3D printing of patient-specific implants for osteochondral defects: workflow for an MRI-guided zonal design

Abstract

Magnetic resonance imaging (MRI) is a common clinical practice to visualize defects and to distinguish different tissue types and pathologies in the human body. So far, MRI data have not been used to model and generate a patient-specific design of multilayered tissue substitutes in the case of interfacial defects. For orthopedic cases that require highly individual surgical treatment, implant fabrication by additive manufacturing holds great potential. Extrusion-based techniques like 3D plotting allow the spatially defined application of several materials, as well as implementation of bioprinting strategies. With the example of a typical multi-zonal osteochondral defect in an osteochondritis dissecans (OCD) patient, this study aimed to close the technological gap between MRI analysis and the additive manufacturing process of an implant based on different biomaterial inks. A workflow was developed which covers the processing steps of MRI-based defect identification, segmentation, modeling, implant design adjustment, and implant generation. A model implant was fabricated based on two biomaterial inks with clinically relevant properties that would allow for bioprinting, the direct embedding of a patient’s own cells in the printing process. As demonstrated by the geometric compatibility of the designed and fabricated model implant in a stereolithography (SLA) model of lesioned femoral condyles, a novel versatile CAD/CAM workflow was successfully established that opens up new perspectives for the treatment of multi-zonal (osteochondral) defects. Graphic abstract

A dual osteoconductive-osteoprotective implantable device for vertical alveolar ridge augmentation

“…Combined, these premises established a method for the custom design of a personalized grafting device for alveolar augmentation procedures. Similar workflows for 3D printing of patient-specific grafts for large volume bone regeneration have been published before, using either extrusion bioprinting (9,10,46) or laser stereolithography (47). Towards this goal materials such as resorbable porous PCL (9), PCL/TCP paste combined with hydrogel (48), porous HA loaded with cells (49), or bi-material printing of TCP with growth factor-loaded alginate hydrogels (50) have been considered.…”

Osteochondral regenerative engineering: challenges, state-of-the-art and translational perspectives

“…In the same year, another group developed a unique concept of defect-specific reconstruction of osteochondral lesions using advanced magnetic resonance imaging (MRI) data processing combined with micro-extrusion-based 3D bioplotting [ 141 ]. In brief, MRI scan data of a multi-zonal osteochondral defect in an osteochondritis dissecans (OCD) patient were obtained and the data were processed using a set of 3D image processing algorithms, followed by the generation of the 3D printable CAD file (*.stl) ( Fig.…”

Biomaterials of human source for 3D printing strategies

“…The medical images obtained by CT and MRI, for example, can be computationally transformed using CAD software and mathematical modeling [45,46]. As examples of such applications, the design of a thyroid cartilage implant, using CAD to biofabricate a collagen-based construct [33]; in situ 3D bioprinting of chondrocytes directly onto large cartilage defects and osteoarthritis lesions, using medical imaging for diagnosis and CAD to deliver cells in a spatiotemporally controlled manner [32]; and the treatment of osteochondral defects using MRI for defect identification, segmentation, modeling and implant design adjustment, and CAD to create the 3D constructs for implantation [31]. Indeed, such strategy has already been tested and optimized for other and varied medical applications: for TE and drug delivery systems; to customize medical devices and therapeutics; as well as inert implants and medical hardware [47][48][49].…”