MR imaging of glenohumeral instability

Familiarity with normal anatomy and pathologic features of the capsulolabral complex as well as high resolution imaging are important factors in achieving a consistently high accuracy rate in diagnosis of glenohumeral instability by conventional MR imaging. In this article, the pathophysiology of glenohumeral instability and the various MR imaging findings are discussed and illustrated.

MR imaging of the menisci. Fundamentals of anatomy and pathology

This article discusses the anatomy of the menisci and various signal abnormalities. Morphologic changes indicative of degenerative disease, degenerative tear, intra- and para-meniscal cysts, and traumatic tear are also covered.

Magnetic resonance imaging of glenohumeral instability

Familiarity with normal anatomy and pathologic features of the capsulolabral complex as well as high resolution imaging are important factors in achieving a consistently high accuracy rate in diagnosis of glenohumeral instabilities by conventional MR imaging. The various types of glenoid labrum lesions and features that are most often associated with glenohumeral instability are defined.

Rotator cuff lesions: signal patterns at MR imaging

The signal intensity patterns of rotator cuff lesions at magnetic resonance (MR) imaging were evaluated in 80 patients who had surgical correlation and in 13 asymptomatic individuals (14 shoulders). Six cadaver shoulders were examined with MR, and histologic correlation was obtained in four. All studies were performed at 1.5 T with a flexible circular surface coil. The accuracy of MR imaging in detection of full-thickness cuff tears (31 patients) was 0.95 and of partial thickness tears (16 patients), 0.84. The most common and accurate pattern for full-thickness cuff tears (22 of 31 tears) was a region of intense signal seen on T2-weighted images. Less often the torn region consisted of an extremely degenerated and attenuated tendon with moderate signal intensity or was obscured by low-signal-intensity scar. The intense signal pattern on T2-weighted images was also accurate, although a less common finding (seven of 16 cases), in the diagnosis of partial tears. Tendinitis was recognized as focal or diffuse regions of increased signal intensity or a nonhomogeneous pattern of increased signal often associated with tendinous enlargement. In some patients, manifestations of subacromial-subdeltoid bursitis was present. Tendon degeneration was also manifested as regions of increased signal intensity. Some similarity and overlap of signal patterns of partial interstitial tears, tendinitis, and tendon degeneration are observed.

Clinical applications of magnetic resonance imaging of the spine

Images

Computed tomography (CT) arthrography of shoulder instabilities in athletes

Sixty professional and recreational athletes underwent CT arthrography of the shoulder for evaluation of suspected shoulder joint derangement. These athletes, 46 males and 14 females ranging in age from 15 to 60 years (mean, 32 years), all had persistent pain that interfered with their sports activity and was resistant to conservative treatment. Seventeen patients had shoulder instability based on clinical manifestations and CT arthrographic findings. An additional five patients, also based on clinical manifestations and CT arthrographic findings, were considered to have an unobtrusive degree of anterior joint laxity. Patients with anterior instability (20 cases) all had an anteroinferior tear or detachment of the glenoid labrum, as well as some violation of the insertion of the joint capsule onto the scapula. Those with posterior instability (two cases) had a combination of labral and capsular tears. Two other major patterns of labral tears, both unaffiliated with shoulder instability, were identified. These included total or partial detachment of superior segments of the labrum, and anterior labral tears at the midglenoid level. Moreover, various degrees of labral attenuation (or, less often, enlargement), osteophyte formation, and alterations in articular cartilage were observed. Surgical correlation was obtained in 25 patients, with 95% accuracy of CT arthrographic findings. CT arthrography is a minimally invasive and highly accurate technique for investigation of glenohumeral derangement. Specifically, the extent of pathologic changes associated with instability can be determined and differentiated from other intraarticular causes of incapacity, such as labral tears caused by throwing, or degenerative changes.

Radiation induced fractures of sacrum: CT diagnosis

Sacral insufficiency fracture due to bone atrophy may develop as a complication of irradiation of pelvic malignancies. Pain is the presenting symptom and the clinical diagnoses most often considered are recurrence of the original malignancy and metastatic disease. Computed tomography provides the most specific information helpful for the detection of these fractures and for exclusion of recurrent malignancy.

The role of computed tomography in evaluation of skeletal metastases

Computed tomography was performed in 100 patients for additional evaluation of suspected skeletal metastases following radionuclide bone scanning in 86 patients and conventional radiography in all. A retrospective review of these cases revealed that the majority (78%) involved the spine and pelvis. Computed tomography contributed to the diagnosis of a malignancy by revealing a definite destructive lesion of bone in 27 patients who had an abnormal radionuclide bone scan, a normal or inconclusive radiograph, or both. It excluded a malignant lesion in 19 patients. In 38 patients, computed tomography provided additional information that contributed to such aspects of patient care as obtaining tissue diagnosis, determining the extent of lesions, and evaluating the response to treatment. False diagnoses were made in two patients. Detection by computed tomography of a skeletal lesion and histologic documentation, frequently by computed tomography-guided percutaneous needle aspiration biopsy, greatly curtailed an otherwise extensive search for the primary site. Furthermore, this information altered the treatment plan by obviating the need for radical resection or biopsy of the primary tumor and by directing the choice of an appropriate chemotherapeutic regimen.

Lumbar spine after surgery: examination with intravenous contrast-enhanced CT

Computed tomography (CT) of the lumbar spine without and with intravenous administration of contrast medium was performed in 143 consecutive patients who had previously had spine surgery for disk herniation and had persistent or recurrent symptoms. Fifty-two patients underwent surgical reexploration. It was possible to make the diagnosis of normal postoperative status, disk herniation, or scarring in 31 (60%) of the 52 patients with the use of CT scans without intravenous contrast medium. CT with intravenous contrast enhancement was useful in 12 of the remaining patients (23%). Enhancement of the margins of a herniated disk occurred in 37 (71%) of the patients. There was near-homogeneous enhancement of postoperative scarring in 34 (65%) patients. Intravenous contrast medium was particularly helpful when disk herniation and scarring were both present, by delineating the margins of a herniated disk and enhancing the entire substance of the scar. In symptomatic postoperative patients, CT of the lumbar spine without intravenous contrast medium should be performed initially. If a definitive diagnosis is not established, CT with intravenous contrast enhancement should be considered.

Athlete shoulder injuries: CT arthrographic findings

Forty-three professional and amateur athletes with persistent shoulder pain that interfered with their sports activities were evaluated by computed tomographic (CT) arthrography. In 19 patients, glenohumeral instability (14 anterior, two posterior, three multidirectional) was diagnosed with CT arthrography based on the simultaneous presence of labral and capsular lesions. The findings were crucial in establishing the diagnosis of instability in six patients in whom the condition was not suggested or could not be confirmed clinically. Another significant injury consisted of labral lesions not associated with glenohumeral instability. These tears often involved the anterior and parasuperior segments of this structure. Other, less frequently detected lesions included segmental labral enlargement and several labra with abnormal orientation (everted labrum). Early onset of degenerative disease was present in many athletes, especially those with a long history of sports activity. CT arthrographic findings were correlated with arthroscopic or surgical results in 19 patients.

Spongious bone density determination for staging and follow-up of patients with prostatic cancer

Quantitative computerized tomography (QCT) of vertebral bodies could reveal metastatic spread of prostatic cancer before such lesions are seen with standard examinations. Focal increase in the density of the spongious bone in face of normal bone scan and serum acid phosphatase is suggestive of metastasis, but certitude is gained only if further increase in density or structural bone changes are demonstrated on follow-up studies. QCT also may provide an objective measurement of tumor response to therapy.

Rate of spinal trabecular bone loss in normal perimenopausal women: CT measurement

Age-related bone loss in women may begin at any time following attainment of peak skeletal maturity bone mass. The rate of bone loss may accelerate near the time of menopause and continue for several years thereafter. Women with low baseline bone mass and women who are fast bone losers are potentially at risk for early spinal osteoporosis. In a prospective longitudinal study, spinal trabecular bone mineral content (BMC) of 83 healthy women, 47-53 years old, was measured with use of computed tomography (CT) at 0, 12, 24, and 36 months. Fifty-four of these same women had a fifth measurement at 48 months. In 51 women the rate of bone loss was less than or equal to 2% per year (average 1.96%; normal bone losers); in 32, it was more than 2% per year (average 5.61%; fast bone losers). CT studies can identify women with low spinal trabecular BMC and/or fast bone loss--women likely to be at increased risk for early spinal osteoporosis. This information may be useful in selection of candidates for vigorous preventive measures, including estrogen replacement.

Trabecular mineral content of the spine in women with hip fracture: CT measurement

The trabecular bone mineral content (BMC) of the spine was measured by computed tomography in 185 women aged 47-84 years with vertebral fracture (n = 74), hip fracture (n = 83), and both vertebral and hip fracture (n = 28). Eighty-seven percent of vertebral-fracture patients, 38% of hip-fracture patients, and 82% of vertebral- and hip-fracture patients had spinal BMC values below the fifth percentile for healthy premenopausal women and values 64%, 9%, and 68% below the fifth percentile for age-matched control subjects. No significant loss of spinal trabecular bone was seen in patients with hip fracture. If it is assumed that the rate of trabecular bone loss is the same in the spine and femoral neck, then hip fracture (unlike osteoporotic vertebral fracture) is not associated with disproportionate loss of trabecular bone. Hip fracture occurs secondary to weakening of bone and increased incidence of falls. Bone weakening may be due to disproportionate loss of trabecular or cortical bone, proportionate loss of both, or other as yet undetermined qualitative changes in bone.

CT arthrography of capsular structures of the shoulder

The capsular mechanism of the shoulder joint consists of the joint capsule, which is strengthened by the glenohumeral ligaments and the rotator cuff, the glenoid labrum, and a variable number of synovial recesses. Although the fibrous capsule is a lax structure, the normal function of the capsular mechanism makes it an effective barrier against anterior dislocation, particularly in external rotation. There has been a tendency in the past to overestimate the role of the glenoid labrum in stability of the shoulder joint. In patients with instability, the significance of the capsular attachment or its anomalous insertions to the glenoid has not been adequately recognized. Labral tears may develop as secondary lesions due to repeated dislocations and subluxations rather than representing the primary lesion responsible for instability. Operative visualization of capsular defects or detachments is often difficult. Prior knowledge of these lesions can effectively help the choice of an appropriate surgical procedure and reduce operating time. The results of computed tomographic (CT) arthrography of the shoulder joint in 45 patients are reported and the normal and pathologic variations of the joint capsule and particularly the capsular insertions are described. Configuration of the joint recesses and the glenoid labrum are also evaluated. These CT findings were correlated and verified by surgery or arthroscopy in 26 cases.

Computed tomography of spinal chordomas

Computed tomography of 16 spinal chordomas revealed lytic lesions, or lytic and blastic lesions, of 2 or more adjacent vertebrae and a fairly well-delineated soft tissue mass in 16 patients. Intravenous contrast enhancement revealed multiple zones of hypodensity in 5 tumors pathologically proved to contain areas of cystic degeneration. Invasion of the epidural space was noted on computed tomography in 2 vertebral and 7 sacral lesions, and on myelography in 7 vertebral lesions. Computed tomography is ideal for delineation of the soft tissue component of these lesions, detection of sacral lesions at an early stage, planning of surgical excision or irradiation treatment, and detection of recurrence.

Computed tomography of osteoid osteoma

Computed tomography revealed a radiolucent nidus with a surrounding zone of osteosclerosis in 17 patients with osteoid osteoma. Plain films did not reveal any abnormality in 5 patients. Conventional tomography was negative in 3 patients. Computed tomography is the modality of choice for detection of osteoid osteoma when the lesion is deep-seated or when it occurs in complex anatomic regions with curvilinear and overlapping surfaces, such as acetabulum, knee, and spine.

Hepatocellular carcinoma with skeletal metastasis

Three patients with symptoms related to metastases from hepatocellular carcinoma are described. The diagnosis of the primary tumor was made at autopsy in two cases and by biopsy in one. The skeletal lesions had a lytic, expansile, and hypervascular appearance. This hypervascularity may lead to bleeding either spontaneously or following biopsy. Hepatocellular carcinoma should be included in the differential diagnosis of osteolytic, expansile, hypervascular metastases, especially when such lesions are encountered in patients with liver cirrhosis.

Computed tomography of septic joints

Twenty-six patients with suspected or known septic joints who had been studied by computed tomography were retrospectively reviewed. Eighteen patients (20 joints) proved to have septic arthritis. Computed tomography was advantageous in patients with acute septic arthritis of deep-seated axial joints, such as the hip and sacroiliac, where it demonstrated particular soft tissue swelling as early as 36 hours after the onset of symptoms. In three patients, this finding on computed tomography was helpful in accurately localizing the disease process and facilitating a diagnostic closed needle aspiration biopsy procedure. Four patients had a primary osseous focus of infection in an adjacent epiphyseal region that was documented by computed tomography. Computed tomography was superior to conventional radiology in revealing early articular bone erosion in joints with curved and overlapping articular surfaces in five patients, and resulted in alteration of their treatment. Fat-fluid levels within the suprapatellar bursae were noted in one patient (two joints). Computed tomography is a valuable modality for evaluation of patients with suspected septic arthritis of axial joints, particularly in the acute stage. Furthermore, it is helpful for evaluation of possible periarticular abscess formation and can serve as a guide for a percutaneous drainage procedure. Computed tomography can also be used when articular bone erosion or medullary extension of osteomyelitis is suspected but not fully documented by conventional radiography.

Hematogenous osteomyelitis with fat-fluid level shown by CT

Computed tomography (CT) revealed fat-fluid (pus) levels in two adult patients who had hematogenous osteomyelitis due to gram-negative organisms: in one patient within an intraosseous cavity, and in another patient within the adjacent suprapatellar bursae. Both patients were hospitalized for other chronic illnesses and had confusing clinical manifestations with non-specific radiographic changes. Observation of fluid levels, in addition to bony erosions, correctly suggested the presence of pus, and in one patient prompted a diagnostic intraosseous aspiration. To our knowledge, this CT sign of hematogenous osteomyelitis has not been previously reported.

Computed tomography of calcification and ossification of posterior longitudinal ligament of the spine

Calcification of the posterior longitudinal ligament occurs in about 3% of adults in Japan, and in about 0.7% of hospitalized adults with spinal symptoms in the United States. The condition may be asymptomatic, however, in patients with a stenotic spinal canal or when the calcification is large, it may cause compression of the spinal cord and myelopathy. The radiographic diagnosis is made when a band of calcification is noted in the spinal canal directly posterior to the vertebral bodies. Lateral tomograms of the spine are helpful for detection and measurement of the exact thickness of the calcification. Computed tomography is particularly helpful because it reveals the thickness and the extent of lateral extension of the calcification, as well as the size of the spinal canal and the extent of its narrowing by the calcification. Seventeen patients evaluated by computed tomography are reported.

Fusion of the lateral joints in fixed atlantoaxial dislocation: a computed tomography demonstration

Fixed atlantoaxial dislocation is a well-known phenomenon that may partially account for the discrepancy between the radiographic and neurologic abnormalities seen in rheumatoid arthritis of the craniocervical region. In this care report, "arthritis rigidity" is demonstrated by computed tomography to be due to fusion of the occipitoatlantoaxial complex, following erosion and disruption of these joints by rheumatoid disease.

Fibrobullous disease of the upper lobes: an extraskeletal manifestation of ankylosing spondylitis

Fibrobullous disease of the upper lobes of the lungs is a rare extraskeletal manifestation of ankylosing spondylitis, occurring in 1.3% of patients with ankylosing spondylitis. We present a patient with this disease, and discuss this pulmonary manifestation. Because the radiographic appearance of the chest in this disease resembles that in tuberculosis, many patients are misdiagnosed and treated for tuberculosis despite negative bacteriology. Computed tomography is useful in delineating the extent of pleural thickening, bullous changes, volume loss, parenchymal fibrosis, and bronchiectasis, as well as identifying or excluding an intracavitary pulmonary mycetoma.

Computed tomography in localization of foreign bodies lodged in the extremities

Surgical removal of foreign objects (FO) lodged in the body may be difficult because of uncertain 3-dimensional localization on conventional roentgenograms. Furthermore, low-density FO may not be detectable on roentgenograms. CT was performed in 8 patients with FO lodged in the extremities, and was found helpful because, (1) it detected 4 low-density FO's missed on roentgenograms, and (2) it facilitated surgical removal by displaying the precise 3-dimensional location of these objects.

Computed tomography of tibial plateau fractures

Open reduction with internal fixation of tibial plateau fractures in performed frequently. Factors that must be considered in planning treatment include the patient's age and physical condition, the presence and degree of plateau depression, the presence and degree of separation of split fragments, and the severity of fracture comminution. Twenty patients with tibial plateau fractures were studied by conventional tomography and computed tomography (CT) in order to determine the role and feasibility of CT in management of such patients. CT resulted in less discomfort to the patient and provided optimal visualization of the plateau defect and the split fragments. It proved more accurate than conventional tomography in assessing depressed and split fractures when they involved the anterior or posterior border of the plateau and in demonstrating the extent of fracture comminution. Split fragments with an oblique plane of fracture also were seen better by CT. The degree of fracture depression and separation as measured by the computerized technique was often more accurate than measurements obtained from conventional tomograms. In three patients, treatment was changed on the basis of the CT findings. In three other cases, the classification was altered without a change in treatment.

Computed tomography of thoracic and lumbar spine fractures that have been treated with Harrington instrumentation

Twenty patients with fractures of the thoracic and lumbar spine underwent computed tomography (CT) following Harrington distraction instrumentation and spinal fusion. CT was done to search for a cause of persistent cord or nerve root compression in those patients who failed to improve and completely recover their partial neurologic deficit (14 cases). In 6 patients seen in the late recovery period, CT was performed to evaluate the causes of pain and instability at the fracture site. Even though the image was degraded due to the artifacts generated by the metallic rods, significant information was available in each case. The most common abnormality was the presence of residual bone fragments originating in the burst fracture of a vertebral body displaced posteriorly, into the spinal canal. In patients with complications in the late recovery period, CT found exuberant callus indenting the canal or lack of fusion of the bone grafts placed in the anterolateral aspect of the vertebral bodies. This experience indicates that CT is the modality of choice for spinal canal evaluation in those patients who fail to have an optimal clinical course following fractures of the thoracic and lumbar spine treated with Harrington rods.

Quantitative computed tomography assessment of spinal trabecular bone. II. In osteoporotic women with and without vertebral fractures

Computed tomography was utilized to measure the bone mineral content of the spinal trabecular bone in 96 osteoporotic women. A significant overlapping was found between the values obtained for these patients and the age-matched normal values. Sixty-six percent had bone mineral content values below the fifth percentile for age-matched normals. Eighty-five percent of those with vertebral fractures had bone mineral content values below the fifth percentile for normal premenopausal women (fracture threshold). It is suggested that diagnosis of osteoporosis be made when the spinal bone mineral content value is below the fracture threshold.

Quantitative computed tomography assessment of spinal trabecular bone. I. Age-related regression in normal men and women

Computed tomography, utilized in conjunction with a calibrated phantom containing a set of reference densities (K2HPO4 and water), is capable of determining the mineral content of the trabecular bone of the spine with an accuracy of about 6% of the ash weight of the vertebrae scanned (specimen studies). Other modalities measure a composite of cortical and trabecular bone. Computed tomography is capable of exclusively measuring the mineral content of the trabecular bone of the spine, where the earliest and most pronounced changes of spinal osteoporosis occur. Quantitative computed tomography measurements are useful for a precise and objective assessment of the spinal mineral content and its changes with age, disease, and drugs.

CT of lumbar spine disk herniation: correlation with surgical findings

Computed tomography (CT) of the lumbar spine was performed with selectively positioned 5-mm-thick axial cross sections to examine each disk level from the top of the neural foramen to the pedicle of the next caudad vertebra. One hundred consecutive patients with 116 surgical disk explorations were reviewed. There was agreement between the CT and surgical findings in 89 patients (104 explorations) in determination of presence or absence of a herniated nucleus pulposus (HNP). Discrepancy occurred in 12 instances (11 patients): two because of incorrect interpretations, five in previously operated patients, three in spondylolisthesis, and two in spinal stenosis. There were 97 true-positives, eight false-negatives, seven true-negatives, and four false-positives. If nine previously operated patients are excluded from the study, then CT was accurate in detection of presence or absence of an HNP in 93% of the disk explorations.

Acute traumatic fibular bowing associated with tibial fractures

Acute traumatic fibular bowing associated with angular fracture of the tibia was observed in three young adults. The fibular bowing may have had a negative effect on the healing of the tibial fracture by transmitting tension through the interosseous membrane, thereby preventing proper reduction of the tibial fracture fragments and delaying the union.

CT of osteomyelitis of the spine

Computed tomography (CT) were performed in 17 adults with osteomyelitis of the spine. The dominant features were paravertebral soft-tissue swelling, abscess formation, and bone erosion. In two patients there were no findings indicative of osteomyelitis on conventional radiographs, but CT revealed paravertebral abscesses and bone lysis, helping to establish the diagnosis of osteomyelitis. CT was found helpful in the evaluation of the patients suspected of spinal osteomyelitis, chiefly because of its ability to detect early erosion of spongy vertebral bone, disk involvement, paravertebral soft-tissue swelling or abscess, and extension of the pathology into the spinal canal. Furthermore, CT facilitated closed-needle biopsy, helping to establish the pathologic diagnosis.

Computed tomography of the sacroiliac joints: comparison with complex-motion tomography

Forty-seven patients with sacroiliac joint abnormalities were examined with computed tomography and conventional complex-motion tomography. Twenty-nine patients had spondyloarthritis. Of the 29, complex-motion tomography detected bone erosions in 16 patients, whereas computed tomography revealed erosions in nine. Computed tomography was more sensitive in detection of joint narrowing, joint widening, osteosclerosis, and intraarticular bony ankylosis. In the remaining 13 patients, computed tomography was the modality of choice in detection of paraarticular soft tissue pathology, such as abscess or tumor, and in detection of the lesions involving the sacral canal and neural foramina.

Computerized tomography of pelvic osteomyelitis in patients with spinal cord injuries

Computerized tomography (CT) was performed in 19 patients with spinal cord injury (SCI) who had large pressure sores and in whom other complications were suspected. CT detected the depth, extent, and degree of undermining of the edges of the pressure sores in 19 of 27 lesions. Conventional radiography detected four cases of pelvic osteomyelitis. CT detected eight additional cases of pelvic osteomyelitis, as well as eight clinically unsuspected peripelvic and intrapelvic abscesses. Technetium-99m bone scanning was not very helpful because of localization in chronic proliferative changes of bone and widespread foci of myositis ossificans, as well as in osteomyelitis. Gallium-67 scanning detected only one of six abscesses. It was not very helpful because of confusion of abscess and osteomyelitis with intense soft tissue swelling and cellulitis, which are often associated with pressure sores in patients with chronic SCI. CT was found to be, by far, the modality of choice for detection of pelvic osteomyelitis and abscess in patients with SCI.

Hypertrophic osteoarthropathy in metastatic renal cell carcinoma

Clinical signs of hypertrophic osteoarthropathy developed in a thirty-eight-year-old man with metastatic hypernephroma. Roentgenograms of the extremities detected the characteristic periosteal reaction along the radius, ulna, metacarpals, femur, tibia, and fibula, bilaterally. The pathogenesis of this syndrome is unknown; it appears to be mediated by a pathologic reflex with the vagus nerve as the afferent limb. When seen in patients with renal cell carcinoma, hypertrophic osteoarthropathy may herald the development of intrathoracic metastases.

Computerized tomography of the Cupid's bow contour of the lumbar spine

The inferior endplates of the third, fourth, and fifth lumbar-vertebral bodies frequently have paired parasagittal concavities when viewed in the frontal projection. In the lateral projection, these concavities lie posteriorly and are superimposed. This has been called Cupid's bow contour of the spine. On CT, Cupid's bow is visualized in an axial plane as two rounded relatively well-circumscribed areas of hypodensity rimmed by apparant osteosclerosis in the posterior half of the vertebral bodies. This, on occasion, may resemble metastasis or other pathology of the spine. The CT features, however, once appreciated, are characteristic of this normal variant, helping to distinguish it from other contour deformities of the vertebrae having clinical significance. The CT features are described and the incidence is discussed in 100 patients.

Computerized tomography in diagnosis of pelvic abscess in spinal-cord-injured patients

Twenty-four spinal-cord-injured patients with pressure sores, and suspected of having other complications were studied by CT, gallium scanning, and ultrasonography. CT was found to be by far the modality of choice for evaluation of the extent and depth of the pressure sore, assessment of the thickness of fibrous tissue scar alongside its boundaries and at its base, detection of associated peri-pelvic and intra-pelvic soft tissue abscesses, sinus tracts and osteomyelitis of the pelvic bones.

Computed tomography of traumatic serosanguineous cysts

Two patients developed traumatic peripelvic serosanguineous cysts, following pelvic fracture. A serosanguineous cyst develops when shearing forces cause separation of the skin and subcutaneous fat from the deep fascia and muscle. The space thus created is filled with serious fluid and blood, and clinically presents as soft cystic masses, appearing usually within a day or so, or rarely, after several weeks or months. Most of these lesions resolve spontaneously, or following aspiration; however, some may persist, necessitating surgical resection. Computed tomography is the modality of choice for detection and, in those cysts requiring surgery, it is helpful in revealing the exact size and location of these lesions.

Pathologic fracture in systemic mastocytosis. Radiographic spectrum and review of the literature

Systemic mastocytosis is a multiorgan disease that most commonly affects the skin and skeletal system. Radiographically, the skeletal changes in the majority of patients consist of either a wide-spread mixture of bone lysis and osteosclerosis or generalized osteoporosis. The osteoporotic form is less well known but may lead to severe generalized demineralization and pathologic fractures. Mast cells secrete a number of substances, two of which (heparin and prostaglandins) are believed to have a role in the induction of osteoporosis. Sclerotic lesions are induced by another mast cell by-product, histamine. One hundred seventy-eight cases of bony mastocytosis have been reported in the literature, including the four patients in the present report. Special staining procedures are necessary for identification of mast cells. Diagnosis may be delayed in patients who do not have the skin lesions (urticaria pigmentosa) and in the osteoporotic form of the disease.

Computerized tomography in diagnosis of compression of the common peroneal nerve by ganglion cysts

A 48-yr old man noted gradual onset of pain, and paresthesia on the lateral aspect of his right leg. The findings were suggestive of S1 root compression. CT of spine was normal. Physical examination revealed a small mass overlying the right fibular head. CT revealed this to be a cystic mass. At surgery a ganglion cyst compressing the common peroneal nerve was found. Peripheral nerves may be compressed by ganglia producing a syndrome mimicking central nerve root compression. CT is the modality of choice for detection of these lesions.

Computed tomography of pressure sores

Twenty-three paralyzed patients admitted for treatment of recurrent pressure sores were evaluated by computed tomography, bone scanning, gallium scanning, and sonography. Computed tomography was helpful in detecting associated peripelvic and pelvic abscesses and pelvic osteomyelitis, which were undiagnosed by all other modalities combined in more than half of the patients. Computed tomography was also useful in preoperative planning by revealing the extent of the undermining of the pressure sore, the thickness of the fibrous scar at its base, and the size and status of the adjacent muscles.

The impact of CT in clinical management of pelvic and acetabular fractures

Thirty-eight consecutive patients admitted to the hospital with pelvic and acetabular fractures underwent CT examination. The axial plane of CT is shown to be the most suitable for evaluation of these fractures. The fracture pattern is readily demonstrated, facilitating fracture classification. The degree of fracture fragment displacement and rotation, hip joint stability, and intra-articular osseous fragments can be determined. A number of unsuspected fractures were detected, including five sacral and four anterior acetabular wall fractures; the latter were due to extension of superior ramus fractures. Soft tissue injuries included several hematomas, serosanguinous cysts in one patient, and bladder laceration in one patient. It is concluded that in patients with pelvic fracture CT examination is the method of choice following preliminary radiographic evaluation, if further radiographic investigation is deemed necessary.

Use of CT-guided percutaneous bone biopsy in staging of genitourinary tumors

CT-guided needle aspiration biopsy has been used for staging of genitourinary tumors. The display of structures provided by CT is particularly suited for complex anatomic sites such as spine, pelvis, thorax, permitting selection of the shortest and safest route for the needle, away from the aorta, vena cava, and pleural surface. Another advantage of CT is its ability to detect soft tissue components of the tumors and the presence of central necrosis therefore targetting the biopsy toward the part of the lesion with the greatest diagnostic yield.

Computed tomography of pressure sores, pelvic abscess, and osteomyelitis in patients with spinal cord injury

Nine patients with spinal cord injury (SCI) and large pressure ulcers and other possible complications, were evaluated by computed tomography (CT), conventional radiography, tomography, bone scanning, gallium scanning, and sonography. CT revealed the depth, extent, and relationship of the ulcer-bed to the underlying structures in all 9 patients. CT also positively identified unsuspected intra- and extra-pelvic abscess and pelvic osteomyelitis in 4 patients each. Other modalities identified only 2 of these complications. We believe CT is the modality of choice for evaluation of these complications in SCI patients, because of its superior ability in evaluation of pressure sores and detection of pathologic changes in soft tissue and bone in the pelvic region.

Bilateral acetabular stress fractures in a paraplegic patient

Advances in rehabilitation programs have enabled many paraplegic persons to take part in activities in which the risk of trauma and skeletal injuries is comparable to that in the general population. Stress or spontaneous fractures are known to occur mainly as a result of severe osteoporosis and uncontrollable motion following removal of leg braces. However, stress fractures due to repeated minor trauma or prolonged physical activity have not been previously observed in paraplegic persons. In this report, bilateral acetabular stress fractures are described in a young paraplegic man during the course of ambulation therapy. The pattern of ambulation in these patients, who attempt to walk with crutches while their legs are placed in braces, is one contributing factor to stress fracture. Because of the paucity of physical findings and absence of pain, these fractures may go unrecognized, which can lead to more serious complications.