4 – SA MSK Flashcards
Why is proper collimation important?
- Reduces amount of scatter radiation produced
o Better radiation safety practice
o Increased image quality
x-ray beams exit the sources as a fan
- *place the centre beam with the joint(s) of interest
- *mild distortion may be present at the edge of the field of view due to divergence of the beam
- Axial skeleton: 4-5 collimate images of the spine, NOT 1 large image of the entire spine
o Positioning devices needed to prop the sternum and spine in the SAME plane in lateral views
Cortex of bone *
- Dense outer layer of compact bone
- Periosteum: outer fibrous lining of cortical bone
o serves as protective layer, also attachment surface for tendons, muscles, and ligaments - endosteum: layer that lines the medullary cavity
Medulla of bone *
- porous cancellous/spongy bone deep to cortical bone
- honeycomb cavities form by a lattice work of trabeculae
Subchondral bone *
- bone immediately adjacent to the articular cartilage
- changes often indicate problems with the cartilage (not visible radiographically)
Diaphysis of bone *
- centre portion/shaft of long bones
- can often see vascular canals in them (usually in the middle)
Metaphysis of bone *
- transition from physis of diaphysis
Physis of bone *
- Growth plate in immature animals
- Physeal scar in mature animal
- Some physes can look like fractures
Epiphysis of bone *
- Between joint space and physis
Apophysis of bone *
- Arise from a separate center of ossification, eventually fuses with the rest of bone
- A site of tendon or ligament attachment
Sesamoid bones *
- Small bone embedded with a tendon or muscle
- Acts like a pulley, provides smooth surface for tendon to glide over
What are ‘cutback zones’ ? What animals are they seen in commonly?
- In rapidly growing animals
- *flaring of metaphysis adjacent to physis
- Means there is a lot of bone turnover/growth
- Common: large breed dogs and horses
Skull
- DV preferred over VD (easier to get it straight)
- *positioning device needed to elevate the nose
Skull DV/VD view
- Equal spaces b/w the mandibular rami and zygomatic arches
Skull lateral view
- Mandibles and tympanic bullae are superimposed
When do you do ‘nose up’ lateral oblique view?
- To view temporomandibular joints
o Eliminates superimposition of the 2 TMJ
When do you do open mouth/intraoral VD view ?
- For nasal cavities
- Eliminates superimposition of mandibles with nasal cavity
When do you do rostrocaudal view?
- For frontal sinuses
*What are some key anatomic features to see on a radiograph of a canine skull?
- Nasal planum and cavity
- Body of manible
- Ramus
- Tympanic bulla
- Frontal sinus
- Cranial vault
- Zygomatic arch
- Lateral aspect of ramus
- TM joint
*What are some key features you should look at in the pharynx/larynx?
- Nasopharynx
- Soft palate
- Oropharynx
- Pharynx
- Larynx
- *know general shape of hyoid apparatus
Straight spinal radiographs: VD view
- Dorsal spinous process completely end-on
- Straight alignment of vertebral bodies
Straight spinal radiographs: lateral view
- Discrete margins of disc spaces
- Well-defined and equal-size intervertebral foramina: “little horse heads”
- Superimposed ribs and transverse processes (“Nike”)
*What are some key anatomical landmarks of the spine on radiographs?
- C6 has large transverse processes
- T11 (sometimes T10) is the anticlinal vertebra (thoracic vertebra with a completely vertical spinous process)
*What are some key radiographic features of the spine?
- No disc between C1-C2
- Diaphragmatic attachments at L3 and L4 ventral aspects
o May cause indistinct ventral borders of the vertebral bodies
*What are some key breed variations and congenital anomalies with the spine?
- Transitional vertebrae
o Asymmetric rib formation at C7/T1 or T13/L1
o Sacralization of L7, lumbarization of S1 - Hemivertebrae in brachycephalic breeds
- Caudal vertebrae can vary in number and size (brachycephalic breeds, Manx cats)
*Transitional L7 with sacralization (of the right aspect)
- Enlarged right transverse process is articulating with the ilial wing and sacrum
*What view can you use to help see the dens of C2?
- 15 degree oblique lateral
- Dens=between C1 and C2 to keep things stable
What are hemivertebrae commonly encountered in?
- Bulldogs
- Boston terriers
- Pugs
What are the most common locations of hemivertebrae?
- T7
- T8
- T12
- Occasional lumbar
*What is the result of hemivertebrae?
- Rib crowding, spinal kyphosis, scoliosis
- NOT common to have associated neurological signs
*How do you interpret the spine?
- Evaluate positioning and technique
- Number of vertebrae in each segment
- Number and symmetry of ribs
- Presence of anomalies and malformation
- Symmetry and congruity of vertebral canal
- Evaluate each vertebra, articular process joint, intervertebral disc space, intervertebral foramen
- Paraspinal soft tissues
*What are some special views you can do with the shoulder?
- Supination and pronation
o Can see different aspects of the humeral head (since rounded) - Cranioproximal-craniodistal oblique view
o Skyline the intertubercular groove (bicipital groove) which contains the biceps tendon and sheath
What are some normal findings with the shoulder?
- Occasionally see incomplete fused ossification centers at distal part of acromion and caudal glenoid cavity
- Might see axillobrachial vein and caudal circumflex humeral artery
- *Clavicles: cats
Greater tubercule (shoulder)
- Supraspinatus attachement
Intertubercular groove and supraglenoid tubercule
- Where the biceps tendon runs and then attaches
What are some standard elbow views?
- Lateral
- Craniocaudal
- Flexed lateral
o Visualize anconeal process without superimposition with the medial humeral condyle
o Use it to look for fragmentation of anconeal process
What are some common findings in the elbow?
- Supracondylar foramen in CATS
o Not dogs
o Brachial artery and median nerve course within - Supratrochlear foramen in DOGS
o Not cats - 30% animals have a supinator sesamoid bone on craniolateral aspect of radial head
*What are some standard views of the pelvis?
- Lateral
- VD frog leg
- VD with legs extended
o Preferred, but proper leg extension may need deep sedation or GA
*How can you tell if you have a straight VD pelvis view?
- Symmetric obturator foramen
- Symmetric coxofemoral joints
- Parallel femurs
*Sacroiliac joint
- Partially a fibrous/cartilaginous joint that remains RADIOLUCENT in life
*What do you use open-leg lateral for?
- *to isolate one coxofemoral joint at a time
*What do you use a flexed DP view on a hind limb for?
- to see lateral talar trochlear ridge
o if not flexed=then it is superimposed by the calcaneus
*What are stressed views of the carpus?
- Stress in all directions: flexed, extension, medial and lateral
- Write ‘stress’ on the side you are challenging
- If see more space or soft tissue=maybe a ligament is ruptured?
What are the principles of interpretation for the appendicular skeleton?
- Start to develop a systematic method of radiographic review
- *ALWAYS correlate findings bac to the history and clinical signs
- If finding does not add up to clinical signs: reevaluate, take additional views, consider another diagnostics
