymptomatic, and her radiograph and magnetic resonance images showed significant improvement, with a normal-appearing talus and ankle joint, and there was complete resolution of bone marrow edema. Although "transient osteoporosis" of the foot is an uncommon condition, clinicians should be aware of this. Unexplained foot pain, with osteopenic bone and diffuse bone marrow edema on magnetic resonance imaging scan, is a feature of this condition. However, the diagnosis is established once other causes are excluded. The condition is self-limiting, and watchful expectancy of a normal recovery is the mainstay of treatment.

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.

An unusual cause of hip pain

The authors describe a case of bilateral transient regional osteoporosis of the hips occurring in a primigravida patient, which resolved spontaneously postpartum, leaving no residual damage. The authors review the existing literature regarding this disease.

[Transient bone marrow edema of the hip]

Transient bone marrow edema of the hip is characterized by moderate homogeneous low MR signal intensity with ill-defined margins that involves at least a portion of the femoral head. Spin echo T1-weighted images are helpful to exclude other underlying diseases (tumor, infection, necrosis from systemic origin…), for which marrow edema is secondary or no epiphyseal in location. High-resolution fat-suppressed T2-weighted or proton density images allow evaluation of the articular cartilage, subchondral bone and subchondal marrow: if the articular cartilage is abnormal, the lesion is irreversible (arthrosis or necrosis); if the subchondral bone is focally interrupted and/or if the femoral is no longer spherical, the lesion is irreversible (necrosis); if a focal linear fluid collection is present under the subchondral bone, the lesion is irreversible (necrosis). Finally, subchondral changes may provide useful prognostic information: the absence of any abnormality other than marrow edema typically indicates that complete resolution is likely; the presence of a focal T2-weighted hypointense lesion immediately next to the subchondral bone suggests an irreversible lesion, especially if it is equal to or thicker than 4mm or the joint space. In some instances, prognosis cannot be reliably determined requiring the need for follow-up imaging.

A newly developed snack effective for enhancing bone volume

BACKGROUND

The incidence of primary osteoporosis is higher in Japan than in USA and European countries. Recently, the importance of preventive medicine has been gradually recognized in the field of orthopaedic surgery with a concept that peak bone mass should be increased in childhood as much as possible for the prevention of osteoporosis. Under such background, we have developed a new bean snack with an aim to improve bone volume loss. In this study, we examined the effects of a newly developed snack on bone volume and density in osteoporosis model mice.

METHODS

Orchiectomy (ORX) and ovariectomy (OVX) were performed for C57BL/6J mice of twelve-week-old (Jackson Laboratory, Bar Harbar, ME, USA) were used in this experiment. We prepared and given three types of powder diet e.g.: normal calcium diet (NCD, Ca: 0.9%, Clea Japan Co., Tokyo, Japan), low calcium diet (LCD, Ca: 0.63%, Clea Japan Co.,) and special diet (SCD, Ca: 0.9%). Eighteen weeks after surgery, all the animals were sacrified and prepared for histomorphometric analysis to quantify bone density and bone mineral content.

RESULTS

As a result of histomorphometric examination, SCD was revealed to enhance bone volume irrespective of age and sex. The bone density was increased significantly in osteoporosis model mice fed the newly developmental snack as compared with the control mice. The bone mineral content was also enhanced significantly. These phenomena were revealed in both sexes.

CONCLUSION

It is shown that the newly developed bean snack is highly effective for the improvement of bone volume loss irrespective of sex. We demonstrated that newly developmental snack supplements may be a useful preventive measure for Japanese whose bone mineral density values are less than the ideal condition.

Collapsed subchondral fatigue fracture of the femoral head

Several etiologies can lead to a subchondral fracture of the femoral head, which may result in femoral head collapse and degenerative change. This article evaluates the follow-up results of subchondral fatigue fractures of the femoral head in which femoral head collapse occurred. The study shows that collapsed subchondral fatigue fractures of the femoral head have a benign clinical course quite unlike that of collapsed osteonecrosis of the femoral head.

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.

Regional migratory osteoporosis

Regional migratory osteoporosis (RMO) is an uncommon disease characterised by a migrating arthralgia involving the weight bearing joints of the lower limb. The typical imaging findings on radiographs, magnetic resonance imaging, computed tomography and bone scintigraphy are described and illustrated. Men in their fifth and sixth decades of life are most commonly affected. The most common presentation is with proximal to distal spread in the lower limb. The world literature has been reviewed which has revealed 63 documented cases of regional osteoporosis or bone marrow oedema with migratory symptoms. Most of these cases have not been labelled as RMO and therefore the condition is probably under-diagnosed. The radiology of RMO is indistinguishable from transient osteoporosis of the hip (TOH) except for the migratory symptoms and the two conditions are likely to be part of the same spectrum of disease. Systemic osteoporosis is a more recently recognised accompanying feature that hints at an underlying aetiology and an approach to the management of this condition.

Histopathological perspective on bone marrow oedema, reactive bone change and haemorrhage

This article presents a systematic review of the current biomedical literature surrounding the aetiopathogenesis and histopathological features of bone marrow oedema, reactive bone change and haemorrhage. Bone marrow oedema is generally demonstrated as a non-specific finding on magnetic resonance imaging in association with infections, tumours and avascular necrosis. When it occurs in isolation as a primary event not triggered by any obvious bony pathology in the clinical setting of debilitating joint pain, it constitutes the "bone marrow oedema syndrome". Although the latter diagnosis is based on magnetic resonance (MR) imaging, showing the lesion as areas of signal hyperintensity within the marrow, recent radiology-histology correlational studies have shown variably interstitial marrow oedema, necrosis, fibrosis and trabecular bone abnormalities. In light of these facts, the use of the term bone marrow oedema syndrome in a radiological context might be considered questionable, but histopathological techniques are not sensitive in detecting increased extracellular fluid. Reactive bone changes may be focal or diffuse and usually amount to increased bone formation. Bone marrow haemorrhage, due to trauma, results in bone bruising, a condition in which the size of the bruise and associated osteochondral injury determines the outcome, although the natural history of these lesions is still being researched.

[Transient osteoporosis of the hip in pregnancy. Successful treatment with calcitonin: a case report]

Transient osteoporosis of the hip is a rare clinical disorder of unknown etiology, characterized by hip pain and functional disability that resolves spontaneously in 6-24 months. Despite a benign prognosis, the long clinical course causes prolonged disability. We report on a case of transient osteoporosis of the hip during pregnancy that was rapidly resolved with the use of calcitonin. An accurate diagnosis was made 2 months after the onset of symptoms (4 weeks postpartum) based on findings in the form of bone marrow edema of the right hip by magnetic resonance imaging. The patient received calcitonin for 8 weeks and the beneficial effect was observed after 3 weeks of therapy with full resolution of symptoms after 8 weeks of therapy (4 months after onset of symptoms). We suggest that the use of calcitonin may be considered as a therapeutic intervention to shorten the disease duration.

Subchondral fracture of the femoral head in healthy adults

Subchondral fracture of the femoral head has been reported to occur as an insufficiency fracture associated with poor bone quality or as a fatigue fracture in young military recruits. Transient osteoporosis of the hip has clinical and imaging findings that resemble those of a subchondral fracture, but it usually occurs in healthy middle-aged people not involved in sports or similar activities. The clinical aspects of five cases of subchondral fracture of the femoral head occurring in four healthy adults without antecedent trauma were evaluated. Of particular interest were whether subchondral fracture of the femoral head could occur without a sudden increase in daily activity and what differences could be detected from the imaging and clinical courses between subchondral fracture of the femoral head and transient osteoporosis of the hip. Three cases of subchondral fracture of the femoral head occurred without an increase in daily activity. The only difference in imaging findings between subchondral fracture of the femoral head and transient osteoporosis of the hip was the existence of a subchondral fracture line seen on magnetic resonance images of a subchondral fracture of the femoral head. The clinical courses of these disorders were similar. These findings suggest transient osteoporosis of the hip and subchondral fracture of the femoral head are subchondral bone injuries of different severity.

LEVEL OF EVIDENCE

Level IV, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

A subchondral fracture in transient osteoporosis of the hip

Although subchondral changes are reported to be associated with transient osteoporosis of the hip (TOH), the etiology of this disorder is unknown.In this paper, we describe a 45-year-old man with TOH who underwent both MRI and CT examinations. Plain radiographs obtained 2 months after the onset of hip pain showed a focal loss of radiodensity in the left femoral head. MRI revealed a bone marrow edema pattern in the left femoral head and neck with an associated subchondral serpiginous low signal intensity line on the T1-weighted images. A CT scan showed a subchondral fracture in the corresponding area. The hip pain and imaging abnormalities resolved spontaneously following conservative treatment. This case study demonstrated that a subchondral fracture of the femoral head was associated with TOH using MRI and CT examinations, and suggests that the presence of a subchondral fracture may be important for the pathophysiology of TOH.

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

Acute bone marrow edema of the hip is a diagnostic challenge for both radiologists and clinicians. Marrow edema is often seen in patients with hip pain and restriction of motion. In patients with acute non-traumatic hip pain, whose radiographs are negative or inconclusive, MR imaging is the imaging study of choice. MR imaging is the most sensitive and specific imaging technique for detecting transient osteoporosis and osteonecrosis, as well as for detecting and staging fractures and microfractures. MR imaging is able to show marrow involvement in various inflammatory disorders and to diagnose reactive marrow edema from femoroacetabular impingment and greater trochanteric pain syndrome. In patients with septic arthritis, it may also depict associated marrow edema and suggest its reactive or infectious origin. For the neoplastic disorders, although plain radiographs should be the initial examination, MR imaging may follow for assessing extension to the surrounding soft tissues and/or associated pathologic fracture, facilitating thus the treatment planning. Computed tomography is more accurate compared with MR imaging in diagnosing intra-articular osteoid osteomas.

MR Imaging of the Hip: Osseous Lesions

Because of the exquisite soft tissue contrast resolution of MR imaging combined with recent technologic developments, a variety of conditions involving the hip joint and adjacent bony structures can be well evaluated using MR imaging, with or without contrast material. Among the different conditions, hip trauma and avascular necrosis are the most frequent indications. Other entities for which MR imaging has proven its usefulness include subchondral fractures, osteochondritis dissecans, transient osteoporosis, bone tumors, inflammatory and infectious processes, and a variety of bone marrow disorders.

Pathologic conditions mimicking osteonecrosis

MRI has become increasingly helpful in establishing an early diagnosis of avascular necrosis(AVN). AVN often demonstrates a classic pattern on MRI; findings earlier in the course of the disease are less specific. Many pitfalls can complicate interpretation, and a number of pathologic conditions can share features of early AVN on MRI and plain radiographs. These entities should be distinguished from AVN, because treatment and prognosis may differ significantly.

MR imaging findings in transient osteoporosis of the hip

PURPOSE

The authors sought to describe the magnetic resonance (MR) imaging findings including perfusion imaging, in association with the course of acute bone marrow oedema syndrome (aBMEs), in a group of patients with acute hip pain and a final diagnosis of transient osteoporosis of the hip (TOH).

MATERIALS AND METHODS

From 217 patients referred with a probable diagnosis of avascular necrosis (AVN) of the femoral head, we identified 42 patients who had clinical and radiographic findings not relevant to AVN. MR imaging examinations were performed on a 1.0T scanner. Perfusion imaging was performed in 20 patients. The bone marrow oedema (BME) was classified in four stages. In addition, the presence or absence of oedema in the subchondral area and the presence of other subchondral lesions were recorded. Acetabular bone marrow was also assessed for the presence of oedema. The quantitative measurements included: maximum size of the effusion, percentage of enhancement (PE) and time of peak enhancement of abnormal marrow compared to the first pass, on the perfusion images.

RESULTS

Osteopenia was present on plain radiographs in 87% of cases. The most common pattern of BME was extending to the femoral head and neck. Acetabulum was involved in 16.6%. In 22.6% the BME spared the subchondral region of the femoral head. There were two cases (4.7%) with subchondral changes. A joint effusion was noted in 33 of the 42 patients. On perfusion imaging, a delayed peak enhancement was noted in 20 patients between 40 and 65 s after the first pass of contrast. No patient had any evidence of femoral head collapse or change in sphericity on follow-up MRI. None of the patients developed avascular necrosis in a time frame of 18 months from the onset of the acute hip pain.

CONCLUSION

The aBMEs MR imaging pattern varies and is most commonly appearing on X-rays as osteopenia. Absence of subcondral lesions, delayed peak enhancement of the abnormal marrow on perfusion images, and sparing of subchondral zone from marrow oedema are MR imaging findings highly correlated to TOH.

Risk factors for nontraumatic osteonecrosis of the femoral head after renal transplantation

We investigated risk factors for osteonecrosis of the femoral head (ONF) in renal transplant recipients, who are susceptible to the disease. Among 287 renal transplant recipients, 18 ONF patients with enough data were included, and 18 age- and sex-matched recipients without ONF were nominated as reference cases. Risk factors were analyzed using a conditional logistic regression method. There were no differences between the ONF patients and the reference cases regarding the types of immunosuppressant or the donor (living or cadaveric, father or mother, matching blood type and human leukocyte antigens). The daily oral steroid dosage (prednisolone 25.0 mg/day or more) and blood urea nitrogen level 2 months after transplantation were the only factors with relevance to the occurrence of ONF. We propose that oral steroid dosages should be low or reduced after renal transplantation, and acute rejection should be controlled with pulsed therapy.

Avascular necrosis and bone marrow edema syndrome

MR imaging is the most accurate modality for the diagnosis of AVN, bone marrow edema syndrome, and femoral head insufficiency fractures. When the particular demographics of the patient are considered, the specificity of this examination is high. The reported success rates of joint-sparing operative intervention are variable. When compared with conservative management, the outcome of joint-sparing operative intervention in patients who have early (stage I, II) AVN lesions is improved. This is impetus for screening programs for patients who are known to be at high risk for AVN, such as patients who have undergone renal transplants and others who are on long-term, high-dose corticosteroid treatment. There is strong evidence that bone marrow edema syndrome (TO) is a distinct entity with demonstrable unique histopathology and well-defined demographics. Increased spatial resolution revealed typical subchondral findings of AVN in lesions that were once believed to represent irreversible TO. SIF of the femoral head is a new concept with a seemingly distinct population and with clinical presentation and imaging characteristics that should permit its differentiation from AVN.

Biochemical markers of bone metabolism in bone marrow edema syndrome of the hip

The aim of this study was to evaluate bone metabolism in patients with bone marrow edema syndrome of the hip. In 37 consecutive patients undergoing core decompression of the femoral head, biochemical markers of bone metabolism were measured in aspirates from cancellous bone and in samples obtained simultaneously from peripheral blood. The diagnosis was made by means of radiographs, magnetic resonance imaging (MRI), and core biopsy specimens. Undecalcified microtome section were available for histopathological evaluation. Bone specific alkaline phosphatase (bone ALP), osteocalcin (OC), procollagen Type I N-terminal propeptide (PINP), and C-terminal cross-linking telopeptide (ICTP) were studied. Mean serum levels of analytes were 13.1 ng/mL (OC), 11.2 ng/mL (bone ALP), 4.7 ng/mL (ICTP), and 38.8 ng/mL (PINP). In samples obtained from cancellous bone, mean concentrations of all markers were elevated significantly. The mean bone to serum ratios for bone ALP and OC were 14.1 (P=0.005) and 4.1 (P=0.002), respectively. For collagen Type I metabolites, bone to serum ratios averaged 16.3 (P=0.001) for ICTP and 9.6 (P=0.001) for PINP. Markers of bone formation correlated with each other in serum as well as in aspirates from cancellous bone. Elevation of all markers in aspirates from cancellous bone pointed at increased bone turnover, which correlated with histopathological findings of irregularly woven bone, osteoid seams, and lining cells. Mean serum concentrations of all markers, however, were not different from healthy individuals and thus did not provide any useful clue in the diagnosis of this disease. The lack of osteonecrotic regions in our specimens, the marked increase of bone turnover in samples obtained from edematous lesions, and the fact that none of the patients developed osteonecrosis of the femoral head so far seem to further support the contention that transient bone marrow edema syndrome of the hip is a distinct clinical entity.

Increased perfusion of the femoral head in transient bone marrow edema syndrome

The pathophysiology of transient bone marrow edema syndrome is not known. Ischemia has been suggested as the pathophysiologic factor, because the histologic findings are similar to those of early stage osteonecrosis. Angiographic studies of osteonecrotic femoral heads have shown arterial interruption and impaired perfusion. The current report describes the angiographic and scintigraphic findings of transient bone marrow edema syndrome of the hip in a 45-year-old man. The nutrient arteries were dilated, and the femoral head perfusion was increased compared with the unaffected contralateral side. These findings suggest that a vasomotor response plays a role in the pathogenesis of transient bone marrow edema syndrome. The disease might be a reversible process after temporary ischemia of the femoral head.

Intravenous pamidronate in the treatment of transient osteoporosis of the hip

The aim of this study was to evaluate the efficacy of intravenous pamidronate in patients with transient osteoporosis of the hip (TOH). Thirteen men and three women (mean age 38.3 years, range 30-49) were recruited. The diagnosis was made by means of radiographs, bone scintigraphy, and magnetic resonance imaging (MRI). Pamidronate (45 mg) was intravenously administered three times, once every third day. The outcome measures included a clinical assessment using a pain visual analog scale (VAS; range 0-100), and the WOMAC functional impairment score (FUI; range 0-100). The bone mineral density (BMD) of the total hip and femoral neck was measured using dual-energy X-ray absorptiometry (DXA). Clinical assessments were made before treatment (T(0)) and 1 month later (T(1)), and the densitometric measurements at T(0), and then after 2 (T(2)) and 4 months (T(4)). A further MRI scan was made 3 months after treatment. In comparison to the unaffected side, there was a significant decrease at T(0) in the BMD of both the total hip (median 16.6%, range 8.5%-29.1%, p < 0.00001) and femoral neck (median 22.5%, range 12.0%-34.2%, p < 0.00001). By T(1), both VAS and FUI had decreased significantly (p < 0.00001). By T(2), the total hip and femoral neck BMD had increased by 10.9% (range 2.7%-23.6%, p < 0.00001) and 12.3% (range 7.8%-26.9%, p < 0.00001), respectively, and all patients were asymptomatic. By T(3), the MRI findings had normalized in all patients and, at T(4), there was a further increase in BMD. None of the patients experienced symptom relapse during the follow-up of 39.5 +/- 17.7 months. These results suggest that a short course of pamidronate is effective in treating TOH, and leads to a prompt and long-lasting recovery.