New adaptive finger brace could improve recovery for joint injuries

A friend's struggles with arthritis and the finger braces used to manage it inspired research by a Carnegie Mellon University student that could make it easier for patients to follow rehabilitation plans, speed up recovery times and help people manage chronic conditions.

Yuyu Lin, a Ph.D. student in the School of Computer Science's Human-Computer Interaction Institute (HCII), worked alongside her friend during an internship and noticed she had to remove the finger braces she wore to relieve arthritis in her knuckles when she used a computer. She couldn't bend her fingers with the braces, but she needed the braces to treat her condition. 

Lin wondered if she could make a finger brace that could easily toggle between stiff and flexible - without removal- to help people facing similar challenges.

With her colleagues in the Interactive Structures Lab (ISL), Lin did just that. The team developed a fully customizable finger brace that can, with the push or flex of a finger, easily switch from stiff to flexible. Along with its versatility, the brace can be 3D printed and requires no assembly.

For this work, we were trying to think from the perspective of the patient, and how to get them to wear this brace and complete their rehabilitation routine more easily." 

Yuyu Lin, Ph.D. student in the School of Computer Science's Human-Computer Interaction Institute (HCII)

Researchers designed the brace as two rigid pieces connected by an elastic band. The band can easily be released when a patient pushes down on the brace and curls or bends their finger to a certain point, allowing easy movement of the finger. When the patient extends their finger, pushing it up, the elastic band snaps back into place through a similar process and the finger becomes immobilized. Think of a snap bracelet - it's rigid until it's bent to a certain point, then it curls around the wrist.

Researchers worked with medical professionals and identified the tendons on the second knuckle of the hand where the brace could be useful. This area, known as the proximal interphalangeal joint, can be challenging to treat because post-injury stiffness can occur without adequate early mobilization.

Current finger orthoses are often static, leaving the digit immobile, and doctors usually ask that the patient remove the brace for rehabilitation exercises. Patients struggle to maintain the balance between immobility and movement, and researchers realized they needed a simple, pain-free solution to this problem. The answer was allowing the finger to move without removing the brace.

"We wanted to understand how we could help people, and what patients needed right now," said Alexandra Ion, an assistant professor in the HCII and director of the Interactive Structures Lab. "We wanted to add our expertise to build this new, unexpected thing."

The brace is customizable as well as flexible. In this initial work, the ISL researchers envision customization through software, allowing patients to easily generate a custom brace and either 3D print it themselves or have the completed device sent to them, ready to wear.

The patient needs to collect certain dimensions to customize their brace: their finger dimensions, which can be measured with a ruler; finger strength, which is measured with a force gauge; and their finger's extension angle, which can be measured with a protractor. Using these metrics, a computational design tool simulates a version of the brace. This step determines how much force, or torque, is required to safely switch the device from stiff to flexible. Based on the simulation, the tool generates a 3D design, allowing the patient to tweak it before printing.

Along with Ion and Lin, the CMU research team included Anoushka Naidu, a senior in the Computer Science Department; Dian Zhu, a senior majoring in mathematical sciences; Kenneth Yu, a junior in the HCII and School of Design; Deon Harper, a student at Pennsylvania State University who was part of the HCII's Summer Research Experience for Undergraduates program; Eni Halilaj, an associate professor in the Mechanical Engineering Department who directs CMU's Musculoskeletal Biomechanics Lab; and Douglas Weber, the Akhtar and Bhutta Professor of Mechanical Engineering. Deborah Kenney from Stanford University and Adam Popchak and Mark Baratz from the University of Pittsburgh Medical Center were also part of the team.

Lin plans to continue developing braces and inventing adaptive devices that can be easily and comfortably worn for more users with limited mobility.

The National Science Foundation and CMU's Center for Machine Learning and Health funded this research, which will be presented at the Association for Computing Machinery's Symposium on User Interface Software and Technology conference.