Association of Lunate Facet Inclination Angle and Interfacet Angle With Kienböck Disease: A Biomechanical Study.

Purpose: Kienböck disease is a rare but severe disorder that causes avascular necrosis of the lunate, resulting in wrist pain, functional disability, and early onset arthritis. Although the exact cause remains unknown, changing biomechanical stresses on the lunate have been linked. The purpose of this study was to investigate the association between lunate facet inclination (LFI) angle, interfacet angle (IFA), scaphoid facet inclination (SFI), and stress distribution on the lunate in order to better understand biomechanical risk factors for Kienböck disease. Methods: This was an experimental study in which a 3-dimensional model was generated from CT images of a healthy wrist, and LFI, SFI, and IFA were changed by simulated osteotomies. A finite element analysis was used to determine stress on the lunate in various situations. Nine different wrist models were tested to determine changes in LFI, SFI, and IFA, as well as the loads placed on the lunate's articulations with the scaphoid, radius, triquetrum, and capitate during flexion and extension. Results: Our investigation found a strong negative correlation between LFI and lunocapitate joint stress. This suggests that a flatter LFI increases mechanical stress on the lunate. In contrast, higher LFI angles were associated with increased scapholunate stress. The findings imply that LFI could have a direct influence on stress patterns within the lunate, shading light on how these angles may contribute to disease development. Conclusions: This study shows that LFI is a significant biomechanical element affecting lunate stress in Kienböck disease. Our findings could support the inclusion of these criteria, in addition to ulnar variance and radial inclination, in diagnostic and surgical considerations for Kienböck disease therapy. Type of study/level of evidence: III.