RheumatologyTier 2Topic

Musculoskeletal radiology tests - CT

Role

CT provides detailed bony/structural imaging of joints and bone - complementary to MRI (better for soft tissue/marrow) and plain X-ray (faster, cheaper, first-line) - particularly useful for complex fracture characterisation, bony erosion detail, and pre-surgical planning
Used selectively in rheumatology/orthopaedics when bony anatomy needs to be defined in more detail than X-ray provides, or when MRI is contraindicated/unavailable

Strengths

Superior spatial resolution for cortical bone detail compared with MRI - useful for characterising complex fractures (particularly intra-articular), subtle erosions in inflammatory arthritis not well seen on X-ray, and pre-surgical 3D planning (e.g. complex joint reconstruction)

Dual-energy CT and limits

Dual-energy CT extends conventional CT with urate crystal detection capability, a specific rheumatological application beyond standard structural bone imaging
CT is generally not the first-line modality for early inflammatory arthritis (MRI and ultrasound are more sensitive for synovitis/early erosive change) but has a role once bony detail needs clarifying or for specific fracture/surgical planning questions

Radiation and surgical planning

Radiation dose is a relevant consideration, particularly for serial imaging or in younger patients, favouring MRI/ultrasound where equivalent information can be obtained without radiation
CT findings directly inform surgical planning discussions when complex bony reconstruction is being considered

Indications

Complex intra-articular fractures, pre-surgical joint reconstruction planning, subtle bony erosion characterisation

Key point

CT's radiation burden and lower soft-tissue sensitivity mean it plays a supporting, more targeted role in musculoskeletal imaging compared with MRI/ultrasound for most routine inflammatory arthritis assessment, reserved for specific bony/structural questions

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