Project Overview:

Problem:

Everyday, over 566,000 Americans use crutches to aid them with mobility. Not only do crutches eliminate utility of the user's hands, they can also cause nerve damage and chafing in the user's underarms. While less damaging alternatives (e.g., scooters, lower arm crutches) exist to aid with ankle and foot injuries, patients with knee injuries have limited options. I tackled this problem as my final project for a 10-week Biomedical Engineering class.

Solution:

As someone who has used crutches extensively, I was all too familiar with their key limitations. I was interested in designing an alternative that would free up the user's hands, and would provide a stable, comfortable, support system. Through an iterative process with plenty of user testing, I arrived at a design that included a waist harness and an "exoskeleton" brace for the user's leg. The brace included a platform on the end to act as the user's foot, and easily maneuverable joints to allow for a flexible range of motion. The solution was designed specifically for patients with knee injuries, given their paucity of options, but it work for patients suffering from other lower extremity issues as well.

Video of the exoskeleton crutches in use!

Design Process

State of the Art Investigation

To begin the project, I performed a thorough investigation of state of the art products. I found several alternatives to traditional crutches, but they did not work for knee injuries and often had poor reviews because of chafing, slipping, or requirement of one or both hands.

Preliminary Sketches

At first, I wanted to stick with the underarm support system, and add a harness to distribute the weight of the patient more evenly. However, after preliminary testing, I learned that the underarm supports would be uncomfortable so I transitioned to sketching up a waist-based harness with an exoskeleton support construct.

SolidWorks Model

Before constructing the full "works-like" prototype, I created a SolidWorks model of my idea so I could see how all of the pieces would function together. I realized that because of the raised nature of the exoskeleton support, a platform would be necessary on the uninjured foot to allow the user to have an even stride.

"Works Like" Prototype

The next phase of the project consisted of building a "works like" prototype that was fully functional despite its suboptimal aesthetics.

Hip Joint Components

The the hip, the prototype consisted of both a swivel joint and a hinge joint. These allowed the user to move his or her leg forward, backward, and side to side.

Knee Joint

At the knee, the exoskeleton has additional swivel and hinge joints to enhance flexibility while maintaining support.

Exoskeleton Foot

At the base of the support structure, there is a "foot" that the user walks on. It is comprised of a rubber cap on the metal rod, to prevent slipping.

Padding

Given the significant amount of pressure on the harness, I added padding to the straps. This made the device comfortable for all of the users who tested it.

Shoe for Non-Injured Foot

To align the user's feet vertically, a platform shoe would be required opposite the injured foot. To test the prototype, I made a "works like" platform shoe out of foam core and a flip flop. However if commercialized, the exoskeleton product would likely come with an attachment for the user's shoe.

Revised Model

Testers of the exoskeleton product found it to be very comfortable and supportive, but were concerned with the amount of time necessary to put on and remove the product. They were additionally concerned about the aesthetics of the prototype. So, I iterated upon the initial design to make the harness more discrete and reduce the amount of padding.

Knee Joint Flexibility

This design would also allow for bending at the knee, if the user's injury allowed for this. A mechanism would allow the structure to lock in the "straight" mode, or allow for bending by way of a simple button mechanism.

Revised Exoskeleton "Foot"

The testers also suggested enlarging the "foot" of the exoskeleton to provide a sturdier surface for walking. I designed a cross-shaped foot to extend under the user's foot and provide a stable surface.

Exoskeleton Crutches