Objective
To compare the biomechanical properties of the anterior transpedicular screw-artificial vertebral body (AVB) and conventional anterior screw plate system (AP) in lower cervical spine by finite element study.
Methods
CT images (C1-T1) were obtained from a 38-year-old female volunteer. The models of intact C3-7 (intact group), AP fixation (AP group), and AVB fixation (AVB group) were established and analyzed by Mimics 14.0, Geomagic Studio 2013, and ANSYS 14.0 softwares. The axial force of 74 N and moment couple of 1 N·m were loaded on the upper surface and upper facet joint surfaces of C3. Under conditions of flexion, extension, lateral bending, and rotation, the Von Mises stress distribution regularity and maximum equivalent stree of AP and AVB groups were recorded, and the range of motion (ROM) was also analyzed of 3 groups.
Results
The intact model of lower cervical spine (C3-7) was established, consisting of 286 382 elements and 414 522 nodes, and it was successfully validated with the previously reported cadaveric experimental data of Panjabi and Kallemeyn. The stress concentrated on the connection between plate and screw in AP group, while it distributed evenly in AVB group. Between AP and AVB groups, there was significant difference in maximum equivalent stress values under conditions of 74 N axial force, flexion, extension, and rotation. AVB group had smaller ROM of fixed segments and larger ROM of adjacent segments than AP group. Compared with intact group, whole ROM of the lower cervical spine decreased about 3°, but ROM of C3, 4 and C6, 7 segments increased nearly 5° in both AP and AVB groups.
Conclusion
As a new reconstruction method of lower cervical spine, AVB fixation provides better stability and lower risk of failure than AP fixation.
ObjectiveTo investigate the safety and effectiveness of pedicle screw implantation via vertebral arch-transverse pathway in clinical application by a prospective randomized controlled trial.MethodsTwenty-four patients who were admitted between May 2015 and June 2017 and met the selection criteria for thoracic pedicle screw fixation were included in the study. According to the random number table method, they were divided into the trial group (screw implantation via vertebral arch-transverse pathway) and the control group (traditional screw implantation technology), with 12 patients in each group. There was no significant difference between the two groups in age, gender, cause of injury, injured segment, and the interval between injury and operation (P>0.05). The time of screw implantation was recorded and compared between the two groups. The acceptable rate of screw implantation and the penetration rate of pedicle wall were calculated after operation.ResultsThe time of screw implantation of trial group was (5.08±1.74) minutes, which was significantly shorter than that of control group [(5.92±1.66) minutes], and the difference was significant (t=4.258, P=0.023). Patients in both groups were followed up 1-2 years, with an average of 1.5 years. During the follow-up, no failure of internal fixation occurred. At 1 week after operation, the screw implantation in trial group was rated as gradeⅠin 54 screws, gradeⅡ in 3 screws, and grade Ⅲ in 2 screws, with the acceptable rate of 93.61%. The screw implantation in control group was rated as gradeⅠin 40 screws, grade Ⅱin 10 screws, grade Ⅲ in 8 screws, and grade Ⅳ in 1 screw, with the acceptable rate of 84.75%. There was significant difference in the acceptable rate of screw implantation between the two groups (χ2=3.875, P=0.037). The penetration rate of pedicle wall in trial group was 8.47% (5/59), which was significantly lower than that in the control group [32.20% (19/59); χ2=4.125, P=0.021].ConclusionCompared with the traditional technique, the pedicle screw implantation via vertebral arch-transverse pathway can obtain a good position of the screw canal with higher accuracy and simpler operation.
Objective To analyze the therapeutic effect of the posterior pedicle screw system combined with interbody fusion cage on lumbarspondylolisthesis. Methods From February 2003 to March 2006, 37 lumbar spondylolisthesis patients were treated with this operation, including21 males and 16 females and aging 3969 years.The affected lumbars were L3(3cases)，L4(23 cases), and L5(11 cases). According to the Meyerdingevaluating system, 12 cases were lassified as degree Ⅰ, 20 cases as degree Ⅱ,and 5 cases as degree Ⅲ. Taillard index, Boxall index, slipping angle, lumbar lordosis angle and intervertebral height index were measured before operation, and 2 weeks and 3 months after operation. Results All patients were followed up 336 months. There were statistically significant differences in Taillard index, Boxall index, slipping angle, lumbar lordosis angle and intervertebral height index between before operation and 2 weeks after operation (P＜0.05),and no statistically significant differences between 2 weeks and 3 months afteroperation(P＞0.05). According to Dewei Zhou’s creterior for scoring, the results were excellent in 27 cases， good in 8 cases，and fair in 2 cases. Theexcellent and good rate was 94.6%. All of the embedded osseous were fused. Thefusing time was from 3 to 8 months (mean 3-9 months). There were no breakageof screw and rod. The position and configuration of the whole cages were good. Conclusion Applying the posterior pedicle screw system combined with interbody fusion cage may achieve synergism in the treatment of lumbar vertebral spondylolisthesis. Above procedure is served as solid internal fixationand offers a satisfactory reduction, and can improve the fusion rate of the spine. So it is an ideal procedure and worthily recommended method for treatment oflumbar vertebral spondylolisthesis.
Objective To employ spinal virtual surgery system (SVSS) for preoperative planning of thoracolumbar pedicle screw fixation, and to establ ish the measurement method for pedicle screw-related parameters. Methods Eight thoracicand lumbar spine specimens (T11-L3) were selected. First of all, SVSS was used for the preoperative planning of pedicle screw and the parameters of both sides of pedicle were measured in every vertebral segment, including angle of axial view (Aa), angle of sagittal view (As), x-direction entrance (XE), total pedicle length of axial view (TLa), total pedicle length of sagittal view (TLs), pedicle height (PH), pedicle width (PW), and pedicle spongy width (PSW). Then the corresponding parameters of the right and left pedicle screws of the specimens were measured actually. Finally, its accuracy was verified by comparing the data by virtual measurement and actual measurement. Results There was no significant difference in the parameters of virtual measurement (Aa, As, TLa, TLs, XE, PW, PSW, and PH) and actual measurement (Aa, As, TLa, XE, PW, PSW, and PH) between the right and left sides (P gt; 0.05). Except XE of the L3 vertebral segment and PSW of T11 and T12 vertebral segments (P lt; 0.05), the differences in other parameters of other segments were not significant (P gt; 0.05). Conclusion After statistical analysis and comparison, the feasibil ity of preoperative planning of thoracolumbar pedicle screw fixation and the accuracy of the measurement of the SVSS is verified.
Objective To ascertain whether augmentation pedicle screw fixation with polymethylmethacrylate (PMMA) can enhance the stability of unstable thoracolumbar burst fractures of osteoporotic spine. Methods Six fresh frozen female osteoporotic spines (T10-L5) were harvested and an anterior and posterior columnunstable model of L1 was made. Each specimen was fixated with plate and the stability test were performed by flexion, extension, axial rotation and lateral bending. The test of fatigue was done with MTS 858.The tests were repeated after screws were augmented with PMMA. To compare the biomechanical stability of 6 different conditions:○anormal specimens(control), ○bdefectmodel fixed with plate, not augmented and not fatigued, ○cafter fatigued, not augmented, ○dscrews augmented with PMMA, not fatigued, ○e after augmented and fatigued. ResultsIn ○b,○d and ○e conditions, the ranges of motion(ROM) were 6.23±1.56，4.49±1.00，4.46±1.83 inflexion and 6.60±1.80，4.41±0.82，4.46±1.83 in extension. There was no significant difference (Pgt;0.05), they were significantly smaller than those in ○a and ○c conditions (8.75±1.88，1.47±2.25 and 8.92±2.97，12.24±3.08) (Plt;0.01).Conclusion The results demonstrated that augmentation pedicle screws fixation with PMMA can increase the stability of osteoporotic spine.
Objective
To compare the effectiveness of cortical bone trajectory screw (CBTS) and conventional pedicle screw for posterior lumbar interbody fusion (PLIF) in the treatment of single segment lumbar degenerative disease.
Methods
Between May 2013 and May 2016, a total of 97 patients with single segment lumbar degenerative disease were treated with PLIF. Fifty-one patients were fixed with CBTS in PLIF (trajectory screw group) and 46 with pedicle screw (pedicle screw group). There was no significant difference in age, gender, body mass index, preoperative diagnosis, lesion segment, and preoperative visual analogue scale (VAS) score, Oswestry dysfunction index (ODI) between 2 groups (P>0.05). The operation time, intraoperative blood loss, postoperative drainage, bed rest time, length of hospital stay, serum creatine kinase (CK) concentration, total amount of diclofenac sodium, perioperative complications, ODI, VAS score, and interbody fusion rate were recorded and compared between 2 groups.
Results
All patients were followed up 12 months. The patients in trajectory screw group had a significantly less operation time, intraoperative blood loss, postoperative drainage, and serum CK concentration when compared with the patients in pedicle screw group (P<0.05). Thirty-five patients (68.6%) in trajectory screw group and 46 patients (100%) in pedicle screw group were given diclofenac sodium within 48 hours after operation, showing significant difference between 2 groups (χ2=89.334, P=0.000). There was no significant difference in the incidence of perioperative complications between trajectory screw group and pedicle screw group (3.9% vs. 8.7%, P=0.418). There was no significant difference in the VAS score, ODI, and interbody fusion rate at 12 months after operation between 2 groups (P>0.05).
Conclusion
For the single segment degenerative lumbar disease, the use of CBTS or conventional pedicle screw for PLIF can obtain satisfactory clinical function and interbody fusion rate. But the former has the advantages of less blood loss, less intraoperative muscle damage, less perioperative pain, shorter length of hospital stay and bed rest time.
ObjectiveTo re-evaluate the systematic review and meta-analysis (SR/MAs) of the efficacy of robot-assisted pedicle screw placement. MethodsThe CNKI, VIP, WanFang Data, SinoMed, PubMed, Embase, Cochrane Library, and Web of Science databases were electronically searched to collect SR/MAs of robot-assisted pedicle screw placement from inception to April 28, 2023. Two reviewers independently screened literature, extracted data and then assessed the quality of reports, methodological quality, risk of bias, and the strength of evidence quality by using PRISMA, AMSTAR-Ⅱ, ROBIS, and GRADE tool. ResultsA total of 20 SR/MAs were included. The results of the included studies showed that robot-assisted pedicle screw placement was more accurate and had a lower number of complications compared with freehand pedicle screw placement. The quality of reports, methodology, and evidence for pedicle screw placement efficiency in all SR/MAs were low or extremely low, with a high risk of bias. The main reasons included high heterogeneity of included studies, unclear research methods and selection criteria, and missing key reporting processes. ConclusionRobot-assisted pedicle screw placement may have better clinical efficiency than traditional freehand pedicle screw placement. But the quality of relational SR/MAs is low.
Objective
To evaluate the fixation strength of expansive pedicle screw (EPS) at different bone mineral density (BMD) levels, further to provide theoretical evidence for the clinical application of the EPS in patients with osteoporosis.
Methods
Fresh human cadaver spines (T12-L5 spines) were divided into 4 levels: normal BMD, osteopenia, osteoporosis, and severe osteoporosis according to the value of BMD, 12 vertebra in each level. Conventional pedicle screw (CPS) or EPS was implanted into the bilateral vertebra in CPS group and EPS group, respectively, 12 screws in each group per BMD level. Screw pullout tests were conducted. The maximum pullout strength, stiffness, and energy absorption were determined by an AG-IS material testing machine with constant rate of loading in a speed of 5 mm/ min.
Results
With the decline of BMD from normal to severe osteoporosis level, the maximum pullout strength and the stiffness correspondingly declined (P lt; 0.05). In CPS group, the energy absorption gradually decreased (P lt; 0.05); in EPS group, significant difference was found between other different BMD levels (P lt; 0.05) except between normal BMD and osteopenia and between osteoporosis and severe osteoporosis (P gt; 0.05). At the same BMD level, the maximum pullout strength of EPS group was significantly larger than that of CPS group (P lt; 0.05); the stiffness of EPS group was significantly higher than that of CPS group (P lt; 0.05) except one at normal BMD level; and no significant difference was found in the energy absorption between 2 groups (P gt; 0.05) except one at osteopenia level. No significant difference was found in maximum pullout strength, stiffness, and energy absorption between EPS group at osteoporosis level and CPS group at osteopenia level (P gt; 0.05); however, the maximum pullout strength, stiffness, and energy absorption of EPS group at severe osteoporosis level were significantly lower than those of CPS group at osteopenia level (P lt; 0.05).
Conclusion
Compared with CPS, the EPS can significantly improve the fixation strength, especially in patients with osteopenia or osteoporosis.
