Ultrasonography Of The Equine Distal Limb Flashcards
What four things does ultrasound provide information on?
–Structures involved
–Degree and extent of injury
–Acute or chronic injury
–Healing / response to treatment
What is the examination technique of using ultrasound?
- Quiet, dark environmen with suitable facilities
- Allow sufficient time for an examination
- Sedation / analgesics for painful lesions
- Clip and scrub affected area
- Use plenty of coupling gel
- Move limb during musculoskeletal examination (dynamic studies)
What is the depth of imaging for SDFT and DDFT?
2-4cm
What is the depth of suspensory ligament?
4-6cm
What angle does the ultrasound probe need to be to the area imaged?
90 degrees
What 2 views do we need with an ultrasound?
Transverse and longitudinal
What images are needed from lateral and medial aspect for suspensory branches?
Transverse images
Name 12 of the normal structures proximal to fetlock seen on ultrasound (15)
- Superficial digital flexor tendon (SDFT)
- Deep digital flexor tendon (DDFT)
- Accessory ligament of DDFT / check ligament (ALDDFT)
- Suspensory ligament (SL)
- Digital extensor tendon
- Intersesamoidean ligaments
- Proximal annular ligament
- Tendon sheath
- Cannon bone
- Splint bones
- Sesamoid bones
- Fetlock joint
- Fetlock collateral ligaments
- Skin and subcut. tissues
- Neurovascular structures
What is the origin of flexor tendons?
Caudomedial humerus
Where does the SDFT insert?
P1 and P2
Where does the DDFT insert?
P3
Where do suspensory ligament arise from?
Palmar carpal ligament and metacarpal bone
Where do the suspensory ligaments insert?
On sesamoid bone (exensor branches)
What are the regions and technique to ultrasound the metacarpus?
7 zones from accessory carpal bone to ergot (1A, 1B, 2A, 2B, 3A, 3B, 3C)
What are the regions and techniues to ultrasound the metatarsus?
•9 zones from base of hock to ergot (1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B, 4C)
Look at this
Name 10 normal structures distal to fetlock (12)
- SDFT and DDFT
- Extensor branches of SL
- Tendon sheath
- Digital extensor tendon
- Distal annular ligament
- P1, P2 and P3
- Pastern joint
- Coffin joint
- Collateral ligaments
- Navicular bone, impar ligament and bursa
- Collateral cartilages
- Skin and subcut. tissue
Look at this
What changes can be seen with disease?
- Position, size, shape, structure and echogenicity
- Changes in position
- Changes in cross sectional area
- Changes in margins
- Changes in fibre pattern
- Changes in echogenicity
What do you describe lesions in terms of?
–Location: which structures are affected, distance from anatomical landmarks (accessory carpal bone or base of hock, where is the lesion
–Size: measure CSA, extent of defect and compare to other limb or known normals
–Shape: margins and outline
–Changes in echogenicity
–Changes in normal architecture
–Anomalies
What are tendon fibres held together by?
Endootenon
What are fasicles held together by?
Paratenon
What is a whole tendon surrounded by?
Epitenon
What does this show?
How do you grade tendon changes in echogenicity?
Type 1: slightly less echogenic than normal
Type 2: half echogenic and half anechoic
Type 3: mostly anechoic
Type 4: completely anechoic
What is fibre pattern/allignment socring?
0: >75% fibres aligned parallel to target path
1: 50-75% fibres aligned parallel to target path
2: 25-50% fibres aligned parallel to target path
3: <25% fibres aligned parallel to target path
What is this?
SDFT
What is the normal appearance of SDFT?
–Homogenic and echogenic.
–Slightly less echogenic than DDFT (TGC).
–Normal CSA for UK and US thoroughbreds and other breeds
–Training can cause a 10% increase in CSA and mild decrease in echogenicity
What is this?
DDFT
What is the normal appearance of DDFT on ultrasound?
–Homogenic and echogenic
–Increased echogenicity cf SDFT
–Hypoechoic region in hindlimb at insertion of ALDDFT
–Bilobed appearance in pastern
–Normal CSA for UK and US thoroughbreds and other breeds
What is the normal appearance of the ALDDFT?
Homoegneous and echogenic
What thickness do we measure with ALDDFT?
Dorsopalmar or lateromedial
What is this?
Suspensry ligament
What is the normal appearance of the suspensory ligament?
–Heterogeneous - muscle, connective tissue, fat + ligament fibres
–Can contain hypoechoic areas check contralateral limb
–Branches are homogenous and echogenic
–Normal CSA published for body and branch.
What is a 3.5.MHz transducer good for?
Echocardiography and ultrasonography of late pregnancy in large / medium sized dogs
What is a 5MHz transducer used for?
Abdominal ultrasound in large dogs, abdominal and cardiac ultrasound in medium and small dogs, pelvic and pregnancy ultrasound in all dogs
What is a 7.5 MHz transducer used for?
Abdominal and cardiac ultrasound in small dogs and cats, pelvic and pregnancy ultrasound in medium and small dogs and cats, cervical ultrasound in large dogs, puppies and kittens
What is a 10MHz transducer used for?
Ultrasound of cervical structures (salivary glands, thyroid), superficial structures (skin, mammary glands) and musculoskeletal
Name 2 advantages of a linear array transducer (3)
- High near field resolution
- Parallel beams
- No moving parts
Name the disadvantage of using a linear array transducer
Large contact area
Name 3 uses of linear array transducers (4)
- Muscles
- Mammary glands
- Joints
- Tendons
What is the purpose of the stand off pads?
Increase distance between transducer and superficial structures
How does an ultrasound machine work?
•When sound strikes a boundary (between two tissues of different acoustic impedance) the beam is split into four
–Transmitted beam
–Reflected beam
–Refracted beam
–Scattered beam
•This reflected beam is received by the ultrasound machine and converted into an image
What are the structures labelled a, b, c and d?
a – superficial digital flexor tendon
b – deep digital flexor tendon
c – straight sesamoidean ligament
d – oblique sesamoidean ligament
What are the structures labelled a, b, c and d?
a – superficial digital flexor tendon
b – deep digital flexor tendon
c – accessory ligament of deep digital flexor tendon (check ligament)
d – suspensory (interosseus) ligament
List the criteria used to assess an ultrasound image (6)
- Position, size, shape, structure and echogenicity
- Changes in position
- Changes in cross sectional area
- Changes in margins
- Changes in fibre pattern
- Changes in echogenicity
List the different features of a lesion that you should describe when interpreting an ultrasound (6)
- Location: which structures are affected, distance from anatomical landmarks (accessory carpal bone or base of hock, where is the lesion
- Size: measure CSA, extent of defect and compare to other limb or known normals
- Shape: margins and outline
- Changes in echogenicity
- Changes in normal architecture
- Anomalies
Identify the different structures in this ultrasound image of the proximal palmar metcarpal region
Describe the abnormalities in the ALDDFT in this image
Increased in size
Irregular outline, assymmetrical shape
Heterogenous pattern
Loss of fibre pattern
This was a chronic healing lesion in this horse, so lacks the hypoechoic regions you would associate with acute lesions, but remains grossly enlarged with variable healing
What is the structure and function of tendons?
- Tendons connect muscle to bone
- They originate from the connective tissue of muscle
- They insert in bones
- They have great tensile strength
- They function to store elastic energy
- Tendons occur at the origin and insertion of muscles
- ORIGIN: Muscles originate from bone by tendons (proximal region)
- INSERTION: Muscles are attached to bone by tendons (distal region)
Label these blue boxes
What is apoenurosis?
a sheet of pearly white fibrous tissue which takes the place of a tendon in sheet-like muscles having a wide area of attachment.
How are the tendons fibres structured?
- String or steel cable consists of several strands of material interwoven
- Tendon structure uses a similar principle except the fibres remain in parallel (to allow elastic movement)
What is the origin and insertion of tendons?
- Tendons occur at the origin and insertion of muscles
- ORIGIN: Muscles originate from bone by tendons (proximal region)
- INSERTION: Muscles are attached to bone by tendons (distal region)
Label these arrows
Label this
What are tendons and ligaments designed to give?
Maximum biomechanical strength
Label 1, 2 and 3 of the tendon
Endotenon (1) holds fibres together to form fasicles
Peritenon (2) holds fasicles together
Epitenon (3) surrounds whole tendon
Label this picture
Label this image of transition from tendon to bone
but don’t label 5 or 6 cause there isn’t an answer and i cbfa to figure it out for myself
- Tendon
- Fibrous cartilage
- Mineralised cartilage
- Bone
Label the blue squares as part of an image from tendon transitioning to bone
Give 2 examples of where ligaments can stabilise and support axial skeleton
What is tendon composed of? How is it organised?
- Tendon is composed of connective tissue
- Type of connective tissue is collagen fibrils
- Collagen fibrils are organised into fibres
- Fibres are arranged in parallel bundles
•Hierarchical organisation
into primary bundles (fibres) & secondary bundles (fasicles)
What is the structure of tendon maintained by?
•Structure of tendon (primary and secondary bundles) is maintained by loose connective tissue
- Endotenon (endotendineum)
- Peritenon (peritendineum)
- Epitenon (epitendineum)
Label the blue squares
What do ligaments do?
•Ligaments link bone to bone
- Tendons link muscle to bone
- Do not have same capacity for elastic storage of energy
- Key component of joints providing stability
- Collateral ligaments present in most joints
What are the functions of the patellar ligaments of equine stifle?
Function is to lock the stifle and maintain the limb in a weight-bearing position with the minimum muscular effort
What is the function of the cruciate ligaments of stifle?
Resist cranio-caudal movement of stifle. Injury is most common cause of lameness in the dog
Which ligaments function is to lock the stifle and maintain the limb in a weight-bearing position with the minimum muscular effort?
Patellar ligaments of equine stifle:
Label this image with regards to tendon sheaths and bursae
Label the blue squares in this image
Which ligaments function is to resist cranio-caudal movement of stifle. Injury is most common cause of lameness in the dog?
Cruciate ligaments of stifle:
FIll in the question mark with the anatomical structure that should be there based on the anatomy
Flushing the flexor tendon sheath in a horse with an infection following a pastern injury
What is the innervation and vasculature for tendons and ligaments? What does this mean?
- Tendons and ligaments have low metabolic function
- Poorly vascularised and innervated
- This affects their ability to heal
What are some ways you can get failure of tendons and ligaments?
- Biomechanically very strong
- Failure often within the muscle or within the bone at the site of attachment
- Fibres arranged in parallel bundles
- When some fibres are damaged, remainder take the additional load / strain
- Tendons and ligaments poorly innervated
- Damage may be significant before pain and lameness is evident
- Tendons and ligaments have poor vascular supply
- Ability to heal is poor
- Tendons and ligaments can be damaged by excessive pressure and friction
- Where they run over joints, bony prominences or where there a marked change in direction
Fill in the blue squares with regards to the tendon bursae
How many bursae are under the nuchal ligament?
3
What is happening in this radiograph?
Radiograph of contrast being injected in navicular bursa
Tendons and ligaments are biomechanically very strong. What does this mean in terms of failure?
Failure often within the muscle or within the bone at the site of attachment
What are these images of?
Acquired bursae in cattle
Tendon and ligaments fibres are arranged in parallel bundles. What does this mean with regards to failure?
When some fibres are damaged, remainder take the additional load / strain
Tendons and ligaments are poorly innervated. What does this mean with regards to failure?
Damage may be significant before pain and lameness is evident
Tendons and ligaments have poor vascular supply. What does this mean with regards to failure?
Ability to heal is poor
Tendons and ligaments can be damaged by excessive pressure and friction. What does this mean with regards to failure?
–Where they run over joints, bony prominences or where there a marked change in direction
This picture is an ultrasound of the superficial digital flexor tendon in a horse. Which is normal and which shows pathology? What pathology?
Left - normal
Right - tendonitis
What are tendon sheaths and bursae?
Tendon sheaths and bursae are fluid-filled structures that protect tendons at pressure / friction points
- Tendon sheaths wrap completely around tendon
- Bursae are present on only one side (like a cushion)
A tendon sheath is a layer of synovial membrane around a tendon. It permits thetendon to stretch and not adhere to the surrounding fascia
Where do tendon sheaths occur?
What is their function?
Occur at the point of friction
Occur wherever tendons cross high motion joints
Surorund and protect tendon and enable it to glide smoothly
Common digital synovial sheaths:
- Where do they reach from?
- What do they enclose?
- Where is swelling of this sheath visible?
Common digital synovial sheaths
- Reaches from the distal cannon to the middle phalanx
- Palmar: 9 pouches
- Enclosed the superficial and deep flexor tendons
- Swelling of this sheath is most easily visible proximal and palmar to the fetlock joint (also know as windgalls)
What are tendon bursae?
Where are they present?
- Fluid-filled sacs that facilitate sliding
- Synovial structures with a synovial membrane and synovial fluid
- Present at major pressure points
- Between bones and muscle, tendons or ligaments, or between skin and bones, muscle, tendons or ligaments
What is bursae existence dependent on?
What can trauma lead to?
- Their existence is inconstant depending on mechanical challenges, age, body condition
- Trauma can lead to ‘acquired` bursae
What are the bursae of the equine hindlimb?
- Patella bursae
- Calcaneal bursae
- Navicular bursa
What is the difference between a tendon and a ligament?
- Tendons originate from the connective tissue of muscle and insert in bones
- They function to store elastic energy
- Ligaments link bone to bone
- Do not have same capacity for elastic storage of energy
- Key component of joints providing stability
What is the difference between a tendon sheath and a bursa?
- Tendon sheaths wrap completely around tendon
- Bursae are present on only one side
