Cyclic GMP-AMP synthase (cGAS), a pivotal molecule in innate immunity, has emerged as a keypoint in interdisciplinary research at the intersection of basic immunology and tumor biology. As a cytosolic nucleic acid sensor, cGAS is primarily characterized by its capacity to recognize double-stranded DNA (dsDNA) in the cytosol. Upon binding to dsDNA, cGAS undergoes a conformational change that promotes its dimerization and subsequent enzymatic activation. Once activated, it catalyzes the synthesis of the second messenger 2',3'-cGAMP from ATP and GTP. cGAMP then binds to the adaptor protein STING, which resides on the endoplasmic reticulum (ER) membrane. The binding process triggers STING to traffic from the ER to the Golgi apparatus, where it is phosphorylated by the kinase TBK1. Phosphorylated STING serves as a docking site for the transcription factor IRF3, facilitating its phosphorylation by TBK1. Once phosphorylated, IRF3 forms dimers and translocates to the nucleus, where it drives the expression of type I interferons and pro-inflammatory cytokines, initiating a potent antimicrobial state. The DNA-sensing mechanism of cGAS is inherently non-selective regarding the origin of its ligand. It readily detects exogenous DNA from invading pathogens, thereby playing an indispensable role in host defense against microbial infections. However, this same mechanism also enables cGAS to recognize self-DNA that leaks from the nucleus or mitochondria into the cytosol under various cellular stress conditions. While critical for immunity, the recognition of self-dsDNA by cGAS can disrupt cellular homeostasis and trigger aberrant inflammatory responses. The loss of self-tolerance can precipitate or exacerbate the pathogenesis of autoimmune disorders such as systemic lupus erythematosus (SLE) and Aicardi-Goutières syndrome (AGS), highlighting the dual role of cGAS as both a sentinel for infection and a potential driver of autoimmune pathology. Notably, the subcellular localization of cGAS is not still. Increasing recent researches have revealed that cGAS is also abundant within the nucleus, challenging the traditional view of it solely as a cytosolic nucleic acid sensor. Within the nucleus, cGAS exhibits non-canonical functions that are distinct from its canonical immunological role. First, cGAS exists in a state of stringent immunological silence in the nucleus, with mechanisms involving its competitive binding to histones and its post-translational modifications which block the activation of cGAS enzymatic activity, thus, effectively preventing it from mounting an autoimmune attack on genomic DNA. Second, cGAS plays a critical role in maintaining genomic stability. Upon DNA damage, cGAS is rapidly recruited to the lesion site and participates in the DNA damage repair process. Moreover, under conditions of DNA replication stress, cGAS contributes to the stabilization of replication forks, preventing the cell from entering a state of uncontrolled hyper-replication. Consequently, in light of the dual role of cGAS in both immune regulation and tumor development, the development of small-molecule drugs targeting cGAS holds significant therapeutic promise. This review summarizes the structural characteristics of cGAS and its canonical function as a pattern recognition receptor in the cytosol, including the types of pathogens it recognizes and the autoimmune responses resulting from erroneous recognition of self-DNA. It then focuses on its emerging non-canonical functions within the nucleus, detailing its nucleocytoplasmic shuttling, the mechanisms underlying its nuclear immune quiescence, and its role in mediating DNA damage repair and replication fork stabilization. Finally, the review discusses the progress and application prospects of small-molecule drugs targeting cGAS for the treatment of autoimmune diseases and cancer.

Cyclic GMP-AMP synthase (cGAS), a pivotal molecule in innate immunity, has emerged as a keypoint in interdisciplinary research at the intersection of basic immunology and tumor biology. As a cytosolic nucleic acid sensor, cGAS is primarily characterized by its capacity to recognize double-stranded DNA (dsDNA) in the cytosol. Upon binding to dsDNA, cGAS undergoes a conformational change that promotes its dimerization and subsequent enzymatic activation. Once activated, it catalyzes the synthesis of the second messenger 2',3'-cGAMP from ATP and GTP. cGAMP then binds to the adaptor protein STING, which resides on the endoplasmic reticulum (ER) membrane. The binding process triggers STING to traffic from the ER to the Golgi apparatus, where it is phosphorylated by the kinase TBK1. Phosphorylated STING serves as a docking site for the transcription factor IRF3, facilitating its phosphorylation by TBK1. Once phosphorylated, IRF3 forms dimers and translocates to the nucleus, where it drives the expression of type I interferons and pro-inflammatory cytokines, initiating a potent antimicrobial state. The DNA-sensing mechanism of cGAS is inherently non-selective regarding the origin of its ligand. It readily detects exogenous DNA from invading pathogens, thereby playing an indispensable role in host defense against microbial infections. However, this same mechanism also enables cGAS to recognize self-DNA that leaks from the nucleus or mitochondria into the cytosol under various cellular stress conditions. While critical for immunity, the recognition of self-dsDNA by cGAS can disrupt cellular homeostasis and trigger aberrant inflammatory responses. The loss of self-tolerance can precipitate or exacerbate the pathogenesis of autoimmune disorders such as systemic lupus erythematosus (SLE) and Aicardi-Goutières syndrome (AGS), highlighting the dual role of cGAS as both a sentinel for infection and a potential driver of autoimmune pathology. Notably, the subcellular localization of cGAS is not still. Increasing recent researches have revealed that cGAS is also abundant within the nucleus, challenging the traditional view of it solely as a cytosolic nucleic acid sensor. Within the nucleus, cGAS exhibits non-canonical functions that are distinct from its canonical immunological role. First, cGAS exists in a state of stringent immunological silence in the nucleus, with mechanisms involving its competitive binding to histones and its post-translational modifications which block the activation of cGAS enzymatic activity, thus, effectively preventing it from mounting an autoimmune attack on genomic DNA. Second, cGAS plays a critical role in maintaining genomic stability. Upon DNA damage, cGAS is rapidly recruited to the lesion site and participates in the DNA damage repair process. Moreover, under conditions of DNA replication stress, cGAS contributes to the stabilization of replication forks, preventing the cell from entering a state of uncontrolled hyper-replication. Consequently, in light of the dual role of cGAS in both immune regulation and tumor development, the development of small-molecule drugs targeting cGAS holds significant therapeutic promise. This review summarizes the structural characteristics of cGAS and its canonical function as a pattern recognition receptor in the cytosol, including the types of pathogens it recognizes and the autoimmune responses resulting from erroneous recognition of self-DNA. It then focuses on its emerging non-canonical functions within the nucleus, detailing its nucleocytoplasmic shuttling, the mechanisms underlying its nuclear immune quiescence, and its role in mediating DNA damage repair and replication fork stabilization. Finally, the review discusses the progress and application prospects of small-molecule drugs targeting cGAS for the treatment of autoimmune diseases and cancer.

Objective To analyze the clinical efficacy of valve surgeries for infective endocarditis and the affecting factors, and compare the early- and long-term postoperative outcomes of different surgery approaches. Methods The patients with infective endocarditis who underwent valve replacement/valvuloplasty in our hospital from 2010 to 2022 were retrospectively collected. The clinical data of the patients were analyzed. Results A total of 343 patients were enrolled, including 197 patients with mechanical valve replacement, 62 patients with bioprosthetic valve replacement, and 84 patients with valvuloplasty. There were 238 males and 105 females with an average age of (44.2±14.8) years. Single-valve endocarditis was present in 200 (58.3%) patients, and multivalve involvement was present in 143 (41.7%) patients. Sixty (17.5%) patients had suffered thrombosis before surgery, including cerebral embolisms in 32 patients. The mean follow-up time was (60.6±43.8) months. Early mortality within one month after the surgery occurred in 17 (5.0%) patients, while later mortality occurred in 19 (5.5%) patients. Eight (2.3%) patients underwent postoperative dialysis, 13 (3.8%) patients suffered postoperative stroke, 6 patients underwent reoperation, and 3 patients suffered recurrence of infective endocarditis. Smoking (P=0.002), preoperative embolisms (P=0.001), duration of surgery (P=0.001), and postoperative dialysis (P=0.001) were risk factors for early mortality, and left ventricular ejection fraction ≥60% (P=0.022) was protective factor for early mortality. New York Heart Association classification Ⅲ-Ⅳ (P=0.010) and ≥3 valve procedures (P=0.028) were risk factors for late mortality. The rate of composite endpoint events was significantly lower in the valvuloplasty group than that in the valve replacement group. Conclusion For patients with infective endocarditis, smoking and preoperative embolisms are associated with high postoperative mortality, multiple-valve surgery is associated with a poorer prognosis, and valvuloplasty has advantages over valve replacement and should be attempted in the surgical management of patients with infective endocarditis.

Objective To design a VR-based air evacuation training system for simulating the on-board medical treatment process during air evacuation.Methods A VR-based air evacuation training system was developed which used 3D modeling technology to construct models of the medical aircraft cabin,medical devices and virtual characters to achieve scene interaction.The hardware part of the system included server computers,training terminal computers,VR equipment,3D fusion projection equipment,motion capture equipment,etc.The software of the system was developed using C++,UE4 Blueprint and C# programming languages,including two modules for medical treatment unit and medical treatment training process evaluation.The efficacy of the system was verified by the trials in air evacuation.Results The system developed successfully simulated the scenarios of tracheal tube dislodgement and increased intracranial pressure in the scenario model of open severe craniocerebral injury.The expert evaluation showed that the system gained advantages in training efficiency,low cost,safety,sense of immersion and recorded the operation data in real time to optimize the follow-up training.Conclusion The system developed delivers a virtual training environment with high-fidelity replication of real-mission conditions,enabling whole-course and immersive air evacuation drills.[Chinese Medical Equipment Journal,2025,46(3):15-20]

Objective To investigate the distribution and antimicrobial resistance profiles of clinically isolated Haemophilus influenzae and Moraxella catarrhalis in hospitals across China from 2015 to 2021,and provide evidence for rational use of antimicrobial agents.Methods Data of H.influenzae and M.catarrhalis strains isolated from 2015 to 2021 in CHINET program were collected for analysis,and antimicrobial susceptibility testing was performed by disc diffusion method or automated systems according to the uniform protocol of CHINET.The results were interpreted according to the CLSI breakpoints in 2022.Beta-lactamases was detected by using nitrocefin disk.Results From 2015 to 2021,a total of 43 642 strains of Haemophilus species were isolated,accounting for 2.91％of the total clinical isolates and 4.07％of Gram-negative bacteria in CHINET program.Among the 40 437 strains of H.influenzae,66.89％were isolated from children and 33.11％were isolated from adults.More than 90％of the H.influenzae strains were isolated from respiratory tract specimens.The prevalence of β-lactamase was 53.79％in H.influenzae strains.The H.influenzae strains isolated from children showed higher resistance rate than the strains isolated from adults.Overall,779 strains of H.influenzae did not produce β-lactamase but were resistant to ampicillin(BLNAR).Beta-lactamase-producing strains showed significantly higher resistance rates to these antimicrobial agents than the β-lactamase-nonproducing strains.Of the 16 191 M.catarrhalis strains,80.06％were isolated from children and 19.94％isolated from adults.M.catarrhalis strains were mostly susceptible to both amoxicillin-clavulanic acid and cefuroxime,evidenced by resistance rate lower than 2.0％.Conclusions The emergence of antibiotic-resistant H.influenzae due to β-lactamase production poses a challenge for clinical anti-infective treatment.Therefore,it is very important to implement antibiotic resistance surveillance for H.influenzae and guide rational antibiotic use.All local clinical microbiology laboratories should actively improve antibiotic susceptibility testing and strengthen antibiotic resistance surveillance for H.influenzae.

Objective To understand the changing composition and antibiotic resistance of bacterial species in the clinical isolates from outpatient and emergency department(hereinafter referred to as outpatients)and inpatient children over time in various hospitals,and to provide laboratory evidence for rational antibiotic use.Methods The data on clinically isolated pathogenic bacteria and antimicrobial susceptibility of isolates from outpatients and inpatient children in the CHINET program from 2015 to 2021 were collected and analyzed.Results A total of 278 471 isolates were isolated from pediatric patients in the CHINET program from 2015 to 2021.About 17.1％of the strains were isolated from outpatients,primarily group A β-hemolytic Streptococcus,Escherichia coli,and Staphylococcus aureus.Most of the strains(82.9％)were isolated from inpatients,mainly SS.aureus,E.coli,and H.influenzae.The prevalence of methicillin-resistant S.aureus(MRSA)in outpatients(24.5％)was lower than that in inpatient children(31.5％).The MRSA isolates from outpatients showed lower resistance rates to the antibiotics tested than the strains isolated from inpatient children.The prevalence of vancomycin-resistant Enterococcus faecalis or E.faecium and penicillin-resistant S.pneumoniae was low in either outpatients or inpatient children.S.pneumoniae,β-hemolytic Streptococcus and S.viridans showed high resistance rates to erythromycin.The prevalence of erythromycin-resistant group A β-hemolytic Streptococcus was higher in outpatients than that in inpatient children.The prevalence of β-lactamase-producing H.influenzae showed an overall upward trend in children,but lower in outpatients(45.1％)than in inpatient children(59.4％).The prevalence of carbapenem-resistant Klebsiella pneumoniae(CRKpn),carbapenem-resistant Pseudomonas aeruginosa(CRPae)and carbapenem-resistant Acinetobacter baumannii(CRAba)was 14％,11.7％,47.8％in outpatients,but 24.2％,20.6％,and 52.8％in inpatient children,respectively.The prevalence of multidrug-resistant E.coli,K.pneumoniae,Proteus mirabilis,P.aeruginosa and A.baumannii strains was lower in outpatients than in inpatient children.The prevalence of fluoroquinolone-resistant E.coli,ESBLs-producing K.pneumoniae,ESBLs-producing P.mirabilis,carbapenem-resistant E.coli(CREco),CRKpn,and CRPae was lower in children in outpatients than in inpatient children,but the prevalence of CRAba in 2021 was higher than in inpatient children.Conclusions The distribution of clinical isolates from children is different between outpatients and inpatients.The prevalence of MRSA,ESBL,and CRO was higher in inpatient children than in outpatients.Antibiotics should be used rationally in clinical practice based on etiological diagnosis and antimicrobial susceptibility test results.Ongoing antimicrobial resistance surveillance and prevention and control of hospital infections are crucial to curbing bacterial resistance.

Objective To investigate the changing antibiotic resistance profiles of E.coli isolated from patients in the 52 hospitals participating in the CHINET program from 2015 to 2021.Methods Antimicrobial susceptibility was tested for clinical isolates of E.coli according to the unified protocol of CHINET program.WHONET 5.6 and SPSS 20.0 software were used for data analysis.Results Atotal of 289 760 nonduplicate clinical strains ofE.coli were isolated from 2015 to 2021,mainly from urine samples(44.7±3.2)％.The proportion of E.coli strains isolated from urine samples was higher in females than in males(59.0％vs 29.5％).The proportion of E.coli strains isolated from respiratory tract and cerebrospinal fluid samples was significantly higher in children than in adults(16.7％vs 7.8％,0.8％vs 0.1％,both P＜0.05).The isolates from internal medicine department accounted for the largest proportion(28.9±2.8)％with an increasing trend over years.Overall,the prevalence of ESBLs-producing E.coli and carbapenem resistant E.coli(CREco)was 55.9％and 1.8％,respectively during the 7-year period.The prevalence of ESBLs-producing E.coli was the highest in tertiary hospitals each year from 2015 to 2021 compared to secondary hospitals.The prevalence of CREco was higher in children's hospitals compared to secondary and tertiary hospitals each year from 2015 to 2021.The prevalence of ESBLs-producing E.coli in tertiary hospitals and children's hospitals and the prevalence of CREco in children's hospitals showed a decreasing trend over the 7-year period.The prevalence of CREco in secondary and tertiary hospitals increased slowly.Antibiotic resistance rates changed slowly from 2015 to 2021.Carbapenem drugs(imipenem,meropenem)were the most active drugs amongβ-lactams against E.coli(resistance rate≤2.1％).The resistance rates of E.coli to β-lactam/β-lactam inhibitor combinations(piperacillin-tazobactam,cefoperazone-sulbactam),aminoglycosides(amikacin),nitrofurantoin and fosfomycin(for urinary isolates only)were all less than 10％.The resistance rate of E.coli strains to antibiotics varied with the level of hospitals and the departments where the strains were isolated,especially for cefazolin and ciprofloxacin,to which the resistance rate of E.coli strains from children in non-ICU departments was significantly lower than that of the strains isolated from other departments(P＜0.05).The E.coli isolates from ICU showed higher resistance rate to most antimicrobial agents tested(excluding tigecycline)than the strains isolated from other departments.The E.coli strains isolated from tertiary hospitals showed higher resistance rates to the antimicrobial agents tested(excluding tigecycline,polymyxin B,cefepime and carbapenems)than the strains from secondary hospitals and children's hospitals.Conclusions E.coli is an important pathogen causing clinical infection.More than half of the clinical isolates produced ESBL.The prevalence of CREco is increasing in secondary and tertiary hospitals over the 7-year period even though the overall prevalence is still low.This is an issue of concern.

This study was analyzed the spatial-temporal distribution and aggregation characteristics of Yersinia pestispositive host animals and vector pathogens in marmot natural foci in the Qilian-Altun mountains,Gansu Province,to provide a scientific basis for precise plague prevention and control.Y.pestissurveillance data for marmot natural foci in Qilian-Altun Mountains of Gansu Province from 2014 to 2023 were obtained from the Disease Control and Prevention Center of Gansu Province.Origin 2024 software was used for data visualization and presentation.Global and local spatial autocorrelation analyses and trend analyses were conducted in ArcGIS 10.8 software,with townships as the spatial scale.Cumulatively,440 strains of Y.pestis were isolated from the natural marmot foci in the Qilian-Altun mountainsof Gansu Province from 2014 to 2023.Most strains was isolated from marmots(345 strains,78.41%),and the remainder were isolated from vectors.Temporal distribution analysis indicated that the highest number of detected bacteria was reported in July and August(both 121 strains,27.50%).Regional distribution analysis revealed that Aksai County reported the highest number of detected bacteria(255 strains,57.95%).Global spatial autocorrelation analysis showed a spatially clustered distribution of the number of bacteria detected annually in the townships containing natural foci,except in2014,2016,and 2021-2023.The strongest spatial clustering was observed in 2020(Moran's I=0.521 2,Z=14.397 0,P<0.001).Local spatial autocorrelation analysis indicated a"high-high"aggregation area in the natural foci every year from 2014 to 2023,primarily in Hongliuwan Town of Aksai County and Dangchengwan Town of Subei County.The distribution of the"low-low"aggregation area was essentially consistent with the low activity area of the Yersinia pestisepidemic.The trend in annual total bacterial count gradually increased from east to west,and peaked in the western part of the epidemic focus.Clear spatial aggregation characteristics of the number of Y.pestis were detected in the marmot natural foci in the Qilian-Altun mountains at the townshiplevel as a whole in Gansu Province from 2014 to 2023.The aggregation area was mainly in the western section of Qilian Mountain to the Altun mountain section of the epidemic source area.Monitoring and prevention and control efforts should be focused in this key area,with prevention and control measures tailored to the local conditions,and classified guidance to decrease the risk of plague occurrence and spread.

Objective To describe the clinical features of patients with primary sclerosing cholangitis(PSC)in China based on a nationwide multicenter patient cohort,and to investigate the risk factors for prognosis.Methods A retrospective cohort study was conducted among the patients with a confirmed diagnosis of PSC based on the electronic medical record system of seven grade A tertiary hospitals across the country,and related data were extracted.The Mann-Whitney U test was used for comparison of continuous data between groups,and the chi-square test was used for comparison of categorical data between groups.The Kaplan-Meier method was used to estimate liver transplant-free survival,and the log-rank test was used for comparison of survival rate between PSC patients with different features.The Cox regression model was used to identify independent risk factors for the prognosis of PSC patients and the interactions between key factors.Results A total of 107 patients were enrolled,among whom 55.6%(55/99)had large-duct PSC and 29.0%(31/107)had comorbidity with inflammatory bowel disease(IBD).The positivity rate of anti-neutrophil cytoplasmic antibody(ANCA)was 32.9%(24/73),and 50.0%(40/80)of the patients had an increase in IgG/IgM.The median symptom-to-diagnosis interval was 1 year(<1-4.0),and 38.3%(41/107)of the patients had progressed to decompensated cirrhosis at the time of diagnosis.The median liver transplant-free survival time was 114 months(95%confidence interval[CI]:62-166),with a 5-year survival rate of 65.7%.The multivariate analysis showed that an increase in total bile acid(TBA)(hazard ratio[HR]=1.006,95%CI:1.002-1.010,P=0.001)and a prolonged symptom-to-diagnosis interval(HR=1.252,95%CI:1.059-1.480,P=0.009)were independent risk factors for prognosis.The interaction analysis showed that compared with the female patients with TBA<50 μmol/L,both male and female patients with TBA≥50 μmol/L had a significant increase in the risk of liver transplantation or death(male:HR=16.563,95%CI:2.103-130.449,P<0.001;female:HR=17.009,95%CI:2.113-136.934,P<0.001),and compared with the patients with an age of<45 years and a TBA level of<50 μmol/L,the patients with an age of≥45 years and a TBA level of≥50 μmol/L had a significant increase in the risk of liver transplantation or death(HR=10.729,95%CI:1.325-86.859,P=0.026).Compared with the female patients with an symptom-to-diagnosis interval of≤2 years,the male patients with a symptom-to-diagnosis interval of>2 years had an increased risk of liver transplantation or death(HR=4.825,95%CI:1.725-13.644,P=0.003),and compared with the patients with an age of<45 years and a symptom-to-diagnosis interval of≤2 years,the patients with an age of<45 years and a symptom-to-diagnosis interval of>2 years had an increased risk of liver transplantation or death(HR=4.983,95%CI:1.366-18.173,P=0.015).Conclusion Compared with the reports from Western countries,large-duct PSC is also the main type of PSC in China,but with a relatively low proportion,and there is also a relatively low proportion of patients with IBD or positive ANCA.An increase in TBA and a prolonged symptom-to-diagnosis interval are independent risk factors for prognosis,with significant interactions with age and sex.This suggests that early screening and intervention should be enhanced to improve prognosis.

Objective:To investigate the surgical techniques and clinical efficacy of arthroscopic-assisted posterior malleolus reduction for the management of ankle fracture-dislocation.Methods:A retrospective analysis was performed on the clinical data of 27 patients who underwent arthroscopy-assisted posterior malleolar reduction via the posterior approach for the surgical management of ankle fracture-dislocation at the Third Affiliated Hospital of Nanjing Medical University (Changzhou No.2 People's Hospital) between January 2022 and June 2023. The cohort comprised 17 males and 10 females, with a mean age of 43.67±9.56 years (range, 25-63 years). Based on the Bartonícek and Rammelt classification, there were 15 type II cases, 9 type III cases, and 3 type IV cases. The operation time, posterior ankle arthroscopy duration, and postoperative complications, such as neurovascular injury, wound infection, or skin necrosis, were recorded. X-ray and 3D CT imaging were utilized to assess joint surface reduction quality, tibiofibular matching and fracture healing status. The ankle plantarflexion, dorsiflexion and hallux flexion contractures were recorded at the last follow-up. Functional outcomes were measured using the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score and the Olerud-Molander ankle score (OMAS), while pain was evaluated using the visual analogue scale (VAS).Results:All 27 patients were followed up postoperatively, with a mean follow-up duration of 14.30±1.38 months (range, 12-18 months). Postoperatively, one patient experienced wound exudation, while another developed intermuscular venous thrombosis in the calf. No cases of neurovascular injury, wound infection, skin necrosis, or hallux flexion contracture occurred, and no reduction loss was observed. The mean operation time was 96.11±11.55 min (range, 80-120 min), and the posterior ankle arthroscopy duration was 35.74±5.67 min (range, 30-45 min). Postoperative X-ray evaluations demonstrated no loss of fracture reduction, and all fractures achieved bony union. The mean fracture healing time was 3.78±0.75 months (range, 3-5 months). Postoperative CT evaluations showed no joint surface malalignment, and distal tibiofibular matching was satisfactory. At the final follow-up, mean ankle plantarflexion was 46.74°±4.73° (range, 33°-50°), and dorsiflexion was 20.96°±3.29° (range, 14°-26°). There was no hallux flexion contracture occurred. The mean AOFAS ankle-hindfoot score was 92.11±7.19 (range, 74-100), with 20 excellent, 5 good, and 2 fair, yielding an excellent-good rate of 93%. The mean OMAS score was 94.44±7.25 (range, 75-100), comprising 20 excellent and 7 good results, yielding an excellent-good rate of 100%. The mean VAS score was 0.70±0.95 (range, 0-3).Conclusion:Arthroscopy-assisted posterior malleolar reduction in ankle fracture-dislocation surgery provides optimal soft tissue protection and ensures precise fracture reduction and fixation.