New “digit” design to help people who have lost fingers – Post Bulletin


ROCHESTER – Sometimes seeing a problem repeated over and over again will inspire a solution.

In the summer of 2018, five local clients arrived at the Limb Lab prosthetic clinic in Rochester after accidentally cutting their thumbs. The accidents all happened within two months.

The Limb Lab team is known for starting all conversations with the trademark question, “What do you want to do?” The responses from these customers highlighted a need in the industry.

These clients all wanted to be able to continue working the way they did before they lost their inches. One is a breeder and another delivers mail for the Post Office. Another customer who is missing a thumb works on an assembly line for a manufacturer.

This meant that prosthetists at Limb Lamb had to find adjustable “thumbs” that clients could wear to enable them to grasp objects as well as other actions.

“I started looking at existing products for these guys and there aren’t many. There was really only one workable solution,” said Limb Lab founder and prosthetist Brandon Sampson.

This solution was a friction-based prosthesis with screws to tighten it in place.

“As soon as these big guys started catching something, it would move and go wild. So they were tightening the friction to hold it, but you couldn’t reposition it,” he said. “So it was pointless and frustrating for those guys.”

Sampson discussed the issue with Limb Lab co-founder Marty Frana, who is the company’s CEO. Frana works on the business side of the operation.

Limb Lab co-founder Brandon Sampson is building on the patent he and co-founder Marty Frana recently obtained for their innovative design of a “universal digit” for clients who have lost a finger.

Jeff Kiger / Release Bulletin

“I love bouncing ideas off him (Frana), because he sees it from such a different perspective than mine. He’s a farm boy from Iowa. I’m a farm boy from Minnesota On a farm, you figure out how to fix problems with baling wire and duct tape,” Sampson said.

They determined that a successful prosthesis would require a mechanism that easily locks in several different places and also rotates in different places. After discussing the plan with an engineer, simple 3D printed prototypes were created.

Sampson has a briefcase full of experiment parts. Eventually, they settled on a design that can actually be used as a replacement for any finger.

A client can use another hand or their teeth to lock it in place. In addition to having a full range of normal movement for a finger, their creation can also lock backwards into a position that no natural finger or thumb should go. It can provide a hook for another way to carry something.

The next step was to submit an application to the US Patent and Trademark Office to patent the design of their “universal cipher”. Sampson and Frana filed this permit on August 6, 2018.

The couple received approval for their patent – their first – on April 26, 2022. They join a large crowd of Rochester-area inventors with patents.

Sampson and his team have not been idle while awaiting patent approval. They had 100 numbers machined out of aluminum. He said 48 clients, some of whom worked in prosthetic clinics, are now using these early versions of the lock cipher. The aluminum version of the numbers are around $750 each.

Limb Lab also started embedding the number in silicone and painting it to make it less noticeable. The silicone “skins” are also customizable. A customer picking up small parts from an assembly line has a skin with an added ridge to provide a sort of “shovel” to aid in the process.

Now, Sampson is talking to major prosthetic manufacturers about incorporating the universal digit into their product lines.

“There’s definitely a lot of interest, and that’s the cool thing. It worked 48 times,” he said.

The Limb Lab has many ideas for variations or related products. Other applications are in preparation at the patent office.

Meanwhile, Limb Lab continues to work with customers. Sampson and Frana founded the company in downtown Rochester in 2018 with one vision and three employees.

There are now 40 Limb Lab employees working in six locations in four states. The original Rochester lab has expanded twice. Together with Brian Childs, another Limb Lab partner and Chief Growth Officer, Sampson plans to open two more offices in 2022.

Jeff Kiger tracks business activity in Rochester and southeastern Minnesota every day in “Heard on the Street.” Send tips to

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