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Musculoskeletal Imaging

Tear

a disruption of the continuity of a tissue or structure; tear is sometimes used synonymously with rupture ( Fig.1, Fig.2, Fig.3).

Tears of the meniscus

of the knee may be traumatic or degenerative. Traumatic tears are usually vertical tears that may propagate in a longitudinal or transverse direction and commonly involve the thin edge of the meniscus, whereas degenerative tears are horizontal cleavage lesions that typically occupy the posterior half of the menisci. A positive McMurray test, consisting of an audible snap or pop as an abnormal meniscus extends over a bone protuberance, is a helpful clinical indicator of the diagnosis of meniscal tear. Arthrography is highly accurate diagnostically. A vertical concentric tear appears as a vertical radiodense line extending through the meniscus. Displacement of the inner fragment may lead to production of a bucket handle tear. In contrast, a vertical radial tear along the inner contour of the meniscus produces a contrast-coated inner meniscal margin and a blunted meniscal shadow. Horizontal tears produce a radiopaque line of contrast material that extends to the superior or inferior surface. On MR imaging, the two criteria for diagnosis of the meniscal tear are intrameniscal signal intensity that extends to a meniscal surface and abnormal meniscal morphology, such as an abrupt change of contour or focal deformity of the meniscus. With bucket-handle tears a foreshortened and blunted meniscus with central displacement of its inner fragment is observed on MR images.

Tears of the patellar and quadriceps tendons

may result from indirect forces or be associated with systemic disorders, such as rheumatoid arthritis, chronic renal disease and systemic lupus erythematosus. Complete tears of the patellar tendon are associated with a high position of the patella (patella alta), whereas complete tears of the quadriceps tendon may lead to an inferior position of the patella (patella baja). Although CT and ultrasonography can be used to verify the presence of tears of the patellar tendon, MR imaging displays these tears most vividly. Partial or complete tears of the quadriceps tendon may occur spontaneously in patients with systemic lupus erythematosus, rheumatoid arthritis, gout or renal failure. Standard arthrography and ultrasonography are useful in assessment of these tears, and sagittal MR images display the quadriceps tendon in exquisite detail.

Tears of the tendons of the ankle and foot

may be acute or chronic, and partial or complete. With MR imaging, recent tendon tears frequently reveal regions of increased signal intensity in T2-weighted spin-echo MR images and in certain gradient echo images. Because of the presence of scar tissue, remote tendon tears do not generally have these high signal intensity characteristics. Three MR imaging patterns have been described: type 1 represents partial tendon rupture with tendon hypertrophy and is characterized by heterogeneous signal intensity; type 2 is a partial tendon rupture with tendon attenuation; type 3 is a complete tendon rupture with tendon retraction, in which the tendon appears discontinuous. See Achilles tendon (III:1), Fig. 1.

Tears of the rotator cuff

may be complete (full-thickness) or incomplete (partial thickness). In complete tears an abnormal communication between the glenohumer abnormalities of the rotator cuff. See rotator cuff (III:1), Fig. 2.

Tears of the acetabular labrum

in adults are frequently associated with developmental dysplasia of the hip DDH . On standard arthrography the acetabular labrum may have an abnormal shape, characterized by enlargement and a rounded contour, and the actual tears may not be opacified. These findings have been designated acetabular rim syndrome.

The spine

Tears of the outer fibres of the anulus fibrosus or Sharpeys fibres are suspected as a precipitating factor in spondylosis deformans.

Complete tears of the Achilles tendon

may occur after strenuous activity requiring sudden or forceful dorsiflexion or pushoff of the foot. Predisposing factors include chronic tendinitis, tendon ossification or calcification, rheumatoid arthritis, systemic lupus erythematosus, and local injection or systemic administration of corticosteroid preparations. See tendinitis (III:1), Fig. 1, tendon (III:1), Fig. 1.

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Fig.1

Tear, meniscal. Coronal fat-suppressed proton-density-weighted MR image demonstrates a tear in the body of the medial meniscus (arrow). (Courtesy of Ben Edwards, MD, Savannah, GA)
Tear, Fig.1
Tear, Fig.2
Tear, Fig.3