Aims. Anchorage of pedicle screw rod instrumentation in the elderly spine with poor bone quality remains challenging. Our study aims to evaluate how the screw bone anchorage is affected by screw design, bone quality, loading conditions, and cementing techniques. Methods. Micro-finite element (µFE) models were created from micro-CT (μCT) scans of vertebrae implanted with two types of pedicle screws (L: Ennovate and R: S. 4. ). Simulations were conducted for a 10 mm radius region of interest (ROI) around each screw and for a full vertebra (FV) where different cementing scenarios were simulated around the screw tips. Stiffness was calculated in pull-out and anterior bending loads. Results. Experimental pull-out strengths were excellently correlated to the µFE pull-out stiffness of the ROI (R. 2. > 0.87) and FV (R. 2. > 0.84) models. No significant difference due to screw design was observed. Cement augmentation increased pull-out stiffness by up to 94% and 48% for L and R screws, respectively, but only increased bending stiffness by up to 6.9% and 1.5%, respectively. Cementing involving only one screw tip resulted in lower stiffness increases in all tested screw designs and loading cases. The stiffening effect of cement augmentation on pull-out and bending stiffness was strongly and negatively correlated to local bone density around the screw (correlation coefficient (R) = -0.95). Conclusion. This combined experimental, µCT and µFE study showed that regional analyses may be sufficient to predict fixation strength in pull-out and that full analyses could show that cement augmentation around pedicle screws increased fixation stiffness in both pull-out and bending, especially for low-density bone. Cite this article: Bone Joint Res 2021;10(12):797–806

Aims. The aim of this study was to systematically compare the safety and accuracy of robot-assisted (RA) technique with conventional freehand with/without fluoroscopy-assisted (CT) pedicle screw insertion for spine disease. Methods. A systematic search was performed on PubMed, EMBASE, the Cochrane Library, MEDLINE, China National Knowledge Infrastructure (CNKI), and WANFANG for randomized controlled trials (RCTs) that investigated the safety and accuracy of RA compared with conventional freehand with/without fluoroscopy-assisted pedicle screw insertion for spine disease from 2012 to 2019. This meta-analysis used Mantel-Haenszel or inverse variance method with mixed-effects model for heterogeneity, calculating the odds ratio (OR), mean difference (MD), standardized mean difference (SMD), and 95% confidence intervals (CIs). The results of heterogeneity, subgroup analysis, and risk of bias were analyzed. Results. Ten RCTs with 713 patients and 3,331 pedicle screws were included. Compared with CT, the accuracy rate of RA was superior in Grade A with statistical significance and Grade A + B without statistical significance. Compared with CT, the operating time of RA was longer. The difference between RA and CT was statistically significant in radiation dose. Proximal facet joint violation occurred less in RA than in CT. The postoperative Oswestry Disability Index (ODI) of RA was smaller than that of CT, and there were some interesting outcomes in our subgroup analysis. Conclusion. RA technique could be viewed as an accurate and safe pedicle screw implantation method compared to CT. A robotic system equipped with optical intraoperative navigation is superior to CT in accuracy. RA pedicle screw insertion can improve accuracy and maintain stability for some challenging areas. Cite this article: Bone Joint Res 2020;9(10):653–666

INTRODUCTION. The correct placement of pedicle screws is a major part of spine fusion and it requires experienced trained spinal surgeons. In the era of European Working Time Directive (EWTD), surgical trainees have less opportunity to acquire skills. Josh Kauffman (Author of The First 20 Hours) examined the K. Anders-Ericsson study that 10,000 hours is required to be an expert. He suggests you can be good at anything in 20 hours following 5 methods. This study was done to show the use of accelerated learning in trainees to achieve competency and confidence on the insertion of pedicle screws. METHODS. Data was collected using 3 experienced spine surgeons, 8 trainees and 1 novice (control) on the cadaveric insertion of pedicle screws over a 4 day didactic lecture in the cadaver lab. Each candidate had 2 cadavers and 156 screw placements over 4 hour shifts. Data was collected for time of pedicle screw insertion for each level on the left and right side. A pre-course and post-course questionnaire (Likert scale) was conducted. RESULTS. There were 8 candidates (surgeons) involved. 1 spinal SpR, 6 spine fellows and 1 junior consultant. A physiotherapist was the control novice. The surgeons and the control got significantly faster over time. The control made significantly more errors than the surgeons. Surgeons were significantly faster by the end (p value < 0.05). The control got faster over time and by the end, was no longer significantly slower than the surgeon when they first started. CONCLUSION. Pedicle screw insertion can cause significant morbidity, which includes paralysis. As a trainee, this is not an easy skill to acquire or practice. This focused pedicle screw course shows that a junior spinal surgeon can achieve improved competency and confidence in 20 hours but furthermore a complete novice can learn to insert pedicle screws and reach a level of competence almost at the level of the trainee in 20 hours as well

Objectives. Cement augmentation of pedicle screws could be used to improve screw stability, especially in osteoporotic vertebrae. However, little is known concerning the influence of different screw types and amount of cement applied. Therefore, the aim of this biomechanical in vitro study was to evaluate the effect of cement augmentation on the screw pull-out force in osteoporotic vertebrae, comparing different pedicle screws (solid and fenestrated) and cement volumes (0 mL, 1 mL or 3 mL). Materials and Methods. A total of 54 osteoporotic human cadaver thoracic and lumbar vertebrae were instrumented with pedicle screws (uncemented, solid cemented or fenestrated cemented) and augmented with high-viscosity PMMA cement (0 mL, 1 mL or 3 mL). The insertion torque and bone mineral density were determined. Radiographs and CT scans were undertaken to evaluate cement distribution and cement leakage. Pull-out testing was performed with a material testing machine to measure failure load and stiffness. The paired t-test was used to compare the two screws within each vertebra. Results. Mean failure load was significantly greater for fenestrated cemented screws (+622 N; p ⩽ 0.001) and solid cemented screws (+460 N; p ⩽ 0.001) than for uncemented screws. There was no significant difference between the solid and fenestrated cemented screws (p = 0.5). In the lower thoracic vertebrae, 1 mL cement was enough to significantly increase failure load, while 3 mL led to further significant improvement in the upper thoracic, lower thoracic and lumbar regions. Conclusion. Conventional, solid pedicle screws augmented with high-viscosity cement provided comparable screw stability in pull-out testing to that of sophisticated and more expensive fenestrated screws. In terms of cement volume, we recommend the use of at least 1 mL in the thoracic and 3 mL in the lumbar spine. Cite this article: C. I. Leichtle, A. Lorenz, S. Rothstock, J. Happel, F. Walter, T. Shiozawa, U. G. Leichtle. Pull-out strength of cemented solid versus fenestrated pedicle screws in osteoporotic vertebrae. Bone Joint Res 2016;5:419–426

Objectives. This presentation discusses the experience at our Centre with treating traumatic thoracolumbar fractures using percutaneous pedicle screw fixation and also looks at clinical and radiological outcomes as well as complications. Design. This is a retrospective study reviewing all cases performed between Jan 2013 and June 2019. Subjects. In our study there were 257 patients in total, of which there were 123 males and 134 females aged between 17 and 70. Methods. We reviewed the case notes and imaging retrospectively to obtain the relevant data. Results. A total of 257 patients were included, 123 males and 134 females; the mean age was 47.6 years. The majority of injuries were from fall from significant height. In 98 cases the fracture involved a thoracic vertebra and in 159 cases a lumbar vertebra. Percutaneous pedicle screw fixation was performed either one level above and below fracture or Two levels above and below the fracture depending upon the level of injury. Forty two cases were treated with additional short pedicle screws at the level of fracture. More than 15% (39) of patients presented with a neurological deficit on admission and more than 80% (32) of those showed post-operative improvement in their neurology as per Frankel Grading system. The mean Operative time was 117minutes +− 45, and mean length of hospital stay was 7.2 +− 3.8 days, with significant improvement in Visual analogue score. Percutaneous fixation achieved a satisfactory improvement in radiological parameters including sagittal Cobb angle (SCA) post-operatively in all patients. The vast majority of patients achieved a good functional outcome according to modified Macnab criteria. Follow up was for a maximum of two years, with relevant imaging at each stage. Ten (3.8%) patients had wound infection with three patients requiring wound debridement. Four patients had upper level screws pulled out and in Four cases one screw was misplaced. All eight had revision surgery. Conclusions. Percutaneous pedicle screw fixation is a safe surgical option with comparable outcomes to open surgery and a potential reduction in perioperative morbidity. Percutaneous pedicle screw fixation is the primary surgical technique to treat traumatic thoracolumbar fractures at our Centre. There were no major complications in our series, with good functional outcome following surgery

Study design. Literature review of the best available evidence on the accuracy of computer assisted pedicle screw insertion. Background. Pedicle screw misplacement rates with the conventional insertion technique and adequate postoperative CT examination have ranged from 5 to 29 % in the cervical spine, from 3 to 58 % in the thoracic spine, and from 6 to 41% in the lumbosacral region. Despite these relatively high perforation rates, the incidence of reported screw-related complications has remained low. Interestingly, the highest rates of neurovascular injuries have been reported from the lumbosacral spine in up to 17% of the patients. Gertzbein and Robbins introduced a 4-mm “safe zone” in the thoracolumbar spine for medial encroachment, consisting of 2-mm of epidural and 2-mm of subarachnoid space. Later, several authors have found the safety margins to be significantly smaller, suggesting that the “safe zone” thresholds of Gertzbein and Robbins do not apply to the thoracic spine, and seem to be too high even for the lumbar spine. The midthoracic and midcervical spine, as well as the thoracolumbar junction set the highest demands for accuracy in pedicle screw insertion, with no room for either translational or rotational error at e.g. T5 level. Computer assisted pedicle screw insertion (navigation) was introduced in the early 90's to increase the accuracy and safety of pedicle screw insertion. Material. PubMed literature search revealed two randomized controlled trials (RCT) comparing the in vivo accuracy of conventional and computer assisted pedicle screw insertion techniques. Three meta-analyses have assessed the published reports on the accuracy of pedicle screw insertion with or without computer assistance, one additional meta-analysis concentrated on the functional outcome of computer assisted pedicle screw insertion. Results. The RCTs by Laine et al and Rajasekaran et al achieved significantly higher screw placement accuracy with computer assistance than with the conventional techniquebased on anatomical landmarks. In a degenerative patient population, Laine et al reported a misplacement rate of 4.6% with computer assistance compared to 13.4% with the conventional technique. In addition to this quantitative difference, a qualitative difference in the misplaced screws was noticed: in the conventional group, 28 out of 37 misplaced screws were either inferior or medial, whereas in the computer assisted group, 1 out of 10 misplaced screws was situated in these ”danger zones”. In deformity surgery, Rajasekaran et al reported a 2% pedicle screw misplacement rate with a computer assisted technique compared to 23% with the conventional technique. Interestingly, in their study, the average screw insertion time in the computer assisted group was significantly shorter than with the conventional technique. The three meta-analyses, assessing up to 37 337 pedicle screws, reported significantly higher accuracy in the placement of pedicle screws with computerassistance compared with the conventional methods. The superiority of the computer assisted technique was even more obvious with abnormal surgical anatomy. CT-based and 3D-fluoroscopy-based navigation methods provided better accuracy compared to 2Dfluoroscopy-based navigation. No statistically significant benefit with computer assistance in the incidence of neuro-vascular complications, or in functional outcome was demonstrated. Conclusion. High pedicle screw misplacement rates have been reported with the conventional technique based on anatomical landmarks and intraoperative fluoroscopy. The concept of ”safe zone” is hypothetical, and underestimates the true risks of misplaced pedicle screws. Computer assistance significantly improves the accuracy and safety of pedicle screw insertion. It will, however, be difficult to correlate this increased accuracy to improved patient outcomes

We present an analysis of manual and computer-assisted preoperative pedicle screw placement planning. Preoperative planning of 256 pedicle screws was performed manually twice by two experienced spine surgeons (M1 and M2) and automatically once by a computer-assisted method (C) on three-dimensional computed tomography images of 17 patients with thoracic spinal deformities. Statistical analysis was performed to obtain the intraobserver and interobserver variability for the pedicle screw size (i.e. diameter and length) and insertion trajectory (i.e. pedicle crossing point, sagittal and axial inclination, and normalized screw fastening strength). In our previous study, we showed that the differences among both manual plannings (M1 and M2) and computer-assisted planning (C) are comparable to the differences between manual plannings, except for the pedicle screw inclination in the sagittal plane. In this study, however, we obtained also the intraobserver variability for both manual plannings (M1 and M2), which revealed that larger differences occurred again for the sagittal screw inclination, especially in the case of manual planning M2 with average differences of up to 18.3°. On the other hand, the interobserver variability analysis revealed that the intraobserver variability for each pedicle screw parameter was, in terms of magnitude, comparable to the interobserver variability among both manual and computer-assisted plannings. The results indicate that computer-assisted pedicle screw placement planning is not only more reproducible and faster than, but also as reliable as manual planning

Pedicle screw fixation is a technically demanding procedure with potential difficulties and reoperation rates are currently on the order of 11%. The most common intraoperative practice for position assessment of pedicle screws is biplanar fluoroscopic imaging that is limited to two- dimensions and is associated to low accuracies. We have previously introduced a full-dimensional position assessment framework based on registering intraoperative X-rays to preoperative volumetric images with sufficient accuracies. However, the framework requires a semi-manual process of pedicle screw segmentation and the intraoperative X-rays have to be taken from defined positions in space in order to avoid pedicle screws' head occlusion. This motivated us to develop advancements to the system to achieve higher levels of automation in the hope of higher clinical feasibility. In this study, we developed an automatic segmentation and X-ray adequacy assessment protocol. An artificial neural network was trained on a dataset that included a number of digitally reconstructed radiographs representing pedicle screw projections from different points of view. This model was able to segment the projection of any pedicle screw given an X-ray as its input with accuracy of 93% of the pixels. Once the pedicle screw was segmented, a number of descriptive geometric features were extracted from the isolated blob. These segmented images were manually labels as ‘adequate’ or ‘not adequate’ depending on the visibility of the screw axis. The extracted features along with their corresponding labels were used to train a decision tree model that could classify each X-ray based on its adequacy with accuracies on the order of 95%. In conclusion, we presented here a robust, fast and automated pedicle screw segmentation process, combined with an accurate and automatic algorithm for classifying views of pedicle screws as adequate or not. These tools represent a useful step towards full automation of our pedicle screw positioning assessment system

Introduction. Pedicle screw loosening in posterior instrumentation of thoracolumbar spine occurs up to 60% in osteoporotic patients. These complications may be alleviated using more flexible implant materials and novel designs that could be optimized with reliable computational modeling. This study aimed to develop and validate non-linear homogenized finite element (hFE) simulations to predict pedicle screw toggling. Method. Ten cadaveric vertebral bodies (L1-L5) from two female and three male elderly donors were scanned with high-resolution peripheral quantitative computed tomography (HR-pQCT, Scanco Medical) and instrumented with pedicle screws made of carbon fiber-reinforced polyether-etherketone (CF/PEEK). Sample-specific 3D-printed guides ensured standardized instrumentation, embedding, and loading procedures. The samples were biomechanically tested to failure in a toggling setup using an electrodynamic testing machine (Acumen, MTS) applying a quasi-static cyclic testing protocol of three ramps with exponentially increasing peak (1, 2 and 4 mm) and constant valley displacements. Implant-bone kinematics were assessed with a stereographic 3D motion tracking camera system (Aramis SRX, GOM). hFE models with non-linear, homogenized bone material properties including a strain-based damage criterion were developed based on intact HR-pQCT and instrumented 3D C-arm scans. The experimental loading conditions were imposed, the maximum load per cycle was calculated and compared to the experimental results. HR-pQCT-based bone volume fraction (BV/TV) around the screws was correlated with the experimental peak forces at each displacement level. Result. The nonlinear hFE models accurately (slope = 1.07, intercept = 0.2 N) and precisely (R. 2. = 0.84) predicted the experimental peak forces at each displacement level. BV/TV alone was a weak predictor (R. 2. <0.31). Conclusion. The hFE models enable fast design iterations aiming to reduce the risk of screw loosening in low-density vertebrae. Improved flexible implant designs are expected to contribute to reduced complication rates in osteoporotic patients

Aiming to evaluate the efficacy and safety of instrumentation using only segmental pedicle screw fixation, we undertook a prospective study of 17 patients with idiopathic scoliosis who underwent corrective surgery in 1998 and 1999. A total of 170 pedicle screws was inserted, 119 in the thoracic spine and 51 in the lumbar, extending from T2 to L5. The Cobb angle was measured on an erect anteroposterior radiograph postoperatively and at 6 and 12-month follow-up. Pedicle screw placement was assessed on the radiographs, and where there was concern about screw position, CT scan was performed. Of the 170 pedicle screws, three were malpositioned lateral to the pedicle and one medial to the pedicle. One pedicle fractured during screw insertion, and three screws partially pulled out on the convex side of the curve at T3 to T5. At six months the mean Cobb angle correction was 53.6%. There were no neurological complications. Two cases required subsequent trimming of rods. We believe fixation using only segmental pedicle screws is a safe method of correcting idiopathic scholastic deformities, but retain some reservations about the pull-out strength of the uppermost screws in the thoracic spine

A prospective cohort outcome evaluation of unstable thoracic spine fractures treated with posterior pedicle screw fixation. The purpose of this study was to determine the accuracy of placement and safety of pedicle screws in open reduction of unstable thoracic spine fractures. The surgeries were performed by one of five fellowship trained spinal surgeons. CT scans were formed on twenty-three patients totaling two hundred screws using 3mm cuts. Three independent reviewers assessed and categorized the screw position as within the pedicle or as a violation of the pedicle wall. 98% of the screws were accurate and we recommend the use of pedicle screws in thoracic fractures . A prospective cohort outcome evaluation of unstable thoracic spine fractures treated with posterior pedicle screw fixation. This study is to determine the accuracy of placement, safety of pedicle screws in open reduction of unstable thoracic spine fracture. Surgery was performed by one of five fellowship trained spine surgeons. CT scans were performed on twenty-three patients using 3mm cuts in both sagittal and transverse planes. Pedicle screw position was assessed by three independent reviewers. Screw position was categorized as within the wall of the pedicle or in violation of the wall. Further sub-classification of pedicle wall violation reviewed the direction and distance of perforation. Independent perioperative and postoperative surveillance for complications was done. Twenty-three unstable thoracic spine fractures treated with two hundred posterior pedicle screws were analyzed. The pedicle screws spanned from T1-T12 with the majority of screws in the mid-thoracic region. Of the two hundred thoracic pedicle screws placed, 70% were fully contained within the pedicle wall. The remaining screws were deemed “out” with cortical perforation (30%). Of these, 20% were lateral perforations, 5% were medial perforations and 5% were anterolateral perforations. No superior, inferior, or anteromedial perforations were found. There was no regional area variation in incidence of perforations. 10% of all perforations were directly related to pedicle diameter to screw diameter mismatch. There were no adverse neurological, vascular, or visceral injuries detected intraoperatively or postoperatively. Surgical management of unstable thoracic spine fractures with posterior pedicle screw fixation is safe. 98% of screws had satisfactory accuracy. Although very minor misplacement of pedicle screws occurred, there were no complications and we recommend the use of pedicle screws in thoracic fractures

Objectives. To employ a simple and fast method to evaluate those patients with neurological deficits and misplaced screws in relatively safe lumbosacral spine, and to determine if it is necessary to undertake revision surgery. Methods. A total of 316 patients were treated by fixation of lumbar and lumbosacral transpedicle screws at our institution from January 2011 to December 2012. We designed the criteria for post-operative revision scores of pedicle screw malpositioning (PRSPSM) in the lumbosacral canal. We recommend the revision of the misplaced pedicle screw in patients with PRSPSM = 5′ as early as possible. However, patients with PRSPSM < 5′ need to follow the next consecutive assessment procedures. A total of 15 patients were included according to at least three-stage follow-up. Results. Five patients with neurological complications (PRSPSM = 5′) underwent revision surgery at an early stage. The other ten patients with PRSPSM < 5′ were treated by conservative methods for seven days. At three-month follow-up, only one patient showed delayed onset of neurological complications (PRSPSM 7′) while refusing revision. Seven months later, PRSPSM decreased to 3′ with complete rehabilitation. Conclusions. This study highlights the significance of consecutively dynamic assessments of PRSPSMs, which are unlike previous implementations based on purely anatomical assessment or early onset of neurological deficits.and also confirms our hypothesis that patients with early neurological complications may not need revision procedures in the relatively broad margin of the lumbosacral canal. Cite this article: X-J. Lin. Treatment strategies for early neurological deficits related to malpositioned pedicle screws in the lumbosacral canal: A pilot study. Bone Joint Res 2016;5:46–51

Summary. Optimum position of pedicle screws can be determined preoperatively by CT based planning. We conducted a comparative study in order to analyse manually determined pedicle screw plans and those that were obtained automatically by a computer software and found an agreement in plans between both methods, yet an increase in fastening strengths was observed for automatically obtained plans. Hypothesys. Automatic planning of pedicle screw positions and sizing is not inferior to manual planning. Design. Prospective comparative study. Introduction. Preoperative planning in spinal deformity surgery starts by a proper selection of implant anchors throughout the instrumented spine, where pedicle screws provide the optimum choice for bone fixation. In the case of severe spinal deformities, dysplastic pedicles can limit screw usage, and therefore studying the anatomy of vertebrae from preoperative images can aid in achieving the safest screw position through optimal fastening strength. The purpose of this study is to compare manually and automatically obtained preoperative pedicle screw plans. Materials and Methods. CT scans of 17 deformed thoracic spines were studied by two experienced spine deformity surgeons, who placed 316 pedicle screws in 3D using a software positioning tool by aiming for the safest trajectory that permitted the largest possible screw sizes. The resulting manually obtained screw sizes, trajectory angles, entry points and normalised fastening strengths were compared to those obtained automatically by a dedicated computer software that, basing on vertebral anatomy and bone density in 3D, determined optimal screw sizes and trajectories. Results. Statistically significant differences were observed between manually and automatically obtained plans for screw sizes (p < 0.05) and trajectory angles (p < 0.001). However, for automatically obtained plans, screws were not smaller in diameter (p < 0.05) or shorter in length (p < 0.001), while screw normalised fastening strengths were higher (p < 0.001). Conclusions. In comparison to manual planning, automatically obtained plans did not result in smaller screw diameters or shorter screw lengths, which is in agreement with the definition of the pull-out strength, but in different screw trajectory angles, which is reflected by higher normalised fastening strengths. Captions. Fig. 1. Visual comparison among automatically obtained (green colour) and manually defined pedicle screw placement plans by two experienced spine surgeons (red and blue colour) for three different patients with adolescent idiopathic scoliosis, shown from top to bottom in a three-dimensional view, left sagittal, right sagittal and coronal view. Fig. 2. Histograms of differences between observers and (left column), between observer and automated method (middle column), and between observer and automated method (right column), shown from top to bottom for differences in pedicle screw pedicle screw diameter, sagittal inclination, and normalised fastening strength. For figures/tables, please contact authors directly.

The accuracy of pedicle screw placement is essential for successful spinal reconstructive surgery. The authors of several previous studies have described the use of image-based navigational templates for pedicle screw placement. These are designed based on a pre-operative computed tomographic (CT) image that fits into a unique position on an individual's bone, and holes are carefully designed to guide the drill or the pedicle probe through a pre-planned trajectory. The current study was conducted to optimise navigational template design and establish its designing method for safe and accurate pedicle screw placement. Thin-section CT scans were obtained from 10 spine surgery patients including 7 patients with adolescent idiopathic scoliosis (AIS) and three with thoracic ossification of the posterior longitudinal ligament (OPLL). The CT image data were transferred to the commercially available image-processing software and were used to reconstruct a three-dimensional (3D) model of the bony structures and plan pedicle screw placement. These data were transferred to the 3D-CAD software for the design of the template. Care was taken in designing the template so that the best intraoperative handling would be achieved by choosing several round contact surfaces on the visualised posterior vertebral bony structure, such as transverse process, spinous process and lamina. These contact surfaces and holes to guide the drill or the pedicle probe were then connected by a curved pipe. STL format files for the bony models with planned pedicle screw holes and individual templates were prepared for rapid prototype fabrication of the physical models. The bony models were made using gypsum-based 3D printer and individual templates were fabricated by a selective laser melting machine using commercially pure titanium powder. Pedicle screw trajectory of the bony model, adaptation and stability of the template on the bony model, and screw hole orientation of the template were evaluated using physical models. Custom-made titanium templates with adequate adaptation and stability in addition to proper orientation of the screw holes were sterilised by autoclave and evaluated during surgery. During segmentation, reproducibility of transverse and spinous processes were inferior to the lamina and considered inadequate to select as contact surfaces. A template design with more bone contact area might enhance the stability of the template on the bone but it is susceptible to intervening soft tissue and geometric inaccuracy of the template. In the bony model evaluation, the stability and adaptation of the templates were sufficient with few small round contact surfaces on each lamina; thus, a large contact surface was not necessary. In clinical patients, proper fit for positioning the template was easily found manually during the operation and 141/142 screws were inserted accurately with 1 insignificant pedicle wall breach in AIS patient. This study provides a useful design concept for the development and introduction of custom-fit navigational template for placing pedicle screws easily and safely

In the last few decades pedicle screw placement has brought in a genuine scientific revolution in the surgical care of spinal disorders. The technique has dramatically improved the outcomes of spinal reconstruction requiring spinal fusion. Short segment surgical treatments based on the use of pedicle screws for the treatment of neoplastic, developmental, congenital, traumatic and degenerative conditions have been proved to be practical, safe and effective. The reported incidence of nerve root damage after the use of pedicle screws ranges from 2% to 32%. The utilization of computerized image-guided technology in lumbosacral spinal fusion surgery offers increased accuracy of pedicle screw placement. We decided to review our x-rays of pedicle screw placement, and to assess the percentage misplacement of pedicle screws inserted without computer assistance. This is a retrospective study and our results are compared with those in the literature. 80 Post operative radiographs of patients operated on for trauma and degenerative conditions of the thoracolumbar spine were studied. Initially these were looked at independently by 2 orthopaedic spinal surgeons and a radiologist, and subsequently all x-rays were reviewed together to see where consensus could be reached where there was any disagreement. The percentage of misplaced screws inserted under fluoroscopy was obtained, and compared to the percentage of misplaced screws inserted under image guidance reported in the literature. Our study shows that there is no significant difference between the 2 techniques

Objective. The use of all pedicle screw constructs for the management of spinal deformities has gained widespread popularity. However, the placement of pedicle screws in the deformed spine poses unique challenges for the spinal surgeon. The purpose of this study was to evaluate the complications and radiological outcomes of surgery in 124 consecutive patients with spinal deformity. These patients underwent correction of coronal and sagittal imbalance with segmental pedicle screw fixation only. Background. All pedicle screw constructs have been associated with improved correction in all three planes. In patients with severe deformity, such constructs can obviate the need for anterior surgeries, and the higher implant cost is offset by the avoidance of dual anterior and posterior approaches. Pedicle screw fixation enables enhanced correction of spinal deformities, but the technique is still not widely applied for thoracic deformities for fear of neurological complications. This is a retrospective study that was carried out on 124 patients who underwent segmental screw fixation for coronal and sagittal spinal deformities. The purpose of this study was to evaluate the complications and outcomes of this technique and also assess the evidence of enhanced correction. Material and Methods. A total of 124 consecutive patients subjected to pedicle screw fixation for spinal deformities were analysed after a minimum period of follow-up of two years. Etiologic diagnoses were idiopathic scoliosis in 32, neuromuscular scoliosis 48, Scheuermann's kyphosis in 28 and others 16. They were reviewed using the medical records and preoperative, intraoperative and postoperative radiographs. Computed tomography was performed when screw position was questionable. Deformity correction was determined on preoperative and postoperative radiographs. The positions of the screws were evaluated using intraoperative and postoperative radiographs. There were 51 male and 73 female patients with the mean age of 17.2 years (range, 10-25 years). The average cobb angle for scoliosis and kyphosis were 55°(range 45°-85°) and 72° (range 68°-100°) respectively. Results. A total of 2784 pedicle screws were inserted and 1488 screws were inserted in the thoracic spine (18 screws/patient). Screw-related neurological complications occurred in two patients 0.4%; these comprised a transient paraparesis and dural tear. Other complications comprised six intraoperative pedicle fractures, 12 screw loosening, four postoperative infections and one haemothorax. There were no significant screw-related neurological or visceral complications. The average correction was 78% for scoliosis and 51% for kyphosis. The mean estimated blood loss was 653 ml (range, 510-850), the mean operation time was 148 minutes (range, 120-220). Conclusion. We were able to demonstrate that application of pedicle screw construct is safe and advantageous in the management of spinal deformities. Significant correction has been achieved with a single stage posterior surgery in all groups. Scoliosis and kyphotic deformity corrections were 78% and 51% respectively; this is far superior to correction achieved with one stage surgery with other constructs. This study showed that improved derotation has decreased the need for thoracoplasty, thus eliminating its risk of associated morbidity. Superior control of the deformity obviated the need for an anterior approach in severe curves. Improved correction, lower morbidity and shorter hospitalisation has compensated for higher implant cost. We believe using all pedicle screw fixation is a relatively safe procedure and offers an excellent correction. This correction was maintained throughout the follow up period. Despite our safety record in thoracic pedicle screw placement, we believe this technique can be potentially dangerous in inexperienced hands, and requires a long learning curve. Therefore, a thorough anatomical knowledge of pedicle morphology, a detailed analysis of pre-operative imaging coupled with experience is essential to avoid complications. Ethics approval None. Interest Statement None

Purpose: We describe a technique using orthoganol imaging on a radiolucent table that allows reliable, safe and reproducible insertion of thoracic pedicle screws. Method: The popularity of pedicle screws for spinal fixation in deformity surgery has increased. Studies have shown lumbar pedicle screws to be safe and effective. The biomechanical superiority of pedicle screws has also been demonstrated. Nonetheless, reluctance to apply the technique to thoracic vertebra remains, most likely because of perceived technical difficulties and a reported high complication rate. We describe a technique using orthoganol imaging on a radiolucent table, used in a series of patients in whom we have inserted a total of over 2000 screws. Results: We have inserted over 2000 thoracic pedicle screws without neurological injury. In addition, this technique has allowed us to use pedicle screw to the exclusion of other, less mechanically favourable, methods of fixation to the spine; over the same time period we used only three sublaminar hooks. Furthermore, the lateral to medial or ‘toeing in’ of screw placement gives greater pull out strength to each screw by increasing the ‘volume’ of bone that has to be overcome before failure by pull out occurs. In addition this trangulation technique allows insertion of :screws of greater diameter than the pedicle and decreases the chance of broaching medially. Conclusion: Using the technique described, we achieve accurate screw placement ‘first time, every time’, giving us a biomechanically superior construct, allowing more powerful derotation of the spine and thus greater correction of deformity. We recommend its use for all thoracic pedicle screws

Background. Accurate insertion of pedicle screws in scoliosis patients is a great challenge for surgeons due to the severe deformity of thoracic and lumbar spine. Meanwhile, mal-position of pedicle screw in scoliosis patients could lead to severe complications. Computer-assisted navigation technique may help improving the accuracy of screw placement and reducing complications. Thus, this meta-analysis of the published researches was conducted concentrating on accuracy of pedicle screw placement and postoperative assessment in scoliosis patients using computer-assisted navigation technique. Methods. PubMed, Cochrane and Web of Science databases search was executed. In vivo comparative studies that assessed accuracy and postoperative evaluation of pedicle screw placement in scoliosis patients with or without navigation techniques were involved and analysed. Results. One published randomised controlled trial (RCT) and seven retrospective comparative studies met the inclusion criteria. These studies included 321 patients with 3821 pedicle screws inserted. Accuracy of pedicle screw insertion was significantly increased with using of navigation system, while average surgery time was not significantly different with non-navigated surgery. And Correction rate for scoliosis in navigated surgery was not significantly different with non-navigated surgery. Conclusions. Navigation technique does indeed improve the accuracy of pedicle screw placement in scoliosis surgery, without prolong the surgery time or decrease the deformity correction effect

Background: Misplaced pedicle screws are associated with significant complications during posterior spinal instrumentation. Purpose: The purpose of this study is to evaluate the efficacy of triggered electromyographic stimulation in predicting the appropriate placement of pedicle screws. Study Design: Prospective clinical trial. Patient Sample: Fifteen consecutive patients (3 males; 12 females). Outcome Measures: Not applicable. Materials and Methods: All patients underwent posterior thoracolumbar spine fusion. Surgery was performed for spondylolisthesis, spinal stenosis, degenerative scoliosis and fractures. All patients received continuous electromyographic monitoring during surgery. During insertion of pedicle screws the integrity of the medial pedicle cortex was tested by stimulating each screw head with a monopolar pedicle probe stimulator and recording the compound muscle action potentials. A threshold of 7 mA and below was considered indicative of pedicle breach. Intraoperative screw placement was verified with the use of image intensifier. Finally, all patients following surgery underwent plain radiographs and CT scan of the operated region to evaluate the position of the pedicle screws. Results: One hundred and fourteen pedicle screws were inserted from T7 to S1 in all patients. There were no myogenic responses at the threshold tested. No screw had to be repositioned intraoperatively. There were no new neurologic deficits recorded following surgery. Review of the radiographs and CT scans obtained following surgery revealed no medial pedicle cortex breach. There were two screws that violated the lateral pedicle cortex, without any subsequent complications for the patients. Conclusions: Our study suggests that the absence of myogenic responses following stimulation at a threshold of 7 mA and below during pedicle screw placement, is a strong indicator that no medial pedicle cortex breach has occurred

To introduce a new robot-assisted surgical system for spinal posterior fixation which called TiRobot, based on intraoperative three-dimensional images. TiRobot has three components: the planning and navigation system, optical tracking system and robotic arm system. By combining navigation and robot techniques, TiRobot can guide the screw trajectories for orthopedic surgeries. In this randomised controlled study approved by the Ethics Committee, 40 patients were involved and all has been fully informed and sign the informed consent. 17 patients were treated by free-hand fluoroscopy-guided surgery, and 23 patients were treated by robot-assisted spinal surgery. A total of 190 pedicle screws were implanted. The overall operation times were not different for both groups. None of the screws necessitated re-surgery for revised placement. In the robot-assisted group, assessment of pedicle screw accuracy showed that 102 of 102 screws (100%) were safely placed (<2 mm, category A+B). And mean deviation in entry point was 1.70 +/− 0.83mm, mean deviation in end point was 1.84 +/− 1.04mm. In the conventional freehand group, assessment of pedicle screw accuracy showed that 87 of 88 (98.9%) were safely placed (<2 mm, category A+B), 1 screw fall in category C, mean deviation in entry point was 3.73 +/− 2.28mm, mean deviation in end point was 4.11 +/− 2.31mm. This randomised controlled study verified that robot-assisted pedicle screw placement with real-time navigation is a more accuracy and safer method, and also revealed great clinical potential of robot-assisted surgery in the future