Kinematics of the wrist in Kienböck's disease: a four-dimensional computed tomography study.

We studied the kinematics of 20 wrists affected by Kienböck's disease using four-dimensional computed tomography (4-D-CT) scanning. Degenerative changes progressed from the lunate facet to the scaphoid fossa at the radiocarpal articulation, then involved the midcarpal joint. Lunate fracture types included coronal (14/20), sagittal (10/20) and ligament attachment-types (8/20). Findings specific to dynamic scanning included the nutcracker phenomenon (12/20), anterior radiolunate impingement (7/20), internal instability of the lunate (6/20), ulnar styloid triquetral impingement (3/20) and dynamic proximal row instability (2/20). Ulnocarpal translocation was found in 4/20 cases. Dynamic 4-D-CT has helped us to identify a subset of pathology in Kienböck's disease on assessment of static imaging. Better understanding of these phenomena can improve our understanding of symptoms and may help direct surgical treatment.Level of evidence: IV.