Percutaneous vertebroplasty for severe osteoporotic vertebral body compression fractures is safe and effective and should not be withheld in this group of patients.

The objective of this review is to present the imaging findings of skeletal tuberculosis in children. The incidence of tuberculosis is increasing and skeletal tuberculosis accounts for 10-20% of all extra-pulmonary cases. The most common manifestations of skeletal tuberculosis in children are spondylitis, arthritis and osteomyelitis. Tuberculous spondylitis involves the intervertebral disc only late in the disease. Subligamentous spread of the infection may lead to multiple levels of vertebral body involvement that may either be continuous or skipped. Extension of the disease into the paravertebral or extra-dural space may occur. Tuberculous arthritis usually occurs as a result of metaphyseal spread to the joint. Tuberculous osteomyelitis may appear as cystic, well-defined lesions, infiltrative lesions or spina ventosa. The latter is a term used to describe a form of tuberculous osteomyelitis where underlying bone destruction, overlying periosteal reaction and fusiform expansion of the bone results in cyst-like cavities with diaphyseal expansion. Radiographs are still the mainstay of evaluation of patients with bony lesions. Ultrasonography can detect soft-tissue extension of the bony lesions and guide drainage or biopsy procedures. CT accurately demonstrates bony sclerosis and destruction, especially in areas difficult to assess on radiographs such as the posterior elements of the vertebral body. MRI is the modality of choice in evaluating early marrow involvement and soft-tissue extension of the lesion.

A large number of artifacts occur in magnetic resonance (MR) imaging of the musculoskeletal system. These artifacts may potentially affect the quality of MR images, and may also simulate pathologic conditions and produce pitfalls in interpretation. Motion artifacts may be periodic or random. Protocol-error artifacts include saturation, wraparound, radiofrequency (RF) interference, shading, and partial volume averaging artifacts. Truncation artifacts occur when the number of phase-encoding steps of high spatial frequencies is insufficient (or under-sampled) for faithful reproduction of the true anatomic detail of the original image. Chemical shift artifacts are due to the protons in fat being mismapped relative to water protons. Susceptibility artifacts occur at the interfaces of structures with different magnetic susceptibilities. Artifacts special to the musculoskeletal system include the magnic angle phenomenon and spurious signal induced at very short echo times, both of which affect anisotropic structures such as tendon, ligament, and cartilage. Recognition and, if possible, correction of these artifacts are an important aspect of practical musculoskeletal MR imaging.

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Diffusion weighted MRI was performed on patients with acute vertebral body compression. The usefulness of the apparent diffusion coefficient (ADC) in differentiating between benign and malignant fractures was evaluated. A total of 49 acute vertebral body compression fractures were found in 32 patients. 25 fractures in 18 patients were due to osteoporosis, 18 fractures in 12 patients were histologically proven to be due to malignancy, and 6 fractures in 2 patients were due to tuberculosis. Signal intensities on T(1) weighted, short tau inversion recovery (STIR) and diffusion weighted images were compared. ADC values of normal and abnormal vertebral bodies were calculated. Except for two patients with sclerotic metastases, benign acute vertebral fractures were hypointense and malignant acute vertebral fractures were hyperintense with respect to normal bone marrow on diffusion weighted images. Mean combined ADCs (ADC(cmb); average of the combined ADCs in the x, y and z diffusion directions) were 0.23 x 10(-3) mm(2) s(-1) in normal vertebrae, 0.82 x 10(-3) mm(2) s(-1) in malignant acute vertebral fractures and 1.94 x 10(-3) mm(2) s(-1) in benign acute vertebral fractures. The differences between ADC(cmb) values were statistically significant (p<0.001). The ADC is useful in differentiating benign from malignant acute vertebral body compression fractures, but there may be overlapping ADC values between malignant fractures and tuberculous spondylitis.