Designing a transitional NuFlex element for orthopedic walker boots for better recovery of lower leg injuries

Abstract

Over one hundred thousand lower leg injuries are reported every year in the United States. During the acute stage of recovery from such injuries, the injured leg must be immobilized to allow healing and prevent re-injury of the fragile injured site. However, after this acute stage, it is more beneficial to allow some motion of the ankle in order to gradually allow ligaments to regain flexibility and range of motion. Most treatment methods for more severe lower leg injuries, such as casts and walker boots, completely immobilize the leg and do not allow for a gradual transition into more motion over time. Some walker boots, called Range of Motion (ROM) walker boots, do allow for a transition between an immobilized state and a mobile state, but utilize simple hinges which constrains the ankle to unnatural motion and adds extra bulk to the boot.

The goal of my thesis is to develop a mechanism for orthopedic walker boots which allows the boot to gradually transition between an immobilized state and a mobile state. Furthermore, the mobile state must allow for natural plantar flexion and dorsiflexion motion while providing adequate support against ankle inversion or eversion. Finally, I wanted to create a less bulky design than current boots. In order to accomplish these goal, I developed a.) a flexible hinge system whose axis of rotation can adjust to match the patients' natural axis of rotation, b.) a mechanism which enables the user to control the range of motion allowed at different stages of healing, and c.) an immobilizing cover which locks the boot into an immobilized state. These three components together make up my NuFlex design. Based on static stress simulation analyses, the NuFlex successfully protects the ankle against inversion and eversion, and also successfully immobilizes the ankle in the immobilized state. However, the flexible hinge system and range control mechanism require further development and user testing in order to validate their efficacy.