Designing Better Bone

As a mechanical engineer for 13 years at the Musculoskeletal Transplant Foundation (MTF)—one of the nation’s leading tissue banks—Manuel Olivos helped design and machine bone from deceased donors to fit each recipient and make tissue transplants more successful.

Olivos, an innovative engineer, developed and helped patent a new method to design and assemble grafts that combine both of the two types of bone that we possess: compact, solid bone, also known as cortical bone, and spongy bone segments known as cancellous bone. To assemble the bone segments, he would custom-cut their ends, then he joined them together with a dovetail joint and interlocking structure that woodworkers use to join pieces of wood to make drawers or log cabins. Then he’d use a pin he developed to lock the bone pieces together, strengthening the implant further.

What Olivos never suspected was that he himself would be in the market for donated bone.

Bone Grafting

For ten years, Olivos had suffered from excessive headaches and neck pain. After painkillers stopped working, his orthopedist recommended a spinal fusion.

Olivos’s surgeon had already grafted bone donated by MTF into other patients. As it turned out, the bone he selected for Olivos’s surgery was the very type of allograft for which Olivos had designed and received a patent.

“What made this allograft revolutionary was our ability to combine both cortical and cancellous bone.We were able to take the machining of bone to a whole new level,” Olivos said.

Within six months of receiving the operation, Olivos was pain-free.

MTF was founded by surgeons in 1987 to provide better tissue for transplantation. Since then, the organization has recovered tissue from more than 115,000 donors and distributed more than 7.5 million grafts for transplantations.

In the early days, surgeons had used saws and other hand tools to machine donated bone into the right shape for transplantation, and MTF staff used a three-axis hand-milling machine for this purpose, said Ray Ferrara, the organization’s director of engineering for operations.

Over the last 20 years, they’ve been using engineering software to custom-design and machine the donated bone. Since 1996, they’ve used Solid Edge, the 3-D engineering design and simulation software from Siemens PLM, starting with Solid Edge v4. MTF’s work represents an unusual application of this 3D CAD software, which is typically used to design parts made of inert materials like metal, ceramics, and plastic.

Bone Shaping

Shaping bone for transplants is different. First, a surgeon requests donated bone for a specific purpose, for example, bone for spinal disc surgery like Olivos’s fusion. MTF constructs a 3-D image of the bone needed to make a patient whole. After the surgeon and the MTF team discuss and tweak the model using the software, a design is locked in. Then they machine the bone using a custom-built CNC machine.

With spinal spacers like the one Olivos received, the fit of the spacer between the vertebrae must be geometrically precise. To achieve that precision, the MTF team tweaks bone-structure models in the software to precision before machining them, Ferrara said.

When they started custom-machining the bone, they were able to produce much more bone for transplantation. “Volumes really started to come up,” Ferrara said.

“The bone is a donated gift, and we don’t have much raw material to play around with,” Ferrara said. “The whole goal is to use as much of it as possible.”

To conserve the bone, the engineering they do is essential, Ferrara said. “Most people are fascinated that there is even engineering involved with tissue donation.”

Meredith Stettner is a writer based in Jersey City, NJ.