Objectives:To evaluate the biomechanics of a new self-developed bidirectional self-locking fusion device in vitro.Methods:12 fresh L3/4 segment specimens of domestic pig spine were randomly divided into 3 groups for modeling:normal group(intact state),traditional fusion device group(traditional fusion device and unilateral screw fixation)and new fusion device group(bidirectional self-locking fusion device implanted).On the basis of MTS multi-freedom(spinal motion)simulation test system and 500N preload,8N·m load was applied to experimental specimens in each direction successively,and the stability test was carried out according to the order of forward bending,backward extension,left bending,right bending,and left and right rotation.The ranges of motion(ROMs)were compared between groups under different working conditions.The axial fatigue compression test was carried out with TT-JQ-01-106 fatigue testing machine to evaluate the stability and reliability of the self-developed fusion device.Results:Compared with the normal group,the ROM of the new fusion device group was significantly decreased under the conditions of flexion(1.67°±0.65° vs 3.46°±0.16°),extension(1.43°±1.01° vs 1.89°±0.29°),left bending(2.07°±1.32° vs 3.08°±0.09°),right bending(1.38°±0.72° vs 4.37°±0.20°),and right rotation(2.17°±1.51° vs 5.10°±0.37°)(all P＜0.05);Under the left rotation condition,the ROM value(3.10°±1.57°)of the new device group was significantly higher than that of the normal group(2.36°±0.62°)(P＜0.05).Compared with the conventional fusion device group,the ROM of the new fusion device group was significantly increased under flexion(1.67°±0.65° vs 1.22°±0.76°)and left rotation(3.10°±1.57° vs 1.57°±0.91°)conditions(P＜0.05);However,there were no significant differences in ROMs between the two groups under extension(1.43°±1.01° vs 1.06°±0.50°),left bending(2.07°±1.32° vs 1.87°±1.41°),right bending(1.38°±0.72° vs 1.45°±0.69°),and right rotation(2.17°±1.51° vs 1.69°±1.07°)conditions(P＞0.05).The ROM values of the normal group under flexion,extension,left bending,right bending,and right rotation conditions were significantly higher than those of the other two groups(P＜0.05).Fatigue test:after 5 million load-displacement cycles,visual inspection revealed no deformation or cracks in the fusion device,and the axial compression fatigue test was passed.Conclusions:The bidirectional self-locking fusion device can obviously improve the stability of the fusion segment,which is equivalent to the stability of using the posterior single-sided nail rod system,meanwhile,it has good fatigue resistance,therefore its mechanical properties can meet the needs of clinical applications.

Objective To investigate the dosimetric effects of tumor treating fields(TTFields)patches on different radiotherapy modes for glioblastoma(GBM)patients who wear TTFields patches during radiotherapy,thereby providing dosimetric guidance for determining the appropriate radiotherapy mode.Methods With the TTFields data from GBM patients,artifact-free radiotherapy CT images were obtained utilizing 3D-printed TPU TTFields patches(3D-Print-TTFields)and anthropomorphic phantoms,and then a TTFields-synchronized radiotherapy image model was constructed.Furthermore,the treatment planning system was used to construct a dosimetric calculation model for TTFields-synchronized radiotherapy by simulating and fitting the ray attenuation rate of TTFields patches measured by accelerators.Using these models,3 kinds of radiotherapy plans were simulated and developed.Specifically,P1 simulated the conventional radiotherapy mode;P2 simulated the TTFields-combined radiotherapy mode(TTF-Com-RT),in which patients underwent radiotherapy using the P1 plan while wearing TTFields patches;and P3 simulated the TTFields-synchronized radiotherapy(TTF-Syn-RT)mode where the TTFields patches were worn throughout the entire radiotherapy process.The paired t-test was used to analyze dosimetric parameters such as target dose(D95),average scalp dose(D-skin),conformity index(CI)and homogeneity index(HI)in 3 plans(P1,P2,and P3),as well as the D95 and D-skin parameters for intensity-modulated radiotherapy(IMRT)and volumetric modulated arc therapy(VMAT)techniques in the P3 plan.Results The D95 simulated by P2 decreased by 1.35%as compared with P1(P<0.05),and the D95 simulated by P3 was 1.31%higher than that in P2(P<0.05).Compared with P1,P2 and P3 increased the D-skin by 12.56%and 14.30%,respectively(P<0.05),and the D-skin simulated by P3 increased by 1.55%as compared with P2(P<0.05).However,there were trivial differences in D95 between P3 and P1,CI and HI among all plans,D95 and D-skin between IMRT and VMAT techniques in P3 plan(P>0.05).Conclusion Based on GBM patient data,CT simulation images obtained from 3D-Print-TTFields combined with anthropomorphic phantom are artifact-free and meet radiotherapy requirements.The target and scalp dose differences between TTF-Com-RT and TTF-Syn-RT are less than 2%,and the dosimetric difference of TTF-Syn-RT using IMRT/VMAT techniques is insignificant.Therefore,clinicians can choose radiotherapy modes and techniques according to actual needs.

Objective To evaluate the efficacy of proximal femoral universal nail(PFUN),a new type of intramedullary fixation system,in the treatment of acute unilateral intertrochanteric femoral fracture in elderly patients.Methods From January 2022 to January 2024,200 patients with acute unilateral femoral intertrochanteric fracture were treated in our department.After closed traction reduction,PFUN was implanted with small incisions.Unified rehabilitation plan was adopted after surgery.The functional evaluation was performed by using the Harris hip score system at the last follow-up.Results The operation time was 25-182 min(median,63.0 min).The intraoperative blood loss was 10-750 ml(median,50.0 ml).Intraoperative blood transfusion(suspension of red blood cells)was required in 40 cases(20％).The postoperative hospital stay was 1-15 d(mean,4.0±1.9 d).The postoperative femoral neck-shaft angle was 116.7°-140.1°(mean,132.4°±5.5°).The quality of fracture reduction on the first day after surgery showed 140 cases as excellent,54 cases acceptable,and 6 cases poor.Complications occurred in 13 cases,including superficial wound infection in 2 cases,who were cured by regular wound dressing change and antibiotic treatment,lower extremity deep vein thrombosis in 8 cases,who were given low molecular weight heparin anticoagulation treatment until improvement,pneumonia in 2 cases and urinary tract infection in 1 case,who were cured or improved after specialist treatment.At one month after surgery,the hip joint X-ray showed blurred fracture lines,callus formation at the fracture site,and no internal fixation failure.There was no internal fixation failure within 3 months after surgery.At six months after surgery,all fractures achieved healing without any failure of internal fixation.All the 200 cases were followed up for 12-29 months(mean,16.1±2.7 months).One case experienced internal fixation failure,and underwent head and neck screw resection,internal fixation removal and hip replacement.At the last follow-up,the postoperative recovery was satisfactory.The Harris score of hip joint was 70-94 points(mean,88.8±2.8 points),including 103 cases as excellent,92 cases good,and 5 cases fair,with an excellent and good rate of 97.5％(195/200).Conclusion PFUN is effective in the treatment of intertrochanteric femoral fractures in elderly patients,with reliable fixation,rapid postoperative recovery,and low failure rate of internal fixation,especially suitable for unstable cases with internal or external wall fractures.

Objective:To investigate the effects of thoracolumbar vertebral fracture with incomplete spinal cord injury on male sexual function and postoperative prognosis.Methods:A retrospective review was conducted on data from 144 male patients with thoracolumbar vertebral fractures and incomplete spinal cord injuries treated between May 2009 and May 2021 in the Department of Traumatology and Orthopedics at Peking University Third Hospital. Patients ranged in age from 19 to 55 years (mean: 38.6±10.6 years) and underwent posterior incision and reduction internal fixation. The International Index of Erectile Function-5 (IIEF-5), the Premature Ejaculation Diagnostic Tool (PEDT), and the International Spinal Cord Injury Male Sexual Function Basic Data Set were used for sexual function evaluation. Based on the American Spinal Injury Association (ASIA) Spinal Cord Injury classification, changes in neurological and sexual function were assessed at the pre-injury stage, 3 months post-injury, 2 years postoperatively, and at the final follow-up. Factors influencing sexual dysfunction and recovery were analyzed. Spearman correlation analysis was used to identify factors affecting sexual function injury and recovery.Results:A total of 117 patients were included in the final analysis. Follow-up duration ranged from 26.2 to 161.7 months (mean: 74.6±40.5 months). After injury, ASIA grades were distributed as follows: 43 patients with grade B, 41 with grade C, and 33 with grade D. At the 2-year follow-up, 30 patients were grade E, 63 grade D, 19 grade C, and 5 grade B. Improvement in ASIA classification was observed in 90.6% (106/117) of patients: 79 improved by one grade, 27 by two grades, 8 remained unchanged, 1 worsened by one grade, and 2 worsened by two grades. Mean IIEF-5 scores were 19.5±6.4 pre-injury, 8.7±8.0 at 3 months post-injury, and 17.5±7.1 at 2 years postoperatively, with statistically significant differences ( F=123.247, P<0.001). Differences between 3 months post-injury vs. pre-injury and 2 years postoperatively vs. 3 months post-injury were statistically significant ( P<0.05). Mean PEDT scores were 5.3±3.1 pre-injury, 6.9±5.2 at 3 months post-injury, and 6.4±5.1 at 2 years postoperatively, with statistically significant differences ( F=17.014, P<0.001). The difference between 3 months post-injury and pre-injury was statistically significant ( P<0.05), but not between 2 years postoperatively and 3 months post-injury ( P>0.05). At the 2-year follow-up, 96 patients had their IIEF-5 classification restored to pre-injury levels, 85 restored PEDT classifications, and 83 restored both. Post-injury ASIA classification was positively correlated with a decrease in IIEF-5 score and an increase in PEDT score at 3 months post-injury ( P<0.05). Injury segment was positively correlated with the decrease in IIEF-5 score ( P<0.05). Time from injury to surgery showed a positive correlation with increased PEDT score at 3 months ( P<0.05). Post-injury ASIA grade, injury segment, time to surgery, age, intraoperative decompression, and spinal cord function recovery all showed significant correlations with changes in IIEF-5 and (or) PEDT scores at 2 years postoperatively ( P<0.05). According to the International Spinal Cord Injury Male Sexual Function Basic Data Set, the proportion of patients willing to discuss sexual issues increased from 29.9% at 3 months post-injury to 47.9% at 2 years postoperatively ( P<0.05). The proportion of patients with absent or diminished psychogenic erections remained stable (48.7% vs. 48.9%, P>0.05), while those with normal reflexive erections increased from 34.2% to 65.0% ( P<0.05). Conclusion:Thoracolumbar fractures with incomplete spinal cord injury result in reduced erectile function and increased incidence of premature ejaculation. The degree of spinal cord injury and the level of the injured segment are strongly correlated with the extent of sexual dysfunction. At the 2-year postoperative follow-up, 70.9% of patients had recovered sexual function to pre-injury levels.

Objective:To investigate the risk factors associated with 90-day mortality in critically ill patients receiving continuous renal replacement therapy (CRRT), with a particular focus on the association between hypotension within the first hour of CRRT initiation and 90-day mortality after hospital admission.Methods:This study was a post hoc analysis of a prospective cohort study investigating the impact of colloid versus crystalloid priming solutions on early hemodynamics in critically ill patients undergoing CRRT. The study enrolled intensive care unit patients who received CRRT at West China Hospital of Sichuan University from January 2024 to May 2024. The data were collected including demographic characteristics, laboratory tests, CRRT-related parameters, blood pressure, heart rate, sequential organ failure assessment scores, and vasoactive-inotropic score, etc. The 90-day survival outcome after hospital admission of critically ill patients aged 18-80 years who received continuous veno-venous hemodiafiltration was used as the primary outcome indicator. A Cox proportional hazards model analysis was conducted, and the predictive ability of the model was evaluated along with the test of the proportional hazards assumption. The risk factors associated with the 90-day mortality after hospital admission of critically ill patients receiving CRRT were explored, with a particular focus on whether hypotension occurring within the first hour of CRRT initiation was one of these risk factors.Results:A total of 208 patients were included in this study. Within 90 days after hospital admission, 141 patients (67.8%) died, among whom 102 were male (72.3%) and the median age was 61.0 (50.0, 71.5) years; 67 patients (32.2%) survived, among whom 53 were males (79.1%) and the median age was 56.0 (47.0, 68.0) years. The incidence of hypotension within the first hour of CRRT initiation was significantly higher in the death group than in the survival group [29.8% (42/141) vs. 16.4% (11/67), χ2=4.275, P=0.039]. Moreover, The mortality rate of the group with hypotension within the first hour of CRRT initiation was higher than that of the group without hypotension [79.2% (42/53) vs. 63.9% (99/155), χ2=4.275, P=0.039]. The Kaplan-Meier survival analysis showed that the median survival time of patients without hypotension within the first hour of CRRT initiation [39.0 d (95% CI 23.2-54.8)] was longer than that of patients with hypotension [26.0 d (95% CI 18.9-33.1)], and the 90-day cumulative survival rate after hospital admission of patients without hypotension was significantly higher than that of patients with hypotension (Log-rank test, χ2=5.100, P=0.024). Univariate and multivariate Cox proportional hazards analyses demonstrated that serum albumin ( HR=0.964, 95% CI 0.933-0.997, P=0.030), sequential organ failure assessment score ( HR=1.064, 95% CI 1.012-1.118, P=0.015), and the use of mechanical ventilation ( HR=8.272, 95% CI 1.145-59.743, P=0.036) were significantly associated with 90-day mortality in critically ill patients undergoing CRRT. In contrast, the vasoactive-inotropic score ( HR=1.004, 95% CI 0.999-1.008, P=0.079) and the presence of hypotension within the first hour of CRRT initiation ( HR=1.236, 95% CI 0.833-1.835, P=0.293) were not significantly associated with 90-day mortality in critically ill patients undergoing CRRT. The consistency index of this model was 0.654 (95% CI 0.617-0.691), the area under the receiver operating characteristic curve was 0.724 (95% CI 0.658-0.800), and the calibration curve showed that the predicted values of the model were well fitted to the actual observations, suggesting that the predictive effect of this model was relatively ideal. Conclusions:In critically ill patients undergoing CRRT, the occurrence of hypotension within the first hour of CRRT initiation was not significantly associated with 90-day mortality after hospital admission. Lower serum albumin levels, higher sequential organ failure assessment scores, and the use of mechanical ventilation may be the risk factors for 90-day mortality in this population.

Objective To evaluate the efficacy of proximal femoral universal nail(PFUN),a new type of intramedullary fixation system,in the treatment of acute unilateral intertrochanteric femoral fracture in elderly patients.Methods From January 2022 to January 2024,200 patients with acute unilateral femoral intertrochanteric fracture were treated in our department.After closed traction reduction,PFUN was implanted with small incisions.Unified rehabilitation plan was adopted after surgery.The functional evaluation was performed by using the Harris hip score system at the last follow-up.Results The operation time was 25-182 min(median,63.0 min).The intraoperative blood loss was 10-750 ml(median,50.0 ml).Intraoperative blood transfusion(suspension of red blood cells)was required in 40 cases(20％).The postoperative hospital stay was 1-15 d(mean,4.0±1.9 d).The postoperative femoral neck-shaft angle was 116.7°-140.1°(mean,132.4°±5.5°).The quality of fracture reduction on the first day after surgery showed 140 cases as excellent,54 cases acceptable,and 6 cases poor.Complications occurred in 13 cases,including superficial wound infection in 2 cases,who were cured by regular wound dressing change and antibiotic treatment,lower extremity deep vein thrombosis in 8 cases,who were given low molecular weight heparin anticoagulation treatment until improvement,pneumonia in 2 cases and urinary tract infection in 1 case,who were cured or improved after specialist treatment.At one month after surgery,the hip joint X-ray showed blurred fracture lines,callus formation at the fracture site,and no internal fixation failure.There was no internal fixation failure within 3 months after surgery.At six months after surgery,all fractures achieved healing without any failure of internal fixation.All the 200 cases were followed up for 12-29 months(mean,16.1±2.7 months).One case experienced internal fixation failure,and underwent head and neck screw resection,internal fixation removal and hip replacement.At the last follow-up,the postoperative recovery was satisfactory.The Harris score of hip joint was 70-94 points(mean,88.8±2.8 points),including 103 cases as excellent,92 cases good,and 5 cases fair,with an excellent and good rate of 97.5％(195/200).Conclusion PFUN is effective in the treatment of intertrochanteric femoral fractures in elderly patients,with reliable fixation,rapid postoperative recovery,and low failure rate of internal fixation,especially suitable for unstable cases with internal or external wall fractures.

Objective:To investigate the effects of thoracolumbar vertebral fracture with incomplete spinal cord injury on male sexual function and postoperative prognosis.Methods:A retrospective review was conducted on data from 144 male patients with thoracolumbar vertebral fractures and incomplete spinal cord injuries treated between May 2009 and May 2021 in the Department of Traumatology and Orthopedics at Peking University Third Hospital. Patients ranged in age from 19 to 55 years (mean: 38.6±10.6 years) and underwent posterior incision and reduction internal fixation. The International Index of Erectile Function-5 (IIEF-5), the Premature Ejaculation Diagnostic Tool (PEDT), and the International Spinal Cord Injury Male Sexual Function Basic Data Set were used for sexual function evaluation. Based on the American Spinal Injury Association (ASIA) Spinal Cord Injury classification, changes in neurological and sexual function were assessed at the pre-injury stage, 3 months post-injury, 2 years postoperatively, and at the final follow-up. Factors influencing sexual dysfunction and recovery were analyzed. Spearman correlation analysis was used to identify factors affecting sexual function injury and recovery.Results:A total of 117 patients were included in the final analysis. Follow-up duration ranged from 26.2 to 161.7 months (mean: 74.6±40.5 months). After injury, ASIA grades were distributed as follows: 43 patients with grade B, 41 with grade C, and 33 with grade D. At the 2-year follow-up, 30 patients were grade E, 63 grade D, 19 grade C, and 5 grade B. Improvement in ASIA classification was observed in 90.6% (106/117) of patients: 79 improved by one grade, 27 by two grades, 8 remained unchanged, 1 worsened by one grade, and 2 worsened by two grades. Mean IIEF-5 scores were 19.5±6.4 pre-injury, 8.7±8.0 at 3 months post-injury, and 17.5±7.1 at 2 years postoperatively, with statistically significant differences ( F=123.247, P<0.001). Differences between 3 months post-injury vs. pre-injury and 2 years postoperatively vs. 3 months post-injury were statistically significant ( P<0.05). Mean PEDT scores were 5.3±3.1 pre-injury, 6.9±5.2 at 3 months post-injury, and 6.4±5.1 at 2 years postoperatively, with statistically significant differences ( F=17.014, P<0.001). The difference between 3 months post-injury and pre-injury was statistically significant ( P<0.05), but not between 2 years postoperatively and 3 months post-injury ( P>0.05). At the 2-year follow-up, 96 patients had their IIEF-5 classification restored to pre-injury levels, 85 restored PEDT classifications, and 83 restored both. Post-injury ASIA classification was positively correlated with a decrease in IIEF-5 score and an increase in PEDT score at 3 months post-injury ( P<0.05). Injury segment was positively correlated with the decrease in IIEF-5 score ( P<0.05). Time from injury to surgery showed a positive correlation with increased PEDT score at 3 months ( P<0.05). Post-injury ASIA grade, injury segment, time to surgery, age, intraoperative decompression, and spinal cord function recovery all showed significant correlations with changes in IIEF-5 and (or) PEDT scores at 2 years postoperatively ( P<0.05). According to the International Spinal Cord Injury Male Sexual Function Basic Data Set, the proportion of patients willing to discuss sexual issues increased from 29.9% at 3 months post-injury to 47.9% at 2 years postoperatively ( P<0.05). The proportion of patients with absent or diminished psychogenic erections remained stable (48.7% vs. 48.9%, P>0.05), while those with normal reflexive erections increased from 34.2% to 65.0% ( P<0.05). Conclusion:Thoracolumbar fractures with incomplete spinal cord injury result in reduced erectile function and increased incidence of premature ejaculation. The degree of spinal cord injury and the level of the injured segment are strongly correlated with the extent of sexual dysfunction. At the 2-year postoperative follow-up, 70.9% of patients had recovered sexual function to pre-injury levels.

Objective To assess the clinical value of prognostic nutritional index(PNI)in predicting the prognosis of patients with advanced liver cancer treated with transarterial chemoembolization(TACE)combined with ablation therapy.Methods A total of 112 patients with advanced liver cancer,who received TACE combined with ablation at the Lishui Municipal Central Hospital of China from January 2020 to January 2024,were enrolled in this study.The general data,survival status,and survival time were collected.The Youden index of PNI was calculated using the receiver operating characteristic(ROC)curve model,and the optimal cutoff value was determined.Based on the optimal cutoff value,the patients were divided into low-PNI group and high-PNI group.The progression-free survival(PFS)and overall survival(OS)time were compared between the two groups,and the independent risk factors affecting PFS and OS were analyzed.Results The Youden index for PNI was 0.43,and the optimal cutoff value of PNI was 43.95.The low-PNI group included 65 patients,and the high-PNI group included 47 patients.There were no statistically significant differences in the baseline data between the two groups.The median PFS and the median OS in the high-PNI group were 13.21 months(95％CI=4.37-22.03)and 40.80 months(95％CI=31.55-50.05)respectively,which were longer than 9.20 months(95％CI=6.58-11.82)and 21.37 months(95％CI=16.56-26.17)respectively in the low-PNI group,the differences were statistically significant(both P＜0.05).The 6-month,one-year and 2-year PFS in the high-PNI group was 56.95％,47.25％and 33.87％respectively,which were higher than 43.95％,32.56％and 16.31％respectively in the low-PNI group.The one-year,2-year and 3-year cumulative survival rates in the high-PNI group were 80.77％,66.66％and 39.40％respectively,which were higher than 63.79％,34.31％and 27.75％respectively in the low-PNI group.Multivariate regression analysis indicated that the number of nodules,metastasis and PNI significantly affected OS,and metastasis and PNI strikingly affected PFS.High PNI was a protective factor for both PFS and OS.Conclusion For patients with advanced liver cancer treated with TACE combined with ablation therapy,PNI is an effective indicator for predicting the prognosis.

Objective To investigate the association between neutrophil-lymphocyte ratio(NLR)and diabetic kidney disease(DKD)in patients with type 2 diabetes mellitus(T2DM).Methods 548 T2DM patients hospitalized in The Second People's Hospital of Liaocheng from January 2022 to March 2023 were divided into control(Con,UACR≤30 mg/g,n=393)group,microalbuminuria(Mic,UACR 30～300 mg/g,n=103)group and macroalbuminuria(Mac,UACR＞300 mg/g,n=52)group according to the levels of UACR.Results In the Con,Mic and Mac groups,blood urea nitrogen(BUN),serum creatinine(Scr),serum uric acid(SUA),cystatin C(CysC)and total cholesterol(TC)increased successively(P＜0.05),and estimated glomerular filtration rate(eGFR)decreased successively(P＜0.05).The systolic blood pressure(SBP),NLR,neutrophil count and lymphocyte count(Lym)in the Mic and Mac groups were higher than those in the Con group(P＜0.05).The age,DM duration and hypertension duration in the Mic group were higher than those in the Con group(P＜0.05),and the hemoglobin(Hb)in the Mac group was lower than that in the Con group(P＜0.05).Logistic regression analysis showed that Hb,Lym,age,SBP,NLR,BUN,Scr,eGFR,SUA,CysC,DM duration,hypertension,hypertension duration,and the use of antihypertensive drugs were all influencing factors for the occurrence of DKD.After adjusting for multiple confounding factors,it was shown that NLR(OR 1.223,95%CI 1.082～1.382),SBP(OR 1.018,95%CI 1.005～1.031),and eGFR(OR 0.973,95%CI 0.954～0.991)remained the influencing factors of DKD.In male DKD patients across different age groups,with BMI＜29.9 kg/m2,non-smoking,non-drinking and without comorbid diabetic retinopathy and hypertension,the NLR was significantly higher compared to the Con group(P＜0.05).However,no interaction effects were observed between these variables and NLR in relation to DKD(P＞0.05).Conclusions NLR is closely related to the occurrence and development of DKD.

Objectives:To evaluate the biomechanics of a new self-developed bidirectional self-locking fusion device in vitro.Methods:12 fresh L3/4 segment specimens of domestic pig spine were randomly divided into 3 groups for modeling:normal group(intact state),traditional fusion device group(traditional fusion device and unilateral screw fixation)and new fusion device group(bidirectional self-locking fusion device implanted).On the basis of MTS multi-freedom(spinal motion)simulation test system and 500N preload,8N·m load was applied to experimental specimens in each direction successively,and the stability test was carried out according to the order of forward bending,backward extension,left bending,right bending,and left and right rotation.The ranges of motion(ROMs)were compared between groups under different working conditions.The axial fatigue compression test was carried out with TT-JQ-01-106 fatigue testing machine to evaluate the stability and reliability of the self-developed fusion device.Results:Compared with the normal group,the ROM of the new fusion device group was significantly decreased under the conditions of flexion(1.67°±0.65° vs 3.46°±0.16°),extension(1.43°±1.01° vs 1.89°±0.29°),left bending(2.07°±1.32° vs 3.08°±0.09°),right bending(1.38°±0.72° vs 4.37°±0.20°),and right rotation(2.17°±1.51° vs 5.10°±0.37°)(all P＜0.05);Under the left rotation condition,the ROM value(3.10°±1.57°)of the new device group was significantly higher than that of the normal group(2.36°±0.62°)(P＜0.05).Compared with the conventional fusion device group,the ROM of the new fusion device group was significantly increased under flexion(1.67°±0.65° vs 1.22°±0.76°)and left rotation(3.10°±1.57° vs 1.57°±0.91°)conditions(P＜0.05);However,there were no significant differences in ROMs between the two groups under extension(1.43°±1.01° vs 1.06°±0.50°),left bending(2.07°±1.32° vs 1.87°±1.41°),right bending(1.38°±0.72° vs 1.45°±0.69°),and right rotation(2.17°±1.51° vs 1.69°±1.07°)conditions(P＞0.05).The ROM values of the normal group under flexion,extension,left bending,right bending,and right rotation conditions were significantly higher than those of the other two groups(P＜0.05).Fatigue test:after 5 million load-displacement cycles,visual inspection revealed no deformation or cracks in the fusion device,and the axial compression fatigue test was passed.Conclusions:The bidirectional self-locking fusion device can obviously improve the stability of the fusion segment,which is equivalent to the stability of using the posterior single-sided nail rod system,meanwhile,it has good fatigue resistance,therefore its mechanical properties can meet the needs of clinical applications.