Objective: To investigate the effects of acetabular coverage on the initial stability of the cup during total hip arthroplasty in developmental dysplasia of hip. Methods: There were 50 fourth-generation synthetic hemi-pelvises. The different cup coverage rate (100% group, 70% group, 60% group, 50% group, 40% group) was created in pelvis with 10 specimens per group. The synthetic hemi-pelvis was fixed rigidly to a customized fixture which was placed on the testing table of the material testing machine. Pull-out and torque test were conducted by computer-control in torsion testing machine. Results: In the acetabular cup pull-out test, the average pull-out force for mode of failure in 100%, 70%, 60%, 50%, and 40% group was 1 560.4±438.7, 1 467.2±349.8, 1 137.8±427.4, 737.4±134.8, 506.6±119.0 N, respectively. The pull-out force was reduced gradually. The pull-out force in 100% group was significantly higher than that in 50% (P=0.004) and 40% (P=0.001) group. The pull-out force in 70% group was significantly higher than that in 50% group (P=0.002) and 40% group (P=0.000). The force in 40% group was significantly lower than that in 60% group (P=0.013) and 50% group (P=0.021). In the acetabular cup torque test, the average torque for mode of failure in 100%, 70%, 60%, 50%, and 40% group was 28.0±3.7, 17.0±2.2, 9.4±1.1, 7.6±1.1, 6.4±1.1 N·m, respectively. The torque was reduced gradually. The torque in 100% group was significantly higher than that in other groups (P<0.05). There was no significant difference between 50% and 40% group (P>0.05). The torque in other groups were similar (P>0.05). Conclusion The present biomechanical study showed that different acetabular cup coverage rate affected the initial stability of the cup. The highest initial stability was observed in the cup with a 100% of cup coverage rate. The cup could not obtain 100% coverage when with acetabular rim defect. We should try our best to make the cup coverage reach to 70%. The 70% coverage rate has sufficient initial stability to meet daily activities without increasing the cup loosening rate.

Objective:To explore the action mechanism of suppressing expression of mitogen- activated protein kinase 14（MAPK14）to alleviate glutamate excitatory toxicity and its neuronal protection effect.Methods:Lentivirus-mediated MAPK14 interference vector was synthetized by Shanghai Jikai Gene Chemical Technology Co.，Ltd. Astrocytes were obtained from SD rats 48 hours after birth，which were cultured in vitro and transfected by lentivirus-mediated transfection. According to the random number table，the cells were divided into three groups：（1）un-transfected group（normal group）with normal astrocytes and the cells were cultured in regular medium composed of Dulbecco's?modified Eagle's?medium（DMEM）；（2）negative control group with astrocytes transfected by MAPK14 no-loaded interference vector；（3）lentivirus transfected group with astrocytes transfected by MAPK14 interference vector. Seventy-two hours after transfection，astrocytes were co-cultured with neurons for 48 hours，and then they were cultured in a medium containing glutamate for 2 hours. The detection indexes included the optimal multiplicity of infection（MOI）value for astrocytes transfected by lentivirus vector，mRNA levels of MAPK14 and glial glutamate transporter 1（GLT-1）detected by rPCR 72 hours after transfection，protein levels of MAPK14 and GLT-1 detected by Western blot 72 hours after transfection，level of lactate dehydrogenase（LDH）and mortality of neurons measured by spectrophotometry and flow cytometry 2 hours after culturing in the medium with glutamate. Results:（1）The optimal MOI value for lentivirus transfecting astrocytes was 30，and astrocytes grew well after transfection.（2）Seventy-two after transfection，the mRNA level of MAPK14 in lentivirus transfected group（0.005 7±0.000 6）was significantly decreased as compared with un-transfected group（0.013 1±0.001 1）and negative control group（0.013 9±0.001 0）（ P<0.01），the mRNA level of GLT-1 in lentivirus transfected group（0.009 1±0.001 2）was not significantly changed as compared with un-transfected group（0.008 7±0.000 3）and negative control group（0.008 9±0.001 1）（ P>0.05）.（3）Seventy-two hours after transfection，the protein level of MAPK14 in lentivirus transfected group（0.29±0.04）was significantly decreased as compared with non-transfected group（0.61±0.05）and negative control group（0.63±0.01）（ P<0.01），the protein level of GLT-1 in lentivirus transfected group（0.73±0.06）was significantly increased as compared with un-transfected group（0.20±0.03）and negative control group（0.23±0.09）（ P<0.01）.（4）After astrocytes were co-cultured with neurons and subsequently cultured in the medium containing glutamate for 2 hours，the level of LDH in lentivirus transfected group［（109.67±2.40）U/L］was significantly lower than that in un-transfected group［（141.52±3.88）U/L］and negative control group［（141.29±3.61）U/L］（ P<0.01）. The mortality of neurons in lentivirus transfected group［（38.72±0.26）%］was significantly lower than that in un-transfected group［（52.94±1.36）%］and negative control group［（54.30±1.23）%］（ P<0.01）. Conclusions:The transfection with lentivirus-mediated MAPK14 interference vector can increase expression of GLT-1 in astrocytes to increase glutamate re-uptake and relieve the glutamate excitatory toxicity in neurons，which may provide a new experimental basis for future use of astrocyte gene regulation to alleviate neuronal injury caused by glutamate excitatory toxicity after traumatic brain injury.

BACKGROUND:With the aging of the global population,the incidence rate of osteoporosis is also increasing.It is very important to further understand its pathogenesis and propose new therapeutic targets.Recent studies have shown that ferroptosis is closely related to the pathogenesis of some bone diseases,such as inflammatory arthritis,osteoporosis and osteoarthritis. OBJECTIVE:To summarize the previous studies on the mechanism of ferroptosis in osteoporosis,so as to provide new therapeutic ideas and potential therapeutic targets for osteoporosis. METHODS:The first author used the computer to search the documents published from 2000 to 2022 in CNKI,WanFang,VIP,PubMed and Web of Science with the key words of"ferroptosis,osteoporosis,osteoblasts,osteoclasts,iron chelators,reactive oxygen species,nuclear factor erythroid 2-related factor 2,heme oxygenase-1,glutathione peroxidase 4,review"in Chinese and English.A total of 70 articles were finally included according to the inclusion criteria. RESULTS AND CONCLUSION:Ferroptosis is significantly different from necrosis,apoptosis and autophagy.In terms of cell morphology and function,it does not have the morphological characteristics of typical necrosis,nor does it have the characteristics of traditional apoptosis,such as cell contraction,chromatin condensation,the formation of apoptotic bodies and the disintegration of cytoskeleton.Contrary to autophagy,ferroptosis does not form a classical closed bilayer membrane structure(autophagic vacuole).Morphologically,ferroptosis is mainly manifested by obvious contraction of mitochondria,increased membrane density,and reduction or disappearance of mitochondrial cristae,which are different from other cell death modes.Iron overload can destroy bone homeostasis by significantly inhibiting osteogenic differentiation and stimulating osteoclast formation,leading to osteoporosis.Iron overload interferes with the differentiation of stem cells to osteoblasts,leading to a weakened osteoblast function and further imbalance of bone metabolism in the body,which eventually leads to osteoporosis.Stimulated by iron overload,osteoclast bone resorption is enhanced and bone loss exceeds new bone formation.Iron chelators have been proved to have osteoprotective effects by inhibiting osteoclast activity and stimulating osteogenic differentiation of osteoblasts.Its potential mechanism is related to inhibiting osteoclast differentiation and promoting osteoblast differentiation.Antioxidants can prevent reactive oxygen species production and inhibit bone absorption,thus improving bone metabolism and effectively preventing osteoporosis.