3 - Principles of Radiology in MSK Flashcards
What is the most commonly used medical imaging modality?
X-rays (plain radiographs)
What are the advantages and disadvantages of X-rays?
Adv: - Quick and inexpensive
Disadv: - Radiation - Poor soft tissue contrast
What is osteomyelitis?
Infection of the bone
On an X-ray how do cortical and cancellous bone differ?
Cortical bone is denser and appears more white on the image than cancellous bone
How does articular cartilage appear on an X-ray?
Articular cartilage is radiolucent so appears as a dark joint space
What is a fracture?
Complete or incomplete break in the continuity of a bone
What are the different types of fracture?
- Transverse
- Linear (sagittal)
- Oblique
- Spiral
- Greenstick
- Comminuted
What is a transverse fracture?
Break across the bone perpendicular to the long axis
What is a linear fracture?
- A fracture line that passes parallel to the long axis of the bone - AKA sagittal fracture
What is an oblique fracture?
A fracture line at an angle oblique to the long axis of the bone but still within one plane
What is a spiral fracture?
- Easily confused with an oblique fracture - The fracture line spirals round in multiple planes due to twisting of the bone
What is a compression fracture?
- Occurs in cancellous bone when an axial load compresses the bone beyond its limit - Most commonly in lumbar vertebrae
What is a greenstick fracture?
- Incomplete fractures where the bone bends and cracks on one side instead of breaking into pieces - Usually in children < 10yrs
What is an epiphyseal separation fracture?
- The fracture line extends through and unfused growth plate - The epiphysis separates from the metaphysis
- Most commonly slipped capital femoral epiphysis (SCFE) of the femur
What two fracture types occur specifically in children?
- Greenstick fractures - Epiphyseal separation fractures
The ossification centre in the diaphysis is the ………… ossification centre
Primary
The ossification centres in the epiphyses are the ………… ossification centres
Secondary
How do the epiphyseal growth plates appear on an X-ray?
- Less mineralised than surrounding bone - Less radio-opaque - Easily seen on X-rays as dark lines
Give examples of factors that influence the proliferation and transformation of cells in the epiphyseal growth plate.
- Growth hormone promotes cellular proliferation - Thyroid hormone deficiency and excess corticosteroids result in a reduction in cell division (growth retardation)
How is a child’s bone age determined?
- Estimates the maturity of the musculoskeletal system by looking at the degree of ossification of the carpal bones and epiphyseal growth plates - Take an X-ray and compare to a standard atlas of bone development - Bone age given in years
What does a significant difference between a child’s bone age and chronological age suggest?
Pathologies such as: - Precocious (early) or delayed (late) puberty - Growth hormone deficiency - Hypo- or hyperthyroidism - Malnutrition
What are the four key stages of fracture repair?
- Haematoma formation
- Soft (fibrocartilaginous) callus formation
- Hard callus formation
- Remodelling
Fracture healing occurs broadly in three phases. What happens in the first (inflammatory) phase?
Hours - days - Haematoma formation - Tissue death - Inflammation and cellular proliferation
Fracture healing occurs broadly in three phases. What happens in the second (reparative) phase?
Days - weeks - Angiogenesis/granulation/procallus formation - Soft callus formation - Hard callus formation
Fracture healing occurs broadly in three phases. What happens in the third (remodelling) phase?
Months - years - Gradual replacement of hard callus with mature bone - Fracture line becomes obscured (radiographic union)
In CT scanning, tissue density is measured in what units?
Hounsfield units
How does MRI work?
- Uses a magnetic field to line up protons in hydrogen atoms - Radio frequency pulses are applies to deflect the protons - Protons realign when the pulse is terminated and emit a signal as they do so (different tissues realign at different rates) - Signal is detected and used to make a 3D image
Which of MRI and CT is better for: - Soft tissue imaging (e.g. malignancy or prolapsed disc)? - Bone architecture imaging (e.g. complex fractures)?
- Soft tissue imaging - MRI - Bone architecture imaging - CT
How do T1 and T2 weighted MRI images differ?
T1 - fat is white, water (fluid) is dark T2 - fat and fluid are bright
What is a STIR sequence in MRI?
- Fluid-sensitive sequence - Signal from fat is suppressed (appears dark), fluid appears bright - Useful for detecting oedema
What is the most common contrast medium used in MRI? How is it given?
Gadolinium - Injected percutaneously into a joint or administered intravenously
What is ultrasonography?
- Use of high-frequency sound waves to produce images - Sound waves made by a transducer and travel through the patient, tissues reflect the waves back and are analysed to create an image
How is nuclear medicine used to image bone?
- Radioisotope-labelled, biologically active drugs given to the patient
- Marker of metabolically active bone (e.g. metastatic disease or healing fractures)
