MSK Flashcards
USF of rotator cuff tendinosis
Best diagnostic clue: Diffusely thickened tendon with variable hypoechogenicity and loss of normal fibrillar pattern • Focal hypoechoic areas can be difficult to distinguish from intra substance tears; tears tend to be more linear • Non-intrasubstance tears are discernible through changes in tendon contour (contour flattening, retraction, fluid gap) • In severe cases, tendon is severely thickened and diffusely hypoechoic
Tendinosis generally affects all rotator cuff tendons to some degree with supraspinatus most affected • Biceps tendinosis usually accompanies rotator cuff tendinosis • Tendon hyperemia is not a feature of rotator cuff tendinosis • Cortical defects and irregularity in and around tendon insertional area commonly associated
Checklist for rotator cuff tendinosis
Systematic examination; look especially at edges for contour deformity; confirm suspected abnormalities in orthogonal plane
USF for rotator cuff tears
Best diagnostic clue: Discontinuity of tendon filled with fluid
Supraspinatus tendon tears close to or at insertional area • Anterior fibers most commonly torn • Gap filled with echogenic fluid or blood +/- gas locules (comet tail artifacts) • Focal flattening of convex bursal surface • Retraction of tendon from insertional area or blunting of edge of tendon insertion • Intrasubstance tear: Linear irregular sharp hypoechoic area within tendon substance
Recognition of intrasubstance tears difficult in moderate to severe tendinosis • Complete tear with retraction: Non-visualization of tendon • Fluid within subacromial-subdeltoid bursa • Muscle atrophy assessed at level of scapular spine (better by MR)
USF of non rotator cuff tendinosis
Imaging Findings • Best diagnostic clue: Focal, nodular or diffuse tendon enlargement with loss of normal fibrillar echotexture • Increased tendon thickening with hypoechogenicity and progressive loss of normal fibrillar pattern • Some tendons (Achilles, patellar, posterior tibialis, rotator cuff tendon, common extensor tendons of forearm) are more susceptible to tendinosis • Cross-sectional area measurements useful for follow-up rather than diagnosis • Level of hyperemia correlates with disease activity • Partial tears seen as sharp linear hypoechoic defect within area of tendinosis • May be difficult to detect in severe tendinosis • Should not be confused with vascular channels within tendon
Secondary signs include adjacent bursitis (Achilles, common extensor), reactive bone changes, paratenon (Achilles, patella) and synovial inflammation
Checklist for non rotator cuff tendonosis
Examine para tenon or synovial sheath and paratendinous tissues for inflammatory change separate from tendinosis • Routinely examine with color Doppler
USF of non rotator cuff tears
Fluid-filled gap within tendon, either partial thickness, full-thickness/complete • In acute phase, gap may be filled with blood +/- gas locules making tendon ends difficult to see • Look for depressed tendon edges at site of tear • Larger tendons tend to tear transversely while smaller tendons tend to tear either longitudinally or transversely • Tendon ends often swollen, especially finger tendons, improving visibility on ultrasound examination • Swelling of tendon ends can impede ultrasound assessment regarding presence and severity of pre-existing tendinosis • Collapsed synovial sheath may be mistaken for attenuated tendon
Reparative hypoechoic granulation tissue and fibrosis may bridge gap in chronic complete tendon tears • Incomplete tendon tears also heal by hypoechoic reparative granulation tissue • Ultrasound accurate at detecting re-tear or defining cause of limitation of movement following repair • Tendon remains swollen and hyperemic long after tendon integrity and strength has returned • Best imaging tool: Ultrasound confirms tendon tears with high accuracy and precision • For small tendons, examine first in transverse plane along length of tendon
Checklist for non rotator cuff tendonitis
Examine entire of length of tendon looking for fluid-filled gap, empty tendon sheath (small tendons) or focal depression of tendon surface
USF of soft tissue infection
Cellulitis
• Edema and hyperemia of subcutaneous fat • Edematous fat is echogenic on ultrasound • Thickened interlobular septa • ±Periseptal fluid & fluid above investing fascia
• Necrotizing fasciitis • Affects subcutaneous fat, fascia and muscle, Thickened disrupted fascia with perifascial fluid (fluid above and below investing fascia) • Severe associated subcutaneous and muscle edema • ±Muscle necrosis (difficult to detect)
• Pyomyositis • Diffuse muscle swelling with edema ± hyperemia • Edematous muscle is echogenic on ultrasound • ±Focal hypoechoic areas due to abscess, necrosis or serous exudate • Best imaging tool: Ultrasound ± ultrasound-guided aspiration gives sufficient information to make prompt diagnosis and guide treatment
USF of bakers cyst
Best diagnostic clue: Fluid-filled sac with neck arising from interspace between gastrocnemius muscle and semimembranosus tendon • Characteristic “talk-bubble” configuration on transverse scans • Cysts typically well-defined and thin-walled • Thick-walled cysts suggest inflammatory knee arthropathy or intra-cystic hemorrhage • Thick-walled cysts often have hyperemic walls • Cyst may be septated • Contain anechoic synovial fluid, typically gelatinous in consistency • Free fluid tracking adjacent to cyst indicates recent leakage
Irregular and multiloculated cysts may result from repeated cyst leakage and re-collection • Cysts usually extend distally superficial to medial belly gastrocnemius muscle • Contralateral subclinical Baker cysts common • USaccurately confirms presence, location and extent • Examine with patient prone, knees extended • Follow medial belly of gastrocnemius proximally and locate interspace between medial gastrocnemius head and semimembranosus tendon • Routinely examine contralateral side
Checklist for bakers cyst
Consider
• Intra-articular CHECKLIST pathology as this is very frequently associated with Baker cysts in adults
Image Interpretation Pearls
• Look for characteristic “talk-bubb]e” configuration of cyst on transverse imaging
USF of bursitis
Ultrasonographic Findings
• Subacromial-subdeltoid (SASD) bursa
o Fluid collects in dependent positions
• Lateral aspect greater tuberosity (teardrop configuration) over biceps, near coracoid & also deep to acromion
• Fluid in bursa over biceps groove is separate from intra-articular fluid in long head biceps tendon sheath
• MR marginally more sensitive than ultrasound at detecting SASDfluid (transducer effacement, subacromial location)
o Bursal fluid strongly associated with supraspinatus tendon tea rs
o Bursal wall th ickening & hyperemia generally not a feature
• If present, consider inflammatory arthropathy (e.g., SL£)
• Bursa most commonly affected by inflammatory arthropathy
• ±Rice bodies
• Small rice bodies better seen by MR
Checklist for bursitis
Consider
• Small amount of fluid may be normal in subacromial-subdeltoid bursa, deep infrapatellar bursa, retrocalcaneal bursa o MR more sensitive to very small amounts of fluid than ultrasound • Bursitis is common; infective bursitis is uncommon • Ch ronic bursitis often associated with wall-thickening & internal debris
Inflammatory arthropathy if SASDbursa thick-walled ± hyperemic
Image Interpretation Pearls
• Fluid distended sac in typical location
USF for peripheral lipoma
Well-defined, encapsulated mass, isoechoic to fat • May be slightly hyperechoic or hypoechoic • Distinctive, fine linear striations parallel to skin • Small lesions may not have demonstrable capsule • Acoustic enhancement not a feature • Compressible similar to adjacent fat • Absent or minimal internal vascularity on color Doppler imaging • Ultrasound findings diagnostic in majority of cases • Subfasciallipomas more variable in appearance • ±MR to confirm lipomatous nature of mass & to exclude features of liposarcoma
USF of soft tissue sarcoma
Large heterogeneous hypoechoic mass • Usually located in deep (subfascial) tissues • Well-encapsulated • ±Myxoid tissue: Well-defined, intra-tumoral anechoic or hypoechoic areas
Necrosis: Poorly-defined hypoechoic areas • ±Calcification: Discrete intra-tumoral echogenic foci with acoustic shadowing • ±Hemorrhage: Ill-defined intra-tumoral echogenic areas without acoustic shadowing • Usually hypervascular with disorganized vascular pattern on color Doppler imaging • 16-gauge or 14-gauge Tru-cut core biopsy with co-axial system necessary for tissue typing & histological staging
Fine-needle aspiration for cytology (FNAC) is not sufficient for initial diagnosis • FNAC useful for detecting residual disease, recurrence or deep-seated retroperitoneal lesions • Concentrate on defining tumor extent • Assess relation to neurovascular bundle & bone
Assess regional nodes
Checklist for peripheral lipoma
Often not possible to distinguish deep-seated lipoma from well-differentiated percutaneous biopsy liposarcoma on imaging or • For deep-seated lesions => MR • Fine internal striations = characteristic US finding
Palpable tumor not initially identifiable on MR => usually a subcutaneous lipoma
Checklist for soft tissue sarcoma
Nearly all STS are well-defined (Le. sharp definition does not equate to benign tumor)
