BACKGROUND:Lumbar degenerative disease is a disease of the musculoskeletal system that primarily affects the intervertebral structures,and the disease is treated with lumbar fusion and disc replacement.OBJECTIVE:To conduct comparative analysis of the differences between lumbar fusion,mechanical lumbar disc prosthesis replacement,and viscoelastic lumbar disc prosthesis replacement.METHODS:The computerized tomography images of a healthy adult were used to construct a finite element model of the L2-L5 normal lumbar spine with Mimic,Geomagic,and Ansys software.The equipment required for lumbar fusion and lumbar spine replacement was constructed using modeling software,and the L3-L4 segment of the lumbar spine was processed according to the surgical requirements for lumbar fusion and intervertebral disc replacement,creating the corresponding finite element model.Specific boundary conditions were applied to extract the mobility of each lumbar spine segment,the stresses on the neighboring intervertebral discs,and the stresses on the prosthesis lining.RESULTS AND CONCLUSION:(1)Compared with the preoperative period,the maximum stress in the upper neighboring discs increased by 64.09％and 39.79％in the forward flexion and lateral bending states if the original mobility was maintained after lumbar fusion surgery.The maximum stress in the lower neighboring discs increased by 24.39％and 20.98％in forward flexion and lateral bending.This suggested that the upper adjacent discs would suffer greater stress changes than the lower adjacent discs during heavy physical labor.(2)Disc replacement did not show significant changes in adjacent disc stress,with mechanical prosthesis replacement slightly reducing adjacent disc stress,while viscoelastic prosthesis replacement was more in line with the biological properties of the disc,with maximum adjacent disc stress similar to that of the preoperative period.(3)In terms of stability,the mechanical prosthesis replacement segment showed a 51.67％increase in range of motion in the lateral bending state and a 53.27％increase in range of motion in the posterior extension state,whereas the viscoelastic prosthesis was better able to maintain mobility in the replacement segment.(4)In addition,the stresses in the liner of the mechanical prosthesis were mainly concentrated in the edge region,and this stress distribution may lead to edge wear and thus affect the service life of the prosthesis.

BACKGROUND:Steroid-induced osteonecrosis of the femoral head(SANFH)is a severe orthopedic disease characterized by interruption of the blood supply to the femoral head and necrosis of subchondral bone,leading to joint dysfunction.Long-term use of glucocorticoids is the main cause of SANFH,and its pathogenesis involves multiple factors,including intravascular coagulation and osteocyte apoptosis.Vascular endothelial growth factor A(VEGF-A),as a key angiogenic factor,has potential value in the treatment of SANFH.OBJECTIVE:To summarize the mechanisms of action of VEGF-A in SANFH,including its progress in promoting angiogenesis,anti-apoptosis,and lipid metabolism regulation,and to discuss the prospects for clinical application of VEGF-A targeted therapy.METHODS:Literature related to VEGF-A targeted regulation of angiogenesis in the treatment of SANFH was identified through searches of PubMed,Web of Science,CNKI,and WanFang databases from database inception to November 2024.After quality assessment,71 articles were selected,data were extracted by independent researchers,and disagreements were resolved through group discussions.RESULTS AND CONCLUSION:(1)VEGF-A binds to its receptors VEGFR-1 and VEGFR-2,activating downstream signaling pathways that promote the proliferation,migration,and angiogenesis of endothelial cells.Therefore,it can promote the formation of collateral circulation and improve blood supply to the area of bone necrosis.(2)Reduced expression of VEGF-A may lead to a decrease in the number of blood vessels within bone tissue,exacerbating the ischemic state of the femoral head.Furthermore,VEGF-A has anti-apoptotic effects and reduce apoptosis in osteocytes and bone marrow cells,thus protecting bone tissue.(3)The role of VEGF-A in regulating lipid metabolism and inflammatory responses,as well as promoting the osteogenic differentiation of bone marrow mesenchymal stem cells,provides a new perspective for the treatment of SANFH.(4)The development of VEGF-A protein delivery systems,such as lipid nanoparticles and exosome-based delivery systems,offers new possibilities for the clinical application of VEGF-A.(5)The research progress of VEGF-A in SANFH treatment has laid a solid foundation for the development of new treatment strategies and has opened up new avenues for future research directions and clinical applications.(6)With further clarification of the mechanisms of action of VEGF-A and continuous advancements in delivery technologies,more effective treatments will be provided for SANFH patients,improving their prognosis.

BACKGROUND:The pathogenesis of steroid-induced osteonecrosis of the femoral head is complex,involving vascular endothelial injury,osteocyte apoptosis,inflammatory responses,and bone metabolism disorders.MicroRNAs(miRNAs),as key regulators of gene expression,play an important role in steroid-induced osteonecrosis of the femoral head.OBJECTIVE:To comprehensively analyze the regulatory role of miRNAs in steroid-induced osteonecrosis of the femoral head and to evaluate their potential as biomarkers and therapeutic tools.METHODS:Relevant literature was retrieved from PubMed,Web of Science,CNKI,and WanFang databases using specific keywords,and articles were selected based on the inclusion and exclusion criteria.By reading titles,abstracts,or full texts,articles with poor relevance or repetitive content were excluded,and 76 articles were finally included for analysis.RESULTS AND CONCLUSION:miRNAs regulate gene expression by binding to the 3'untranslated region of target mRNAs,affecting cell differentiation,proliferation,apoptosis,and stress responses.Specific miRNAs such as miR-33-5p,miR-99a,miR-106b-5p,miR-155,miR-146a,and miR-21 play a central regulatory role in vascular injury,inflammatory responses,osteocyte differentiation,and apoptosis in steroid-induced osteonecrosis of the femoral head.Additionally,the expression patterns of miRNAs are closely related to the pathogenesis of steroid-induced osteonecrosis of the femoral head,showing potential as biomarkers.Although miRNAs shows great potential as biomarkers in therapeutic strategies,the current limitation of sample size and lack of multi-population validation restrict the universality and reliability of the results.Moreover,the efficacy and safety of miRNA therapeutic strategies(including off-target effects and delivery issues)remain major challenges in realizing clinical applications.

OBJECTIVE:It has been confirmed that neuromodulation technology can improve the clinical symptoms of patients with Parkinson's disease,and there are differences in the efficacy of different neuromodulation stimulation methods.Herein,a network meta-analysis was used to evaluate the efficacy of different neuromodulation stimulation modalities in improving non-motor symptoms such as sleep disorders and depression and anxiety in patients with Parkinson's disease,thereby exploring the optimal neuromodulation stimulation regimen.METHODS:The Chinese Biomedical Literature Database,WanFang Database,VIP Database,CNKI Database,Web of Science,PubMed,The Cochrane Library,and EMbase databases were searched for randomized controlled trials on neuromodulation techniques to improve sleep disorders,depression and anxiety in patients with Parkinson's disease.The control group was treated with conventional treatments(drugs,conventional rehabilitation therapy,etc.)or sham stimulation,and the experimental group was supplemented with neuromodulation technology on the basis of the control group.The quality of the included studies was evaluated using the PEDro scale and the deviation risk assessment tool recommended by the Cochrane Collaboration.RevMan 5.4 and Stata 17.0 were used for network meta-analysis of the four outcomes(sleep disorders,anxiety symptoms,depressive symptoms,and quality of life).RESULTS:(1)Twenty-nine randomized controlled trials involving six neuromodulation stimulation modalities were included.These modalities were transcranial direct current stimulation,high-frequency repetitive transcranial magnetic stimulation,low-frequency repetitive transcranial magnetic stimulation,deep brain stimulation of the subthalamic nucleus,deep brain stimulation of the globus pallidus,multi-target deep brain stimulation.(2)The results of network meta-analysis showed that compared with conventional treatment,transcranial direct current stimulation[standardized mean difference(SMD)=-2.57,95％confidence interval(CI)=-4.52 to-0.63,P＜0.05)had the best effect in improving sleep disorders in patients with Parkinson's disease.In terms of improving depressive symptoms,deep brain stimulation of the globus pallidus(SMD=-1.00,95％CI=-1.87 to-0.14,P＜0.05)had the best effect,followed by low-frequency repetitive transcranial magnetic stimulation(SMD=-0.91,95％CI=-1.60 to-0.23,P＜0.05),deep brain stimulation of the subthalamic nucleus(SMD=-0.82,95％CI=-1.56 to-0.08,P＜0.05),and high-frequency repetitive transcranial magnetic stimulation(SMD=-0.75,95％CI=-0.97 to-0.53,P＜0.05).In terms of improving anxiety symptoms,high-frequency repetitive transcranial magnetic stimulation(SMD=-0.86,95％CI=-1.54 to-0.18,P＜0.05)had the best effect.In terms of improving the quality of life,deep brain stimulation of the globus pallidus(SMD=-0.79,95％CI=-1.55 to-0.04,P＜0.05)had the best efficacy,followed by high-frequency repetitive transcranial magnetic stimulation(SMD=-0.63,95％CI=-0.90 to-0.36,P＜0.05)and transcranial direct current stimulation(SMD=-0.50,95％CI=-0.80 to-0.19,P＜0.05).CONCLUSION:Neuromodulation technology has significant efficacy in improving non-motor symptoms in patients with Parkinson's disease.Transcranial direct current stimulation has the best efficacy in improving sleep disorders,deep electrical stimulation of the medial cerebral part of the globus pallidus has the best efficacy in improving depressive symptoms,high-frequency repetitive transcranial magnetic stimulation has the best efficacy in improving anxiety symptoms,and deep electrical stimulation of the globus pallidus has the best efficacy in improving quality of life.

BACKGROUND:Previous studies have found that neuronal damage caused by continuous excessive fluoride exposure is related to Ca2+overload,but the mechanism of Ca2+flow conversion between intracellular calcium stores and cell apoptosis damage is still unclear.OBJECTIVE:To investigate the effect of fluoride exposure on Ca2+transport channel proteins and apoptosis levels in the mitochondria-associated endoplasmic reticulum membrane of primary cultured neural cells.METHODS:Primary nerve cells of neonatal SD rats were cultured in vitro and identified by immunofluorescence staining with neuronal nucleus-specific antibody up to day 7.The nerve cells were divided into control group(containing 0 mmol/L sodium fluoride),low fluoride group(containing 0.5 mmol/L sodium fluoride),and high fluoride group(containing 1 mmol/L sodium fluoride).The cell morphological changes were observed by light microscope 24 hours after fluorine exposure.The expression levels of apoptosis-related protein BAX/BCL-2 and calcium transfer-related pathways VDAC1,GRP 75,and IP3R were detected using western blot assay.The expression levels of VDAC1,GRP 75,and IP3R mRNA were detected by RT-PCR.Ca2+levels were detected by Rhood-2AM Ca2+probe.Mitochondrial membrane potential detection kit was used to detect the change in mitochondrial membrane potential.The level of apoptosis was determined by flow cytometry and TUNEL staining.RESULTS AND CONCLUSION:(1)The purity of neurons cultured on day 7 had been determined to be over 90％,with few impurities,good growth status,and tight cell network connections,meeting the requirements of subsequent experiments.(2)Compared with the control group,growth of neural cell clusters in the low-fluoride group and the high-fluoride group increased;the processes were broken;the cell body was rounded,and the connection network between cells was destroyed.Compared with the low-fluoride group,the cell damage changes in the high-fluoride group were more obvious.(3)Compared with the control group,the protein expressions of VDAC1,GRP75,and IP3R were increased in the low-fluoride group and the high-fluoride group(P＜0.05),and the ratio of apoptosis-related protein BAX/BCL-2 was increased(P＜0.05).Compared with the control group,the expression of VDAC1 and GRP75 mRNA in the low-fluoride group was significantly increased(P＜0.05);the expression levels of VDAC1,GRP75,and IP3R mRNA in the high-fluoride group were significantly increased(P＜0.01).(4)The level of cell apoptosis increased significantly after fluoride exposure,and the high-fluoride group was significantly higher than the control and low-fluoride groups(P＜0.01).(5)After fluoride exposure,the concentration of mitochondrial Ca2+in nerve cells increased significantly(P＜0.05),the mitochondrial membrane potential decreased(P＜0.01),and the degree of damage in the high-fluoride group was more obvious(P＜0.05).The results show that fluoride exposure impairs the morphological structure of primary neural cells,resulting in upregulation of Ca2+transfer pathway protein expression between the endoplasmic reticulum and mitochondria,mitochondrial Ca2+overload,mitochondrial damage,and increased levels of apoptosis.

BACKGROUND:Choline kinase alpha is a key enzyme in phospholipid metabolism,involved in the synthesis of phosphatidylcholine,and plays an important role in maintaining cell membrane integrity and signal transduction.Research has shown that choline kinase alpha is highly expressed in various tumors and is closely related to cell proliferation,metabolic reprogramming,and tumor progression.As a potential therapeutic target,the role of choline kinase alpha in tumor metabolism and mitochondrial function still needs further exploration.OBJECTIVE:To evaluate the effects and the underlying mechanisms of choline kinase alpha on the proliferation and apoptosis of glioma U87MG and U251 cells.METHODS:Short hairpin RNA of choline kinase alpha and its empty vector control were transfected into U87MG and U251 glioma cells.Mitochondrial morphology was observed by transmission electron microscopy.Mitochondrial structure and functional protein levels were assessed by western blot assay.Reactive oxygen species levels in cells were measured using a reactive oxygen species fluorescent probe.Mitochondrial membrane potential was assessed with a JC-1 assay.Intracellular adenosine triphosphate levels were measured by chemiluminescence.Cell proliferation was evaluated using a CCK-8 assay.Apoptosis levels were analyzed by flow cytometry.The mitochondrial fission inhibitor Mdivi-1 was used to protect the mitochondrial function of the choline kinase α-silenced lentiviral cells.Finally,U87MG cells were subcutaneously injected to construct a subcutaneous tumor model in nude mice.The tumor growth in nude mice was observed before and after choline kinase alpha silencing and after the use of the mitochondrial fission inhibitor Mdivi-1.RESULTS AND CONCLUSION:(1)Compared with the empty control group,the mitochondria of U87MG and U251 cells in the choline kinase alpha silencing lentivirus group exhibited significant structural abnormalities in mitochondria,such as vacuolization and cristae disruption.The expressions of mitochondrial structure and function-related proteins TOM20,ACO2,and ATP5A were significantly decreased(P＜0.01,P＜0.001),the expression of SOD2 was significantly increased(P＜0.01,P＜0.000 1),the fluorescence intensity of reactive oxygen species was significantly increased(P＜0.01),the mitochondrial membrane potential and adenosine triphosphate level were significantly decreased(P＜0.01,P＜0.001),the cell proliferation ability was reduced(P＜0.01),and the apoptosis level was increased(P＜0.001).(2)Following Mdivi-1 treatment,the fluorescence intensity of reactive oxygen species in U87MG and U251 cells decreased(P＜0.05,P＜0.01),mitochondrial membrane potential and adenosine triphosphate levels were significantly restored(P＜0.05,P＜0.01,P＜0.001),cell proliferation ability was improved(P＜0.05,P＜0.01),and apoptosis level was decreased(P＜0.05).(3)In addition,the in vitro subcutaneous tumor formation experiment of nude mice showed that compared with the empty control group,the mass and growth rate of subcutaneous tumors formed by U87MG cells in the choline kinase alpha silencing lentivirus group were significantly reduced(P＜0.000 1).After Mdivi-1 treatment,the mass and growth rate of tumors were significantly increased(P＜0.000 1).(4)The results show that choline kinase alpha silencing affects the proliferation and apoptosis of glioma cells by inducing mitochondrial dysfunction.

BACKGROUND:Extracellular vesicles mediate intercellular signal transduction through the proteins,nucleic acids,and lipids they carry,thereby influencing the function of target cells.This vesicle-mediated communication mechanism is involved in regulating female reproductive development.OBJECTIVE:To summarize and analyze the regulatory roles of extracellular vesicle-mediated intercellular communication in female reproductive development.METHODS:A search was conducted in the PubMed database using the search terms"extracellular vesicles,exosomes,reproduction,maternal-embryo communication,maternal-fetal crosstalk,embryo implantation,endometrium,oviduct,follicle."The initial screening was carried out by reading the titles and abstracts of the literature,and then the literature with poor relevance to the research purpose,outdated content,and duplication was excluded according to the inclusion and exclusion criteria.Ultimately,69 relevant articles were included for comprehensive analysis.RESULTS AND CONCLUSION:Extracellular vesicles play a crucial role in key processes of female reproductive development,from folliculogenesis to implantation.(1)Extracellular vesicles mediate intercellular communication within the follicle,particularly the interactions between oocytes and follicular cells,which are essential for follicle development and maturation.(2)Extracellular vesicles and their contents facilitate interactions between the embryo and the fallopian tube,influencing the trajectory of embryonic development.(3)Extracellular vesicles and their contents promote implantation by mediating bidirectional communication between the embryo and the endometrium.Uterine-derived extracellular vesicles regulate processes such as embryo adhesion,invasion,and decidualization,while embryo-derived extracellular vesicles modulate endometrial receptivity,convey embryonic signals,and adjust the endometrial microenvironment.Studying the roles of extracellular vesicles in female reproductive development can provide valuable insights into the mechanisms of infertility and support the development of new therapeutic strategies.

BACKGROUND:Magnetic nanomaterials,as a hot topic in the biomedical field in recent years,are often used to enhance the targeted delivery of drugs to the affected area.OBJECTIVE:To investigate the effects of magnetic nano drug carriers on skeletal muscle injury markers and inflammatory responses in rats with sports injuries.METHODS:Magnetic nanoparticles were prepared.A total of 88 male SD rats were randomly divided into a blank group(n=8),an injury control group(n=32),a Yunnan Baiyao group(n=24),and a magnetic nano-drug carrier group(n=24)by using a random number table method.The latter three groups were modeled with exercise-induced muscle injury(treadmill slope of-16°,running speed of 16 m/min,and training time of 120 min).Immediately after exercise,after verifying the success of the model,Yunnan Baiyao patch was applied to the gastrocnemius muscle of the rats in the Yunnan Baiyao group.Yunnan Baiyao patch loaded with magnetic nanoparticles was applied to the gastrocnemius muscle of the rats in the magnetic nano-drug carrier group.At 24,48,and 120 hours after exercise,blood was drawn from the abdominal aorta of rats to detect the activities of creatine kinase and lactate dehydrogenase,as well as the levels of myoglobin,interleukin-6,and tumor necrosis factor-α.Hematoxylin-eosin staining was used to observe the infiltration of inflammatory cells in the gastrocnemius muscle.RESULTS AND CONCLUSION:(1)Compared with the blank group,the levels of myoglobin,creatine kinase,lactate dehydrogenase and tumor necrosis factorα in the injury control group at 24,48 and 120 hours after exercise were increased(P＜0.05),and the level of interleukin 6 at 24 and 120 hours after exercise was increased(P＜0.05).Compared with the injury control group,the level of myoglobin in the Yunnan Baiyao group at 24 and 48 hours after exercise was decreased(P＜0.05),the activities of creatine kinase and lactate dehydrogenase at 24,48 and 120 hours were decreased(P＜0.05),and the levels of interleukin 6 and tumor necrosis factor α at 120 hours after exercise were decreased(P＜0.05).Compared with the Yunnan Baiyao group,the level of myoglobin in the magnetic nano-drug carrier group at 24 and 48 hours after exercise was decreased(P＜0.05),the activities of creatine kinase and tumor necrosis factor α at 48 and 120 hours after exercise were decreased(P＜0.05),and the lactate dehydrogenase activity was reduced(P＜0.05).(2)Hematoxylin-eosin staining showed that a large number of inflammatory cells infiltrated in the muscle fibers of the injury control group 24 hours after exercise,and then the inflammatory cell infiltration gradually decreased,and the local damaged muscle fibers began to regenerate 120 hours after exercise.A large number of inflammatory cells infiltrated in the muscle fibers of the Yunnan Baiyao group and the magnetic nano-drug carrier group 24 hours after exercise,and then the inflammatory cell infiltration gradually decreased,and the damaged muscle fibers were regenerating 120 hours after exercise,and there was no significant difference from the blank group.(3)The results show that Yunnan Baiyao patch combined with magnetic nanoparticles can accelerate the recovery of exercise-induced muscle injury in rats,and the effect is better than that of Yunnan Baiyao alone.

BACKGROUND:Promoting skin wound healing is a huge challenge facing global public health.To promote faster and higher-quality wound healing,it is necessary to explore more advantageous dressings to address this problem.OBJECTIVE:To investigate the hemostatic properties of acellular dermal matrix hydrogel and its effect on skin wound healing.METHODS:(1)Acellular dermal matrix hydrogel was prepared,and the differences in microscopic morphology and main components between it and acellular dermal matrix were analyzed.(2)Acellular dermal matrix hydrogel and chitosan hydrogel were used to cover the femoral artery puncture site of rats,and the bleeding quality and coagulation time were recorded.Acellular dermal matrix hydrogel and chitosan hydrogel were mixed with rat anticoagulated blood,and the coagulation index within 30 minutes was detected.(3)A full-thickness skin defect model with a diameter of 12 mm was made on the back of 18 SD rats,and they were randomly divided into 3 groups,with 6 rats in each group:the model group used PBS to clean the wound,and the control group and the experimental group used chitosan hydrogel and acellular dermal matrix hydrogel to cover the wound,respectively.The hydrogel dressing was changed every day,and the treatment was continued for 14 days,and the wound healing was observed.On day 3 after modeling,immunofluorescence staining of inducible nitric oxide synthase(M1 macrophages)and CD206(M2 macrophages)was performed on the wound surface.On day 14 after modeling,hematoxylin-eosin staining,Masson staining,and CD31 immunohistochemical staining were performed on the wound surface.RESULTS AND CONCLUSION:(1)Scanning electron microscopy revealed that the acellular dermal matrix hydrogel had a porous structure,and the Fourier transform infrared spectrum showed that it had the same main components as the acellular dermal matrix.(2)Both acellular dermal matrix hydrogel and chitosan hydrogel had obvious hemostatic ability in vivo.In the in vitro coagulation experiments,the coagulation index of acellular dermal matrix hydrogel was significantly higher than that of chitosan hydrogel.(3)In the rat skin full-thickness defect model,both acellular dermal matrix hydrogel and chitosan hydrogel could improve the wound healing rate.Hematoxylin-eosin and Masson staining results showed that acellular dermal matrix hydrogel could reduce the infiltration of inflammatory cells in the center of the wound.Both acellular dermal matrix hydrogel and chitosan hydrogel could decrease scar width and increase collagen deposition rate.CD31 immunohistochemical staining results showed that both hydrogels could promote angiogenesis in the wound site.Immunofluorescence staining results showed that both hydrogels could reduce the proportion of M1 macrophages and increase the proportion of M2 macrophages,and the effect of acellular dermal matrix hydrogel was stronger than that of chitosan hydrogel.(4)The results show that the acellular dermal matrix hydrogel has good hemostatic properties and the ability to promote wound healing.

BACKGROUND:Lumbar degenerative disease is a disease of the musculoskeletal system that primarily affects the intervertebral structures,and the disease is treated with lumbar fusion and disc replacement.OBJECTIVE:To conduct comparative analysis of the differences between lumbar fusion,mechanical lumbar disc prosthesis replacement,and viscoelastic lumbar disc prosthesis replacement.METHODS:The computerized tomography images of a healthy adult were used to construct a finite element model of the L2-L5 normal lumbar spine with Mimic,Geomagic,and Ansys software.The equipment required for lumbar fusion and lumbar spine replacement was constructed using modeling software,and the L3-L4 segment of the lumbar spine was processed according to the surgical requirements for lumbar fusion and intervertebral disc replacement,creating the corresponding finite element model.Specific boundary conditions were applied to extract the mobility of each lumbar spine segment,the stresses on the neighboring intervertebral discs,and the stresses on the prosthesis lining.RESULTS AND CONCLUSION:(1)Compared with the preoperative period,the maximum stress in the upper neighboring discs increased by 64.09％and 39.79％in the forward flexion and lateral bending states if the original mobility was maintained after lumbar fusion surgery.The maximum stress in the lower neighboring discs increased by 24.39％and 20.98％in forward flexion and lateral bending.This suggested that the upper adjacent discs would suffer greater stress changes than the lower adjacent discs during heavy physical labor.(2)Disc replacement did not show significant changes in adjacent disc stress,with mechanical prosthesis replacement slightly reducing adjacent disc stress,while viscoelastic prosthesis replacement was more in line with the biological properties of the disc,with maximum adjacent disc stress similar to that of the preoperative period.(3)In terms of stability,the mechanical prosthesis replacement segment showed a 51.67％increase in range of motion in the lateral bending state and a 53.27％increase in range of motion in the posterior extension state,whereas the viscoelastic prosthesis was better able to maintain mobility in the replacement segment.(4)In addition,the stresses in the liner of the mechanical prosthesis were mainly concentrated in the edge region,and this stress distribution may lead to edge wear and thus affect the service life of the prosthesis.