Topic 1 MSK Flashcards
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
What are bundles surrounded by?
perimysium (connective tissue, blood vessels, nerves, and adipose tissue) also called the fibroadipose septa
What do bundles form?
The muscle
What is the muscle covered by?
epimysium.
What may separate single muscles or groups of muscle?
A fascial layer
What are the three parts of a skeletal muscle?
Tendinous origin, Muscle belly, tendinous insertion
Briefly describe the ultrasound appearance of muscle
- Bundles of fibres appear as homogeneous and hypoechoic striated bundles.
- The perimysium surrounds the bundles is a thin echogenic linear septations arranged longitudinally within the muscle substance, dispersed throughout the bundles
- epimysium appears as a thin echogenic layer surrounding the periphery of the muscle.
- Adjoining muscles are separated by a slightly thicker echogenic fascial layer.
What are tendons made up of?
tightly packed collagen fibres arranged in parallel bundles. These fibres are relatively avascular.
What is the peritenon?
• a layer of connective tissue that wraps around the tendon and sends intratendinous septae between the bundles of fibres.
Why is the musculotendinous juntion important to examin closely?
prone to tear during stresses.
Where do tendons usually attach?
usually attach to bone at sites of tuberosities, ridges, or spinae
What are retinacula?
fibrous sheaths that cover parts of tendons to provide stability and to keep certain tendons close to the bone
What is a synovial sheath?
a double layered sheath containing a thin layer of synovial fluid that allows the tendon to glide smoothly
What are synovial bursae?
small fluid filled pouches that act as bolsters to facilitate the dynamics of associated tendons and muscles, reducing friction between two structures.
What is the ultrasound appearance of tendons?
• The bundles of fibres appear as echogenic linear structures in their longitudinal orientation, and as a bundle of finely punctated echogenic foci when viewed transversely.
What is the ultrasound appearance of the peritenon?
a thin echogenic layer around the tendon, often indiscernible from the tendon itself.
What is the ultrasound appearance of the synovial sheath?
it appears as two thin echogenic layers around the tendon, with a very thin (< 1 mm) layer of anechoic synovial fluid within the layers.
What is the ultrasound appearance of nerves?
- Peripheral nerves typically appear as linear bundles of multiple hyper and hypoechoic fascicles, with a ‘honeycomb-like’ appearance when viewed in transverse.
- The nerves are usually small in diameter (3 mm to 5-6 mm).
- The overall nerve shape is rounded or slightly ellipsoid in cross-section, and evenly linear in a longitudinal plane.
- Nerve fibres have a similar echotexture to tendons, but are slightly less echogenic than tendon fibres.
How does size affect the ultrasound appearance of a nerve?
Larger nerves like the median nerve take on the honeycomb appearance
Smaller nerves tend to appear as tri-laminar structures as seen in the included image of the radial nerve.
What are the muscles of the anterior thigh?
Pectineus Iliopsoas Tensor fascia lata Sartorius Rectus femoris Vastus lateralis Vastus medialis Vastus intermedius
What is the pectineus origin and insertion?
Superior pubic ramus
Pectineal line of femur
What is the iliopsoas origin and insertion?
Transverse processes of lumbar spine, iliac crest, iliac fossa
Lesser trochanter
What is the TFL origin and insertion?
ASIS anteriorly
ITB attachment at lateral tibial condyle
What is the Sartorius origin and insertion?
ASIS
Pes anserinus
What is the rectus femoris origin and insertion?
AIIS Patella
What is the vastus lateralis origin and insertion?
Greater trochanter
Patella
What is the vastus medialis origin and insertion?
Intertrochanteric line
Patella
What is the vastus intermedius origin and insertion?
Anterior and lateral surface of body of femur
Patella
What are the muscles of the medial thigh?
Adductor longus Adductor brevis Adductor magnus Gracilis Obturator externus
What is the adductor longus origin and insertion?
Inferior pubic ramus
Middle 1/3 linea aspera
What is the adductor brevis origin and insertion?
Inferior pubic ramus
Pectineal line and prox linea aspera
What is the adductor magnus origin and insertion?
Inferior pubic ramus and ischial tuberosity
Linea aspera, medial supracondylar line and adductor tubercle of femur
What is the gracilis origin and insertion?
Medial inferior pubic ramus
Pes anserinus
What is the obturator externus origin and insertion?
Margins of obturator foramen
Trochanteric fossa of femur
What are the muscles of the posterior thigh?
Semitendinosus
Semimembranosus
Biceps femoris
What is the semitendinosus origin and insertion?
Ischial tuberosity
Pes anserinus
What is the semimembranosus origin and insertion?
Ischial tuberosity
Posterior medial condyle of tibia
What is the biceps femoris origin and insertion?
Long head- Ischial tuberosity
Short head - Linea aspera
Insertion - Lateral head fibula
What are the anterior muscles of the calf?
Tibialis anterior
Extensor digitorum longus
Extensor hallucis longus
Peroneus tertius
What is the tibialis anterior origin and insertion?
Antero-lateral tibial Condyle
Medial cuneiform and base first metatarsal
What is the EDL origin and insertion?
Antero-lateral tibial Condyle
Middle and distal phalanges of four digits
What is the EHL origin and insertion?
Middle anterior fibula
Base of distal phalanx, dorsum great toe
What is the peroneus tertius origin and insertion?
Inferior 1/3 of anterior fibula and interosseous membrane
Dorsum base fifth MT
What are the lateral muscles of the calf?
Peroneus longus
Peroneus brevis
What is the peroneus longus origin and insertion?
Head lateral fibula
Base first metatarsal and medial cuneiform
What is the peroneus brevis origin and insertion?
Inferior 2/3 lateral fibula
Base fifth metatarsal
What are the superficial muscles of the posterior calf?
Lateral gastrocs
Medial gastrocs
Soleus
Plantaris
What is the lateral gastrocs origin and insertion?
Lateral femoral condyle
Posterior calcaneus
What is the medial gastrocs origin and insertion?
Medial femoral condyle
Posterior calcaneus
What is the soleus origin and insertion?
Posterior prox. fibula and prox medial border of tibia Posterior calcaneus
What is the plantaris origin and insertion?
Lateral supracondylar line of femur
Posterior calcaneus
What are the deep muscles of the posterior calf?
Popliteus
Flexor hallucis longus
Flexor digitorum longus
Tibialis posterior
What is the popliteus origin and insertion?
Lateral surface of lateral Condyle of femur
Posterior prox tibia
What is the FHL origin and insertion?
Inferior 2/3 posterior fibula
Base of distal phalanx of great toe
What is the FDL origin and insertion?
Postero-medial tibia
Bases of distal phalanges of four digits
What is the tibialis posterior origin and insertion?
Interosseous membrane and posterior tibia and fibula Navicular, cuneiform, bases 2nd and 3rd bones
