Posterior root of lateral meniscus: the detailed anatomic description on 3T MRI.

BACKGROUND: Although there have been some attempts to reveal the anatomy of the posterior root of the lateral meniscus (PRLM) through cadaver studies, arthroscopy, or imaging, it has not yet been described fully. PURPOSE: To describe clearly the unique features of the PRLM, including its course, configuration, and size, using 3.0-T magnetic resonance imaging (MRI). MATERIAL AND METHODS: A total of 105 knee 3.0-T MR examinations of 103 patients with arthroscopically proven intact PRLM were reviewed retrospectively. Based on fat-saturated, proton-density-weighted (PDW) axial/coronal images and PDW sagittal images, the course, configuration, and attachment sites of the PRLM were evaluated. RESULTS: The majority of PRLM (76.2%) had two attachment sites: the medial tubercle along the intertubercular crest, just posteromedial to the tibial attachment of the anterior cruciate ligament (ACL), and the posterior slope of the lateral tubercle. The remaining cases (23.8%) had a solitary insertion on the intertubercular area (17 cases), or the posterior slope of the lateral tubercle (eight cases). The PRLM of the intertubercular area appeared as a dark signal line parallel to the tibial plateau on the mid-sagittal image and dark signal foci traversing the intertubercular crest on contiguous coronal images. CONCLUSION: The PRLM inserts mainly in the intertubercular area with a thin, long anterior extension to the point just posteromedial to the tibial attachment of the ACL. It is well delineated on PDW 3.0-T MRI as a dark signal line parallel to the tibial plateau on mid-sagittal images and dark signal foci traversing the intertubercular crest on contiguous coronal images.

Spinous process fractures in osteoporotic thoracolumbar vertebral fractures.

OBJECTIVES: To evaluate the incidence and pattern of spinous process fractures (SPFs) in patients with osteoporotic compression fractures (OCFs) of the thoracolumbar spine. METHODS: Spinal MRI or CT of 398 female patients (age range 50-89 years, mean age 70 years) who had OCFs in the thoracolumbar spine were retrospectively reviewed. The incidence, location and imaging results for the SPFs were evaluated. RESULTS: Of the 398 patients who had thoracolumbar OCFs, 14 (3.5%) had SPF. In six patients with single compression fractures, the SPF occurred at the level just above the vertebral compression fracture. In six out of seven patients with multiple continuous compression fractures, the SPF occurred just one level above the uppermost level of the compression fracture. The remaining one patient who had thoracolumbar spinal fixation at T12-L2 with continuous compression fractures in T12-L5 had a SPF in L2. In one patient who had multiple compression fractures in discontinuous levels (fractures at T10 and L1, respectively), the SPF occurred at T12. The directions of the fractures were vertical or oblique vertical (perpendicular to the long axis of the spinous process) in all cases. CONCLUSION: In the presence of an OCF in the thoracolumbar spine, a SPF was found in 3.5% of cases, and most of the fractures were located just one level above the compression fracture. Therefore, in patients who have OCF, the possibility of a SPF in the level just above the compression fracture should be considered.

Malignant myoepithelioma of the humerus with a satellite lesion: a case report and literature review.

We report an extremely rare case of malignant myoepithelioma presenting as a cortical osseous lesion on the humeral shaft with a satellite lesion. A 21-year-old man presented with persistent pain of the right upper arm after local trauma that had occurred 2 months earlier. Radiological examination revealed an expansile osseous tumour based on the cortex of the humeral shaft as well as a satellite lesion. En bloc resection was performed. Microscopic examination with immunohistochemical staining was used to establish a diagnosis of malignant myoepithelioma. Osseous malignant myoepithelioma occurring in long tubular bones rather than in bony structures with salivary tissue is extremely rare. Here, we demonstrate radiological and pathological features of a malignant myoepithelioma that developed in the cortex of the humeral shaft and review previously reported cases.

Osteonecrosis in patients with systemic lupus erythematosus: MR imaging and scintigraphic evaluation.

This study was to describe the findings of osteonecrosis in patients with SLE at MR and scintigraphic imaging. Among 415 patients with SLE, 37 patients were diagnosed to have osteonecrosis. MR images and bone scintigraphs were analyzed for sites of involvement, signal intensity, bilaterality and multiplicity. MR imaging features of osteonecrosis in patients with SLE included isointense signal intensity relative to adjacent bone marrow, hypointense rim, marginal enhancement and unusual involvement of flat bones. Bilateral and multiple involvements were common.

CT and MR arthrography of the normal and pathologic anterosuperior labrum and labral-bicipital complex.

Interpretation of computed tomographic and magnetic resonance arthrograms of the shoulder is complicated by normal variants of the labrum and glenohumeral ligaments. A superior sublabral recess is located at the 12 o'clock position and represents a normal recess between the superior labrum and the cartilage of the glenoid cavity. A sublabral foramen is located at the 2 o'clock position and represents localized detachment of the labrum from the glenoid rim. Buford complex is characterized by absence of the anterosuperior labrum and cordlike thickening of the middle glenohumeral ligament. Imaging features of damage to the anterior labrum include absence or detachment of the labrum and an irregular frayed appearance. Superior labrum anterior-to-posterior (SLAP) lesions are classified as type I (tear confined to the superior labrum), type II (labrum and biceps tendon detached from the superior glenoid), type III (bucket handle tear of the superior labrum), or type IV (bucket handle tear of the superior labrum with lateral extension into the biceps tendon). Increased distance between the labrum and the glenoid, an irregular appearance of the labral margin, or lateral extension of the separation may suggest a SLAP lesion rather than a normal anatomic variant. However, differentiation between normal variants and pathologic conditions and between various types of SLAP lesions remains difficult.

Subcutaneous and musculoskeletal sparganosis: imaging characteristics and pathologic correlation.

OBJECTIVE: To document the imaging characteristics of subcutaneous and musculoskeletal sparganosis. DESIGN AND PATIENTS: Ten patients with musculoskeletal sparganosis were examined, with a variety of imaging modalities including MRI (n=6), ultrasonography (n=8), plain radiography (n=7) and CT (n=1). Pathologic correlation was carried out in all cases. RESULTS: Nine lesions involved soft tissues, of which seven were in the thigh, two in the trunk and one involved a vertebral body. The majority of the lesions in soft tissue were confined to the subcutaneous layer but two extended deep into underlying muscles. Sonography revealed low-echoic serpiginous tubular tracts (8/8), and an intraluminal echogenic structure (4/8). MRI revealed multiple serpiginous tubular tracts and peripheral rim enhancement. Two patients showed perilesional soft tissue edema. Pathologically, the lesion consisted of a larva surrounded by three layers of inflammation: an inner epithelioid granulomatous cell layer, middle chronic inflammatory cell layers, and an outer fibrous layer. CONCLUSION: The study suggests that if serpiginous tubular tracts are seen at imaging studies, musculoskeletal sparganosis should be included in the differential diagnosis.

Alveolar soft part sarcoma: MR and angiographic findings.

OBJECTIVE: To present the MR and angiographic findings of alveolar soft part sarcoma (ASPS). DESIGN AND PATIENTS: MR examinations (12 tumors of 10 patients) of ASPS performed at multiple hospitals were retrospectively reviewed. The tumors were found in the thigh (n=4), lower leg (n=4), femur (n=2, local metastasis), scalp (n=1) and arm (n=1). The MR signal characteristics including signal intensity, homogeneity and signal void of lesions and bony invasion including direct invasion or local metastasis were evaluated. Angiographic findings (n=4) and post-embolotherapy follow-up MR imaging (n=2) findings were also assessed. RESULTS: Local bony metastasis was found in two cases. Seven tumors showed heterogeneous high signal intensity on T - and T2-weighted images with good enhancement. One tumor had a very high signal on T1-weighted images. Eight tumors (67%) showed numerous signal voids in or near the tumors. All four angiographic studies showed numerous enlarged vessels, arteriovenous shunts and delayed washout. Two cases mimicked arteriovenous malformations on angiographic studies but MR images demonstrated solid soft tissue components as well as tortuous vessels. CONCLUSIONS: High signal on T1 -weighted image and numerous signal voids are highly suggestive of ASPS, although they are not universal as has been suggested and arteriovenous malformation should be included in the differential diagnosis. Local bony metastases in ASPS were seen in two cases and should be carefully investigated.

Bone bruises: MR characteristics and histological correlation in the young pig.

PURPOSE: To correlate magnetic resonance (MR) signal characteristics of bone bruises with histological findings. MATERIALS AND METHODS: In 14 tibiae of young pigs, bone bruises were created in the proximal tibial metaphysis. The signal intensity seen on the MR images were correlated with histological findings. The following findings were evaluated: (a) changes of signal intensity on the tibiae; (b) changes of histology on the tibiae; and (c) changes of (a) and (b) on follow-up examinations. RESULTS: We observed three types of injuries on T1-weighted images: focal or diffuse low signal, normal signal and linear low signal intensities. Severe hemorrhagic areas showed low signal intensities on all sequences of MR imaging. Fast spin-echo (FSE) T2-weighted images showed a more distinct low signal intensity than T1-weighted images. FSE short tau inversion recovery (STIR) and FSE fat saturated (FSE-FS) T2-weighted images showed similar signal intensities with FSE T2-weighted images. FS T1-weighted enhanced images showed low signal intensities with variable enhancements. Upon histological examination, hemorrhages and edemas were prominent at the subcortical areas of the contusion sites. The areas of dense, low signal intensities in all imaging sequences showed signs of severe hemorrhage. The areas of diffuse low signal and enhanced areas showed mixed areas of hemorrhages and edemas. Follow-up MR imaging showed evolution of the processes of hemorrhages and edemas with fatty marrow changes. CONCLUSIONS: MR imaging can depict changes in the bone marrow resulting from direct injury to the bone. MR imaging is a useful tool for evaluating the evolution of bone bruises.

Parosteal osteosarcoma of the scapula.

Parosteal osteosarcoma is a low-grade osteosarcoma, which occurs on the surface of the bone. We had experienced a parosteal osteosarcoma involving the flat bone, the scapula of a 21-year-old man. This is an extremely rare location for a parosteal osteosarcoma. Plain radiograph showed broad-based, well-defined radiodense lesion at the scapula. Computed tomogram demonstrated an intact cortex and absence of a medullary involvement. Tumor showed a lobulated, high-density lesion, indicating bone formation. Histologically, parosteal osteosarcoma is a well-differentiated osteosarcoma. The tumor is composed of a hypocellular proliferation of spindle cells, with minimal cytologic atypia. The bone is in the form of a well-formed bony trabeculae. Occasional cartilage is present in the form of a cap.

Chondroblastoma: MR characteristics with pathologic correlation.

PURPOSE: The purpose of this study was to describe the MR findings of chondroblastoma with pathologic correlation. METHOD: In 22 patients with pathologically proven chondroblastoma, MR signal characteristics were correlated with pathological findings. RESULTS: On T2-weighted images, 12 (55%) lesions were hyperintense with hypointense areas in 9 lesions, whereas 10 (45%) were hypointense. Therefore, 19 of 22 (86%) lesions with pathologic correlation had hypointense areas entirely (n = 10) or partly (n = 9) on T2-weighted images. On gadolinium-enhanced images, 13 (59%) lesions showed lobular enhancement and 9 (41%) showed marginal and septal enhancement. Low signal intensity on T2-weighted MR images was most strongly associated with an abundance of immature chondroid matrix, hypercellularity of the chondroblasts, calcifications, and hemosiderin on histology. CONCLUSION: Chondroblastoma was found to show hypointense portions on T2-weighted images. Signal intensity on T1- and T2-weighted MR images in chondroblastoma was dependent on the amounts of histopathological components.

Spinal involvement of hematopoietic malignancies and metastasis: differentiation using MR imaging.

The purpose of this study was to determine the usefulness of magnetic resonance imaging (MRI) for distinguishing spinal involvement of hematopoietic malignancies (lymphoma, leukemia, and multiple myeloma) from metastasis. 62 spinal MRIs were obtained in 60 patients with hematopoietic malignancies (n = 24) and metastasis (n = 36) in clinically and pathologically proven cases. MRI findings were evaluated in each group of patients for the pattern of involvement, signal change of vertebral body, location of paraspinal mass formation, location of epidural mass formation, cortical destruction, contour change, and compression fracture. Diffuse involvements were more commonly seen in hematopoietic malignancies than in metastasis (p < 0.05). Signal change confined to anterior element was seen in 9 metastasis but was not seen in hematopoietic malignancies. Cortical destructions were more commonly seen in metastasis than in hematopoietic malignancies (p < 0.05). Other findings did not show any statistical significance in both groups. MRI findings such as diffuse involvement, posterior epidural mass formation, and cortical destruction were useful to distinguish spinal involvement of hematopoietic malignancies and metastasis.

Erdheim-Chester disease: a case report.

A 42-year-old man with Erdheim-Chester disease (EC) is presented. This is the first case of this disease reported in Korea. The patient complained of knee pain and plain roentgenogram of the bilateral legs revealed diffusely increased density, coarsened trabecular pattern, and cortical thickening in the diaphysis, and metaphysis as well as epiphysis. Magnetic resonance imaging revealed that the lesions showed low signal intensity on T1-weighted images and heterogeneously low and high signal intensity on T2-weighted images. Histological examination of the biopsy specimen showed a xanthogranulomatous lesion consisting aggregations of foamy histiocytes and Touton-type giant cells. Immunohistochemical staining showed positive reaction to anti-S-100 and lysozyme in the cytoplasm of the giant cells.

Nonossifying fibroma: characteristics at MR imaging with pathologic correlation.

PURPOSE: To correlate the findings of nonossifying fibroma at magnetic resonance (MR) imaging with those at pathologic examination. MATERIALS AND METHODS: In 19 patients (age range, 8-25 years; mean age, 14 years) with pathologically proved nonossifying fibroma, MR images were analyzed for signal intensity and patterns of contrast enhancement. Findings at MR imaging and biopsy were correlated. RESULTS: On T1-weighted images, all nonossifying fibromas had low signal intensity compared with that of skeletal muscle. On T2-weighted images, 15 lesions (79%) were hypointense and four (21%) were hyperintense. On gadolinium-enhanced images, intense contrast enhancement was seen throughout 15 lesions (heterogeneous pattern in 12 and homogeneous in three) and in the margins and septa in four. Extensive hypercellular fibrous tissue and hemosiderin seen at pathologic examination were depicted with low signal intensity on T2-weighted MR images. CONCLUSION: The distinguishing features of nonossifying fibroma included hypointensity and septation on T2-weighted images. Signal intensity on T1- and T2-weighted MR images and the patterns of contrast enhancement were dependent on the amounts of hypercellular fibrous tissue, hemosiderin, hemorrhage, collagen, foamy histiocytes, and bone trabeculae.

MR imaging of tears of discoid lateral menisci.

OBJECTIVE: The purpose of this study was to determine the positive predictive value (PPV) for diagnosis of discoid lateral meniscal tear using MR imaging and to describe various patterns of such tears in the knee. SUBJECTS AND METHODS: MR reports of 77 patients (10-67 years old) who underwent prospective MR imaging that led to a diagnosis of discoid lateral meniscal tear were correlated with arthroscopic results. MR images obtained in 71 patients confirmed to have discoid lateral meniscial tear were retrospectively reviewed for the presence, site, and pattern of discoid lateral meniscal tear, including type of displacement of the torn segment. MR abnormalities were correlated with arthroscopic findings. RESULTS: For the prospective MR interpretations, the PPV for discoid meniscus was 92%. PPV for discoid meniscal tear was 57%. PPVs for individual types of discoid meniscal tears were 46% (peripheral tear, 19/41), 76% (peripheral tear with horizontal tears, 16/21), 56% (horizontal tear, 5/9), 50% (transverse tear, 1/2), 67% (horizontal tear combined with transverse tear, 2/3), and 100% (longitudinal tear, 1/1). Peripheral tear alone and peripheral tear with horizontal tear were the most common types of tears (n = 20, 28%). Multiple tears (n = 34, 48%) were common. Displacement of the torn segments was seen in 51 patients (72%). CONCLUSION: MR imaging has a low PPV for diagnosing discoid lateral meniscal tear. Peripheral tear alone and peripheral tear with horizontal tear were the most common types of tears, and displacement of the torn segment was frequent.

Well-differentiated osteosarcoma of the rib.

Well-differentiated osteosarcoma is extremely rare, there is no sex predominance and the mean age is in the third decade. The tumor has a strong predilection for the long bones of the extremities, especially the metaphysis but may also occur in the diaphysis. Radiologically, the lesion shows no distinctive features, often simulating fibrous dyplasia or desmoplastic fibroma. We report a case of well-differentiated osteosarcoma involving the rib of a 45-year-old female. This is a peculiar case of well differentiated osteosarcoma involving an unusual site and older patient. We also discuss histological differential diagnosis as well as clinical features of this rare disease.

Evaluation of the anterior cruciate ligament of the knee: comparison between partial flexion true sagittal and extension sagittal oblique positions during MR imaging.

OBJECTIVE: To compare partial flexion true sagittal (FS) magnetic resonance (MR) images with extension sagittal oblique (ESO) MR images with regard to delineation of the anterior cruciate ligament (ACL) in the knee. DESIGN: To establish the appropriate degree of flexion of the knee joint, two human cadaveric knee joints were used as a supplementary technique. FS and ESO images then were performed in 17 knees with an intact ACL and six knees with a torn ACL. In 22 of the 23 knees in which the MR diagnosis of intact or torn ACL corresponded to that derived from arthroscopy, the paired MR images were rated by a three-point scale. RESULTS: FS images were rated superior to ESO images in 53%, 41% and 47% of cases with regard to femoral attachment sites, midportions and tibial attachment sites of intact ACLs, respectively. FS images allowed better assessment of disrupted ACLs and residual ligamentous structures. Overall the FS images were either equal to or better than the ESO in the majority of cases. CONCLUSION: FS images are useful when the ACL is not well visualized in initial ESO images.

Elbow effusions: distribution of joint fluid with flexion and extension and imaging implications.

RATIONALE AND OBJECTIVES: The authors study the distribution of elbow joint fluid with flexion and extension of the joint and evaluate the imaging implications of such distribution. METHODS: Three cadaveric elbows were studied with radiography, ultrasonography, and magnetic resonance imaging after the incremental injections of 1 to 15 mL of saline solution into the elbow joint. Imaging was obtained with full flexion and extension of the joint. Anatomic sections were obtained for correlation. RESULTS: In flexion fluid initially collected posteriorly and, with larger quantities, anteriorly. In extension the anterior fat pad was pressed into its fossa and the posterior fat pad was displaced superiorly by the olecranon process. On lateral radiographs in elbow flexion a positive fat pad sign was seen with 5 to 10 mL of fluid in the joint. Sonography allowed identification of 1 to 3 mL of fluid posteriorly with the elbow flexed. Magnetic resonance imaging allowed identification of 1 mL of fluid, regardless of joint position and location. CONCLUSIONS: The distribution of joint fluid in the elbow is influenced by flexion and extension of the joint. Radiography is best performed in flexion. Sonography is more sensitive than radiography in diagnosing effusions, but should be performed along the olecranon fossa with the elbow flexed. Magnetic resonance imaging is most sensitive in identifying effusions, regardless of joint position or location.

Hemophilic pseudotumor: spectrum of MR findings.

OBJECTIVE: To determine the MR imaging appearance of hemophilic pseudotumor (HP) and its clinical implications. DESIGN AND PATIENTS: Five hemophilic patients (aged 35-77 years) with 12 HPs in various anatomic locations were included in this study. The MR images were retrospectively evaluated for the appearance of the lesions and accompanying abnormalities, as well as their clinical implications. RESULTS AND CONCLUSION: MR images of all five patients (12 lesions) showed well-defined masses containing blood clots in various stages of organization surrounded by a fibrous capsule in subcutaneous fat or in intramuscular, interfascial, subperiosteal, and intraosseous locations. Intramuscular HP frequently had mural nodules. This is an almost unique appearance that is somewhat unexpected. MR imaging allowed determination of number, size, and extent of the lesions, evidence of neurovascular involvement, and accompanying musculoskeletal alterations. It is concluded that MR imaging not only is a sensitive and accurate method for detecting and diagnosing HP and providing useful information for therapeutic decision making, but can also be used to assess results of treatment by allowing evaluation of the evolution of blood products, the size of lesions in regions difficult to access by physical examination, and recurrent bleeding within a chronic lesion.

Correlation between ossification of the stylohyoid ligament and osteophytes of the cervical spine.

OBJECTIVE: To investigate the correlation between ligamentous ossification or osteophytes of the cervical spine and ossification of the styloid process and stylohyoid ligament, and to determine any relation between diffuse idiopathic skeletal hyperostosis (DISH) of the thoracic spine and ossification of the styloid process and stylohyoid ligament. METHODS: Four patients having cervical spine DISH, an elongated styloid process and/or variable patterns of stylohyoid ligament ossification, and clinical findings compatible with Eagle's syndrome are described. Cervical computed tomography scans of 100 patients who also had lateral radiographs of the thoracic spine were reviewed. Point biserial and Spearman rank correlation analysis, McNemar test, chi-squared test, and Fisher's exact test were used to determine correlation between elongation of the styloid process and/or ossification of the stylohyoid ligament and (1) ligamentous ossification or osteophytes of the cervical spine (the characteristic spinal manifestation of DISH), and/or (2) DISH of the thoracic spine. RESULTS: (1) Elongation of the styloid process and variable patterns of ossification of the proximal, middle, and distal parts of the stylohyoid ligament, and (2) enlargement of this ligament were significantly correlated with transverse and anteroposterior dimensions of ligamentous ossification or osteophytes of the cervical spine at various levels. The prevalence of such abnormalities of this process and ligament was not significantly different between the patients with and without thoracic spine DISH. CONCLUSION: Variable types of styloid process-stylohyoid ligament complex abnormalities have significant correlation with ligamentous ossification and osteophytes of the cervical spine.