Seminars in musculoskeletal radiology
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Semin Musculoskelet Radiol · Jan 2000
ReviewEvaluation of the postoperative spine: reducing hardware artifacts during magnetic resonance imaging.
The magnetic susceptibility artifact created by the hardware that is a mainstay of today's surgical techniques can complicate magnetic resonance (MR) imaging of the postoperative spine. This article reviews the physical principles that underlie production of the magnetic susceptibility artifact, as well as the imaging parameters that can be altered to reduce artifact and improve visualization of the areas of concern. Those imaging parameters that most greatly affect artifact production are the strength of the ambient magnetic field, the type of sequence chosen, echo time, the strength and orientation of the frequency encoding gradient, the resolution along the frequency encoding axis as determined by field of view (FOV) and the number of pixels in the frequency encoding direction, the orientation of the hardware to the main magnetic field, the section thickness, and the orientation of the imaging plane.
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Three bones and two joints comprise the pectoral girdle. These are the clavicle, scapula, proximal humerus, acromioclavicular joint, and shoulder joint. The pectoral girdle binds the upper extremity to the torso. ⋯ Whereas the former is a painful but self-limiting injury with minimal sequelae, the latter is life threatening. However, the severity of most pectoral girdle injuries lies between these two extremes. Fractures and dislocations are common in this region throughout life, and a clear understanding of the patterns of injury and their radiographic spectrum is essential for all radiologists who deal with trauma.
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Fractures and dislocations of the elbow usually occur secondary to indirect trauma. In the adult, fractures of the distal humerus almost always involve the condyles. Fractures of the radial head and neck may be subtle, and the appearance of secondary signs, such as the elevated fat pads from an elbow joint effusion, may be diagnostically useful. ⋯ Osteochondral injury may be difficult to identify without adjunctive imaging techniques, such as magnetic resonance (MR) imaging. Soft tissue injury at the elbow is also well characterized by MR imaging. Fractures of a single forearm bone may occur in isolation, usually due to a direct blow, but these are usually associated with fracture of displacement of the other bone in that forearm.
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Magnetic resonance (MR) imaging is an excellent technique for evaluating the postoperative spine when the patient has chronic or recurrent symptoms. Potential causes of pain following lumbar surgery include arachnoiditis, stenosis, epidural fibrosis and disc herniations, pseudomeningocele, and infection. The postoperative cervical spine may be complicated by hematoma, canal or foraminal stenosis, disc herniation, and cord abnormality. This article reviews standard imaging protocols, the normal postoperative appearance of the spine, and the characteristic imaging findings for each of the abnormal postoperative conditions.
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Benign cartilage lesions discussed in this article include osteochondroma (solitary, epiphyseal, and multiple), chondroblastoma, periosteal chondroma, and chondromyxoid fibroma. These lesions often demonstrate imaging appearances strongly suggesting the above diagnosis, particularly the "ring and arc" mineralization characteristic of cartilage lesions, which reflects their underlying pathology. This article emphasizes the imaging spectrum of these lesions with a multimodality approach.