After a gun accident resulted in the loss of the middle finger on his right hand, Colin Macduff immediately knew that he would create his own custom prosthesis.

“Three hours after surgery, I woke my wife up at 3 in the morning, and I told her that I was going to make a finger out of bicycle parts,” Macduff, the president of RCM Enterprise LLC, told O&P Business News. “She thought that I was crazy.”

But as soon as he was physically able, Macduff, who was an architectural drafter before his accident, retired to his garage where he spent approximately 8 hours creating a prosthetic finger for himself out of aluminum handlebars from a bicycle. Now, several prototypes later, Macduff has turned his self-made finger into a successful business.

“I had no idea that this was going to turn into a 24/7 job,” Macduff said. “I didn’t know it was going to be this big.”

Bio-mechanical Prosthetic Finger

Although the first prototype was functional, Macduff soon learned that a metal finger was not ideal.



Colin Macduff


“Especially in the Pacific Northwest winter, the cold weather would transfer to the metal,” Macduff said. “And it caused excruciating pain to the amputation.”

After some further development, Macduff began fabricating the device, which is called the Bio-mechanical Prosthetic Finger, with plastic polymer. The prosthesis is worn on the residual finger like a ring, and the plastic material is extremely durable, as well as lightweight and functional.

“It’s like a roll cage for your finger,” Macduff said. “It’s designed to take a beating and protect the amputation.”

However, the tip of the finger is soft and users can easily pick up something delicate, like a sheet of paper. The Bio-mechanical prosthetic finger is designed to be worn 24 hours a day, and the maintenance is as simple as washing your hands.




Cold weather prompted a change in design from metal to plastic polymer.

Images: Colin Macduff 


“It is actually dishwasher safe,” Macduff joked. “But you are not going to want to take it off for that long, so just wash it like you would regularly wash your hands.”

The design of the device provides the user with sensory feedback, so he or she can feel how much weight is being applied to the finger.

“So you can actually pinch something and feel how much pressure you are putting down on it,” MacDuff said. “But at the same time, it’s not hurting your amputation.”

And the prosthetic device has functioning joints that enable to the user to pick up a glass, write and wield a power tool.

“You can go out and chop wood or go swimming or anything you’ve done before,” Macduff said. “But you don’t have the painful side effect of jamming your amputation into everything and anything.”

In addition to its functional benefits, the Bio-mechanical Prosthetic Finger also provides potential long-term health benefits because stress on the adjacent fingers is reduced.


Multiple devices can be worn as necessary.




“If I wasn’t wearing it, I would be putting lateral stress on the adjacent joints,” Macduff said. “And I would be jamming my finger into everything.”

Multiple devices also can be worn on the same hand if the user has lost more than one finger.

“The acuity tests have proven that it is beneficial,” Macduff said. “And if someone is wearing multiple [devices], it is exponentially better.”


The Bio-mechanical Prosthetic Finger is patent-protected, and Macduff now markets the device to other finger amputees. Each prosthesis is custom-made, and the fitting process is simple.

“Everything is drawn up in CAD,” Macduff said. “I take my original drawing and can manipulate it around the patient’s amputation.”

Interested patients send Macduff a photocopy of both of their hands next to a ruler for scale. Once the request is approved by insurance, which it typically is, Macduff sends a custom ring-sizing kit to attain the correct measurements.

“We have to see what kind of scarring there is and how much functionality there is from the [proximal interphalangeal] PIP joint,” Macduff said. “There are so many variables in there, but since it is designed around the amputation, we can design it.”

Currently, the fitting and fabrication, which is done through additive manufacturing, takes approximately 2 months to 3 months to complete. RCM Enterprise is in the final stages of streamlining the manufacturing process, and is working on securing a European patent and developing a full-finger prosthesis that would attach to the metacarpal joint.

“I tell my patients that I am not going to be able to give their old finger back to them, but I can give them a tool,” Macduff said. “And once you learn how to use that tool, in time you may forget about your accident.” — by Megan Gilbride


Disclosure: Macduff is the president of RCM Enterprise, which fabricates the Bio-mechanical Prosthetic Finger.



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