Dynamic wrist imaging using four-dimensional CT: current concepts, clinical applications, and future perspectives.

Carpal instability is fundamentally a dynamic disorder that may not be detected using conventional static imaging modalities such as radiography, CT, and MRI. This diagnostic limitation may delay diagnosis and treatment, potentially leading to progressive instability and degenerative changes. Four-dimensional CT enables dynamic, in vivo visualisation and quantitative analysis of wrist kinematics by acquiring sequential volumetric datasets during active motion. This allows identification of abnormal motion patterns, including altered intercarpal coordination and subluxations, which cannot be detected using static imaging. Clinical applications include evaluation of scapholunate instability, distal radioulnar joint instability, midcarpal instability, and altered carpal kinematics in conditions such as Kienböck disease. Four-dimensional CT may also be valuable for preoperative planning and postoperative assessment by enabling objective evaluation of treatment-related changes in wrist motion. Comparison with the contralateral wrist provides an internal physiological reference and may improve diagnostic confidence by distinguishing pathological motion from normal anatomical variation. Four-dimensional CT complements conventional imaging and arthroscopy by providing functional information on wrist biomechanics. It should be used selectively when dynamic instability is suspected and conventional imaging is inconclusive. Ongoing advances in automated analysis, dose optimisation, and protocol standardisation are expected to further improve clinical applicability and support broader integration into clinical practice.