Danek prototype lab. Instead, they come to see their ideas for new surgical instruments become working prototypes with the help of FDM (fused deposition modelling) rapid prototyping. With locations in Memphis, Tennessee and Rossi, France, Sofamor Danek is the world leader in spinal and cranial medical technologies.
“We often see one or two VIP surgeons per day,” says design engineer Richard Franks. “They come in with a problem to solve in the morning. They explain their need to an engineer, who models a solution on ProEngineer and then makes a rapid prototype. Often by the next morning we’ll have a prototype in their hands. Sometimes we even deliver the same day. Having the FDM machine in-house really makes it easy for us to design products.”
Sofamor Danek engineers recently designed a ratcheting counter-torque instrument that surgeons use to fasten set-screws to a corrective implant on a patient’s vertebrae. After the screws are fixed in place, the tool shears off the screw heads at a pre-set torque level. The existing method required surgeons to use separate tools, working them in opposing directions, using both hands. The result was often a violent impulse occurring at the moment of shearing, which the surgeons were keen to avoid.
“The device we developed combines the two existing tools into a single unit,” says Mr Franks. “As the surgeon squeezes two handle pieces together, the ratchet tightens the screws.” The engineers produced a working polycarbonate ratchet strong enough to withstand testing on stainless steel set-screws and durable enough to survive an autoclave.
Senior engineering manager Troy McDonald adds: “Surgeons are really rough on these prototypes while trying them out, so we have got to have tough material. FDM gave us the strength and durability we needed. It also turned out to be an important tool for us, as the benefits of functional prototypes extend to communication too. Being able to use the rapid prototypes has really cut down on miscommunication.”
After sending the counter-torque ratchet out to three hospitals, Sofamor Danek learned that the tool design could be improved by rotating its handle 90 degrees - information it might not have learned without working prototypes.
The financial advantages of including FDM technology in the prototype lab are evident too. Designs can be refined and savings mount as more prototypes are made in-house.
“We have several divisions and each one has its own dedicated engineering staff that comes to our RP lab with modelling requests. Almost everything that comes off the FDM machine is for functional evaluation saving the company a lot of money. The cost of sending out work versus doing it in-house is easy to capture and we can justify owning the FDM system by reducing that cost alone. But the intangibles, like timing issues, communication, and the value-added services are where we see the greatest benefits.”