Sonoma Orthopedics uses 3D printed bone fracture models to teach doctors new intermedullary …

Aug 5, 2016 | By Benedict

Using 3D printing equipment from Stratasys, Sonoma Orthopedics Products, Inc. is pioneering techniques for implementing intramedullary devices for ankle, wrist, and clavicle fracture repair. These bones had previously been considered too small for such procedures.

When patients require clavicle, wrist, or ankle surgery for fractures, doctors normally turn to plate fixation, a method which involves making a large incision over damaged bones and applying metal fixtures to their exterior in order to hold the fragments in place as they heal. Larger bones like the femur (thigh) or tibia (shin), on the other hand, can be treated with a different technique, something known as intramedullary fixation. This method involves placing a special pin inside the medullary canal of the bone. Less invasive, more precise, and requiring less hardware, intramedullary fixation is the more effective method of treatment, but surgeons have traditionally shied away from using it on smaller bones.

During a standard intermedullary fixation process, small incisions are made over the damaged bone, which is prepared using special instruments which enable the intermedullary pin to be properly placed. This pin is inserted into the bone cavity, putting the bone halves into alignment. Once this alignment has been achieved, small screws are drilled through the bone from the outside to hold the device in place.

Surgeons have traditionally viewed clavicle, wrist, and ankle bones as too small for intermedullary fixation, but a new kind of intermedullary fixation, developed by Sonoma Orthopedics, could change all that. Sonoma’s proprietary pin technique uses fixation grippers, located within the bone on the far end of the pin, in place of screws. These grippers thoroughly align and and immobilize the fracture to ensure perfect alignment. The secret to the company’s rapid progress, however, has been the use of 3D printed bones, created using additive manufacturing equipment from Stratasys.

Sonoma wants to train as many surgeons as possible to use its new technique, but to do so requires a subject on which to practice. Since human cadavers can only be used in very limited quantities, and since foam-based artificial bones cannot recreate certain fracture idiosyncrasies, obtaining an alternative which realistically mimics many kinds of fractures becomes imperative. “Normally we would use generic foam models or cadavers for training, but both these scenarios carry problems,” said Stephen McDaniel, Senior Project Engineer with Sonoma Orthopedics. “For example, if I want a specific fracture and a specific bone canal, it’s impossible to achieve that at the right quality using a cadaver and difficult or costly to recreate in foam when very specific details are needed.”

Fortunately for Sonoma, 3D printing represents a viable and cost-effective means of creating bone fracture models. Models can be created directly from digital data, and can be made with quality-controlled fractures that mimic important nuances in fracture details. Crucially, these 3D printed models can be made on-demand to reflect a patient’s specific fracture, but Sonoma has also collected an extensive library of CT scans which surgeons can explore to find an appropriate bone model.

Sonoma now uses 3D printing both as a low-volume production solution for training models and as a prototyping and experimenting tool: “With 3D printing, I’m able to send a model to Stratasys Direct Manufacturing and have it in-hand within days and that allows me to perform a new test so much faster,” said McDaniel. “We don’t have these kinds of prototyping capabilities in-house, so having this ability in 3 days versus the six weeks it would normally take with conventional means makes our iterative design process much faster. I’m able to simply take the CT scan and our intramedullary instrument and hold up the bone model and determine whether or not it’s the right fit.”

In order to get the most out of its additive manufacturing endeavors, Sonoma uses a range of 3D printing techniques for different items. Some fracture models are made using the Stereolithography technique, ideal for large, lightweight parts with fine feature details. Stratasys has been able to create parts up to 20 x 20 x 20 cm for Sonoma using its Stereolithography 3D printers, with one particular print proving particularly useful for the medical firm: “Our 3D printed, large-scale model features fractures expanded to show the application of the screws and to show how the fracture is repaired,” McDaniel explained. “We call the model Bigfoot. Bigfoot works like a tractor beam, attracting surgeons to our booth.”

One particular surgical case has lived on in McDaniel’s memory. A patient had suffered a clavicle fracture which had healed deformed. Even after plate fixation surgery—the common procedure for such an injury—the patient was unable to retain a full range of movements, and was therefore prevented from going about her usual business. After a CT scan, doctors found an abnormality on the patient’s affected bone, which had been the cause of the her discomfort and inability to move properly. The clavicle needed to be re-fractured and healed using a new method: Sonoma’s pioneering intermedullary fixation technique.

“We created models of the patient’s unbroken clavicle and clavicle that had broken and healed abnormally for the doctor to compare,” says McDaniel. “We then 3D printed the badly healed clavicle model with Stratasys Direct Manufacturing so that the doctor could hold it in his hand and feel and see the abnormality in a way the X-ray couldn’t reveal to him.”

Using this 3D printed model, the doctor was able to practice the pioneering technique before attempting it on the patient. Thanks to this practice, the surgery was successful, and the patient was able to get back on her feet and return to her everyday activities. Sonoma says it will continue to use 3D printing to create its surgical models, since they can be created in days instead of weeks, with no loss of quality.

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Posted in 3D Printing Application

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