Outrigger Splint (Outrigger Finger Extension Assist)

Outrigger Splint (Outrigger Finger Extension Assist)

●Background

In the summer of 2025, I contracted Guillain-Barré Syndrome, and the extensor muscles in my left hand's middle, ring, and little fingers became very weak

This made it difficult to lift my fingers sufficiently, and typing on a PC keyboard was particularly problematic
Typing requires not only the force to press keys but also the "hovering" strength to hold fingers in the air Since my extensor muscles weakened, normal typing became difficult

Therefore, I designed a dorsal outrigger splint (finger extension assist device) tailored to my hand and produced it with 3D printing

This device assists finger extension using outrigger arms and tension springs installed on the back of the hand
The outrigger section adopts a truss structure to maintain strength while reducing weight

By using this device, I was able to blind type again
This model is a publication of that personal prototype device

●Important Disclaimer

⚠️This model is not a medical device

This device has not been designed or verified by medical professionals and is published as a personal prototype device
It is not intended as a substitute for medical treatment or rehabilitation

By downloading and using this model, you understand the following:

・Use this model at your own risk
・We cannot be held responsible for discomfort, injury, or worsening of existing conditions due to its use
・If you experience pain, discomfort, or symptoms, please consult a medical professional

●Purpose

This device is designed for the following purposes:

・To assist finger extension
・To hold fingers in the air (hovering assistance)
・To assist with light tasks such as keyboard typing

It is designed as a personal assistive device for a specific condition and may not be suitable for everyone
Additionally, this 3D model is designed for the left hand

●Size Information

Finger ring inner diameter

[For index, middle, ring fingers] 17.5mm/18.0mm
[For little finger] 16.0mm/16.5mm

Reference (in my case)

Index finger: 17.5mm
Middle finger: 18.0mm
Ring finger: 18.0mm
Little finger: 16.5mm

Spring mounting hole diameter 3mm

Hand size and finger thickness vary among individuals, so please scale as necessary for use

●Items required for production

・3D printed parts
・Adhesive suitable for the filament material
・20mm wide hook and loop fastener band
・Spring mounting screws M3x8mm polycarbonate pan head screws 8 pieces
・Tension springs↓
　　　(Reference specifications)
　　　[For index, middle, ring fingers]
　　　　Wire diameter: 0.29mm
　　　　Outer diameter: 4mm
　　　　Length: 25mm
　　　[For little finger]
　　　　Wire diameter: 0.26mm
　　　　Outer diameter: 2.4mm
　　　　Length: 20mm

●Assembly Method

1 Insert the four arm sections into the slit holes of the base part
2 Secure the arms with adhesive to fix them firmly
3 Select a ring that fits your finger size
4 Connect the ring and the spring with an M3 screw
5 Secure the opposite end of the spring to the hole at the tip of the arm with an M3 screw
6 Attach the hook and loop fastener band to the slits in the base part

●How to Use

1 Wear the main body on the back (dorsal side) of your hand
2 Tighten the hook and loop fastener band to secure it to your hand
3 Insert your four fingers into their respective rings
4 Finger extension is assisted by the tension of the springs

⚠️Precautions during use

Do not forcibly pull your fingers
Do not tighten it so strongly that it impedes blood circulation
If you experience pain or discomfort, discontinue use

●Summary

This device was created as a personal prototype to assist with daily tasks even when finger extension is weakened
I hope it will be helpful for those facing similar challenges or interested in rehabilitation and assistive device creation