Subchondral changes in transient osteoporosis of the hip

Objective. To review the subchondral changes on MR imaging in transient osteoporosis of the hip (TOH) and to consider the pathophysiology. Design and patients. MR images of 12 hips of 11 consecutive patients with TOH were retrospectively studied. The diagnoses of TOH were confirmed on the basis of previously published criteria, including decreased bone density of the femoral head and/or neck on radiographs, bone marrow edema (BME) pattern on MR images, spontaneous resolution of the symptoms and a return to normal radiodensity. Results. All 12 hips showed a BME pattern in the femoral head and/or neck. Linear patterns of very low signal intensity were identified on T1-weighted images in the subchondral area within the diffuse low signal intensity area in all 12 hips. On T2-weighted images, a low signal intensity line was observed in the corresponding area in eight hips only. These linear patterns were thought to represent subchondral fracture lines. Conclusions. The presence of a subchondral fracture may be important when considering the pathophysiology of TOH. Received: 5 April 2000 Revision requested: 11 July 2000 Revision received: 22 January 2001 Accepted: 29 January 2001     

暂时性骨质疏松症的MRI表现

目的:探讨暂时性骨质疏松症的MRI表现。方法:对经临床证实的10例暂时性骨质疏松症(TOH)患者的临床及影像学资料进行回顾性分析。10例患者均行MRI平扫,其中5例行MRI增强扫描,4例行CT扫描。10例中男7例,女3例,年龄为25～40岁。结果:10例TOH中,双侧髋关节同时受累2例,单侧受累8例,主要MRI表现为弥漫性骨髓水肿,累及股骨头、颈及转子间,股骨头形态完整,1例可见软骨下应力性骨折,所有病例均无股骨头软骨下骨质缺损;关节囊肿胀和关节积液8髋;MRI增强扫描示病变区呈明显均匀强化。主要CT表现为股骨头骨密度弥漫性减低,骨皮质变薄。治疗5～11个月后患者疼痛症状消失,股骨内MRI信号恢复正常。结论:CT上表现为弥漫性骨质疏松、MRI表现为弥漫性骨髓水肿、缺乏软骨下骨质病变以及均匀一致强化是TOH性特征的影像学表现。     

Bone marrow edema of the hip: MR findings after core decompression.

Magnetic resonance imaging is an extremely sensitive technique for evaluation of bone marrow changes at an early stage of avascular necrosis (AVN) of the hip. We therefore examined 11 painful hips whose clinical symptoms led us to suspect idiopathic AVN. The radiographs of all of these either were normal or demonstrated a minimal decrease in radiodensity. Magnetic resonance demonstrated diffuse signal loss of the bone marrow at short TR/TE images of the femoral head in all hips, with various extensions in the head, neck, and intertrochanteric area. These regions turned iso- to hyperintense on long TR/TE images compatible with bone marrow edema (BME). Focal abnormalities characteristic for AVN were not seen in any of the cases. Radionuclide studies performed in six cases were positive. All patients underwent core decompression treatment. Hydrostatic bone marrow pressure measurement and intraosseous venography were positive in five cases when measured. Histology available in eight cases confirmed the presence of BME. Furthermore, the bone changes corresponded to those of early AVN. Follow-up examinations after core decompression with MR showed normal signal intensity in all cases. Magnetic resonance represents a viable diagnostic tool for BME and can monitor the therapeutic success of core decompression. Whether BME of the femoral head constitutes a distinct transient syndrome or represents an early form of AVN is controversial at present. Our findings support those who believe that BME may represent an initial stage of idiopathic AVN.     

Bone marrow oedema on MR imaging indicates ARCO stage 3 disease in patients with AVN of the femoral head

Objectives

To test the hypothesis that bone marrow oedema (BME) observed on MRI in patients with avascular necrosis (AVN) of the femoral head represents an indicator of subchondral fracture.

Methods

Thirty-seven symptomatic hips of 27 consecutive patients (53 % women, mean age 49.2) with AVN of the femoral head and associated BME on magnetic resonance (MR) imaging were included. MR findings were correlated with computed tomography (CT) of the hip and confirmed by histopathological examination of the resected femoral head. Imaging studies were analysed by two radiologists with use of the ARCO classification.

Results

On MR imaging a fracture line could be identified in 19/37 (51 %) cases, which were classified as ARCO stage 3 (n?=?15) and stage 4 (n?=?4). The remaining 18/37 (49 %) cases were classified as ARCO stage 2. However, in all 37/37 (100 %) cases a subchondral fracture was identified on CT, indicating ARCO stage 3/4 disease. The extent of subchondral fractures and the femoral head collapse was graded higher on CT as compared to MRI (P?Histopathological analysis confirmed bone necrosis and subchondral fractures.

Conclusions

In patients with AVN, BME of the femoral head represents a secondary sign of subchondral fracture and thus indicates ARCO stage 3 disease.

Key Points

? BME on MRI in AVN of femoral head indicates a subchondral fracture. ? BME in AVN of the femoral head represents ARCO stage 3/4 disease. ? CT identifies subchondral fractures and femoral head collapse better than MR imaging. ? This knowledge helps to avoid understaging and to trigger adequate treatment.     

髋部一过性骨质疏松的MRI表现及与股骨头缺血性坏死的鉴别

目的：探讨髋部一过性骨质疏松（TOH）的MRI表现及其与股骨头缺血性坏死（AVN）的鉴别。方法：回顾性分析7例有髋部疼痛症状的TOH患者MRI资料。男6例,女1例。年龄31~53岁,平均41岁。女性患者患病时不在妊娠期内。髋部行T1、T2WI、T2-STIR扫描。结果：病变均为单侧。病变部位T1WI均呈低信号,T2WI呈中高信号,压脂图像呈明显高信号。异常信号区可累及股骨头、股骨颈、股骨干上段,关节积液见于4个髋关节。结论：掌握TOH的MRI的特殊征象,有利于鉴别TOH与AVN。     

Magnetic resonance perfusion and diffusion imaging characteristics of transient bone marrow edema,avascular necrosis and subchondral insufficiency fractures of the proximal femur

Purpose

To evaluate magnetic resonance (MR) perfusion and diffusion imaging characteristics in patients with transient bone marrow edema (TBME), avascular necrosis (AVN), or subchondral insufficiency fractures (SIF) of the proximal femur.

Materials and methods

29 patients with painful hip and bone marrow edema pattern of the proximal femur on non-contrast MR imaging were examined using diffusion-weighted and dynamic gadolinium-enhanced sequences. Apparent diffusion coefficients (ADCs) and perfusion parameters were calculated for different regions of the proximal femur. Regional distribution and differences in ADC values and perfusion parameters were evaluated.

Results

Seven patients presented with TBME, 15 with AVN and seven with SIF of the proximal femur. Perfusion imaging showed significant differences for maximum enhancement values (E_max), slope (E_slope) and time to peak (TTP) between the three patient groups (p < 0.05). In contrast, no significant differences for ADC values were calculated when comparing TBME, AVN, and SIF patients.

Conclusion

Diffusion weighted imaging of bone marrow of the proximal femur did not show significant differences between patients with TBME, AVN or SIF. In contrast, MR perfusion imaging demonstrated significant differences for the different patient groups and may as a complementary imaging technique add information to the understanding of the pathophysiology of diseases associated with bone marrow edema.     

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.     

Segmental patterns of avascular necrosis of the femoral heads: early detection with MR imaging

Thirty-two patients (64 hips) in whom avascular necrosis (AVN) of the femoral heads was highly suspected clinically were studied by magnetic resonance (MR) imaging, radionuclide bone scintigraphy, and conventional radiography. MR studies were positive for AVN in 37 hips, compared with 30 positive scintigraphic studies. In all cases in which scintigraphy and radiography were positive, MR imaging demonstrated decreased signal from the affected femoral heads, indicative of bone marrow disease. Imaging results were confirmed by biopsy or subsequent imaging appearances. In patients with negative initial scintigraphic and radiographic studies, the MR imaging criterion for a positive study was a moderately decreased bone marrow signal displaying segmental patterns within an otherwise normal-appearing femoral head on relatively T1-weighted images. In this series of high-risk patients, radionuclide scintigraphy had a sensitivity of 81%, compared with 100% for MR imaging. MR imaging should be the imaging modality of choice for early evaluation of bone marrow changes indicative of AVN.     

Correlation of MRI and histomorphological findings in bone marrow oedema syndrome of the hip

Bone marrow oedema syndrome (BMOS) of the hip includes severe hip joint pain, focal loss of radiodensity in radiographs, increased uptake in bone scintigrams and the pattern of bone marrow oedema in the femoral heads in MRI scans. In 15 patients (16 hip joints) we found the clinical and radiological signs of BMOS. On T1-weighted MRI images areas of low signal intensity could be observed in the head, neck and the intertrochanteric region of the femur in various extensions. These areas showed a significant increase in signal intensity on the T2-weighted images. Because pain was resistant to conservative therapy all these patients were treated by core decompression of the femoral head in a prospective study. Bone cores were evaluated histologically using undecalcified sections and quantitative microradiography. The existence of intramedullary oedema in exactly the regions exhibiting the MRI pattern of bone marrow oedema was verified histologically; however, bone and marrow changes similar to those of early avascular necrosis (AVN) were also visible. These findings support our assumption that BMOS might be a transitory initial phase of AVN. Therefore core decompression treatment for patients suffering pain from BMOS is recommended after excluding other diseases.     

Screening for avascular necrosis of the hip with rapid MRI: preliminary experience

PURPOSE: The purpose of this work was to compare rapidly acquired MR images with routinely employed SE and turbo SE (TSE) images in screening for hip avascular necrosis (AVN). METHOD: Twelve patients with findings suspicious for radiographically occult AVN of one or both hips were studied with our routine screening protocol (imaging time >7 min) and similarly weighted, rapidly acquired MR sequences (imaging time <1 min). RESULTS: The rapidly acquired MR images were judged to be similar to the routine protocol in demonstrating marrow edema, irregular lines within the femoral head characteristic of AVN, and osteoarthritis. CONCLUSION: The rapidly acquired MR sequences that we studied reliably revealed the presence or absence of AVN, marrow edema, and osteoarthritis of the hip in our sample population when compared with SE and TSE sequences that we routinely perform. Further investigation of rapidly acquired MR sequences is warranted, as imaging time may be dramatically reduced and patient throughput increased.     

Potential pitfalls of magnetic resonance imaging in the diagnosis of avascular necrosis

Magnetic resonance (MR) imaging and radionuclide (RN) bone scans were performed in two patients with collagen vascular disease (CVD) to evaluate hip pains. In both patients RN bone scans demonstrated decreased radioactivity in the femoral heads, whereas, MR imaging was normal. Because early changes of avascular necrosis (AVN) frequently present as decreased radioactivity in the femoral head, special attempts were made to detect this decreased activity using pinhole collimator imaging. The diagnosis of AVN was confirmed surgically by venous pressure measurements. Abnormal RN bone scans representing decreased flow due to vasculitis in patients with CVD, may be more sensitive in the diagnosis of AVN before structural changes can be detected on MR studies.     

Correlation between bone marrow edema and collapse of the femoral head in steroid-induced osteonecrosis

OBJECTIVE: The purpose of this study was to clarify whether bone marrow edema is detectable on initial MR imaging of steroid-induced osteonecrosis of the femoral head. SUBJECTS AND METHODS: Forty-eight hips with osteonecrosis were examined consecutively with MR imaging and radiography. In a previously reported screening program, osteonecrosis was diagnosed on MR imaging when subchondral bands of abnormal signals were present. In the screening program, the MR images of 200 hips of 100 patients receiving high-dose steroid therapy were examined prospectively. Subchondral bands were detected in 48 hips at a mean of 14 weeks after the initiation of steroid therapy. RESULTS: On follow-up MR imaging of 47 hips (one hip excluded) bone marrow edema was initially observed in 13 hips after the onset of hip pain. MR imaging of the remaining 34 hips did not reveal bone marrow edema and the patients were all asymptomatic. MR imaging of 31 of the 34 hips continued to show subchondral bands and MR imaging of the other three hips indicated that the subchondral bands had disappeared. When bone marrow edema was detectable, abnormal findings on radiography were slight but 11 (85%) of the 13 hips progressed to advanced osteonecrosis. Bone marrow edema was highly correlated with the subsequent collapse of the femoral head (p<0.0001). CONCLUSION: Bone marrow edema was not present on initial MR imaging of osteonecrosis. Bone marrow edema should be considered a marker for potential progression to advanced osteonecrosis, and careful examinations for osteonecrosis are necessary when bone marrow edema is seen.     

Subchondral insufficiency fracture of the femoral head: magnetic resonance imaging findings correlated with micro-computed tomography and histopathology

We described magnetic resonance (MR) imaging findings of subchondral insufficiency fracture of the femoral head without collapse in which micro-computed tomography (CT) and histopathologic studies were performed. Magnetic resonance imaging showed a subchondral low-signal intensity band, which corresponded to the fracture callus. Diffuse bone marrow edema with contrast enhancement effect was seen in both the proximal and distal segments of the low-signal intensity band. These features are distinct from those of avascular necrosis.     

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.     

Subchondral insufficiency fractures of the femoral head

The aim of this study was to increase awareness of, and to show the variable clinical and radiological features of, subchondral insufficiency fractures of the femoral head. The clinical and radiological findings in 7 patients with subchondral insufficiency fractures of the femoral head were reviewed retrospectively. The diagnosis was confirmed histologically in 4 patients. Radiographs were performed in all patients, MRI in 5 and scintigraphy in 4 patients. Radiographs showed varying degrees of femoral head collapse in 4 patients. In the remaining 3 patients radiographs showed a normal femoral head, regional osteoporosis and focal sclerosis, respectively. Magnetic resonance imaging showed a low-signal band on T1- and T2-weighted images in the subchondral bone adjacent or parallel to the articular surface associated with bone marrow oedema. Scintigraphy showed increased uptake in the femoral head. Insufficiency fractures of the femoral head are easily overlooked or confused with avascular necrosis and, when there is significant joint destruction, osteoarthritis. Unsuspected insufficiency fracture of the femoral head can lead to significant and rapid loss of bone stock in osteoporotic patients waiting for arthroplasty for osteoarthritis. Increased awareness of this condition will hopefully lead to earlier diagnosis and a successful outcome of conservative treatment.     

Bone marrow perfusion evaluated with gadolinium-enhanced dynamic fast MR imaging in a dog model

The authors studied, in a dog model, the feasibility of using gadolinium-enhanced dynamic magnetic resonance (MR) imaging to noninvasively monitor bone marrow perfusion of the proximal femur. With a gradient-recalled acquisition, sequential images of 10 hips in five healthy dogs were obtained for 14 minutes after an intravenous bolus injection of 0.2 mmol of gadopentetate dimeglumine per kilogram. The study was repeated after unilateral arterial embolization of major femoral vessels. Radiolabeled microspheres were injected before and after vessel occlusion. After unilateral embolization, statistically significant differences in enhancement were observed between embolized and control sides (eg, 31% vs 83% average peak enhancement in the femoral neck). There was a high correlation (r = .81 [average]) between the MR data and the microsphere blood flow measurements. The postembolization data indicate that contrast-enhanced fast MR imaging may allow early detection of abnormal bone marrow flow. This technique may be valuable in evaluating patients at risk for avascular necrosis of the femoral head, especially in posttraumatic cases.     

The role of MR imaging in avascular necrosis of the femoral head

Due to the pattern of its blood supply, the femoral head is particularly vulnerable to avascular necrosis (AVN). Nontraumatic AVN is a devastating disorder affecting young patients, and despite treatment it normally follows a progressive course toward a destructive osteoarthropathy. Magnetic resonance (MR) imaging is currently used in major classification systems solely for early detection of femoral head AVN when plain radiographs are normal. More recent data have shown that MR imaging may improve staging, investigate radiologically occult collapse, depict other causes of disability and pain, assess prognosis, and evaluate treatment. This article reviews the established and evolving role of MR imaging in patients at risk or with known femoral head AVN.     

成人股骨头缺血性坏死合并骨髓水肿的介入治疗

目的探讨成人股骨头缺血性坏死合并骨髓水肿的介入治疗及其疗效观察。方法选择临床症状突出,经磁共振成像（MRI）检查证实的成人股骨头缺血性坏死合并骨髓水肿的患者20例,24髋,经对侧股动脉插管,分别超选择至患侧旋股内、外动脉,闭孔动脉开口,造影确定导管位置后,灌注溶栓剂、解痉剂及血管扩张剂等。结果①经2次或3次介入灌注术后与灌注前造影片对比,股骨头颈部血管增多、增粗、股骨头染色变深16例22髋,2例2髋改变不明显。②本组20例中有19例患者疼痛消失、明显减轻或缓解,总有效率占95％。③24个髋关节介入治疗前后活动范围均有不同程度改善。④16髋介入治疗后MRI对比,骨髓水肿明显减轻。结论介入灌注术治疗股骨头缺血性坏死合并骨髓水肿疗效确切。     

Avascular necrosis of bone in severe acute respiratory syndrome

AIM: To report the incidence of avascular osteonecrosis (AVN) in severe acute respiratory syndrome (SARS) patients. MATERIALS AND METHODS: Sixty-seven SARS patients who had large joint pain between March 2003 and May 2003 underwent both plain radiographs and magnetic resonance imaging (MRI) examination on the same day. All patients received steroids and ribavirin treatment. All plain radiographs and MR images were analysed by two experienced musculoskeletal radiologists. Any abnormalities, location, extent, morphology, the number, size and signal intensity of lesions were evaluated. RESULTS: Twenty-eight patients were identified with AVN, The mean time to diagnosis of AVN was 119 days after the onset of SARS, or 116 days after steroid use. Three patients had early bilateral AVN of the femoral head, four patients of one femoral head, five patients of the bilateral hips and knees, four patients of the ipsilateral hip and knees, 10 patients of the knee(s), one patient of the right proximal fibula, and one patient of the knees and talus. Results of hip, knee and ankle plain radiographs were negative. CONCLUSION: AVN can occur in the patients with SARS. AVN had a strong association with steroid use. More studies are required to confirm whether the virus itself can also lead to AVN.     

Magnetic resonance imaging of avascular necrosis of the femoral head

This study investigates the role of magnetic resonance imaging (MR) in identifying avascular necrosis (AVN) of the femoral head and in monitoring its therapy. The detection of AVN, particularly in its early stages, is imperative to give therapeutic intervention the best opportunity for successful management. The results of magnetic resonance imaging are compared with those of the standard diagnostic modalities in evaluation of patients with the lesion. Examinations were performed at 0.12 T with a repetition time (TR) of 143 ms and times to echo (TE's) of 10 or 20 ms. This study represents a retrospective review of 90 hips which were examined in 45 consecutive patients. Of these, 52 hips were biopsied as part of treatment. MR was shown to be sensitive in the detection of AVN. Comparison of MR with radionuclide imaging showed comparable sensitivity and specificity. MR was also noted to be sensitive in the detection of early AVN. Preliminary results suggest that MR can monitor treatment of the affected hip, and may even be able to predict patient response to therapy. Although further work is necessary to determine the role of MR in the evaluation of the patient presenting with hip pain, MR is a sensitive method in detecting AVN and in monitoring its course in patients suspected of having the disease.