“Orbit” is the term surgeons use for the eye socket. The most common types of orbital fracture are orbital floor (blow-out) fracture due to sports injuries, motor vehicle accidents or hits from direct blunt objects.
Any orbital-related surgery involving implants is complex and lengthy, since each patient’s eye socket is uniquely shaped. The implant of choice needs to be precisely shaped manually before it is inserted into the space, a time-consuming operative procedure that relies on the ophthalmologist’s clinical experience and often requires several adjustments until it fits the curvature of the patient’s orbit. Any mismatch between the implant and the orbit in size or shape can lead to orbital volume expansion or malposition.
Traditionally ophthalmic surgeons would create the implant from either a titanium mesh, a thin piece of porous polyethylene or a combination of both, and manually insert into the subperiosteal space after all unstable bone fragments have been removed and the prolapsed tissues is reduced.
Now Hong Kong Polytechnic University’s Industrial Center (IC) is using 3D printed models to improve eye orbital implant surgery accuracy and reduce operating times. IC uses a Fortus 3D Production System from Stratasys to create customized molds for the orbital implants, in just three to four hours.
Using a patient’s CT scan and X-ray images, the IC team reconstructs the patient’s orbital floor in CAD software. They then 3D print two thermal layers – the upper and lower parts of the mold – and press a thin titanium sheet between the two mold parts to form the shape. This precision helps ophthalmologists create accurate implants before an operation and is expected to be particularly beneficial in complicated cases like complex fractures involving multiple orbital walls and rims.
Customized Implants with Sterilizable Material
The Fortus’ material options played a key role in improving surgeries. Since artificial parts are placed inside a patient’s orbit, everything from the implant to surgical guides needs to be completely decontaminated. PC-ISO, a bio-compatible thermoplastic used to print strong, heat-resistant surgical parts, became the immediate answer. Because the material is bio-compatible in its raw state (it complies with ISO 10993 USP Class VI) and can further be gamma or EtO sterilized, it’s ideal for the medical industry.
“Surgeons would only need to sterilize the mold and form the implant shape by pressing the two parts together, resulting in an accurate customized implant,” said Louis Sze, assistant engineer at the Hong Kong Polytechnic University.
3D printing helps visualize a patient’s missing orbital floor (left) versus original shape before impact (right)
More Projects Coming Up
IC currently is the registered Hong Kong Hospital Authority supplier of customized surgical guides such as orbital implants, orthopaedic pre-surgery models and dental models. However, it continues to incorporate 3D printing technology into other projects. For instance, the Fortus 3D Production System has become one of IC’s most used instruments for research and student projects and also allow for better training by producing accurate anatomical models.