Biomechanical evaluation of acromioclavicular joint reconstructions using a 3-dimensional model based on the finite element method

Prescription methodology integrated with equipment designed for customising racing wheelchair

BACKGROUND

Wheelchair racing is a traditional modality of Paralympic athletics. In general, racing wheelchairs are customized according to the athletes' anthropometric conditions, based on pre-established dimensions according to the manufacturer's manual. Usually, athletes choose the dimensions for their new sports wheelchairs, and when they are delivered for use, they often have problems due to incorrect body adjustments.

PURPOSE

To develop a new customization methodology that is made possible through a new multi-adjustable racing wheelchair prescription equipment (RWPE) for athletics. This equipment performs several measurements and adjustments according to the athlete's anthropometric characteristics, evaluating the best-fit athlete to obtain better performance in the personalized wheelchair.

MATERIALS AND METHODS

Customizing racing wheelchairs is based on anthropometric measurements of the individual and specific ergonomic adjustments for better performance and safety. The RWPE is a multi-adjustment device composed of modules that use measuring instruments to guarantee maximum precision and accuracy of the assessments. This project's innovation is associated with the multi-regulation equipment itself and a conventional process of manufacturing a racing wheelchair through an online form. The RWPE has a robust and rigid structure for conducting race-track experimental tests.

RESULTS AND CONCLUSIONS

The experimental tests allowed the equipment to be validated regarding safety, comfort, and prescription methodology. A high-performance athlete validated the equipment and prescription methodology, and as a result, a new version of a parameterized wheelchair was also developed using the prescription methodology. A comparison between prescription tests showed better athlete performance regarding estimated average power, considering dimensions optimized through RWPE.

Computational model of the cancer necrotic core formation in a tumor-on-a-chip device

The mechanisms underlying the formation of necrotic regions within avascular tumors are complex and poorly understood. In this paper, we investigate the formation of a necrotic core in a 3D tumor cell culture within a microfluidic device, considering oxygen, nutrients, and the microenvironment acidification by means of a computational-mathematical model. Our objective is to simulate cell processes, including proliferation and death inside a microfluidic device, according to the microenvironmental conditions. We employed approximation utilizing finite element models taking into account glucose, oxygen, and hydrogen ions diffusion, consumption and production, as well as cell proliferation, migration and death, addressing how tumor cells evolve under different conditions. The resulting mathematical model was examined under different scenarios, being capable of reproducing cell death and proliferation under different cell concentrations, and the formation of a necrotic core, in good agreement with experimental data reported in the literature. This approach not only advances our fundamental understanding of necrotic core formation but also provides a robust computational platform to study personalized therapeutic strategies, offering an important tool in cancer research and treatment design.

Evaluation of the coracoid bone tunnel placement on Dog Bone™ button fixation for acromioclavicular joint dislocation: a cadaver study combined with finite element analysis

BACKGROUND

Dog Bone™ button fixation is frequently used to treat acromioclavicular joint (ACJ) dislocation. However, various studies have reported complications after fixation.

OBJECTIVE

To investigate the effect of the coracoid bone tunnel location on the treatment of ACJ dislocation through single-tunnel coracoclavicular (CC) ligament fixation with the Dog Bone™ button.

METHODS

Six cadaveric shoulders were used. Each specimen was subjected to five testing conditions in the following order: (1) normal ACJ (Gn); (2) acromioclavicular and CC ligaments were removed (G0); (3) CC ligament reconstruction was performed using the Dog Bone™ technique, and the coracoid bone tunnel was at the center of the coracoid base (G1); (4) reconstruction was performed at 5 mm distal from the G1 site, along the axis of the coracoid (G2); (5) reconstruction was performed at 10 mm distal from the G1 site, along the axis of the coracoid (G3). The angles of pronation and supination of the clavicle under the same load (30 N) were measured. Next, a finite element (FE) model was created using computed tomography (CT) images of the normal shoulder. Model 1 (M1), model 2 (M2), and model 3 (M3) correspond to G1, G2, and G3, respectively. A force of 70 N was applied as a vertical upward load to the distal clavicle. Subsequently, the von Mises stress, the strain LE along the FiberWire, and the displacement nephogram of the three models were obtained.

RESULTS

After single-tunnel CC ligament fixation using the Dog Bone™ technique, the clavicle in the G2 group (20.50 (19.50, 21.25) °, 20.00 (18.75, 21.25) °) had the best rotational stability. The peak von Mises stress, the strain LE along the FiberWire, and the maximum displacement were smaller in M2 than in M1 and M3.

CONCLUSIONS

When the coracoid bone tunnel was located 5 mm anterior to the center of the coracoid base (along the axis of the coracoid), the clavicle showed greater rotational stability.

The stress and strain pattern in the ligaments of the acromioclavicular joint using a quasi-static model

BACKGROUND

The precise role of the acromioclavicular and coracoclavicular ligaments during shoulder motion is unclear. We evaluate changes in the stress-strain distribution of the acromioclavicular joint's ligaments during different shoulder passive motion positions.

METHODS

A 3D acromioclavicular joint model was reconstructed. A constitutive hyperelastic model was used for the ligaments. The kinematics of the shoulder girdle was taken to simulate shoulder abduction (Motion 1) and horizontal adduction (Motion 2). A computer-generated quasi-static and non-linear finite element model was used to predict the 3D stress-strain distribution pattern of the acromioclavicular ligament and the coracoclavicular ligament complex.

FINDINGS

In motion 1, from 20 to 90° the peak von Mises stress was found in the conoid (4.14 MPa) and the anteroinferior bundle (2.46 MPa), while from 90 to 120° it was found in the conoid and the trapezoid. However, there were no significant differences between the mean stress values between anteroinferior bundle and trapezoid throughout the motion (p = 0.98). In Motion 2, from 20 to 80° the maximum equivalent elastic strain was found in the anteroinferior bundle (0.68 mm/mm) and the conoid (0.57 mm/mm), while from 80 to 100° it was higher in the conoid (0.88 mm/mm) than in the anteroinferior bundle (0.77 mm/mm).

INTERPRETATION

The coracoclavicular ligament complex demonstrated a high stress-strain concentration during simulated passive shoulder abduction. Additionally, it was shown that the acromioclavicular ligament plays an important role in joint restraint during passive horizontal adduction, changing the primary role with the trapezoid and conoid at different motion intervals.

There is direct relationship between bone bridge length and coracoclavicular fixation resistance to failure: Biomechanical study in a porcine model

BACKGROUND

This study aims to evaluate the relation between coracoclavicular resistance to failure and the distance between clavicular tunnels. The hypothesis is that a greater clavicular bone bridge between tunnels achieves a stronger coracoclavicular fixation.

METHODS

Descriptive Laboratory Study. Thirty-six (36) coracoclavicular models were constructed utilizing porcine metatarsals. Coracoclavicular stabilizations were performed using a subcoracoid loop fixation configuration through two clavicular tunnels, tied at the clavicle's superior cortex using a locking knot. Models were randomly assigned to 1 of 3 experimental groups of variable bone bridge length between clavicular tunnels: 5 mm, 10 mm, and 15 mm. Each group had 12 models. Fixation resistance was assessed through the ultimate failure point under an axial load to failure trial. Failure patterns were documented. A one-way ANOVA test was used, and a Tukey post hoc as needed (P < 0.05).

FINDINGS

Mean strength per bone bridge length: 5 mm = 312 N (Range: 182-442 N); 10 mm = 430 N (Range: 368-595 N); 15 mm = 595 N (Range: 441-978 N). The 15 mm group had a significantly higher ultimate failure point than the other two groups: 5 mm (P < 0.001) and 10 mm (P < 0.001). All fixations systematically failed by a superior cortex clavicle fracture at the midpoint between tunnels.

INTERPRETATION

A direct relationship between bone bridge length and coracoclavicular resistance to failure was demonstrated, being the 15 mm length a significantly higher strength construct in a tied loop model.

[Prognostic evaluation of hip joint function following capsule repair based on a threedimensional finite element analysis model]

OBJECTIVE

To construct a three-dimensional (3D) finite element mechanical model of total hip arthroplasty for comparison of biomechanical differences of the hip joint following capsule repair and postoperative rehabilitation.

METHODS

Six frozen specimens of hip joint posterior capsule ligament complex were collected in a bone-capsule-bone manner, and the load-strain curve and other mechanical properties of the specimens were tested using a universal material testing machine. Thin-section CT data of the pelvis and lower limbs obtained from a volunteer were imported into Mimics software to construct a 3D model of the hip joint. Digital models of the cup, femoral prosthesis and joint capsule were created in CATIA software and imported into Mimics to simulate total hip arthroplasty; the assembled data were imported into ABAQUS software. The properties of the capsule were set according to results of the mechanical test, anatomical studies, and constitutive equations, and the biomechanics of the anatomically repaired and conventionally repaired capsules were compared during hip flexion.

RESULTS

The results of testing on the 6 capsule specimens showed a mean ultimate tensile strain of (39.21±5.23)% and a mean of ultimate tensile strength of 1.65±0.38 MPa. The stress-strain curve of the finite element model was consistent with the results of mechanical test on the specimens and the biochemical characteristics of the capsule. The stress was distributed evenly in the anatomically repaired capsule during hip flexion but not in the capsule repaired through the conventional approach; the tensile stress in the lower part of the conventionally repaired capsule reached the ultimate tensile stress measured on the capsule specimens at a 90° flexion.

CONCLUSIONS

The finite element model allows dynamic, quantitative and visual assessment of stress distribution in the hip joint capsule, and compared with the conventional approach, anatomical repair can achieve better biomechanical properties of the capsule.

Novel Double Endobutton Technique Combined with Three-Dimensional Printing: A Biomechanical Study of Reconstruction in Acromioclavicular Joint Dislocation

Objective

To reconstruct the acromioclavicular (AC) joint using an adjusted closed‐loop double Endobutton technique via a guiding locator that was applied using three‐dimensional (3D) printing technology. At the same time, the reliability and safety of the novel double Endobutton (NDE) were tested by comparing the biomechanics of this technique with the TightRope (TR) approach.

Methods

This retrospective study was conducted between January 2017 and January 2019. The Department of Anatomy at Southern Medical University obtained 18 fresh‐frozen specimens (8 left and 10 right; 12 men and 6 women). First, the guiding locators were applied using 3D printing technology. After preparation of materials, specimens were divided into an NDE group, a TR group, and a normal group. In the NDE and TR groups, the navigation module was used to locate and establish the bone tunnels; after that, the NDE or TR was implanted. However, the Endobuttons were fixed while pressing the distal clavicle downwards and the length of the loop could be adjusted by changing the upper Endobutton in the NDE group while the suture button construct was tensioned and knotted after pressing down the distal clavicle in the TR. Finally, load testing in anterior–posterior (AP), superior–inferior (SI), and medial–lateral (ML) directions as well as load‐to‐failure testing in the SI direction were undertaken to verify whether the NDE or TR had better biomechanics.

Results

In the load testing, the displacements of the NDE and TR groups in the AP, SI, and ML direction were significantly shorter than those of the normal group (P < 0.05). In the load‐to‐failure testing, the ultimate load of the NDE and TR groups had significantly higher increases than the normal group (722.16 ± 92.04 vs 564.63 ± 63.05, P < 0.05; 680.20 ± 110.29 vs 564.63 ± 63.05, P < 0.05). However, there was no statistically significant difference between the two techniques for these two tests (P > 0.05). In the NDE group, four of six failures were a result of tunnel fractures of the coracoid, while two of six were due to suture breakage. In the TR, three failures were due to coracoid tunnel fractures, one was a result of a clavicle tunnel fracture, and the rest were due to suture breakage. In the normal group, half of the failures were a result of avulsion fractures of the conical ligament at the point of the coracoid process, and the other three were due to rupture of the conical ligament, fracture of the distal clavicle, and fracture of the scapular body.

Conclusion

As for the TR technique, the stability and strength of the AC joint were better in patients who underwent reconstruction using the NDE technique than in the intact state.

Dynamics Simulation Analysis and Enhancement of Phased Array Antenna Plate

Phased array antennas have been widely used in military and civilian electronic fields as equipment for transmitting and receiving electromagnetic waves. The flatness of the antenna array is mainly ensured by the rigidity of the antenna frame. Therefore, the structural design of the planar array antenna mainly lies in the structural design of the antenna frame. Given the planarity requirements of the antenna array, how to properly design the structure of the antenna frame becomes a difficult problem facing the structural designer. In this paper, static stiffness and strength analysis are performed using finite element method(FEM) when the antenna is slipping. By establishing finit element model of the antenna, the platforms and the leatheroid ground, the laws of dynamic stress and deformation are researched. Analyse the reasons of structure breakage when it slips, and than advance the method of enhancing the stiffness and strength, offer a theoretical basis of structure design.