Fatigue Stress Fractures of the Pubic Ramus in the Army: Imaging Features with Radiographic, Scintigraphic and MR Imaging Findings

Although fatigue fractures are not unusual in athletes and military personnel those of the pubic ramus are rare. We report three cases of fatigue fractures of the inferior pubic rami in two male recruits and one female military cadet. On the initial radiograph, most of the lesions were subtle and easy to overlook. However, bone scintigraphy provided more distinct images that allowed easy and early detection of lesions, and MR imaging presented more diagnostic information, which allowed a precise diagnosis.

Giant Cell Tumor of Short Tubular Bone: Case Report

Giant cell tumors of the bone commonly occur in the epiphyseal scar of a long tubular bone, representing about 5% of all primary bone tumors. A short tubular bone, such as one in the hand or foot, is the site of less than 5% of all giant cell bone tumors. The authors report two cases in which giant cell tumors arose in the short tubular bone, and describe the clinical manifestations and radiologic findings.

MRI Findings of Dysplasia Epiphysealis Hemimelica: A Case Report

Dysplasia epiphysealis hemimelica, also known as Trevor's disease, is a rare disorder characterized by osteochondral overgrowth of one or more epiphyses and usually affecting the lower limbs. It typically presents in childhood, with painless swelling or deformity around the involved joint. We report a case of recurrent dysplasia epiphysealis hemimelica which presented as a large popliteal mass four years after excision of the initial lesion.

Imaging of Melorheostosis: Emphasis on MR Imaging Findings

PURPOSE: To evaluate the usefulness of various radiographic imaging modalities in the diagnosis and characterization of melorheostosis. MATERIALS AND METHODS: We retrospectively evaluated the plain film (n=8), computed tomographic (CT) imaging (n=5) and magnetic resonance (MR) imaging (n=5) findings of eight patients with melorheostosis diagnosed by bone biopsy (n=4) and characteristic radiographic findings (n=8). MR images were obtained with a 1.5-T scanner focused on the region of maximal radiographic abnormality. Pulse sequences include T1-weighted SE, T2-weighted fast SE (n=5) and postcontrast imaging (n=4). In order to define subtle enhancement of the lesions, subtraction MR images were obtained in one case. Imaging findings were analyzed with particular emphasis on the distribution of lesions along the sclerotome, differential radiographic findings between diaphyseal and metaepiphyseal lesions of the long bones, as seen on plain radiographs, and the density and signal characteristics of hyperostotic, lesions, as seen on CT and MR images. RESULTS: Characteristic distribution along the sclerotome was identified in five of eight cases mainly along C6 and 7 (n=2) and L3, 4 and 5 (n=3) sclerotomes. In diaphyseal melorherostosis (8/8), a characteristic finding, i.e., a wax flowing down from the candle, was identified on plain radiographs. In all three patients with metaepiphyseal melorheostosis (3/8), multiple round or oval hyperostotic lesions were seen in the epiphysis and metaphysis of the long bones. On CT, the marrow cavity was partly obliterated by hyperostotic lesions in all five patients with endosteal hyperostosis. Among these, central ground glass opacity with a sclerotic rim was seen in three patients. Periosteal hyperostosis was seen in two of five cases, being visualized as irregular excrescences in the periosteal region and surrounding soft tissue. Individual hyperostosis was visualized as hypointense on T1-weighted images and as a hyperintense center with a surrounding hypointense rim on T2-weighted images (5/5). On postcontrast images, central enhancement was noted in all four cases. In one of these, in which the degree of central enhancement was subtle, subtraction images (postcontrast SE- precontrast SE) also revealed a central signal increment. Central enhancement corresponded to the hyperintense center seen on T2-weighted images (4/4) and the ground-glass opacity seen on CT (2/2). CONCLUSION: Radiographic imaging plays a crucial role in the diagnosis of melorheostosis. The future role of gadolinium-enhanced MR imaging in the characterization of the lesion may be important though further evaluation and pathologic correlation is required.

MRI Findings of Malignat Lymphoma Presenting in Bones

PURPOSE: To analyze the MR finding of skeletal malignant lymphoma. MATERIALS AND METHODS: The authors retrospectively reviewed the MR imaging findings(location, signal intensity and contrast enhancement of lesions, and patterns of bone marrow involvement) of 12 patients with malignant lymphoma presenting in bones and confirmed by incisional biopsy, blind bone marrow biopsy or fol-low-up MR imaging. RESULTS: Among the 15 lesions in 12 patients, the spine was the most commonly involved site(n=5), followed by the ilium(n=4), femur(n=3), sternum(n=2), and tibia(n=1). On T1-weighted images, lesions showed signal intensity close to muscle, while on T2-weighted images, involved bones showed variable signal intensity from muscle to water signal intensity. Patterns of bone marrow involvement were nodular(n=2), diffuse(n=5), or segmental(n=8). All cases of segmental bone marrow involvement also produced soft tissue mass. In two cases in which this occurred, cortical breakdown was not noted. CONCLUSION: On T1- and T2-weighted MR images, particularly the latter, bone marrow involvement of malignant lymphoma was observed, with variable signal intensity. Contrast enhanced images revealed distinct lesion. Patterns of bone marrow involvement varied.

Correlation between MR Imaging and Histopathologic Findings in Acute Osteomyelitis: Experimental Study in Rabbits

PURPOSE: We compared the sequential characteristic MR findings with histopathologic findings in experimentally induced osteomyelitis of rabbits tibiae . MATERIALS AND METHODS: We induced osteomyelitis in the left tibiae of 25 rabbits by direct inoculation of E. coli. Right tibiae of the same rabbits were directly punctured with sterile needle, which were used as control groups. Spin-echo sagittal T1- and T2-weighted images(T1WI & T2WI) and gadolinium-enhanced T1-weighted sagittal images of both tibiae were obtained at 3 days, 5 days, 1 week, 2 weeks, and 4 weeks following inoculation of pathogen. MR-pathologic correlation study was done with emphasis on changes of the morphology and the MR signal intensity(SI) of marrow abscess. RESULTS: Well-defined abscesses were seen on MR 3 -5 days after pathogen inoculation and they all showed low SI on both T1 & T2WI and no enhancement. MR imaging of abscess wall, which became visible at 3 days as high SI on T1WI, gradually changed to low SI on T1WI and high SI on T2WI with diffuse enhancement according to the time sequence (17% after 3 days; 40% after 5 days; 46% after 1 week; 56% after 2 weeks; 60% after 4 weeks). The peripheral portion of the abscess, which was seen in some cases (48% after 3 days; 40% after 4 weeks), showed iso-intensity to muscle on T1WI and ill-defined high SI on T2WI with mild Gd-enhancement. Pathologically the abscesses and their walls were composed of cell debris and granulation tissue with infiltration of inflammatory cells. Fibroblasts and acute inflammatory cells in the abscess wall, which were most prominent at 3 and 5 days relatively, decreased gradually along with the development of abscess. Inner layer of the abscess wall was composed of chronic inflammatory cells, which appeared after 2 weeks of inoculation. The granulation tissue and inner chronic inflammatory cell layer became more organized feature after 4 weeks. The peripheral portion of the abscess revealed as granulation tissue. In the control group, necrosis or inflammatory cell infiltration was absent and the lesion decreased in size to remain only focal fatty change of bone marrow after 4 weeks. CONCLUSION: Central abscess composed of cell debris showed low SI on both T1 & T2WI without enhancement. Granulation tissue of the abscess wall showed more organized feature forming inner layer of chronic inflammatory cells along with the progression of osteomyelitis. Abscess showed hyperintensity on T1WI in the early stage, but changed to hypointensity on T1WI, hyperintensity on T2WI in later stage.

Correlation between MR Imaging and Histopathologic Findings in Acute Osteomyelitis: Experimental Study in Rabbits

PURPOSE: We compared the sequential characteristic MR findings with histopathologic findings in experimentally induced osteomyelitis of rabbits tibiae . MATERIALS AND METHODS: We induced osteomyelitis in the left tibiae of 25 rabbits by direct inoculation of E. coli. Right tibiae of the same rabbits were directly punctured with sterile needle, which were used as control groups. Spin-echo sagittal T1- and T2-weighted images(T1WI & T2WI) and gadolinium-enhanced T1-weighted sagittal images of both tibiae were obtained at 3 days, 5 days, 1 week, 2 weeks, and 4 weeks following inoculation of pathogen. MR-pathologic correlation study was done with emphasis on changes of the morphology and the MR signal intensity(SI) of marrow abscess. RESULTS: Well-defined abscesses were seen on MR 3 -5 days after pathogen inoculation and they all showed low SI on both T1 & T2WI and no enhancement. MR imaging of abscess wall, which became visible at 3 days as high SI on T1WI, gradually changed to low SI on T1WI and high SI on T2WI with diffuse enhancement according to the time sequence (17% after 3 days; 40% after 5 days; 46% after 1 week; 56% after 2 weeks; 60% after 4 weeks). The peripheral portion of the abscess, which was seen in some cases (48% after 3 days; 40% after 4 weeks), showed iso-intensity to muscle on T1WI and ill-defined high SI on T2WI with mild Gd-enhancement. Pathologically the abscesses and their walls were composed of cell debris and granulation tissue with infiltration of inflammatory cells. Fibroblasts and acute inflammatory cells in the abscess wall, which were most prominent at 3 and 5 days relatively, decreased gradually along with the development of abscess. Inner layer of the abscess wall was composed of chronic inflammatory cells, which appeared after 2 weeks of inoculation. The granulation tissue and inner chronic inflammatory cell layer became more organized feature after 4 weeks. The peripheral portion of the abscess revealed as granulation tissue. In the control group, necrosis or inflammatory cell infiltration was absent and the lesion decreased in size to remain only focal fatty change of bone marrow after 4 weeks. CONCLUSION: Central abscess composed of cell debris showed low SI on both T1 & T2WI without enhancement. Granulation tissue of the abscess wall showed more organized feature forming inner layer of chronic inflammatory cells along with the progression of osteomyelitis. Abscess showed hyperintensity on T1WI in the early stage, but changed to hypointensity on T1WI, hyperintensity on T2WI in later stage.

MR Evaluation of Pyo genic Osteomyelitis Involving the Epiphyses

PURPOSE: The purpose of this study was to analyze of the MR findings of the pyogenic osteomyelitis involving the epiphyses of the long bones in childhood. MATERIALS AND METHODS: Eleven childen with pyogenic osteomyelitis involving the epiphyses of the long bones were evaluated by MRI. A diagnosis of pyogenic osteomyelitis was established by biopsy and culture in eight cases and during follow-up after antibiotic treatment in three. We analyzed the involved bone, initial location, pattern, degree of growth plate involvement, degree of epiphyseal involvement, surrounding change and plain radiographic findings. RESULTS: The involved bones were the proximal femur in four cases, distal femur in two, proximal tibia in two, distal tibia in one, distal fibula in one and proximal humerus in one. The initial site of the lesion was the metaphysis in ten cases and epiphysis in one. The lesion pattern was the Brodie's abscess in six cases and osteomyelitis in five. The degree of growth plate involvement was 16-20% in five case and 5% or less in four ; the degree of epiphyseal involvement was 5% or less in four cases, 6-10% in four and 11-15% in two. All cases showed low or intermediate signal intensity on T1-weighted images, high signal intensity on T2-weighted images, and contrast enhancement. Joint effusion adjacent to the lesion was detected in five cases. Radiographic findings of the involved epiphysis were normal in six cases, but indicated osteolytic lesion in four cases and sclerosis in one. CONCLUSION: Pyogenic osteomyelitis involving the epiphyses of the long bones in childhood usually developed from metaphyseal osteomyelitis and was combined with destruction of the growth plate.

MR Evaluation of Pyo genic Osteomyelitis Involving the Epiphyses

PURPOSE: The purpose of this study was to analyze of the MR findings of the pyogenic osteomyelitis involving the epiphyses of the long bones in childhood. MATERIALS AND METHODS: Eleven childen with pyogenic osteomyelitis involving the epiphyses of the long bones were evaluated by MRI. A diagnosis of pyogenic osteomyelitis was established by biopsy and culture in eight cases and during follow-up after antibiotic treatment in three. We analyzed the involved bone, initial location, pattern, degree of growth plate involvement, degree of epiphyseal involvement, surrounding change and plain radiographic findings. RESULTS: The involved bones were the proximal femur in four cases, distal femur in two, proximal tibia in two, distal tibia in one, distal fibula in one and proximal humerus in one. The initial site of the lesion was the metaphysis in ten cases and epiphysis in one. The lesion pattern was the Brodie's abscess in six cases and osteomyelitis in five. The degree of growth plate involvement was 16-20% in five case and 5% or less in four ; the degree of epiphyseal involvement was 5% or less in four cases, 6-10% in four and 11-15% in two. All cases showed low or intermediate signal intensity on T1-weighted images, high signal intensity on T2-weighted images, and contrast enhancement. Joint effusion adjacent to the lesion was detected in five cases. Radiographic findings of the involved epiphysis were normal in six cases, but indicated osteolytic lesion in four cases and sclerosis in one. CONCLUSION: Pyogenic osteomyelitis involving the epiphyses of the long bones in childhood usually developed from metaphyseal osteomyelitis and was combined with destruction of the growth plate.

Distal Femoral Cortical Irregularity in Adult: MR Imaging and Pathologic Correlation

PURPOSE: To correlate the pathologic and MR findings of distal femoral cortical irregularity(DFCI) in adult. MATERIALS AND METHODS: We retrospectively reviewed knee MR images of 120 adult patients(25-62 years old) without infection, tumor, or fracture. Five femoral specimens of adult cadaver were used to correlate pathologic and MR findings. A double cortical line' on MR images was interpreted as DFCI, and MR findings were analyzed to determine the thickness, internal signal intensity, location of the DFCI, shape of the external cortex, and clarity of the inner cortex. The outer cortex was classified as either convex or flat, and the inner cortex was classified according to its thickness and continuity as one of three types. RESULTS: One hundred and sixteen patients(97%) had DFCI, which in all cases was observed at the attachment site of the medial head of the gastrocnemius muscle. Mean thickness was 3.7mm and DFCI was thicker in men than in women(p<0.05). The outer cortex was convex in 75 cases(65 %) and flat in 41(35 %). The inner cortex was thick and continuous in 47cases(41 %, mean age 31), thin and continuous in 54(47 %, mean age 38), and thin and discontinuous in 19(16 %, mean age 47). Clarity tended to diminish with age. The internal area of DFCI showed signal intensity equal to that of adjacent bone marrow and was pathologically proven to be normal marrow tissue. CONCLUSION: DFCI was observed in most adults and was considered to be a normal variation. Its MR and pathologic findings were different to those observed during periods of growth.

Simple Bone Cyst involving Proximal Epiphysis of the Humerus: A Case Report

Simple or unicameral bone cysts are metaphyseal lesions of long bones. They usually move away from the physiswith growth to become diaphyseal in location. Involvement of the physis and epiphysis by these cystic lesions isvery rare. This paper reports a case of simple bone cyst of the proximal humerus in a 11- year -old girl which wasshown by MR imaging to extend through the physis into the epiphysis.

Brodie's Abscess in Pediatric Patients: MR Imaging Findings

PURPOSE: To determine the characteristic MR imaging findings of Brodie's abscess in pediatric patients. MATERIALS AND METHODS: We retrospectively reviewed 17 pediatric patients with surgically-proven or clinically and radiologically diagnosed Brodie's abscess who had undergone T1- and T2-weighted spin-echo sequences, T2-weighted fast spin-echo sequence and gadolinum enhanced MR imaging. The MR imaging findings were analysed and classified according to the signal characteristics of the abscess and srrounding bone marrow. RESULTS: The MR imaging findings of Brodie's abscess could be classified as one of three types, as follows : Type I (10/17) was seen as a target appearance with four layers ; i.e. a center with low signal intensity on T1-weighted images and high signal intensity on T2-weighted images; an inner rim of high signal intensity, as compared with muscle on both T1- and T2-weighted images with intense contrast enhancement; an outer rim of low signal intensity on both T1- and T2-weighted images, and a peripheral halo of low signal intensity on T1-weighted images and variable signal intensity on T2-weighted images. In type II (4/17), there was no distinction between the center and the inner rim on T1-weighted images, but a clear distinction on contrast enhanced images by intense enhancement of the inner rim. In type III (3/17), there was no distinction between the center and the inner rim on either T1-weighted or contrast enhanced images, due to diffuse enhancement of the lesions. Additional findings of Brodie's abscess include epiphyseal plate violation (8/17), linear or tubular sinus tracts (7/17), inflammatory reaction or edema of surrounding soft tissue (7/17), periosteal reaction (1/17), and pyogenic arthritis (1/17). CONCLUSION: MR imaging is a useful diagnostic tool for the characterization and determination of the extent of Brodie's abscess. Contrast enhanced MR imaging is particularly valuable for the evaluation of type II lesions.

Diaphyseal Osteomyelitis of the Long Bone: Evaluation of Radiograph and MRI

PURPOSE: To describe the radiographic and MR characteristics of subacute diaphyseal osteomyelitis of the long bone. MATERIALS AND METHODS: We retrospectively analyzed plain radiographs and MR images in nine children and two young adults with surgically-proven diaphyseal osteomyelitis of the long bones. MR imaging was carried out before and after Gd-DPTA administration. Patients charts were reviewed for clinical and laboratory data and histologic correlation was available in all cases. RESULTS: All patients had a history of a minimum of 2 weeks' duration. All presented with an insidious onset of mild pain; they showed apyrexia and normal erythrocyte sedimentation rate. In all patients, plain radiographs showed single or multiple linear periosteal reaction with cortical irregularity. Medullary abnormality was not found except in one case which showed an abscess cavity. MR images revealed thickening or irregularity of the cortex, periosteal reaction, bone marrow signal alteration, and perilesional edema. CONCLUSION: Subacute diaphyseal osteomyelitis of the long bone is broadly based on the cortex, and elicits more sclerosis and periosteal reaction. Familarity with plain radiographs and MR features may be useful in the diagnosis of subacute diaphyseal osteomyelitis.

MR Findings of Fibrous Dysplasia

PURPOSE: To describe the MR findings of fibrous dysplasia. SUBJECTS AND METHODS: MR images of fibrousdysplasia in 13 pathologically proved cases were retrospectively analyzed regarding the signal intensity, hypointense rind, internal septations, cortical disruption, soft tissue extension, and the pattern of contrast enhancement. RESULTS: All cases showed low signal intensity on T1-weighted images. On T2-weighted images, 8cases(62%) were hyperintense and 5 cases(38%) hypointense. Hypointense rind was seen in 10 cases(77%), internal septations in 3 cases(23%), and cystic change in 2 cases(15%). Soft tissue extension was observed in fourcases(31%) including one case with pathologic fracture. After Gd-DTPA infusion, central contrast enhancement wasnoted in 8 cases(73%) and peripheral rim enhancement in 3 cases(23%). Pathologically, hypointensity on T2-weighted images was due to numerous bony trabeculae. CONCLUSION: Hypointensity on T1W1 and hyperintensity(62%) or hypointensity(38%) on T2W1 as well as contrast enhancement in fibrous dysplasia depend on degree of cellularity, collagen, cystic and hemorrhagic changes, and bony trabeculae.