BACKGROUND:Developmental dysplasia of hip causes groin pain in patients with prolonged activity or standing due to the presence of deformities of the acetabulum and femoral head in terms of structure,size and orientation,and if not effectively treated,patients' normal activities will be severely limited.OBJECTIVE:Finite element model of the hip joint of solid-liquid biphase fiber reinforced cartilage based on FEBio was established to explore the biomechanical properties of the cartilage for patients with developmental dysplasia of hip and the normal hip joint.METHODS:A patient with developmental dysplasia of hip and a normal volunteer were chosen to build their left hip models including left pelvis,left femur,and cartilage attached thereto. The solid-liquid biphase fiber reinforced cartilage of normal hip was verified to be effective. The cartilage equal contact stress,fluid pressure,solid effective stress,and fluid support rate differences between the developmental dysplasia of hip patients hip and the normal one in the case of one leg of static load (2130 N) were compared after establishing finite element models of developmental dysplasia of hip patients.RESULTS AND CONCLUSION:(1) Compared with the finite element results of the normal hip model,the cartilage contact position of developmental hip dysplasia patient hip showed obvious edge contact,the peak contact stress (3.86 Mpa) and peak fluid pressure (3.76 Mpa) were both higher than normal hip model. (2) After 1500 s (stable load-bearing capacity),peak contact stress and peak fluid pressure in both models decreased,but the cartilage contact position of developmental hip dysplasia patient hip moved from the edge of cartilage to the center,and fluid support rate decreased from 97.41％ to 91.08％. The fluid support rate in normal hip was decreased by 0.58％ from 95.24％ to 94.66％. (3) It is indicated that under the physiological load of standing on one leg,the cartilage of developmental dysplasia of hip patients showed obvious edge load,and the decrease of peak contact stress,fluid pressure,and fluid formation rate was greater than that of normal cartilage. Considering the solid-liquid biphasic fiber reinforcement characteristics of cartilage,it is of great clinical significance to evaluate the biomechanical properties of hip cartilage in developmental dysplasia of hip patients,to understand the pathophysiological mechanism of developmental dysplasia of hip,and make preoperative plan.

Objective To investigate the effects of patient bone mass differences on the stability of unicondylar knee arthroplasty(UKA)prostheses.Methods A UKA finite element model was established to quantify the effects of five different bone quality conditions on the proximal tibial von Mises stress,bone-prosthesis fixation interface contact stress,and bone-prosthesis fixation interface micromotion,using the medial knee force and joint motion predicted by the individualized UKA musculoskeletal multibody dynamics model as boundary conditions.Results The influences of bone strength on the proximal tibia von Mises stress and bone-prosthesis fixation interface contact stress were not obvious,and the difference in peak values of the proximal tibia von Mises stress between two groups of models with the largest difference in bone strength was not more than 5％,and the difference in peak values of the bone-prosthesis fixation interface contact stress was only 2.37 MPa.However,the influence of bone strength on the bone-prosthesis fixation interface micromotion was significant,and the weaker bones were more prone to cause the bone-prosthesis fixation interface micromotion.However,bone strength had a significant effect on the bone-prosthesis fixation interface micromotion,and weak bone was more likely to cause changes in the bone-prosthesis fixation interface micromotion.Compared to patients with the neutral bone quality,the prosthesis fixation interface micromotion increased by 84.67％at 20％gait cycles for patients with the weakest bone quality.Conclusions UKA patients with a weaker bone quality have a higher risk of prosthesis loosening.It is recommended that surgeons should carefully choose their surgical strategy in order to reduce the rate of postoperative revision in UKA.

Objective To investigate the effects of patient bone mass differences on the stability of unicondylar knee arthroplasty(UKA)prostheses.Methods A UKA finite element model was established to quantify the effects of five different bone quality conditions on the proximal tibial von Mises stress,bone-prosthesis fixation interface contact stress,and bone-prosthesis fixation interface micromotion,using the medial knee force and joint motion predicted by the individualized UKA musculoskeletal multibody dynamics model as boundary conditions.Results The influences of bone strength on the proximal tibia von Mises stress and bone-prosthesis fixation interface contact stress were not obvious,and the difference in peak values of the proximal tibia von Mises stress between two groups of models with the largest difference in bone strength was not more than 5％,and the difference in peak values of the bone-prosthesis fixation interface contact stress was only 2.37 MPa.However,the influence of bone strength on the bone-prosthesis fixation interface micromotion was significant,and the weaker bones were more prone to cause the bone-prosthesis fixation interface micromotion.However,bone strength had a significant effect on the bone-prosthesis fixation interface micromotion,and weak bone was more likely to cause changes in the bone-prosthesis fixation interface micromotion.Compared to patients with the neutral bone quality,the prosthesis fixation interface micromotion increased by 84.67％at 20％gait cycles for patients with the weakest bone quality.Conclusions UKA patients with a weaker bone quality have a higher risk of prosthesis loosening.It is recommended that surgeons should carefully choose their surgical strategy in order to reduce the rate of postoperative revision in UKA.

Prosthesis loosening is the leading cause of postoperative revision in unicompartmental knee arthroplasty (UKA). The deviation of medial and lateral translational installation of the prosthesis during surgery is a common clinical phenomenon and an important factor in increasing the risk of prosthesis loosening. This study established a UKA finite element model and a bone-prosthesis fixation interface micromotion prediction model. The predicted medial contact force and joint motion of the knee joint from a patient-specific lower extremity musculoskeletal multibody dynamics model of UKA were used as boundary conditions. The effects of 9 femoral component medial and lateral translational installation deviations on the Von Mises stress of the proximal tibia, the contact stress, and the micro-motion of the bone prosthesis fixation interface were quantitatively studied. It was found that compared with the neutral position (a/A of 0.492), the lateral translational deviation of the femoral component significantly increased the tibial Von Mises stress and the bone-prosthesis fixation interface contact stress. The maximum Von Mises stress and the maximum contact stress of the fixation interface increased by 14.08% and 143.15%, respectively, when a/A was 0.361. The medial translational deviation of the femoral component significantly increased the bone-prosthesis fixation interface micro-motion. The maximum value of micromotion under the conditions of femoral neutral and medial translation deviation was in the range of 20-50 μm, which is suitable for osseointegration. Therefore, based on considerations such as the micromotion range suitable for osseointegration reported in the literature, the risk of reducing prosthesis loosening, and factors that may induce pain, it is recommended that clinicians control the mounting position of the femoral component during surgery within the safe range of 0-4 mm medial translation deviation.
Humans ; Arthroplasty, Replacement, Knee/methods* ; Finite Element Analysis ; Biomechanical Phenomena ; Knee Prosthesis ; Tibia/surgery* ; Femur/surgery* ; Stress, Mechanical ; Prosthesis Failure ; Knee Joint/surgery* ; Prosthesis Design

Although metal blocks have been widely used for reconstructing uncontained tibial bone defects, the influence of their elastic modulus on the stability of tibial prosthesis fixation remains unclear. Based on this, a finite element model incorporating constrained condylar knee (CCK) prosthesis, tibia, and metal block was established. Considering the influence of the post-restraint structure of the prosthesis, the effects of variations in the elastic modulus of the block on the von Mises stress distribution in the tibia and the block, as well as on the micromotion at the bone-prosthesis fixation interface, were investigated. Results demonstrated that collision between the insert post and femoral prosthesis during tibial internal rotation increased tibial von Mises stress, significantly influencing the prediction of block elastic modulus variation. A decrease in the elastic modulus of the metal block resulted in increased von Mises stress in the proximal tibia, significantly reduced von Mises stress in the distal tibia, decreased von Mises stress of the block, and increased micromotion at the bone-prosthesis fixation interface. When the elastic modulus of the metal block fell below that of bone cement, inadequate block support substantially increased the risk of stress shielding in the distal tibia and fixation interface loosening. Therefore, this study recommends that biomechanical investigations of CCK prostheses must consider the post-constraint effect, and the elastic modulus of metal blocks for bone reconstruction should not be lower than 3 600 MPa.
Knee Prosthesis ; Humans ; Finite Element Analysis ; Tibia/surgery* ; Elastic Modulus ; Arthroplasty, Replacement, Knee/methods* ; Stress, Mechanical ; Metals ; Prosthesis Design ; Knee Joint/surgery* ; Biomechanical Phenomena

BACKGROUND:Developmental dysplasia of hip causes groin pain in patients with prolonged activity or standing due to the presence of deformities of the acetabulum and femoral head in terms of structure,size and orientation,and if not effectively treated,patients' normal activities will be severely limited.OBJECTIVE:Finite element model of the hip joint of solid-liquid biphase fiber reinforced cartilage based on FEBio was established to explore the biomechanical properties of the cartilage for patients with developmental dysplasia of hip and the normal hip joint.METHODS:A patient with developmental dysplasia of hip and a normal volunteer were chosen to build their left hip models including left pelvis,left femur,and cartilage attached thereto. The solid-liquid biphase fiber reinforced cartilage of normal hip was verified to be effective. The cartilage equal contact stress,fluid pressure,solid effective stress,and fluid support rate differences between the developmental dysplasia of hip patients hip and the normal one in the case of one leg of static load (2130 N) were compared after establishing finite element models of developmental dysplasia of hip patients.RESULTS AND CONCLUSION:(1) Compared with the finite element results of the normal hip model,the cartilage contact position of developmental hip dysplasia patient hip showed obvious edge contact,the peak contact stress (3.86 Mpa) and peak fluid pressure (3.76 Mpa) were both higher than normal hip model. (2) After 1500 s (stable load-bearing capacity),peak contact stress and peak fluid pressure in both models decreased,but the cartilage contact position of developmental hip dysplasia patient hip moved from the edge of cartilage to the center,and fluid support rate decreased from 97.41％ to 91.08％. The fluid support rate in normal hip was decreased by 0.58％ from 95.24％ to 94.66％. (3) It is indicated that under the physiological load of standing on one leg,the cartilage of developmental dysplasia of hip patients showed obvious edge load,and the decrease of peak contact stress,fluid pressure,and fluid formation rate was greater than that of normal cartilage. Considering the solid-liquid biphasic fiber reinforcement characteristics of cartilage,it is of great clinical significance to evaluate the biomechanical properties of hip cartilage in developmental dysplasia of hip patients,to understand the pathophysiological mechanism of developmental dysplasia of hip,and make preoperative plan.

Objective To establish different sleep deprivation models in zebrafish to provide reproducible and practical modeling reference solutions for basic research on insomnia.Methods Zebrafish insomnia models were induced by two interventions:continuous light(150 Lux)and light plus caffeine.The zebrafish were divided randomly into control,light,caffeine(100 μmol/L),and combined light and caffeine groups.The locomotor ability of zebrafish in each group was observed using open field and circadian rhythm behavioral experiments.The expression and secretion of related sleep genes and the neurotransmitter 5-hydroxytryptamine(serotonin;5-HT)were detected using quantitative polymerase chain reaction and enzyme-linked immunosorbent assay,respectively.Results Sleep time,resting time(during the day),and sleep rounds were significantly reduced(P＜0.01 or P=0.01)and the distance traveled was significantly increased in the light group compared with the control group(P＜0.01).The resting time(daytime)and sleep rounds were increased in the combined and caffeine groups(P＜0.01)compared with the control group.There was no significant difference in the activity distance between the combined and caffeine groups(P＞0.05).The percentages of swimming distance and swimming time in the central area were decreased in the light group compared with the control group(P＜0.05),and were both decreased in the caffeine group compared with the light group(P＜0.01).HT receptor 1Aa(HTR1aa)mRNA expression at 6:00.and 12:00 was up-regulated in the light group compared with the control group(P＜0.05),but there was no significant difference in HTR1ab mRNA levels between the light group and the combined group(P＞0.05).5-HT secretion was decreased in the light group at 6:00(P＜0.01)and at 12:00 compared with the control group.5-HT levels were reduced in both the light and combined groups(P＜0.01),and secretion levels in the light and combined groups were still lower than in the control group at 18:00.(P＜0.01).Conclusions Light alone is the best intervention for modeling long-lasting insomnia in zebrafish larvae.The responsible mechanisms may be related to the HTR1aa gene as well as biological factors such as 5-HT.

BACKGROUND:Unaccustomed exercise triggers skeletal muscle damage,but produces a specific training effect that reduces muscle re-injury to reduce pain-muscle memory. OBJECTIVE:Based on the etiology of delayed onset muscle soreness,to review the existence and possible mechanism of skeletal muscle memory in delayed onset muscle soreness and to present new insights into the prevention and treatment of delayed onset muscle soreness. METHODS:The first author searched in PubMed,Embase,Web of Science,CNKI and WanFang databases for relevant literature published from January 1990 to December 2022.The keywords were"DOMS,skeletal muscle memory,exercise skeletal muscle adaptation,repeat turn effect,exercise and autophagy,autophagy and inflammation"in English and Chinese,respectively.A total of 102 articles were finally included for review. RESULTS AND CONCLUSION:The etiology of delayed onset muscle soreness is currently believed to be an acute inflammatory response due to metabolic disorders,mechanical injury and oxidative stress,while exercise-induced skeletal muscle memory can reduce delayed onset muscle soreness and exercise re-injury.When the duration,frequency and intensity of centrifugal training are gradually increased,symptoms of the injury can be minimized or even avoided.Therefore,based on the mechanism of exercise-induced skeletal muscle memory,it is the future research direction to find more effective ways to prevent and alleviate exercise-induced muscle injury.This review aims to(1)clarify the existence of exercise-induced skeletal muscle memory;(2)explore the possible mechanisms of exercise-induced skeletal muscle memory and propose the relationship between this memory and skeletal muscle autophagy;and(3)provide new strategies for the prevention and treatment of delayed onset muscle soreness by improving the level of skeletal muscle autophagy.

Objective For patient-specific open-wedge high tibial osteotomy(OWHTO),a novel anatomical fixation plate was designed,and the effects of geometric parameters and material selection on biomechanical fixation were studied.Methods A patient-specific OWHTO anatomical fixation plate was designed and constructed,and the effects of design parameters(thickness,width,and length of the fixation plate)and four different materials(stainless steel,titanium alloy,magnesium alloy,and PEEK)on the biomechanics of the OWHTO fixation system were studied using finite element analysis.The biomechanical differences between the anatomical fixation plate and TomoFix fixation plate were also compared.Results The thickness had a greater effect on the micromotion of the osteotomy space than the length and width of the fixation plate did.Titanium alloy or magnesium alloy fixation plates were more conducive than stainless steel and PEEK materials in obtaining reasonable stability and mechanical transfer simultaneously.Compared with that of the TomoFix plate,the maximum von Mises stress of the anatomical fixation plate was reduced by 13.5%;the maximum von Mises stress of the screws and tibia was increased by 9.8%and 18.4%,respectively;and the micromotion at the maximum osteotomy space cc was increased by 49.3%.Conclusions Anatomical fixation plates have a positive effect on reducing the stress-shielding effect and improving biomechanical properties under the premise of ensuring stability.This study provides a reference for the development of OWHTO anatomical fixation plates.