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Investigating the Influence of Architecture and Material Composition of 3D Printed Anatomical Design Scaffolds for Large Bone Defects
but this approach requires a complex surgical procedure jetting allowing high reproducibility and precise control
usually performed in specialized clinical centers [7]-[10] . over the porosity, PS, and pore interconnectivity [22]-[26] .
Bone shortening allows bone healing to start Under an Engineering and Physical Sciences Research
immediately and assists soft tissue coverage by reducing Council/Global Challenges Research Fund (EPSRC/
the defect size or soft tissue tension . However, for very GCRF) project entitled “Bone Bricks: Low cost-effective
[11]
large bone defects (>8 cm), this clinical approach must be modular osseointegration prosthetics for large bone
combined with other treatments to be effective . loss surgical procedures” authors aim to develop and
[11]
Distraction osteogenesis is based on the principle that implement a novel low cost osseointegrated modular
bone and soft tissues can be regenerated under tension. It prosthetic solution to treat large bone loss injuries to
involves the application of a modular-ring external fixator enable limb salvage. The immediate application is to
and allows early bearing, stimulates local blood flow, and treat Syrian refugees who have been displaced to Turkey.
produces good quality bone. However, it is a complex and The project proposes to build on the current treatment of
laborious technique usually associated with chronic pain, external fixation but with the addition of an engineered
infection, nervous, and vascular injury and scars due to the internal prosthetic implant to improve patient outcomes,
metal wires transfixing and cutting through soft tissues . avoid painful limb lengthening, and reduce recovery
[12]
Masquelet and Begue , proposed a two-stage time. A patient-specific prosthetic to fill the bone lost
[13]
approach to treat bone defects in both septic and due to injury is being developed using biodegradable
aseptic conditions. First, a cement spacer is placed in and biocompatible modular pieces (bone bricks), from a
the bone defect, inducing the formation of a biological pallet of shapes and sizes that fit together in a Lego-like
membrane around it [14],[15] . Then, the cement spacer is way to form the prosthesis. The assembled prosthesis
removed, and a biological graft is placed within the tube will create a hollow cage which will be filled with an
of the induced impermeable, vascular, and biological infection prevention paste containing calcium sulfate
active membrane [14],[15] . However, autografts despite and polymeric microbeads encapsulating antibiotics
being osteogenic, osteoinductive, and osteoconductive (Figure 1). This paper presents preliminary results
and have no risks of immunogenicity and disease considering anatomical designed bone bricks produced
transmission, present several limitations such as pain using different architectures and material composition.
and morbidity in the donor site, limited quantity and Produced structures are morphologically, mechanically,
availability, prolonged hospitalization time, the need for and biologically investigated.
general sedation or anesthesia, risk of deep infection and
hematoma, extended non-weight bearing, and the risk of 2. Materials and methods
inadequate graft hypertrophy [16]-[19] .
Moreover, current clinical approaches require 2.1. Materials
long inability periods with consequences difficult to
quantify (social integration, family, and psychological/ Polycaprolactone (PCL) (CAPA 6500, Mw = 50000Da), a
mental problems). They are also expensive, and some semi-crystalline linear aliphatic biopolymer, was supplied
are relatively complex, posing significant problems to
surgeons treating groups of risk such as refugees and
victims of conflict zones . Therefore, there is a demand
[20]
for novel bone replacements, which must be cost-
effective, biocompatible, infection resistant, bespoke,
or modular, providing the initial bone stability to allow
weight-bearing and biological integration for long-term
stability .
[21]
A range of different techniques has been explored
to produce physical supports for cell attachment,
proliferation, and differentiation. These techniques
include conventional processes such as solvent casting,
freeze-drying, phase separation, gas foaming, melt
molding, and particle-leaching, usually involving the use
of toxic organic solvents and not allowing the control of
porosity, pore size (PS), pore shape, pore distribution,
and pore interconnectivity; and additive manufacturing
processes such as vat-photopolymerization, extrusion-
based processes, powder-bed fusion, binder, and material Figure 1. Bone bricks approach for large bone loss treatment.

44 International Journal of Bioprinting (2021)–Volume 7, Issue 2