Magnetic resonance imaging and histopathology in femoral head necrosis

We correlated preoperative magnetic resonance (MR) images and histopathology of eight femoral heads from patients with osteonecrosis. The signal intensity of the MR image was low in the area where fibrovascular tissue, disintegrated fibrovascular tissue, or amorphous necrotic material occupied the medullary space. On the other hand, the necrotic marrow without revascularization showed high signal intensity. Osteonecrosis can be detected by MR imaging as soon as a certain amount of bone marrow is replaced by fibrovascular tissue.     

Magnetic resonance imaging and histopathology in femoral head necrosis

We correlated preoperative magnetic resonance (MR) images and histopathology of eight femoral heads from patients with osteonecrosis. The signal intensity of the MR image was low in the area where fibrovascular tissue, disintegrated fibrovascular tissue, or amorphous necrotic material occupied the medullary space. On the other hand, the necrotic marrow without revascularization showed high signal intensity. Osteonecrosis can be detected by MR imaging as soon as a certain amount of bone marrow is replaced by fibrovascular tissue.     

Magnetic resonance imaging in osteonecrosis of the femoral head

Magnetic resonance imaging (MRI) has been used in the assessment of patients with osteonecrosis of the femoral head. Preliminary results indicate that the technique is sensitive to early changes that occur within marrow elements as well as to later changes that involve trabecular bone. Advantages of MRI include its noninvasiveness, the lack of ionizing radiation, a high sensitivity to pathologic changes in bone, and the capability of producing images of equal resolution in all planes.     

Magnetic resonance imaging and histology of repair in femoral head osteonecrosis

Different repair processes affect the clinical course of nontraumatic avascular femoral head osteonecrosis, not just necrotic lesion size and location. Fourteen femoral heads were retrieved at total hip arthroplasty after core decompression treatment, or after conservative treatment was done on 13 male patients diagnosed with different stages of femoral head osteonecrosis. To determine repair types, features of coronal magnetic resonance images were correlated with light microscopy findings on corresponding coronal undecalcified sections and microradiographs of the retrieved femoral heads. In five femoral heads, repair of necrotic bone and marrow remained restricted to the reactive interface for as many as 63 months, producing the diagnostic osteosclerotic rim with adjacent hypervascularity (limited repair). Nine femoral heads showed extension of the repair process into the necrosis. In five femoral heads, predominant resorption of necrotic bone led to femoral head breakdown within 2 to 50 months (destructive repair). In four femoral heads, reparative bone formation had started from subchondral fractures and/or the reactive interface, definitely reducing the size of the necrotic area (reconstructive repair). In the latter, the disease progressed slowly or stopped for as many as 45 months, irrespective of treatments, but elimination of risk factors seemed beneficial. Although core decompression did not always reach the necrotic area and improve repair, it reduced accompanying bone marrow edema and could delay the disease progress. Osteonecrosis with limited repair can be identified on magnetic resonance images obtained at followup, but the similar signal changes of destructive and reconstructive repair cannot be distinguished on magnetic resonance images alone. The evidence of reconstructive repair in nontraumatic osteonecrosis, however, gives hope for treatments that can improve repair to a sufficient creeping substitution of the affected femoral head.     

Magnetic resonance imaging of the femoral head after acute intracapsular fracture of the femoral neck

In fifteen patients who had a subcapital fracture of the femoral neck (twelve displaced fractures and three non-displaced fractures), magnetic resonance imaging of the femoral head was done with two-dimensional Fourier transform spin-echo technique within forty-eight hours of injury. The magnetic resonance image did not show avascular necrosis of the femoral head in any of the patients. In eleven patients, there was a decreased signal at the base of the femoral head, immediately adjacent to the fracture. This decreased signal corresponded to a recognized band of necrosis and hemorrhage next to the site of the fracture and was not related to the viability of the femoral head. No other changes were seen on the images. We concluded that this type of magnetic resonance imaging is inadequate to determine the viability of the femoral head within forty-eight hours after a patient sustains an acute intracapsular fracture of the femoral neck.     

Magnetic resonance imaging of the head and neck

Magnetic resonance imaging (MR) has already gained wide acceptance in the evaluation of intracranial and spinal canal abnormalities. MR also provides excellent resolution of certain tumors of the head and neck and is particularly useful for the evaluation of neoplasms in the vicinity of the skull base. The absence of a bone signal prevents the streaking artifact so troublesome with computerized axial tomography (CT) and allows better definition of tumor. MR does not use ionizing radiation and appears to be an innocuous imaging mode--thus multiple examinations in young patients are not objectionable with MR. The ability to obtain images in multiple planes by control of the magnetic gradients allows for axial, sagittal, and coronal imaging, without changing the supine position of the patient. Multiple projections are helpful in providing better preoperative assessment of the extent and size of certain neoplasms of the neck.     

Magnetic resonance imaging in the early diagnosis of ischemic necrosis of the femoral head. Preliminary results

Magnetic resonance imaging (MRI) was performed on the hips of 25 patients with suspected ischemic necrosis of the femoral head. Twenty-six femoral heads manifested MRI changes of ischemic necrosis: diminished bone marrow signal in a ringlike, focal, or diffuse pattern. Plain radiographs were normal in 13 of 26 MRI-positive hips; six were asymptomatic. MRI was more effective in detecting early cases than conventional 99mTc-diphosphonate or 99mTc-sulfur colloid (SC) bone scanning. There were no false-negative MRI examinations, but diphosphonate scans were negative in nine hips with normal radiography and abnormal MRI. Sulfur colloid scans were normal in only two hips with positive MRI, but SC scan results were often equivocal because isotope deficits were bilaterally symmetric. The results of this preliminary investigation imply that MRI has extraordinary sensitivity for the detection of early ischemic necrosis. Unlike radionuclide scanning, MRI shows the exact location and extent of femoral head necrosis. Because MRI is expensive, it should be used in a cost-effective manner. Therefore, MRI is best suited for the diagnosis of early cases where less expensive tests are negative or equivocal and as a precursor to more costly interventional procedures, such as core biopsy study or decompression.     

Magnetic resonance imaging after closed head injury in children

Magnetic resonance imaging (MRI) was performed in a series of 21 children and adolescents who had been hospitalized after sustaining closed head injuries of varying severity at least 6 months previously. Areas of high intensity in the parenchyma were present in 8 of the 11 severely injured patients, whereas MRI findings were normal in all 10 patients with mild-to-moderate head injuries. Lesions involving the subcortical white matter were confined to severely injured patients whose clinical features were compatible with diffuse axonal injury. Neuropsychological assessment disclosed deficits primarily in the severely injured patients; these deficits were significantly associated with persistent lesions visualized by MRI. Serial MRI and neurobehavioral assessment following early injury may be useful in documenting cognitive impairment in relation to structural alterations of the young brain.     

Signal variability in magnetic resonance imaging of femoral head osteonecrosis

The present study was designed to document the pattern and extent of magnetic resonance imaging (MRI) changes in femoral head osteonecrosis and also to correlate MRI findings with technetium bone scans and computed tomograms. Over a three-year period, MRI was performed on 26 patients who had clinical and roentgenographic evidence of femoral head necrosis in one or both hips. MRI abnormalities were present in all 41 hips with osteonecrosis, even when symptoms were absent and roentgenographic findings were nonspecific or not yet apparent. A single possible false-positive MRI was noted in a hip with mild degenerative change. There was considerable variation in the pattern and extent of MRI abnormalities. The most common findings were irregularity of the subchondral cortical outline (82.9%), an inhomogeneous pattern of signal loss (50%), focal increases in signal intensity with T2 weighting (35.5%), and effusion (33.3%). Regions of dense cancellous bone on computed tomograms correlated with bands of low-intensity MRI signal. In the diagnosis of asymptomatic hips, MRI was clearly more sensitive than technetium bone imaging. The role of MRI in defining prognosis and treatment selection remains to be established.     

Magnetic resonance imaging in cases of severe head injury

Magnetic resonance imaging (MRI) is an invaluable tool in the evaluation of intracranial and spinal disorders. However, because of various technical limitations, the use of MRI in head-injured patients has yet to be fully explored. With its precise anatomical sensitivity, MRI may be useful in severely head-injured patients in whom computed tomographic (CT) scans fail to demonstrate an anatomical substrate for the degree of coma. In this regard, a prospective study in severely head-injured patients was undertaken. Twenty-four patients with Glasgow coma scores of 7 or less who had minimal or no CT abnormalities and normal intracranial pressures underwent MRI as soon as their medical conditions allowed. In all 24, MRI demonstrated lesions that were not evident on repeated CT scans--suspected white matter shear injuries or contusions in 10, brain stem injuries in 5, diffuse white matter injury in 5, and subdural hematoma in 4. None of the 19 patients with the most widespread MRI abnormalities or the presence of brain stem injuries made any significant neurological recovery. Various prognostic indicators of the outcome of acute posttraumatic coma are continuously being developed. In this group of patients, the MRI scan is the most sensitive measure. Significant MRI abnormalities with normal CT scans and intracranial pressures were universally associated with vegetative outcome in this series. As we gain experience imaging neurotrauma, MRI may form the basis for a better in vivo understanding of the substrate for and natural history of traumatically induced coma.     

Histologic correlation in magnetic resonance imaging of femoral head osteonecrosis

The present study was undertaken to determine whether a correlation exists between localized magnetic resonance image (MRI) signal behavior and specific histopathologic features of femoral head osteonecrosis. Contiguous, 5-mm coronal MRI sections were compared with corresponding histologic sections from six surgically excised femoral heads. After identifying specific areas of interest on the images, signal intensity was evaluated, both subjectively and objectively, and T1 and T2 relaxation times were calculated. Mean values for these data were compared among the following histologic categories: normal bone, unrepaired dead bone and marrow, unrepaired dead bone with marrow replaced by amorphous debris, and zones of repair. For each type of tissue, MRI signal intensity on T1- and intermediately T2-weighted images behaved in a distinctive fashion. Active repair tissue could be differentiated from both necrotic bone and normal bone by a tendency for the signal to increase in intensity on intermediately T2-weighted images. These findings suggest that MRI may provide a noninvasive means of quantitatively analyzing the volume and spacial distribution of repair tissue in osteonecrotic femoral heads. In clinical practice, such analysis may lead to improvements in disease staging and treatment planning.     

Dynamic magnetic resonance imaging of femoral head perfusion in femoral neck fracture.

A prospective followup study of 36 femoral neck fractures according to the assessment of femoral head perfusion using dynamic magnetic resonance imaging is reported. Patients were divided into three groups based on the dynamic magnetic resonance imaging findings (dynamic curve pattern and relative enhancement ratio) that were conducted within 48 hours of the injury. Traction was used to achieve anatomic reduction and to prevent additional damage to vascularity until minimally invasive internal fixation could be done. The fractures of all 17 patients whose femoral head perfusion was normal (Type A; n = 11) or was impaired but not totally absent (Type B; n = 6) healed without complications. Among the 19 patients whose femoral head perfusion was absent (Type C), 15 had complications (osteonecrosis, n = 10; nonunion, n = 5). Assuming that fractures with a Type A or Type B curve pattern would unite successfully and that those with a Type C curve pattern would not, the sensitivity, specificity, and accuracy of the predictions of successful osteosynthesis of the femoral neck fractures using this method were 81%, 100%, and 89%, respectively. The current classification of femoral neck fractures using dynamic magnetic resonance imaging may be useful in selecting an appropriate treatment method for the fractures.     

Center of the femoral head: a magnetic resonance imaging study

Determination of the center of the femoral head (CFH) may be difficult because of incomplete epiphyseal ossification of the femoral head in children younger than 8 years. The purpose of this study is to find a practical method for determining the center of the femoral head in normal hips of children younger than 8 years. Twenty-seven children who had magnetic resonance imaging (MRI) examinations of their hips (N = 54) were reviewed retrospectively. The average age of the subjects was 4.7 years (range, 1.2-8 years). Measurements were performed on the closest section to the midcoronal plane of the femoral head (the widest spherical femoral head seen on the MRI section). The CFH on the MRI section was found using a constructed circular frame by using a computer program. The medial and lateral edges of the proximal femoral ossific nucleus were marked, and the midpoint of the ossific nucleus adjacent to the growth plate (MPON) was determined. The distance between the MPON and the CFH was calculated. The average distance was 1.5 mm (range, 0-5 mm). The distance between these 2 points was less than or equal to 2 mm in 40 hips (74%). In conclusion, this study shows that the MPON can be used as a landmark to determine the center of the femoral head in normal hips of children younger than 8 years and can be used to measure the lower extremity mechanical axis.     

Magnetic resonance imaging and scintigraphy of avascular necrosis of the femoral head. Prediction of subsequent segmental collapse.

For the purpose of an effective management of patients at high risk for nontraumatic avascular necrosis of the femoral head (ANFH), it is expedient to examine the femoral heads of patients most likely to undergo subsequent segmental collapse. The purpose of this study was to evaluate the ability of magnetic resonance imaging (MRI) and radionuclide bone scanning (RS) to predict segmental collapse of the femoral head at the roentgenographically normal stage. Fifty-five hips in 37 patients at risk for ANFH and having normal roentgenograms were included in this study. Magnetic resonance imaging was performed in all hips and RS in 29 hips. The patients were observed during a period of more than two years without any invasive intervention, and nine femoral heads manifested collapse during this period. Predictive values for subsequent segmental collapse of a positive test of MRI and RS were 31% and 13%, respectively, whereas those indicative of a negative test were 100% and 76%, respectively. Magnetic resonance imaging was more useful than RS in detecting patients in need of intensive follow-up examination. In particular, a bandlike area of low intensity that traversed the femoral head in midcoronal slices on MR images seemed to be a significant indicator of subsequent collapse.     

Magnetic resonance imaging of the ischemic femoral head in pigs. Dependency of signal intensities and relaxation times on elapsed time

The magnetic resonance (MR) signal behavior of freshly excised pig femoral heads undergoing ischemic necrosis in vitro was evaluated. Ten femoral heads removed from skeletally immature pigs were stored at 37 degrees in a sealed, sterile container during the observation period. Imaging was initially performed 40 minutes after excision (base-line) and repeated at six, 12, 24, 48, and 72 hours. Changes in MR signal intensity were measured, and the T1 and T2 relaxation times were calculated for selected epiphyseal and metaphyseal areas. Signal intensities decreased during the first 24 hours and returned to baseline by 72 hours. T1 relaxation time increased most significantly between baseline and 24 hours and then decreased to near baseline level between 48 and 72 hours. T2 changes over time were not statistically significant. The type of localized, distinctive decreases in MR signal intensity occurring in clinical cases of early nontraumatic femoral head osteonecrosis was not observed in pigs. Such changes appear to require the presence of an intact and vigorous repair response within adjacent viable bone. However, the transient decrease in signal intensity and prolongation of T1 relaxation time at 12, 24, and 48 hours after traumatic vascular insult may be indicators of early femoral head ischemia.     

The diagnostic value of magnetic resonance imaging in non-traumatic osteonecrosis of the femoral head

To assess the effectiveness of nuclear magnetic-resonance imaging in the detection of osteonecrosis of the femoral head, we studied the cases of twenty-five patients (forty-nine hips) in whom necrosis of the femoral head was suspected on the basis of plain radiographs, computed tomographic scans, radionuclide bone scans, and magnetic resonance-imaging scans. The results of these investigations were compared, for all except one patient, with the pathological findings of transtrochanteric core biopsies of the femoral head and neck of both hips. Of the forty-nine hips, thirty-three had histological proof of osteonecrosis. Twenty-two (67 per cent) of these hips showed definite necrosis on the plain radiographs; eighteen (62 per cent), on the twenty-nine available computed tomographic scans; twenty-four (77 per cent), on the thirty-one available radionuclide bone scans; and all of the hips, on the magnetic resonance-imaging studies. In six additional hips, there were histological changes (marrow necrosis, edema, hemorrhage, and fibrosis) in the medullary spaces without detectable osteonecrosis. The plain radiographs and computed tomographic scans of these six hips were normal except for the computed tomographic scan of one, and the radionuclide uptake on bone-scanning was abnormal in four of the six, as were the magnetic resonance-imaging studies. In the two hips that had normal magnetic resonance-imaging studies, the biopsies showed only destruction of fat cells in the medullary spaces, with no edema or fibroblastic reaction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Magnetic resonance imaging findings in 46 elbows with a radial head fracture

Background and purpose

Radial head fractures are common, and may be associated with other injuries of clinical importance. We present the results of a standard additional MRI scan for patients with a radial head fracture.

Patients and methods

44 patients (mean age 47 years) with 46 radial head fractures underwent MRI. 17 elbows had a Mason type-I fracture, 23 a Mason type-II fracture, and 6 elbows had a Mason type-III fracture.

Results

Associated injuries were found in 35 elbows: 28 elbows had a lateral collateral ligament lesion, 18 had capitellar injury, 1 had a coronoid fracture, and 1 elbow had medial collateral ligament injury.

Interpretation

The incidence of associated injuries with radial head fractures found with MRI was high. The clinical relevance should be investigated.