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Correspondence to Author: Heng De,
Department of Orthopaedic Medicine, Third Afliated Hospital of Inner Mongonia Medical University, China.
Abstract:
Background : Abstraction The aim of this work is to investigate
the biomechanical characteristics of several internal fixators
for ankle arthrodesis using three-dimensional finite-element
analysis.
Techniques We compared four distinct internal fixations in
ankle arthrodesis using finite-element analysis:
Group D had one anterior anatomical plate (Ø3.5 mm) and
one posterior-lateral screw (Ø6.5 mm), Group C only had
an anterior anatomical plate (Ø3.5 mm), and Group A had
three crossed screws (Ø6.5 mm); Group B had two crossed
screws (Ø6.5 mm) and an anterior plate (Ø2.7 mm). The
displacement of the arthrodesis surface, as well as the
stress peak and stress distribution of these models under
intorsion, extorsion, and dorsifexion torque, were analyzed
and compared for the four types using Ansys 21.0 software.
and a vertical load that is neutral.
Outcomes: Arthrodesis surface displacement: Under
neutral vertical load and dorsifexion torque, Group A’s
maximum displacement was more than Group D’s, but it
was less under intorsion and extorsion torque. The maximal
displacement in Group B was less than that of the other
three fxation models against dorsifexion, neutral vertical
load, intorsion, and extorsion. The maximum displacement
in Group C was much higher than that in the other three
fixation models when compared to the four loading patterns
mentioned above. Stress peak and distribution: the middle
portions of the compression screws, plate joints, and bending
portions of the plates were where the peak von Mises stress
was concentrated, according to the stress distribution of the
four models.
Conclusion: The fxation model with an anterior and two
crossing screws performed better in terms of biomedical
benefits than the other three fxation models; as a result, this
model may be considered a secure and trustworthy internal
fxation method for ankle arthrodesis.
Keywords: Ankle arthrodesis, Biomechanics, Digital orthopedics, Internal fxation, 3D fnite element
Introduction: Fusion surgery is still crucial in the treatment of end stage ankle osteoarthritis, even if there is still no clear gold standard. Nowadays, ankle arthrodesis is seen as a favorable option because of its increased rate of healing and broader spectrum of application [1]. Since Austrian surgeon Eduard Alber first proposed ankle arthrodesis in 1879, the procedure has undergone numerous revisions, leading to the development of dozens of surgical methods [2]. The efficacy of ankle arthrodesis is guaranteed by a sufficient a robust and steady fixation and compression, as well as an efficient and strong contact area. It can help realign lower limbs, relieve discomfort, correct abnormalities, and reconstruct plantigrade feet [2, 3]. The choice of internal fixators is crucial for ankle arthrodesis. A variety of fixation techniques are available, such as internal plate fixation, compression screw internal fixation, intramedullary nail fixation, and external support fixation; nevertheless, the non-healing rate remains between 5 and 37% [4]. There is disagreement over the best location and orientation for internal fxators due to their varying biomechanics. Therefore, by conducting ankle arthrodesis with two crossing screws (Ø6.5 mm) and anterior plates (Ø2.7 mm), we were able to obtain adequate efficacy in this trial. Ten In order to better understand the biomechanical properties of various internal fxators and offer a better solution for maximizing the fxation of ankle arthrodesis, we compared this with other widely used internal fxation methods using biomechanical fnite-element analysis. This laid the theoretical groundwork for upcoming clinical research.
MATERIALS AND PROCEDURES
A healthy adult male volunteer who was 175 cm tall and 65 kg in weight was chosen; he signed an informed permission
form and had no prior history of foot and ankle conditions,
injuries, or other pertinent conditions. The Inner Mongolia
Baogang Hospital Ethics Committee gave its approval to this
study.
Method of study: We took a 64-slice spiral CT plain scan of the volunteer’s right ankle.Using the imported CT imaging data in the DICOM format, we were able to first separate and extract the ankle’s bone tissue structure using the Mimics software. Next, we employed segmentation and denoising to produce a precise and lucid initial 3D tumor model. To match the produced tibiotalar model with the real situation, we imported the pertinent fles into the Geomagic 2017 software. We replicated the joint cleaning procedure used for ankle arthrodesis to build a 3D tibial model. Together with the cartilage and subchondral tissue from the astragalar dome, we also excised the distal tibia. Making four internal fixation types for ankle arthrodesis in three dimensions The interference steps were employed in Solidworks 2017. Software that uses four different internal fixation models to simulate the ankle arthrodesis process. Ultimately, as illustrated in Figs. 1, 2, and Table 1, we performed a fnite-element analysis of the four fxation models. The apparent density of bone [ρ (kg m−3)] was converted to Young’s modulus [E (MPa)]. Based on previous studies [5, 6], E=0:2ρ1:52 (for ρ≤476:7) and E=−3842+13ρ (for ρ>476:7) are calculated. It was not allowed for the contact surfaces to slide or separate. The Young’s modulus of the screw is 200 GPa. It was expected that the Poisson’s ratio for the screws and bones was 0.3. Screws and bones are examples of frictionless interactions. To increase the precision of the contact normal computation, Kuhn surfaces were applied to all exterior surfaces.
Outcomes: Table 2 shows the maximum displacement of the arthrodesis
surface under four stressors for each of the four ankle
arthrodesis models. When compared to the other three
fixation models, the model with two crossing screws and one
anterior plate showed the smallest maximum displacement
under dorsifexion torsion, extorsion, intorsion, and neutral
vertical stress. When compared to the other three fxation
models, the maximum displacement against the four loading
patterns indicated earlier was notably greater in the fxation
model with anterior plates alone. Under neutral vertical load
and dorsifexion torque, the maximum displacement in the
model with three screws was greater than in the model with
anterior plates and posterior-lateral screws. The maximum
displacement compared to the fixation model with front plates
and posterior-lateral screws, the arthrodesis surface under
intorsion and extorsion torque was reduced in the model with
three screws.
The stress distribution and stress maxima for the four different
fxation models are shown in Tables 3, 4, 5, 6, and 7. When
we compared the overall stress peaks of the four models, we
discovered that the stress peaks in the models with anterior
plates and posterior-lateral screws and the model with two
crossed screws and anterior plates had smaller stress peaks
with respect to extorsion and intorsion torque than the
models with anterior plates and three screws. Regarding the
neutral vertical load and dorsifexion torque, the stress peak
was smaller in the flexion-strain model with three screws and
anterior plates than it was in the flexion-strain model with
two crossed screws and anterior plates and the flexion-strain
model with anterior plates and posterior-lateral screws. The
model with the largest stress peak across all four forces was
the fxation model with just anterior plates. The fracture model
with two crossing screws and anterior plates, as well as the
one with three screws, had the highest risk of fractured screws
and plates, as well as stress fracture under vertical load, based
on the stress peaks of the bones, plates, and screws in the four models. The models for fixation that used anterior
plates alone and those that used anterior plates along with
posterior-lateral screws showed the highest risk of stress
fracture under intorsion and extorsion stress patterns, as
well as fractured screws and plates. The compression screws,
plate joints, and plate bending elements are all evidently
under significant stress in their center regions, as indicated
by the stress maps of all four models.
Conclusion:
The ankle joint must be in good working order for the human
body to support weight and move forward. Ankle arthroplasty
and ankle arthrodesis are two surgical techniques used to
treat end-stage joint illnesses include post-traumatic ankle
arthritis, persistent ankle instability, and paralytic deformity
with muscle–tendon imbalance. Research has indicated that
the fusion rate and control of complications were better
with screw fxation, particularly following the introduction
and extensive application of three compression screw
fxation [8, 16, 17]. The majority of the capsule is retained
after arthroscopic fusion, which may increase the stability
of the fusion. However, screw fixation is the sole option
available with arthroscopic fusion.Recent advancements in
ankle arthrodesis have led to the adoption of several locking
plate types and orientations. Biomechanical testing has
demonstrated that the anterior plates act as “tension bands,”
effectively preventing ankle flexion and extension.reducing
the ankle arthrodesis surface’s micro-motion. They can also
significantly raise rotational resistance and help heal broken
bones [18–20]. A transparent surgical field can make the
process easier and allow for a more thorough exposure
of the ankle joint. The third posterior-lateral screw may
significantly withstand dorsifexion and rotational forces and
boost initial stability, depending on the two crossing screws;
nevertheless, its placement can easily damage the peroneal
nerve and cause the screws to clash. So et al. [21] evaluated
and examined the percentage of articular surface area (SA)
loss on the top of the astragalus between the conventional
fixation with two screws and that with three screws using
image analysis software.
According to the results, the third posterior-lateral screw
caused an oval hole because of its modest entry angle and
non-perpendicular direction, which led to a 6%–10% loss
of the SA in the subtarsal joint. As a result, patients with
low bone mass must utilize this screw cautiously. So et al.
suggested combining low screw force with locking plates.
Since 2020, we have been doing ankle arthrodesis through
a small anterior incision utilizing the fxation with two
crossed screws (Ø6.5 mm) and anterior plates (Ø2.7 mm),
after carefully weighing the advantages and disadvantages
of several internal fxation models and access options. The
biomechanical characteristics could not be identified, despite
the positive therapeutic outcomes.Because of the rapid
advancement and widespread use of computer technology,
finite-element analysis is a dynamic, widely used, practical, and
efficient numerical analytical method that has quickly spread
from structural engineering strength analysis to practically
all sectors of science and industry. It was first applied to the
measurement of bone stresses in orthopedic biomechanics in
1972 [22]. Since then, its application to stress analysis of bones
and bone prosthesis, fracture fixation devices, and non-bone
tissues has grown. Its purpose is to evaluate the connection
between load-bearing function and morphology and to offer a
theoretical foundation for clinical practice, thereby optimizing
implant design and fxation techniques. For static or dynamic
analytical study, finite-element analysis can replicate operating
circumstances that are not possible to produce in traditional
biomechanical studies.
with the benefits of being quick, inexpensive, repeatable, and
having thorough performance testing. It can also supplement
traditional biomechanical experiments and offer more
thorough, precise, varied, and three-dimensional mechanical
data for therapeutic use. The application of the finite-element
approach to the research of ankle joint biomechanics has
increased recently [23–26]. Ankle arthrodesis has been
analyzed using finite-element method. The initial stability of
three-screw fixation for ankle arthroscopic anthrosis was the
main focus of Wang et al.’s investigation. In comparison to the
posteromedial home-run screw, the screw configuration of the
latter was proven to be more biomechanically stable and to
prevent collisions [27]. Three types of two-screw configuration
fixation were used by Zhu et al. to analyze the initial stability
and stress distribution of ankle arthroscopic arthrodesis.
For the present being, however, there isn’t a finite-element
analysis that focuses on the mechanical characteristics of
the anterior plate in ankle arthrodesis. Furthermore, to
offer trustworthy evidence support for additional clinical
research and clinical practice, a cross-sectional assessment
of the mechanical characteristics of various ankle arthrodesis
internal fixation techniques by finite-element analysis is
urgently required.
In this investigation, we gathered and imported into the Mimics
software the CT scan imaging data of a volunteer adult male
in good health. We used this information to build a crude 3D
ankle joint model. Using the Geomagic software, we smoothed
and denoised the model to create a strong model. Lastly, we
put the data into the Solidworks program to simulate various
procedures like ankle arthrodesis and perform assembly and
cutting. Using this, we developed the experimental models
for finite-element analysis for four different types of ankle
arthrodesis. In order to get the final analysis findings, we lastly imported the models into the finite-element analysis
program Ansys and adjusted the loading conditions, analysis
settings, and characteristics. This study has a high degree
of simulation and validity since the 3D finite-element model
it built can fully acquire spatial information from different
angles and the design of many parameters approximates
clinical reality.
The term “microdisplacement of the arthrodesis surface”
describes the deformation of the ankle’s arthrodesis surface
under torsion, extorsion, dorsifexion torsion, and and neutral
stresses brought on by walking’s stride. The effectiveness
and durability of internal fixators for ankle arthrodesis can
be determined by the displacement value. According to
the study’s findings, the displacement of the arthrodesis
surface under neutral and dorsifexion torsion in the fixation
model with anterior plates alone was significantly smaller
than that under extorsion and intorsion. This suggests that
anterior plates had a significant advantage against neutral
and dorsifexion torsion, but that their resistance to intorsion
and extorsion was only moderate. The displacement under
neutral load, dorsifexion intorsion, extorsion, and intorsion
was significantly less in the fxation model with anterior plates
than it was in the model with a 6.5 mm posterior-lateral
screw based on anterior plates, particularly under intorsion
and extorsion. suggesting that a greater fixation effect may
result from the posterior-lateral screw’s location. This notion
is also supported by the findings of Xie [30] and Cliford [29].
The degree of deformation of the arthrodesis surface under
the four forces varied little in the fxation model with three
screws, suggesting that this model can offer more evenly
distributed resistance to outside forces.
In terms of resistance to intorsion and extorsion, the fusion
model with three screws proved to be more advantageous
than the fusion model with anterior plates and posterior lateral screws; the anterior plates demonstrated satisfactory
resistance to both neutral stress and dorsifexion intorsion,
particularly the latter. In relation to the displacement of the
arthrodesis surface, the fixation model utilizing anterior
plates and posterior-lateral screws fared better.
The displacement of the arthrodesis surface against neutral
stress, dorsifexion intorsion, intorsion, and extorsion was
smaller in the fxation model with two crossed screws and
anterior plates than in the other three models, according
to our analysis of the experimental results, which clearly
showed this to be the most stable configuration out of the
four models. The majority of forces were centered in the
middle regions of the compression screws, plate joints, and
plate bending portions, according to the stress distribution
and stress peak. This suggests that after ankle arthrodesis,
the materials used in these areas should be strengthened
and thickened to avoid fractured screws and plates.
Regarding resistance to extorsion and intorsion, the fxation model with three screws and the fxation model with two
crossed screws and anterior plates outperformed the fxation
model with anterior plates and the fxation model with anterior
plates and posterior-lateral screws. In terms of resistance to
dorsifexion intrusion and neutral (vertical) stress, the fusion
model with anterior plates and two crossed screws, as well
as the fusion model with anterior plates and posterior-lateral
screws, outperformed the fusion model with three screws.
SUMMARY
Out of the four fxation models, the one with two crossing
screws and anterior plates had the best biomechanical
performance, according to a thorough investigation of the
stability and safety of the models. In comparison to the other
three fxation models, it exhibited the smallest maximum
displacement under extorsion, intorsion, torsion, and neutral
vertical load. Out of the four models, the fixation type with
two crossing screws and anterior plates had the best safety in
terms of dorsifexion and intorsion torque.
The results of this study suggest that basic anterior plate
fxation with three screws is best saved for patients with strong
bones because it has a minimal compressive effect and is not
very safe. When a plate and screws are applied together, the
biomechanical effects are better and the fixation strength is
higher than when either plate or screw is applied alone. A
better option for patients who need more fixation strength is
to apply plate screws in combination.
The tiny anterior plate can counteract the Achilles tendon’s
strength, and by shrinking it, patients’ local blood flow and
soft tissue damage can be lessened. This offers patients who
have poor local soft tissue conditions in the surgical site an
alternate surgical choice.
However, there were numerous issues with this study: The
study did not take into account the impact of soft tissues,
including muscles and ligaments, on ankle joints. Additionally,
the majority of patients receiving ankle arthrodesis are middle aged and older individuals suffering from osteoporosis, and
their bone problems are directly linked to the loosening of
screws. Our investigation is restricted to the software’s use,
and more biomechanical studies are required to confirm the
results.
Citation:
Heng De. 3D finite-element analysis is used to compare several internal fixation models in ankle arthrodesis. The Journal of Hepatology 2024.
Journal Info
- Journal Name: The Journal of Hepatology
- Impact Factor: 1.6
- ISSN: 3064-6987
- DOI: 10.52338/tjoh
- Short Name: TJOH
- Acceptance rate: 55%
- Volume: 7 (2024)
- Submission to acceptance: 25 days
- Acceptance to publication: 10 days
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