# Dynamic CT-based assessment of ulnar-sided wrist kinematics in healthy participants using automated 3-D analysis

## TL;DR

This study uses dynamic CT scans to assess wrist joint motion in healthy people, providing normal values for ulnar-sided wrist kinematics.

## Contribution

The study introduces an automated 3-D workflow for quantifying ulnocarpal impaction and distal radioulnar joint stability using dynamic CT.

## Key findings

- Minimal distal radioulnar joint translation was observed during wrist movements, with notable inter-individual variation.
- Ulnocarpal proximity to the triquetrum showed greater variation during motion compared to the lunate.
- Palmar–dorsal translation was larger during pronation–supination than during other wrist movements.

## Abstract

Dynamic CT imaging may help to diagnose ulnar-sided wrist pain by analysing joint motion in normal and pathological wrists. In this study an automated 3-D workflow was developed to quantify ulnocarpal impaction and distal radioulnar joint stability with dynamic CT imaging in normal wrists during motion. The aim was to establish normal values which can be used as a reference.

Dynamic CT scans were acquired from the dominant wrist of 59 healthy participants during three wrist movements: flexion–extension and radioulnar deviation were measured in 30 wrists and pronation–supination in 29. Ulnocarpal impaction was assessed with 3-D ulnar variance, reflecting proximal–distal translation of the distal radioulnar joint, and ulnocarpal proximity to the lunate and triquetrum. Distal radioulnar joint stability was evaluated using the 3-D epicentre and 3-D modified radioulnar line methods, which captured palmar–dorsal translation.

Minimal proximal–distal and palmar–dorsal translation of the distal radioulnar joint was observed across all wrist movements, although considerable inter-individual variation was notable. Three-dimensional ulnar variance did not increase during pronation. Ulnocarpal proximity to the triquetrum showed greater variation during wrist motion than to the lunate (median range 4.2–5.0 vs. 1.2–1.4 mm, respectively). Palmar–dorsal translation was larger during pronation–supination (3-D epicentre range 15.2%) than during flexion–extension and radioulnar deviation (7.7 and 9.3%, respectively).

Dynamic CT imaging shows promise for evaluating the distal radioulnar joint during wrist motion. Normal values that quantify ulnocarpal impaction and distal radioulnar joint stability found in this study may serve as a reference for future research of ulnar-sided wrist pathology.

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