1.Atlantodentoplasty using the anterior retropharyngeal approach for treating irreducible atlantoaxial dislocation with atlantodental bony obstruction: a retrospective study
Jia SHAO ; Yun Peng HAN ; Yan Zheng GAO ; Kun GAO ; Ke Zheng MAO ; Xiu Ru ZHANG
Asian Spine Journal 2025;19(1):54-63
Methods:
The clinical data of 26 patients diagnosed with irreducible atlantoaxial dislocation complicated by atlantodental bony obstruction were analyzed retrospectively. All patients underwent anterior retropharyngeal atlantodentoplasty, followed by posterior occipitocervical fusion. Details including surgical duration and blood loss volume were recorded. Radiographic data such as the anterior atlantodental interval, O–C2 angle, space available for the cord, clivus–canal angle, and cervical medullary angle, and clinical data including the Japanese Orthopedic Association (JOA) score were assessed. The fusion time of the grafted bone and the development of complications were examined.
Results:
In patients undergoing anterior retropharyngeal atlantodentoplasty, the surgical duration and blood loss volume were 120.1±16.4 minutes and 100.6±33.5 mL, respectively. The anterior atlantodental interval decreased significantly after the surgery (p <0.001). The O–C2 angle, space available for the cord, clivus–canal angle, and cervical medullary angle increased significantly after the surgery (p <0.001). The JOA score during the latest follow-up significantly increased compared with that before the surgery (p <0.001). The improvement rate of the JOA score was 80.8%±18.1%. The fusion time of the grafted bone was 3–8 months, with an average of 5.7±1.5 months. In total, 11 patients presented with postoperative dysphagia and three with irritating cough. However, none of them exhibited other major complications.
Conclusions
Anterior retropharyngeal atlantodentoplasty can anatomically reduce the atlantoaxial joint with a satisfactory clinical outcome in patients with irreducible atlantoaxial dislocation with atlantodental bony obstruction.
2.Atlantodentoplasty using the anterior retropharyngeal approach for treating irreducible atlantoaxial dislocation with atlantodental bony obstruction: a retrospective study
Jia SHAO ; Yun Peng HAN ; Yan Zheng GAO ; Kun GAO ; Ke Zheng MAO ; Xiu Ru ZHANG
Asian Spine Journal 2025;19(1):54-63
Methods:
The clinical data of 26 patients diagnosed with irreducible atlantoaxial dislocation complicated by atlantodental bony obstruction were analyzed retrospectively. All patients underwent anterior retropharyngeal atlantodentoplasty, followed by posterior occipitocervical fusion. Details including surgical duration and blood loss volume were recorded. Radiographic data such as the anterior atlantodental interval, O–C2 angle, space available for the cord, clivus–canal angle, and cervical medullary angle, and clinical data including the Japanese Orthopedic Association (JOA) score were assessed. The fusion time of the grafted bone and the development of complications were examined.
Results:
In patients undergoing anterior retropharyngeal atlantodentoplasty, the surgical duration and blood loss volume were 120.1±16.4 minutes and 100.6±33.5 mL, respectively. The anterior atlantodental interval decreased significantly after the surgery (p <0.001). The O–C2 angle, space available for the cord, clivus–canal angle, and cervical medullary angle increased significantly after the surgery (p <0.001). The JOA score during the latest follow-up significantly increased compared with that before the surgery (p <0.001). The improvement rate of the JOA score was 80.8%±18.1%. The fusion time of the grafted bone was 3–8 months, with an average of 5.7±1.5 months. In total, 11 patients presented with postoperative dysphagia and three with irritating cough. However, none of them exhibited other major complications.
Conclusions
Anterior retropharyngeal atlantodentoplasty can anatomically reduce the atlantoaxial joint with a satisfactory clinical outcome in patients with irreducible atlantoaxial dislocation with atlantodental bony obstruction.
3.Atlantodentoplasty using the anterior retropharyngeal approach for treating irreducible atlantoaxial dislocation with atlantodental bony obstruction: a retrospective study
Jia SHAO ; Yun Peng HAN ; Yan Zheng GAO ; Kun GAO ; Ke Zheng MAO ; Xiu Ru ZHANG
Asian Spine Journal 2025;19(1):54-63
Methods:
The clinical data of 26 patients diagnosed with irreducible atlantoaxial dislocation complicated by atlantodental bony obstruction were analyzed retrospectively. All patients underwent anterior retropharyngeal atlantodentoplasty, followed by posterior occipitocervical fusion. Details including surgical duration and blood loss volume were recorded. Radiographic data such as the anterior atlantodental interval, O–C2 angle, space available for the cord, clivus–canal angle, and cervical medullary angle, and clinical data including the Japanese Orthopedic Association (JOA) score were assessed. The fusion time of the grafted bone and the development of complications were examined.
Results:
In patients undergoing anterior retropharyngeal atlantodentoplasty, the surgical duration and blood loss volume were 120.1±16.4 minutes and 100.6±33.5 mL, respectively. The anterior atlantodental interval decreased significantly after the surgery (p <0.001). The O–C2 angle, space available for the cord, clivus–canal angle, and cervical medullary angle increased significantly after the surgery (p <0.001). The JOA score during the latest follow-up significantly increased compared with that before the surgery (p <0.001). The improvement rate of the JOA score was 80.8%±18.1%. The fusion time of the grafted bone was 3–8 months, with an average of 5.7±1.5 months. In total, 11 patients presented with postoperative dysphagia and three with irritating cough. However, none of them exhibited other major complications.
Conclusions
Anterior retropharyngeal atlantodentoplasty can anatomically reduce the atlantoaxial joint with a satisfactory clinical outcome in patients with irreducible atlantoaxial dislocation with atlantodental bony obstruction.
4.Construction of CRMP1 lentiviral interference plasmid and its effect on expression of NLRP3 inflammasome protein in SH-SY5Y cells
Songhao WANG ; Kun QIN ; Yu HAN ; Weiwei ZHANG ; Shaoye XU ; Xiaoyun SHAO
Chinese Journal of Immunology 2025;41(2):433-438
Objective:To construct a lentiviral interference plasmid targeting collapse response regulatory protein 1(CRMP1)gene,to establish a human neuroblastoma cell line(SH-SY5Y)with stable CRMP1 knockdown,and to investigate its impact on expression of NLRP3 inflammasome protein.Methods:Double-stranded shRNA was designed and synthesized targeting h-CRMP1 mRNA sequence,and cloned into PLKO.1 vector.Recombinant shCRMP1 plasmids were constructed correctly,which was transfected into HEK-293T cells for lentiviral packaging.Obtained lentivirus supernatant was concentrated and then infected into SH-SY5Y cells.The interference effect of shCRMP1 plasmid and protein expressions of NLRP3 inflammasome components in SH-SY5Y cells were detected by Western blot.Results:DNA sequencing results showed that insertion sequences of recombinant interference plasmids pLKO.1-shCRMP1 were consistent with designed sequences,which confirmed successful construction of shCRMP1 lentivirus interfering plasmids and transfected into HEK-293T cells for lentivirus packaging,and protein level of CRMP1 in HEK-293T cells were decreased.SH-SY5Y cells were infected with lentivirus concentrate obtained from packaging and screened with puromycin.Western blot results showed that shCRMP1 recombinant lentiviral plasmids could significantly down-regulate CRMP1 protein expression in SH-SY5Y cells.It was also found that in SH-SY5Y cell line with stable CRMP1 knockdown,inhibition of CRMP1 expression could effectively inhibit NLRP3 inflammasome activation under MPP+induction.Conclusion:pLKO.1-shCRMP1 lentiviral interfering plas-mids have been successfully constructed,and interference with CRMP1 can inhibit activation of NLRP3 inflammasome in MPP+-in-duced SH-SY5Y cells.This study provides guidance for further research on mechanism of CRMP1 in neurodegenerative diseases such as Parkinson's disease.
5.Effect of exogenous luteinizing hormone on vitrification granulosa cells and its mechanism
Jie CHEN ; Shang GAO ; Shao-jie ZHANG ; Xi YANG ; Kun LI ; Jun SHI ; Xing WANG
Journal of Regional Anatomy and Operative Surgery 2025;34(1):1-5
Objective To investigate the effect of exogenous luteinizing hormone (LH) on vitrification granulosa cells and its mecha-nisms. Methods The granulosa cells of 4-week-old preadolescent mice were selected and divided into the fresh group (without vitrification procedure),the vitrification group (treated according to vitrification procedure) and the LH group (treated with 0.3 IU/L of LH intervention on the basis of the vitrification group). Granulocyte count was performed,and Realtime PCR and Western blot were used to detect the expression changes of Foxl2,PI3K,AKT and mTOR mRNAs and proteins in each group. Results Compared with the vitrification group,the total number of granulosa cells in the LH group was significantly increased (P<0.05),and the expression of Foxl2,PI3K,AKT and mTOR mRNAs and proteins were elevated (P<0.05). Conclusion The intevention of exogenous LH is beneficial for the survival of vitrifi-cation granulosa cells,and the mechanism may be related to the activation of PI3K/AKT/mTOR pathway.
6.Application progress of micro-CT and finite element analysis techniques in scaphoid bone research
Yuan LYU ; De-zhou ZHANG ; Hai-long QIAN ; Si-min WANG ; Chao-qun WANG ; Kun LI ; Jie CHEN ; Xue BAI ; Hai-long ZHAO ; Shao-jie ZHANG ; Yuan MA ; Zhi-jun LI ; Jun SHI ; Xing WANG
Journal of Regional Anatomy and Operative Surgery 2025;34(2):168-173
The scaphoid bone is one of the important bone of hand,which is frequently injured and difficult to treat in clinical practice.Therefore,it is very important to deeply study the microstructure and biomechanical characteristics of the scaphoid bone for understanding its injury mechanism and optimizing treatment scheme.Microcomputed tomography(micro-CT)provides high-resolution imaging of bone tissue,while finite element analysis can help to simulate the stress distribution and behavioral patterns of the scaphoid bone under various physiological and pathological states.The high-resolution three-dimensional image of the scaphoid bone obtained by micro-CT technology can be used to construct finite element models of real anatomical structure of the scaphoid bone,thus achieving accurate simulation of the mechanical properties of the scaphoid bone.The fusion of these two advanced technologies provides a new perspective for revealing the structural and functional relationships and injury mechanism of the scaphoid bone.Therefore,this paper reviews the anatomical characteristics of the scaphoid bone and its biomechanical behavior in different states,emphasizing the specific applications and advantages of micro-CT and finite element analysis techniques in the study of the scaphoid bone.By summarizing the research findings in recent years,this paper provides novel scientific basis and methods for the diagnosis,treatment,and prevention of scaphoid bone-related disorders.
7.Identification algorithm of disease severity in patients with acute respiratory distress syndrome based on ensemble learning
Peng-cheng YANG ; Xin SHAO ; Chun-chen WANG ; Kun BAO ; Yang ZHANG ; Shi-chen DU ; Hai-feng XU
Chinese Medical Equipment Journal 2025;46(2):1-9
Objective To propose a novel identification algorithm based on ensemble learning for assessing the severity of acute respiratory distress syndrome(ARDS)to achieve continuous monitoring of the disease severity.Methods Firstly,leve-raging the open-source MIMIC-Ⅳ database,a variety of non-invasive physiological parameters of patients were extracted and subjected to preliminary preprocessing.A multivariate feature selection algorithm was employed to rank these parameters and calculate feature importance scores through weighted computation.Secondly,based on the feature importance scores,a subset search algorithm was utilized to identify the subset of features that could yield optimal performance across four machine learning algorithms:neural networks,logistic regression,AdaBoost and XGBoost.Finally,a soft voting ensemble method was designed using a generalized linear regression model to integrate the results of each single machine learning algorithm,and a multivariate ensemble learning algorithm was proposed by combining the optimal feature subsets.The algorithm proposed when used to identify the severity of ADRS was evaluated with MIMIC-Ⅳ database,and compared with the traditional algorithms.Results The sensitivity,specificity,accuracy and AUC of the algorithm were 87.15%,89.23%,88.34%and 0.923 4,respectively,all of which outperformed those of the traditional algorithms.Conclusion The ARDS severity identification algorithm based on ensemble learning is capable of achieving continuous and real-time monitoring of the severity of ARDS,thereby offering robust support for the early identification and warning of ARDS in patients.[Chinese Medical Equipment Journal,2025,46(2):1-9]
8.Safety study of navigation-assisted medial “in-out-in” technique in C 2 screw fixation
Jia SHAO ; Yanzheng GAO ; Kun GAO ; Kezheng MAO ; Xiuru ZHANG
Chinese Journal of Surgery 2025;63(12):1146-1155
Objective:To evaluate the safety and clinical efficacy of the navigation-assisted medial “in-out-in” technique in C 2 pedicle screw fixation. Methods:This study is a retrospective cohort study. The clinical data of 68 patients with high-riding vertebral arteries of the axis who underwent C 2 pedicle screw implantation using the medial “in-out-in” technique in the Department of Spinal Surgery, Henan Provincial People′s Hospital from August 2020 to July 2023 were retrospectively analyzed. There were 32 males and 36 females, with an age of (56.9±10.2) years (range: 35 to 78 years). Among them, 36 patients underwent navigation-assisted medial “in-out-in” technique for C 2 pedicle screw implantation and were included in the navigation group; 32 patients received freehand screw placement and were included in the freehand group. The operative time, intraoperative blood loss, postoperative maximum pedicle-screw distance (PSD max), bone graft fusion time, fusion rate, and occurrence of internal fixation-related complications were recorded and compared between the two groups. The spinal cord cross-sectional area (SSC) was measured before surgery and at 1 week after surgery. The atlanto-dental interval (ADI), clivus-canal angle (CCA), and Japanese Orthopaedic Association (JOA) score were evaluated before surgery, at 1 week, 3 months, 1 year after surgery, and at the final follow-up. Independent sample t-test, repeated measures analysis of variance, paired t-test, χ2 test, or Fisher′s exact test were used for data comparison. Results:Six patients with reduction blocked by atlanto-dental osteophytes first underwent anterior cervical atlanto-dental arthroplasty, followed by posterior surgery in the prone position, while the remaining 62 patients underwent posterior reduction and internal fixation. All 36 patients in the navigation group successfully completed C 2 medial “in-out-in” screw implantation, including 34 cases with unilateral medial ”in-out-in” screw implantation and 2 cases with bilateral implantation. In the freehand group, 28 cases completed medial “in-out-in” screw implantation, with 4 cases (12.5%) of implantation failure; the implantation failure rate in the navigation group was lower than that in the freehand group ( χ 2=5.027, P=0.025). The posterior surgical time in the navigation group was shorter than that in the freehand group ((158.1±25.7) minutes vs. (176.4±27.6) minutes, t=2.829, P=0.006), while there was no statistically significant difference in intraoperative blood loss during posterior surgery between the two groups ((217.5±62.2) ml vs. (212.7±53.2) ml, t=0.340, P=0.735). There was no significant change in SSC before and after surgery in both groups (all P>0.05). The postoperative JOA scores, ADI, and CCA in both the navigation group and the freehand group were significantly improved compared with those before surgery (all P<0.01), and there were no differences between the two groups (all P>0.05). The postoperative PSD max was (4.7±0.9) mm and the bone graft fusion time was (4.9±1.3) months in the navigation group, compared with (4.8±0.5) mm and (4.9±1.7) months in the freehand group, respectively; there were no statistically significant differences between the two groups (all P>0.05). During pedicle preparation, 1 case (2.8%) in the navigation group and 3 cases (9.4%) in the freehand group developed cerebrospinal fluid leakage due to dural puncture by the hand drill. One patient in the freehand group developed symptomatic cerebral infarction postoperatively, presenting with dysarthria, which recovered after medical treatment. There was no significant difference in the incidence of cerebrospinal fluid leakage or vertebral artery injury between the two groups. Conclusion:The navigation-assisted medial “in-out-in” technique enables safe and rapid implantation of three-column fixation screws in patients with high-riding vertebral arteries of the axis, with high accuracy in screw placement and satisfactory clinical outcomes.
9.Spinal cord morphological changes and risk factors in upper cervical spine surgery using C 2 medial "in-out-in" pedicle screws
Xiuru ZHANG ; Yanzheng GAO ; Kun GAO ; Jia SHAO ; Kezheng MAO ; Zhongzheng GU
Chinese Journal of Orthopaedics 2025;45(6):351-360
Objective:To investigate spinal cord morphological changes and risk factors in upper cervical spine surgery using C 2 medial "in-out-in" pedicle screws in patients with atlantoaxial dislocation (AAD) and high-riding vertebral artery (HRVA). Methods:A retrospective analysis was conducted on 41 patients with AAD who underwent C 2 medial "in-out-in" pedicle screw implantation at our hospital between January 2019 and December 2023. The cohort included 12 males and 29 females, with a mean age of 47.6±10.3 years (range: 18-68 years). Among them, 30 patients received unilateral C 2 medial "in-out-in" screws, while 11 patients received bilateral screws. All patients underwent posterior reduction and internal fixation. Measurements included C 2 pedicle height, C 2 pedicle width, C 2 horizontal spinal canal width, screw invasion distance into the spinal canal, and spinal canal invasion rate based on CT findings. MRI evaluations included spinal canal-dura mater distance, dura mater-spinal cord distance, spinal canal-spinal cord distance, and spinal cord cross-sectional area. The change rate of spinal cord cross-sectional area was calculated and categorized into >20% decrease group (decreasing group) and ≤20% decrease group (non-decreasing group). Postoperative outcomes were assessed using the Visual Analogue Scale (VAS) and Japanese Orthopedic Association (JOA) scores. Results:The mean operative time was 165.5±30.1 minutes (range: 120-220 minutes). No spinal cord vascular injuries or severe complications were observed. However, five patients experienced cerebrospinal fluid (CSF) leakage, requiring delayed removal of drainage tubes, but their wounds healed successfully. Follow-ups (range: 6-24 months) showed no loosening of internal fixation, fractures, or bone graft nonunion, with a 100% bone fusion rate at 6 months postoperatively. VAS scores improved significantly from a preoperative median of 5.0 (3.5, 6.0) (range: 1-7) to 2.0 (2.0, 3.0) at 3 months and 1.0 (1.0, 1.0) at 6 months ( Z=36.716, P< 0.001). JOA scores improved from 10.0 (9.0, 12.0) (range: 4-14) preoperatively to 13.0 (11.0, 13.5) at 3 months and 14.0 (12.0, 15.0) at 6 months ( Z=67.093, P<0.001). The height of C 2 pedicle was 5.50±1.78 mm, the width of C 2 pedicle was 2.27±1.23 mm, the width of C 2 horizontal spinal canal was 23.76±4.91 mm, the spinal canal-dura mater distance was 3.08±0.85 mm, dura mater-spinal cord distance was 3.23±0.85 mm, the spinal canal-spinal cord distance was 6.31±1.11 mm, the distance of screw invasion into the spinal canal was 2.80±1.54 mm, the rate of spinal canal invasion was 12.1%±6.8%, the preoperative spinal cord cross-sectional area was 69.81±13.27 mm 2, and the postoperative spinal cord cross-sectional area was 68.81±13.94 mm 2. Based on spinal cord cross-sectional area changes, 32 patients were classified into the non-decreasing group, and 9 patients into the decreasing group. The intraclass correlation coefficient (ICC) values ranged from 0.733 to 0.984, indicating high measurement reliability. There were significant differences in the proportion of C 2 bilateral medial "in-out-in" screws (χ 2=6.903, P=0.009), the incidence of CSF leakage (χ 2=15.391, P<0.001), the distance of screw invasion into the spinal canal ( t=4.990, P<0.001) and the rate of spinal canal invasion ( t=4.045, P<0.001) in the decreasing group versus the non-decreasing group. The JOA scores of the non-decreasing group were significantly higher at 3 and 6 months postoperatively compared to the decreasing group ( P<0.05). No other parameters showed significant differences between the groups. Binary logistic regression analysis identified spinal canal invasion rate [ OR=1.963, 95% CI (1.010, 3.817), P=0.047] as an independent risk factor for spinal cord cross-sectional area reduction. The Jordan index was 0.875, with a spinal canal invasion rate threshold of 14.18%, a sensitivity of 1.000, a specificity of 0.875, and an AUC of 0.983, indicating strong predictive value. Conclusion:The C 2 medial "in-out-in" screw technique provides effective posterior fixation and fusion for AAD patients with HRVA. However, to minimize spinal cord morphological changes and associated risks, the spinal canal invasion rate should be kept below 14.18% when using this technique.
10.Spinal cord morphological changes and risk factors in upper cervical spine surgery using C 2 medial "in-out-in" pedicle screws
Xiuru ZHANG ; Yanzheng GAO ; Kun GAO ; Jia SHAO ; Kezheng MAO ; Zhongzheng GU
Chinese Journal of Orthopaedics 2025;45(6):351-360
Objective:To investigate spinal cord morphological changes and risk factors in upper cervical spine surgery using C 2 medial "in-out-in" pedicle screws in patients with atlantoaxial dislocation (AAD) and high-riding vertebral artery (HRVA). Methods:A retrospective analysis was conducted on 41 patients with AAD who underwent C 2 medial "in-out-in" pedicle screw implantation at our hospital between January 2019 and December 2023. The cohort included 12 males and 29 females, with a mean age of 47.6±10.3 years (range: 18-68 years). Among them, 30 patients received unilateral C 2 medial "in-out-in" screws, while 11 patients received bilateral screws. All patients underwent posterior reduction and internal fixation. Measurements included C 2 pedicle height, C 2 pedicle width, C 2 horizontal spinal canal width, screw invasion distance into the spinal canal, and spinal canal invasion rate based on CT findings. MRI evaluations included spinal canal-dura mater distance, dura mater-spinal cord distance, spinal canal-spinal cord distance, and spinal cord cross-sectional area. The change rate of spinal cord cross-sectional area was calculated and categorized into >20% decrease group (decreasing group) and ≤20% decrease group (non-decreasing group). Postoperative outcomes were assessed using the Visual Analogue Scale (VAS) and Japanese Orthopedic Association (JOA) scores. Results:The mean operative time was 165.5±30.1 minutes (range: 120-220 minutes). No spinal cord vascular injuries or severe complications were observed. However, five patients experienced cerebrospinal fluid (CSF) leakage, requiring delayed removal of drainage tubes, but their wounds healed successfully. Follow-ups (range: 6-24 months) showed no loosening of internal fixation, fractures, or bone graft nonunion, with a 100% bone fusion rate at 6 months postoperatively. VAS scores improved significantly from a preoperative median of 5.0 (3.5, 6.0) (range: 1-7) to 2.0 (2.0, 3.0) at 3 months and 1.0 (1.0, 1.0) at 6 months ( Z=36.716, P< 0.001). JOA scores improved from 10.0 (9.0, 12.0) (range: 4-14) preoperatively to 13.0 (11.0, 13.5) at 3 months and 14.0 (12.0, 15.0) at 6 months ( Z=67.093, P<0.001). The height of C 2 pedicle was 5.50±1.78 mm, the width of C 2 pedicle was 2.27±1.23 mm, the width of C 2 horizontal spinal canal was 23.76±4.91 mm, the spinal canal-dura mater distance was 3.08±0.85 mm, dura mater-spinal cord distance was 3.23±0.85 mm, the spinal canal-spinal cord distance was 6.31±1.11 mm, the distance of screw invasion into the spinal canal was 2.80±1.54 mm, the rate of spinal canal invasion was 12.1%±6.8%, the preoperative spinal cord cross-sectional area was 69.81±13.27 mm 2, and the postoperative spinal cord cross-sectional area was 68.81±13.94 mm 2. Based on spinal cord cross-sectional area changes, 32 patients were classified into the non-decreasing group, and 9 patients into the decreasing group. The intraclass correlation coefficient (ICC) values ranged from 0.733 to 0.984, indicating high measurement reliability. There were significant differences in the proportion of C 2 bilateral medial "in-out-in" screws (χ 2=6.903, P=0.009), the incidence of CSF leakage (χ 2=15.391, P<0.001), the distance of screw invasion into the spinal canal ( t=4.990, P<0.001) and the rate of spinal canal invasion ( t=4.045, P<0.001) in the decreasing group versus the non-decreasing group. The JOA scores of the non-decreasing group were significantly higher at 3 and 6 months postoperatively compared to the decreasing group ( P<0.05). No other parameters showed significant differences between the groups. Binary logistic regression analysis identified spinal canal invasion rate [ OR=1.963, 95% CI (1.010, 3.817), P=0.047] as an independent risk factor for spinal cord cross-sectional area reduction. The Jordan index was 0.875, with a spinal canal invasion rate threshold of 14.18%, a sensitivity of 1.000, a specificity of 0.875, and an AUC of 0.983, indicating strong predictive value. Conclusion:The C 2 medial "in-out-in" screw technique provides effective posterior fixation and fusion for AAD patients with HRVA. However, to minimize spinal cord morphological changes and associated risks, the spinal canal invasion rate should be kept below 14.18% when using this technique.

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