Orbital surgery aided by 3-D printing

Reviewed by Paul Langer, MD Newark, NJ-Three-dimensional (3-D) printing can produce models of facial skeletons and guides to help orbital surgeons plan repair of complicated fractures, according to Paul Langer, MD. “In the cases where we have used it, the alignments have been excellent,” said Dr. Langer, professor of ophthalmology, Rutgers New Jersey Medical School, Newark. “In our experience it’s been very, very helpful.” Related: Exploring anti-VEGF therapy for orbital vascular lesions Dr. Langer and a resident, Leon Rafailov, MD, described their experience with the new technology. “Typically, the fracture cases where we’ve used this technology are those with severe comminution or with fragments missing,” Dr. Langer said. “That’s when the technology is most useful because we can anticipate what we’ll find at the time of the surgery.” In simple trauma cases where there are only one or two fractures, 3-D printing is not necessary, he said. Dr. Langer’s institution does not own its own 3-D printer; it contracts with private companies that print the guides. How it works How it works The process begins with computed tomography (CT) of the injury. The CT must have slices of 1.25 mm or thinner, Dr. Langer said. “Five-mm cuts will not be able to transmit enough information,” he said. Related: Endoscopy can aid treatment of pediatric nasolacrimal duct obstruction The surgeon then must send the CT scan by compact disc using overnight delivery to the 3-D printing company, which downloads it to make the virtual model. The surgeon then meets in a web-based conference with engineers from one of the companies. Together the surgeon and the engineer manipulate the images of the bone fragments to plan the surgery. “It helps us to know ahead of time by moving the pieces virtually what will be missing or how the bones will fit together,” he said. Moving actual bone fragments during surgery is difficult because they are connected to muscles and arteries. More: AD-IOLs mimic movement of natural lens Typically, the engineer will call back the next day with images of guides for approval. Dr. Langer sometimes asks for more adjustments, such as space for more screws. When Dr. Langer has approved the guides, the company prints them out in polyamide. The 3-D printing company sends the guides to its representative, who delivers them to the hospital. Intraoperatively, Dr. Langer lays the guides over the fracture to align the segments and screws the guide in place to temporarily hold the fracture segments in place. Then he screws a metal plate over the fracture and removes the guide. “Otherwise, while you’re putting screws and plates on the bone fragments, you may move them and not get the contour or curvature you want,” Dr. Langer said. Related: Surgeons face choices in pediatric orbital cellulitis The 3-D printers can also produce acrylic facial skeletons, which are sterilized and used intraoperatively to guide fracture reduction, for example, by helping shape a metal plate. “I can shape an implant exactly to the contour I want, then pull it off the printed skull and put it in the patient,” Dr. Langer said. Case example In one case, Dr. Langer operated on a 19-year-old man with multiple periorbital fractures and significant comminution and misalignment of bones following a gunshot to the right face. After virtually manipulating the CT images on a computer, Dr. Langer discovered there was a large bone fragment missing. He then worked with an engineer to design guides to realign the larger fracture segments. Recent: Targeting refractory vitreous seeds in retinoblastoma The printing company then produced a model of the reconstructed facial skeleton showing the bone fragments realigned in their optimal locations. It also produced guides for the procedure. Dr. Langer corrected the defect in the right inferior orbital rim with a porous polyethylene implant. Postoperative CT showed excellent symmetry and alignment. The technology has also been used in surgery to aid in facial reconstruction after tumor removal, Dr. Langer said. Currently several companies are competing to provide this technology. One drawback to this approach is the time required to send the CT scans by mail to the company, planning by web conference and then shipping the 3-D models back to the hospital. Recent: ARVO 2017 making global connections in vision research “If I see a patient today, I can’t operate tomorrow,” Dr. Langer said. “It’s usually 4 to 5 days.” As the technology becomes more widely available, more hospitals may buy their own 3-D printers, making this approach even more available, he said. Dr. Langer has also used 3-D printing to create implants. For example, he recently operated on a women who had been in a car accident years earlier. The original surgery to reassemble fragments of her skull left a divot in her forehead. “I imagined there were bone fragments missing, extruded through the laceration or whatever, and the defect was so long-standing it would be difficult to break those bones and reset them,” Dr. Langer said. “So we created an implant that would smooth out that defect into an arc rather than a divot.” He designed the implant by computer, then had it printed out of polyether ether ketone (PEEK) “which is strong and hard and biologically inert so you can implant it in patients and screw it in,” he said. “You can shape it with a drill or a saw.” After sterilizing the implant, Dr. Langer screwed it in place on the woman’s forehead. “She was very happy because she had had this defect for years and now her forehead was smooth,” he said. More: Simultaneous ocular myasthenia gravis and thyroid eye disease? Paul Langer, MD E: planger@njms.rutgers.edu This article was adapted from Dr. Langer’s presentation at the 2015 meeting of the American Academy of Ophthalmology. He did not indicate any proprietary interest in the subject matter.