Development and Evaluation of a Quick Release Posterior Strut Ankle Foot Orthosis

Abstract

Ankle foot orthosis (AFO) stiffness affects ankle range of motion but can also provide energy storage and return to improve mobility. To perform multiple activities during the day, a person may want to change their AFO stiffness to meet their activity’s demand. Carrying multiple AFO and changing the AFO is inconvenient and could discourage users from engaging in multiple activities. This thesis developed a new quick-release mechanism (QRM) that allows users to easily change posterior strut elements to change AFO stiffness. The QRM attaches to the AFO and requires no tools to operate. The new QRM includes a quick-release key, weight-bearing pin, receptacle anchor, and immobilization pin. A prototype was modelled with SolidWorks and simulated with SolidWorks Simulation. The QRM was designed to have no mechanical failure during intense activities such as downhill walking and running. Unlike a solid screw connection, the QRM needed an additional part to eliminate unsecured motion related to clearance between the quick release key and receptacle anchor. Mechanical test results and measurement data demonstrated no deformation on each part after mechanical testing. User testing revealed that, although the quick release mechanism can be locked or unlocked rapidly, the person’s posture when operating can facilitate strut swapping. A learning effect occurred by repeated practice. The Quick Release AFO (QRAFO) prototype verified the manufacturing feasibility of the QRAFO design. Overall, the novel quick release AFO improved strut swapping time without sacrificing device strength.