The Capitate-to-Axis-of-Radius Distance (CARD): A New Radiographic Measurement for Wrist and Carpal Alignment in the...

Area of Science:

• Orthopedic surgery
• Radiology
• Wrist biomechanics

Background:

• Sagittal radiocarpal alignment is crucial for wrist function.
• Existing radiographic methods for assessing sagittal alignment have limitations.

Purpose of the Study:

• To establish the reliability of the capitate-to-axis-of-radius distance (CARD) for evaluating sagittal radiocarpal alignment.
• To validate the CARD by comparing measurements in normal wrists versus those with distal radial fractures (DRFs) and rheumatoid arthritis (RA).

Main Methods:

• The CARD was defined as the perpendicular distance from the capitate head center to the radius axis.
• Inter- and intraobserver reliability was assessed.
• CARD values were compared between normal wrists (n=25) and wrists with DRFs (n=25) or RA (n=25).

Main Results:

• The CARD demonstrated excellent inter- and intraobserver reliability.
• Significant differences in mean CARD values were observed between normal (2.2 ± 2.5 mm), DRF (15.7 ± 6.5 mm), and RA (0.2 ± 4.4 mm) wrists.
• Strong correlations were found between CARD and deformity severity in DRFs (r=0.8) and RA (r=-0.7).

Conclusions:

• The CARD is a reproducible and user-friendly index for assessing sagittal carpal alignment.
• The CARD is a valuable tool for quantifying sagittal plane deformities in DRFs and RA.
• Normal wrist CARD values serve as a useful reference for unilateral wrist conditions.