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Equine Diagnostic Ultrasound 1

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sihirlifil's version from 2017-12-06 15:14

Introduction

Question Answer
Indications for ultrasoundEvaluate muscular, tendinous, ligamentous, synovial & bony abnormalities
Lesion ID & characterization
Follow-up: monitor healing, formulate post-injury exercise plan
Important points for restraint & preparationSedate appropriately (IV detomidine/butorphanol)
1 person at head
Clip skin over area to be examined, clean skin with soap, degrease with alcohol
Apply coupling gel (soaks in over time, which allows better detail so do general scan first then detailed when soaked in)
Use standoff pad for flexor tendons & superficial structures (increases contact area)
Use stocks if available
US good for what kind of pathologies?Tendinopathies (acute & chronic)
Desmopathies (acute & chronic)
Joint/tendon sheath/bursa effusions (synovial structures)
Diffuse ST swellings: edema, cellulitis
Discharging tracts, suspected FB, penetrating injuries
Myositis, muscle tears, hematomas, seromas, abscesses
Soft tissue mass lesions (abscesses, hematomas, seromas)
(Vascular abnormalities: phlebitis, thrombi, abnormal flow)
(Bones: US cant penetrate but can see irregular contours in the cortices with frax; can dx frax in pelvis, which is not as accessible via radiographs; ID & localize fracture fragments; PERIOSTEAL REACTIONS BEFORE VISIBLE ON RADS; fluid accumulation (infxn) around implants)
Tendons & ligaments of the metacarpal & metatarsal regionsSDFT
DDFT
Distal check ligament/Accessory ligament of the DDFT
In general: how to dx tendon/ligament injuriesCompare affected limb with contralateral (‘normal’) limb, or assess for presence of bilateral disease
Scan both longitudinal and transverse planes!
Assess severity 4-7 days after injury & determine prognosis
Bowed tendon a.k.a. severe ST swelling over the right fore SDFT, mid-metacarpus, acute
Criteria for assessing a lesionEchogenicity
Cross-sectional area (CSA)
Fiber alignment (FAS)
Margination
Shape
Normal appearance of palmar metacarpal region:Shape: differs along length from prox to distal & medial to lateral
Echogenicity: Uniform in 1 structure across the image
Transverse images: CSA = similar between R & L limbs (& references), margination = contour of individual tendons/ligaments visible
Longitudinal image: Fiber alignment & margination
Transverse palmar metacarpal: how do you tell which side is medial?SDFT is wider on the medial side than lateral (& DDFT is opposite)
How can lesions be localized?Using measuring tape from a landmark (more reproducible)
Zones approach
Lesion localization: FL landmark?Most palmar point of accessory carpal bone
Lesion localization: HL landmark?Point of the hock
FL longitudinal image, metacarpal area: arrows are what structures? (Skin at top)
1 = SDFT
2 = DDFT
3 = Accessory ligament of DDFT (=inferior check ligament)
4 = Suspensory ligament
5 = cannon bone (palmar cortex)
Dotted space in between is connective tissue
Echogenicity: acute =Anechoic to hypoechoic
Echogenicity: subacute =Hypoechoic
Echogenicity: Chronic =Hypoechoic to hyperechoic; often heterogenous
Mineralizations are possible
(e.g. hematoma heals to seroma, then clots, then new fibers form)
What is a core lesion?Focal area of hypoechogenicity within a tendon
Generally well-defined
Visible in long & short axis images
Tendon swelling
How does chronic tendinopathy (tendonitis) look on US?Variable echogenicity (tend to be more echogenic as start to heal)
Disrupted fiber alignment pattern
No longer large, anechoic spaces
+/- tendon swelling
Tendinitis
Tendinitis (Doppler not standard protocol)
Fiber alignment: assessed how? should look like?Longitudinal images, should be parallel & homogenous
Indicates quality of scar tissue, initial severity & change over time influence prognosis
Severe acute tendinitis of large part of SDFT
Loss of regular fiber alignment, anechoic spaces, enlarged SDFT CSA
DDFT is normal!
Cross-sectional area (CSA): assessed how? tells us what?Measured in transverse images
Assess severity of lesion by quantifying CSAs of lesion & affected tendon
How is the CSA quantified?% tendon damaged = (total lesion area / total tendon area)
Mild: 0-15%
Moderate: 16-25%
Severe: >25%
Cross-sectional area (CSA): should measure where?At level of biggest extent of lesion
How to tell a tendon lesion is healing?Stable or decreasing lesional CSA
Increase in echogenicity & homogeneity of texture
Longitudinal: improvement in striated pattern/parallel fiber alignment/longer fibers appear
Absence of peritendinous fibrosis & adhesions: needs to be assessed dynamically i.e. flex & extend limb while scanning
What’s the difference between the top & bottom pics?
Top = initial scans of R HL carpus
Bottom: 7 months post-injury
Used to monitor progression of healing
(8m post: )
Rehabilitation: how often to rescan? how do findings affect the plan?Every 2-3 months and before increasing amount of exercise
Adapt exercise program to the clinical & sonographic findings; deterioratioin in sonographic appearance --> reduce (or don’t increase) exercise
Clinical improvement is often more advanced than sonographic; sonographic findings do not reflect clinical findings appropriately!
Swiss warmblood 14y, acute onset lameness, LF
Core lesion of SDFT
Transverse: Round hypoechoic area
Longitudinal: Loss of long fibers, hypoechoic zone, extensive
Dutch WB, mare, 20y, chronic lesion
Diffuse SDFT lesion
Transverse: diffuse enlargement of SDFT. MUCH LARGER THAN DDFT!
Longitudinal: heterogenous fiber arrangement; short fibers, mildly hypoechoic SDFT, swelling
What’s the difference between the left 2 & right 2 images?
Left: Core lesions (Acute- hypo, well-defined)
Right: Chronic (enlarged, heterogenous, echogenic)
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Case Examples

Question Answer
How would you describe the lesion?
SDFT lesion (26yo, RF): Hypoechoic, marginal (well-defined)
Lesion CSA approx. 30% of tendon CSA
What do these transverse & longitudinal images at 6 & 17 cm distal to the ACB tell us? Proximo-distal extent of the lesion (1/3 of metacarpal area affected); change in appearance and CSA
Lesion very superficial but may still cause pain
Describe this longitudinal, extended field of view (panorama) image (taking image as moving probe)
Shows proximo-distal extent of SDFT lesion
Hypoechoic
Loss of fibers, fiber arrangement disruped
Thickening of tendon
A 7yo Dutch WB gelding was scanned at the palmar metacarpal area. What’s happening at the red arrows in the image?
Thickened proximal annular ligament
Red circle?
Focal mineralization (hyperechoic focus with acoustic shadowing in DDFT)
Indicates chronic tendinopathy
These transverse & longitudinal scans at 2cm distal to the ACB show?
Focal hyperechoic lesion with acoustic shadowing = chronic tendonitis with dystrophic multifocal calcification
Distal DDFT (distal 1/3) where SDFT more banana shaped, wrap around DDFT
(can see with horses injected with steroids)
Blue outlining which structure?
ALDDFT (at 10cm distal to ACB); ENLARGED!
Missing spaces in between structures
What’s wrong here?
ALDDFT enlarged (transverse)
Fibers are short, ligament is thickened (longitudinal)
What is *?
Proximal SL desmopathy (FL): Lesion in origin of the suspensory ligament
HYPOECHOIC, loss of fibers, irregular fiber arrangement
SL is enlarged
(often bilateral)
How does insertional desmopathy of the branches of the SL appear?Heterogenicity of the ligament
Irregularity of proximal palmar/plantar contour of sesamoid bone
+/- mineralized foci in ligament (chronic) = dystrophic mineralization
Entheseophytes may form on insertion on proximal sesamoid bones, or small avulsions may occur
Left image is normal; right image = ?
Insertional desmopathy of the branches of the SL (separate into 2 branches at mid-lower 1/3 of metacarpal/tarsal area, insert on curved abaxial surfaces of proximal sesamoids)
Abnormal: gaps, spaces, calcification
Where is the palmar annular ligament? fxn?Proximal to metacarpo-/metatarsophalangeal joint (fetlock)
Connects palmar contours of proximal sesamoid bones and forms a retinaculum for the flexor tendons, including the tendon sheath
Annular ligament syndrome: lesions may be found where?Annular ligament
Tendon sheath
Flexor tendons
Enlargement of any of these structures will lead to narrowing of the retinaculum causing compression/tension of the other structures --> annular ligament syndrome
Annular ligament syndrome: Desmitis =Thickening, fiber disruption, irregular & ill-defined border, adhesions (annular ligament itself)
Annular ligament syndrome: Tenosynovitis =Effusion, thickening of the synovial lining, +/- adhesions (tendon sheath)
Annular ligament syndrome: Tendonitis =Enlarged CSA, abnormal echogenicity, irregular fiber pattern & surface (flexor tendons)
Annular ligament syndrome: in most cases, what can be seen with lesions to any of the 3 structures?Marked thickening (fibrosis) of subcutaneous tissue
Annular ligament syndrome
Severe ST swelling +/- incisure
Tendon sheath effusion & entheseophyte formation of proximal sesamoids
What structure between calipers? (transverse image) what about it?
Palmar annular ligament (wraps around SDFT & DDFT)
Abnormally thickened
Scar formation in subcutaneous tissue
Palmar annular ligament: normal thickness?<2mm
Normal measurement from palmar surface of SDFT to skin<5mm
What’s going on with these images?
Palmar annular ligament enlargement; distance between skin & surface of SDFT increased >5mm
(pic of palmarodistal approach to digit, longitudinal images) (scan between heel bulbs, curvilinear)
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