Biomechanical evaluation of the stabilizing effect of wrist orthoses and cast treatments on an arm phantom

Abstract

Background: Standardized testing procedures are required for the objective assessment of mechanical stabilization provided by wrist braces. While early functional mobilization using orthoses is clinically favored, objective comparisons of their stabilizing effects compared to rigid casts remain scarce. The aim of this study was the biomechanical investigation and classification of the "ActiMove Manus Air", a novel ready-to-wear fracture wrist brace, compared to four established standard treatments. Methods: Five types of immobilization devices (Cast, Splint, DJO Exos Manus, ActiMove Manus Forte, Manus Air) were tested on a silicone measurement phantom with a 3D-printed hand skeleton. Stiffness was recorded in dorsal extension, palmar flexion, radial abduction, and ulnar abduction using a custom-built measurement system. Results: The circular cast application exhibited the highest overall stiffness (0.70 Nm/°), followed by the DJO Exos Manus (0.56 Nm/°). The open-design Manus Air ranked with an overall stiffness of 0.25 Nm/°, surpassing the conventional splint (0.18 Nm/°) and the ActiMove Manus Forte (0.16 Nm/°). Notably, in dorsal extension and radial abduction, the Manus Air clearly exceeded the stiffness of the splint. Conclusion: The innovative, open design of the Manus Air enables essential wound inspection and positions itself biomechanically as a highly valid alternative to conventional splints. It provides adequate stiffness required for safe early functional mobilization.