Slipped capital femoral epiphysis is the most common hip disorder in children aged 9 to 16, affecting about 11 in 100,000 children in the US annually. It's treated via surgery to reshape the head of the femur, and needless to say – the quicker that the operation can be completed, the better. That's why scientists from the University of California San Diego have been experimentally using 3D-printed models of patients' hips to reduce surgery time by approximately 25 percent.

In the study, pediatric orthopedic surgeon Dr. Vidyadhar Upasani operated on a total of 10 children. With five of them, he first practised on 3D-printed models of their hip joints. These were made by a team led by MD student Jason Caffrey, using CT scans of the patients' pelvises. The models featured a honeycomb-like internal structure that simulated the structure of bone.

For the other five patients, Upasani didn't use models. Instead, he relied on the traditional method of studying X-rays of the hip before performing the surgery. Additionally, two other surgeons operated on a different group of five patients without first practising on models.

When everything was compared, it turned out that the model-guided operations were 38 to 45 minutes shorter than those in the two control groups. According to the university, that would translate into at least US$2,700 worth of time-savings per surgery. The printer that was used had a one-time cost of about $2,200, with each model costing around $10 in materials.

The findings of the study were so convincing that the orthopedics department of Rady Children's Hospital, where Upasani performs surgeries, has purchased its own printer. "I've seen how beneficial 3D models are," he says. "It's now hard to plan surgeries without them."

Surgeons at the University of Louisville have previously used an oversize 3D-printed model of a 14-month old child's heart to plan for what turned out to be life-saving surgery.

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