Page 298 - IJB-9-4

International Journal of Bioprinting Design and biomechanical analysis of porous tantalum prostheses

1. Introduction prostheses, especially in the evaluation of the designed
prostheses from the viewpoint of bone biomechanics.
Artificial knee arthroplasty is one of the most common and
successful orthopedic surgeries for the treatment of end- This paper reports a clinical case on the application of
[1]
stage knee disease . However, after the joint replacement, a FEA in designing patient-specific tantalum prostheses with
series of complications such as infection, bone resorption, or an appropriate pore size and wire diameter for knee joint
aseptic loosening may require joint revision surgery. Among revision. Particularly, standard porous tantalum cylinders
various materials for joint revision surgery, porous tantalum with various pore sizes and wire diameters were first
has attracted extensive attention because of its clinically fabricated by using a selective laser printing technology and
validated excellent abrasion, corrosion resistance, and their compressive mechanical properties were measured.
osteointegration [2-5] . More importantly, it has been noticed Subsequently, FEA models on the patient-specific tibia and
from joint revision surgery that the geometrical shape of bone prostheses were developed from the patient’s computed
defects and the mechanical properties of surrounding bone tomography (CT) data. By using the models, the maximum
tissue vary with patients and bone defect sites. Consequently, von Mises stress and displacement for porous tantalum
the commercialized standard modular blocks cannot match prostheses and tibia and the maximum strain for the tibia
the bone defect region geometrically and biomechanically. were numerically simulated. Finally, according to the
Development of patient-specific porous tantalum prostheses biomechanical requirements on both the prostheses and
with matching shape and biomechanics may help to increase the tibia, the tantalum prostheses with appropriate pore size
the success rate of joint revision surgery. and wire diameter were determined. This work provides a
valuable reference for the clinical design of porous tantalum
Extensive tracks and clinical follow-up observations prostheses for joint revision surgery.
have proven that porous tantalum as various prostheses can
induce strong osteointegration and produce satisfactory
repair outcomes [6-11] . The earliest technology employed to 2. Materials and methods
fabricate porous tantalum is chemical vapor deposition . 2.1 Mechanical test
[12]
The representative manufacturer is Zimmer. Tantalum has Seven kinds of standard cylinder porous tantalum samples
[13]
a high melting point of ~2996°C . With the development (diameter 15 mm, height 20 mm) with a pore shape of
of 3D printing technologies, some technologies capable of dodecahedron were manufactured using a selective laser
providing a temperature high enough to melt tantalum, melting (SLM; FARSOON Technology, China) system
such as electron-beam-melting-based and laser-melting- by Zhuzhou Printing Additive Manufacturing Co. Ltd in
based technologies, are being employed to fabricate porous Hunan Province, China. The fabrication was performed
tantalum [14-16] . The fabricated porous tantalum prostheses in argon atmosphere with a laser power of 250 W, a laser
geometrically match well with the bone defect and result scanning speed of 150 mm/s, and an energy density of
in effective osteointegration and treatment . In addition 241.5 J/mm . Different pore size (900–1500 μm) and wire
[16]
3
to geometrical matching, ideal patient-specific porous diameter (300–600 μm) were selected. To simplify the
tantalum prostheses should have appropriate mechanical description, the sample with a wire diameter of m and a
properties to guarantee the mechanical safety of both the pore size of n was recorded as m/n. The specific pore and
prostheses and the bone tissue [17-20] . Therefore, regulating wire diameter information is shown in Table 1.
and measuring the mechanical properties of tantalum
prostheses seem critically important. The uniaxial compression mechanical tests were
carried out by using AG-X50kND electronic universal
Pore size and wire diameter are two critical parameters material testing machine from SHIMADZU, Japan. All
in 3D printing to regulate the mechanical properties the test samples were compressed at a loading rate of
of scaffolds. However, it is difficult to carry out in vivo 1 mm/min until 50% strain occurred. The diameter (d)
mechanical tests on the implanted prostheses or the bone and height (h) of the sample were measured with a caliper
tissue. Therefore, numerical simulation of the in vivo before experiment. The cross-sectional area of the sample
biomechanical responses by using finite element analysis (A) was calculated using A = π × (d/2) . According to the
2
(FEA) becomes a more effective approach [21-23] . FEA can obtained stress–strain curves, the Young’s modulus and
provide the mechanical responses of bone tissue [24-26] and yield strength were calculated. At least three specimens
prostheses [27-30] under various mechanical environments, were tested for each sample.
which in turn is valuable to guide the design and fabrication
of prostheses. Despite the wide applications of FEA, few 2.2. Construction of the tibia and prosthesis models
studies were reported on its application in the clinical The patient was an 84-year-old male with severe
design of patient-specific 3D-printed porous tantalum osteoarthritis in his left knee. After 16 years of left knee

Volume 9 Issue 4 (2023) 290 https://doi.org/10.18063/ijb.735