Streamlining the Arm Sling

BLUF - As the project lead for senior capstone I developed the design architecture for an arm sling with DFA and characterized its immobilization capabilities

After my senior design capstone professor connected my team with an orthopedic surgeon at UCLA Ronald Reagan Hospital, we met to discuss patient needs and clinician concerns. Our primary objective was to make the sling that patients suffering from rotator cuff injury would effectively immobilize their arm consistently wear during recovery.

Designing the Arm Sling

In order to make an arm sling that fits a patient, I modeled all parts with surfaces. Each panel is designed to fit together modularly, enabling a custom-fit solution for a patient's unique anatomy

Validating the Arm Sling

After 3D printing all the components and installing the foam cushioning, we talked with our professor who pointed us to a vision-based validation tehcnique. He offered us to use his ViCon system to capture the motion of a group member wearing the sling and performing various locomotive and functional tasks. As ViCon systems are precise to sub-millimeter levels, we followed his advice and sampled marker locations in space to establish the motion of the torso, arm, and sling. Sampling at 100Hz ensured we had ample data to confidently determine the location and alignment of the patient's body and accessory.

My teammate wears the sling with reflective gray markers forming triangles attached

Markers visualized in space on the ViCon GUI while my teammate performs tasks

Using vector geometry, I programmed a script in Python that accepts the .csv files generated by the ViCon system and converts them to angle displacements between the torso, arm, and sling. The algorithm is as follows:

Locate intervals where at least three markers are visible for per part
Average those intervals to obtain positions before, during, and after an action
Define a plane for each part using a cross product
Compute angles between each pair of planes using a dot product

Results

Our sling reliably keeps the same position for the arm when performing ambulatory and functional tasks