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Materials Science in Additive Manufacturing MAM for orthopedic bone plates: An overview

organized to cover the entire spectrum of manufacturing The process of fracture healing is protracted, typically
phases through AM, from material evolution and spanning 3 – 6 months. Recognizing this, some bone
bone plate design to prevailing technologies and post- plates are engineered as permanent fixtures, obviating the
processing methodologies for the additive manufactured need for subsequent removal surgeries [47,48] . These plates,
bone plates. Furthermore, insights into potential future especially those for load-bearing bones, must be resilient to
directions associated with AM in bone plate development endure the healing process and accommodate the specific
are provided. biomechanical loads .
[49]
2. Essentials of bone plate integration When designing or selecting bone plates for medical
applications, it is crucial to address a multifaceted set of
Bones are fundamental to the structural integrity and requirements. These encompass not only the choice of
mobility of vertebrates. Among them, long bones, such material composition, ensuring compatibility, and durability
as the femur, tibia, fibula, metatarsals, humerus, ulna, but also the mechanical and biomechanical properties
radius, metacarpals, and phalanges, play a crucial role that guarantee optimal performance under physiological
in providing support and facilitating movement . Due conditions. In addition, the biomedical implications, including
[39]
to their prominence and function, these bones are often biocompatibility, potential inflammatory responses, and
susceptible to injuries, commonly resulting from accidents long-term outcomes for the patient, are equally significant in
or physical trauma. determining the success of the bone plate.
To address such injuries, medical professionals resort
to a range of treatments. One prevalent method involves 3. Overview of MAM
the use of internal implants to stabilize fractured bone AM, often referred to as 3D printing or rapid prototyping,
fragments. Depending on the specific location and has transformed the landscape of manufacturing since
[50]
function of the injured bone, various implants ranging its pioneering introduction in 1984 . Unlike traditional
from bone plates and intramedullary nails to K-wires manufacturing methods that subtract material, AM adds
and screws are employed . Among these, osteosynthesis material layer by layer, hence its nomenclature. This
[7]
plates, which facilitate the healing process, are particularly method not only optimizes material usage but also offers
significant. Their vital role in ensuring the proper fusion of unparalleled design freedom.
fractured bone segments has made them an indispensable The journey of an additive manufactured product begins
tool in orthopedic treatments . in the digital realm. A product design is first conceptualized
[15]
Orthopedic plates play a pivotal role in the healing and then rendered into a digital 3D model using computer-
process of fractures, but their design and material aided design software or through 3D scanning of an
composition are crucial for optimal patient outcomes. The existing object. This digital model is saved in the.stl format.
ideal materials for these implants should be non-toxic, Before printing can commence, this model is processed
biocompatible, non-immunogenic, and bioactive, ensuring using slicing software. The software breaks down the model
[40]
both effective healing and patient comfort . As outlined into hundreds or thousands of horizontal layers, creating a
by the Arbeitsgemeinschaft für Osteosynthesefragen, the G-code file. This G-code serves as the instruction manual for
key principles of internal fixation include meticulous the AM machine, dictating every precise movement it must
alignment of fractured fragments, secure stabilization, undertake. Guided by this code, the printer systematically
preservation of blood supply, and early initiation of deposits or solidifies the chosen material layer upon layer,
functional movement . gradually giving shape to the desired object.
[41]
However, a significant challenge in the realm of While the foundational concept of AM remains
orthopedic plates is the discrepancy in stiffness between consistent, the technologies driving it have proliferated into
metal plates and natural cortical bones. Metal plates, diverse paths. At present, over 20 distinct AM technologies
commonly used in medical applications, often possess a have been acknowledged . Standardizing bodies such as
[32]
stiffness much higher than that of bones. This differential can ASTM and ISO classify them into seven primary categories:
lead to undesirable consequences, such as stress shielding, Binder jetting (BJT), directed energy deposition (DED),
manifesting as bone loss beneath the plate, or osteoporosis material extrusion (MEX), material jetting, powder bed
in the regenerated bones [42,43] . To circumvent this issue, fusion (PBF), sheet lamination, and vat photopolymerization
the design focus has shifted toward creating bone plates (VPP) [29,32] . These categories encompass various techniques,
with materials that mimic the stiffness of natural bones. materials, and applications, with certain methods such
Such designs foster a conducive mechanical environment, as BJT, DED, MEX, and PBF specialized in fabricating
promoting effective bone fracture healing [44-46] . metallic products. The MAM sector prominently features

Volume 2 Issue 4 (2023) 4 https://doi.org/10.36922/msam.2113