Having personal experience with the typically agonizing time spent in a waiting room while a loved one undergoes surgery, I am a big fan of anything that safely reduces the amount of time patients have to spend on an operating table, including 3D printed surgical models for training and planning purposes. Medical models, specifically patient-specific ones, allow surgeons to get their eyes, and their hands, on the organ or body part they’ll be operating on ahead of time, which lets them plan out exactly what they need to do during the surgery. This can decrease the amount of surprises that could pop up during the procedure, and helps get the patient out of surgery faster. A joint research team of pediatric orthopedic surgeons and bioengineers from UC San Diego and Rady Children’s Hospital are jumping on the proverbial bandwagon and using 3D printed models to shorten pediatric hip surgeries and train surgeons.

Dr. Vidyadhar Upasani, a pediatric orthopedic surgeon at both UC San Diego and Rady Children’s Hospital, said, “Being able to practice on these 3D-models is crucial.”

The specific surgery the team is working to shorten is for the most common hip disorder in children ages 9 to 16 – slipped capital femoral epiphysis (SCFE), which affects roughly 11 out of every 100,000 children each year in the US; it’s commonly associated with obesity and hormonal dysfunction. The head of the patient’s femur deforms the bone plate by slipping along it, and surgeons have to restore hip function by sculpting the femur into its normal shape. It’s a tricky procedure, because the bone and its growth plate are not directly visible during the surgery, so surgeons can’t get a 3D visualization of how exactly the plate is deformed.

Typically, surgeons pre-plan the necessary bone cuts by studying X-rays of the surgery site from different angles, and then an X-ray fluoroscopy beam illuminates the site for guiding purposes from time to time during the surgery itself. But both of these methods expose children to radiation, and can take a long time; that time also increases because surgeons aren’t able to practice the surgery ahead of time on a physical model. This is where 3D printing technology swoops in to save the day.

The researchers recently published a study, titled “Patient-specific 3D models aid planning for triplane proximal femoral osteotomy in slipped capital femoral epiphysis,” in the Journal of Children’s Orthopaedics. The research showed that by giving surgeons a 3D printed model of the young patient’s hip joint to prepare with ahead of time, the amount of time needed for the surgery was reduced by about 25% when compared to a control group. Senior author Dr. Upasani worked with D.R. Wenger, M. Jeffords, C.L. Farnsworth, and J.D. Bomar from Rady Children’s Hospital; UC San Diego’s A.F. Szewczyk, E. Cory, and bioengineering professor Robert L. Sah; and UC San Diego students Jason Caffrey, who’s pursuing a PhD in bioengineering, and Lillia Cherkasskiy, working towards an MD, to process CT scans of patients’ pelvises with Materialise Mimics software and create a 3D printable, computerized model of the bone and growth plate.

According to the paper’s abstract, “The purpose of this study was to evaluate the benefits of using 3D print technology to aid in surgical planning.”

UC San Diego engineering alumnus Jason Caffrey

The study was inspired by a hands-on engineering class that Professor Sah taught two years ago. Caffrey assisted with the class, where students used CT scans of UC San Diego patients to 3D print models of complex ankle bone fractures. The class is still being taught today.

One difficulty that the research team ran into was working out the right texture for the models so that they accurately mimicked real bone. The 3D printed model would break if the texture was too thin, and a surgical tool would melt it if it was too thick; they ended up using a honeycomb structure, and each model took four to ten hours to print with ABS material on a LulzBot TAZ 6. Using Professor Sah’s lab at the UC San Diego Jacobs School of Engineering, Caffrey led the 3D printing efforts, and Dr. Upasani operated on a total of ten patients for the study, only using the 3D printed models to plan the surgeries for five. Two other surgeons operated on a separate group of five patients, without using a 3D printed model for pre-surgical planning.

Dr. Upasani said that Rady Children’s orthopedics department was so inspired by the positive results of the study that it purchased its own 3D printer.

“I’ve seen how beneficial 3D models are. It’s now hard to plan surgeries without them,” said Dr. Upasani.

(a) Pre-operative anteroposterior (AP) radiograph of a proximal femur of a 15-year-old girl with SCFE. (b) AP view of this patient’s proximal femur 3D model, (c) the mock surgery osteotomies were performed and wedge removed and (d) fragments in final position. (e) A radiograph taken three months post-operatively indicates the correction achieved by the TPFO.

The surgeries for the group of patients where Dr. Upasani used the 3D printed models for planning were 38-45 minutes shorter than the surgeries of the two control groups. Researchers said that this would equal at least $2700 in savings per surgery, and after the one-time cost of purchasing a $2200 3D printer, surgical planning models can be created for a cost of about $10.

Caffrey and Dr. Upasani are now working together to use 3D printed models in an effort to determine the best way to surgically correct hip dysplasia in infants. Discuss in the Hip Surgeries forum at 3DPB.com.

[Source/Images: UC San Diego]

 

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