Changes in ulnar variance in relation to forearm rotation and grip

Area of Science:

• Orthopedics
• Radiology
• Human Anatomy

Background:

• Ulnar variance, the relative length of the ulna and radius, is crucial in wrist biomechanics.
• Understanding normal ulnar variance is essential for diagnosing and managing wrist pathologies.

Purpose of the Study:

• To determine the normal range of ulnar variance in healthy adults.
• To assess the impact of different wrist positions and grip conditions on ulnar variance.
• To establish a normative database for clinical research and diagnosis.

Main Methods:

• Radiographic analysis of 120 healthy volunteers' wrists.
• Acquisition of images in various positions (pronation, supination, neutral) under static and dynamic (maximum grip) conditions.
• Measurement of ulnar variance (UV) and calculation of maximum dynamic change (UVmax - UVmin).

Main Results:

• Mean normal ulnar variance in neutral rotation was +0.74 ± 1.46 mm, significantly lower in males than females.
• Negative ulnar variance was observed in 26% of participants.
• Maximum ulnar variance occurred during pronated grip (UVmax +1.52 ± 1.56 mm), and minimum variance during relaxed supination (UVmin +0.19 ± 1.43 mm).
• Mean maximum dynamic change in ulnar variance was 1.34 ± 0.53 mm.

Conclusions:

• Established normative values for ulnar variance across different conditions.
• Highlighted the significant dynamic changes in ulnar variance with grip and position.
• The generated database is valuable for diagnosing radio-ulnar length discrepancies and guiding clinical research.