Normal Range and Influencing Factors of Distal Radioulnar Joint Translation: A Descriptive Study

Distal radioulnar joint (DRUJ) instability is commonly assessed clinically via physical examination, such as a ballottement test, which evaluates palmar-dorsal translation of the radius relative to the ulna. However, the normal physiological range of translation and the factors influencing it remain poorly defined, limiting the test's diagnostic precision. This study aimed to quantify the normal range of DRUJ translation and identify its associated factors in a healthy population.

Healthy adult participants were recruited between January 1, 2025, and April 30, 2025. Data on occupation, gender, age, height, weight, handedness, wrist circumference, forearm length, and grip strength were recorded. A custom-designed device was used to measure the palmar, dorsal, and combined DRUJ translations in forearm pronation, supination, and neutral positions. Univariate and multivariate analyses were performed to identify factors influencing translation.

The mean (±SD) combined DRUJ translation was 11.9 ± 4.2 mm in pronation, 12.4 ± 3.9 mm in supination, and 13.3 ± 4.6 mm in the neutral position. Significant side-to-side differences were observed for all translations in pronation and for both palmar and dorsal translations in the neutral position. No significant side-to-side difference was found in supination. Compared to pronation and supination, combined and palmar translations were significantly greater in the neutral position. Conversely, dorsal translation was greatest in supination. Multivariate analysis revealed that combined DRUJ translation in supination was significantly influenced by grip strength, forearm length, weight, and age.

Our findings establish reference values for DRUJ translation and demonstrate that it is influenced by forearm position and multiple factors. To improve the clinical utility of the ballottement test, we recommend performing it in forearm supination while comparing both limbs. Specifically, combined DRUJ translation with forearm supinated is significantly affected by grip strength, forearm length, weight, and age.