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Extremities

Tendons are strong specular reflectors - fibrillar pattern - closely spaced, parallel, bright linear reflections at 90 degrees. Anisotropy (variable echogenicity based on the orientation of the transducer). Muscle is composed of many fascicles (hypoechoic) separated by fibrous tissue - perimysium (echogenic). Peripheral nerves are hypoechoic surrounded by hyperechoic epineurium.


Tendon Rupture

Blunt tendon tip, refractive shadowing, Nonvisualization, Mass, loss of fibrillar architecture, fluid collection


Tendonitis, Tenosynovitis

Fluid distending the tendon sheath and/or thickening of the tendon sheath


Rotator cuff

4 tendons: Subscapularis, Supraspinatus, Infraspinatus, Teres minor --> band of tissue covering the humeral head.

Series of layers from deep to superficial:

  • Echogenic humeral head
  • Anechoic or hypoechoic articular cartilage
  • Echogenic rotator cuff
  • hypoechoic subdeltoid bursa
  • Hyperechoic peribursal fat
  • Hypoechoic deltoid muscle
  • Subcutaneous tissues
Normal cuff: outer convexity contour, lack of compressibility w/ transducer


Rotator cuff tears

The majority of tears originate at the site of insertion of the supraspinatus to the greater tuberosity. From here they may extend posteriorly to the infraspinatus, medially to the more proximal supraspinatus.

Full thickness tears:

  • Wet tear - fluid filled defect
  • Dry tear - subdeltoid bursa and fat drops into the defect - converts normal convex interface, if not visible, pressure w/ transducer can push the bursa and fat into the anechoic or hypoechoic defect (compressibility), non-visualization of the cuff
Supraspinatus tear: the tear involves only first 1.5 cm of cuff behind the biceps tendon
Infraspinatus tear: if more than 1.5 cm, supraspinatus and infraspinatus
Partial thickness tears: hypoechoic defect, not associated w/ contour changes and do not compress w/ transducer pressure
Calcific tendinitis: painful, echogenic w/ shadow


Bursas


Baker’s cyst

Between medial head of gastrocnemius and the semimembranosus tendon. Simple, internal septations, irregular thick walls, nodular synovial proliferation, loose bodies. Beak like appearance of the neck protruding between medial gastroc and the semimembranosus tendon. If ruptures, fluid tracking into the calf


Masses

cystic, complex, solid, localizing, relationship, vascularity


Ganglion cysts

70% originate from scapholunate joint over the dorsal surface of the wrist. 20% arise on the volar side around the flexor carpi radialis tendon or the radial artery. 10% arise along the flexor tendon sheaths of the fingers and from the interphalangeal joints. Anechoic w/ well defined walls, through transmission


Giant cell tumor

2nd most common mass in the hand, bng lesion histologically identical to pigmented villonodular synovitis, volar surfaces of the fingers. Solid, homogeneous, hypoechoic masses w/ blood flow, (can be quite vascular) adjacent to tendons. Arise from sheath, not tendon, therefore they do not move w/ finger movement


Neurofibromas

In the middle of nerve


Schwannomas

In the periphery of nerve. Solid, hypoechoic, vascular


Morton’s neuroma

Mass of the plantar digital nerves, between metatarsal heads


Cellulitis

Edema, fluid dissects in the fibrinous retinaculum of the subq fat - marbled appearance


DVT

Normal arterial waveform of the extremity has high-resistance profile, triphasic. Exercise will transform waveform to low-resistance profile.

Sensitivity of US for DTV is 95% and specificity is 98%: Noncompressibility, Augmentation of venous flow by calf compression or plantar flexion. Alteration of the venous pulsatile (respiratory phasicity) waveform --> becomes blunted due to more central obstruction --> loss of respiratory phasicity (subclavian - thrombosis, stenosis, extrinsic compression)


Pseudoaneurysms

Extravascular blood flow near or adjacent to the artery (hematoma w/ persistent arterial communication via patent neck), yin-yang pattern, “to and fro” waveform pattern in the neck. Treatment: US guided injection of thrombin (contraindicated if wide neck or pseudoaneurysm is a part of AVF)


AVF

Below the femoral bifurcation, prominent perivascular tissue vibration, change from nl high-resistance pattern to low resistance flow in supplying artery and arterialization of venous waveform