Wrist & Hand Imaging: Systematic Interpretation

Radius-lunate-capitate should be co-linear

• Lunate sits in lunate fossa
• Capitate articulates with lunate
• Draw lines through long axes

Scapholunate angle: 30-60° normal Capitolunate angle: Less than 30° (nearly co-linear)

DISI (Dorsal Intercalated Segment Instability):

• SL angle greater than 70°
• Lunate tilts dorsally
• Associated with SL ligament injury

VISI (Volar Intercalated Segment Instability):

• SL angle less than 30°
• Lunate tilts volarly
• Associated with LT ligament injury

Boxer fracture: 5th MC neck

• Assess apex dorsal angulation
• Acceptable angulation varies by digit

Bennett fracture: 1st MC base

• Intra-articular fracture-dislocation
• Small volar fragment stays with trapezium
• Shaft displaces dorsally/radially

Rolando fracture: Comminuted Bennett

Mallet finger: Avulsion dorsal P3 base

• May be bony or tendinous
• Greater than 30% articular = consider fixation

Volar plate avulsion: Volar P2/P3 base

• Hyperextension injury

Gamekeeper/Skier thumb: UCL injury

• Stress views may show instability
• MRI for soft tissue assessment

The scaphoid is the most commonly fractured carpal bone, accounting for roughly 79% of carpal fractures, and predominantly affects young active adults (peak in males aged 15-30). Initial radiographs miss an estimated 15-20% of true fractures, which is the central driver of every imaging pathway in this topic.

Distal radius fractures are among the most common fractures worldwide, with a bimodal distribution (young high-energy and older osteoporotic/fragility). Metacarpal and phalangeal fractures together represent a large share of all hand injuries presenting to emergency departments globally, making the PA/oblique/lateral hand series a high-volume, high-yield study.

Whether to obtain immediate MRI, immediate CT, early MRI at day 3, or delayed radiographs at 2 weeks remains debated. Decision-analysis and a single-centre randomised trial favour immediate cross-sectional imaging because it shortens unnecessary immobilisation and lost productivity, but access, cost and out-of-hours availability still drive real-world pathways. Many centres run a hybrid pathway: clinical risk stratification, then MRI for high-suspicion cases.

CT has excellent specificity but can miss non-displaced trabecular fractures and bone bruising that MRI detects. MRI has higher sensitivity but may over-call bone oedema as a "fracture", potentially leading to overtreatment. The Cochrane analysis found CT and MRI broadly comparable, with bone scintigraphy most sensitive but least specific — so test choice depends on whether your priority is avoiding a missed fracture or avoiding overtreatment.

Predynamic and dynamic scapholunate instability can have entirely normal static radiographs. Diagnosis then depends on stress (clenched-fist) views, fluoroscopy, MR arthrography or arthroscopy, the latter still regarded as the reference standard for partial ligament tears. There is no universally agreed non-invasive test, and inter-observer reliability of SL gap and angle measurements is only moderate.

Conventional MRI has variable sensitivity for peripheral TFCC tears and partial intrinsic ligament tears. MR arthrography improves accuracy but is invasive, and wrist arthroscopy remains the diagnostic gold standard. The cut-off between a degenerative (often asymptomatic) Palmer Class 2 TFCC change and a clinically relevant tear is a recurring source of over-diagnosis.