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Updated: Feb 8, 2026
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In Vivo Electrophysiological Measurement of the Rat Ulnar Nerve with Axonal Excitability Testing
Published on: February 6, 2018
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The Effect of Axial Loading on Ulnar Variance
Kagan Ozer1, Andy F Zhu1, Breana Siljander2
1Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, Michigan.
Journal of Wrist Surgery
|June 21, 2018
Summary
Increased ulnar variance under axial loading may indicate wrist instability. A change exceeding 1mm suggests triangular fibrocartilage complex (TFCC) pathology or longitudinal instability in patients with ulnar-sided wrist pain.
Area of Science:
- Orthopedics
- Radiology
- Biomechanics
Background:
- Forearm rotation alters ulnar variance, a critical factor in wrist function.
- Daily activities necessitate axial wrist loading, yet its effect on ulnar variance is unstudied.
- Understanding ulnar variance changes under load is key for diagnosing wrist pain.
Purpose of the Study:
- To quantify changes in ulnar variance during axial wrist loading.
- To correlate these changes with wrist pain and intra-articular pathologies.
Main Methods:
- Compared neutral and axially loaded (18.1 kgf) wrist radiographs in 21 asymptomatic individuals and 24 patients with ulnar-sided wrist pain.
- Utilized magnetic resonance (MR) arthrograms for symptomatic wrists.
- Analyzed the correlation between ulnar variance change, MR findings, and physical examination.
Main Results:
- Asymptomatic individuals showed a mean ulnar variance increase of 0.4 mm under axial load.
- Patients with ulnar-sided wrist pain exhibited a greater average increase of 0.8 mm.
- An increase >1 mm in ulnar variance correlated significantly with ligament disruption, triangular fibrocartilage complex (TFCC) perforation, and foveal detachment.
Conclusions:
- A >1 mm increase in ulnar variance under axial loading is indicative of longitudinal instability.
- This significant change suggests potential triangular fibrocartilage complex (TFCC) pathology.
- Findings aid in diagnosing the source of ulnar-sided wrist pain.
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