Advancing Frontiers in Bone Bioprinting

Three-dimensional (3D) bioprinting of cell-laden biomaterials is used to fabricate constructs that can mimic the structure of native tissues. The main techniques used for 3D bioprinting include microextrusion, inkjet, and laser-assisted bioprinting. Bioinks used for bone bioprinting include hydrogels loaded with bioactive ceramics, cells, and growth factors. In this review, a critical overview of the recent literature on various types of bioinks used for bone bioprinting is presented. Major challenges, such as the vascularity, clinically relevant size, and mechanical properties of 3D printed structures, that need to be addressed to successfully use the technology in clinical settings, are discussed. Emerging approaches to solve these problems are reviewed, and future strategies to design customized 3D printed structures are proposed.

Three-dimensional Bioprinting for Bone and Cartilage Restoration in Orthopaedic Surgery

Notable shortcomings exist in the currently available surgical options for reconstruction of bone and articular cartilage defects. Three-dimensional (3D) printing incorporating viable cells and extracellular matrix, or 3D bioprinting, is an additive manufacturing tissue engineering technique that can be used for layer-by-layer fabrication of highly complex tissues such as bone and cartilage. Because of the scalability of 3D bioprinting, this technology has the ability to fabricate tissues in clinically relevant volumes and addresses the defects of varying sizes and geometries. To date, most of our in vitro and in vivo success with cartilage and bone tissue bioprinting has been with extrusion-based bioprinting using alginate carriers and scaffold free bioinks. Fabrication of composite tissues has been achieved, including bone which includes vascularity, a necessary requisite to tissue viability. As this technology evolves, and we are able to integrate high-quality radiographic imaging, computer-assisted design, computer-assisted manufacturing, with real-time 3D bioprinting and ultimately in situ surgical printing, this additive manufacturing technique can be used to reconstruct both bone and articular cartilage and has the potential to succeed where our currently available clinical technologies and tissue manufacturing strategies fail.

Three Dimensional Printed Bone Implants in the Clinic

Implants are being continuously developed to achieve personalized therapy. With the advent of 3-dimensional (3D) printing, it is becoming possible to produce customized precisely fitting implants that can be derived from 3D images fed into 3D printers. In addition, it is possible to combine various materials, such as ceramics, to render these constructs osteoconductive or growth factors to make them osteoinductive. Constructs can be seeded with cells to engineer bone tissue. Alternatively, it is possible to load cells into the biomaterial to form so called bioink and print them together to from 3D bioprinted constructs that are characterized by having more homogenous cell distribution in their matrix. To date, 3D printing was applied in the clinic mostly for surgical training and for planning of surgery, with limited use in producing 3D implants for clinical application. Few examples exist so far, which include mostly the 3D printed implants applied in maxillofacial surgery and in orthopedic surgery, which are discussed in this report. Wider clinical application of 3D printing will help the adoption of 3D printers as essential tools in the clinics in future and thus, contribute to realization of personalized medicine.