Feb 28, 2017 | By Benedict

Researchers at the Mayo Clinic‘s tissue engineering and biomaterials laboratory in Rochester, MN have created a porous 3D printed scaffold implant for patients undergoing ACL (anterior cruciate ligament) reconstruction. The 3D printed scaffold can facilitate bone regeneration.

Load to failure testing of the 3D printed scaffolds

Anterior cruciate ligament injury is one of the most common injuries suffered by athletes, and is most likely to occur to those involved in skiing, soccer, American football, basketball, and gymnastics. Sudden stopping or twisting movements can cause the ligament, which is located in the knee, to stretch too far. The injury is commonly identified by a “pop” in the knee, a feeling that the knee has “given out,” and severe subsequent pain. Ouch!

Because of the high frequency at which ACL injuries occur, finding effective ways to repair a damaged ACL is a top priority for medical researchers. Excitingly, researchers at the Mayo Clinic in Minnesota think they have stumbled upon a potentially game-changing treatment. In a study that has been published in Tissue Engineering, the researchers explain how they have designed a 3D printed porous scaffold that slowly releases a human protein, helping to speed up the recovery of ruptured anterior cruciate ligaments.

According to the group of researchers, which includes Joshua Alan Parry, MD; Sanjeev Kakar, MD; and coauthors from the Mayo Clinic, the 3D printed ACL implant has been engineered to deliver a human bone-promoting protein over an extended period of time in order to improve bone regeneration. The team tested four methods of distributing recombinant human bone morphogenetic protein 2 (rhBMP-2) to the damaged ligament over a period of time. By staggering the release of the protein, the researchers could ensure that the ruptured ACL received the appropriate amount of the protein at given times.

3D printed scaffold designs with 20, 35, and 44 percent porosity

In the study, which is titled “Three-Dimension-Printed Porous Poly(Propylene Fumarate) Scaffolds with Delayed rhBMP-2 Release for Anterior Cruciate Ligament Graft Fixation,” the researchers compared the use of four different protein delivery approaches, including the use of microspheres (microscopic hollow spheres of the protein), to reduce the initial burst release of rhBMP-2 from the scaffold and extend its release over time.

The 3D printed scaffold for treating ACL ruptures is 3 mm in diameter and 10 mm in length, and contains 300 μm pores. Before testing the four unique protein delivery approaches, the researchers created four different scaffold designs varying in porosity, at 0%, 20%, 35% and 44%. Using a rabbit ACL construction model, the researchers found that “the 20% scaffold maintained the greatest pullout strength.”

Next came the comparison of delivery approaches. The researchers found that, out of the four delivery methods tested—microspheres only, microspheres + collagen, collagen only, and a saline solution only—the microsphere delivery groups had a smaller burst release and released a smaller percentage of rhBMP-2 over a 32-day period. “Combining a synthetic bone mineral coating with microspheres had an additive effect, decreasing the initial burst release and cumulative release of rhBMP-2,” they wrote, concluding that the microsphere scaffolds were most effective for bone regeneration.

The Mayo Clinic in Rochester, MN

Peter C. Johnson, MD, Tissue Engineering’s Co-Editor-in-Chief, commented that the study showed promise for the treatment of ACL injuries, highlighting the importance of adopting new methods of treatment. “This work is a good example of the fusion of technologies—controlled release drug delivery and 3D printing,” said Johnson, who is also Principal of MedSurgPI, as well as President and CEO of Scintellix.

The study states that the 3D printed scaffolds were designed using SolidWorks 3D CAD software and fabricated using a Viper si2 Stereolithography 3D printer from 3D Systems. Post-curing was achieved using a 3D Systems UV oven.

 

 

Posted in 3D Printing Applications

 

 

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