Osteocytes are the most abundant and long-lived cells in bone,serving as primary regulators of bone remodeling.Besides playing critical roles in endocrine regulation and calcium-phosphate metabolism,osteocytes are primary responders to mechanical stimuli,perceiving and responding to these stimuli directly and indirectly.The process of mechanotransduction in osteocytes is a complex and finely tuned regulation involving interactions between the cell and its surrounding environment,neighboring cells,and various mechanosensors within the cells with distinct functions.The known major mechanosensors in osteocytes include primary cilia,Piezo ion channels,integrins,extracellular matrix,and connexin-based intercellular junctions.These mechanosensors play crucial roles in osteocytes,perceiving and transducing mechanical signals to regulate bone homeostasis.This review aims to provide a systematic introduction to these five mechanosensors,offering new perspectives and insights into understanding how osteocytes respond to mechanical stimuli and maintain bone tissue homeostasis.

Objective To analyze coating properties of porous artificial joints,including coating morphology and coating mechanical properties,and summarize the range of coating properties of current mainstream products,to provide references for the design and development of new products,as well as provide the basis for the long-term implant removal analysis.Methods Samples for the surface morphology,shear strength,and tensile strength of the coatings used in the experiment were prepared in accordance with ASTM F1854,ASTM F1044,and ASTM F1 147 standards,respectively.The coatings were processed using plasma spraying.The surface morphology(coating thickness,porosity,and pore intercept)of the coatings for all 17 products(Nos.1-17)was tested;for products Nos.1-7 and Nos.15-16,the shear strength test between the coating and substrate was conducted first in accordance with the test method of ASTM F1044.Then,according to the test method of ASTM F1 147,the tensile strength test between the coating and substrate was conducted.For product No.17,the shear and tensile strengths of the composite coating and simple titanium coating were tested,respectively,according to the test method of ASTM F1044 and ASTM F1 147.Results A total of 15 products(88.2％)had coating thicknesses between 300 μm and 500 μm.There were 16 metal-coated products(Nos.1-16),of which 11(68.75％of the total)had coating porosities between 30％and 50％,and 14(87.5％of the total)had coating pore intercepts between 50 μm and 150 μm.The mechanical properties of the coatings were independent of the substrate material used.The shear and tensile strengths of the composite coatings with hydroxyaptite(HA)were significantly lower than those of the pure metal coatings.Conclusions For the design and manufacture of artificial joints with porous coatings,the performance of the coating can be referred to the following indexes:the coating thickness is 300-500 μm,the coating porosity is 30％-50％,the coating pore intercept is 50-150 μm.The substrate materials can be selected based on the use of the product.The effects of a lower bonding force on product performance should be considered when designing prostheses with composite coatings containing HA.This range of performance metrics provides control for long-term clinical extraction analyses.

Objective To analyze and compare the strength of titanium alloy crystalline porous scaffolds and porous scaffolds with a triply periodic minimal surface(TPMS)structure and explore the effect of porosity on the equivalent elastic modulus and permeability.Methods Crystalline porous scaffolds(cell 1-4)and TPMS porous scaffolds(P-,G-,D-,and FKS-type)with the same porosity were constructed,and the equivalent elastic modulus,equivalent yield strength,and permeability of the scaffolds were calculated using finite element simulation.Results The elastic modulus of eight scaffolds was in the range of 5.1-10.4 GPa,the yield strength was in the range of 69-110 MPa,and the permeability of 4 crystalline scaffolds was in the range of 0.015-0.030 mm2.Conclusions With an increase in porosity,the elastic modulus and yield strength of the scaffold gradually decreased,and the permeability gradually increased.The cell 2-type scaffold is suitable for repairing defects at load-bearing bone sites because of its high elastic modulus and yield strength.The cell 3-type scaffold with a uniform stress distribution and a longer linear elasticity phase may be suitable for designing porous tibial platforms for knee joint prostheses.

Objective To study the biomechanical differences between hollow compression screws and shape-memory alloy staples in triple arthrodesis internal fixation and to provide references for the clinical application of shape-memory alloy staples.Methods Two-dimensional(2D)computed tomography(CT)foot data from a patient with severe horseshoe foot stiffness were selected,and a triple arthrodesis model was established using Mimics and Geomagic software.A geometric triple arthrodesis internal fixation model was established using SolidWorks 2021 software.Four fixation schemes(A,B,C,and D)were established according to the type and combination of fixed screws(hollow compression screws and shape-memory alloy riding nails).The biomechanical characteristics of models with different internal fixation schemes under neutral physiological loading were simulated and analyzed using ABAQUS software.Results The maximum end-face displacements of the fused surfaces of the talocalcaneal talonavicular and calcaneocuboid joints in the internal fixation model of scheme D were greater than those in schemes A,B,and C.The differences between the medial and lateral displacements of the fused surfaces of the talonavicular and calcaneocuboid joints in the internal fixation model of scheme D were 13.10％and 13.60％,respectively.The fused surface displacements were closer to the parallel displacements than those in the other three fixation schemes.The von Mises stresses were greater than those of schemes A,B,and C.Conclusions The application of scheme D(internal fixation at fusion surfaces of the talonavicular and calcaneocuboid joints with staples and at fusion surfaces of the talocalcaneal joints with compression hollow screws)provides stability at fusion surfaces of the internal fixation after triple arthrodesis surgery with near-parallel micromovement,which produces appropriate fusion stresses to make contact at the fusion end closer,promote the growth of bone scabs,and achieve better fusion results.

Objective To study the effects of different posterior slope installations of unicompartmental knee arthroplasty(UKA)prostheses on the loading and motion of the knee joint and insert wear.Methods A combined approach involving the UKA musculoskeletal multibody dynamic,finite element,and wear prediction models was used to investigate the effects of five different posterior slope installation positions of the UKA prosthesis on the postoperative knee joint force and motion,insert contact stress,linear wear depth,and wear volume.Results At a 0° posterior slope,the maximum von Mises stress of the insert was 24.84 MPa,maximum contact stress was 47.61 MPa,and volumetric wear after 5 million cycles(MC)was 47.29 mm3.As the posterior slope angle of the UKA prosthesis increased,the internal rotation and posterior translation during the gait cycle increased,the medial joint force during the swing phase increased,the von Mises and contact stresses of the insert after 5 MC decreased significantly,and the wear area,maximum linear wear depth,and volumetric wear volume of the insert were consequently reduced.Compared to the 0° posterior slope,the linear wear depths of the insert at the 3°,5°,and 7° posterior slopes decreased by 17.8％,19.2％,and 20.6％,respectively.The volumetric wear volumes of the inserts decreased by 24.5％,30.9％,and 34.3％,respectively.Conclusions Installing a UKA prosthesis with a posterior slope exceeding 3° significantly increases internal rotation and posterior translation during the gait cycle,further reducing the articular volumetric wear of the polyethylene insert.

Objective To obtain the range of anatomical parameters of healthy knee joints in Chinese males and validate a statistical shape model(SSM)based on the geometric shape of a healthy knee to provide references for the design of knee SSM-based prostheses.Methods Computed tomography(CT)images of knee joints from 112 healthy males were acquired to build three-dimensional(3D)knee joint models.Each model was the target model separately,and the remaining models were used as the training set for principal component analysis(PCA).The obtained knee SSM was fitted to the target model to predict the SSM.The exact anatomical measurement points were marked on the sample and SSM prediction models,and 17 linear and 3 angular parameters were derived.The values of the anatomical parameters were statistically tested using an independent samples t-test and Mann-Whitney U-test,and the validity of the SSM in terms of geometric shape was demonstrated if the resulting P-values were all greater than 0.05.Results Qualitative and quantitative comparative analyses of anatomical parameters showed that the mean deviation of linear parameters was less than 6 mm,and that of angular parameters was less than 2.5°.The results of statistical tests showed P＞0.05 for all anatomical parameters,proving that the knee SSM prediction model was not statistically different from the true healthy model in terms of geometric shape.Conclusions This study derived a reference range of anatomical parameters for a healthy knee and demonstrated that the knee SSM model was consistent with the real healthy model in terms of shape.The results provide a reference for the design of knee SSM-based prostheses.

Objective To establish a finite element model of the T2-L5 thoracolumbar spine and verify its validity,to provide numerical model support for exploring the dynamic response characteristics and injury mechanism under spinal impact loads.Methods A three-dimensional(3D)finite element model of the T2-L5 thoracolumbar spine was established based on CT scanning data.The load-rotation angle curve of the T12-L1 segment under different moments(flexion,extension,rotation,and lateral bending conditions)was calculated and compared with the data reported in the literature.Free-fall loads at different heights were applied to the finite element models of the T2-6,T7-11,and T12-L5 spine.The peak axial force and bending moment were obtained by finite element simulation analysis and compared with data reported in the literature.Results The maximum rotation angle of the T12-L1 finite element model was-2.24°-1.55° under moments in different directions,which was in good agreement with the literature data.The peak axial force of T2-6,T7-11,and T12-L5 spine finite element models subjected to different free-fall loads was 1.7-5.3 kN,1.3-5.5 kN,and 1.3-7.5 kN respectively,which were within the error range reported in the literature.Stress nephograms of the spine and intervertebral discs showed that the vertebral body was first stressed from the outer edge.The intervertebral disc was subjected to the main load by the nucleus pulposus,consistent with the actual spinal injury mechanism.Conclusions The T2-L5 spine model established in this study can correctly simulate the biomechanical behavioral characteristics of the spine under different working conditions,and the analysis results are effective.

Objective To study the effect of pain on the lumbar and hip joint moments in patients with lumbar disc herniation(LDH)while sitting and standing.Methods Dynamic data from 20 healthy controls and 20 patients with LDH were collected using an AMTI dynamometer.The differences in moments between the lumbar spine and hip joints in the sagittal and coronal planes for the two groups of subjects performing sitting-standing tasks were analyzed using statistical parameter mapping(SPM).Results Compared to the healthy control group,the LDH group showed a significant increase in the maximum lumbar flexion moment and the maximum hip adduction moment from standing to sitting(P＜0.05).SPM analysis showed that during the initial phase of standing(37％-42％),the hip abduction moment of the LDH group was significantly greater than that of the healthy control group(P=0.007).Conclusions Subjects with LDH have an unstable lumbar spine and pelvis during sitting and standing,especially at the stationary stage,which makes it difficult to achieve balance in their body.Therefore,increasing the hip abduction moment is necessary to maintain pelvic stability.During clinical evaluation and treatment,emphasis should be placed on the stable function of the spine and pelvis.

Objective To investigate the biomechanical properties of a novel sacroiliac lag screw with a spiral blade.Methods Percutaneous sacroiliac lag screws were used as the controls.Polyurethane material was used to simulate the trabecular bone,and the pullout resistance performance was tested on an Instron mechanical testing machine.Subsequently,pelvic specimens were utilized to analyze the static stiffness and dynamic stability of the novel sacroiliac lag screw in repairing sacroiliac joint injuries under normal standing conditions,with normal pelvis,single-sided sacroiliac joint injury pelvis,percutaneous sacroiliac lag screw-single screw repair,and percutaneous sacroiliac lag screw-double screw repair as controls.Results The damage to the polyurethane material after screw extraction was smaller in the novel sacroiliac lag screw group.The average effective holding displacement of the novel sacroiliac lag screw was significantly greater than that of the percutaneous sacroiliac lag screw(P＜0.05).However,the maximum resistance to the pullout force for the percutaneous sacroiliac lag screw was significantly higher than that for the novel sacroiliac lag screw(P＜0.05).The stiffness after repair of sacroiliac joint injuries was significantly higher when using a single sacroiliac lag screw than when using two percutaneous sacroiliac lag screws(P＜0.05).The displacement amplitude was the highest in the sacroiliac joint injury group,followed by that in the normal group.The displacement amplitudes in the other groups were similar;however,the differences were statistically significant(P＜0.05).The dynamic stability of the sacroiliac lag screw repair group was the best,slightly better than that of the percutaneous sacroiliac lag screw-double screw repair group,and the dynamic stability of the sacroiliac joint injury group was the worst.The novel sacroiliac lag screw effectively repaired the sacroiliac joint injuries.Conclusions The novel sacroiliac lag screw can effectively hold the trabecular bone and has practical clinical utility.

Objective To establish a finite element model of the hallux valgus foot and study the stress and displacement changes in the first and second rays of the hallux valgus under different tensile forces.Methods Foot CT images of a patient with hallux valgus were imported into Mimics to reconstruct a three-dimensional(3D)skeletal model of the foot.The 3-matic software was used to mesh the reconstructed model and generate the volume mesh.The optimized model was imported into ANSYS for finite element analysis.The relationship between the tensile forces and the stress/displacement of the first and second rays of the hallux valgus was verified by changing the size and direction of the tensile forces.Results Tensile forces of different magnitudes and directions were applied to the first proximal phalanx.When the force was less than 12 N,with an increase in tension,the displacement of the first phalange changed more significantly.For every 2 N increase in tension,the displacement increased by approximately 1 mm.When the force was greater than 12 N,with an increase in tension,the stress on the first phalange increased,whereas the displacement only changed slightly.In addition,when the magnitude of the force remained unchanged at 12 N and the direction of the force changed at intervals of 15°,the stress and stress distributions of the first and second rays changed with direction,and the displacement also changed accordingly.When the direction of the force was perpendicular to that of the second phalanx,the displacement of the first phalanx increased.Conclusions Finite element analysis technology can vividly and accurately analyze the stress and displacement changes of the first and second rays of hallux valgus under different tensile forces,and it lays a foundation for the design of hallux valgus orthoses.