🤖 AI Summary
This study addresses the limitations of conventional rigid canes, which lack axial compliance and may impair proprioception while increasing the risk of upper-limb secondary injuries, as well as spring-based canes that offer compliance at the expense of stability. The authors propose a novel cane tip module incorporating a prestressed, self-tensioned double-unit tensegrity structure to achieve synergistic optimization of nonlinear stiffness, ground conformity, and force feedback. Through axial loading tests, human gait experiments—including straight walking and turning maneuvers—and subjective user evaluations, the design demonstrates significant reductions in impact loading rate compared to rigid canes, along with improved comfort, pain relief, perceived exertion, and usability. Crucially, it avoids the stability loss and gait slowing commonly associated with spring-based alternatives.
📝 Abstract
Purpose: Six million people use crutches as mobile aids in the US. Rigid designs with no axial mobility limit sensory feedback and lead to secondary injury on the upper joints. Spring-loaded designs offer compliance but may compromise stability. We designed a biologically inspired tensegrity crutch with a compliant module aiming to achieve favorable mechanical properties. The terminal module was a pre-stressed self-tensile two-cell tensegrity structure. We compared the tensegrity crutch to commercial rigid and spring-loaded crutches in mechanical tests using axial loading, in overground straight and turning walking, and in participant experience. Methods: In human trials, healthy young adults (N=18) with no recent lower-body injury performed straight walking and turning trials at a comfortable self-selected pace. A knee blocker simulated unilateral injury of the dominant leg. After using each type of crutch, participants reported their perceived levels of effort, comfort, pain, stability, and usability. Results: Compared to the rigid design, both spring-loaded and tensegrity conditions reduced peak loading rates. The tensegrity design improved effort, comfort, pain, and usability. Spring-loaded crutches reduced perceived stability and walking speed. Conclusion: The biologically inspired tensegrity crutches were an overall improvement to existing designs. Simulations and mechanical testing suggest that nonlinear stiffness, ground-following, and force feedback are among the beneficial mechanical properties that underlie this improvement.