1190: Tendon ultrasound

Abstract

There are two types of tendons: those covered with a synovial sheath, and those covered with dense connective tissue called paratendon. Tendons are formed by connective tissue, which is a fibrous, dense structure with collagen fibers directed in a longitudinal way, and these are poorly vascularized. Those covered with synovial sheath contain a small amount of synovial fluid, which facilitates mobility. Normal tendons are very echogenic, with a fibrous internal structure, which is shown better in a longitudinal sonogram (along the long axis of the tendon). The most important echographic artifact of this kind of fibers is a false hypoechoic image, derived from the oblique orientation of the ultrasound beam. In perpendicular orientation at 90°, the direction of the beam of the ultrasound in relation to the position of the tendon fibers avoids artifacts or false images. Thus, correct perpendicular position of the probe beam in relation to the tendon fibers is extremely important. Tendon pathology: The most common cause for the examination of tendons includes swelling, rupture, subluxation or luxation. In tendinosis, the tendons covered by a sheath have a sonographic appearance different from those that lack it. These swellings are associated with liquid collections inside the sheath, tendon enlargement, and/or hypoechogenicity inside the tendon. The abnormal liquid collection can produce a hypoechoic ring around the tendon, which is normally significant when larger than 2 mm (0,005 in). In those tendons that do not have synovial sheath, the enlargement of the tendon can be focalized or globalized. In acute inflammatory processes, the tendon is edematous, its echogenicity diminished and its contours are badly defined. In chronic inflammatory processes, the difference is set by calcium intratendinous deposits, which produce posterior shadowing, and important enlargement of the fiber. This guides the sonographist and s/he can recognize when the process became chronic. There are two types of tendons: those covered with a synovial sheath, and those covered with dense connective tissue called paratendon. Tendons are formed by connective tissue, which is a fibrous, dense structure with collagen fibers directed in a longitudinal way, and these are poorly vascularized. Those covered with synovial sheath contain a small amount of synovial fluid, which facilitates mobility. Normal tendons are very echogenic, with a fibrous internal structure, which is shown better in a longitudinal sonogram (along the long axis of the tendon). The most important echographic artifact of this kind of fibers is a false hypoechoic image, derived from the oblique orientation of the ultrasound beam. In perpendicular orientation at 90°, the direction of the beam of the ultrasound in relation to the position of the tendon fibers avoids artifacts or false images. Thus, correct perpendicular position of the probe beam in relation to the tendon fibers is extremely important. Tendon pathology: The most common cause for the examination of tendons includes swelling, rupture, subluxation or luxation. In tendinosis, the tendons covered by a sheath have a sonographic appearance different from those that lack it. These swellings are associated with liquid collections inside the sheath, tendon enlargement, and/or hypoechogenicity inside the tendon. The abnormal liquid collection can produce a hypoechoic ring around the tendon, which is normally significant when larger than 2 mm (0,005 in). In those tendons that do not have synovial sheath, the enlargement of the tendon can be focalized or globalized. In acute inflammatory processes, the tendon is edematous, its echogenicity diminished and its contours are badly defined. In chronic inflammatory processes, the difference is set by calcium intratendinous deposits, which produce posterior shadowing, and important enlargement of the fiber. This guides the sonographist and s/he can recognize when the process became chronic.