Doctors display a 3D printed model of the knee joint. ”This is the femur, this is the tibia, and this is the route through which the guide pin is positioned during surgery.” Yesterday morning, in the orthopedic classroom of Li Huili Hospital, Dr. Shen Wenge, chief physician of the department, held a knee model and demonstrated it to reporters. A few days ago, through 3D printing technology, medical staff “replicated” a car accident patient’s left knee joint, and after “rehearsal” to finalize the entire surgical plan. The surgery, which would have taken two hours, took only one hour after the preliminary “rehearsal. The model was copied 1:1 according to the surgical site At the scene, the reporter saw that the knee model was slightly transparent white, two bones were connected by a steel pin, each bone was the size of an adult man’s fist. A 15 cm long needle is inserted under the tibia, passing through the cross-section of the two bones and finally out the side of the femur. “The model is a 1:1 replica for the surgical site.” Shen Wenge said. The reporter learned that the patient surnamed Shen, female, Cixi, 47 years old. 4 months ago, Shen riding an electric car and a small car collision, the left leg was injured outside the knee. The local hospital took a film, did not find the problem, that is, the general trauma. Shen sister then went home. But soon after, she found that she walked a little wrong, can not run, can not jump, let alone walk when the emergency stop. As soon as these movements, there is a sense of dislocation, as if they are about to fall. This makes Shen a little afraid to go out. Shen came to the city’s major hospitals, magnetic resonance examination found that her left knee anterior cruciate ligament has been ruptured. The doctor suspects that it was the car accident that caused the damage. The ligament rupture is not like a fracture, it can grow back after fixation, the ligament is broken, can not be sutured, can only be replaced with autologous, allogeneic or artificial ligament, while the original ruptured ligament cleaned up. The surgery Shen needed was called an arthroscopic ACL reconstruction. Under the arthroscope, an allograft ligament is implanted and fixed in the joint to replace the patient’s torn ligament. The surgery is not too big, but it is complex and requires a high degree of precision. Shen Wenge pointed to the model and said, “The two points on the cross-section of the femur and tibia are called isometric points, and finding this point is the key to the surgery.” In the past, this type of surgery was performed by repeatedly adjusting the locator under the arthroscope to find the isometric point and perform the surgery. The surgery was time-consuming and the intraoperative damage was not insignificant. Moreover, because the surgery relied more on the surgeon’s personal feeling and experience, cases where the isometric point was not equal in length also occurred, with deviations in the implantation position, unsatisfactory ligament reconstruction, and patients walking, running and jumping with a sense of impact or other abnormal sensations after the surgery. This small model provided a valuable “rehearsal” for this difficult surgery. By observing and measuring the model, the doctors were able to find the correct incision and isometric points and finalize the entire surgical plan. The rest of the surgery was a “copycat” operation, so to speak. The surgery, which could have taken more than two hours, was completed in just one hour. Currently, Shen is recovering well, and she will be discharged from the hospital in a short time. 3D printing model error of no more than 1 mm 3D knee model is how to make out? The reporter interviewed the producer of a biotechnology company in Ningbo, the person in charge of Luo Kun told reporters that the model, two technicians worked overtime and spent a full day rushing out. The technicians first brought the surgical site dense scan CT, and then select the valid data, after integration into the 3D conversion software, “we selected 372 valid data from more than 400 data, that is, 372 flat images, stacked one by one to form the image, and finally into the CD-ROM, connected to the 3D printer to start printing.” Luo Kun introduced. All the data, the technical staff are many times to check, the error can not exceed 1 mm. Because, a small error of 1 mm, presented on the model, it will be a small step of 1 mm, the model at first glance is problematic, can not be used. This time, the printing, the use of resin materials. Only the “rough embryo”, it took 8 hours to print. Then the brackets were reduced and the joints were smoothed. Then it took two hours to harden and one hour to light. “The hardening solution contains many chemicals, which are rather pungent, and the odor will only evaporate when it is illuminated under a spotlight.” Luo Kun said. It is reported that 3D printing technology applied in the medical field, in Ningbo City is the first time. In the future, in addition to orthopedics, 3D printing technology will also appear in neurosurgery, vascular surgery, thoracic surgery and many other departments, while depending on the condition of the choice of resin, titanium metal or biomaterials as raw materials.