A Biomechanical Analysis of the Distal Radioulnar Joint Ballottement Test Using Stress CT.

Area of Science:

• Orthopedic Surgery
• Radiology
• Biomechanics

Background:

• Diagnosing distal radioulnar joint (DRUJ) instability is challenging with current clinical maneuvers.
• Existing computed tomography (CT) methods lack reliability for DRUJ instability assessment without applied stress.
• Simultaneous evaluation of stress CT and clinical stress tests for DRUJ instability has not been previously studied.

Purpose of the Study:

• To compare the efficacy of stress CT and clinical stress maneuvers in identifying distal radioulnar joint (DRUJ) instability.
• To evaluate DRUJ stability in both stable and unstable wrist conditions using advanced imaging and biomechanical testing.

Main Methods:

• Development of an arthrometer to assess clinical stress tests of the DRUJ across various forearm rotations.
• Application of standardized volar and dorsal loads to simulate clinical stress on the DRUJ.
• Acquisition of CT images under both stressed and unstressed conditions, with subsequent sectioning of the triangular fibrocartilage complex (TFCC) to induce instability.

Main Results:

• The arthrometer detected significant differences in TFCC integrity in the supinated position, though a portion of measured translation was due to clamp rotation.
• Unstressed CT analysis, using the radioulnar ratio, failed to differentiate between stable and unstable DRUJ states.
• Stress CT analysis of ulnar translation demonstrated significant differences in DRUJ stability between intact and sectioned TFCC states.

Conclusions:

• Clinical examination maneuvers and arthrometers are influenced by rotational components, limiting direct assessment of bony translation.
• Stress CT provides a more accurate quantification of underlying bony translation for evaluating DRUJ instability.
• Unstressed CT imaging is insufficient for identifying DRUJ instability.