Development of patient-specific orbital floor implants made of shape memory alloys

The shape memory alloy NiTi has successfully proved in many areas of medical technology. This paper describes the innovative idea and development of orbital floor implants made of NiTi. Pseudoelastic NiTi has the peculiarity that it can withstand large mechanical deformations of up to 8% without being plastically deformed, i.e. it goes back to its original shape with relief of the strain. This material property can be used to produce flexible, yet stable implants. The NiTi implants can be implanted into the body in compressed form over relatively small approaches. Arriving at the fracture position, they develop self-reliantly in the previously memorized shape. The perioperative trauma is reduced. The treatment of orbital floor fractures is often done surgically by use of implants from rigid materials such as titanium, which are inserted in the eye socket through an open approach on the lower eyelid. Implants made of a pseudoelastic shape memory alloys can help to reduce the required incision length of approach. It is even possible to insert the implant in a minimally invasive procedure via endoscopic access routes and to completely avoid open approach. In this paper first design variants of pseudoelastic orbital floor implants are presented and considerations on the manufacturing process are made.