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Six-screw short-segment posterior fixation for thoracolumbar fractures, which involves intermediate screws at the fractured vertebrae has been proposed to reduce the rates of kyphosis recurrence and implant failure. Yet, little is known about the mechanisms and biomechanical responses by which intermediate screws at the fracture vertebrae enhance fixation strength. The objective of this study was to investigate the biomechanical properties that are associated with the augmentation of intermediate screws in relation to the severity of type A thoracolumbar fracture using finite element analysis. Short-segment stabilization models with or without augmentation screws at fractured vertebrae were established based on finite element model of moderate compressive fractures, severe compressive fractures and burst fractures. The spinal stiffness, stresses at the implanted hardware, and axial displacement of the bony defect were measured and compared under mechanical loading conditions. All six-screw stabilization showed a decreased range of motion in extension, lateral bending, and axial rotation compared to the traditional four-screw fixation models. Burst thoracolumbar fracture benefited more from augmentation of intermediate screws at the fracture vertebrae. The stress of the rod in six-screw models increased while decreased that of pedicle screws. Our results suggested that patients with more unstable fractures might achieve greater benefits from augmentation of intermediate screws at the fracture vertebrae. Augmentation of intermediate screws at the fracture vertebrae is recommended for patients with higher wedge-shaped or burst fractures to reduce the risk of hardware failure and postoperative re-collapse of injured vertebrae.

Background: "Convex Pedicle Screw Technique" reduces the theoretical risk of neurovascular injury. Our aim is to evaluate the efficacy of this technique in patients with neuromuscular scoliosis (NMS)., Methods: Retrospective study of 12 patients who underwent a Convex Pedicle Screw Technique and were diagnosed with NMS. Patients who had undergone previous spinal surgery were excluded. The minimum follow-up required was 24 months. Demographic data, intraoperative data, neurovascular complications and neurophysiological events requiring implant repositioning, as well as pre- and postoperative radiological variables were collected., Results: Twelve patients diagnosed with NMS underwent surgery. The median operative time was 217 minutes. Mean blood loss was 3.8±1.1 g/dL hemoglobin (Hb). The median postoperative stay was 8.8±4 days. A reduction of the Cobb angle in primary curve of 49.1% (from 52.8°±18° to 26.5°±12.6°; P<0.001) and in secondary curve of 25.2% (from 27.8°±18.9° to 18.3°±13.3°; P=0.10) was achieved. Coronal balance improved by 69.4% (7.5±46.2 vs. 2.3±20.9 mm; P=0.72) and sagittal balance by 75% (from -14.1±71.8 vs. -3.5±48.6 mm; P=0.50). There were no neurovascular complications. There were no intraoperative neurophysiological events requiring implant repositioning, nor during reduction maneuvers. No infections were reported., Conclusions: The correction of the deformity from convexity in NMS achieves similar results to other techniques, and a very low complication rate., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jss.amegroups.com/article/view/10.21037/jss-23-128/coif). The authors have no conflicts of interest to declare., (2024 Journal of Spine Surgery. All rights reserved.)

Introduction: Pedicle screw instrumentation (PSI) serves as the widely accepted surgical treatment for adolescent idiopathic scoliosis (AIS). The accuracy of screw positioning has remarkably improved with robotic assistance. Nonetheless, its impact on radiographic and clinical outcomes remains unexplored. This study aimed to investigate the radiographic and clinical outcomes of robot-assisted PSI vs. conventional freehand method in AIS patients., Methods: Data of AIS patients who underwent PSI with all pedicle screws between April 2013 and March 2022 were included and retrospectively analyzed; those with hybrid implants were excluded. Recruited individuals were divided into the Robot-assisted or Freehand group according to the technique used. Radiographic parameters and clinical outcome measures were documented., Results: In total, 50 patients (19, Freehand group; 31, Robot-assisted group) were eligible, with an average age and follow-up period of 17.6 years and 60.2 months, respectively, and female predominance (40/50, 80.0%). The correction rates of Cobb's angles for both groups were significant postoperatively. Compared to freehand, the robot-assisted technique achieved a significantly reduced breech rate and provided better trunk shift and radiographic shoulder height correction with preserved lumbar lordosis, resulting in significantly improved visual analog scale scores for back pain from the third postoperative month., Conclusion: Overall, robot-assisted PSI provides satisfactory radiographic and clinical outcomes in AIS patients., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Chen, Lin, Wu, Shih, Chen, Lee, Lu and Pan.)

Objective: Lumbar fractures are the most common spinal injuries, and surgery is required for severe fracture. This study aimed to investigate the variations in motion and stress in varying states of activity after minimally invasive and traditional open pedicle screw placement for L1 vertebral fracture stabilization., Methods: We studied a male volunteer (26 years old) with no history of chronic back pain or lumbar spine trauma. We used the finite element method for this investigation. Using finite element software, we created a three-dimensional model of L1 vertebral compression fracture. We also constructed models for four percutaneous pedicle screws spanning the fractured vertebra and four screws traversing the damaged vertebra with transverse fixation., Results: In all three-dimensional movement directions, the open pedicle fixation system experienced maximum stress higher than its percutaneous counterpart. With axial spinal rotation, von Mises stress on the traditional open pedicle screw was considerably lower than that with percutaneous pedicle fixation, but peak stress was elevated at the transverse connection. Traditional open pedicle fixation displayed less maximum displacement than percutaneous pedicle internal fixation., Conclusions: During axial spinal movements, high peak stress is observed at the transverse connection. Patients should avoid excessive axial rotation of the spine during recovery., Competing Interests: Declaration of conflicting interestThe authors declare that there is no conflict of interest.

Objective: Operative treatment of adolescent idiopathic scoliosis (AIS) with posterior spinal fusion aims for three-dimensional correction of coronal curve and thoracic kyphosis. Our aim was to compare two different designs of asymmetrical rods in adolescents who underwent a posterior spinal fusion with pedicle screw instrumentation for AIS with an emphasis on thoracic kyphosis restoration., Methods: This study was made with 76 consecutive adolescents (mean age 15.6 years, SD 2.0). Thirty-nine patients were operated with sagittal reinforced rods and 37 patients were operated with beam-like rods. The clinical and radiological results were assessed preoperatively, postoperatively, and during the follow-up visits at the outpatient clinic 6 months and 2 years after the surgery., Results: At the last follow-up, the mean (SD) major thoracic curves were 13° (6.2°) and 13° (6.0°) (P = 0.717). Correction percentages were 75% in the sagittal reinforced group and 73% in the beam-like rod group (P = 0.517). The mean (SD) thoracic kyphosis was 24° (11°) and 22° (7.8°) at the two year follow-up in the sagittal reinforced rod group and beamlike rod group (P = 0.517). There was a slight negative correlation between the major curve correction and thoracic kyphosis change in both groups, although this was not statistically significant (R = -0.19, P = 0.094 in the sagittal reinforced rod group, R=-0.16, P = 0.180 in the beam like rod group)., Conclusions: There are no significant differences in the coronal or sagittal deformity restoration in adolescent patients who underwent a posterior spinal fusion with sagittal reinforced rods and beam-like rods for adolescent idiopathic scoliosis., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Posterior spinal correction and fusion remains the most common surgical treatment in AIS. Surgeons currently favour all pedicle screw (AS) correction techniques with alternative implants being less utilised. The purpose of this study was to assess whether a hybrid hook−screw (HS) construct could achieve similar outcomes. Methods: A single centre, prospective cohort study was conducted. Patients with moderate and severe thoracic AIS (Lenke 1) were included. Clinical and radiological results of a standardised hybrid HS technique were compared with those obtained with an AS construct. All patients had a minimum 2-year follow-up. Results: 160 patients were included in this series (80 patients/group). The HS group had significantly reduced surgical time, blood loss and implant density. Both techniques achieved ≥75% scoliosis correction. The HS group was superior in restoring thoracic kyphosis and global sagittal balance with an average 31% increase in kyphosis compared to 10% with the AS group (p < 0.001). There was significant improvement in SRS-22 scores at 2 years postoperative (p < 0.001) in both groups. There were no neurological or visceral complications related to instrumentation, no detected non-union and no reoperations. The HS implant cost was significantly lower than that of AS, with a mean instrumentation saving of almost £2000/patient. Conclusion: A standardised hybrid HS technique achieved excellent correction of thoracic scoliosis, high patient satisfaction and low complication rates in patients with thoracic AIS. These results were comparable to the AS group. The HS technique achieved better correction of thoracic kyphosis and sagittal balance than the AS technique, together with reduced surgical time, blood loss and implant cost.

Background: Pedicle screw instrumentation of the cervical spine, although technically challenging due to the potential risk of serious neurovascular injuries, is biomechanically favorable for stabilization purposes. Patient-specific templates are increasingly used in the thoracolumbar spine with excellent accuracy. The aim of this study was to evaluate the accuracy of cervical pedicle screw placement with patient-specific templates in a clinical setting and to report the European experience so far., Methods: Multicentric, retrospectively obtained data of twelve patients who underwent dorsal instrumentation of the cervical spine with 3D-printed patient-specific templates were analyzed. Postoperative computed tomography (CT) scans were used to evaluate pedicle perforation and screw deviations between the planned and actual screw position. Furthermore, surgical time, radiation exposure, blood loss and immediate postoperative complications were analyzed., Results: A total of 86 screws were inserted, of which 82 (95.3%) were fully contained inside the pedicle. All perforations (four screws, 4.7%) were within the safe zone of 2 mm and did not result in any neurovascular complications. Overall, median deviation from planned entry point (Euclidean distance) was 1.2 mm (0.1 - 11 mm), median deviation from the planned trajectory (Euler angle) was 4.4° (0.2-71.5°), median axial and sagittal trajectory deviation from the planned trajectory were 2.5° (0 - 57.5°) and 3.3° (0 - 54.9°), respectively. Median operative time was 168 minutes (111 - 564 minutes), median blood loss was 300 ml (150 - 1300 ml) and median intraoperative fluoroscopic dose was 321.2 mGycm 2 (102.4 - 825.0 mGycm 2 ). Overall complications were one adjacent segment kyphosis, one transient C5 palsy and one wound healing disorder., Conclusion: Patient-specific 3D-printed templates provide a highly accurate option for placing cervical pedicle screws for dorsal instrumentation of the cervical spine., Competing Interests: None., (© 2022 The Author(s). Published by Elsevier Ltd on behalf of North American Spine Society.)

Several studies have reported incidence and risk factors for the development of proximal junctional kyphosis (PJK) in patients with adolescent idiopathic scoliosis (AIS). However, there is little information regarding long-term follow-up after pedicle screw instrumentation (PSI) with rod derotation (RD) and direct vertebral rotation (DVR). Sixty-nine AIS patients who underwent deformity correction using PSI with RD and DVR were retrospectively analyzed in two groups according to the occurrence of PJK, with a minimum five-year follow-up, including a non-PJK group ( n = 62) and PJK group ( n = 7). Radiological parameters were evaluated at preoperative, postoperative, and last follow-up. Incidence for PJK was 10.1% (7/69 patients), with a mean 9.4-year follow-up period. The thoracolumbar/lumbar curve (TL/L curve) was proportionally higher in the PJK group. The proximal compensatory curve was significantly lower in the PJK group than in the non-PJK group preoperatively ( p = 0.027), postoperatively ( p = 0.001), and at last follow-up ( p = 0.041). The development of PJK was associated with the TL/L curve pattern, lower preoperative proximal compensatory curve, and over-correction of the proximal curve for PSI with RD and DVR. Therefore, careful evaluation of compensatory curves as well as of the main curve is important to prevent the development of PJK in the treatment of AIS.

Background: Bony fusion rate was significantly lower in patients with type 3 Modic change than patients with normal endplates. It is not known whether there are relevant differences in fusion efficiency among patients with type 2 sclerotic Modic change or non-sclerotic Modic change, or no Modic change., Methods: A retrospective study contained 196 lumbar segments in 123 subjects undergoing posterior lumbar interbody fusion (PLIF) with pedicle screw instrumentation (PSI) to assess the effect of type 2 sclerotic Modic change on fusion efficiency. These endplates were allocated into groups A, B, and C, according to their Modic changes. Group A had endplates with type 2 Modic change and endplate sclerosis. Group B had type 2 Modic change without endplate sclerosis. Group C had neither Modic change nor endplate sclerosis. The presence of Modic change was determined by magnetic resonance imaging (MRI). Endplate sclerosis in type 2 Modic change was detected by computed tomography (CT) before the operation. We collected CT data 3 months to more than 24 months after operation in patients to assess bony fusion., Results: Incidences of bony fusion were 58.8% in group A, 95.0% in group B, 94.3% in group C. The bony fusion rate was significantly lower in group A than in either group B or C. There was no significant difference between groups B and C. Thus, endplates with type 2 sclerotic Modic change had a lower fusion rate in patients undergoing PLIF with PSI., Conclusion: Type 2 sclerotic Modic change could be an important factor that affects solid bony fusion in patients undergoing PLIF with PSI. CT may help diagnose endplate sclerosis in patients with type 2 change and inform the choice of the best site for spinal fusion.

Objectives: Temporary placement of an internal distraction rod is one of the surgical options in the treatment of severe scoliosis to avoid preoperative halo traction or vertebral column resection. This technique can be applied in a single session or staged. The aim of our study was to report the outcomes of less-invasive temporary internal distraction (LI-TID) in the surgical treatment of adolescents with severe idiopathic scoliosis (IS)., Methods: We performed a single-center, retrospective study of 22 adolescents (19 girls; mean age, 14.8 ± 2.0 years) with severe IS (major curve, ≥90°) who had undergone LI-TID, followed by staged pedicle screw instrumentation, with a minimum of 2 years of follow-up available. The demographic data, radiographic outcomes, pulmonary function test results, perioperative data, revised 22-item Scoliosis Research Society Outcomes questionnaire results, complications, and neuromonitoring data were collected., Results: The average major curve was 120° (range, 90°-160°) preoperatively and 59° (range, 29°-69°) at the final follow-up examination. Thoracic kyphosis (T5-T12) had improved from an average of 80° preoperatively to 33° postoperatively (range, 22°-69°), and the spinal height (T1-S1) had increased from 332 mm (range, 198-432 mm) preoperatively to 405 mm (range, 258-495 mm) at the final follow-up visit. Of the 22 patients, 5 (22.7%) had experienced an intraoperative neuromonitoring change without postoperative neurologic deficits, and 2 had developed superior mesenteric artery syndrome, with resolution after conservative treatment. The mean percentage of the predicted forced vital capacity had improved from 44.5% ± 11.3% to 66.5 ± 10.8 at final follow-up (P < 0.05). The total questionnaire score had improved significantly from 2.9 ± 0.61 to 4.1 ± 0.44 (P < 0.05)., Conclusion: The results from the present study have shown that staged LI-TID, followed by pedicle screw instrumentation, is safe and effective in adolescents with severe IS, with improvements in spinal deformity, pulmonary function, and health-related quality of life., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Objective: Neuromuscular scoliosis (NMS) is often associated with rapid progressive spinal deformities. Indications, when to extend the instrumentation to the pelvis for pelvic obliquity are not generally accepted at this time. This study reports on the indications, surgical technique and results using pedicle screw instrumentation exclusively with or without pelvic fixation for spine fusion in patients with NMS., Patients and Methods: Thirty-seven NMS patients were treated with pedicle screw instrumentation (PSI) between 2007 and 2013 with a minimum follow-up of 24 months. The mean age at the time of operation was 14.91 ± 2.03 years (range, 11.17-18.58). Posterior spine fusion (PSF) was conducted in 33 patients; 4 patients underwent a combined anterior spinal release followed by PSF during one-stage surgery. Pelvic fixation was achieved by ilium screws combined with S-1 screws in 4 cases and by sacral-alar-iliac (SAI) technique by Sponseller in 9 cases, respectively., Results: The mean primary Cobb angle was 65.5° (range, 14-103°) and improved significantly to 19.8° (range, 1-50°, p < 0.001) after surgery and 20.5° (range, 3-57, p = 0.47) at 2 years FU, respectively. Besides, an improvement of pelvic obliquity and T1 tilt angle could be detected. Major complications occurred in 19% and minor complications in 32%., Conclusion: Pedicle screw fixation only for spine fusion in patients with NMS can be applied safely with reasonable complication rates. An excellent correction in all planes, a significant improvement of the pelvic obliquity and almost no loss of correction at 2 years FU were observed., Competing Interests: Declaration of Competing Interest None., (Copyright © 2019 Royal College of Surgeons of Edinburgh (Scottish charity number SC005317) and Royal College of Surgeons in Ireland. Published by Elsevier Ltd. All rights reserved.)

Study Design: Case reports and review of the literature with a proposed management algorithm., Objectives: To report two cases of a potential vascular complication due to an incorrectly placed pedicle screw (PS) during spine deformity surgery. Relevant literature regarding the management of vascular complications is reviewed, and an evidence-based management algorithm is proposed. Aortic lesions represent a rare but potentially life-threatening complications with spine deformity and revision surgery, significantly increasing the risk. A management algorithm for an aortic lesion in the case of a malpositioned PS has not yet been published., Methods: Case 1: An 18-year-old female with proximal thoracic spinal non-instrumented fusion underwent a revision corrective procedure due to a progressive right-sided thoracolumbar compensatory curve. However, postoperative computed tomography (CT) performed to evaluate the position of the PS revealed malposition of the left T9 PS, which was abutting the descending aorta with CT angiography excluding the perforation of the aorta. Case 2: A 17-year-old male was scheduled for correction of Lenke 3-C-N adolescent idiopathic scoliosis. Postoperative routine evaluation with low-dose CT revealed a left T9 PS paravertebral malposition, and subsequent CTA demonstrated that the thread of the PS was in contact with the descending thoracic aorta and an unlikely hemodynamically significant vessel injury., Results: Successful removal of both malpositioned PS was performed. In the first case, a cardiovascular surgeon attended the operation if an urgent thoracotomy was needed, and in the second case, additional video-assisted thoracoscopic control of the aorta was performed during PS removal., Conclusions: Preoperative imaging in spinal surgery is essential to avoid major vascular and other complications when placing PS, especially in thoracic deformities. When a potential major vessel complication emerges, an interdisciplinary approach and an appropriate management algorithm are mandatory to make the best clinical decisions., Level of Evidence: 4.

Objective: To verify whether the pedicle screw placement (PSP) skills of young surgeons receiving immersive virtual reality surgical simulator (IVRSS) training could be improved effectively and whether the IVRSS-PSP training mode could produce a real clinical value in clinical surgery., Methods: Twenty-four young surgeons were equally randomized to a VR group and a NON-VR group. Participants in VR group received IVRSS-PSP training, and those in NON-VR group used the conventional model of observing a spinal model first and then watching a teaching video of spinal surgery for 40 minutes x five. The nailing outcome of the participants before and after training was evaluated by statistical analysis in both groups., Results: Post-training data analysis showed that the success rate and accuracy rate of screw placement in VR group and NON-VR group were 82.9% and 69.6% vs. 74.2% and 55.4%, respectively, showing statistically significant differences between the two groups by chi-square test (P < 0.05)., Conclusion: The present study demonstrated that IVRSS-PSP was helpful to improve the success rate of PSP for young surgeons, and may provide valuable reference for PSP training of young surgeons. In addition, our study also showed a promising potential of the VR technology in surgical simulation training.

Previous finite element studies of thoracolumbar fractures were mostly based on simulation analysis of one single object, which was difficult to objectively evaluate the differences between conventional pedicle screws and Schanz pedicle screws. The aim of this study was to evaluate the stress of screw and injured vertebrae displacement using the finite element model of conventional pedicle screw and Schanz pedicle screw instrumentation for the treatment of lumbar 1 fractures. Data of eight healthy volunteers were used to simulate the finite element model. The instrumentation models were divided into four groups: moderate fracture conventional (MC), moderate fracture Schanz (MS), unstable/severe fracture conventional (UC), and unstable/severe fracture Schanz (US) pedicle screw groups. The maximum screw stress and lumbar 1 displacement/micro-motion in each group increased with the increase of torque and/or load. Under the same fracture, maximum von Mises stress of conventional pedicle screw (MC/UC) was larger than Schanz pedicle screw (MS/US) (P < 0.05) and lumbar 1 displacement/micro-motion of Schanz pedicle screw (MS/US) was larger than conventional pedicle screw (MC/UC) (P < 0.05). Under the same screws, the maximum von Mises stress and displacement/micro-motion of unstable fracture (UC/US) were larger than moderate fracture (MC/MS) (P < 0.05). Posterior short-segment instrumentation with Schanz pedicle screws were recommended for unstable fractures. The compression displacement/micro-motion of bony defect during flexion may lead to the postoperative re-collapse of injured vertebrae.

Introduction: Adolescent idiopathic scoliosis (AIS) can lead to severe deformity. However, early detection and treatment can prevent its progression. Surgical instrumentation for scoliosis treatment has evolved from Harrington instrumentation to pedicle screws. However, there are still some concerns about the efficacy and long-term effects of pedicle screw fixation, and the clinical and radiographic outcomes of surgical treatment for severe AIS (>90°) by posterior spinal fusion alone need to be established., Presentation of Case: Eight patients with severe and rigid idiopathic scoliosis were recruited for this study. All surgeries were performed by one senior spine surgeon between 2015 and 2018. Free hand technique, intraoperative neurophysiologic monitoring (IONM), and intraoperative fluoroscopy to assess the screw position was performed., Discussion: Severe scoliosis results in a complex three-dimensional spinal deformity that often requires correction in multiple planes. Mean major coronal correction rate was 67% (45-80%). No major complications occurred during the perioperative period and after one year follow up., Conclusion: Pedicle screws provide three-dimensional deformity correction. There were no complications other than the low-grade late implant-associated infections. Posterior spinal fusion with pedicle screw-only instrumentation obtains a good and stable correction for severe scoliosis., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objective: We sought to compare the radiologic outcomes for different distal fusion levels in a rigid curve with major thoracolumbar and lumbar (TL/L) adolescent idiopathic scoliosis (AIS) using rod derotation (RD) with direct vertebral rotation (DVR) after pedicle screw instrumentation (PSI)., Methods: This study finally enrolled 28 patients who were diagnosed with AIS in rigid curve with major TL/L curves, treated by PSI with RD and DVR and with a minimum 2-year follow-up. Patients were divided into 2 groups, L3 and L4, on the basis of the distal fusion level at the lowest instrumented vertebra (LIV) of L3 or L4., Results: There was no significant difference in TL/L curve, thoracic (minor), and compensatory (caudal) curves between the L3 and L4 groups either postoperatively (P = 0.162, 0.426, and 0.762, respectively) or at the last follow-up (P = 0.952, 0.620, and 0.562, respectively). The overall prevalence of unsatisfactory results was 42.9% (12/28 patients). The prevalence of unsatisfactory results was 61.1% (11/18) in the L3 group and 10% (1/10) in the L4 group, which was significantly different (P < 0.05)., Conclusions: Unsatisfactory results occurred more often in the L3 group than in the L4 group, and unsatisfactory results had significant influence on progression of TL/L and distal compensatory curves. Such progression was closely correlated with deteriorating LIV disk angle in the L3 group. Therefore if the curve is rigid, LIV should be extended to L4 to avoid the adding-on phenomenon in the treatment of major TL/L AIS using RD with DVR after PSI., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: The optimal anchor density in adolescent idiopathic scoliosis (AIS) surgery to achieve good curve correction remains unclear. The purpose of the study is to analyze the correlations between three-dimensional curve correction and anchor density in the pedicle screw-based posterior fusion of AIS., Methods: One hundred and twenty-seven AIS patients receiving primary posterior fusion with pedicle screw instrumentation were retrospectively reviewed. Anchor density (AD) was defined as the screws number per fused spinal segment. The correlations between three-dimensional curve correction radiographic parameters and anchor density were analyzed with subgroup analysis based on different curve types, curve magnitudes, and curve flexibilities. The differences of curve correction parameters between the low-density (AD ≤1.4), middle-density (1.4 < AD ≤1.7) and high-density (AD > 1.7) groups were also calculated. Independent t-test, analysis of variance (ANOVA), and Pearson's correlation coefficient were used for statistical analysis., Results: There were no correlations between the anchor density and the coronal curve correction or apical vertebral rotation (AVR) correction. In the sagittal plane, mild positive correlations existed between anchor density and thoracic kyphosis correction in all patients (r = 0.27, p = 0.002). Subgroup analysis revealed similar mild positive correlations in Lenke 1 (r = 0.31, p = 0.02), Lenke 1-3 (r = 0.27, p = 0.01), small curves (40°-60°, r = 0.38, p <  0.001), and flexible curves (flexibility > 40%, r = 0.34, p = 0.01). There were no differences between low-density (mean 1.31), middle-density (mean 1.55), and high-density (mean 1.83) in terms of coronal or axial curve correction parameters. Low-density group has longer fused level (mean difference 2.14, p = 0.001) and smaller thoracic kyphosis correction (mean difference 9.25°, p = 0.004) than high-density group., Conclusion: In our study, the anchor density was not related to coronal or axial curve corrections. Mild positive correlations with anchor density were found in thoracic kyphosis correction, especially in patients with smaller and flexible curves. Low anchor density with longer fusion level achieves similar curve corrections with middle or high anchor density in adolescent idiopathic scoliosis surgery.

Objective: To analyze the effects of direct vertebral rotation (DVR) on radiologic outcomes in the treatment of thoracic adolescent idiopathic scoliosis after selective thoracic fusion with pedicle screw instrumentation., Methods: Adolescent idiopathic scoliosis patients with single thoracic curves (n = 110) treated by selective thoracic fusion with a minimum of 2 years of follow-up were retrospectively analyzed. The patients were separated into 2 groups: non-DVR (n = 63) and DVR (n = 47)., Results: There was a significant difference in fused segments between the non-DVR and DVR groups (P < 0.001). There was also a significant difference in main thoracic curve postoperatively (P = 0.001) and at the last follow-up (P = 0.006) between the non-DVR and DVR groups. However, there was no significant difference in proximal thoracic and lumbar curves postoperatively (proximal thoracic curve: P = 0.186; lumbar curve: P = 0.155) and at the last follow-up (proximal thoracic curve: P = 0.250; lumbar curve: P = 0.060) between the 2 groups. Significant improvements in the lowest instrumented vertebra tilt and disc angle were noted but then slight deteriorations in such were observed during the follow-up period in the non-DVR group. The prevalence of unsatisfactory results was 20.6% (13 of 63) in the non-DVR group and 19.1% (9 of 47) in the DVR group, with no significant difference (P = 0.522)., Conclusions: For correcting single thoracic adolescent idiopathic scoliosis by selective thoracic fusion with pedicle screw instrumentation, the addition of DVR to the surgical procedure showed comparable radiologic outcomes compared with non-DVR procedures., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objective: Pedicle screw instrumentation is widely used for spinal deformity correction and fusion in adolescents for idiopathic scoliosis. The goal is to achieve and sustain good alignment in all 3 planes. We compared 2 different cobalt-chromium (CoCr) rod designs with different stiffnesses with regard to the restoration of coronal and sagittal balance in adolescents operated on for idiopathic scoliosis., Material and Methods: A prospective comparative study was made of 90 consecutive adolescents, mean age (standard deviation) 15.6 years (2.1 years), with idiopathic scoliosis who underwent posterior spinal fusion by the use of bilateral segmental pedicle screw instrumentation (PSI) with 6.0 Co-Cr rods. Fifty-four adolescents (43 girls) were operated on by the use of circular rods and 36 (27 girls) by the use of sagittal reinforced rods, with a 2-year follow-up., Results: Preoperative major coronal curves were similar and at 2 years: 11° (5.0) and 17° (7.2) with correction percentages of 78% (10) and 69% (12) in the circular and reinforced rod groups (P < 0.01). Thoracic kyphosis at 2 years measured 16° (7) and 21° (6) in the circular and reinforced rod groups (P < 0.01). The number of patients with hypokyphosis was lower in the reinforced rod group at 2 years (P = 0.02). In the reinforced rod group, there was a negative correlation between coronal correction and thoracic kyphosis (r = -0.52, P < 0.01)., Conclusions: Both circular and sagittal reinforced 6.0-mm CoCr rods provide adequate coronal correction for adolescents with idiopathic scoliosis. The use of sagittal reinforced rods provided better thoracic kyphosis restoration and a lower risk for postoperative hypokyphosis., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objective: To develop finite element models of spine following osteotomy and evaluate the effect of number and location of cross-links (CLs) on long-segment instrumentation., Methods: A finite element model of instrumented spine following osteotomy was created from computed tomography images of a postoperative male patient with thoracolumbar kyphotic deformity. Five fixation models were established to simulate different number and location of CLs. Four loading conditions (flexion, extension, lateral bending, and axial rotation) were applied on the models. Range of motion (ROM), maximum value and distribution of stress on implants, and stress on vertebrae were compared between models., Results: With increased number of CLs, average ROM of instrumented segments was reduced by 2.37%, 1.89%, and 2.49% in flexion, extension, and lateral bending. ROM was reduced by 21.98% in loading axial rotation condition. With increased number of CLs, ROM tended to be limited. Peak stresses were located on rods during axial rotation, on proximal pedicle screws during flexion, and on the osteotomy site during extension and lateral bending. CLs had an effect of dispersing stress concentration., Conclusions: The application of CLs enhanced the rigidity of the construct. With increased number of CLs, ROM of the construct was decreased, especially in axial rotation. CLs can also disperse the stress concentration. After comparing various CL configurations in different motion conditions, we believe that the optimal method is to place 2 CLs at the osteotomy site and the proximal segment., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background and Aims:: To compare outcomes between posterior spinal fusion of juvenile idiopathic scoliosis and adolescent idiopathic scoliosis patients with a minimum of 2-year follow-up. The juvenile idiopathic scoliosis patients were fused to the stable vertebra and adolescent idiopathic scoliosis to the touched vertebra. We hypothesized that extending the spinal fusion to the stable vertebra in juvenile patients would provide similar outcomes compared with fusion to the touched vertebra in adolescents., Materials and Methods:: A prospective comparative study of 21 consecutive children with juvenile (Risser 0) and 84 adolescent (Risser ⩾2) idiopathic scoliosis (1:4 ratio) undergoing bilateral segmental pedicle screw instrumentation and direct vertebral derotation with a minimum of 2-year follow-up., Results:: Juvenile patients had a significantly larger main curve (58° vs 53°, p = 0.003), more fused levels (p = 0.012) and posterior column osteotomies (p = 0.014) than adolescent patients. Distal adding-on (>10°) was observed in one (4.7%) juvenile and three (3.6%) adolescent patients (p = 0.80), without the need for revisions. Scoliosis Research Society 24 total score averaged 101 in juvenile and 97 in adolescent group at 2-year follow-up (p = 0.047)., Conclusion:: Posterior spinal fusion with bilateral segmental pedicle screw instrumentation to the stable vertebra provides similar clinical and radiographic outcomes in juvenile patients as compared with adolescents with fusion to the touched vertebra in idiopathic scoliosis. Health-related quality of life as measured using the Scoliosis Research Society 24 questionnaire at the end of follow-up was better in the juvenile as compared with the adolescent group.

In spine surgery, pedicle screw instrumentation is being used very commonly. However, putting pedicle screws in the right place and direction needs the use of image intensifier in 2 orthogonal planes. This consumes valuable time while moving the image intensifier and operating table multiple times during the surgery and also excess radiation exposure. Here, we present a simple technique to apply surgical pearl to angulate the pedicle screws in cephalocaudal direction using simple instrument available on table. This may help in reducing the usage of image intensifier and expedite the procedure.

Background: The aim of our study was to identify factors that influence the occurrence of adjacent fractures in patients with cement-augmented pedicle screw instrumentation., Methods: Data were retrospectively collected from medical charts and operative reports for every surgery in which cement-augmented instrumentation was used in our hospital of 4 consecutive years. A total of 93 operations were included and examined for gender, age, T-score, number of fused segments, number of implanted screws, broken screws, loosening of screws, leakage and distribution pattern of cement, pre- and postoperative kyphosis angle, revision surgery and adjacent fractures in follow-up. Categorical data were compared using the χ 2 test or by Fisher's exact test, as appropriate. Continuous variables conforming to a normal distribution were compared using Student's t test. Otherwise the Mann-Whitney U test was applied. A P -value of <.05 was considered statistically significant. A trend was defined as a P < .2., Results: The mean age was 68.1 years with a mean T-score of -3.12. Nineteen adjacent fractures occurred during follow-up and the median follow-up was 12 months (range, 1-27). Patients showed a higher risk for adjacent fractures following revision surgery ( P = .016). Most fractures occurred superior to the instrumented level ( P = .013) and in the first 12 months. Difference of T-score between the group "no adjacent fracture" and the group "adjacent fracture" was 0.7 ( P = .138). Another trends were found in greater age ( P = .119) and long instrumentations ( P = .199)., Conclusions and Clinical Relevance: Revision surgeries are associated with a higher risk of adjacent fractures. In these cases, prophylactic kyphoplasty of the superior vertebra should be considered. This study is a retrospective, nonrandomized cohort/follow-up study., Level of Evidence: 3., Competing Interests: Disclosures and COI: The authors received no funding for this study and report no conflicts of interest.

Background: Postoperative urinary retention has been reported to affect up to 27% of adults undergoing degenerative lumbar spine surgery and approximately one-third of children undergoing lower-extremity orthopedic surgery. No data exist on the incidence and risk factors of postoperative urinary tract retention/difficulties to empty the bladder in young patients undergoing instrumented posterior spinal fusion. We aimed to characterize incidence, risk factors and treatment of postoperative urinary retention (POUR) and difficulties to empty the bladder in young patients undergoing posterior spinal fusion (PSF) for idiopathic scoliosis., Methods: One hundred and eleven consecutive patients (mean age 16years [range, 11-21years], 81 females and 30 males) undergoing PSF for adolescent idiopathic scoliosis were screened after removal of urinary catheter postoperatively for inability to void and residual volume of urinary bladder. The latter was measured using ultrasound on two separate occasions. POUR and the need for intermittent catheterization were defined as an inability to void after catheter removal and documented full bladder with ultrasound (a residual of 300mL or more) or a significant residual volume after voiding (>2mL/kg or >100mL)., Results: Fifty-one (46%) of the patients were either unable to void or had a clinically significant amount of residual volume after voiding. These fifty-one patients required intermittent catheterization for a mean of two days. Thirty patients (27%) had POUR, a residual volume of 300mL or more. Two (1.8%) patients experienced urinary tract infection postoperatively. Patients with urinary retention had a significantly higher mean intraoperative blood loss (mean 626mL vs. 464mL; p=0.020) and longer operation time (mean 3.3h vs. 2.8h; p=0.009) as compared with those not having urinary retention. In multivariate analyses the main risk factor for urinary retention was male gender (odds ratio 3.2 [95% confidence interval 1.1-9.2], p=0.028)., Conclusions: Postoperative voiding difficulties affect almost half of the patients with age under 21years undergoing PSF for idiopathic scoliosis. The main risk factors were increased intraoperative blood loss, longer length of surgery and male gender. POUR should be actively screened and treated in this patient population., Level of Evidence: Prospective Cohort Study II., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: Training beginners of the pedicle screw instrumentation technique in the operating room is limited because of issues related to patient safety and surgical efficiency. Three-dimensional (3D) printing enables training or simulation surgery on a real-size replica of deformed spine, which is difficult to perform in the usual cadaver or surrogate plastic models. The purpose of this study was to evaluate the educational effect of using a real-size 3D-printed spine model for training beginners of the free-hand pedicle screw instrumentation technique. We asked whether the use of a 3D spine model can improve (1) screw instrumentation accuracy and (2) length of procedure., Methods: Twenty life-size 3D-printed lumbar spine models were made from 10 volunteers (two models for each volunteer). Two novice surgeons who had no experience of free-hand pedicle screw instrumentation technique were instructed by an experienced surgeon, and each surgeon inserted 10 pedicle screws for each lumbar spine model. Computed tomography scans of the spine models were obtained to evaluate screw instrumentation accuracy. The length of time in completing the procedure was recorded. The results of the latter 10 spine models were compared with those of the former 10 models to evaluate learning effect., Results: A total of 37/200 screws (18.5%) perforated the pedicle cortex with a mean of 1.7 mm (range, 1.2-3.3 mm). However, the latter half of the models had significantly less violation than the former half (10/100 vs. 27/100, p < 0.001). The mean length of time to complete 10 pedicle screw instrumentations in a spine model was 42.8 ± 5.3 min for the former 10 spine models and 35.6 ± 2.9 min for the latter 10 spine models. The latter 10 spine models had significantly less time than the former 10 models (p < 0.001)., Conclusion: A life-size 3D-printed spine model can be an excellent tool for training beginners of the free-hand pedicle screw instrumentation.

Background: Recent studies have shown higher accuracy rates of image-guided pedicle screw placement compared to freehand (FH) placement. However, data focusing on the impact of spinal navigation on the rate of revision surgeries caused by misplaced pedicle screws (PS) are scarce., Objective: This study is aimed at identifying the rate of revision surgeries for misplaced PS comparing three-dimensional (3D) fluoroscopy navigation (3DFL) with FH PS placement., Methods: A retrospective analysis was conducted of 2232 patients (mean age, 65.3 ± 13.5 years) with 13,703 implanted PS who underwent instrumentation of the thoracolumbar spine between 2007 and 2015. Group 1 received surgery with use of 3DFL (January 2011 to December 2015), group 2 received surgery in the FH technique (April 2007 to December 2015). Because the use of 3DFL was initiated in January 2011, the examined period for 3DFL-navigated surgeries is shorter. Patients routinely received postoperative computed tomography scans and/or intraoperative control 3D scans., Results: There was an overall rate of revision surgeries for malpositioned PS of 2.9%. In the 3DFL group, the rate of secondary revision surgeries was significantly lower with 1.35% (15/1112 patients) compared to 4.38% (49/1120 patients) in the FH group, respectively (odds ratio, 3.35; P < 0.01). Of all PS in the 3DFL group (30/7548 PS), 0.40% needed revision surgery (P < 0.01) compared to 1.14% in the FH group (70/6155 PS)., Conclusions: We were able to show that the use of 3DFL-navigated PS placement significantly reduces the rate of revision surgeries after posterior spinal instrumentation compared to freehand PS placement., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Pars and pedicle fractures as a result of CBT (cortical bone trajectory) during pedicle screw placement have been reported. The primary aim of the study is to compare the fracture rate between screws with modular heads to screws with standard pre-assembled tulip heads. The secondary aim of the study is to determine the potential variables that can be identified prior to instrumentation in order to predict risk of fractures. Twenty-four fresh frozen lumbar vertebrae were obtained from five different cadavers. Anatomical landmark measurements were obtained. Right and left pedicles of each vertebra were randomly instrumented with the preassembled head screws (n=24) and modular head screws (n=24) under video recording. X-ray images were obtained for measuring relative angle deviations between tapped and final screw trajectories. Finally, pullout tests were performed. Seventeen out of twenty-four (70.8%) of the spinous processes had to be excised in order to obtain proper trajectories. Six fractures occurred with pre-assembled head screws versus one in the modular head screws (p=0.04). Distances from the midline to the medial wall of the pedicle were marginally significant as a predictor for fracture (p=0.08). The pullout loads between both types of screws were not statistically different (p=0.38). Age was better correlated with pullout load than absolute bone density value (p<0.001). In conclusion, modular head screws had a significantly lower fracture rate than pre-assembled head screws for cortical bone trajectory in osteoporotic bone. There was no clear anatomic variable that could be measured pre-operatively to predict potential fracture risk in CBT., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Aims: In a multicentre, randomised study of adolescents undergoing posterior spinal fusion for idiopathic scoliosis, we investigated the effect of adding gelatine matrix with human thrombin to the standard surgical methods of controlling blood loss., Patients and Methods: Patients in the intervention group (n = 30) were randomised to receive a minimum of two and a maximum of four units of gelatine matrix with thrombin in addition to conventional surgical methods of achieving haemostasis. Only conventional surgical methods were used in the control group (n = 30). We measured the intra-operative and total blood loss (intra-operative blood loss plus post-operative drain output)., Results: Each additional hour of operating time increased the intra-operative blood loss by 356.9 ml (p < 0.001) and the total blood loss by 430.5 ml (p < 0.001). Multiple linear regression analysis showed that the intervention significantly decreased the intra-operative (-171 ml, p = 0.025) and total blood loss (-177 ml, p = 0.027). The decrease in haemoglobin concentration from the day before the operation to the second post-operative day was significantly smaller in the intervention group (-6 g/l, p = 0.013) than in the control group., Conclusion: The addition of gelatine matrix with human thrombin to conventional methods of achieving haemostasis reduces both the intra-operative blood loss and the decrease in haemoglobin concentration post-operatively in adolescents undergoing posterior spinal fusion for idiopathic scoliosis., Take Home Message: A randomised clinical trial showed that gelatine matrix with human thrombin decreases intra-operative blood loss by 30% when added to traditional surgical haemostatic methods in adolescents undergoing posterior spinal fusion for idiopathic scoliosis., (©2016 The British Editorial Society of Bone & Joint Surgery.)

Background Context: Cortical bone trajectory (CBT) technique for pedicle screw placement in the lumbar spine has become more popular since its introduction in 2009. The distinct advantages of using the CBT technique involve increased screw purchase within the cortical bone and reduced surgical dissection. However, contrary to several favorable biomechanical results, there were anecdotal reports of clinical complications associated with CBT., Purpose: This study aimed (1) to report on two unique pars and pedicle fracture cases involving the use of the CBT technique and (2) to perform a cadaveric pilot study to determine the possible mechanism for this fracture pattern., Study Design/setting: A case report and cadaveric study were carried out., Methods: After presenting two clinical cases, 19 fresh-frozen lumbar vertebrae were obtained from 8 cadavers. Pedicle screws were instrumented on each level using CBT under video recording. After the instrumentation, X-ray images were obtained, and anatomical dissections were performed., Results: To be able to reach a necessary angle for medial to lateral CBT trajectory, 13 out of 19 (68%) spinous processes had to be removed. There were a total of seven complications. One pars and pedicle fracture out of 37 trajectories (2.7%) and 6 out of 37 trajectory deviations (16.2%), which resulted in gross loosening, were observed., Conclusions: The head of the pedicle screw impinging on the base of spinous process and lamina was observed in our cadaveric model. This mechanism could potentially explain both screw loosening and fractures associated with the CBT technique., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objective: Lumbar spinal stenosis is conventionally treated with surgical decompression. However, bilateral decompression and laminectomy is more invasive and may not be necessary for lumbar stenosis patients with unilateral radiculopathy. We aimed to report the outcomes of unilateral laminectomy and bilateral pedicle screw fixation with fusion for patients with lumbar spinal stenosis and unilateral radiculopathy., Methods: Patients with lumbar spinal stenosis with unilateral lower extremity radiculopathy who received limited unilateral decompression and bilateral pedicle screw fixation were included and evaluated using visual analog scale (VAS) pain and the Oswestry Disability Index (ODI) scores preoperatively and at follow-up visits. Ligamentum flavum thickness of the involved segments was measured on axial magnetic resonance images., Results: Twenty-five patients were included. The mean preoperative VAS score was 6.6±1.6 and 4.6±3.1 for leg and back pain, respectively. Ligamentum flavum thickness was comparable between the symptomatic and asymptomatic side (p=0.554). The mean follow-up duration was 29.2 months. The pain in the symptomatic side lower extremity (VAS score, 1.32±1.2) and the back (VAS score, 1.75±1.73) significantly improved (p=0.000 vs. baseline for both). The ODI improved significantly postoperatively (6.60±6.5; p=0.000 vs. baseline). Significant improvement in VAS pain and ODI scores were observed in patients receiving single or multi-segment decompression fusion with fixation (p<0.01)., Conclusion: Limited laminectomy and unilateral spinal decompression followed by bilateral pedicle screw fixation with fusion achieves satisfactory outcomes in patients with spinal stenosis and unilateral radiculopathy. This procedure is less damaging to structures that are important for maintaining posterior stability of the spine.

Background: Various techniques have been described for pedicle screw placement with established clinical and radiological success. Suboptimal screw trajectories can compromise bony purchase and, worse yet, cause neurological and vascular injuries. Thus, it is of paramount importance to achieve maximum accuracy of screw placement. Our objective is to evaluate the accuracy of pedicle screw placement in the thoracolumbar spine by resident surgeons. Two popular techniques, gearshift versus drill, were compared., Methods: This is a a cadaveric surgical technique comparison study. Six resident surgeons instrumented the spine from T1 to S1 using both gearshift and drill techniques. Each pedicle was randomly assigned to either of the techniques. Pedicle screws were placed freehand without radiographic guidance. Violations (medial, lateral, anterior, superior and inferior) were recorded by studying the computerized tomographic scans of instrumented cadavers by blinded observers. Critical perforations were defined as greater than 2mm breach of the pedicle wall., Results: A total of 100 vertebrae (200 pedicles) were instrumented in the six cadavers. 103 pedicles were breached (51.5% of total pedicles). Lateral violations were the most encountered (65% of violations, 67 total, 48 critical, 19 noncritical) followed by medial (24%, 25 total, 13 critical, 12 noncritical), and the rest were anterior (3%), superior (4%) and inferior (4%). There was no overall difference in violations comparing the gearshift technique (49.5%, 51 total, 37 critical, 14 noncritical) with drill technique (50.5%, 52 total, 33 critical, 19 noncritical). Analyzing the breaches at individual vertebra indicated most violations at T6 (11), T5 (10), followed by T3 (9) and T4 (9), decreasing towards the lumbosacral vertebrae., Conclusion: The results of this study suggest that the gearshift and drill techniques for placement of pedicle screws in the thoracolumbar spine fare similarly with regards to risk of breach when applied by resident surgeons.

Clinical, radiological, and Scoliosis Research Society-22 questionnaire data were reviewed pre-operatively and two years post-operatively for patients with thoracolumbar/lumbar adolescent idiopathic scoliosis treated by posterior spinal fusion using a unilateral convex segmental pedicle screw technique. A total of 72 patients were included (67 female, 5 male; mean age at surgery 16.7 years (13 to 23)) and divided into groups: group 1 included 53 patients who underwent fusion between the vertebrae at the limit of the curve (proximal and distal end vertebrae); group 2 included 19 patients who underwent extension of the fusion distally beyond the caudal end vertebra. A mean scoliosis correction of 80% (45% to 100%) was achieved. The mean post-operative lowest instrumented vertebra angle, apical vertebra translation and trunk shift were less than in previous studies. A total of five pre-operative radiological parameters differed significantly between the groups and correlated with the extension of the fusion distally: the size of the thoracolumbar/lumbar curve, the lowest instrumented vertebra angle, apical vertebra translation, the Cobb angle on lumbar convex bending and the size of the compensatory thoracic curve. Regression analysis allowed an equation incorporating these parameters to be developed which had a positive predictive value of 81% in determining whether the lowest instrumented vertebra should be at the caudal end vertebra or one or two levels more distal. There were no differences in the Scoliosis Research Society-22 outcome scores between the two groups (p = 0.17). In conclusion, thoracolumbar/lumbar curves in patients with adolescent idiopathic scoliosis may be effectively treated by posterior spinal fusion using a unilateral segmental pedicle screw technique. Five radiological parameters correlate with the need for distal extension of the fusion, and an equation incorporating these parameters reliably informs selection of the lowest instrumented vertebra., (©2014 The British Editorial Society of Bone & Joint Surgery.)

Background Context: Conventionally, short-segment fusion involves instrumentation of one healthy vertebra above and below the injured vertebra, skipping the injured level. This short-segment construct places less surgical burden on the patient compared with long-segment constructs, but is less stable biomechanically, and thus has resulted in clinical failures. The addition of two screws placed in the fractured vertebral body represents an attempt to improve the construct stiffness without sacrificing the benefits of short-segment fusion., Purpose: To determine the biomechanical differences between four- and six-screw short-segment constructs for the operative management of an unstable L1 fracture., Study Design: Biomechanical study of instrumentation in vertebral body cadaveric models simulating an L1 axial load injury pattern., Methods: Thirteen intact spinal segments from T12 to L2 were prepared from fresh-frozen cadaver spines. An axial load fracture of at least 50% vertebral body height was produced at L1 and then instrumented with pedicle screws. Specimens were evaluated in terms of construct stiffness, motion, and rod strain. Two conditions were tested: a four-screw construct with no screws at the L1 fractured body (4S) and a six-screw construct with screws at all levels (6S). The two groups were compared statistically by paired Student t test., Results: The mean stiffness in flexion-extension was increased 31% (p<.03) with the addition of the two pedicle screws in L1. Relative motion in terms of vertical and axial rotations was not significantly different between the two groups. The L1-L2 rod strain was significantly increased in the six-screw construct compared with the four-screw construct (p<.001)., Conclusions: In a cadaveric L1 axial load fracture model, a six-screw construct with screws in the fractured level is more rigid than a four-screw construct that skips the injured vertebral body., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background Context: Surgical indications and procedures for spinal Langerhans cell histiocytosis (LCH) in children are still controversial. Reports containing large samples of surgically treated patients are few in the currently available literature, and the reported operative procedures were also somewhat obsolete. So, further investigation based on large-sample cases and using improved surgical techniques is beneficial and helpful to refine the treatment strategy., Purpose: To recommend a reasonable treatment strategy for thoracic or lumbar spine LCH in children complicated with neurologic deficit., Study Design/setting: Retrospective/academic medical center., Patient Sample: Twelve children aged from 2 to 16 years old with the diagnosis of thoracic or lumbar spinal LCH accompanied by neurologic deficit received surgical treatment from January 2005 to January 2010., Outcome Measures: Frankel scale for neurologic function, fusion of the mass, and recurrence of the lesion., Methods: All 12 patients presented initially with local pain and progressive neurologic detriment. Neurologic evaluation revealed two patients with Frankel Grade B, eight with Grade C, and two with Grade D. Radiographic features were positive for typical vertebra plana, a space-occupying mass in the spinal canal compressing neural elements, and a spinal canal encroachment rate more than 50%. Posterior instrumentation with pedicle screw combined with anterior corpectomy, decompression, and support bone graft was performed in the first seven patients as a one-stage procedure. In the remaining five patients, posterior pedicle screw fixation, laminectomy for decompression (via excision of the tumor-like mass), and repair of laminae with allograft bone block were performed. The collapsed vertebral body was left untouched. No chemotherapy or radiotherapy was administrated postoperatively in any of the cases., Results: The mean follow-up duration was 43.3 months. The mean operation time was 330 minutes with combined procedure and 142 minutes with single posterior approach (p=.000). The average blood loss was 933 mL with combined procedure and 497 mL with single posterior approach (p=.039). Three of seven patients who received combined surgery encountered approach-related complications, that is, one with intercostal neuralgia and two with pleural effusion. No severe neurologic deteriorate, instrumentation failure, or disease recurrence was detected at follow-up. Neurologic function completely recovered in all 12 patients from 2 to 12 weeks after surgery. The anterior bone graft fused and shaped well in all seven patients, and allograft bone block for lamina repair also achieved complete fusion in the remaining five patients. The internal fixator was removed at 3 to 5 years (average 4.1 years) after initial operation in six patients. No deformity, including scoliosis and kyphosis, has been identified during follow-up period in both procedures., Conclusions: For spinal LCH patients, neurologic deficit is a main indication for operative treatment to prevent permanent and serious consequences. Surgery provides an opportunity for rapid recovery of neurologic function. Both combined and single-stage posterior approaches based on pedicle screw instrumentation techniques are similarly effective in relieving neurologic compression. However, single-stage posterior approach is more favorable with less complications, and preserving involved vertebral body is not a latent hazard of recurrence., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background Context: Congenital kyphoscoliosis is a disorder that often requires surgical treatment. Although many methods of surgical treatment exist, posterior-only vertebral column resection with instrumentation and fusion seem to have become the gold standard for very severe and very rigid curves. Multiple chevron and concave rib osteotomies have been previously reported to be effective in the treatment of neglected severe idiopathic curves. We hypothesized that this method may also be used successfully in the treatment of congenital kyphoscoliosis., Purpose: To evaluate the effectiveness and safety of multiple chevron osteotomies combined with concave rib osteotomy and posterior pedicle screw instrumentation., Study Design: Retrospective chart review in the spine service of a large university hospital., Patient Sample: Adolescent patients undergoing a specific surgical treatment for the indication of rigid congenital kyphoscoliotic deformity., Outcome Measures: Radiographic images were used for the measurement of deformity correction. The Turkish version of the Scoliosis Research Society 22 (SRS-22) Patient Questionnaire has been used as a clinical outcome measure in the patient population., Methods: A retrospective chart review was performed. Patients admitted to Hacettepe Hospital Spine Center during the period of 2005 to 2009 were included. Criteria for inclusion were as follows: adolescent age group (10-16 years); congenital kyphoscoliosis; formation and/or segmentation defect of at least two vertebral motion segments; surgical treatment of deformity by posterior all-pedicle screw instrumentation, multiple chevron osteotomies, and multiple concave rib osteotomies; follow-up of at least 24 months; and a complete set of preoperative, postoperative, and follow-up standing posteroanterior and lateral full spinal radiographs. The patients' hospital records and X-rays were reviewed. Duration of surgery, intraoperative blood loss, postoperative transfusion requirements, postoperative stay in postanesthesia care unit (PACU), time of hospitalization, and complications were recorded. Deformity in both coronal and sagittal planes was analyzed for correction and maintenance of the correction in preoperative, postoperative, and follow-up radiographs. Patients' health-related quality of life was assessed using the SRS-22 questionnaire at the final follow-up., Results: Eighteen patients met the inclusion criteria. Their average age was 13.6 years (range, 11-16 years). Chevron osteotomies were performed at apical segments (three to seven levels) and concave rib osteotomies at Cobb-to-Cobb (five to eight levels). No patient had preoperative cord compression because of the sharply angulated deformity or neurologic deficit. The average preoperative scoliosis was 66.0° (range, 31°-116°), 52.4° (range, 22°-85°) on flexibility X-rays, and became 24.9° (range, 12°-52°) postoperatively. The average preoperative global kyphosis (T2-T12) of 75.9° (range, 50°-106°) became 49.5° (range, 18°-66°). The average preoperative local kyphosis of 71.9° (range, 35°-114°) became 31.4° (range, -44° to 64°). The average intraoperative bleeding was 989 cc, surgical time was 292 minutes, and intraoperative transfusion was 2.3 units. The maximum PACU stay was overnight. There were no neurologic complications except one pneumothorax and one pneumonia. The average follow-up was 34.3 months. At follow-up, average scoliosis was 27.5° (range, 10°-50°), global kyphosis was 50.3° (range, 28°-73°), and local kyphosis was 36.9°(range, -36° to 58°). Performed on the last follow-up, the average scores for the five domains of SRS-22 were 4.3, 4.4, 4.2, 4.1, and 4.8 for function, pain, self-image, mental health, satisfaction, and total, respectively., Conclusions: Multiple chevron and concave rib osteotomies with posterior instrumentation provide an acceptable rate of deformity correction and maintenance of correction at 2 years with acceptable intraoperative bleeding, surgical time, postoperative morbidity, and rate of complications. It can be considered as an alternative in the treatment of rigid congenital curves involving more than three levels or multiple curves separated by at least two segments that would otherwise require multiple vertebral resections., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Posterior instrumentation is a common fixation method used to treat thoracolumbar burst fractures. However, the role of different cross-link configurations in improving fixation stability in these fractures has not been established. A 3D finite element model of T11-L3 was used to investigate the biomechanical behavior of short (2 level) and long (4 level) segmental spine pedicle screw fixation with various cross-links to treat a hypothetical L1 vertebra burst fracture. Three types of cross-link configurations with an applied moment of 7.5 Nm and 200 N axial force were evaluated. The long construct was stiffer than the short construct irrespective of whether the cross-links were used (p < 0.05). The short constructs showed no significant differences between the cross-link configurations. The XL cross-link provided the highest stiffness and was 14.9% stiffer than the one without a cross-link. The long construct resulted in reduced stress to the adjacent vertebral bodies and screw necks, with 66.7% reduction in bending stress on L2 when the XL cross-link was used. Thus, the stability for L1 burst fracture fixation was best achieved by using long segmental posterior instrumentation constructs and an XL cross-link configuration. Cross-links did not improved stability when a short structure was used., (Copyright © 2013 Orthopaedic Research Society.)

The pedicle is a power nucleus of the vertebra and offers a secure grip of all 3 columns. Pedicle screw instrumentation has advantages of rigid fixation with improved three-dimensional (3D) correction and it is accepted as a reliable method with a high margin of safety. Accurate placement of the pedicle screws is important to reduce possible irreversible complications. Many methods of screw insertion have been reported. The author has been using the K-wire method coupled with the intraoperative single posteroanterior and lateral radiographs, which is the most safe, accurate and fast method. Identification of the curve patterns and determining the fusion levels are very important. The ideal classification of adolescent idiopathic scoliosis should address the all patterns, predict the extent of accurate fusion and have good inter/intraobserver reliability. My classification system matches with the ideal classification system, and it is simple and easy to learn; and my classification system has only 4 structural curve patterns and each curve has 2 types. Scoliosis is a 3D deformity; the coronal and sagittal curves can be corrected with rod rotation, and rotational deformity has to be corrected with direct vertebral rotation (DVR). Rod derotation and DVR are true methods of 3D deformity correction with shorter fusion and improved correction of both the fused and unfused curves, and this is accomplished using pedicle screw fixation. The direction of DVR is very important and it should be opposite to the direction of the rotational deformity of the vertebra. A rigid rod has to be used to prevent rod bend-out during the derotation and DVR.

Objective: The current literature implies that the use of short-segment pedicle screw fixation for spinal fractures is dangerous and inappropriate because of its high failure rate, but favorable results have been reported. The purpose of this study is to report the short term results of thoracolumbar burst and compression fractures treated with short-segment pedicle instrumentation., Methods: A retrospective review of all surgically managed thoracolumbar fractures during six years were performed. The 19 surgically managed patients were instrumented by the short-segment technique. Patients' charts, operation notes, preoperative and postoperative radiographs (sagittal index, sagittal plane kyphosis, anterior body compression, vertebral kyphosis, regional kyphosis), computed tomography scans, neurological findings (Frankel functional classification), and follow-up records up to 12-month follow-up were reviewed., Results: No patients showed an increase in neurological deficit. A statistically significant difference existed between the patients preoperative, postoperative and follow-up sagittal index, sagittal plane kyphosis, anterior body compression, vertebral kyphosis and regional kyphosis. One screw pullout resulted in kyphotic angulation, one screw was misplaced and one patient suffered angulation of the proximal segment on follow-up, but these findings were not related to the radiographic findings. Significant bending of screws or hardware breakage were not encountered., Conclusion: Although long term follow-up evaluation needs to verified, the short term follow-up results suggest a favorable outcome for short-segment instrumentation. When applied to patients with isolated spinal fractures who were cooperative with 3-4 months of spinal bracing, short-segment pedicle screw fixation using the posterior approach seems to provide satisfactory result.