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• >1,000,000 people in the US suffer from neurological disorders 1, limiting muscle strength and compromising independent living
• Maneuvering a standard power wheelchair joysticks is difficult with reduced hand dexterity
• With a starting price of $40, the frequent replacement of joysticks due to loss or damage is expensive
• Joystick replacement may take weeks, rendering the patient completely immobile in their chair for an extended time period
There is no existing low-cost, rapidly producible, and customizable joystick that allows patients of limited hand dexterity to operate their power wheelchairs. We formed a partnership with Inglis
House, a residential home to three hundred individuals with neurological disorders, to develop a manufacturing process has been designed to enable the occupational therapists (OT) to 3D print customizable joysticks inhouse.
The novel joystick design encourages the function hand position, a clinically established safe resting hand position. This position is driven dimensionally by the metacarpalphalangeal joint resting at a 45° angle 2 , which would allow a wheelchair user to rest their hand over a spherical shaped joystick and maneuver using the extrinsic flexor and extensor muscles of the three primary fingers 2 .
Additionally, the spherical joystick design is the most reproducible and easily manufactured as it can be customized based only on a few dimensions. The
relieving the thenar muscles and median nerve, further reducing pain and discomfort 2 .
specific resident based on his or her anthropometric measurements. This algorithm assumes that the metacarpalphalangeal joint is 45° to keep the hand in
calculated as 1.5x thumb width to allow room for the thumb to roll.
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Action
Finger extension 3+
Hand extension
Shoulder extension 2+
Elbow flexion
Grade
2+
3+
The clinical Manual Muscle
Test will be used by OT to evaluate the strength of the patient’s fingers, hand and shoulder extension, and elbow flexion.
The test grades muscle group resistance to an applied force from 0, no resistance, to 5, normal resistance 5 . To the left is the expected grade needed to use our joystick effectively.
The OT then quantifies a patient’s hand dexterity, using a Range of
Motion Test, to determine if he or she can safely maintain the functional hand position.
To customize our design the following measurements are taken:
- Length from DIP to PIP
- Length from PIP to MCP
- Index finger thickness
- Thumb finger thickness
- Thumb finger length
In the CAD generation phase, the OT inputs the recorded anthropometric measurements into our GUI tool, which calculates the customized dimensions of the joystick design on the back end and outputs a CAD rendering of the customized joystick. This tool has been developed in MATLAB and CADLab, and it interfaces well with SolidWorks, the CAD program that renders the final CAD file for printing in
using a MakerBot Replicator Desktop 3D printer.
In the delivery phase, the OT prints the final customized joystick. The joystick design includes 10-32 threading on the base, which allows a nylon screw to be threaded into it. This screw pushes against the metal post found on the arm of a standard power wheelchair to hold the joystick safely in place. This serves as a safety mechanism to ensure the joystick will not unintentionally be removed from the wheelchair such as during a sharp turning or muscle spasm. The use of a screw as a locking mechanism allows for the joystick to still be easily unscrewed from the wheelchair for cleaning or replacement. It also allows the user to adjust the height of the joystick by changing where the screw locks it into place.
To verify the patient can safely and effectively use their new, customized joystick, the clinical Wheelchair Skills Test will be performed. This test grades wheelchair patients on a series of sub-tests, which include moving forward, backward, or turning
180° in place 7 . Patients will take the test using the commercial joystick and the new 3D printed joystick. A comfort survey will be used to obtain patient feedback as to the utility and comfort of the new manufactured 3D printed joysticks.
• Our process is a same-day, inexpensive method for joystick replacement
• Printing of joystick take less than five hours
• Product cost per joystick = $1, a 40x reduction in cost
• Joystick encourages the functional hand position, reducing strain
• Manufacturing process is currently being implemented at Inglis House
• Joystick design is currently being tested by 10 Inglis House residents
$40-$60
$1-2
We would like to acknowledge the staff and the residents of Inglis House for their support, especially Dawn Waller, Robin Trent, Danielle Paffet, Charles Sammertino, Dr. Gina Disipio, DO and Katy Stauffer; our Senior Design advisors Drs. Karen Moxon, Wan Shih, and Sriram
Balasubramanian of Drexel University; Emily Meltzer of Thomas Jefferson University, and
Ricardo Solarzano of BioBots.
1 D. Hitz. et al . How common are the “common” neurologic disorders?. Neurology . 68(5): 326-
37. 2007 Jan 30.
2 Brunnstrom's Clinical Kinesiology , 6th ed, Brunstromm, 2011.
3 Fast Facts on US Hospitals. Americal Hospital Association. (2012).
4 P. Basiliere, Forecast: 3D Printers Worldwide, 2013. Gartner, Inc . 2013 Sep 27.
5 Manual Muscle Testing Procedures. National Institute of Environmental Health Sciences, 2014.
6 E. Mulligan, Range of Motion Measurements. Orthopedic Physical Therapy Educational
Programs and Services , 2015.
7 R. Kirby, et al . Wheelchair Skills Test (WST) Version 4.2 Manual . Halifax, Nova Scotia:
Dalhousie University. 2013. 8 Park-Lee, E. et al.
Residential care facilities: A key sector in the spectrum of long-term care providers in the United States, National Center for Health
Statistics , (78), 2011.