Additive, layer-by-layer manufacturing process allows for the manufacture of complex geometries in plastic and metal implants and orthoses.
Engineers have long been aware of the potential of laser sintering to create innovative and beneficial medical products. Because it is an additive (layer-by-layer) manufacturing process, laser sintering can build parts free of the traditional constraints imposed by machining or molding.
Recent medical applications of laser sintering are now demonstrating the technology’s unique capabilities for mass customization and the manufacture of designs with complex geometries in both plastics and metals.
Plastic Drill Guides for Knee Surgery
Conventional knee replacement surgery involves reusable measurement and drilling guides that are available in predetermined sizes. The inevitable variation in the shape of each patient’s knee means that one of these sizes may be the best fit, but none of them is a perfect fit. A better option is to make each guide patient-specific.
One medical device supplier is currently laser sintering a customizable, disposable drill guide from a biocompatible polyamide thermoplastic (based on PA 12). Starting with a 3D MRI or CT-scan image of the knee, a surgical drill guide (used to pinpoint drilling location) can be designed, and then laser sintered, to reflect a patient’s joint geometry to a tolerance of within a few millimeters (see Fig. 1). Using such guides results in smaller incisions, better-fitting implants, and faster patient recovery. Manufacturing a custom guide for individual patients would be far more expensive — if not prohibitively so — than using traditional manufacturing methods.
Titanium Dental Implants
Dental implants have long been made from titanium because of its strength-to-weight ratio, corrosion resistance, biocompatibility, and affinity for binding with human bone. Creating dental implants with direct metal laser-sintering (DMLS) produces significant improvements in their design and function.
One supplier’s patented line of titanium dental implants includes a uniquely complex surface geometry that promotes bone growth. The dental implant surface is characterized by 2-200 micron cavities created during laser sintering (see Fig. 2). These porous surface characteristics cannot be readily obtained through traditional metal-finishing methods. Both the pores and the isoelasticity of the dental implant surface (a Young’s modulus nearly identical to that of bone) promote osseointegration and accelerated bone healing following surgery (see Fig. 3). The dental implants are manufactured using Ti64, a pre-alloyed Ti6AIV4 alloy powder that is much like its conventional counterpart.
The same manufacturing characteristics that make laser sintering an excellent choice for these examples have led to other medical applications: replacement plastic hip drill guides; lightweight, durable ortheses; and cobalt-chrome dental bridges and copings, among others. Medical designers are also exploring other in vivo applications, such as a new high-performance sterilizable PEEK thermoplastic for customized implants, and a cobalt-chrome knee implant now at the prototype stage.
This technology was done by EOS GmbH Electro Optical Systems, Krailling, Germany. For more information, visit http://info.hotims.com/34454-163.