Musculoskeletal Ultrasound - Basic

Ultrasound of Muscles (Basic)

1. Musculoskeletal Ultrasound Presented by Syed Yousaf Farooq

2. INDICATIONS Indications for MSK ultrasound include but are not limited to: 1. Pain or dysfunction. 2 . Soft tissue or bone injury. 3 . Tendon or ligament pathology. 4 . Arthritis, synovitis , or crystal deposition disease. 5. Intra-articular bodies. 6 . Joint effusion. 7 . Nerve entrapment, injury, neuropathy, masses, or subluxation. 8 . Evaluation of soft tissue masses, swelling, or fluid collections.

3. 9. Detection of foreign bodies in the superficial soft tissues. 10 . Planning and guiding an invasive procedure. K. Congenital or developmental anomalies. 11 . Postoperative or post procedural evaluation An MSK ultrasound examination should be performed when there is a valid medical reason. There are no absolute contraindications. Makes musculoskeletal sonography a powerful tool for diagnosing abnormalities of the soft tissues.

4. Equipment Selection Musculoskeletal structures are long, striated and many times layered tissues. Due to the striated morphology of these tissues and their superficial location, high frequency, linear array transducers are best suited for this application. It is recommended that no less than 7.5 MHz transducers be used for musculoskeletal examinations of the extremities.

5. Probe Placement It is very important to maintain accurate transducers placement in musculoskeletal sonography. Due to the close proximity of several distinct structures in a small area, a slight displacement of the probe can produce inaccurate images.

6. ANISOTROPY Anisotropy is defined as the ability of a substance or material to display different properties, depending on the angle of insonation

7. POSTERIOR ACOUSTIC SHADOWING

8. MUSCLE Muscle is made of bundles of contractile striated muscle fibers with their major axis lying along the contraction direction. These muscle fibers have a considerable length, varying from a few millimeters to several centimeters.

9. Muscle Muscle is externally surrounded by a thick connective sheath called the epimysium . From the internal aspect of this sheath several septa invigilate to form the perimysium , which surrounds diverse bundles of muscular fibers, named fascicles Very light and thin septa arising from the perymysium spread into the fascicles to surround every muscular fiber and form the endomysium .

10. PENNATION ANGLE It is the angle measured between the muscular fibers direction and the central Apo neurosis axis

11. Skeletal Muscle On longitudinal views, the muscle septae appear as echogenic structures, and are seen as thin bright linear bands.

12. On transverse views, the muscle bundles appear as speckled echoes with short, curvilinear bright lines dispersed throughout the hypoechoic background.

13. Cortical Bone On ultrasound examination, normal cortical bone appears as a continuous echogenic (bright) line with posterior acoustic shadowing (black).

14. TENDONS Transmit the muscular tension to mobile skeletal segments Extremely resistant to traction. Extremely variable shape and dimensions. Consist of about 70% of type I collagen fibers.

15. Tendon may either be: Supporting or Sliding tendon

16. SLIDING TENDONS SLIDING TENDONS are wrapped in a covering sheath ( tenosynovial sheath) Whose function is to guarantee better sliding and protection to the tendons when they run adjacent to irregular osseous surfaces, sites of potential friction.

17. In addition, US is the only technique that allows the sonologist to perform a dynamic study of tendons, which is extremely important for the diagnosis of tendon pathology.

18. TENDONS In long axis view; the tendons appear as echogenic ribbon-like bands, defined by a marginal hyperechoic line corresponding to the paratenon and characterized by a fibrillar internal structure . On ultrasound the parallel series of collagen fibers are hyperechoic , separated by hypoechoic surrounding connective tissue . Tendons are known to be anisotropic structures .

19. RETINACULUM Retinaculum is a transversal thickening of the deep fascia attached to a bone’s eminence. The biomechanical function of a retinaculum is to keep the tendons in position as they pass underneath it, in order to avoid their dislocation during muscular action.

20. Appear on ultrasound as thin hyper echoic structures located more superficially than the sliding tendons, in very critical areas from a biomechanical point of view. Dynamic Scanning and high amount of gel is used as a spacer in order to avoid any pressure on the tissue, for the evaluation of retinacula.

21. LIGAMENTS The structure of ligaments is very similar to that of tendons : The main differences are reduced thickness and a less regular arrangement of structural elements; for this reason, it is harder to study ligaments with US than tendons.

22. Types of ligaments Intrinsic capsular ligaments Extrinsic ligaments

23. LIGAMENTS Classified as; Extra-capsular ligaments & Intra-capsular ligaments

24. Ultrasonography The US examination of ligaments, unlike tendons, is mainly performed using long axis views, the transducer being aligned on the ligament’s major axis. Transverse views (short axis) have poor diagnostic value. With US, ligaments appear as homogeneous, hyper echoic bands, 2-3 mm thick, lying close to the bone.

25. MOST COMMON LIGAMENTS Ligaments of the medial and lateral compartments of the ankle: Deltoid Ligament Anterior Talo -fibular Ligament Fibulo-calcaneal Ligament

26. MOST COMMON LIGAMENTS The collateral ligaments of the knee. The collateral and annular ligaments of the elbow. The coraco-acromial and coraco -humeral ligaments of the shoulder. The ulnar collateral ligament of the thumb

27. THE LATERAL COMPARTMENT OF THE ANKLE. THE ANTERIOR TALO-FIBULAR LIGAMENT

28. BURSAE In a normal joint, the bursa is a thin black/ anechoic line no more than 2 mm thick. The bursa fills with fluid due to irritation or infection.

29. PERIPHERAL NERVES High-frequency transducers allow the visualization of peripheral nerves that pass close to the skin surface.

30. From an anatomical point of view, nerves are characterized by: A complex internal structure made of nervous fibers (containing axons, myelin sheaths and Schwann cells) grouped to form fascicles, and loose connective tissue (containing elastic fibers and vessels ) PERIPHERAL NERVES

31. US provides advantages over MR imaging, including: A higher spatial resolution and the ability to explore long segments of nerve trunks in a single study. To examine nerves in both static and dynamic states with real time scanning . Systematic scanning on short axis planes is preferred to follow the nerves contiguously throughout the limbs.

32. On long axis planes: Their appearance is similar to tendons, but less echogenic. Nerves typically appear as multiple hypoechoic parallel linear areas separated by hyperechoic bands.

33. On short axis planes: High-resolution US demonstrates nerves as honeycomb appearance. Multiple , punctate echogenicities (bright dots) within an ovoid, well-defined nerve sheath .

34. The outer boundaries of nerves are usually undefined due to; Similar hyperechoic appearance of both the superficial epineurium and the surrounding fat.

35. Nerves are compressible structures. Alter their shape depending on the volume of the anatomical spaces within which they run, As well as on the bulk and conformation of the perineural structures.

36. Cartilage Ultrasound has great potential for the evaluation of hyaline cartilage, as microscopic lesions could be imaged by transducers with a high spatial resolution. Limited dimensions of acoustic windows available for the visualization of the cartilage surfaces.

37. The most frequent artifacts in the examination of cartilage profile is the angle of insonation. As in the examination of femoral trochlea which is not totally perpendicular to the direction of the US beam due to its wavy orientation.

38. CARTILAGINOUS CHANGES These include: Loss of sharpness of the superficial margin Loss of transparency of the cartilaginous layer. Cartilage thinning and subchondral bone profile irregularities.

39. Thank you