3D Printed Bone Models Provide True-To-Life Training For Surgeons

Traditionally, when clavicle, wrist or ankle fractures require surgery, doctors rely on plate fixation. Plate fixation requires a large incision over the damaged bones and the application of metal fixtures to the outside of the bone to hold the fragments in place during healing. Intramedullary fixation is an alternative surgical procedure commonly used to fix larger bones like the femur (thigh) or tibia (shin), in which a special pin is placed inside of the medullary canal of the bone. This procedure is typically less invasive through smaller incisions, and eliminates the need for prominent hardware while providing precise bone alignment.

Intramedullary fixation is performed using small incisions over the damaged bone. The bone is prepared using special surgical instruments to allow the intramedullary pin to be properly positioned. The intramedullary pin is inserted into the bone cavity, joining the bone halves (or pieces) together into proper, pre-fracture alignment. Small screws are then drilled from the exterior through the bone to hold the device in place. Intramedullary fixation has proven to result in faster recovery and improved patient comfort.

Project

Sonoma Orthopedics Products, Inc. has been pioneering technologies to facilitate the use of intramedullary devices for ankle, wrist and clavicle fracture repair, bones that have historically been too small to allow for this type of procedure. Their intramedullary fracture repair products involve a proprietary pin technique. After drilling into the bone and aligning the pin with a guide, Sonoma’s intramedullary pin releases fixation grippers in place of screws. The fixation grippers are located within the bone on the far end of the pin, and complemented with additional external screws on the near end. The combination thoroughly aligns and immobilizes the fracture to guarantee proper bone alignment. As this procedure becomes more commonplace, training doctors and surgeons on proper techniques to further decrease recovery time and increase patient quality of life is critical. To train doctors on advanced intramedullary fracture repair procedures, Sonoma Orthopedics wanted to create a model that mimicked bone, accurately recreated delicate fracture variations, and allowed surgeons to use Sonoma’s pins on the model during training.

Challenge

Conventional bone models used to train practitioners on new surgical procedures include cadavers and special foam models. While cadavers could offer the brick and mortar, so to speak, of drilling into bone, cadavers are inconsistent in terms of quality and costly to use for repeated training. Foam models, another common training alternative, are unable to cost-effectively recreate fracture idiosyncrasies or model unique canal geometries on-demand.

“Normally we would use generic foam models or cadavers for training, but both these scenarios carry problems,” explains 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.”

3D printing offered a viable, cost-effective solution to recreating accurate models with repeatable bone fracture types for multiple training scenarios.

Solution

The ability of 3D printing to quickly and accurately reproduce a model directly from computer data makes it an ideal alternative to cadaver or foam bone models for Sonoma. 3D printed bone models provide quality-controlled fractures that actualize important nuances in fracture details from body to body. 3D printed bone models are also printed on-demand to reflect a specific patient’s fracture in order to prepare doctors for more challenging or complicated surgeries.

In order to prepare for the most likely fracture scenarios, Sonoma references an expansive CT-scan library. Sonoma works with the CT-scan library to form accurate representations of 20-50% average bone size and fracture configurations which are then 3D printed as models for training. Using this method, doctors are able to practice with the best average and learn how to heal the most common fractures and abnormalities.

“Sonoma Orthopedic Products partners with Stratasys Direct Manufacturing frequently because 3D printing builds models of fractures and canals that not only demonstrate our surgical device but actually teach surgeons, ‘Here’s how to insert our screw into the bone, here’s how to really use it,” says McDaniel. “We would not get the same quality we get with 3D printing in three days via conventional means.”

“We call the model Bigfoot. Bigfoot works like a tractor beam, attracting surgeons to our booth.”

3D printing provides an ideal low volume production solution for end-use training models, but it is also Sonoma Orthopedics’ go-to for proof-of-concept prototyping and material experimentations. “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,” says 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.”

Sonoma relies on multiple 3D printing technologies for models, prototyping and even marketing collateral. Pictured below is a large scale model of a particular ankle fracture with Sonoma’s intramedullary device in place. Stereolithography is an ideal technology for large, lightweight parts with finer feature details thanks to its ability to print fine layers quickly and in a build volume of 20x20x20”.

3D printed bone model

“Our 3D printed large scale model features fractures expanded to show the application of the screws and to show how the fracture is repaired,” explains McDaniel. “We call the model Bigfoot. Bigfoot works like a tractor beam, attracting surgeons to our booth.”

Results

One unique case in which 3D printing was especially handy for Sonoma involved a clavicle fracture that had healed deformed. After plate fixation surgery and removal, the patient continued to experience limitations in her range of movements and was unable to return to favorite activities.

“The healed fracture looked normal on X-Ray, but after a more thorough CT-scan, the doctor noticed the bone had an abnormality,” explains McDaniel. “It was the abnormality which was causing the patient discomfort.” The doctor determined that the patient’s clavicle bone would need to be re-fractured and healed using a new method: intramedullary fixation. “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.” The surgeon practiced the intramedullary fixation procedure using the 3D printed model and Sonoma’s intramedullary device. After the abnormality in the bone was re-fractured and healed with the intramedullary device, the patient regained full use of their shoulder once more.

3D printing allows Sonoma Orthopedic to take the final intramedullary device used in-body and test it out on 3D printed bone models, providing surgeons with true-to-life training environments that give the feel of real surgery. “When we’re working to find the best ways to mend bones with the least down time for patients, we use as much technology as we can. Conventional manufacturing of these models involves tooling and fixturing, and that takes weeks,” says McDaniel. “I can’t get the same quality I get from 3D printing in just days as I would from conventional manufacturing methods.”

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