Xiaogang Wu

Osteocytes are force-sensitive cells possessing a complex lacunar-canalicular system (LCS), embedded within a piezoelectric bone matrix. TRPV4, as a key mechanosensor, plays a crucial role in osteocyte mechanotransduction and related bone disorders. However, the mechanisms underlying its force sensing, mechanical signaling pathways, and biomechanical response remain poorly understood. To address this issue, this study established a finite element model incorporating multiple mechanosensors-including bone matrix, LCS, osteocytes, and TRPV4-based on the piezoelectric effect. By integrating the multiphysics coupling of solid mechanics, fluid mechanics, and electric fields to simulate the complex effects on osteocytes, the model calculated stress, strain, and fluid shear stress (FSS) on TRPV4. Result indicate that piezoelectricity significantly increases stress and strain in TRPV4, particularly FSS. Biomechanical parameters of TRPV4 exhibit significant variations across different locations, with the highest stress levels observed at the cell processes (Maximum increase of approximately 300%). Stress distribution patterns also differ across distinct regions, while stress concentration in TRPV4 primarily occurs in its transmembrane domain and ion channel regions. This study reveals that upon coupling with primary cilia and RhoA, the mechanical response mechanism of TRPV4 undergoes significant alteration. TRPV4 exhibits greater sensitivity to fluid shear stress, whereas Piezo1 responds more strongly to membrane stress. This study elucidates the microscopic mechanical response mechanism and gating activation mechanism of TRPV4 within complex bone cell environments. It clarifies the interaction mechanisms between TRPV4 and other cellular structures, providing a research pathway for understanding bone cell mechanical transduction mechanisms and complex interactions across multiple scales. This work offers theoretical insights into the pathogenesis and therapeutic approaches for TRPV4-related bone disorders.

Prolonged internal fixation in the femur can cause issues like osteosclerosis and stress masking, which hinder fracture recovery. AZ31b magnesium alloy has already been widely investigated and shown to be biocompatible and biodegradable. This study used finite element analysis to investigate stress changes during healing, aiming to find the best time for removing internal fixation and focuses on optimizing the structural design of internal fixation, using AZ31b magnesium alloy, to address issues like osteosclerosis and stress shielding in femoral neck fracture healing. This study focuses on optimizing structural design for the treatment of Pauwels III femoral neck fractures using cannulated screws. Pauwels III fractures are characterized by high shear stress and unstable fracture angles, making them prone to fixation failure. By optimizing the fixation method, the risk of complications such as osteosclerosis and stress shielding can be mitigated, ultimately improving clinical outcomes. The findings show that when cancellous bone heals but cortical bone does not, stress on the fracture surface decreases. Early removal of titanium internal fixation, followed by biodegradable porous internal fixation, allows for natural degradation during healing. We simulated stress evolution across healing stages via finite element modeling to determine optimal fixation replacement timing. Four AZ31b magnesium alloy porous structures (cubic, honeycomb, diagonally orientated, modified truncated pyramid) were designed; their equivalent elastic modulus and strength were evaluated through simulated compression tests, while permeability was analyzed using computational fluid dynamics (CFD). We found that the cubic and honeycomb structures were found to have higher permeability (6.23 × 10 ^-7 m ² , 1.636 × 10 ^-7 m ² ) and have high elastic modulus (8.422Gpa, 14.694Gpa) which can match the elastic modulus of human bone. Optimal structures were then applied to an inverted triangular screw group model for biomechanical validation post-femoral neck fracture fixation. Finite element analysis of a Pauwels III femoral neck fracture model indicated that the honeycomb porous internal fixation had superior mechanical properties. In conclusion, this study proposed a solution to osteosclerosis and stress masking after femoral neck fracture surgery.

Fusion devices play a critical role in lumbar fusion surgery. Titanium alloy fusion devices offer good biocompatibility and stability, but their mechanical properties far exceed those of bone, leading to stress shielding effects after implantation, which can reduce spinal fusion rates and cause endplate collapse. On the other hand, fusion devices made of polyether ether ketone (PEEK), which has a lower elastic modulus, are not conducive to bone ingrowth and fusion stability due to their material properties. Personalized fusion devices that can precisely adapt to a patient’s physiological condition are not widely used due to their lengthy design cycle. This study proposes an optimized design method based on a titanium alloy-PEEK composite structure. By constructing three composite structure models—PEEK core and Ti frame (square hole type, circular hole type, plate type)—and combining finite element compression simulation with machine learning algorithms, the structural parameters are intelligently optimized. The machine learning algorithm used in this study is Back Propagation Neural Network. The aim of this study is to match the equivalent elastic modulus of the fusion device with that of cortical bone. The three optimized fusion devices, along with the Ti fusion device and PEEK fusion device as control groups, were implanted into a traditional PLIF postoperative model for static and transient dynamic analysis. The biomechanical responses of the lumbar spine at various locations after implantation of the five fusion devices were analyzed and compared. The results indicate that all three optimized fusion devices effectively reduce the risk of device settlement, thereby mitigating stress shielding effects, improving fusion rates, and enhancing postoperative lumbar stability. Among them, the circular hole inner core fusion device (M2) demonstrated the best overall performance. The peak von Mises stress of L4 lower endplate and L5 upper endplate in M2 model were 54.2% and 27.7% respectively lower than those in Ti fusion device. Compared with Ti fusion device, the strain energy of M2 model increased by 49.7%. The development framework of this study which integrated “finite element simulation-machine learning-postoperative model biomechanical validation and evaluation” can effectively reduce the design cycle and cost of personalized orthopedic implants.

Many lumbar interbody fusion methods have been proposed, but there is a relative scarcity of fundamental biomechanical research on these varied surgical procedures. In this study, a finite element model of an L4-L5 functional spinal unit was created and five interbody fusion methods were evaluated, including posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), extreme lateral interbody fusion (XLIF), oblique lateral interbody fusion (OLIF) and anterior lumbar interbody fusion (ALIF). Static and harmonic vibration surgery analysis models were developed based on it, investigating the biomechanical properties, as well as the variation of strain energy. Results indicate that while OLIF and XLIF produced similar biomechanical outcomes, 45.8% higher facet joint contact stress in OLIF compared to XLIF. In contrast, TLIF and PLIF exhibit superior performance, with TLIF showing stress concentration on the left-side screw. ALIF outperformed other models in terms of overall stability, but has significantly higher stress peaks and sensitivity to vibration loads. In general, PLIF exhibits no significant shortcomings, TLIF offers excellent dynamic performance, OLIF and XLIF may exert greater pressure on the facet joints, and ALIF provides optimal stability. The integration of these findings into clinical practice can provide a theoretical basis for clinical surgeons when selecting surgical approaches.

Aging lacuna-canalicular system (LCS) has osteocyte size reduction, cell process number loss, and canaliculus blockage. This study built four osteocyte aging models for various aging features. These models have processes, collagen hillocks, and primary cilia mechanoreceptors for signal comparison. A triaxial displacement load on the piezoelectric bone matrix was utilized to explore mechanical signal changes in the absence of different processes, canaliculi blockage, and the effects of aging on osteocyte mechanoreceptor signals. Osteocyte age doesn't affect piezoelectric effect electric field strength. The aging model flows slower than the normal model. Blocking canaliculi raises fluid pressure. Aging osteocytes lack processes, reducing primary cilia and process stress-strain. Osteocyte volume reduction and canaliculi blockage exacerbate this alteration.

The addition of microstructures to the inner surface of the stent reduces resistance and inhibits the phenomenon of blood adhesion. In this study, the design of a fish-scale microstructured vascular stent was proposed based on bionics, and its main design parameters were optimized using the finite element method. In addition, the hemodynamic effects of a standard stent and a fish-scale microstructured stent on an ideal cerebral aneurysm were comparatively analyzed. The results showed that the fish-scale microstructured stent significantly accelerated intraluminal blood flow velocity by 11.6% compared to the standard stent. In addition, the fish-scale microstructured stent was able to reduce blood flow into the aneurysm lumen by 28.6%.

Introduction: The electric signals within the cartilage tissue are essential to biological systems and play a significant role in cartilage regeneration. Therefore, this study analyzed and investigated the reverse mechano-electrical effect in porcine articular cartilage and its related influencing factors.Methods: The deflection of cartilage samples in an electric field was measured to analyze the mechanisms of different factors affecting the reverse mechano-electrical effect in articular cartilage.Results: The results showed that the cartilage thickness, water content, and externally applied voltage all impacted the deflection of the cartilage. The reduction in cartilage water content resulted in a decrease in cartilage thickness, following the same influencing mechanism as thickness. On the other hand, an increase in the externally applied voltage led to an increase in the electric field force within the cartilage space, consequently increasing the deflection of the cartilage in the electric field. Additionally, the externally applied voltage also caused a slight temperature rise in the vicinity of the cartilage specimens, and the magnitude of the temperature increase was proportional to the externally applied voltage.Discussion: The fitting results of the experimental data indicated that cartilage thickness influenced the dielectric constant and moment of inertia of the cartilage in the electric field, thereby affecting the magnitude of the electric field force and deflection of the cartilage. This may provide valuable insights for further investigation into the microscopic mechanisms of cell proliferation, differentiation, and cartilage regeneration induced by electrical stimulation.

In lumbar spinal fusion, the titanium cage tends to cause stress shielding due to their high elastic modulus, which can lead to degenerative lesions in adjacent spinal segments. Furthermore, polyetheretherketone (PEEK) cages have certain material characteristics that do not promote bone ingrowth and fusion stability. In this study, a new cage was designed, and its biomechanical performance in percutaneous endoscopic posterior lumbar interbody fusion (PE-PLIF) was analyzed using the finite element (FE) method. A complete model of the L4–L5 lumbar spine was established, and static and harmonic vibration FE analysis models were developed based on it. The biomechanical properties of titanium, PEEK, and combined cage in PE-PLIF fusion were compared. The strain capacity of the combined fusion increased by 9.5% when compared to the titanium fusion. The surgical model under the combined fusion reduces the L5 endplate stress by 12% in the forward flexion condition and the fusion stress by 17% in the vibration condition compared to the model supported by the titanium fusion, and the differences in screw stress and mobility among the three models are not significant in multiple conditions. Consequently, the combined cage demonstrates a certain reduction in the stress-shielding effect when compared to the titanium cage; it has better fusion effect and provides theoretical support and guidance for the design of the clinical fusion cage. Graphical abstract