Jul 11, 2017 | By Benedict

Researchers at the University of North Carolina and North Carolina State University have conducted a study to evaluate two 3D printing methods, electron beam melting (EBM) and direct metal laser sintering (DMLS), for manufacturing titanium osseointegrated implants.

Titanium 3D printed osseointegrated implants can be used to improve the integration of prosthetic devices

One thing that everyone involved in 3D printing can agree on is that titanium 3D printed implants are transforming modern medicine. But beyond that obvious statement, there’s a lot of room for argument.

For example, medical and additive experts are still trying to find out what 3D printing techniques are best for producing medical implants, while competing medical device companies generally all claim that their own 3D printed designs are the most effective at repairing the body, encouraging bone regrowth, or fitting naturally and safely into their designated bodily location.

These disagreements make it especially important for independent researchers to carry out experiments on 3D printed titanium implants, and that’s exactly what researchers from two North Carolina universities have just done.

A study conducted by the two universities has shown that 3D printing can be used to customize implant surface textures and geometries to match the specific anatomy of human amputees. But perhaps most interestingly, the study tested both EBM (using an Arcam A2 3D printer) and DMLS (using an EOS M290) 3D printing techniques, finding that the techniques produced differing results.

The subject of the study was the production of titanium osseointegrated implants, medical devices upon which new bone can grow and interact.

“Osseointegrated implants transfer loads from native bone to a synthetic joint and can also function transdermally to provide a stable connection between the skeleton and the prostheses, eliminating many problems associated with socket prostheses,” the researchers wrote in their research paper. “Additive manufacturing provides a cost-effective means to create patient-specific implants and allows for customized textures for integration with bone and other tissues.”

During the study, two groups of Sprague-Dawley rats received bilateral titanium implants in their distal femurs, one group receiving EBM implants transcortically in one femur and a DMLS implant in the contralateral femur, the other receiving DMLS implants in the intramedullary canal of each femur. The rats were then studied for four weeks.

Each 3D printed implant measured 7 mm in length and 2 mm in diameter, and was made from grade 5 titanium.

Surface topography of fine-textured (left) and coarse-textured DMLS titanium implants

Interestingly, while the EBM 3D printing method can only produce a coarse textured implant, DMLS can create either a fine or coarse textured surface. Knowing this, the researchers wanted to see how the techniques affected resulting strength of bone integration, interlocking, and torque.

When the rats’ four-week period of evaluation was up, the North Carolina researchers found that the fixation strength of coarse-textured implants provided better interlocking than fine-textured implants, without affecting bone volume fraction (BV/TV) or bone-implant contact (BIC) in both rat groups.

Additionally, the researchers discovered that the coarse EBM 3D printed implants in the transcortical model demonstrated an 85 percent increase in removal torque over the fine DMLS textured implants.

They also found that the thrust load in the intramedullary model saw a 35 percent increase from fine to coarse DMLS implants.

Their conclusion? “This research indicates that coarse textured surfaces can provide a higher interface strength for titanium alloy implants than fine textured surfaces,” they wrote. Of course, that’s hardly a damning evaluation of DMLS, since the metal 3D printing technique can also produce coarse textures, but it does suggest that coarse-textured 3D printed implants are ideal in such situations.

While the North Carolina researchers recommend that “future studies should be conducted to determine the optimal roughness for implant fixation,” their research could already prove useful for medical professionals looking to utilize 3D printing to create titanium osseointegrated implants.

The research paper, titled “Osseointegration of Coarse and Fine Textured Implants Manufactured by Electron Beam Melting and Direct Metal Laser Sintering,” was published in 3D Printing and Additive Manufacturing.

Its authors were David S. Ruppert, Ola L.A. Harrysson, Denis J. Marcellin-Little, Sam Abumoussa, Laurence E. Dahners, and Paul S. Weinhold.

 

 

Posted in 3D Printing Application

 

 

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