Imaging of hip disorders.

Many different imaging modalities are available to assist in the evaluation of hip disease. One must choose the image or series of images that not only provide the most diagnostic and clinical information, but also remain the simplest and most cost effective for the patient. The initial examination should be the conventional radiograph. This will provide, in most instances, the most diagnostic information for arthritic disease, stress and insufficiency fractures, infection, and bone tumors. If the conventional radiograph is normal, or if more information is needed, bone scintigraphy should be done next. Bone scintigraphy will confirm the presence of disease, demonstrate its anatomic location, and give some information as to its physiologic state. Computed tomography does not play an important role in the evaluation of hip disease except in acute fractures involving the acetabulum. MR imaging is the modality of choice for diagnosing and staging osteonecrosis, searching for marrow disease, assessing cartilage abnormality, and evaluating the extent of soft-tissue disease.

Cartilaginous bone tumors.

Cartilaginous tumors can be subdivided into several categories according to the following three criteria: (1) Is the lesion benign or malignant? (2) Is the lesion a pure or impure cartilaginous tumor? (3) Is the epicenter of the lesion intraosseous, juxtacortical, or in the soft tissues? This article focuses on the four most common benign cartilaginous tumors, enchondroma, osteochondroma, chondroblastoma, and chondromyxoid fibroma, and on chondrosarcoma. It reviews the biologic and developmental considerations of each and discusses in depth the basic concepts in the radiologic diagnosis of cartilaginous tumors.

Imaging of soft tissue tumors.

In summary, MR imaging is the preferred modality for the evaluation of a soft tissue mass after plain films have been taken. The radiologic appearance of certain soft tissue tumors or tumorlike processes such as myositis ossificans, benign fatty tumors, intramuscular hemangiomas, pigmented villonodular synovitis, and certain hematomas may be sufficiently unique to allow a strong presumptive radiologic diagnosis. It must be emphasized that MR cannot reliably distinguish between benign and malignant lesions, and when radiologic evaluation is nonspecific, one is ill advised to suggest a lesion is benign or malignant solely on the basis of its MR appearance. CT may be useful in specific instances for the identification of subtle soft tissue mineralization in those patients in whom lesions are not adequately evaluated by radiographs. Ultrasonography may be useful in the assessing of recurrent disease as well as in establishing tumor vascularity.

The use of gadolinium in the MR evaluation of musculoskeletal tumors.

Magnetic resonance (MR) imaging has emerged as the preferred modality for the imaging evaluation of musculoskeletal tumors. Although there is general agreement on the value of MR in diagnosis and staging, the use of intravenous contrast in the evaluation of musculoskeletal lesions remains controversial. The purpose of this review is to highlight these controversies, to put them in perspective, and to suggest recommendations for the use of gadopentetate dimeglumine. The following specific areas will be addressed: (a) evaluation of soft-tissue tumors, (b) diagnosis of low-grade chondrosarcoma and the use of contrast material in identification of intraosseous metastases, (c) monitoring response to chemotherapy, (d) evaluation for local recurrence after surgery and/or radiation therapy, and (e) selection of biopsy site.

Giant-cell tumor of the tibia in a child presenting as an expansile metaphyseal lesion with fluid-fluid levels on MR.

Approximately two percent of giant-cell tumors (GCT) occur in the skeletally immature. The patient presented is four years old with a cystic giant-cell tumor of the tibial metaphysis. Fluid-fluid levels are demonstrated on CT and MR and likely represent the underlying pathophysiology.

Atlantoaxial subluxation in Reiter's syndrome. A report of three cases and review of the literature.

Three patients with the unusual manifestation of atlantoaxial subluxation in Reiter's syndrome are studied. Each patient had mild symptoms referable to the cervical spine and radiologic evidence of erosive disease elsewhere in the skeleton. One patient had an 11-year history of Reiter's syndrome when the atlantoaxial subluxation was detected. The other two had atlantoaxial subluxation detected within 1 year of initial presentation, at variance with three other such patients that were reported previously, in whom there was a 6- to 10-year interval from initial presentation until radiographic documentation of atlantoaxial subluxation. Cervical spine radiographs, including flexion and extension views, are recommended for all patients with Reiter's syndrome and cervical spine symptoms.

Magnetic resonance imaging of the brain stem in adolescent idiopathic scoliosis.

The cause of adolescent idiopathic scoliosis remains an enigma. Several studies have demonstrated abnormalities of posture, proprioception, and equilibrium control in patients with adolescent idiopathic scoliosis. These functions are integrated by structures in and around the brain stem. Twenty-seven patients with adolescent idiopathic scoliosis were studied with magnetic resonance imaging to delineate the anatomy of the brain stem in such patients. Imaging was conducted from the hypothalamus to the spinal cord at C3 in 26 patients; the remaining patient underwent an incomplete study because of a claustrophobic reaction. The study group consisted of 25 females and 2 males with an average age of 16 + 5 years. There were 19 right thoracic curves, 5 thoracolumbar curves, and 3 left lumbar curves. The mean primary curve size was 27 degrees at the most recent clinical evaluation. Seven patients were treated with observation, 14 with bracing, and 6 with surgery. The magnetic resonance imaging studies were read independently by three attending radiologists in a randomized, blinded fashion along with the magnetic resonance imaging studies of 11 controls. Asymmetry in the ventral pons or medulla in the area of the corticospinal tracts was noted in seven study patients and one control; one study patient had an enlarged cisterna magna and one an inconclusive (incomplete) study. These findings may support previous studies that have suggested a central nervous system abnormality as a cause of adolescent idiopathic scoliosis.

Percutaneous transpedicular biopsy of vertebral body lesions.

STUDY DESIGN: This prospective study evaluates the use of transpedicular biopsy in obtaining diagnostic tissue from vertebral body lesions. OBJECTIVE: To report the authors' experience of all (N = 32) percutaneous transpedicular biopsies performed between 1990-1994. SUMMARY OF BACKGROUND DATA: Previous articles have discussed the value of open biopsy of the vertebral body using a Craig needle. A large series of closed percutaneous transpedicular biopsies have not been reported. METHODS: The authors evaluated 32 patients (26 outpatients, six inpatients) who underwent transpedicular biopsy for T1-L4 lesions of the vertebral bodies. None of the tumors had an extraosseous component. Biopsy specimens were obtained from 25 lesions using C-arm fluoroscopy; seven were guided by computed tomography. All biopsies were performed with a 14- to 17-gauge bone biopsy needle. RESULTS: The needle passed through the pedicle into the site of disease in all patients, as confirmed by C-arm fluoroscopy or computed tomography. There were 22 malignancies; four isolated compression fractures, two at T6, one at T7, one at T8; four cases of infection or inflammation; and one case each of Paget's disease and myelofibrosis. Two patients required a second biopsy because the tissue sample was suspicious for lymphoma but not diagnostic. All 26 outpatients were discharged after a 2-hour observation period. There were no complications. CONCLUSION: Transpedicular biopsy of deep vertebral body lesions using a bone biopsy needle under computed tomography or fluoroscopy guidance can be performed safely and efficaciously as an outpatient procedure.

MR imaging of musculoskeletal tumors of the hand and wrist.

Musculoskeletal tumors of the hand and wrist are relatively uncommon. Yet, despite their overall rarity, certain bone and soft-tissue lesions have a predilection for this location. This article reviews the common musculoskeletal tumors of the hand and wrist. It is not intended as a comprehensive review but as an overview, emphasizing the use of MR imaging in the evaluation of these lesions and highlighting those diagnoses that may be suggested by MR imaging.

MR imaging of soft-tissue masses. Mass-like lesions that simulate neoplasms.

The MR appearance of soft-tissue masses that simulate neoplasms has been described. In some cases, radiographs may demonstrate characteristic findings in association with MR imaging that may be diagnostic, such as an ossific rim seen in myositis ossificans, periosteal reaction seen in fibro-osseous pseudotumor, and retained foreign bodies present in a foreign body reaction or abscess. In other cases, the characteristic lesion location, age of the patient, and clinical presentation may be suggestive of the diagnosis, as in elastofibroma and nodular fasciitis.

The use of gadolinium in the MR evaluation of soft tissue tumors.

MRI has emerged as the preferred modality for the imaging evaluation of musculoskeletal tumors. Although there is general agreement on the value of MR in detection, diagnosis and staging, the use of intravenous contrast in the evaluation of soft-tissue tumors and tumor-like masses remains controversial. The purpose of this review is to highlight these controversies, to put them in perspective, and to make recommendations for the use of gadolinium-enhanced imaging. The following specific areas will be addressed: (1) general considerations in the evaluation of soft tissue tumors, (2) added specificity in diagnosis, (3) response to chemotherapy, (4) evaluation for local recurrence after surgery and/or radiation therapy, and (5) selection of biopsy site.

Magnetic resonance imaging of musculoskeletal tumors.

In summary, MRI is the preferred modality for the evaluation of a soft-tissue mass following radiography. The radiologic appearance of certain soft-tissue tumors or tumor-like processes such as benign fatty tumors, intramuscular hemangiomas, pigmented villonodular synovitis, and certain hematomas may be sufficiently unique to allow a strong presumptive radiologic diagnosis. It must be emphasized that MRI cannot reliably distinguish between benign and malignant lesions and, when radiologic evaluation is nonspecific, one is ill advised to suggest a lesion is benign or malignant solely on its MR appearance. The role of MRI in the evaluation of bone tumors is predominantly one of staging. MRI is superb to evaluate the extent of intraosseous and soft-tissue involvement as well as the relationship of the lesion to the neurovascular bundle. Unfortunately, MRI remains nonspecific and is unable to predict lesion histology. Finally, the value of Gd-DTPA enhanced imaging is still to be determined.

Benign soft-tissue tumors in a large referral population: distribution of specific diagnoses by age, sex, and location.

OBJECTIVE: The purpose of this study was to determine the specific diagnoses, relative prevalence, and the age, sex, and skeletal distribution of benign soft-tissue tumors and to ascertain the relative frequency of these tumors in specific anatomic locations and age groups among a population of patients in a large pathologic consultation service. MATERIALS AND METHODS: The computer diagnoses of 39,179 lesions occurring in 38,484 patients seen by the Armed Forces Institute of Pathology soft-tissue pathologists during the 10-year period starting January 1, 1980, and ending December 31, 1989, were retrospectively reviewed. All lesions were placed in one of 121 major categories in accordance with the classification system used by the World Health Organization and coded to one of 32 anatomic locations such as hand, wrist, and forearm. Age and sex of the patients were also recorded. For purposes of analysis, all lesions were placed in one of 10 categories: hand and wrist, upper extremity, proximal limb girdle (axilla and shoulder), foot and ankle, lower extremity, hip and buttocks region, head and neck, trunk, retroperitoneum, and other lesions. The study group included 31,047 mesenchymal lesions, of which 18,677 were benign. RESULTS: Approximately two thirds of soft-tissue tumors were classified into seven diagnostic categories: lipoma and lipoma variants (16%), fibrous histiocytoma (13%), nodular fascilitis (11%), hemangioma (8%), fibromatosis (7%), neurofibroma (5%), and schwannoma (5%). Approximately 80% of all benign tumors were placed in seven diagnostic categories for each age and location. In the retroperitoneum, for example, approximately half the benign lesions in the 16- to 25-year old group were fibromatosis (20%), schwannoma (14%), and neurofibroma (13%). For the same location in children 5 years old or younger, almost two thirds of the benign tumors were lipoblastoma (37%) or lymphangioma (26%). CONCLUSION: Despite the large number of pathologic possibilities, most benign soft-tissue tumors are classified into a small number of specific diagnostic categories. These may be further defined when the location of the lesion and the age of the patient are considered. Knowledge of tumor prevalence will assist the radiologist in establishing a suitably ordered differential diagnosis when a soft-tissue tumor has a nonspecific radiologic appearance.

Malignant soft-tissue tumors in a large referral population: distribution of diagnoses by age, sex, and location.

OBJECTIVE: The purpose of this study was to determine the relative prevalence, age at presentation, sex distribution, and skeletal distribution of malignant soft-tissue tumors and to ascertain the relative frequency of these tumors in specific anatomic locations and age groups among a population of patients in a large pathologic consultation service. MATERIALS AND METHODS: The computer diagnoses of 39,179 lesions occurring in 38,484 patients seen by soft-tissue pathologists at the Armed Forces Institute of Pathology during the 10-year period from January 1, 1980, to December 31, 1989, were retrospectively reviewed. All lesions were placed in one of 121 major categories in accordance with the classification system used by the World Health Organization and coded to one of 32 anatomic locations, such as hand, wrist, forearm, and so forth. Age and sex also were recorded. For purposes of analysis, all lesions were placed in one of 10 categories: hand and wrist, upper extremity, proximal limb girdle (axilla and shoulder), foot and ankle, lower extremity, hip and buttocks region, head and neck, trunk, retroperitoneum, and other lesions. The study group included 31,047 mesenchymal lesions, of which 12,370 were malignant. RESULTS: More than 80% of malignant tumors were classified into eight diagnostic categories: malignant fibrous histiocytoma (24%), liposarcoma (14%), leiomyosarcoma (8%), malignant schwannoma (6%), dermatofibrosarcoma protuberans (6%), synovial sarcoma (5%), fibrosarcoma (5%), and sarcoma, not classified further (12%). Approximately 79% of all malignant tumors were classified into five diagnoses for each age and location. With the distal upper extremity (hand and wrist) as an example, 50% of malignant lesions in the 16-25-year-old group were classified as epithelioid sarcoma (29%), malignant fibrous histiocytoma (13%), and synovial sarcoma (8%). For the same location but for children 5 years old or younger, almost 50% of malignant tumors were classified as infantile fibrosarcoma. CONCLUSION: Despite the multitude of pathologic possibilities, most malignant soft-tissue tumors are classified into a small number of diagnoses. These may be further defined when the location of the lesion and the age of the patient are considered. Knowledge of tumor prevalence will assist radiologists in establishing a suitably ordered differential diagnosis when a soft-tissue tumor has a nonspecific radiologic appearance.

Primary musculoskeletal tumors of fibrous origin.

Tumors of fibrous origin include fibrous dysplasia (FD), fibroxanthoma (nonossifying fibroma), cortical desmoid, desmoplastic fibroma, fibrosarcoma, and malignant fibrous histiocytosis (MFH). Benign fibrous lesions (FD, fibroxanthoma, and cortical desmoid) frequently demonstrate pathognomonic radiologic characteristics obviating the need for biopsy. Indeed, biopsy of these lesions can occasionally lead to confusion with more aggressive lesions. Desmoplastic fibroma and the malignant fibrous lesions (fibrosarcoma and MFH) often reveal nonspecific imaging features of a solitary nonmineralized lesion with aggressive characteristics. However, imaging is important as with other neoplasms in delineating the extent of involvement for staging purposes. This article reviews the spectrum of clinical characteristics, pathology, imaging appearances, treatment, and prognosis of lesions of fibrous origin in bone.

Lesions of unknown histogenesis: Langerhans cell histiocytosis and Ewing sarcoma.

Langerhans cell histiocytosis (LCH) and Ewing sarcoma represent lesions of unknown histogenesis. Both lesions typically affect children and adolescents. Imaging features frequently suggest the diagnosis, and both lesions may demonstrate aggressive characteristics. LCH shows a broader spectrum of imaging findings, depending on lesion activity and location, which are reviewed in this article. Ewing sarcoma typically reveals both osseous and soft tissue involvement, although direct continuity of the components is often not apparent. Knowledge of the spectrum of clinical and radiologic features facilitates early diagnosis and can be used to evaluate the effects of therapy.

From the archives of the AFIP. Extraskeletal osseous and cartilaginous tumors of the extremities.

Extraskeletal osseous and cartilaginous tumors and tumorlike conditions of the extremities can often be differentiated radiologically; for those that cannot, knowledge of the spectrum of lesions will allow a suitably ordered differential diagnosis. Of the osseous lesions--myositis ossificans, fibro-osseous pseudotumor, fibrodysplasia ossificans progressiva, soft-tissue osteoma, and extraskeletal osteosarcoma--all but myositis ossificans are relatively rare. Myositis ossificans has a distinct mineralization pattern that can be observed radiologically as a peripheral rim of lamellar bone. Fibro-osseous pseudotumor typically occurs in the digits of the hand and lacks the well-defined zoning pattern of myositis ossificans. The cartilaginous entities include the true tumors, soft-tissue chondroma and extraskeletal chondrosarcoma, and the tumorlike process, synovial osteochondromatosis. The tumors are relatively rare; synovial osteochondromatosis commonly affects middle-aged men, especially in the knee, and is associated with osteoarthritis. The differential diagnosis for these extraskeletal osseous and cartilaginous lesions includes soft-tissue sarcoma, benign mesenchymoma, malignant mesenchymoma (rare), calcified tophi in gout, melorheostosis (rare), pilomatricoma (rare), and tumoral calcinosis (rare).

Aneurysmal bone cyst: concept, controversy, clinical presentation, and imaging.

The aneurysmal bone cyst is the result of a specific pathophysiologic change, which is probably the result of trauma or a tumor-induced anomalous vascular process. In approximately one third of cases, the preexisting lesion can be clearly identified. The most common of these is the giant cell tumor, which accounts for 19-39% of cases in which the preceding lesion is found. Other common precursor lesions include osteoblastoma, angioma, and chondroblastoma. Less common lesions include fibrous dysplasia, fibroxanthoma (nonossifying fibroma), chondromyxoid fibroma, solitary bone cyst, fibrous histiocytoma, eosinophilic granuloma, and even osteosarcoma. Interestingly, some of the controversy surrounding this lesion may be the result of a change in how the lesion was defined by Lichtenstein in 1953, when intramedullary lesions were added to the previously described juxtacortical (superficial) lesions. Members of the AFIP have suggested that many of the intramedullary lesions in which no previous lesion can be identified may represent giant cell tumors of bone. Their similarity to proved giant cell tumors in skeletally immature patients can be striking and seems more than coincidental. Appropriate treatment of an aneurysmal bone cyst requires the realization that it results from a specific pathophysiologic process, and identification of the preexisting lesion, if possible, is essential. Clearly an osteosarcoma with superimposed secondary aneurysmal bone cyst change must be treated as an osteosarcoma, and giant cell tumor with secondary features of aneurysmal bone cyst would be expected to be more likely to recur locally. The vast majority (approximately 80%) of patients presenting with aneurysmal bone cystlike findings are less than 20 years old. More than half of all such lesions occur in long bones, with approximately 12-30% of cases occurring in the spine. The pelvis accounts for about half of all flat bone lesions. Most patients present with pain and/or swelling, with symptoms usually present for less than 6 months. The imaging appearance of aneurysmal bone cyst reflects the underlying pathophysiologic change. Radiographs show an eccentric, lytic lesion with an expanded, remodeled "blown-out" or "ballooned" bony contour of the host bone, frequently with a delicate trabeculated appearance. Radiographs may rarely show flocculent densities within the lesion, which may mimic chondroid matrix. CT scanning will define the lesion and is especially valuable for those lesions located in areas in which the bony anatomy is complex, and which are not adequately evaluated by plain films. Fluid-fluid levels are common and may be seen on CT scans and MR images.(ABSTRACT TRUNCATED AT 250 WORDS)