Imaging in lameness Flashcards
List the indications for imaging in orthopaedics
- Acute or chronic lameness
- Skeletal or joint pain
- Fracture confirmation/characterisation
- Swelling centred on bones/joints
- Monitoring/screening for inherited musculoskeletal disease
- Metabolic bone disease
- Evaluation of systemic disease
Describe the steps in the diagnostic process of orthopaedic disease
- DDx list formulated on basis of history and clinical examination (other tests)
- Imaging test performed
- Differential list narrowed based on results
- Further tests (imaging?) performed to narrow new differential list
- Diagnosis and treatment plan
What are the 4 main considerations of the imaging examination
Determine the correct region to image
Select the most appropriate modality/modalities
Perform technically competent examination
Accurately interpret results of study
How can you determine the correct region to image?
Thorough general clinical examination and history
Comprehensive orthopaedic exam
Examination under GA/sedation?
How can you select the most appropriate imaging modality - which modalities are available?
Radiographs initially?
Ultrasound
CT or MRI
Scintigraphy
Which features of the imaging exam will ensure the image is technically competent
- Correct region radiographed
- Well-positioned, reproducible views
- Adequate number/orthogonal (at least 2 views)
- Free from significant artefacts
- Awareness of limitations of radiography
What is geometric distortion and when does it occur?
- Occurs if structure is towards edge of collimated area or not truly parallel to film/detector
- GA or sedation and careful positioning required
- Tight collimation can help
What are the limitations of radiography to be aware of for orthopaedic disease?
Oblique projections can create apparent artefactual lesions
Poor soft tissue contrast resolution
Describe the uses/purpose of serial radiography
Monitor progression of disease
Show diseases radiographically occult in their early stages
Assess dynamic component of disease
Can be useful if diagnosis is uncertain
What are the key points of interpreting radiographs which are fundamental to all modalities?
- Deviation from normal appearance recognised
- Lesion(s) accurately described in systematic fashion
- Pertinent aspects of lesion(s) appreciated from their description
- Formulation of differential diagnoses (with integration of other information from signalment etc)
Describe normal variations seen on radiographs
Normal variations in age, breed, and species need to be considered
What are the 5 Rontgen signs?
Number
Size
Shape (including margins)
Location
Opacity
You should consider that a lesions could also be one of which 3 things?
- Artefact of poor positioning or technique
- Feature/variant of normal anatomy
- Composite shadow of superimposed normal structures
Which areas of bones can be assessed through imaging?
- Alignment, shape, length
- Periosteal reaction/cortical lysis/defects
- Endosteal/medullary changes
- Physes
Which areas of joints can be assessed through imaging?
Swelling/effusion
Subchondral bone
Periarticular changes
What are the possible causes of reduced soft tissue size?
- Atrophy (focal)
- Lameness (chronic)
- Neurogenic
- Fibrosis/scarring - Weight loss (general)
What are the possible causes of increased soft tissue size?
Focal
- Trauma
- Abscess/seroma
- Granuloma
- Neoplasia
Diffuse
- Oedema
- Cellulitis/vasculitis
- Diffuse neoplasia
Name the 3 areas of long bones
Epiphysis
Diaphysis
Metaphysis
Describe the anatomy of long bones on the cut section
Cortex and medulla
Outside of the cortex = periosteum
Inside of the cortex = endosteum
Describe reduction in bone opacity and the possible indications of this
- Maybe artefactual: Poor exposure
- 30-60% mineral loss required to be appreciated radiographically
- Minimum 7 days to be apparent
- Focal loss easier to detect
What are the causes of generalised and focal reductions in bone opacity?
Generalised - nutritional secondary HPTH)
Localised/focal (lysis) - neoplasia, occasionally osteomyelitis
Name and describe the appearance of the 3 categories of focal bone loss
Geographical lysis = unified area which looks relatively homogenous where there is a reduction in opacity
Moth-eaten = coalescing holes through the bone
Permeative = lots of very tiny holes in the bone – bone is eaten away in a particular area
Which type of focal bone loss is least and most aggressive
Geographical = least
Moth-eaten
Permeative = most
Name the 7 types of periosteal bone reaction from least to most aggressive
Smooth - inactive/benign
Rough
Brush border
Palisading
Spicular
Sunburst
Amorphous - active/aggressive
Describe the appearance of amorphous periosteal reaction
Diffuse shapeless mineralisation extending into the surrounding soft tissues
Is a long transition zone a sign of a benign or aggressive lesion?
Aggressive
Describe some features of aggressive bone lesions
Long zone of transition
Active periosteal reaction
Destruction of the cortical integrity
Soft tissue swelling
How are distributions of skeletal lesions categorised?
Monostotic (single bone involvement)
Polyostotic (multiple bones)
Focal
Generalised
Symmetrical
Asymmetrical
Describe the key points to consider for joint radiography
- High quality radiographs essential, Centred of the joint of interest
- High prevalence of incidental findings
- Careful orthopaedic exam critical: Eliminate incidental findings e.g. in older animals
- Stressed radiographs and oblique projections useful in some cases
What are the 5 main features to assess on joint radiography?
- Soft tissue swelling
- Joint “space” width
- Subchondral bone opacity
- Osteophyte/enthesophytes
- Periarticular mineralisation
What is subchondral bone?
Bone just underneath the joint surface
Joint effusions may not be distinguishable from …?
Periarticular swelling
How is joint effusion assessed differently in the stifle?
Stifle a special case (adjacent fat provides contrast) – can see if there is joint swelling vs swelling around the joint
Fat pad is normally a triangular shape, this can become compressed when there is abnormal pathology
How is cartilage visualised on radiography?
Cartilage is not visible as soft tissue opacity
Can use contrast to visualise or MRI
List the causes of subchondral bone defects (8 options)
- Osteochondrosis
- Aseptic necrosis (femoral head)
- Septic arthritis
- Erosive arthritis (carpus/tarsus)
- Soft tissue neoplasia
- Trauma (avulsions)
- Osseous cyst like lesions
- Osteoarthritis (only very severe)
Describe the radiographic changes seen in osteoarthritis of the stifle
- Soft tissue swelling/effusion
- Periarticular new bone (osteophytes/enthesophytes) at predictable sites
- Subchondral sclerosis
- Narrowed joint space (if weight-bearing/very severe)
Osteophytes are associated with the ….?
Enthesophytes are associated with the ….?
Joint capsule
Ligament
What are the mineralised bodies, where do they occur?
Commonly seen
Normal (occurring at predictable sites)
- Sesamoids (some inconsistent)
- Accessory centres of ossification
Incidental (tendinopathies?)
Pathological (osteochondral fragments)
Name the VITAMIND terms used to form DDx lists
Vascular
Infectious/Immune-mediated
Traumatic, toxic
Anomalous
Metabolic
Idiopathic
Neoplastic, nutritional
Degenerative/Drug induced
Describe the 4 predilection sites for osteochondrosis
- Caudal aspect humeral head
- Medial part humeral condyle
- Lateral femoral condyle
- Medial trochlear ridge talus
Describe the 4 predilection sites for osteosarcomas
Proximal humerus
Distal radius/ulna
Distal femur
Proximal tibia
Describe the uses/limitations of ultrasound in orthopaedics
- Use linear (high frequency) probe
- Muscles, tendons and ligaments clearly visualised
- Bone surface is depicted well
- Imaging deep to surface not possible if cortex intact
Which key structures can be identified on US of the shoulder?
Biceps tendon and sheath (craniomedial)
Supraspinatus and infraspinatus muscles/tendons (lateral/craniolateral)
Name the parts that make up the calcaneal tendon
- Gastrocnemius
- Superficial digital flexor
- Conjoined/common calcaneal (biceps femoris, semitendinosus and gracilis)
