BACKGROUND:At present,experimental animal models of primate idiopathic scoliosis with erect feet have not been established.With rapid development of computer and imaging,we can use computer software to simulate models of human idiopathic scoliosis,and do relevant biomechanical analysis and provide instructions for clinical surgery operation.OBJECTIVE:To research the best surgical fusion level for the adolescent idiopathic scoliosis (AIS) of PUMC Ⅱ d_2 with the finite element model (FEM).DESIGN,TIME AND SETTING:The compadson observation was performed at the Department of Orthopedics,Beijing Union Hospital from May 2007 to May 2008.PARTICIPANTS:One female patient with PUMC Ⅱ d_2 scoliosis (double curve malformation) was included.METHODS:FEM (T5-S) of PUMC Ⅱ d_2 idiopathic scoliosis was used to simulate upper thoracic curve,lower lumbar curve and double curve fusion manners.Hollow lateral curvature pedicle of vertebral arch received 50,100,150 N load.Displacement of T_5 and T_(11) on upper sagittal plane (displacement of Z axis positive value on upper sagittal plane,displacement of negative value on lower sagittal plane) and their difference value were compared.T_5 displacement represented outcomes of double curve orthopaedics.T_(11) displacement represented outcomes of lower lumbar curve orthopaedics.Their difference value (T5-T11) represented outcomes of upper thoracic curve orthopaedics.MAIN OUTCOME MEASURES:Different fusion segments and displacement of T_5 and T_(11) under different orthopedic forces were measured.RESULTS:In PUMC Ⅱ d_2 lateral curvature,T_5 displacement on Z axis:fusion displacement of double curves was greater compared with upper curve alone or lower curve alone (P < 0.01 ).Difference of T_5-T_(11) displacement:double curves orthopaedics > upper thoracic curve orthopaedics alone > lower lumbar curve orthopaedics alone (P < 0.01).Displacement of T_(11) on Z axis:double curves orthopaedics > lower lumbar curve orthopaedics alone > upper thoracic curve orthopaedics alone (P < 0.01).CONCLUSION:Fusing two curves would get the best effect on the AIS of PUMC Ⅱ d_2 compared with upper curve alone or lower curve fusion alone.Effects of 3 kinds of load on correction of upper thoracic curve:double curve orthopaedics < upper thoracic curve orthopaedics alone > lower lumbar curve orthopaedics alone.Effect of 3 kinds of load on correction of lower lumbar curve orthopaedics alone:double curve orthopaedics > lower lumbar curve orthopaedics alone > upper thoracic curve orthopaedics alone.Three-dimensional finite element analysis is an effective method to analyze biomechanics of scoliosis deformity correction and provides a virtual non-invasive verification manner,and can optimize surgery scheme.

Objective To study the mechanism of p55 inducing cell apoptosis, the 180 bp fragment of Puma promoter was cloned into the pGL3-basic luciferase reporter vector. The biological activity of Pumareporter plasmid was verified by cell transfection. Methods The target fragments of Puma were amplified by RT-PCR method and the fragments were inserted into the pGL3-basic luciferase reporter vector. The acquired Puma-Luc plasmid was transfected into H1299 cell line and detected its activity. Results Sequencing indicated that the amplified Puma promoter is correct. Dual-luciferase Reporter Assay showed the Puma-Luc constructs have promoter activity. Conclusion The cloning of human Puma gene promoter and the construction of its reporter vector were successful. This study will lay the foundation for further research on the function of p53 inducing apoptosis through mitochondrial pathway.

Objective To explore the effect of resveratrol ( Rev) as an antioxidant on oxidative damage to HepaRG cells induced by troglitazone ( Tro).Methods Cells were divided into five groups: control ( RPMI 1640 only with 0.1%DMSO), Tro(50 μmol/L), Tro(50 μmol/L) +Rev(15 μmol/L), Tro(50 μmol/L) +Rev(7.5 μmol/L) and Tro (50 μmol/L)+Rev(3.75 μmol/L) groups.MTT assay was performed to detect the viability of Rev-treated, Tro-treated and Rev with 50 μmol/L Tro-treated HepaRG cells.After 48 hours, the level of reactive oxygen species (ROS) and lipid oxidation ( malondialdehyde , MDA ) , degree of apoptosis , total antioxidant capacity , activity of hydrogenperoxidase (catalase, CAT), glutathione peroxidase (GSH-px) and superoxide dismutase(SOD)of these groups were identified. Results Tro could obviously cause HepaRG cells to produce oxidative stress .Compared with control group ,ROS and lipid peroxidation ( MDA) levels and the rate of apoptosis and necrosis in Tro-treated group were significantly increased ( P<0.05),total antioxidant capacity greatly reduced (P<0.05),and the activity of CAT,GSH-px and SOD was decreased (P<0.05).After adding various concentrations of Rev interaction , ROS and MDA production volume decreased (P < 0.05), and the apoptosis and necrosis rate correspondingly declined (P<0.05).Total antioxidant capacity of the cells and the activity of the three antioxidant enzymes were increased (P<0.05), and there was a dose-dependent relationship. Conclusion Tro can cause HepaRG cells to produce significant oxidative stress while Rev can significantly improve the oxidative damage of Tro to HepaRG cells .

Objective To investigate the clinical efficacy of short segment fixation with percutaneous pedicle screws or traditional open surgery for the type A1-A3 thoracolumbar compression fracture.Methods A retrospective case control study was conducted on the clinical data of 64 patients with thoracolumbar compression fracture admitted to Shanxi Dayi Hospital between January 2012 and February 2017.There were 44 males and 20 females,aged 21-65 years [(45.4 ± 11.1) years].There was one patient with injured segment at T11,29 at T12,27 at L1 and seven at L2.According to AO typing,there were 39 patients classified as Type A1,two as Type A2 and 23 as Type A3.The patients were divided into minimally invasive surgery group (n =37) and open surgery group (n =27).Minimally invasive surgery group was treated with minimally invasive percutaneous pedicle screw fixation and open reduction.The open surgery group was treated with traditional open pedicle screw short segment fixation and open reduction.The operation time,intraoperative blood loss,total hospitalization time,postoperative hospitalization time,visual analogue scale (VAS) before and after operation,local kyphosis of the fractured vertebra,segmental kyphosis and complications in two groups were recorded.Results All patients were followed up for 12-29 months,with an average of 13.2 months.Between the minimally invasive surgery group and open surgery group,no significant difference was found in the operation time [(106.4± 37.3) minutes vs.(131.3 ± 33.6) minutes] (P ＞ 0.05),and significant differences were found in intraoperative blood loss [(71.2 ± 34.9) ml vs.(409.3 ± 267.5) ml],total hospitalization time [(11.7 ± 7.2) days vs.(21.6 ± 12.8) days] and postoperative hospitalization time [(8.1 ± 7.4) days vs.(16.6 ± 10.6) days] (P ＜ 0.05).In the minimally invasive surgery group,VAS was (6.5 ±1.1) points preoperatively and was (2.3 ± 0.7) points and (1.0 ± 0.3) points immediately after operation and at final follow-up.In the open surgery group,VAS was (6.9 ± 1.0)points preoperatively and was (4.2 ± 1.0) points and (0.9 ± 0.4) points immediately after operation and at final follow-up (P ＜0.05).Compared with the preoperative VAS,those immediately after operation and at final follow-up were significantly decreased within the two groups (P ＜ 0.05).There were no significant differences in the preoperative VAS and VAS at final follow-up between the two groups (P ＞ 0.05),but significant difference was found in VAS immediately after operation between the two groups (P ＜ 0.05).In the minimally invasive surgery group,the local kyphosis of the fractured vertebra was (19.3 ± 3.8) °preoperatively,(3.4 ± 1.7) ° immediately after operation,and (4.6 ± 1.9) ° at final follow-up.In the open surgery group,the local kyphosis of the fractured vertebra was (19.6 ± 6.8) ° before operation,(1.6 ± 0.8) ° immediately after operation,and (2.4 ± 1.1) ° at final follow-up.The kyphosis of fractured vertebra immediately after operation and at final follow-up were significantly decreased within the two groups compared with the preoperative kyphosis(P ＜0.05),but no significant differences were found between the two groups (P ＞ 0.05).In the minimally invasive surgery group,the segmental kyphosis Cobb angle was (16.1 ± 9.1) ° before operation,(3.0-± 1.8) ° immediately after operation,and (5.9 ±1.8) ° at final follow-up.In the open surgery group,the segmental kyphosis Cobb angle was (15.2±12.0) ° before operation,(3.1 ± 1.4) ° immediately after operation,and (5.6 ± 2.1) ° at final follow-up.The segmental kyphosis Cobb angle immediately after operation and at final follow-up were significantly decreased within the two groups compared with the preoperative Cobb angle (P ＜ 0.05),but no significant differences were found between the two groups (P ＞ 0.05).No spinal cord injuries because of pedicle screws were observed after operation in either group.In the open surgery group,there was one patient with wound infection who recovered after dressing change,and no infection case was found in the minimally invasive surgery group.Conclusion For type A1-A3 thoracolumbar compression fractures,both the minimally invasive posterior pedicle screw fixation and the traditional open pedicle screw fixation can achieve satisfactory near-term results,and the former is better in intraoperative blood loss,immediate relief of pain after operation and shorter hospital stay than the latter.

Objective:To evaluate the value of 68Ga-labeled prostate-specific membrane antigen( 68Ga-PSMA PET/CT)in the diagnosis of prostate cancer(PCa) and determination of the strategy on neurovascular bundle(NVB)preservation and lymphadenectomy before surgery. Methods:We retrospectively analyzed the clinical data of 46 patients with newly diagnosed PCa who underwent 68Ga-PSMA PET/CT from June 2018 to October 2019. The median age was 66.50 (60.00, 69.25) years old and the median PSA was 15.97(8.58, 33.10)ng/ml. Forty-one patients were diagnosed PCa and 5 were diagnosed with benign prostatic hyperplasia or prostatitis by 68Ga-PSMA PET/CT, 6 were diagnosed with lymph nodes metastasis. Forty patients underwent mpMRI, 33 were diagnosed PCa, and 6 were diagnosed with lymph nodes metastasis. Seventeen patients underwent 11C-choline PET/CT, 12 were diagnosed PCa, and 4 were diagnosed with lymph nodes metastasis. Among the 41 patients which were diagnosed PCa by 68Ga-PSMA PET/CT, 26 were confirmed with PCa by needling biopsy, 12 did not undergo the needling biopsy and 3 had negative biopsy; 22 were in the high-risk group, and 19 were in the low- and medium-risk group. All 41 patients underwent radical prostatectomy. The strategy of NVB preservation was determined by the position of the PCa reported by 68Ga-PSMA PET/CT. If the tumor was close to the unilateral prostate capsule, the healthy part of the NVB would be preserved. And if the tumor was limited in the prostate gland, bilateral NVB would be preserved. The NVB was preserved in 16 cases(6 cases unilateral and 10 cases bilateral). In addition to routine lymph node dissection for patients in the high-risk group, lymph node dissection was also performed on patients with 68Ga-PSMA PET/CT that showed positive lymph nodes in the low- and medium-risk groups. The paired chi-square or Fisher exact test was used to compare the sensitivity and specificity of 68Ga-PSMA PET/CT, mpMRI, and 11C-choline PET/CT for lesion detection. Spearman analysis was used to examine the correlation between the SUV max, Gleason score, and the PSA value before treatment. Results:Forty-one patients undergoing radical resection were diagnosed PCa by postoperative pathology, and no cancer tissue was observed at the surgical margin; the median Gleason score was 8(7, 9); 20 cases (48.8%) had a pathological stage ≤pT 2c; 21 cases (51.2%)≥pT 3; 7 cases were N+ (11 positive lymph nodes). Seven cases (17.1%) had complications of Clavien-Dindo ≤ grade 2 within 30 days after surgery, and there was no complication above grade 3 after surgery. The median follow-up time of the 41 patients was 16(12, 20). The rate of urinary control was 46.3%, 95.1%, and 100% after 1 month, 6 months, and 12 months follow-up respectively. Among the five patients that did not undergo surgery, the PSA value of 4 decreased after antibiotic treatment, and biopsy was performed in 1 case without PSA decreasing, and no carcinoma was found. The sensitivity of 68Ga-PSMA PET/CT on the primary PCa was 100%(41/41), which was significantly better than that of 11C-choline(80%, 12/15, P=0.016)and mpMRI (83.7%, 31/37, P=0.009), while no statistical significance was observed between the specificity of 68Ga-PSMA PET/CT (5/5)and 11C-choline PET/CT(2/2, P=1.000), 68Ga-PSMA PET/CT and mpMRI(1/3, P=0.107). Of the 41 patients that were diagnosed with PCa, the sensitivity of 68Ga-PSMA PET/CT to lymph nodes metastases(71.4%, 5/7) had a significant difference with that of mpMRI(16.7, 1/6, P=0.016), but no statistical difference with 11C-choline (75%, 3/4, P=1.000). Analysis of the relationship between SUV max of 68Ga-PSMA PET/CT, Gleason score, and PSA value before treatment revealed that the SUV max of 68Ga-PSMA PET/CT in patients with Gleason score ≥8 and <8 score were 19.60(9.58, 24.38) and 8.55 (5.18, 12.88); SUV max of patients with PSA values ≥20 ng/ml and <20 ng/ml before treatment were 19.40 (13.00, 23.50) and 8.40 (5.35, 13.95), respectively, the differences were statistically significant (all P<0.05). Conclusions:68Ga-PSMA PET/CT had high sensitivity and specificity for the diagnosis of primary prostate cancer lesions, but the sensitivity for the diagnosis of lymph node metastasis was not enough to guide the preoperative decision of whether to remove the lymph node and the scope of the removal. However, the treatment strategy of whether to retain NVB could be formulated according to the tumor location displayed by 68Ga-PSMA PET/CT before surgery.

Objective To investigate the therapeutic influence of short segment fixation with navigated percutaneous pedicle screws in the treatment of thoracolumbar compression fracture and whether use of pedicle screw fixation affects the treatment efficacy.Methods A retrospective case control study was conducted on the clinical data of 38 patients with thoracolumbar compression fracture admitted between January 2014 and October 2016.There were 27 males and 11 females,with an average age of 35.9 years (range,21-59 years).There were 14 cases with injured segment at T12,14 cases at L1,and 10 cases at L2,all of which were classified as Type A according to AO typing.The patients were divided into screw group (n =22) and non-screw group (n =16).The pedicle screws were placed into the upper and lower adjacent segments of the fracture vertebra or the fracture vertebra by percutaneous fluoroscopyguided navigation.The operation time,intraoperative blood loss,Visual analogue scale (VAS) before and after operation,anterior vertebral body height,Cobb angle,and complications in two groups were recorded.Results All patients were followed up for 12-30 months,average 15.2 months.No significant differences were found between the screw group and the non-screw group with respect to operation time [(44.7 ±12.6)minutes vs.(39.3 ±11.9)minutes] and blood loss [(56.8 ±13)ml vs.(48.4 ± 11.0)ml](P ＞0.05).In the screw group,preoperative VAS was (6.7 ± 1.5) points,and VAS at postoperative 1 week,six months and 1 year were (2.3 ± 0.9) points,(1.1 ± 0.3) points and (0.9 ± 0.5) points,respectively (P ＜ 0.01).In the non-screw group,preoperative VAS was (6.1 ± 1.7) points,and VAS at postoperative 1 week,six months and 1 year were (2.1 ± 0.8) points,(1.2-± 0.6) points and (1.0-±0.6) points,respectively (P ＜0.01).No significant difference was found on VAS between the two groups (P ＞ 0.05).In the screw group,anterior vertebral body height was (59.5 ±-1 3.6) ％ preoperatively,and anterior vertebral body height at postoperative 1 week,six months and 1 year was (90.6±7.7)％,(89.3 ±8.3)％ and (88.4 ±7.9)％ (P＜0.01).In the non-screw group,preoperative anterior vertebral body height was (60.1 ± 12.5)％,and anterior vertebral body height at postoperative 1 week,six months and 1 year was (89.3 ±8.9)％,(88.4 ±9.1)％ and (86.5 ±8.7)％ (P ＜0.01).No significant difference was found on anterior vertebral body height between the two groups (P＞0.05).In the screw group,preoperative Cobb angle was (15.6 ±4.1)°,and Cobb angle at postoperative 1 week,six months and 1 year was (3.0 ±1.8)°,(5.0 ±1.9) ° and (5.9 ±1.8)°,respectively (P ＜ 0.01).In the non-screw group,preoperative Cobb angle was (16.2 ± 5.1) °,and Cobb angle at postoperative 1 week,six months and 1 year was (3.1 ±1.4)°,(5.2 ±2.3)° and (5.6 ± 2.1) °,respectively (P ＜ 0.01).No significant difference was found on Cobb angle between the two groups (P ＞ 0.05).No spinal cord injuries because of pedicle screws were observed after operation in both groups.Conclusions For thoracolumbar compression fracture,short segment fixation with navigated percutaneous pedicle screws has the advantages of shorter operation time,less bleeding,better postoperative pain relief,and fewer complications.In addition,the postoperative VAS,anterior vertebral body height and sagittal Cobb angle are improved significantly.However,use of pedicle screw fixation in fracture vertebra does not have significant influence on the treatment efficacy.

Objective: To investigate the clinical effect of posterior unilateral short segment screw fixation and bone graft fusion in the treatment of special upper cervical spine injuries. Methods: A retrospective case series study was conducted to analyze the clinical data of 15 patients with upper cervical spine injury admitted to Shanxi Bethune Hospital from July 2012 to May 2017. There were nine males and six females, aged 10-69 years [(41.9±20.9)years]. There were eight patients with traumatic atlantoaxial dislocation, one with congenital atlantoaxial dislocation, two with atlantoaxial dislocation with nonunion of odontoid process, three with Anderson type II odontoid process fracture, and one with old odontoid process fracture. All patients had cervico-occipital pain to different degrees, slender unilateral pedicle and distinct stenosis of vertebral artery. All patients were treated with posterior unilateral screw fixation and bone graft fusion. The injury of spinal cord and vertebral artery, operation time and intraoperative blood loss were recorded. Visual analogue scale (VAS) was used to evaluate pain before and after operation, and Japanese Orthopaedic Association (JOA) score was used to evaluate spinal cord function and postoperative improvement rate before and at the last follow-up. The position of internal fixation and fusion of bone graft were observed by X-ray after operation. Results: All 15 patients were followed up for 6-36 months [(20.4±8.6)months]. All the screws were implanted successfully at the first time, without spinal cord or vertebral artery injury. The operation time was 100-210 minutes [(131.3±32.0)minutes], and the intraoperative blood loss was 100-450 ml [(203.1±104.0)ml]. Preoperative VAS score was (7.9±0.9)points, and postoperative VAS score was (3.7±0.8)points (P<0.01). Preoperative JOA score was (12.1±4.4)points, and the JOA score at postoperative follow-up was (16.1±1.4)points, with the improvement rate of 68%. Postoperative X-ray showed good recovery of cervical spine sequence. One patient developed loosened internal fixation after the neck brace protection was removed one month after surgery, and the patient recovered after timely second surgical fixation and fusion. The remaining 14 patients did not have loosened internal fixation, fracture or loss of reduction, with bone fusion 6-12 months after surgery. Conclusion Posterior cervical unilateral short-segment screw fixation and bone graft fusion can restore cervical stability, relieve pain, and improve function recovery, which can be used as a complementary procedure to treat upper cervical spine injury with anatomic structure variation.

Objective:To compare perioperative differences between posterior lumbar interbody fusion(PLIF)by a posterior median approach or open transforaminal lumbar interbody fusion(TLIF)and minimally invasive surgery TLIF(MIS-TLIF)by a paravertebral approach for lumbar spondylolisthesis(Ⅰ~Ⅱ°)in elderly patients.Methods:A retrospective study was conducted to analyze clinical data of patients aged 60 years and over with lumbar spondylolisthesis(n=68)who underwent PLIF or MIS-TLIF from January 2014 to December 2017.Patients were divided into the PLIF group(n=40, 12 males and 28 females)and the MIS-TLIF group(n=28, 6 males and 22 females)according to the type of surgery.Differences in operating time, blood loss, exposure frequency, postoperative drainage volume, indwelling duration, hospital stay length and complications were compared between the groups.Results:There was no significant difference in operative time between the PLIF group and the MIS-TLIF group(156±51)min vs.(153±38)min( P=0.77). There were significant differences in intraoperative blood loss and radiation exposure frequency between the PLIF group and the MIS-TLIF group(458±272)ml vs.(157±104)ml( P<0.001); (6.7±1.5)times vs.(30.6±6.9)times( P<0.01). There was no significant difference in intraoperative complications between the PLIF group and the MIS-TLIF group(25% or 10/40 vs.7.1% or 2/28, P=0.057). There were more postoperative drainage, longer indwelling time and hospitalization in the PLIF group than in the MIS-TLIF group(664±351)ml vs.(210±127)ml( P<0.001); (3.7±2.9)d vs.(2.2±0.8)d( P=0.002); (9.2±3.6)d vs.(6.9±1.7)d( P=0.001). The incidence of postoperative neurological complications was not significantly different between the PLIF group and the MIS-TLIF group(7.5% or 3/40 vs.14.3% or 4/28, P=0.365). The incidence of postoperative non-neurological complications was higher in the PLIF group than in the MIS-TLIF group(27.5% or 11/40 vs.7.1% or 2/28, P=0.036). Conclusions:Compared with PLIF, MIS-TLIF has the advantages of less intraoperative bleeding and postoperative drainage, shorter indwelling duration of urinary catheters, shorter hospital stays and fewer complications of non-neurological complications in treating Ⅰ-Ⅱ degree lumbar spondylolisthesis in the elderly, but it requires more radiation exposure.

Objective:To explore the risk factors of surgical site infection after posterior lumbar interbody fusion and internal fixation in elderly patients with lumbar degenerative diseases.Methods:The clinical data of elderly patients who underwent posterior lumbar interbody fusion and internal fixation for degenerative diseases of lumbar spine in Department of Orthopedics, Shanxi Bethune Hospital from January 2019 to December 2021 were retrospectively analyzed.Eighteen elderly patients with postoperative incision infection were included into the infection group, and according to the ratio of 1∶3, 54 elderly patients without incision infection during the same period were randomly selected and included in the non-infection group.The general data of patients, surgical related data and perioperative laboratory indexes were compared between groups using univariate analysis.The screened out indicators with close correlation with incision infection and with significantly statistical significance were included in binary Logistic regression analysis.Risk factors related to postoperative incision infection were analyzed by receiver operating characteristic curve(ROC).The quantitative data of risk factors related to postoperative incision infection were selected for receiver operating characteristic curve(ROC)analysis.Results:When comparing the infected versus non-infected groups, the operative time was(197.1±39.5)min vs.(171.4±37.2)min, preoperative lymphoid count was(1.6±0.5)×10 9/L vs.(1.9±0.6)×10 9/L, and postoperative neutrophil count was[(7.2(6.2-9.5)×10 9/L vs.6.3(4.8-7.2)×10 9/L], percentage of neutrophils(82.5±8.8), % vs.(71.1±6.7), percentage of lymphocytes(1.1±0.6)×10 9/L vs.(1.7±0.7)×10 9/L, percentage of lymphocytes(11.0±5.6)% vs.(19.8±6.0)%, number of neutrophils vs.Lymphocyte count ratio(NLR)[8.5(5.2-15.0) vs.3.6(2.6-4.9)]and serum albumin concentration(31.4±2.5)g/L vs.(33.3±2.4)g/L, all P<0.05).Logistic regression analysis showed that diabetes mellitus( OR=6.649, 95% CI: 1.233-35.853), operation time( OR=1.025, 95% CI: 1.004-1.047), and percentage of postoperative neutrophils( OR=1.261, 95% CI: 1.125-1.414)were independent risk factors of incision infection after posterior interbody fusion and internal fixation in patients with lumbar degenerative diseases(all P<0.05).ROC analysis showed that the area under the curve of operation time was 0.680, and the cut-off value was 177.5 min.The area under the curve of the percentage of neutrophils after operation was 0.841, and the cut-off value was 78.85%. Conclusions:In patients with posterior interbody fusion and internal fixation for lumbar degenerative diseases complicated with diabetes, long operation time, and increased percentage of neutrophils after surgery can independently increase the risk of incision infection.

BACKGROUND:The angle of screw placement in anterior cervical discectomy and fusion plays a crucial role in determining the stability of the internal fixation system. OBJECTIVE:To predict the impact of different screw placement angles on the stress experienced by the internal fixation system in anterior cervical discectomy and fusion utilizing finite element analysis,with the ultimate goal of identifying the optimal screw placement angle. METHODS:A three-dimensional reconstruction method was employed to establish a mechanical model of the cervical spine,enabling the simulation of three distinct working conditions:scoliosis,uprightness,and forward flexion.In SolidWorks 2017,the anterior cervical plate and screw models were built according to different placement angles of the screws,with a as the inward offset,b as the ideal position,c as the outward offset,d as the downward offset,and e as the upward offset.The stress distribution of internal fixation system at different screw placement angles was observed,and the stress and displacement were recorded. RESULTS AND CONCLUSION:(1)By constructing a finite element model of the entire cervical spine and incorporating an anterior titanium plate,it was found that the biomechanical changes in the spine did not significantly differ based on the various angles of screw insertion on the titanium plate under the same working conditions.(2)However,microscopic analysis revealed that the outward offset(c)screw position exhibited the most effective resistance against side bending,while the downward offset(d)screw demonstrated optimal load-bearing capacity in the upright condition.Additionally,the outward deviation(c)screw displayed superior anti-bending effects in the reverse buckling condition.(3)The fixation effect of the internal fixation device remained relatively stable across different motion conditions.Although there was a 10％variation in the internal fixation effect under the three working conditions when the screw was placed inward,outward,downward,or upward,the displacement changes were minimal.These findings suggest that the requirements of load bearing,bending resistance,and flexion resistance could be simultaneously met without a specific optimal screw location in clinical practice.(4)The placement direction of titanium plate screw in anterior cervical disc-resection and fusion has little effect on the mechanical stability of the cervical spine.The screw angles in different directions have little influence on the stability of the internal fixation device in the lateral,upright,and forward flexion movements of the cervical spine.There is no need to pursue the direction of screw placement in clinical operations.