Principles of Musculoskeletal Ultrasound Imaging Updated 3 July 2012
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General Principles of Musculoskeletal Ultrasound
Alice Chiu SPT DKCH 3 July 2012
Basic considerations Equipment Selection
◦ High Frequency, linear array transducers are best for
tissues with striated morphology of tissues e.g mm,
ligt in superficial location. (5-14MHz) (7.5MHz)
◦ Adequate greyscale is necessary for accurate
diagnostic interpretation-optimal image settings.
Probe Placement
◦ If the image states is a midline image, be sure to be
as close to midline as possible
Image Orientation
◦ Longitudinal view: left side of image is CEPHALAD
◦ Transverse view: left side of the image is the
PATIENT’s RIGHT
Suggested Exam Protocol◦Bilateral studies not absolute
necessary◦Not necessary to perform all images
for each extremity: selection◦Usually perform images in the area
of complaint◦Usual practice: no less than 6 images
per exam with 3 transverses and 3 longitudinal images
Identification of bony landmarks during imaging is key success for
accurate soft tissue labeling.
Reflectivity-echogenicityHigh reflective pattern: whiter and
brighter-hyperechoicLow reflective pattern: darker and less
bright-hypoechoicNo reflectivity-clear fluid-anechoicSame reflectivity surrounding tissue-
isoechoic
HyperechoicHypoechoic
Anechoic Isoechic
Basic Normal Musculoskeletal Ultrasound Anatomy Skeletal Muscle
◦Long view: muscle septae appear as bright/echogenic structures and are seen as thin bright linear band.
◦Transverse views: muscle bundles appear as speckled echos with short curvilinear bright lines dispersed throughout the darker/hypoechoic background
Subcutaneous Tissue◦Isoechoic( equal brightness) with
skeletal muscle. ◦Main difference: septa do not lay in
lines or layers. ◦It usually appears as a thick
continuous, hyperechoic band usually separate subcutaneous fat from muscle.
Cortical Bone◦Appears as a continuous echogenic
( bright ) line with posterior acoustic shadowing ( black)
Fascia◦Collagenous structure that usually
surrounds the musculotendinous areas of the extremities.
◦The fascia is encompassed by subcutaneous tissue.
◦Fascia is seen inserting into bone, blending with periosteum.
◦Appears as a fibrous, bright/hyperechoic structure.
Periosteum◦A thin echogenic line running parallel
with the cortical bone.◦Not usually not visualized by US
except after cortex damages, periosseous soft tissues and periosteum will produce a perisoteal reaction visible by US.
Tendons◦A bright/echogenic linear band that can
vary in thickness according to its location.◦Tendons are known to be anisotropic
structures in US nomenclature.◦On Longitudinal views: fibrillar
echotexture.◦The parallel series of collagen fibers are
hyperechoic, separated by darker/hypoechoic surrounding connective tissues.
◦The fibres will be continuous/intact.◦ Interruptions in tendon fibres are
visualised as anechoic /black areas within the tendon.
Anisotropy The physical characteristic of muscle, tendons
and nerves to vary in their ultrasound appearances depending upon the angle of insonation of the incident sound beam. Produced when the probe is not perpendicular with the structure being evaluated.
The apparent change in echogenicity within the structure may mimic the appearance of fluid or lead to loss of visulisation of the structure.
Thus angulation of probe is important for beam to insonates at 90 degree
Most common artifact in MS US
Anisotropy artifact. Transverse sonograms of the extensor surface of the wrist show the extensor digitorum (ED) and extensor pollicis longus (EPL) tendons, clearly and without artifact on the image obtained with the probe held exactly perpendicular to the tendons
but with a significant loss of echogenicity on the image obtained with the probe held at an oblique angle to the tendons
Tendon pathology◦Tendonitis: acute ◦Tendinoses/tendinosis : chronic, may
have ischemia in critical zones followed by myxoid degeneration Caused by degenerative process,
overuse, steriod injection, systemic disease etc…
Ligaments◦Bright echogenic linear structure.◦Have more compact fibrillar
echotexture.◦Individual strands/fibers of the
ligaments are closely aligned.◦Ligaments are composed of dense
connective tissue, like tendons, but there is much variability in the amounts of collagen, elastin and fibrocartilage within a ligament, which makes its ultrasound appearance more variable than tendons.
ATFL- lat malleolus with talus
CFL- lat malleoulus with calcaneous
Ultrasound grading of ligt injury◦Grade I: mild stretching-normal◦Grade II: partial tear-thickened
hypoechoic◦Grade III: complete tear-complete
disruption
I II III
Bursae◦Thin black/anechoic line no more
than 2 mm thick. ◦Will fill with fluid due to irritation or
infection and become distend and enlarge.
◦Internal brightness echoes are inflammatory debris.
Longitudinal sonogram shows 30-year-old man with knee pain. Fluid is visible in deep infrapatellar bursa (solid arrow), indicating deep infrapatellar bursitis. Patellar tendon is normal (open arrow), but overlying soft tissues appear swollen (arrowhead).
Peripheral Nerves◦Appear a parallel hyperechoic lines
with hypoechoic separations between them.
◦Longitudinal view: appearance similar to tendons but less bright/echogenic.
◦Transverse view: the peripheral nerve individual fibers and fibrous matrix, present with multiple punctate echogenicities( bright dots) within an ovid well defined nerve sheath.
Longitudinal sonogram of the median nerve shows parallel hypoechoic groups of nerve fascicles and the median nerve, which lies deep to the flexor digitorum superficialis (FDS) muscle in the distal forearm.
Sequel…
References Introduction to Musculoskeletal Ultrasound
Imaging Randy E Moore DC RDMSwww.mskmasters.com John Lin at el, “ An illustrated Tutorial of
Musculoskeletal sonography” AJR:175, Sept 2000
www.essr.org/Real Time Ultrasound in Physiotherapy
Practice AIU
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