Imaging lameness Flashcards
What are some indications for orthopaedic imaging?
Skeletal/joint pain Acute/chronic lameness Fracture confirmation/characterisation Swellings Monitor/screening for inherited musculoskeletal disease Metabolic bone disease Evaluating systemic disease
What is geometric distortion?
Distorted imaging on radiographs
Occurs if structure towards the edge of collimated area OR not parallel to plate
How can geometric distortion be prevented?
Careful positioning - keep away from edge of collimated area, tight collimation, keep parallel
What are the limitations of radiography?
Artefacts - e.g. Mack lines
Poor soft tissue contrast
2D image of 3D structures - structures superimposed
What are Mack lines?
Lines of opacity
Not a real lesion (artefact)
Due to geometric distortion
What is serial radiography?
Multiple radiographs over a period of time
To monitor disease progression or confirm a diagnosis
What are the 5 Roentgen signs?
Number Size Shape Location Opacity
What amount of mineral loss (%) is required to see a reduction in bone opacity on a radiograph?
30-60%
Also takes minimum of 7 days to be apparent
Consider may be artefact
(Focal loss easier to detect)
What may cause a generalised reduction in bone opacity on a radiograph?
Artefact
Nutritional issue - secondary to hyperparathyroidism
Why does hyperparathyroidism cause a reduced bone density?
Increased parathyroid hormone
Causes calcium to be released from bone stores
What may cause a focal area of decreased bone density?
Lysis - due to neoplasia or osteomyelitis
What are the 3 types (patterns) of focal bone lysis?
Geographic
Moth-eaten
Permeative
(From least to most aggressive)
What does monostotic and polyostotic mean?
Monostotic = affecting 1 bone Polyostotic = affecting more than 1 bone
How can skeletal lesions be categorised?
Focal or generalised
Symmetrical or asymmetrical
Monostotic or polyostotic
Is cartilage visible on radiographs?
No - (soft tissue opacity)
Give examples of subchondral defects
Osteochondrosis Aseptic necrosis Septic arthritis Erosive arthritis Soft tissue neoplasia Trauma (avulsions) Osseous cyst-like lesions Severe osteoarthritis
What is an osteophyte?
Abnormal bony projection around joints
Bone spur
What is an enthesophyte?
Abnormal bony projections at the attachment site of a ligament
Joint effusions may not be distinguishable from periarticular swellings - except for which joint?
Stifle - adjacent fat provides contrast
What may be seen radiographically with osteoarthritis?
Periarticular new bone at predictable sites
Soft tissue swelling/effusion
Subchondral sclerosis
Narrowed joint space (if weight bearing or v severe)
What can cause mineralised bodies on radiographs?
Accessory centres of ossification
Tendinopathies (incidental)
Osteochondral fragments (pathological)
What are the predilection sites for osteochondrosis?
Caudal aspect of humeral head
Medial part of humeral condyle
Lateral femoral condyle
Medial trochlear ridge of talus
What are the predilection sites for osteosarcoma?
Proximal humerus
Distal radius/ulna
Distal femur
Proximal tibia
What frequency probe should be used for musculoskeletal ultrasound imaging?
Linear (high frequency) probe
