How should I report a dynamic wrist radiograph describing radial inclination and ulnar variance during radial and ulnar deviation?

Reporting Dynamic Wrist Radiographs with Radial and Ulnar Deviation

Dynamic wrist radiographs during radial and ulnar deviation should be reported by documenting the scapholunate (SL) interval width in millimeters for each position, assessing carpal alignment on lateral views, measuring ulnar variance, and comparing findings between positions to detect dynamic instability that may not be apparent on standard views.

Essential Measurements and Documentation

Scapholunate Interval Assessment

• Measure and report the SL interval in millimeters on PA views in both radial and ulnar deviation positions 1, 2.
• Normal SL interval should be ≤4 mm; widening >4 mm suggests scapholunate instability 2.
• Document any increase in SL gap width between neutral and deviated positions, as dynamic instability may show normal measurements at rest but pathologic widening with stress 3, 4.

Carpal Alignment Evaluation

• Assess and report carpal alignment and spacing abnormalities on both PA and lateral views 2.
• On lateral views, evaluate the longitudinal axes relationships between the radius, lunate, capitate, and scaphoid, as these form the basis for classifying carpal instability patterns 5.
• Document any malalignments or soft-tissue swelling visible on lateral projections 1.

Ulnar Variance Measurement

• Measure and report ulnar variance, as accurate measurement requires proper radiographic positioning 1.
• Note that arm positioning significantly affects measurements; standardized positioning with the shoulder abducted 90°, elbow flexed 90°, and forearm in neutral rotation is critical 6.

Position-Specific Reporting

Radial Deviation Views

• Document SL interval width in millimeters 4.
• Note any carpal crowding or overlap on the radial side 5.
• Assess for scaphoid flexion and potential rotatory subluxation 5.

Ulnar Deviation Views

• Measure and report SL interval width, comparing to radial deviation and neutral positions 4.
• Evaluate for increased carpal spacing on the ulnar side 2.
• Document any lunotriquetral interval abnormalities 5.

Critical Reporting Elements

Dynamic Instability Detection

• Explicitly state whether dynamic instability is present or absent based on positional changes 1, 5.
• Dynamic instability is diagnosed when routine radiographs appear normal but abnormalities emerge with positional change or stress maneuvers 5.
• Compare measurements between positions; an increase in SL interval from neutral to stress positions indicates dynamic instability 3, 4.

Standardization Requirements

• Document the exact arm positioning used during imaging, as variations significantly affect interpretation 6.
• Specify whether views are true PA projections with proper positioning (shoulder abducted 90°, elbow flexed 90°) 6.
• Note that improper positioning can simulate normal AP appearance on PA radiographs, leading to misinterpretation 6.

Common Pitfalls to Avoid

• Do not rely solely on neutral position measurements—dynamic instabilities are only apparent with provocative positioning and may be completely missed on standard views 1, 5.
• Avoid inconsistent positioning between comparison views, as even slight variations dramatically affect ulnar variance and carpal measurements 6.
• Do not overlook subtle findings on lateral views, as these are critical for identifying malalignments that may not be apparent on PA projections 1.
• Remember that static radiographs have limitations—if clinical suspicion for dynamic instability remains high despite normal stress views, consider advanced imaging such as MRI or videofluoroscopy 5, 4.