Fusion Fixation Research Articles

Biomechanical properties analysis of posterior lumbar interbody fusion with transpedicular oblique screw fixation

ObjectiveAn alternative to conventional posterior lumbar interbody fusion (PLIF) is a PLIF with transpedicular oblique screw fixation system. An assessment of new fixation system's viability and efficacy is conducted through a comparison of its biomechanical properties with those of conventional PLIF. MethodA comprehensive finite element model (FEM) of the lumbar regions L1-L5 was developed and the surgical segment L3-L4 was chosen to comprise the surgical models of both traditional PLIF and new PLIF. In new PLIF model, an analysis was conducted on segmental range of motion (RoM), cage stress, inferior endplates stress, vertebral stress, and internal fixation stress. Three-dimensional printers are utilized to fabricate and assemble the fusion cage and vertebrae, and compression test machines are employed to execute physiological load and extreme load experiments on new PLIF, so as to verify the accuracy of the FEM analysis and the mode of fatigue exhibited by new PLIF. ResultsIn new PLIF, the maximum stress on the inferior endplates under physiological loads was reduced in comparison to conventional PLIF. While the maximum stress on the cage, vertebral body, and screw increased, it remained within an acceptable range. The experimental data indicates that new fixation system can endure a vertical load exceeding 2800 N and an ultimate bending moment of 77 Nm. ConclusionThe new PLIF exhibits a comparable RoM to its predecessor, simultaneously mitigating inferior endplate stress and accommodating physiological loads, which reduce the amount of surgical incision and fusion fixation instruments. Consequently, it emerges as a sanguine surgical approach to fuse the degenerative lumbar spine.

Severe Rigid Scoliosis Deformity Correction Using Extended Posterior Release and Instrumentation: A Retrospective Study.

Sever rigid scoliotic deformity (magnitude of the curve >80° and <25% correction on bending film) correction is a great challenge to spine surgeons. Severe scoliosis when untreated or not treated properly, may lead to severe complications due to curve progression. The aim of operative management is to achieve significant correction of sagittal, coronal, and rotational deformity to avoid neurodeficit, maintain sagittal balance, and improve cardiopulmonary function. In this retrospective study, eight patients with severe rigid scoliosis who underwent through single-staged extended posterior release and spinal fusion between March 2022 and November 2023. The surgical procedures were the excision of the posterior ligament and spinous process, laminectomy, excision of ligament flavum, facetectomy, and posterior spinal fusion utilizing pedicle screws, rods, and sub-laminar wires. Patients were evaluated radiologically using posteroanterior and lateral X-rays of the whole spine and computed tomography scans. Demographic data, pre- and post-operative cobbs angle, osteotomized segment, instrumentation segments, blood loss, operation duration, follow-up duration, and complications were recorded. Pre-operative mean cobbs angle was 94.1° (range 83-110°) and post-operative mean cobbs angle was 33.3° (range 28-42°) with 64.6% scoliosis correction. The mean estimated blood loss was 517 mL (range 300-580 mL). The mean operation duration was 272.5 min (210-340 min). Mean spinal fixation fusion segments were 11.1 (range 8-14). No major complications were noted. Our study concluded that extended posterior-only release, facetectomy, and posterior spinal fusion by utilizing pedicle screws and pre-contoured rods significantly corrected severe and rigid scoliosis with a high correction rate and avoid complications of anterior release. Hence, we can achieve remarkable correction in rigid scoliosis using the proper choice of levels, proper implant, and extended posterior release.

Biomechanical Comparison Using 3-D Finite Element Method between Cortical Screw Trajectory Fixation and Pedicle Screw Fixation for Fusion of the Lumbar Degenerative Spine

Biomechanical Comparison Using 3-D Finite Element Method between Cortical Screw Trajectory Fixation and Pedicle Screw Fixation for Fusion of the Lumbar Degenerative Spine

Selection of treatment strategies for lumbar Brucella spondylitis: a retrospective clinical study.

This study aims to investigate the treatment strategies for lumbar brucellar spondylitis by comparing the outcomes of pure pharmacological treatment with diseased intervertebral fixation fusion, with or without lesion clearance. A total of 157 patients with lumbar brucellar spondylitis were categorized into three groups: Group A (52 cases) received pure pharmacological treatment, Group B (53 cases) underwent posterior vertebral fixation fusion, and Group C (52 cases) received posterior (or anterior) lesion clearance followed by posterior vertebral fixation fusion. Clinical data were analyzed, and the efficacy of the three treatment methods was evaluated. The surgical groups showed better outcomes at various time points compared to the pharmacological treatment group (P < 0.05). The pure fixation group outperformed the lesion clearance fusion group during the perioperative period (P < 0.05). The ESR, CRP, ODI scores, imaging evaluation and complications of the lesion clearance followed by fixation group were all better than those of the other two groups (P < 0.05). Surgical treatment groups showed no statistically significant difference in VAS scores (P > 0.05), and both were superior to the pharmacological treatment group. There were no statistically significant differences in clinical efficacy among the three groups at the last follow-up. Surgical treatment achieves early recovery goals compared to pharmacological treatment for brucellar spondylitis. However, individualized treatment principles should guide surgical decisions to select the most suitable approach for patients.

Comparison of Fusion Rates/Complications Between Different Types of Thumb Metacarpophalangeal Fusion Techniques.

Thumb metacarpophalangeal (MP) fusion is generally successful; however, complications have been reported to occur in 0% to 30% of cases, whereas nonunion rates vary by method but, overall, are reported to occur in 0% to 15% of cases. Many fixation techniques have been described, but there is no consensus on the optimal fusion technique. Our goal was to compare complication and union rates of different thumb MP arthrodesis techniques. We performed a retrospective review of patients who underwent primary thumb MP fusion between 2000 and 2022. Patients who underwent revision fusion, fusion for infection, or amputation were excluded. Fusions of MP joints of other fingers were also excluded. Data collection consisted of demographic data, complications, time to fusion, rate of delayed union and rate of nonunion. Five different fusion constructs were evaluated during our study period: staples, Kirschner wires (K-wires), cerclage, K-wires with cerclage, and intramedullary screw. Forty-seven patients underwent fusion with staples, 16 with K-wires, 14 with cerclage, 9 with K-wires and cerclage, and 6 with an intramedullary screw. The individual complication and nonunion rates differed significantly among the groups with the intramedullary screw group having a statistically higher rate of nonunion (P = .004). Furthermore, smoking, diabetes, and being overweight were associated with nonunions. Union rates were significantly lower in patients treated with an intramedullary screw and those who are smokers, diabetics, and/or overweight. Caution should be exercised when using intramedullary screw fixation for MP fusion, especially in patients with these comorbidities.

Safety and Efficacy Analysis of Anterior and Posterior Lesion Removal and Fusion Fixation in Spinal Infectious Disease

Safety and Efficacy Analysis of Anterior and Posterior Lesion Removal and Fusion Fixation in Spinal Infectious Disease

Fusion Length Requiring Spinopelvic Fixation in Lumbosacral Fusion with Anterior Column Support at L5-S1: Assessment of Fusion Status Using Computed Tomography.

The lumbosacral (LS) junction has a higher nonunion rate than other lumbar segments, especially in long-level fusion. Nonunion at L5-S1 would result in low back pain, spinal imbalance, and poor surgical outcomes. Although anterior column support at L5-S1 has been recommended to prevent nonunion in long-level LS fusion, fusion length requiring additional spinopelvic fixation (SPF) in LS fusion with anterior column support at L5-S1 has not been evaluated thoroughly. This study aimed to determine the number of fused levels requiring SPF in LS fusion with anterior column support at L5-S1 by assessing the interbody fusion status using computed tomography (CT) depending on the fusion length. Patients who underwent instrumented LS fusion with L5-S1 interbody fusion without additional augmentation and CT > 1 year postoperatively were included. The fusion rates were assessed based on the number of fused segments. Patients were divided into two groups depending on the L5-S1 interbody fusion status: those with union vs. those with nonunion. Binary logistic regression analyses were performed to identify risk factors for LS junctional nonunion. Fusion rates of L5-S1 interbody fusion were 94.9%, 90.3%, 80.0%, 50.0%, 52.6%, and 43.5% for fusion of 1, 2, 3, 4, 5, and ≥ 6 levels, respectively. The number of spinal levels fused ≥ 4 (p < 0.001), low preoperative bone mineral density (BMD; adjusted odds ratio [aOR], 0.667; p = 0.035), and postoperative pelvic incidence (PI) - lumbar lordosis (LL) mismatch (aOR, 1.034; p = 0.040) were identified as significant risk factors for nonunion of L5-S1 interbody fusion according to the multivariate logistic regression analysis. Exhibiting ≥ 4 fused spinal levels, low preoperative BMD, and large postoperative PI-LL mismatch were identified as independent risk factors for nonunion of anterior column support at L5-S1 in LS fusion without additional fixation. Therefore, SPF should be considered in LS fusion extending to or above L2 to prevent LS junctional nonunion.

Screw Insertional Torque Measurement in Spine Surgery: Correlation With Bone Mineral Density and Hounsfield Unit.

Achieving successful fusion during spine surgery is dependent on rigid pedicle screw fixation. To assess fixation strength, the insertional torque can be measured during intraoperative screw fixation. This study aimed to explore the technical feasibility of measuring the insertional torque of a pedicle screw, while investigating its relationship with bone density. Thoraco-lumbar screw fixation fusion surgery was performed on 53 patients (mean age, 65.5 ± 9.8 years). The insertional torque of 284 screws was measured at the point passing through the pedicle using a calibrated torque wrench, with a specially designed connector to the spine screw system. The Hounsfield units (HU) value was determined by assessing the trabecular portion of the index vertebral body on sagittal computed tomography images. We analyzed the relationship between the measured insertional torque and the following bone strength parameters: bone mineral density (BMD) and HU of the vertebral body. The mean insertion torque was 105.55 ± 58.08 N∙cm and T-score value (BMD) was -1.14 ± 1.49. Mean HU value was 136.37 ± 57.59. Screw insertion torque was positively correlated with BMD and HU in whole patients. However, in cases of osteopenia, all variables showed very weak correlations with insertional torque. In patients with osteoporosis, there was no statistically significant correlation between BMD and torque strength; HU showed a significant correlation. The insertional torque of screw fixation significantly correlated with bone density (BMD and HU). HU measurements showed greater clinical significance than did BMD values in patients with osteoporosis.

The clinical efficacy of laminectomy fusion fixation and posterior single open-door laminoplasty in the treatment of multilevel cervical ossification of the posterior longitudinal ligament (OPLL): a retrospective study

BackgroundTo compared the clinical efficacy of two surgical methods, posterior laminectomy fusion fixation, and posterior single open-door laminoplasty, in treating multilevel cervical ossification of the posterior longitudinal ligament (OPLL).MethodsThe study retrospectively included 102 patients treated between December 2016 and December 2020. The patients were included into an observation group (56 cases) treated with total laminectomy and lateral screw fixation, and a control group (46 cases) treated with single open-door laminoplasty.ResultsAfter 24 months, both groups showed significant improvement in Japanese Orthopaedic Association (JOA) scores and Visual Analogue Scale (VAS) scores, indicating better clinical symptoms and functional recovery. There was no significant difference in preoperative JOA and VAS scores between the two groups (P > 0.05). At 24 months after surgery, there was no significant difference in JOA and VAS scores between the two groups (P > 0.05). However, the observation group had a significantly higher cervical curvature index (CCI) and lower range of motion (ROM) of the cervical spine compared to the control group (P < 0.05). The CCI in control group was lower than before surgery, while the CCI in observation group was higher than before surgery, and CCI in the control group was considerably lower than that in the observation group (P < 0.05). The complication rate was lower in the control group, with fewer cases of axial symptoms, fifth cervical nerve root palsy, and overall complications. The overall complication rate was 25.0% (14/56) in the observation group and 10.8% (5/46) in the control group (P < 0.05).ConclusionsBoth posterior laminectomy fusion fixation and posterior single open-door laminoplasty yield positive outcomes in improving clinical neurological function, cervical curvature, range of motion of the cervical spine, and cervical sagittal balance. Although open-door laminoplasty is less effective than total laminectomy in maintaining CCI and sagittal balance, it excels in preserving cervical range of motion, less surgical trauma and complications. Thus, open-door laminoplasty may be a suitable first-choice treatment for multi-segmental cervical OPLL, especially for patients with lordotic cervical spine physiological curvature.

Simultaneous Single-Position Lateral Lumbar Interbody Fusion Surgery and Unilateral Percutaneous Pedicle Screw Fixation for Spondylolisthesis.

To evaluate the clinical and radiological efficacy of a combine of lateral single screw-rod and unilateral percutaneous pedicle screw fixation (LSUP) for lateral lumbar interbody fusion (LLIF) in the treatment of spondylolisthesis. Sixty-two consecutive patients with lumbar spondylolisthesis who underwent minimally invasive (MIS)-TLIF with bilateral pedicle screw (BPS) or LLIF-LSUP were retrospectively studied. Segmental lordosis angle (SLA), lumbar lordosis angle (LLA), disc height (DH), slipping percentage, the cross-sectional areas (CSA) of the thecal sac, screw placement accuracy, fusion rate and foraminal height (FH) were used to evaluate radiographic changes postoperatively. Visual analogue scale (VAS) and Oswestry Disability Index (ODI) were used to evaluate the clinical efficacy. Patients who underwent LLIF-LSUP showed shorter operating time, less length of hospital stay and lower blood loss than MIS-TLIF. No statistical difference was found between the 2 groups in screw placement accuracy, overall complications, VAS, and ODI. Compared with MIS-TLIF-BPS, LLIF-LSUP had a significant improvement in sagittal parameters including DH, FH, LLA, and SLA. The CSA of MIS-TLIF-BPS was significantly increased than that of LLIF-LSUP. The fusion rate of LLIF-LSUP was significantly higher than that of MIS-TLIF-BPS at the follow-up of 3 months postoperatively, but there was no statistical difference between the 2 groups at the follow-up of 6 months, 9 months, and 12 months. The overall clinical outcomes and complications of LLIF-LSUP were comparable to that of MIS-TLIF-BPS in this series. Compared with MIS-TLIF-BPS, LLIF-LSUP for lumbar spondylolisthesis represents a significantly shorter operating time, hospital stay and lower blood loss, and demonstrates better radiological outcomes to maintain lumbar lordosis, and reveal an overwhelming superiority in the early fusion rate.

Establishment of an animal model of adjacent segment degeneration after interbody fusion and related experimental studies

BackgroundDegenerative spine conditions are common and frequent clinical diseases, and adjacent segment disease (ASD) after spinal fusion (SF) is a common complication after spinal fusion (SF). In this study, we established an animal model of ASD after interbody fusion to observe the morphologic changes of adjacent segment (AS) disks and to determine the expression and significance of tumor necrosis factor-alpha (TNF-α) and interleukin-1beta (IL-1β) in ASD tissues to provide a good experimental basis and reference for clinical prevention and treatment of ASD after interbody fusion.MethodsThirty-six male and female New Zealand rabbits weighing 2.0–2.5 kg were randomly divided into control group (group A) and experimental groups (groups B, C, and D), with 9 rabbits in each group, of which groups B, C, and D were the 4-, 8-, and 12-week groups, respectively. Autologous iliac bone grafts were used as the bone graft material. In the experimental groups, a SF was performed on the C2–C3 intervertebral space. The C3–4 adjacent segments were examined. In the experimental group, the animals were subjected to gross observation, X-ray examination, hand touch inspection, and micro-computed tomography (micro-CT) 4, 8, and 12 weeks after surgery. The micromorphologic changes of the cervical disks in the segments of the control group and experimental groups were observed under light microscopy. Immunohistochemistry and Western blotting were used to detect the expression of TNF-α and IL-1β in the AS tissues after interbody fusion in the control and experimental groups.ResultsThe measurement data of the rabbit cervical spine bony structures indicated that the length of the vertebral body and the sagittal diameter of the lower end of the vertebral body decreased gradually from the 2nd–6th cervical vertebrae, and the difference was statistically significant (P < 0.05). The difference in the transverse diameter of the lower end of the vertebral body was not statistically significant (P > 0.05), the change in the oblique diameter of the lower end of the vertebral body fluctuated, and the difference was statistically significant (P < 0.05). The fusion rate of the cervical spine by hand touch inspection was 22.2% (2/9), 55.6% (5/9), and 88.9% (8/9) in groups B, C, and D, respectively. The differences in bone volume-to-total volume (BV/TV) and X-ray scores were statistically significant in groups B, C, and D (P < 0.05). Significant degeneration occurred in groups B, C, and D compared with group A. The expression of TNF-α and IL-1β in the intervertebral disk tissue was significantly higher in groups B, C, and D compared with group A (P < 0.05), and increased with time.ConclusionIn this study, an animal model of ASD after interbody fusion fixation in rabbits was successfully established. Postoperative imaging and hand touch inspection showed a positive correlation between the amount of new intervertebral bone and the degree of fusion with time. The results of immunohistochemistry and Western blot showed that TNF-α and IL-1β were highly expressed in the AS tissues of the experimental group after interbody fusion, and the degree of disk degeneration was positively correlated with the time after interbody fusion.

Development of a novel PLDLA/β-TCP composite-based biodegradable anterior cervical plate and screw system.

We investigated the effectiveness and safety of a new composite-based biodegradable anterior cervical plate/screw (ACPS) system for the anterior cervical discectomy and fusion (ACDF) fixation. A biocomposite in combination with 30 wt% β-tricalcium phosphate (β-TCP; a biodegradable ceramic having osteoconductive ability) and 70 wt% poly-l/d-lactide copolymer (PLDLA; a biodegradable polymer) was developed and used in the ACPS device, comprising one plate and four screws for fixation. Based on a literature review, a clinically required period of performance maintenance was set as 16 weeks, and to verify the performance for a period of 16 weeks or more, the test was conducted for 26 weeks. Following ISO 13781:2017 testing protocols, an in vitro degradation test was performed to verify the performance and evaluate the decomposition characteristics of the biodegradable ACPS system. Using an animal model as a preclinical investigation, the prepared ACPS device was implanted into five mongrel dogs weighing over 30 kg to evaluate the detachment prevention effect of the ACPS system on polyether ether ketone (PEEK) cage after ACDF. By week 26, the molecular weight was decreased by 45.35% for the plate and 52.56% for the screw; the bending strength of the plate was decreased by approximately 26.2% when compared with the initial stage. The torsional yield strength and pullout strength of the screw was increased by 52.31% and 5.3%, respectively by week 2 and then subsequently decreased until week 26. No detachment or dislocation of the inserted PEEK cage was observed for 26 weeks in vivo study. These findings recommend that the ACPS system might be a promising biodegradable tool for the fixation of interbody implants and supporting the fusion in an ACDF model. Furthermore, additional clinical trials are planned for the future.

A Review of Spinal Twine Injury and Its Management

There is no universal agreement on the best procedure for treating lower cervical dislocation because anterior reduction and interbody fusion fixation have not been directly compared to posterior reduction and short-segmental pedicle screw fixation. This study compares the long-term effects of severe cervical dislocation with spinal cord injury treated using an anterior versus a posterior method. A total of 149 patients (follow-up rate of 84.1%) could be followed for more than 10 years. 67 patients had posterior reduction and short-segmental pedicle screw fixation, while 92 patients underwent anterior reduction and interbody fusion and fixation. Surgical or post-operative problems as well as the Japanese Orthopaedic Association (JOA) scores, the Neck Disability Index (NDI), the American Spinal Injury Association grading (ASIA), Odom's criteria, cervical kyphosis, and operating parameters were assessed. 10 to 17 years were spent monitoring the patients. At the follow-up, there was no discernible difference between the two groups' primary JOA scores, NDI scores, or ASIA scores. The posterior method was linked to a larger loss of alignment at the last follow-up and by two years (P = 0.012 and P 0.001, respectively).

101. Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) vs anterior lumbar interbody fusion with pedicle screw fixation in single-level circumferential fusion

101. Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) vs anterior lumbar interbody fusion with pedicle screw fixation in single-level circumferential fusion

P111. Sublaminar fixation in thoracic AIS posterior fusion with >5-year followup, radiographic and clinical outcomes comparison of hooks, wires and bands

P111. Sublaminar fixation in thoracic AIS posterior fusion with >5-year followup, radiographic and clinical outcomes comparison of hooks, wires and bands

Biomechanical analysis of a single-level customized cage screw fixation for anterior cervical discectomy and fusion in the cervical spine: an in-silico study

The usual surgical choice of customized cage fixation is anterior cervical discectomy and fusion (ACDF) for cervical spondylosis with disc herniation. The safe and successful cage fixation for ACDF surgery benefits patients with cervical disc degenerative disease by easing their discomfort and regaining function. The cage prevents mobility between the vertebrae by using cage fixation to anchor the neighbouring vertebrae. The goal of the current study is to develop a customized cage-screw implant for single-level cage fixation at C4–C5 level of the cervical spine (C2–C7). The Finite Element Analysis (FEA) is performed for the intact and implanted cervical spine and analysed the flexibility, stress of the implant and implant adjacent bone during three physiological loading conditions being analysed. Lower surface of the C7 vertebrae is fixed and 50 N compressive force with 1 Nm moment are applied on the C2 vertebrae for simulated lateral bending, axial rotation and flexion-extension. The flexibility is decreased at single level of fixation (C4–C5 level) by 64% to 86%, as compared to natural cervical spine. The flexibility is increased 3% to 17% at the nearest levels of fixation. The maximum Von Mises stress in PEEK cage varies from 24 to 59 MPa and for Ti-6Al-4V screw the stress varies from 84 MPa to 121 MPa which are far below the yield stress of PEEK (95 MPa) and Ti-6Al-4V (750 MPa).

Effect of adjacent segmental facet joint degeneration on adjacent segment disease after lumbar fusion and fixation

To explore the effect of facet joint degeneration in adjacent segments on the incidence of adjacent segment disease (ASD) after lumbar fusion and fixation. A retrospective analysis was performed on 138 patients who underwent L5S1 posterior lumbar interbody fusion (PLIF) from June 2016 to June 2019. Patients were divided into a degeneration group (68 cases) and a non-degenerative group (70 cases) based on the presence or absence of L4,5 facet joint degeneration before surgery (graded using the Weishaupt standard). Age, gender, body mass index (BMI), follow-up time, and preoperative L4,5 intervertebral disc degeneration (graded using the Pfirrmann standard) were collected for both groups. Clinical outcomes were evaluated using the visual analogue scale (VAS) and Oswestry disability index (ODI) at 1 and 3 months after surgery. The incidence and time of ASD after surgery were analyzed. There were no significant differences between the two groups in age, gender, BMI, follow-up time, or preoperative L4,5 intervertebral disc degeneration. Both groups showed significant improvement in VAS and ODI at 1 and 3 months after surgery (P<0.001), with no significant difference between the groups(P>0.05). However, there was a statistically significant difference in the incidence and timing of ASD between the groups (P<0.05). The degeneration group had 2 cases of ASD in gradeⅠdegeneration, 4 cases of ASD in gradeⅡdegeneration, and 7 cases of ASD in grade Ⅲ degeneration. There was a statistically significant difference between the number of patients with grade Ⅲ degeneration and those with gradesⅠandⅡASD (P<0.0167, Bonferroni correction). Preoperative degeneration of adjacent articular processes will increase the risk of ASD after lumbar fusion fixation, whereas gradeⅢ degeneration will further increase the risk.

Biomechanical effect of endplate defects on the intermediate vertebral bone in consecutive two-level anterior cervical discectomy and fusion: a finite element analysis

BackgroundIntermediate vertebral collapse is a newly discovered complication of consecutive two-level anterior cervical discectomy and fusion (ACDF). There have been no analytical studies related to the effects of endplate defects on the biomechanics of the intermediate vertebral bone after ACDF. This study aimed to compare the effects of endplate defects on the intermediate vertebral bone biomechanics in the zero-profile (ZP) and cage-and-plate (CP) methods of consecutive 2-level ACDF and to determine whether collapse of the intermediate vertebra is more likely to occur using ZP.MethodsA three-dimensional finite element (FE) model of the intact cervical spine (C2–T1) was constructed and validated. The intact FE model was then modified to build ACDF models and imitate the situation of endplate injury, establishing two groups of models (ZP, IM-ZP and CP, IM-ZP). We simulated cervical motion, such as flexion, extension, lateral bending and axial rotation, and compared the range of motion (ROM), upper and lower endplate stress, fusion fixation device stress, C5 vertebral body stress, intervertebral disc internal pressure (intradiscal pressure, or IDP) and the ROM of adjacent segments in the models.ResultsThere was no significant difference between the IM-CP model and the CP model in the ROM of the surgical segment, upper and lower endplate stress, fusion fixation device stress, C5 vertebral body stress, IDP, or ROM of the adjacent segments. Compared with the CP model, the endplate stress of the ZP model is significantly higher in the flexion, extension, lateral bending and axial rotation conditions. Compared with the ZP model, endplate stress, screw stress, C5 vertebral stress and IDP in IM-ZP were significantly increased under flexion, extension, lateral bending and axial rotation conditions.ConclusionsCompared to consecutive 2-level ACDF using CP, collapse of the intermediate vertebra is more likely to occur using ZP due to its mechanical characteristics. Intraoperative endplate defects of the anterior lower margin of the middle vertebra are a risk factor leading to collapse of the middle vertebra after consecutive 2-level ACDF using ZP.

Application of back-forward Bending CT localization image in the prediction of proximal junctional kyphosis after spinal deformity surgery in adults

To investigate the feasibility of predicting proximal junctional kyphosis (PJK) in adults after spinal deformity surgery based on back-forward Bending CT localization images and related predictive indicators. A retrospective analysis was performed for 31 adult patients with spinal deformity who underwent posterior osteotomy and long-segment fusion fixation between March 2017 and March 2020. There were 5 males and 26 females with an average age of 62.5 years (range, 30-77 years). The upper instrumented vertebrae (UIV) located at T 5 in 1 case, T 6 in 1 case, T 9 in 13 cases, T 10 in 12 cases, and T 11 in 4 cases. The lowest instrumented vertebrae (LIV) located at L 1 in 3 cases, L 2 in 3 cases, L 3 in 10 cases, L 4 in 7 cases, L 5 in 5 cases, and S 1 in 3 cases. Based on the full-length lateral X-ray film of the spine in the standing position before and after operation and back-forward Bending CT localization images before operation, the sagittal sequence of the spine was obtained, and the relevant indexes were measured, including thoracic kyphosis (TK), lumbar lordosis (LL), local kyphosis Cobb angle (LKCA) [the difference between the different positions before operation (recovery value) was calculated], kyphosis flexibility, hyperextension sagittal vertical axis (hSVA), T 2-L 5 hyperextension C 7-vertebral sagittal offset (hC 7-VSO), and pre- and post-operative proximal junctional angle (PJA). At last follow-up, the patients were divided into PJK and non-PJK groups based on PJA to determine whether they had PJK. The gender, age, body mass index (BMI), number of fusion segments, number of cases with coronal plane deformity, bone mineral density (T value), UIV position, LIV position, operation time, intraoperative blood loss, osteotomy grading, and related imaging indicators were compared between the two groups. The hC 7-VSO of the vertebral body with significant differences between groups was taken, and the receiver operating characteristic curve (ROC) was used to evaluate its accuracy in predicting the occurrence of PJK. All 31 patients were followed up 13-52 months, with an average of 30.0 months. The patient's PJA was 1.4°-29.0° at last follow-up, with an average of 10.4°; PJK occurred in 8 cases (25.8%). There was no significant difference in gender, age, BMI, number of fusion segments, number of cases with coronal plane deformity, bone mineral density (T value), UIV position, LIV position, operation time, intraoperative blood loss, and osteotomy grading between the two groups ( P>0.05). Imaging measurements showed that the LL recovery value and T 8-L 3 vertebral hC 7-VSO in the PJK group were significantly higher than those in the non-PJK group ( P>0.05). There was no significant difference in hyperextension TK, hyperextension LL, hyperextension LKCA, TK recovery value, LL recovery value, kyphosis flexibility, hSVA, and T 2-T 7, L 4, L 5 vertebral hC 7-VSO ( P>0.05). T 8-L 3 vertebral hC 7-VSO was analyzed for ROC curve, and combined with the area under curve and the comprehensive evaluation of sensitivity and specificity, the best predictive index was hC 7-L 2, the cut-off value was 2.54 cm, the sensitivity was 100%, and the specificity was 60.9%. Preoperative back-forward Bending CT localization image can be used to predict the occurrence of PJK after posterior osteotomy and long-segment fusion fixation in adult spinal deformity. If the patient's T 8-L 2 vertebral hC 7-VSO is too large, it indicates a higher risk of postoperative PJK. The best predictive index is hC 7-L 2, and the cut-off value is 2.54 cm.

Unilateral Pedicle Screw Fixation versus Bilateral Pedicle Screw Fixation for Single-Level Lumbar Degenerative Spine: A Systematic Review of Meta-analyses

AIM: The objectives of this study were to perform a systematic literature review based on studies that compare unilateral and bilateral pedicle screw fixation (PSF) in lumbosacral spine fusion to provide recommendations for the treatment of degenerative diseases of the spine, to identify studies with a more complete evidence base, and to identify possible limitations in available literature sources that require further research. METHODS: A literature search was conducted in PubMed, Embase, and the Cochrane Library to identify studies that compare unilateral versus bilateral PSF versus interbody implant placement used the treatment of degenerative diseases of the lumbosacral spine. The study included meta-analyses that met the inclusion criteria. The quality of meta-analyses was evaluated with a measurement tool to assess systematic reviews (AMSTAR) score and the most relevant meta-analysis was determined by applying the Jadad algorithm. RESULTS: Twelve studies fulfilled the eligibility criteria and were included in the study. The results of AMSTAR score ranged from 6 to 9, based on the results, four meta-analysis can be assigned to “middle” category and remained 8 to “upper” category. According to the results obtained, there was no significant difference between unilateral and bilateral PSF; however, unilateral fixation had advantages in the duration of surgical treatment and intraoperative blood loss. СONCLUSION: According to this systematic review, unilateral PSF is an effective fixation method in the formation of lumbosacral spine fusion and has advantages in reducing the duration of surgical treatment and intraoperative blood loss compared to bilateral PSF.