Musculoskeletal Imaging
Musculoskeletal imaging tests accurate fracture description, recognition of tumour patterns by age and location, and distinction of arthritis types. MRI interpretation of marrow and ligament injury is increasingly examined.
Fracture reporting
- State the bone, location, pattern (transverse, oblique, spiral, comminuted), displacement, angulation, rotation and intra-articular extension.
- A scaphoid fracture may be radiographically occult; snuffbox tenderness warrants immobilization and repeat imaging or MRI.
- In the elbow, a visible posterior fat pad indicates an occult joint effusion and possible fracture.
Tumours and arthritis
- Age and location narrow the differential: osteosarcoma in the metaphysis of a young patient with sunburst periosteal reaction; Ewing tumour in the diaphysis with onion-skin reaction; giant cell tumour in the epiphysis with a soap-bubble appearance.
- Osteoarthritis is asymmetric with osteophytes and subchondral sclerosis; rheumatoid arthritis is symmetric with erosions and osteopenia.
- STIR or T2 fat-suppressed sequences show marrow oedema before radiographs change.
Worked example
A 70-year-old cannot weight-bear after a fall but radiographs are normal. Occult femoral neck fracture is likely; MRI shows a T1 hypointense linear band with marrow oedema. If MRI is unavailable, CT or repeat films after 48 hours are options.
Traps
- Missing the posterior fat pad sign in a child's elbow.
- Describing a fracture without displacement or joint involvement.
- Assuming normal radiographs exclude a scaphoid or femoral neck fracture.