Osteomyelitis originating in and around bone infarcts: giant sequestrum phenomena

OBJECTIVE

We describe four cases of osteomyelitis that occurred in and around foci of preexisting osteonecrosis in the medullary cavity. Although sequestration is a well-known complication of osteomyelitis, there is little information known about infection occurring in proximity to large regions of already necrotic bone.

CONCLUSION

Osteomyelitis and bone infarction can be seen in the same patient population. Medullary infarcts may function as sequestra, predisposing patients to osteomyelitis and soft-tissue infection.

The influence of flip angle on the magic angle effect

OBJECTIVE

To assess the impact of flip angle with gradient sequences on the "magic angle effect". We characterized the magic angle effect in various gradient echo sequences and compared the signal-to-noise ratios present on these sequences with the signal-to-noise ratios of spin echo sequences.

DESIGN

Ten normal healthy volunteers were positioned such that the flexor hallucis longus tendon remained at approximately at 55 degrees to the main magnetic field (the magic angle). The tendon was imaged by a conventional spin echo T1- and T2-weighted techniques and by a series of gradient techniques. Gradient sequences were altered by both TE and flip angle. Signal-to-noise measurements were obtained at segments of the flexor hallucis longus tendon demonstrating the magic angle effect to quantify the artifact. Signal-to-noise measurements were compared and statistical analysis performed. Similar measurements were taken of the anterior tibialis tendon as an internal control.

RESULTS AND CONCLUSIONS

We demonstrated the magic angle effect on all the gradient sequences. The intensity of the artifact was affected by both the TE and flip angle. Low TE values and a high flip angle demonstrated the greatest magic angle effect. At TE values less than 30 ms, a high flip angle will markedly increase the magic angle effect.

Filariasis of the ankle: magnetic resonance imaging

Filariasis is a world health problem that is frequently seen in tropical and subtropical countries. In endemic areas, the clinical spectrum of extremity swelling, lymphangitis, or elephantiasis is usually recognized as filariasis. In the United States, diagnosis of the disease may be more difficult because of lack of familiarity with this infection. We present a case of filaremic arthropathy of the ankle joint and the magnetic resonance imaging (MRI) findings of this disease. It is the first reported case of MRI findings in a human patient. MRI has been done on animal models with filariasis, and the findings are similar.

Avascular necrosis of bone in human immunodeficiency virus infected patients

The objective of this article was to delineate the causes of avascular necrosis (AVN) in patients with human immunodeficiency virus (HIV). HIV-infected patients with pain in large joints were prospectively screened. Patients had radiographs and magnetic resonance imaging of their affected joints. Serum lipids, anticardiolipin antibody levels (IgG, IgM), and hemoglobin electrophoresis were performed on all patients who had radiographic studies. Medical records were screened for factors known to predispose for AVN. Eight patients completed the protocol, and five patients had AVN in seven joints. No common laboratory abnormality was identified in the patients with AVN. All of the patients with AVN had a history of steroid use; four of five patients having taken steroids for HIV-related diseases. The cause of AVN does not appear to be directly related to the disease, but to steroid treatment for manifestations of the disease.

Computed tomographic and magnetic resonance imaging of chronic odontoid fractures

STUDY DESIGN

The analysis of the imaging characteristics found in chronic odontoid fractures.

OBJECTIVES

To determine the efficacy of computed tomography and magnetic resonance imaging in diagnosing a chronic odontoid fracture.

SUMMARY OF BACKGROUND DATA

Radiographic examination of the cervical spine is intrinsic to the evaluation of all patients with blunt trauma. Injury to the craniocervical junction constitutes 19-25% of all cervical spine fractures. At the authors' trauma center computed tomography is routinely used instead of the open-mouth odontoid radiograph to facilitate cervical spine evaluation. This practice has increased the detection of fractures that are unrecognized in plain radiography, and has, at the same time, raised questions about the age and significance of these fractures.

METHODS

Radiography, computed tomography, and magnetic resonance imaging studies were performed on three patients who came to the emergency department with odontoid fractures. Two patients had a history of severe trauma, and one had a history inconsistent with an acute odontoid fracture. One patient also had a technetium Tc 99m methylene dihydroxyphosphonate bone scan. The studies were obtained to determine the age of the fractures.

RESULTS

All three patients were determined to have chronic odontoid fractures. This diagnosis was facilitated by the use of computed tomographic and magnetic resonance imaging. Computed tomography showed increased sclerosis in the proximal fracture fragment in all cases and well-corticated fracture edges in one patient. Magnetic resonance images showed normal bone marrow or bone sclerosis in the odontoid process. Soft tissue edema was absent. A bone scan was not useful in resolving this issue.

CONCLUSION

Computed tomography and magnetic resonance imaging can be useful in determining the chronicity of an odontoid fracture.

Internal derangement of the knee after ipsilateral femoral shaft fracture: MR imaging findings

OBJECTIVE

This study uses magnetic resonance (MR) imaging to delineate the types and frequencies of injuries seen in the knee after ipsilateral femoral shaft fracture. We also compare the results of the orthopedic knee examination with the MR findings.

DESIGN AND PATIENTS

MR imaging of the ipsilateral knee was performed on 34 patients with closed femoral shaft fractures. Indications for knee MR imaging included knee pain at the time of fracture, soft tissue swelling or an effusion of the knee, or a positive knee examination under anesthesia. The patients had a mean age of 27 years and all were stabilized with intramedullary nails. Imaging was performed a mean time of 2.5 days after surgery. All patients had knee examinations done under anesthesia, and the MR results were compiled and compared with the clinical examinations.

RESULTS

Ninety-seven percent of patients demonstrated knee effusions. Twenty-seven percent of patients demonstrated meniscal tears, with the posterior horn of the medial meniscus most frequently torn. The medial collateral ligament was the most frequent site of ligamentous injury (38%) followed by the posterior cruciate ligament (21%). Fifty percent of patients had injuries of the extensor mechanism. Bone bruises were noted in 32% of patients. Articular cartilage injuries were confined to the patella in four cases. One occult tibial plateau fracture and one meniscocapsular separation were seen.

CONCLUSIONS

There is a common incidence of both ligamentous and meniscal injury to the knee after ipsilateral femoral shaft fracture. MR imaging can be useful in assessing the extent of injury, and may reveal findings unsuspected after clinical examination of the knee.

Osteogenesis imperfecta with joint contractures: bruck syndrome

We describe an Egyptian boy with osteogenesis imperfecta who was born with thumb contractures and bilateral antecubital pterygia. He was seen at 16 months of age with femur and tibial fractures, thoracic vertebral compression fractures, scoliosis and Wormian bones. The findings are consistent with a diagnosis of Bruck syndrome.

Synovial sarcoma: frequency of nonaggressive MR characteristics

PURPOSE

Our objective was to examine the MR characteristics of synovial sarcoma and determine the frequency of a nonaggressive imaging appearance.

METHOD

Fifteen patients with histologically confirmed cases of synovial sarcoma and prior MR examinations were seen. Retrospective analysis of imaging features included assessment of size, margins, homogeneity, internal architecture, T1- and T2-weighted signal intensities, and bone invasion.

RESULTS

Five of 15 patients (33%) had well circumscribed, homogeneous lesions with a mean length of 4.8 cm. The T1-weighted signal intensity was either isointense to muscle or greater in signal intensity than muscle. The T2-weighted images demonstrated signal intensity equal to or greater than fat. The remaining 10 lesions were larger (mean length of 11.3 cm) with mild to complex levels of inhomogeneity and margins that varied from well circumscribed to infiltrating.

CONCLUSION

There are two sets of MR features seen with synovial sarcoma. Small lesions of -5 cm can demonstrate a nonaggressive appearance with well circumscribed margins and homogeneous signal intensity. These tumors could be confused with benign lesions, resulting in inappropriate surgical intervention like excisional biopsies through transverse incisions. This would make future surgery more difficult. Larger lesions tend to be more heterogeneous in signal intensity.

Computed tomography--guided aspiration of a ganglion cyst of the anterior cruciate ligament: a case report

This report describes the case of a ganglion cyst of the anterior cruciate ligament in a 26-year-old man who had long-standing intermittent knee pain with locking. The cyst was successfully aspirated under computed tomography guidance, with complete resolution of symptoms. A literature review is presented along with diagnostic and treatment approaches for this uncommon finding.

Frequency and significance of fractures of the upper cervical spine detected by CT in patients with severe neck trauma

OBJECTIVE

Radiographic evaluation of the upper cervical spine in patients who have suffered severe trauma is often problematic because of the difficulty of obtaining adequate open-mouth views of the odontoid in these critically ill patients. This study was undertaken to determine the frequency and clinical significance of upper cervical spine fractures detected by CT in this patient population.

MATERIALS AND METHODS

The study group consisted of 100 consecutive patients brought to the emergency department after severe trauma who had CT of the craniocervical junction done instead of an open-mouth view. Plain film evaluation consisted of a cross-table lateral view, an anteroposterior view, and, if necessary, a swimmer's view. The radiographic studies were reviewed retrospectively by a musculoskeletal radiologist and a neuroradiologist, respectively. Hospital records were reviewed to ascertain the patients' clinical signs and symptoms on admittance and to determine how identification of the fractures changed the treatment plan.

RESULTS

Eight fractures in seven patients were identified with CT of the craniocervical junction. Three of the fractures were of the occipital condyle, and five were at the C1-C2 level. None of the fractures were seen directly on plain radiographs, although secondary signs of injury such as prevertebral soft-tissue swelling were seen in two of the seven cases.

CONCLUSION

CT of the craniocervical junction revealed an 8% frequency of fractures of the occipital condyle and C1-C2 that were undetected on the cross-table lateral cervical spine radiographs. Fractures occurred in greater numbers than expected, and all surviving patients were stabilized with a halo. This experience shows that CT is an efficient method of evaluating patients in whom the standard open-mouth radiograph of the odontoid cannot be done.

Magnetic resonance imaging of intraosseous lipomas: a radiologic-pathologic correlation

Four patients with intraosseous lipomas were studied with magnetic resonance imaging. The imaging features and histology of each tumor were compared. Magnetic resonance imaging was very helpful in establishing a pathologic diagnosis. If a severe degree of involution was present, then the magnetic resonance findings could be ambiguous, making diagnosis more difficult.

A case report of intracortical hemangioma. A forgotten intracortical lesion

The differential diagnosis for lytic intracortical lesions consists primarily of osteoid osteoma and Brodie's abscess. A third, less-well-known lesion is the intracortical hemangioma. It has an identical appearance to the two aforementioned lesions on bone scan and radiographs. This case report will describe the magnetic resonance imaging appearance of intracortical hemangioma and how it might be differentiated from osteoid osteoma and Brodie's abscess.

Patterns of fracture after air bag deployment

The airbag restraint system has been described as a means of reducing fatalities in frontal crashes. This conclusion is based on crash investigations and statistical extrapolation, but few data exist to document specific fracture patterns and injuries after airbag deployment. Seven cases of driver's side airbag deployment after motor vehicle crashes were studied for extent of injury. Unrestrained (non-seatbelted) drivers demonstrated flexion injuries of the cervical and thoracic spine and direct impaction fractures of the face and sternum. One restrained (lap-shoulder belt) driver demonstrated an extension injury of the upper cervical spine. What may emerge from further study is a decrease in fatalities, but also a pattern of fractures specific to airbag use.

Mechanics of interbody spinal fusion. Analysis of critical bone graft area

Bone graft subsidence is a serious complication of interbody spinal fusion. In this study, 66 mechanical tests were performed on 35 thoracic vertebral bodies to investigate the in situ mechanics of interbody spinal fusion. The relationships among trabecular bone density, bone strength, and size of bone graft area were analyzed. All vertebral bodies were scanned by quantitative computer tomography (QCT) to determine their bone density before mechanical testing. The decorticated trabecular beds of the vertebral bodies, void of all posterior elements, were loaded in a manner similar to that which occurs after surgical interbody fusion. That is, rectangular blocks of polymethylmethacrylate, representing bone grafts, were used to transfer controlled compressive loads to the decorticated vertebral trabecular surface. Both destructive and nondestructive tests were performed. The relationship between QCT bone density and trabecular bone strength was related by a power function, and, on average, the bone density and trabecular bone strength were 0.137 g/cm3 and 3.97 MPa, respectively. Eighty percent of the vertebral bodies with graft covering 25% of the total end plate area or less failed at loads less than 600 N, while 88% of the vertebral bodies with 30% or greater covered were able to carry a load greater than 600 N. The results suggest that the intrinsic behavior of trabecular bone loaded within the vertebral body is little different from the behavior of the whole body, that QCT bone density is indicative of bone strength, and that interbody graft area should be significantly greater than 30% of the total end plate area to provide a margin of safety.(ABSTRACT TRUNCATED AT 250 WORDS)

Bilateral diskoid medial menisci diagnosed by magnetic resonance imaging: a case report

A diskoid medial meniscus is a rare finding occurring in approximately 0.3% of the general population. Bilateral medial diskoid menisci are even less common, with only three other cases appearing in the literature. This may be the first reported case of bilateral medial diskoid menisci diagnosed by magnetic resonance imaging and verified at arthroscopy.

Synovial chondromatosis of the hip. Evaluation with air computed arthrotomography

Four patients with primary synovial chondromatosis of the hip were evaluated with air or double contrast computed arthrotomography. Air computed arthrotomography was an easy and accurate method of diagnosing the disease and delineating its anatomic extent. The use of air as a sole contrast agent allowed noncalcified chondromatous nodules to be identified. It prevented faintly calcified nodules from being obscured by positive contrast, and was a better means of assessing the narrow portions of the hip joint. Accurate diagnosis of this disease and its extent was demonstrated using air computed arthrotomography. This method provided the most complete preoperative data for the orthopaedic surgeon.