What are 4 uses for ultrasound in the setting of MSK trauma?
o 1. Detect muscle tears
o 2. Assess the extent of muscle tears
o 3. Evaluate the healing process
o 4. Assist in the aspiration of hematoma when indicated
What is a muscle strain?
• When pain is acute and persistent, beginning during exercise, and not related to muscle rupture, it is referred to as muscle strain
What is DOMS?
• When pain starts hours to days after exercise, it is called delayed onset muscle soreness (DOMS)
How does an ultrasound appear in the setting of DOMs?
• Ultrasound is often normal but helps in excluding muscle tear or intramuscular hematoma, which may clinically mimic DOMS
What is ultrasound used for when a mass is clinically palpable or is suspected?
- confirm a muscular mass
- exclude causes of pseudomuscular mass of the extremities, such as accessory muscle, muscle herniation, or subcutaneous edema.
- locate and delineate the mass by determining its exact location in the muscle
- To characterize the mass.
- distinguishing cystic from solid muscular masses, presence of calcifications or ossifications in the mass
- guiding a biopsy
What are the ultrasound features of a partial muscle tear?
- Discontinuity in the muscle fibers and the fibrous septa
- Hematoma appearing as a hypoechoic fluid filling the gap in the torn muscle
- Echoic debris in the hematoma, representing muscle fragments or blood clot
- Shaggy margins of the torn muscle
- Interfascial fluid collection is a sign of fascial tear
What are the ultrasound features of a complete muscle tear?
- A retracted and hyperechoic muscle
- Surrounded by a large hematoma (“bell clapper” appearance)
- Fascial tear may be demonstrated by US
What constitutes a grade 1 partial tear?
May be normal
Focal fibre discontinuity
Small haematoma <1cm
What constitutes a grade 2cpartial tear?
Fibres rupture involving <1/3 or the of the muscle surface
Moderate haematoma <3cm
Small interfascial haematoma
What constitutes a grade 3 partial tear?
Fibres rupture involving >/3 of the muscle surface
Large haematoma >3cm
Large interfascial haematoma
What is shadowing?
occurs posterior to a highly reflective interface, where most of the incident sound beam is reflected, producing a signal void or shadow posterior to that structure.
What is posterior enhancement?
- sound travels through an anechoic structure it is not attenuated as much as the surrounding tissue, and more sound is available to image the deeper tissues
- The echoes returning are of greater amplitude, further amplified by the time gain compensation.
- The result is a false impression of increased echogenicity from deeper structures.
What is the comet tail artefact?
- Reverberation occurs within a glass or metallic object when the sound beam is repeatedly reflected between the highly reflective anterior and posterior walls.
- The resultant artifact is echogenic bands placed at equal depth from each other, with the periodicity of the bands equal to the thickness of the object.
What is refraction artefact?
- bending of the beam when travelling from one material and into another of differing acoustic impedance
- can result in a real lesion being depicted at an incorrect location
- minimised by having the angle of incidence as close to 90 degrees as possible.
What is the speed of sound artefact?
- Ultrasound equipment calculates distance based on the time a sound pulse takes to return as an echo, and on the assumption that there is a constant speed of sound
- within the human body there are slight variations in the speeds that sound can travel at through differing tissues.
- The artefact produced may be an object shown at an incorrect depth.
What is beam width artefact?
When an object is smaller than the beam width, echoes depicted at that location are a combination of the echoes from that object and the surrounding tissues. It is the same as ‘volume averaging’ in CT and MRI.
What is anisotropy?
• Anisotropy is a false hypoechogenicity of a structure due to the obliquity of the ultrasound beam
Why is recognising anisotropy important?
• can mimic abnormal hypoechoic pathology in a normal tendon or muscle
How can anisotropy ne eliminated?
- the structure to be scanned should be perpendicular to the ultrasound beam (parallel to the transducer face)
What are some ways to bring a structure perpendicular to the transducer face when attempting to limit anisotropy?
• positioning the limb to align the tendon or muscle in a more linear approach
- angling the transducer to bring the ultrasound beam perpendicular to the structure (‘heel-toeing’)
• The use of a stand-off pad to facilitate heel-toeing, or the use of an angled stand-off on the transducer face will help achieve the desired result.
What structure is most effected by anisotropy?
Tendons
When can anisotropy be useful?
To differentiate tendons from surrounding structures
What are muscle fibres surrounded by?
endomysium (extensive network of capillaries and nerves)
What are groups of fibres referred to as?
Bundles
-
Topic 1 MSK79
-
Topic 2 Pathology Tendons muscles nerves112
-
Topic 3 the shoulder116
-
Topic 4 elbow65
-
Topic 4 hand and wrist82
-
Topic 5 - The hip39
-
Topic 6 - the knee39
-
Topic 7 - the foot and ankle76
-
Topic 8 - Lumps and bump60
-
Topic 9 - intro to paeds70
-
topic 10 - paediatric urinary tract and adrenals97
-
Topic 11 - cranial ultrasound24
-
Topic 11 - cranial pathology61
-
Topic 12 - paediatric small parts41
-
Practice exam56
