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Background Context: Pedicle screws (PS) offer great benefits in posterior lumbar interbody fusion (PLIF), but several drawbacks of PS, including the risk of superior facet joint violation and muscle injury, have also pointed out. Recently, cortical screws (CS) were invented, which can be placed without the drawbacks associated with PS. However, whether CS in PLIF can provide similar or greater clinical and radiologic outcomes compared to those of PS has not been fully evaluated in clinical research studies., Purpose: To evaluate whether the CS provides similar results to the PS in PLIF, in terms of fusion rate, clinical and surgical outcomes, and complications., Study Design: This is a prospective, randomized, noninferiority trial., Patient Sample: Seventy-nine eligible patients were randomly assigned to either Group A (39 patients), for which PS was used, or Group B (40 patients), for which CS was used., Outcome Measures: The primary study end point was to measure fusion rate using dynamic radiographs and computed tomography scans. Secondary end points included intensity of low back pain and pain radiating to the leg using visual analog scales, and also, functional status using the Oswestry Disability Index, surgical morbidity, and additional outcomes such as pedicle fracture and mechanical failure., Methods: We compared baseline data in both groups. To evaluate the efficacy of CS in PLIF compared to PS, we compared fusion rates, clinical outcomes, and complications after surgery in both groups., Results: At the 6- and 12-month follow-up points, similar fusion rates were observed in both groups (p=.81 and 0.61, respectively). According to the clinical outcome, CS provided similar improvements in pain amelioration and functional status compared to PS, with no significant differences. Additionally, CS resulted in significantly less surgical morbidity, including shorter incision length, quicker operative time, and less blood loss, compared to PS., Conclusions: CS in PLIF provides similar clinical and radiologic outcomes compared to PS in PLIF. On the basis of the present study, we suggest CS to be a reasonable alternative to PS in PLIF., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Background Context: Anterior transarticular screw (ATAS) fixation has been suggested as a viable alternative to posterior stabilization. However, we are not aware of previous reports attempting to establish the usefulness of specific fluoroscopic landmark-guided trajectories in the use of ATAS, and we could find no reference to it in a computerized search using MEDLINE., Purpose: To determine the anatomic feasibility of ATAS placement using defined fluoroscopic landmarks to guide screw trajectory., Study Design: Evaluation using three-dimensional screw insertion simulation software and 1.0-mm-interval computed tomographic scans., Patient Sample: Computed tomographic scans of 100 patients including 50 men and 50 women., Outcome Measures: Incidence of violation of the vertebral artery groove of C1 and C2, the spinal canal, and the atlanto-occipital joint and screw lengths and lengths of C1 and C2 purchase., Methods: Four screw trajectories were determined: promontory screw (PS), single central facet (CF) screw, and medial (MF) and lateral (LF) double facet screws. Placement of a 4.0-mm screw was simulated using defined fluoroscopic landmarks for each trajectory. The previously mentioned outcome measures were evaluated and compared for the four trajectories. This study was not supported by any financial sources, and there is no topic-specific potential conflict of interest with this study., Results: No violation of the C1 or C2 vertebral artery groove or of the spinal canal was observed for any of the screw types. Screw lengths and the length of C2 purchase were by far the longest for PS (40.4±2.8 and 25.7±2.1 mm, respectively; p<.001 in all post hoc comparisons). The length of C1 purchase was longer for CF (16.4±2.3 mm) and LF (15.8±1.6 mm) than PS (14.7±2.0 mm) and MF (14.6±2.4 mm) (p≤.001, respectively). There was no atlanto-occipital joint violation if the length of C1 purchase was set at 12 mm for CF and LF and at 10 mm for PS and MF., Conclusions: Our results suggest that it may be possible to place ATASs without violating the vertebral artery groove, spinal canal, or the atlanto-occipital joint by using the described entry points, trajectories, and fluoroscopic landmarks., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Object: The authors introduce a simple technique and tool to facilitate reduction of atlantoaxial subluxation during posterior segmental screw fixation., Methods: Two types of reduction tool have been designed: T-type and L-type. A T-shaped levering tool was used when a pedicle or pars screw was used for C-2, and an L-shaped tool was used when a laminar screw was used for C-2. Twenty-two patients who underwent atlantoaxial segmental screw fixation and fusion for the treatment of anteroposterior instability or subluxation, using either of these new types of reduction tool, were enrolled. Demographic, clinical, and surgical data, which had been prospectively collected in a database, were analyzed. The atlantodens interval was measured on lateral radiographs, and the space available for the spinal cord was measured on CT scans., Results: The authors could attain reduction of the atlantoaxial subluxation without difficulty using either type of tool. The preoperative atlantodens interval ranged from -16.9 to 10.9 mm in a neutral position, and the postoperative interval ranged from -2.8 to 3.0 mm, with negative values due to extension-type or mixed-type instability. The mean space available for the spinal cord significantly increased, from 9.5 mm preoperatively to 15.4 mm postoperatively (p < 0.001)., Conclusions: This technique allowed for controlled manipulation and reduction of the atlantoaxial subluxation without difficulty.

Background Context: To our knowledge, no large series comparing the risk of vertebral artery injury by C1-C2 transarticular screw versus C2 pedicle screw have been published. In addition, no comparative studies have been performed on those with a high-riding vertebral artery and/or a narrow pedicle who are thought to be at higher risk than those with normal anatomy., Purpose: To compare the risk of vertebral artery injury by C1-C2 transarticular screw versus C2 pedicle screw in an overall patient population and subsets of patients with a high-riding vertebral artery and a narrow pedicle using computed tomography (CT) scan images and three-dimensional (3D) screw trajectory software., Study Design: Radiographic analysis using CT scans., Patient Sample: Computed tomography scans of 269 consecutive patients, for a total of 538 potential screw insertion sites for each type of screw., Outcome Measures: Cortical perforation into the vertebral artery groove of C2 by a screw., Methods: We simulated the placement of 4.0 mm transarticular and pedicle screws using 1-mm-sliced CT scans and 3D screw trajectory software. We then compared the frequency of C2 vertebral artery groove violation by the two different fixation methods. This was done in the overall patient population, in the subset of those with a high-riding vertebral artery (defined as an isthmus height ≤ 5 mm or internal height ≤ 2 mm on sagittal images) and with a narrow pedicle (defined as a pedicle width ≤ 4 mm on axial images)., Results: There were 78 high-riding vertebral arteries (14.5%) and 51 narrow pedicles (9.5%). Most (82%) of the narrow pedicles had a concurrent high-riding vertebral artery, whereas only 54% of the high-riding vertebral arteries had a concurrent narrow pedicle. Overall, 9.5% of transarticular and 8.0% of pedicle screws violated the C2 vertebral artery groove without a significant difference between the two types of screws (p=.17). Among those with a high-riding vertebral artery, vertebral artery groove violation was significantly lower (p=.02) with pedicle (49%) than with transarticular (63%) screws. Among those with a narrow pedicle, vertebral artery groove violation was high in both groups (71% with transarticular and 76% with pedicle screws) but without a significant difference between the two groups (p=.55)., Conclusions: Overall, neither technique has more inherent anatomic risk of vertebral artery injury. However, in the presence of a high-riding vertebral artery, placement of a pedicle screw is significantly safer than the placement of a transarticular screw. Narrow pedicles, which might be anticipated to lead to higher risk for a pedicle screw than a transarticular screw, did not result in a significant difference because most patients (82%) with narrow pedicles had a concurrent high-riding vertebral artery that also increased the risk with a transarticular screw. Except in case of a high-riding vertebral artery, our results suggest that the surgeon can opt for either technique and expect similar anatomic risks of vertebral artery injury., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Background Context: Although routine transection of the C2 nerve root during atlantoaxial segmental screw fixation has been recommended by some surgeons, it remains controversial and to our knowledge no comparative studies have been performed to determine whether transection or preservation of the C2 nerve root affects patient-derived sensory outcomes., Purpose: The purpose of this study is to specifically analyze patient-derived sensory outcomes over time in patients with intentional C2 nerve root transection during atlantoaxial segmental screw fixation compared with those without transection., Study Design: This is a post-hoc comparative analysis of prospectively collected patient-derived outcome data., Patient Sample: The sample consists of 24 consecutive patients who underwent intentional bilateral transection of the C2 nerve root during posterior atlantoaxial segmental screw fixation (transection group) and subsequent 41 consecutive patients without transection (preservation group)., Outcome Measures: A visual analog scale (VAS) score was used for occipital neuralgia as the primary outcome measure and VAS score for neck pain, neck disability index score and Japanese Orthopedic Association score for cervical myelopathy and recovery rate, with bone union rate as the secondary outcome measure., Methods: Patient-derived outcomes including change in VAS score for occipital neuralgia over time were statistically compared between the two groups. This study was not supported by any financial sources and there is no topic-specific conflict of interest related to the authors of this study., Results: Seven (29%) of the 24 patients in the transection group experienced increased neuralgic pain at 1 month after surgery either because of newly developed occipital neuralgia or aggravation of preexisting occipital neuralgia. Four of the seven patients required almost daily medication even at the final follow-up (44 and 80 months). On the other hand, only four (10%) of 41 patients in the preservation group had increased neuralgic pain at 1 month after surgery, and at ≥ 1 year, no patients had increased neuralgic pain. The difference in the prevalence of increased neuralgic pain between the two groups was statistically significant at all time points (3, 6, 12, and 24 months postoperatively) except at 1 month postoperatively. The intensity of neuralgic pain, which preoperatively had not been significantly different between the two groups, was significantly higher in the transection group at the final follow-up., Conclusions: C2 nerve root transection is not a benign procedure and, in our experience, more than a quarter of the patients experience increased neuralgic pain following C2 nerve root transection. Because the prevalence and intensity of postoperative neuralgia was significantly higher with C2 nerve root transection than with its preservation, we recommend against routine C2 nerve root transection when performing atlantoaxial segmental screw fixation., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Study Design: Evaluation using 3-dimensional screw trajectory software and computed tomographic scans., Objective: To investigate the anatomic feasibility of laminar screw placement in the upper thoracic spine compared with pedicle screw placement., Summary of Background Data: Although laminar screws have been suggested as an alternative to pedicle screws in the upper thoracic spine, previous anatomic feasibility studies have some limitations., Methods: Four types of screws were simulated from T1 to T6: unilaminar screw (US), superior bilaminar screw (SBS), inferior bilaminar screw (IBS), and pedicle screw (PS). Maximum allowable screw dimensions and the success rates of 4.5-mm screw placement were compared for each level. Laminar screw dimensions with more than 90% success rate at each level were determined for reference., Results: Computed tomographic scans of 132 patients were analyzed. Laminar screw diameters gradually increased from T1 (4.4-5.4 mm, for each type) to T6 (4.8-6.7 mm), whereas PS diameter steeply declined from T1 (5.9 mm) to T4 (3.4 mm) and then leveled off. At T1, PS had greater success rate of 4.5-mm screw placement than laminar screws (US > IBS > SBS); at T2, US had greater success rate than IBS, followed by PS and SBS; and at T3 to T6, laminar screws (US > IBS > SBS) had greater success rate than PS in all comparisons. Except for SBS at T1, laminar screw diameters with more than 90% success rates were between 3.5 and 5.0 mm., Conclusion: In view of their anatomic feasibility, laminar screws can be a viable alternative to PSs in the upper thoracic spine. Particularly at T3 to T6 where the pedicle width is inherently small, the success rates of laminar screw placement were significantly and consistently higher than those of PS placement. The comparable success rates of laminar screws using commercially available screw sizes further emphasize their potential clinical use.

Background Context: There have been several reports describing the usage of subaxial cervical laminar screws. However, the anatomic feasibility of placing such screws has not been thoroughly evaluated yet., Purpose: To determine the feasibility of the laminar screw placement in the subaxial cervical spine using a large number of computed tomography (CT) scans and three-dimensional screw trajectory software., Study Design: Three-dimensional simulation study of screw placement., Patient Sample: Computed tomography scans of 215 consecutive patients were examined, for a total of 430 screws at each level of the subaxial cervical spine., Outcome Measures: Successful screw placement without laminar cortical breach, facet joint violation, and collision between two screws in the same level., Methods: We simulated the placement of 4.0-mm subaxial (C3-C7) cervical laminar screws. Unilateral and bilateral screw placement was simulated, and their success rates were evaluated at each level of the subaxial cervical spine. This study was not supported by any financial sources. One of the authors received royalties for a posterior cervical fixation system, which is not the topic of this article and is not used or mentioned in this article., Results: The success rate of unilateral screw placement was the highest at C7 (91.4%), followed by C6 (31.9%), C3 (30.2%), C4 (6.3%), and C5 (4.0%). It was significantly higher (p<.001) in men than in women at C6 and C7 but not at the other levels. The success rate of bilateral screw placement was the highest at C7 (68.8%), followed by C3 (13.5%), C6 (8.8%), C4 (1.9%), and C5 (0.9%). It was significantly higher in men (83.5%) than in women (52.0%) at C7 (p<.001) but not at the other levels., Conclusions: The relatively high success rate at C7, particularly of unilateral placement, suggests that laminar screw placement can be a sound alternative method for fixation at this level. However, careful preoperative CT scan evaluation and patient selection are required, particularly for bilateral fixation in women. At C3 and C6, unilateral screw placement can be considered in approximately 30% of patients after careful selection using preoperative CT scans. At C4 and C5, neither unilateral nor bilateral screw fixation is recommended for most patients., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background Context: To our knowledge, there is no clinical study analyzing the feasibility and complications of the routine insertion of the lateral mass screw via the posterior arch for C1 fixation in a live surgical setting., Purpose: To evaluate the feasibility of routine insertion of the lateral mass screw via the posterior arch and related complications., Study Design: Prospective clinical-radiological analysis., Patient Sample: Fifty-two consecutive patients with 102 C1 lateral mass screws inserted via the posterior arch., Outcome Measures: Cortical perforation, vertebral artery injuries, and visual analog scale score of occipital neuralgia recorded on a prospective database., Methods: All consecutive patients in whom lateral mass screw placement via the posterior arch was attempted as the first choice whenever C1 posterior fixation was necessary were enrolled. Prospective database, clinical records, questionnaires regarding occipital neuralgia, pre- and postoperative computed tomography (CT) angiograms, and follow-up radiographs and CT scans were analyzed. This study was supported by a $9,000 academic research grant by the first author's hospital. The last author receives royalties for a posterior cervical fixation system, which is not the topic of this study and is not used or mentioned in this article., Results: One hundred two screws were attempted in 52 consecutive patients by a single surgeon. The height of 43 posterior arches (42%) was smaller than 4 mm on preoperative CT angiography. Lateral mass screws could be inserted via the posterior arch in all cases including eight with nine ponticuli posticus and seven with seven persistent first intersegmental arteries, but the posterior arch was perforated cranially by 7, caudally by 30, and craniocaudally (partially) by 3 screws and vertically split by 14 screws. Among the last 28 screws for which the authors' overdrilling technique was used, only one vertical split occurred, whereas among the first 74 screws without overdrilling, 13 vertical splits occurred. None of them led to screw loosening or nonunion. There were no vertebral artery injuries. Among the 19 patients with preoperative occipital neuralgia, 12 had complete resolution and seven had alleviation at the last follow-up. Among the 33 patients without preoperative neuralgia, seven developed new neuralgia postoperatively. Three of them underwent C2 root transection and the other four underwent C2 root dissection for intraarticular fusion of the facet joints. Of the seven, five had complete resolution and two had mild discomfort at the last follow-up., Conclusions: Routine insertion of the lateral mass screw via the C1 posterior arch was feasible in even those with a small posterior arch, ponticulus posticus, or persistent first intersegmental artery. Although cortical perforation or vertical splitting of the posterior arch was often inevitable, it did not lead to significant weakening of the fixation or nonunion. Vertical split could be minimized by overdrilling the posterior arch. Vertebral artery injury was preventable by mobilization before screw insertion. Occipital neuralgia was not uncommon but thought to be unrelated to screw placement in most cases., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Study Design: Evaluation by simulation of screw insertion using fine-cut computed tomographic (CT) scans and screw trajectory software., Objective: To evaluate the feasibility and optimal trajectory of the occipital condylar screw., Summary of Background Data: To the best of our knowledge, no large series examining the feasibility and optimal trajectory of occipital condylar screws have been published., Methods: We simulated unicortical placement of a 4 × 18-mm screw using 1-mm sliced CT scans and 3-dimensional screw trajectory software in 314 occipital condyles of 157 patients. With the screw tip directed toward a point just below the tip of the basion on lateral fluoroscopy, 3 entry points were compared in view of success rate of screw placement, safe range of medial angulation in an axial plane, and maximum screw length., Results: The lateral entry point had the highest success rate (93.0%) of screw placement, mean safe range of the medial angulation (10.9°), and maximum screw length (20.7 mm), followed by the middle (92.0%, 10.8°, and 20.6 mm, respectively) and medial (74.2%, 7.7°, and 19.7 mm, respectively) entry points. While the lateral and the middle entry points did not have any statistically significant difference in the 3 parameters, they were significantly better than the medial entry point. All 3 entry points had highly variable ranges of safe medial angulation, making it difficult to provide a single recommended value., Conclusion: Screw placement is feasible in up to 93% of the occipital condyles. The lateral and the middle entry points are significantly better than the medial entry point. Selection between the middle and the lateral entry points should be individualized taking into account local anatomic variation. Because the medial angulation of these screws is highly variable, preoperative 3-dimensional CT evaluation and possibly even intraoperative navigation may be required.

Object: The aim of this study was to evaluate after more than 5 years the outcome of surgical treatment for flexible idiopathic scoliosis using skipped pedicle screw fixation., Methods: For patients with spine curves < 90° and flexibility > 20%, pedicle screws had been inserted into every other segment on the corrective side and 2-4 screws per curve had been inserted on the supportive side. The authors analyzed the results in 57 patients, including the correction rate of coronal curvature and rotational deformity, correction loss, sagittal balance, complications, blood loss, operation time, and implant costs., Results: The mean Cobb angle was 54° preoperatively and 17° immediately after surgery (69% correction). At the last follow-up, the mean Cobb angle was 18° (2% correction loss). Rotation of the apical vertebra was corrected by 50% on average and showed only a 6% correction loss at the last follow-up. None of the patients had problems in maintaining sagittal balance. An adding-on phenomenon was detected in 4 patients (7%). Twelve of 14 patients with coronal decompensation showed improvement after surgery, whereas postoperative decompensation developed in 3 patients. Four patients had implant failures, and 4 had postoperative infections. The mean blood loss during surgery was 832 ml, and the mean operation time was 167 minutes. Compared with conventional methods, the authors' method used up to 48% fewer screws., Conclusions: Skipped pedicle screw fixation of flexible idiopathic scoliosis showed satisfactory results. This method has several advantages, including reduced blood loss, shorter operation time, and reduced cost.

Background Context: Injury to the internal carotid artery (ICA) is a potentially catastrophic complication of C1-lateral mass (C1-LM) or C1-C2 transarticular screw insertion., Purpose: This study was designed to determine the risk of injury to the ICA during placement of these screws using computed tomography angiography (CTA)., Study Design: Radiographic analysis using CTA., Patient Sample: One hundred sixty CTAs were examined, for a total of 320 ICAs., Outcome Measures: Not applicable., Methods: Fine-cut intravenous CTAs with multiplanar and three-dimensional reconstruction were reviewed. The position of the ICA in relation to the anterior cortex (AC) of C1, anterior end of the anterior tubercle (AT), and medial margin of the transverse foramen (TF) was measured bilaterally in three ascending and equidistant levels of the C1-AT., Results: The position of the ICA in relation to C1 was variable. The average distance between the ICA and the AC of C1 was only 3.7 mm. Furthermore, 96% of the time the posterior margin of the ICA was located posterior to the anteriormost aspect of the anterior C1 tubercle (average distance, 5.4 mm), making the ICA vulnerable to damage if a drill, tap, or screw was inserted to the depth of the anteriormost portion of the AT as seen on a lateral fluoroscopic or radiographic view. The medial margin of the ICA was located medial to the TF (a location potentially vulnerable to injury with bicortical screw placement) less often at the caudal aspect of the C1-AT (54%) than at its middle or cranial aspect (74% and 75%, respectively). No ICAs were located anterior to the medial 30% of the C1-LM or more medially., Conclusions: Bicortical C1-LM or C1-C2 transarticular screw placement carries a potential risk of ICA injury. Given the wide variation in ICA location relative to C1, if bicortical C1 fixation is required, preoperative CTA should be considered to determine the optimal screw trajectory. In general, inferomedially angulated C1-LM screws appear to be safer with respect to the ICA injury than other potential trajectories., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Study Design: Radiologic evaluation of computed tomography (CT) scans using screw insertion simulation software., Objective: To investigate the optimal entry point and trajectory of atlantooccipital transarticular screws., Summary of Background Data: To our knowledge, no large series focusing on the placement of atlantooccipital transarticular screws have been published., Methods: We used 1.0-mm sliced CT scans and 3-dimensional screw trajectory software to simulate 4.0-mm screw placement. Four entry points were evaluated. Screw placement success rate, safe range of medial angulation, and screw length using each entry point were determined., Results: CT scans of 126 patients were evaluated, for a total of 252 screws for each entry point. On simulation, the 2 lateral entry points showed significantly higher success rates and safe range of medial angulation than the 2 middle points. The 2 lateral entry points had similar success rates (98.0% for anteriolateral (AL) point and 97.6% for posteriolateral (PL) point). Although the safe range of medial angulation was significantly wider for the AL point (26.1 degrees) than for the PL point (23.7 degrees), the screw lengths were significantly longer for the PL point (32.6 mm) than for the AL point (29.4 mm). For both points, 30 degrees of medial angulation led to highest rate of successful screw placement, but the rate was only 79.4% and 80.2%, respectively., Conclusion: Although there was no significant difference in success rates between AL and PL points, PL is likely the best entry point. Although 30 degrees medial and approximately 5 degrees upward angulation led to the highest rate of successful screw placement, the rate was only around 80%. Given the wide individual variation, we recommend that a preoperative 3-dimensional CT scan be obtained when attempting atlantooccipital transarticular screw fixation.

Background Context: Inadvertent perforation of the C0-C1 and C1-C2 joints is one of the potential complications of C1 screw insertion., Purpose: To identify a simple lateral fluoroscopic landmark to help prevent atlantooccipital (C0-C1) and atlantoaxial (C1-C2) joint violations during C1 lateral mass screw insertion., Study Design: Screw insertion simulation using computed tomography (CT)., Patient Sample: Cervical spine 1.0-mm interval CT scans of 154 patients performed at a single institution between October 2004 and October 2005 were analyzed., Outcome Measures: C0-C1 and C1-C2 joint violations during CT-based simulation of C1 lateral mass screw placement., Methods: Fine cut CT scans and screw trajectory software was used to simulate insertion of 4.0mm screws. The entry point was the middle of the junction of the posterior arch and the posterior inferior part of the lateral mass. Zero and fifteen degrees medially angulated trajectories were evaluated. For both, we determined the maximum cranial and caudal angulation that avoided joint violation, and where the screw could safely be directed in the C1 anterior arch on a lateral view using these angulations. We expressed these targeting points as a percentage of the total height of the anterior atlas arch such that 100% represented the cranial border of the arch, 50% the center and 0% the caudal border., Results: Screw trajectories in 154 patients (308 screws) were evaluated. Using the 15 degrees medial angulation, the C0-C1 joint was safe in all cases when the trajectory was below the 40% point of the anterior arch. The C1-C2 joint was safe when the trajectory was above the 20% point. Using the 0 degrees angulation, safety margin was slightly wider. Because it may be difficult to differentiate between 0 degrees and 15 degrees of medial angulation intraoperatively, we suggest aiming the screw tip between the 20% and 40% points for either trajectory. We call this the "safe zone of C1.", Conclusions: When the screw is directed between 0 degrees and 15 degrees medially, it can be inserted without C0-C1 and C1-C2 joint violation if the screw tip trajectory lies between the 20% and 40% points of the anterior atlas arch.

Study Design: Prospective consecutive case series., Objective: To identify the incidence of undetected vertebral artery groove and foramen violations and arterial injuries during placement of C1 lateral mass and C2 pedicle screws., Summary of Background Data: Although insertion of C1 lateral mass and C2 pedicle screws has become increasingly common, we are unaware of any report that has specifically examined postoperative CT scans with CT angiography to determine the incidence of undetected neurovascular violations during insertion of these screws., Methods: Twenty-three consecutive patients were examined after upper cervical screw fixation was performed under fluoroscopic guidance. In all patients, intraoperative clinical findings, fluoroscopic images, and postoperative radiographs were reviewed. Thin-cut CT scans and CT angiography with multiplanar and three-dimensional reconstruction were used to detect cortical breaches and arterial injuries., Results: A total of 85 screws, including 39 C1 lateral mass, 39 C2 pedicle, and 7 C2 laminar screws were inserted. No apparent neurologic or arterial injuries were noted. However, CT scans revealed that 8 C2 pedicle screws (21%) resulted in vertebral artery groove violations. None resulted in arterial injury. Two C1 screws (5%) had errant trajectories. One breached the medial wall of the lateral mass and the other breached the vertebral artery foramen, causing arterial occlusion as seen on CT angiography. None of the violations were detected intraoperatively or on postoperative plain radiographs with the exception of 1 C1 medial breach observed on a postoperative open-mouth view., Conclusion: Although vertebral artery groove and foramen violations were relatively common on postoperative CT scans, none were detected intraoperatively or on postoperative radiographs. Most alarmingly, 1 vertebral artery injury was undetected intraoperatively. Since a vertebral injury can be potentially catastrophic, this study emphasizes the inherent dangers associated with placement of C1 and C2 screws and underscores the importance of careful postoperative evaluation and surgical technique when inserting these screws.

Study Design: Prospective observational cohort study.Objective: To compare the outcomes of our new technique, distraction arthrodesis of C1-C2 facet joint with C2 root preservation (Study group), to those of conventional C1-C2 fusion with C2 root transection (Control group) for the management of intractable occipital neuralgia caused by C2 root compression.Summary Of Background Data: We are not aware of any report concerning C2 root decompression during C1-C2 fusion.Materials and Methods: Inclusion criteria were visual analogue scale (VAS) score for occipital neuralgia 7 or more; C2 root compression at the collapsed C1-C2 neural foramen; and follow-up 12 months or more. The Study group underwent surgery with our new technique including (1) C1-C2 facet joint distraction and bone block insertion while preserving the C2 root; and (2) use of C1 posterior arch screws instead of conventional lateral mass screws during C1-C2 segmental screw fixation. The Control group underwent C2 root transection with C1-C2 segmental screw fixation and fusion. We compared the prospectively collected outcomes data.Results: There were 15 patients in the Study group and 8 in the Control group. Although there was no significant difference in the VAS score for the occipital neuralgia between the 2 groups preoperatively (8.2 ± 0.9 vs. 7.9 ± 0.6, P = 0.39), it was significantly lower in the Study group at 1, 3, and 6 months postoperatively (P < 0.01, respectively). At 12 months, it was 0.4 ± 0.6 versus 2.5 ± 2.6 (P = 0.01). There was no significant difference in improvement in the VAS score for neck pain and neck disability index and Japanese Orthopedic Association recovery rate, which are minimally influenced by occipital neuralgia.Conclusion: Our novel technique of distraction arthrodesis with C2 root preservation can be an effective option for the management of intractable occipital neuralgia caused by C2 root compression. [ABSTRACT FROM AUTHOR]

Background Context: There have been conflicting results on the surgical outcome of lumbar fusion surgery using two different techniques: robot-assisted pedicle screw fixation and conventional freehand technique. In addition, there have been no studies about the biomechanical issues between both techniques.Purpose: This study aimed to investigate the biomechanical properties in terms of stress at adjacent segments using robot-assisted pedicle screw insertion technique (robot-assisted, minimally invasive posterior lumbar interbody fusion, Rom-PLIF) and freehand technique (conventional, freehand, open approach, posterior lumbar interbody fusion, Cop-PLIF) for instrumented lumbar fusion surgery.Study Design: This is an additional post-hoc analysis for patient-specific finite element (FE) model.Patient Sample: The sample is composed of patients with degenerative lumbar disease.Outcome Measures: Intradiscal pressure and facet contact force are the outcome measures.Methods: Patients were randomly assigned to undergo an instrumented PLIF procedure using a Rom-PLIF (37 patients) or a Cop-PLIF (41), respectively. Five patients in each group were selected using a simple random sampling method after operation, and 10 preoperative and postoperative lumbar spines were modeled from preoperative high-resolution computed tomography of 10 patients using the same method for a validated lumbar spine model. Under four pure moments of 7.5 Nm, the changes in intradiscal pressure and facet joint contact force at the proximal adjacent segment following fusion surgery were analyzed and compared with preoperative states.Results: The representativeness of random samples was verified. Both groups showed significant increases in postoperative intradiscal pressure at the proximal adjacent segment under four moments, compared with the preoperative state. The Cop-PLIF models demonstrated significantly higher percent increments of intradiscal pressure at proximal adjacent segments under extension, lateral bending, and torsion moments than the Rom-PLIF models (p=.032, p=.008, and p=.016, respectively). Furthermore, the percent increment of facet contact force was significantly higher in the Cop-PLIF models under extension and torsion moments than in the Rom-PLIF models (p=.016 under both extension and torsion moments).Conclusions: The present study showed the clinical application of subject-specific FE analysis in the spine. Even though there was biomechanical superiority of the robot-assisted insertions in terms of alleviation of stress increments at adjacent segments after fusion, cautious interpretation is needed because of the small sample size. [ABSTRACT FROM AUTHOR]

STUDY DESIGN: Prospective randomized controlled trial. OBJECTIVE: The aim of this study was to monitor the quality control of robot-assisted pedicle screw fixation accuracy by using a cumulative summation (CUSUM) test at the initial stage of its application. SUMMARY OF BACKGROUND DATA: Although robot-assisted pedicle screw fixation reduces screw misplacement rates and provides critical support for minimally invasive surgical procedures, there have been no reports relating to the monitoring of quality control of the accuracy of this robot-assisted pedicle screw fixation procedure. METHODS: Patients with lumbar spinal stenosis scheduled to undergo surgery were randomly and equally assigned through 1:1 allocation to a robot-assisted minimally invasive posterior lumbar interbody fusion (Rom-PLIF) group or a conventional open posterior PLIF using freehand technique group. The accuracy of pedicle screw placement was evaluated using postoperative computed tomography. The primary outcome was the CUSUM analysis for monitoring the quality control of the accuracy of pedicle screw insertion between the Rom-PLIF and conventional open posterior PLIF using freehand technique groups. RESULTS: Of the 80 pedicle screws inserted in each group, 4 screws in the Rom-PLIF group, and 7 in the conventional open PLIF group, breached the pedicle. Of these 11 offending screws, 4 cases were categorized as grade B in the Rom-PLIF group, whereas 6 were grade B and 1 case was grade C in the Com-PLIF group, using the Gertzbein and Robbins classification. Throughout the monitoring period, there was no CUSUM test-derived indication that the quality of performance of the pedicle screw fixation procedure was inadequate in either group. CONCLUSION: First, this study demonstrates the adequacy of quality control of robot-assisted pedicle screw fixation even early in the application period based on the CUSUM analysis. Second, the CUSUM test can be a useful tool for monitoring of the quality of procedures related with spine surgery. [ABSTRACT FROM AUTHOR]