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Background Percutaneous pedicle screw (PPS) placements in the lumbosacral spine generally rely on fluoroscopy at the expense of radiation exposure. Our accumulated experience in open PS placements without fluoroscopic guidance realized a consistent shift toward PPS insertion with newly developed devices, which require neither fluoroscopy nor navigation. We wish to report our new technique and evaluations of its accuracy. Methods Our equipment consisted of a pedicle targeting tool to identify and escort the cannulated awl to the correct starting point for cortical bone perforation and a cannulated awl-probe system with a guidewire to maintain the optimal position throughout the subsequent surgical steps. The surgeon could advance the blunt-tipped probe searching for the cancellous bone track using tactile feedback as experienced in open techniques. A 2-year period of transition from a free-hand (1169 screws in 286 patients) to the new PPS technique (1933 screws in 413 patients) allowed accuracy comparison between the two procedures using postoperative CT scans. Results Compared with the open-group, the PPS-group showed a lower rate of fully contained intrapedicular PS placements at L1 through S1, as a whole (90.7% vs 85.4%), but not at L4 through S1 (89.9% vs 90.2%). Less-accurate PPS placements at upper than lower lumbar spines in part reflect intended pedicle perforations laterally as a trade-off for avoiding facet violation immediately above the most cephalad screw. The PPS-group also had a higher incidence of PS-related transient nerve root complications (0% vs 1.7%). These values for the PPS-group, however, fell within those previously reported for free-hand or fluoroscopy techniques. Conclusions Our new PPS technique, although useful for eliminating the potential risk of repeated radiation exposure, fell short of reaching the accuracy of the free-hand technique. Nerve integrity monitoring with PS stimulation, which we currently use, will help further improve the technical precision. Study design Original Article. The study was approved by our institutional review boad (2,019,231).

Background The bicortical or tricortical fixation technique with purchase into the anterior sacral wall or promontory has been recommended to achieve rigid sacral pedicle screw fixation, which carries the potential risk of neurovascular injuries. The penetrating endplate screw (PES) technique was proposed as an alternative screw trajectory to facilitate both strong fixation and safety. However, there has been no report on the practical significance of using the PES technique. The aim of the present study was to investigate radiological outcomes using the PES technique for lumbosacral fusion by comparing it with the anterior bicortical technique. Methods The subjects consisted of 44 patients with L5 isthmic spondylolisthesis who underwent single-level posterior lumbar interbody fusion at L5-S using the PES technique (20 patients) or the anterior bicortical technique (24 patients) and were followed up for > 2 years (mean follow-up: 36.6 months). Screw loosening and bone fusion were radiologically assessed and compared between the two groups. Factors contributing to bone fusion were investigated using the following factors: (1) age, (2) sex, (3) body mass index, (4) bone mineral density, (5) screw diameter, (6) screw length, (7) pelvic incidence, (8) crosslink connector, (9) cage material, and (10) sacral screw insertion technique. Results Respective screw loosening and bone fusion rates were 10.0 and 90.0% using the PES technique and 29.2 and 79.2% using the anterior bicortical technique, with no significant differences between the two techniques. Multivariate logistic regression analysis revealed that the age (odds ratio = 0.87, p = 0.02) and PES technique (odds ratio = 22.39, p = 0.02) were significant independent factors contributing to bone fusion. Conclusions This is the first study to demonstrate the significance of using the PES technique to improve radiological outcomes. The PES technique could be a valid option for lumbosacral fixation for L5 isthmic spondylolisthesis in terms of improved bone fusion.

Background The anterior cage at L5-S1 segment is more vulnerable to anterior migration because of the sacral slope, the greater disc angle (DA), the higher shear force, and the weaker pedicle screw fixation at S1. We hypothesized that a supplemental screw (SS) fixation is effective for the prevention of anterior cage migration in oblique lateral interbody fusion (OLIF) at L5-S1. Methods This study involved 61 consecutive patients who underwent OLIF at L5-S1 and had more than 1-year regular follow-up. In the first 35 cases, the anterior cage was fixed with pedicle screws only (non-SS group). In the remaining 26 cases, the anterior cage was fixed with a SS and pedicle screws (SS group). Radiological parameters including anterior disc height (ADH), posterior disc height (PDH), DA, cage migration, cage subsidence, and fusion rate at L5-S1 were compared between the two groups. Result Of the total 61 patients, fifteen (24.6%) patients had an anterior cage migration of >2 mm and six (9.8%) patients had an anterior cage migration of >5 mm. Baseline demographic characteristics were similar between the two groups. The mean cage migration was 2.0 ± 3.1 mm in the non-SS group and 0.9 ± 0.9 mm in the SS group (P = 0.038). Thirteen (37.1%) patients had a cage migration of >2 mm in the non-SS group, while only two (7.7%) had a cage migration of >2 mm in the SS group (P = 0.002). There were no significant differences in the ADH, PDH, DA, cage subsidence, and fusion rate between the two groups (all P > 0.05). There was no SS-related complication in the SS group. Conclusions SS fixation in front of the anterior L5-S1 cage is simple, safe, and effective for the prevention of anterior cage migration in OLIF at L5-S1.

The cervicothoracic junction (CTJ) is the site of transition in biomechanical, osseous, and alignment properties of the spine. The interface between the highly mobile, lordotic cervical spine and the rigid, kyphotic thoracic spine results increased the biomechanical stress experienced at this junction. The concentration of stress at this level has led to high rates of failure when instrumenting near or across the CTJ. The changes in osseous anatomy from the cervical spine to the thoracic spine present additional challenges in construct planning. For these reasons, a thorough understanding of the complexity of the cervicothoracic junction is necessary when operating near or across the CTJ. There are multiple options for cervical fixation, including lateral mass screws, pedicle screws, and laminar screws, each with its own advantages and risks. Instrumentation at C7 is controversial, and there is data supporting both its inclusion in constructs and no risk when this level is skipped. Thoracic pedicle screws are the preferred method of fixation in this region of the spine; however, the connection between cervical and thoracic screws can be challenging due to differences in alignment. Transitional rods and rod connectors mitigate some of the difficulties with this transition and have shown to be effective options. Recently, more investigation has looked into the failure of posterior cervical constructs which end at or near the CTJ. The trend in data has favored fixation to T1 or T2 rather than ending a construct at C7 due to the decreased rates of distal junction kyphosis. Although data on patient-reported outcomes with a length of constructs and the lowest instrumented vertebra is scarce, preliminary reports show no difference at this time. As posterior cervical instrumentation continues to increase in frequency, the CTJ will continue to be an area of difficulty in navigation and instrumentation. A thorough understanding of this region is necessary and continued research is needed to improve outcomes.Level V.

Pedicle screw (PS) placement in thoracic scoliotic deformities can be challenging due to altered vertebral anatomy; malposition can result in severe functional disability or inferior construct stability. Three-dimensional (3D) printed patient-specific guides (PSGs) have been recently used to supplement other PS placement techniques. We conducted a single-center, retrospective observational study to assess the accuracy of PS placement using PSGs in a consecutive case series of pediatric and adult patients with thoracic scoliosis.We analyzed the data of patients with thoracic scoliosis who underwent PS placement using 3D-printed PSG as a vertebral cannulation aid between June 2013 and July 2018. PS positions were determined via Gertzbein-Robbins (GR) and Heary classifications on computed tomography images. We determined the concordance of actual and preoperatively planned PS positions and defined the technique learning curve using a receiver-operating characteristic (ROC) curve.We performed 362 thoracic PS placement procedures in 39 consecutive patients. We classified 352 (97.2%), 2 (0.6%), and 8 (2.2%) screws as GR grades 0 (optimal placement), I, and II, respectively. The average instrumented PS entry point offsets on the X- and Y-axes were both 0.8 mm, and the average differences in trajectory between the planned and the actual screw placements on the oblique sagittal and oblique transverse planes were 2.0° and 2.4°, respectively. The learning process was ongoing until the first 12 PSs were placed.The accuracy of PS placement using patient-specific 3D templates in our case series exceeds the accuracies of established thoracic PS placement techniques.

Existing freehand techniques of screw placement mainly emphasized on various entry points and complex trajectory reference. The aim of this study is to illustrate a standardized and reliable freehand technique of pedicle screw insertion for open pedicle screw fixation with a universal entry point and a stereoscopic trajectory reference system and report the results from a single surgeon's clinical experience with the technique.In this study, the author respectively reviewed a total of 200 consecutive patients who had undergone open freehand pedicle screw fixation with Superior Articular Process (SAP) technique from January 2019 to May 2020. For accuracy and safety, all 200 cases had undergone postoperative X-ray while 33 cases including spinal deformity, infection, and tumor had received additional CT-scan. Screw accuracy was analyzed via a CT-based classification system with Student's t test.A total of 1126 screws had been placed from T1-S1 with SAP-guided freehand technique and the majority had been confirmed safe in X-ray without the need of CT scan. A total of 316 screws in deformity or infectious or tumor cases had undergone additional CT scan with 95.5% (189 of 198 screws) accuracy in thoracic group and 94.9% (112 of 118 screws) in lumbar group. The accuracy had been 90.5% (114 of 126 screws) in deformity group and 95.8% (182 of 190 screws) in non-deformity group. All perforation cases had been rated Grade B (2 mm) without significant difference between the medial and the lateral (p 0.05). No cases had been detected with significant neurological deficiencies. The mean intraoperative X-ray shots were 0.73 per screw.SAP-guidance is a reliable freehand technique for thoracic and lumbar pedicle screw instrument. It allows accurate and safe screw insertion in both non-deformity and deformity cases with less radiation exposure.

Lumbosacral fixation is commonly used for the management of lumbosacral instability. As the sacrum mainly consists of cancellous bone, bicortical fixation, in which the pedicle screw penetrates the anterior sacral cortex, can help increase the strength of fixation. However, this method carries a risk to the L5 nerves which lie anterior to the sacrum at this level.The goal of this study is to determine a safe zone for the placement of S1 pedicle screws to decrease the likelihood of L5 nerve injury.Retrospective imaging review.This study evaluated imaging data of patients who underwent lumbar spine magnetic resonance imaging (MRI) at our institute between September 1, 2020 and September 1, 2021.T1-weighted axial MRIs were measured at the level of S1 pedicle screw placement. The space medial and lateral to the L5 nerve root on the anterior sacrum were measured and defined as safe zones. Additionally, the nerve width and sacral lengths were measured at this level.The distribution of the measurements were evaluated to determine a medial and lateral safe zone, as well as the average nerve width at the level of S1 pedicle screw placement. Correlation analysis was performed to determine a relationship between safe zone sizes and sacral size.A total of 400 MRIs were analyzed. The average medial safe zone measured was 32.8 mm (95% CI: 32.2-33.4) with no nerves lying within 22.3 mm of the midline sacrum. The average lateral safe zone measured was 17.7 mm (95% CI: 17.1-18.2), with no nerves within 5.3 mm of the lateral border of the sacrum. The average nerve root width was 6.2 mm (95% CI: 6.13-6.34). An increased sacral length was associated with a larger medial (p.001) and lateral (p.001) safe zone.Our study revealed lateral and medial safe zones for the placement of S1 pedicle screws to avoid iatrogenic nerve injury in a retrospective cohort of 400 patients. There were no L5 nerve roots found within 22.3 mm of the sacrum's mid-axis or within 5.3 mm of the sacrum's anterolateral border. These defined safe zones can be used during pedicle screw planning and placement to decrease the risk of injury to the L5 nerve root.

Dorsal instrumentation and decompression are the mainstays of spinal tumor treatment. Replacing titanium screws with carbon fiber-reinforced polyetheretherketone (CFRP) screws can reduce imaging artifacts on neural structures and perturbations of radiation dose. Further reduction of metal content in such screws might enhance the benefit. The aim of this study was to assess the artifacts produced by all-titanium screws (Ti-Ti), CFRP thread-titanium screw heads (C-Ti), and all-CFRP screws (C-C).A cadaveric spine was used to place Ti-Ti, C-Ti, and C-C consecutively from T2 to S1. Computed tomography and 1.5T and 3T magnetic resonance imaging were performed for each screw system. Axial T1- and T2-weighted sequences of representative thoracic and lumbar regions were assessed for artifacts. The artifacts were classified as not relevant, considerable, or severe.We evaluated 92 screws and made 178 artifact assessments. The artifacts were clearly visible in computed tomography scans but did not influence the visualization of intraspinal structures. Severe magnetic resonance imaging artifacts were found in 28% (17/60, mostly in the thoracic spine) of Ti-Ti, 2% (1/60, all T1 sequences) of C-Ti, and 0% of C-C, and considerable artifacts were found in 47% (28/60) of Ti-Ti, 10% (6/60, only 1 T2 sequence) of C-Ti, and 0% of C-C screws (P0.001).CFRP pedicle screws reduced the artifact intensity in spinal structures compared with titanium screws, and may be beneficial for planning radiotherapy and for follow-up imaging. C-C demonstrated an enhanced effect on dorsal structures.

Studies have compared the safety and accuracy of robot-assisted techniques for inserting conventional open pedicle screws for spinal surgery. However, no relevant studies have confirmed that robot-assisted percutaneous screw placement is better than fluoroscopic percutaneous screw placement for the treatment of thoracolumbar fractures. This study compared the accuracy and safety of TiRobot-assisted percutaneous pedicle screw placement with those of the fluoroscopy-assisted percutaneous technique for the treatment of thoracolumbar fractures.This retrospective study included 126 patients with thoracolumbar fractures who underwent percutaneous pedicle screw placement. Sixty-five patients were treated with the TiRobot-assisted technique and 61 patients were treated with the fluoroscopy-assisted technique. Patient demographics, accuracy of screw placement (according to the Gertzbein and Robbins scale of grades A to E), screw insertion angle, radiation exposure, surgical time, intraoperative blood loss, length of hospital stay, incision length, hospital expenses, surgical site infection, and neurological injury of the TiRobot-assisted and fluoroscopy-assisted groups were compared using Student's t-test, Pearson χA total of 729 screws were placed (TiRobot-assisted group: 374 screws; fluoroscopy-assisted group: 355 screws). In the TiRobot-assisted group, 82.8% of screws were optimally positioned (grade A); however, the placement grades of the remaining screws were categorized as grade B (13.3%), grade C (3.2%), and grade D (0.5%). In the fluoroscopy-assisted group, 66.7% of the screws were optimally positioned (grade A); however, the placement grades of the remaining screws were categorized as grade B (21.4%), grade C (7.6%), grade D (3.6%), and grade E (0.5%). The proportion of clinically acceptable screws (grade A or B) was greater in the TiRobot-assisted group than in the fluoroscopy-assisted group. Additionally, the TiRobot-assisted group had a significantly larger mean screw insertion angle (22.27° ± 5.48° vs 20.55° ± 5.15°), larger incision length (13.86 ± 1.24 cm vs 12.77 ± 1.43 cm), and higher hospital expenses (69061.55 ± 7166.60 yuan vs 59383.85 ± 5019.64 yuan) than the fluoroscopy-assisted group. There were no significant differences in the intraoperative blood loss, length of hospital stay, and rates of surgical site infection and neurological injury in both groups (p 0.05). However, the TiRobot-assisted group had significantly better surgical times, radiation times, and radiation exposure than the fluoroscopy-assisted group (p 0.05).Percutaneous TiRobot-assisted pedicle screw placement is a safe, useful, and potentially more accurate alternative to the percutaneous fluoroscopy-assisted technique for treating thoracolumbar fractures.

Aim. To compare the safety and efficacy of computed tomography (CT)-assisted three-dimensional guiding templates (3DGTs) and free-hand (FH) technique for posterior cervical pedicle screw fixation in cervical spondylotic myelopathy (CSM) treatment. Methods. Thirty-five patients (216 screws) with CSM and developmental cervical stenosis were randomly divided into groups A (FH) and B (3DGTs). All patients underwent modified posterior surgery with cervical pedicle screw insertion (C1-7). Preoperative, postoperative, and intergroup comparisons of efficacy were evaluated using the visual analog scale (VAS), Japanese Orthopaedic Association (JOA), and Short Form 12 (SF-12) scores and JOA score improvement rate. Incidence of intra- and postoperative complications was analyzed. Postoperative cervical spine CT was performed to evaluate (i) the pedicle screws’ deviation angle from the optimal path (sagittal deviation, α; coronal deviation angle, β), screw insertion point’s deviation distance (d), and screw accuracy and (ii) the deviation angle and distance of screw entrance point of pedicle screws from the optimal channel. Results. All patients successfully completed the procedures. Groups A and B did not significantly differ in age, sex ratio, body mass index, operative time, or intraoperative blood loss amount. Postoperative VAS, JOA, and SF-12 scores improved in both groups. VAS, JOA, or SF-12 scores did not significantly differ between the 2 groups. The α, β, and d scores were lower in group B, but accuracy was higher in group B. Conclusions. 3DGTs and FH technique show comparable outcomes with respect to neurological improvement and safety.

To evaluate the clinical efficacy of the treatment of scoliosis with a pedicle screw system through paraspinal intermuscular approach (PIA).This is a retrospective case series study. A total of 10 patients diagnosed with scoliosis had surgical indications and treated with a pedicle screw system in one-stage posterior surgery by PIA from March 2013 to April 2015 at the First Hospital of Jilin University were enrolled in this study. The average age of the patients was 14.9 years, including one male and nine females. The operative information and surgical results, including Cobb angle correction, correction loss, global balance (including Frontal Plane Balance [FPB] and Sagittal Plane Balance [SPB]), and fusion rate were reviewed. Functional outcomes including visual analog scale (VAS) back pain score, leg pain score, and Scoliosis Research Society-22 questionnaire (SRS-22) were used to evaluate the quality of life of patients preoperatively and at last follow-up.Each patient was followed up at least six times. The average follow-up time was 43.2 months. Mean scoliosis and kyphosis improved from 68.5° ± 18.1°to 18.7° ± 11.8° and from 34.4° ± 17.9°to 24.0° ± 6.7°, respectively (p 0.05); at last follow-up, it was 20.1° and 24.7°, respectively (p 0.05). During the follow-up, mean coronal and sagittal correction loss was 1.4° ± 1.2°and 0.7° ± 0.8°, respectively (p 0.05). Mean FPB improved from 32.7 to 11.7 mm (p 0.05); Mean SPB changed from 0.3 to -0.7 mm (p 0.05). No dural tears were observed during the corrective surgery or wound infection or implant-related complications. No pseudoarthrosis was identified according to the last follow-up three-dimensional (3D) CT scan. All the domains in SRS-22 questionnaire show statistically significant improvement at the last follow-up (p 0.05). The VAS back pain scores improved from a mean preoperative score of 1.7 to a mean postoperative score of 0.2 (p 0.05).This original one-stage posterior PIA is safe and effective in the treatment of scoliosis, which is characterized with less blood loss, shorter operation time, and satisfactory bony fusion.

Pedicle screws placement is very common procedure in spinal surgery. Robotic assisted surgery has been widely used in this operation. We assessed the accuracy of thoracolumbar spine trans-pedicle screws (TPS) implantation utilizing a noval robotic navigation system (i-Navi robotic navigation system) by planning with two-dimensional (2-D) C-arm.This study was approved by the Institutional Review Board of the Cathay General Hospital on June 21, 2018 (IRB number: CGH-P 106,092), and written informed consents were obtained from all the patients. There are 18 patients were enrolled in the study. All the patients received the posterior fusion with TPS insertion under the assistant of our robotic navigation system.There are 18 patients were included into our study, there are 2 patients were quitted from the study due to the equipment setup was not complete. Other 16 patients completed the entire procedure successfully. There is total 88 pedicle screws were inserted through i-Navi robotic navigation system. There are 79 of 88 screws were graded A, and 9 screws were graded B; no screws were graded C or D. No vascular or nerve injuries were noted after the operations.We present our i-Navi robotic navigation system, by planning with 2-D C-arm imaging and pre-operative CT scans. According to the results of study, we think it can provide a reliable and easy tool to perform the TPS in thoracic lumbar spine surgery.

Aims The aim of this study was to evaluate whether, after correction of an adolescent idiopathic scoliosis (AIS), leaving out the subfascial drain gives results that are no worse than using a drain in terms of total blood loss, drop in haemoglobin level, and opioid consumption. Methods Adolescents (aged between 10 and 21 years) with an idiopathic scoliosis (major curve ≥ 45°) were eligible for inclusion in this randomized controlled noninferiority trial (n = 125). A total of 90 adolescents who had undergone segmental pedicle screw instrumentation were randomized into no-drain or drain groups at the time of wound closure using the sealed envelope technique (1:1). The primary outcome was a drop in the haemoglobin level during first three postoperative days. Secondary outcomes were 48-hour postoperative oxycodone consumption and surgical complications. Results All 90 patients were included in the primary outcome analysis (no drain = 43; drain = 47). The mean total postoperative blood loss (intraoperative and drain output) was significantly higher in the group with a subfascial drain than in the no-drain group (1,008 ml (SD 520) vs 631 ml (SD 518); p < 0.001). The drop in haemoglobin level did not differ between the study groups over the postoperative timepoints (p = 0.290). The 48-hour opioid consumption was significantly higher in the no-drain group (2.0 mg/kg (SD 0.9) vs 1.4 (SD 0.6); p = 0.005). Two patients in the no-drain and one patient in the drain group developed a surgical site infection. Conclusion Leaving the subfascial drain out after pedicle screw instrumentation for AIS is not associated with higher postoperative haemoglobin levels. Patients treated without a subfascial drain needed 30% more opioids during the first 48 hours than those who had a drain. Cite this article: Bone Joint J 2022;104-B(9):1067–1072.

Background Lateral lumbar interbody fusion (LLIF) is widely used in degenerative lumbar spine surgery. Previous studies of radiographic investigations after LLIF have assessed the anterior interbody fusion rate, the changes in the segmental lumbar lordosis, efficacy of indirect neural decompression, and remodeling of the ligamentum flavum hypertrophy and spinal canal dimension, and so on. The purpose of this study was to evaluate the radiological changes in the degenerated facet joints following LLIF with bilateral percutaneous pedicle screw (PPS) fixation, focusing on spontaneous fusion. Methods We retrospectively analyzed 31 patients (79 surgical levels) who underwent two- or three-level LLIF with PPS fixation without direct posterior decompression and bone grafting. We assessed the fusion rate and characteristics of the facet joints’ fusion process on the preoperative, immediately postoperative, 12-month, and at least 2-year computed tomography (CT) images. On average, the last follow-up CT was performed after 30.2 months. Multivariate logistic regression analysis investigated factors related to spontaneous facet joint fusion postoperatively. Results The fusion rates of the interbody and facet joints were 32.9% (26/79) and 19.0% (15/79) after 12-months and 79.7% (63/79) and 58.2% (46/79) at the final CT follow-up, respectively. Of the 46 cases with spontaneous facet fusion, three cases fused posteriorly only. Concomitant anterior interbody fusion was seen in 43/46 (93.5%) cases. Facet fusion started in a ring shape from the outermost joint edges, exposing subchondral bone without cartilage covering, and progressed to the central thicker cartilage regions. Multivariate analysis established that concomitant anterior interbody fusion (adjusted odds ratio [aOR]: 12.10, P = 0.0035) and preoperative facet joint osteoarthritis of Weishaupt Grade ≧ 1 (aOR: 4.770, P = 0.0068) were significant contributing factors to postoperative spontaneous facet fusion. Conclusions Our study shows that spontaneous facet fusion frequently occurs after LLIF and may be an indicator of the inherent structural stability of the LLIF construct.

Lateral lumbar interbody fusion (LLIF) and percutaneous posterior screw fixation (PPSF) techniques is used to treat degenerative lumbar pathologies. Dual-position (DP) lumbar surgery involves repositioning the patient from the supine or lateral decubitus position to prone for posterior fixation. Single-position (SP) lumbar surgery is commonly performed nowadays, a minimally invasive alternative performed entirely from the lateral decubitus position. However, controversy still exists. This meta-analysis aimed to compare perioperative outcomes between SP lumbar surgery and DP lumbar surgery for LLIF and PPSF.We conducted this meta-analysis according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and searched Medline and Scopus from inception to November 11, 2021, for relevant studies.Six studies were identified, which contained totals of 502 and 447 patients in the SP and DP groups, respectively. The unstandardized mean difference in operative time, length of hospital stay, intraoperative blood loss, radiation doses, lumbar lordosis, and pelvic incidence-lumbar lordosis mismatch were -86.1 (95% confidence interval [CI] -149.2 to -23.1) minutes, -1.6 (95% CI -2.4 to -0.9) days, -55.6 (95% CI -127.5 to 16.2) mL, -30.3 (95% CI -80.5 to 19.8) mGy, 1.34 (95% CI -1.17 to 3.86) degrees, and -4.06 (95% CI -5.65 to -2.47) lower in SP when compared with DP. The chances of having complications and reoperations in SP were 0.75 (95% CI 0.49-1.14) and 0.77 (95% CI 0.44-1.36) times, respectively, compared with the DP group. No significant differences were found for intraoperative blood loss, radiation dose, lumbar lordosis, complications, and reoperations between the 2 groups.This meta-analysis found that SP have lower operative time and length of hospital stay compared with DP LLIF and PPSF. However, no differences in intraoperative blood loss, radiation dose, radiographic change, complications, and reoperation rates were found.

The objective of this study was to introduce a retractor that can be temporarily installed on unilateral pedicle screws to achieve distraction-reduction and nerve root protection, and to analyze the efficacy and safety of retractor-assisted transforaminal lumbar interbody fusion (TLIF) in the treatment of lumbar spondylolisthesis.This was a retrospective study of 125 patients who underwent retractor-assisted TLIF for single-segment spondylolisthesis from November 2017 to February 2021. Based on morphology, patients were divided into degenerative (N = 66) and isthmic groups (N = 59). Differences in demographics and preoperative characteristics between the groups were analyzed using the independent samples t-test and χUnilateral screw retractor-assisted TLIF significantly corrected spondylolisthesis and improved disc height and segmental lordosis (p 0.05). There was no significant difference in foramen height between the two sides before and after operation (pre: 15.81 ± 3.58 mm vs 15.69 ± 3.68 mm, p = 0.599; post: 18.65 ± 2.31 mm vs 18.74 ± 2.26 mm, p = 0.516). The degree of spondylolisthesis in the DLS group before surgery was significantly lower than that in the isthmic spondylolisthesis group (17.70 ± 5.62% vs 25.18 ± 9.73%, p 0.001), whereas a similar degree of correction could be achieved after surgery (5.91 ± 3.12% vs 7.16 ± 5.69%, p = 0.135). FJAs from L3/4 to L5/S1 were significantly smaller in patients with DLS than those in with isthmic spondylolisthesis (p 0.05). Patients with facet sagittalization were more likely to have DLS (β: -0.101, odds ratio [OR]:0.904, 95% confidence interval [CI]: 0.874-0.934, p 0.001), while the cut-off FJA of L4/5 for predicting L4 spondylolisthesis was 53.19.Pedicle screw retractor-assisted TLIF is effective and safe in treating both degenerative and isthmic lumbar spondylolisthesis. The unilateral retractor has the capacity to maintain the disc height achieved by paddle distractors, which optimizes the nerve protection and distractor placement. Patients with an FJA on L4/553.19 were more likely to have DLS.

The pedicle morphology of ankylosing spondylitis (AS)-related thoracolumbar kyphosis patients may be different from that of individuals with normal spine due to the ectopic ossification and kyphotic deformity. However, there was no literature analyzing the pedicle morphology of AS patients with thoracolumbar kyphosis. Therefore, the present study aimed to investigate the pedicle morphology of lower thoracic and lumbar spine (T9-L5) in ankylosing spondylitis (AS)-related thoracolumbar kyphosis patients.A retrospective review of AS patients with thoracolumbar kyphosis (AS group) and the patients with spinal or rib fracture (fracture group) who underwent CT scans of the lower thoracic and lumbar spine between February 2017 and September 2018 was performed. Patients with spinal tumor, spinal tuberculosis, severe degenerative spinal diseases including degenerative scoliosis, degenerative spondylolisthesis, degenerative spinal stenosis or history of previous spine surgery, or AS patients with pseudarthrosis which influenced the measurement of pedicle parameters were excluded. The measured parameters on CT images included transverse pedicle angle (TPA), transverse pedicle width (TPW), chord length (CL), pedicle length (PL), and sagittal pedicle angle (SPA). The intraclass correlation coefficient (ICC) was used to evaluate the agreement of radiographic parameters between observers. The independent sample t test was applied for the comparison of pedicle parameters between the two groups. The gender distribution between the two groups were compared using the Fisher's exact test.A total of 1444 pedicles of 53 AS-related thoracolumbar kyphosis patients and 30 patients with fracture were analyzed. TPA was significantly smaller in AS group (p 0.05). Significantly larger TPW was found in AS group in the lumbar spine (p 0.05). TPW ≥ 7.5 mm was observed in 95.3%-98.1% of the pedicles at the levels of L3-L5 in AS group. The CL and PL were significantly larger in AS group at the levels of T9-L5 (p 0.05). The CL ≥ 50 mm was found in 84.0%-96.2% of the pedicles in mid-to-lower lumbar spine in AS group. Significantly smaller SPA was found in AS group at the levels from L3 to L5 (p 0.05).Pedicle screws with relatively large diameter of 7.5 mm and length of 50 mm could be used in mid-to-lower lumbar spine in the majority of AS-related thoracolumbar kyphosis patients. Also, the insertion angle of pedicle screws in both the transverse and sagittal plane should be appropriately reduced in these patients. This study may help surgeons select the pedicle screws of appropriate size in AS patients.

This pilot study was undertaken to evaluate the safety, performance, and usability of the Xvision-Spine (XVS) System (Augmedics, Arlington Heights, IL) during open spinal fixation procedures in patients requiring pedicle screw placement in the lumbosacral spine.The XVS System is an augmented reality head-mounted display (HMD) based on a computer navigation system designed to assist surgeons in accurately placing pedicle screws. It uses an HMD-mounted tracking camera to provide optical tracking technology, and provides the surgeon a translucent direct near-eye display of the navigated surgical instrument's location relative to the computed tomographic image. We report the preliminary results of a prospective series of all consecutive patients who underwent augmented reality-assisted pedicle screw placement in the lumbosacral vertebrae at 3 institutions. Clinical accuracy for each pedicle screw was graded with Gertzbein-Robbins scores by 2 independent and blinded neuroradiologists.The 19 study participants included 8 men and 11 women with a mean age of 59.13 ± 12.09 and 59.91 ± 12.89 years, respectively. Seventeen procedures were successfully completed via the XVS System. Two procedures were not completed due to technical issues with the system's intraoperative scanner. A total of 86 screws were inserted. The accuracy of the XVS System was 97.7%.The XVS System's performance in accurate placement of pedicle screws in the lumbosacral vertebrae had an overall accuracy of 97.7%. These preliminary results were comparable to the accuracy of other manual computer-assisted navigation systems reported in the literature.

C2 pedicle screw placement in patients with basilar invagination (BI) is fraught with risks because of a high incidence of anatomical variations and high-riding vertebral artery (HRVA). However, no study can be found in the literature that attempted to identify the ideal entry point and trajectory through the C2 pedicle in BI patients with HRVA.To investigate the parameters of ideal entry point and trajectory for C2 pedicle screw placement in BI patients with HRVA and compare them with those in BI patients without HRVA and patients without BI as control. These parameters would serve as a guide to pedicle screw placement.A retrospective comparative study.A total of 396 patients (198 consecutive BI patients and 198 matched patients without BI as control) and 792 unilateral pedicles from April 2017 to October 2021 at two medical centers were included.The insertion parameters of mediolateral angle, surface distance, cephalad angle, and vertical distance from the superior border of the lamina were the primary outcome measures for the reference of C2 pedicle screw placement. Furthermore, factors that affect the primary insertion parameters were assessed via multiple linear regression analyses.According to the diagnosis of BI and HRVA, the unilateral pedicles were assigned into HRVA of BI, non-HRVA of BI, HRVA of control, and non-HRVA of control groups. Subgroup analyses based on Goel types A and B were also performed. Moreover, vertebral artery (VA) anomalies that might result in potentially serious complications were identified and systematically compared.The measurements of insertion parameters in BI patients with HRVA indicated a mean mediolateral angle of 27.42°, a mean cephalad angle of 43.02°, a mean surface distance of 9.74 mm, and a mean vertical distance from the superior border of the lamina of 3.85 mm. Compared with that in BI patients without HRVA, the measurements suggested that the entry point in BI patients with HRVA should be shifted upward by 0.38 mm and the trajectory should be angled cephalad by 6.05° and medially by 4.78°. In the control group, changes in the insertion parameters between HRVA and non-HRVA showed a similar trend to the BI group. Multiple linear regression showed that mediolateral angle was significantly associated with the male gender (B=-0.930, p=.017) and the diagnoses of HRVA (B=6.964, p.001), Goel type A (B=-1.656, p=.003), and Goel type B (B=0.981, p=.030). Moreover, cephalad angle was significantly associated with the length of lateral mass (B=-0.319, p=.001) and the diagnoses of HRVA (B=3.254, p.001) and Goel type A (B=6.924, p.001). The VA anomalies were significantly higher in the BI group than in the control group.The insertion parameters of the ideal entry point and trajectory for C2 screw placement in BI patients with HRVA were remarkably different from those of non-HRVA of BI, HRVA of control, and non-HRVA of control cohorts. Preoperative 3D computed tomography (CT) and CT angiography are highly recommended in such patients to improve intraoperative safety and reduce postoperative complications.

Pedicular screws (PS) often are used in lumbar fusion. Cortical bone trajectory (CBT) is a novel technology in lumbar fusion with less evidence of clinical outcomes. Therefore, we conducted a meta-analysis to compare the efficacy and safety between CBT screw fixation and traditional PS in lumbar fusion surgery.Multiple databases were searched for the articles that compared CBT and traditional PS in lumbar fusion surgeries. Meta-analysis was conducted by RevMan 5.3 software. The following indicators were abstracted: visual analog scale (VAS) scores for back and leg pain, Oswestry Disability Index (ODI), Japanese Orthopaedic Association (JOA) score, surgical duration, complications, and blood loss. The quality of the articles was assessed by the Newcastle-Ottawa Scale or Cochrane Handbook.In total, 25 studies were included, involving a total of 1735 patients. There was no difference in preoperative VAS scores, JOA, ODI, postoperative VAS scores, and fusion rates. In addition, postoperative JOA (mean difference [MD] = 0.78, P = 0.02), ODI (MD = -2.09, P = 0.03), surgical duration (MD = -26.90, P = 0.02), complications (MD = 0.70, P = 0.03), and blood loss (MD = -85.27, P = 0.0009) showed greater improvement trends in the CBT group than the PS group, with significant difference.CBT reduced the rate of complications, surgical duration, blood loss, postoperative ODI, and JOA scores. The CBT technique, with better postoperative outcomes, achieved similar fusion rates compared with the PS technique.

To provide definitions and a conceptual framework for single position surgery (SPS) applied to circumferential fusion of the lumbar spine.Narrative literature review and experts' opinion.Two major limitations of lateral lumbar interbody fusion (LLIF) have been (a) a perceived need to reposition the patient to the prone position for posterior fixation, and (b) the lack of a robust solution for fusion at the L5/S1 level. Recently, two strategies for performing single-position circumferential lumbar spinal fusion have been described. The combination of anterior lumbar interbody fusion (ALIF) in the lateral decubitus position (LALIF), LLIF and percutaneous pedicle screw fixation (pPSF) in the lateral decubitus position is known as lateral single-position surgery (LSPS). Prone LLIF (PLLIF) involves transpsoas LLIF done in the prone position that is more familiar for surgeons to then implant pedicle screw fixation. This can be referred to as prone single-position surgery (PSPS). In this review, we describe the evolution of and rationale for single-position spinal surgery. Pertinent studies validating LSPS and PSPS are reviewed and future questions regarding the future of these techniques are posed. Lastly, we present an algorithm for single-position surgery that describes the utility of LALIF, LLIF and PLLIF in the treatment of patients requiring AP lumbar fusions.Single position surgery in circumferential fusion of the lumbar spine includes posterior fixation in association with any of the following: lateral position LLIF, prone position LLIF, lateral position ALIF, and their combination (lateral position LLIF+ALIF). Preliminary studies have validated these methods.

Navigation systems for spinal fusion surgery rely on intraoperative computed tomography (CT) or fluoroscopy imaging. Both expose patient, surgeons and operating room staff to significant amounts of radiation. Alternative methods involving intraoperative ultrasound (iUS) imaging have recently shown promise for image-to-patient registration. Yet, the feasibility and safety of iUS navigation in spinal fusion have not been demonstrated.To evaluate the accuracy of pedicle screw insertion in lumbar and thoracolumbar spinal fusion using a fully automated iUS navigation system.Prospective porcine cadaver study.Five porcine cadavers were used to instrument the lumbar and thoracolumbar spine using posterior open surgery. During the procedure, iUS images were acquired and used to establish automatic registration between the anatomy and preoperative CT images. Navigation was performed with the preoperative CT using tracked instruments. The accuracy of the system was measured as the distance of manually collected points to the preoperative CT vertebral surface and compared against fiducial-based registration. A postoperative CT was acquired, and screw placements were manually verified. We report breach rates, as well as axial and sagittal screw deviations.A total of 56 screws were inserted (5.50 mm diameter n=50, and 6.50 mm diameter n=6). Fifty-two screws were inserted safely without breach. Four screws (7.14%) presented a medial breach with an average deviation of 1.35±0.37 mm (all2 mm). Two breaches were caused by 6.50 mm diameter screws, and two by 5.50 mm screws. For vertebrae instrumented with 5.50 mm screws, the average axial diameter of the pedicle was 9.29 mm leaving a 1.89 mm margin in the left and right pedicle. For vertebrae instrumented with 6.50 mm screws, the average axial diameter of the pedicle was 8.99 mm leaving a 1.24 mm error margin in the left and right pedicle. The average distance to the vertebral surface was 0.96 mm using iUS registration and 0.97 mm using fiducial-based registration.We successfully implanted all pedicle screws in the thoracolumbar spine using the ultrasound-based navigation system. All breaches recorded were minor (2 mm) and the breach rate (7.14%) was comparable to existing literature. More investigation is needed to evaluate consistency, reproducibility, and performance in surgical context.Intraoperative US-based navigation is feasible and practical for pedicle screw insertion in a porcine model. It might be used as a low-cost and radiation-free alternative to intraoperative CT and fluoroscopy in the future.

Augmented reality (AR) is a novel technology with broadening applications to neurosurgery. In deformity spine surgery, it has been primarily directed to the more precise placement of pedicle screws. However, AR may also be used to generate high fidelity three-dimensional (3D) spine models for cases of advanced deformity with existing instrumentation. We present a case in which an AR-generated 3D model was used to facilitate and expedite the removal of embedded instrumentation and guide the reduction of an overriding spondyloptotic deformity.A young adult with a remote history of a motor vehicle accident treated with long-segment posterior spinal stabilization presented with increasing back pain and difficulty sitting upright in a wheelchair. Imaging revealed pseudoarthrosis with multiple rod fractures resulting in an overriding spondyloptosis of T6 on T9. An AR-generated 3D model was useful in the intraoperative localization of rod breaks and other extensively embedded instrumentation. Real-time model thresholding expedited the safe explanation of the defunct system and correction of the spondyloptosis deformity.An AR-generated 3D model proved instrumental in a revision case of hardware failure and high-grade spinal deformity.

To compare the safety and efficacy of posterior internal fixation with open vertebroplasty (VP) and posterior internal fixation with open kyphoplasty (KP) in the treatment of metastatic epidural spinal cord compression (MESCC) with posterior wall destruction.This retrospective study, conducted between January 2016 and May 2019, equally divided 60 patients with MESCC and posterior wall destruction into two groups based on the surgical method: open vertebroplasty with pedicle screw fixation (VP group) and open kyphoplasty with pedicle screw fixation (KP group). Visual analogue scale (VAS), SF-36 scores, middle vertebral height (MVH), and posterior vertebral height (PVH) were evaluated for the two groups preoperatively, postoperatively, and 1 year after surgery. Spinal Instability Neoplastic Score, Frankel grades and complications were recorded and evaluated.Five patients were excluded from the analysis, and our study cohort consisted of 55 adult patients who met the inclusion criteria. The VAS and SF-36 scores of these two groups of patients significantly improved, when compared with those before the surgery (P 0.05). There were significant differences in total cost (8835 ± 1468 vs 9540 ± 053 USD) and cement volume (4.51 ± 0.96 ml vs 6.35 ± 1.09 ml) between two groups (P 0.05). The MVH and PVH of these two groups of patients significantly improved, when compared with those before the surgery (P 0.05). The MVH was significantly larger in the KP group than in the VP group postoperatively (20.15 ± 4.86 vs 17.70 ± 3.78, P 0.05) and at the final follow-up (20.42 ± 5.59 vs 17.28 ± 3.23, P 0.05). However, the PVH of the two groups did not significantly differ at the two postoperative follow-ups (P 0.05). No significant differences were found in surgery time, time from surgery to discharge, blood loss and complications between both groups postoperatively (P 0.05).In the short term, both approaches are effective and safe in patients with MESCC and posterior wall destruction. The posterior internal fixation with open VP may be a good choice of surgical method in patients with MESCC and posterior wall defects.

Retrospective Single-Center Review of Data at a Level 1 Trauma Center.Compare deformity correction and surgical outcomes of percutaneous instrumentation and open fusion in traumatic thoracolumbar fractures.In our retrospective study, all patients undergoing elective spine surgery for TL fractures at a Level 1 trauma center between 2000 and 2017 were reviewed. Patients who underwent percutaneous fixation were given the option of hardware removal after the fracture had healed.A total of 185 patients were included in the study, with 109 treated with an open fusion, and 76 with percutaneous fixation. Twenty-five patients in the latter group had the instrumentation removed after the fracture had healed. None of them required reoperation. In the open fusion group 54.1% of patients required a decompressive laminectomy. Percutaneous fixation patients had a shorter operative time (98.3 min vs 214 min, p 0.0001), shorter length of stay (9.8 days vs 13.5 days, p = 0.04), and less blood loss (68.4 cc vs 691 cc, p 0.001). They also had a better correction of their traumatic kyphosis after surgery (p = 0.005).Percutaneous fixation is a valuable option for the treatment of TL fractures in cases without evidence of neural compression. It is still unclear whether hardware removal helps prevent adjacent segment degeneration. Percutaneous fixation could allow for better reduction of the fracture with improvement of postoperative alignment.

Purpose The present study aimed to assess the feasibility, safety and accuracy of navigated spinopelvic fixation with focus on S2-alar-iliac screws (S2AIS) and tricortical S1 pedicle screw implantation with the use of high-resolution three-dimensional intraoperative imaging and real-time spinal navigation. Methods Patients undergoing navigated intraoperative CT-based spinopelvic stabilization between January 2016 and September 2019 were included. Pelvic fixation was achieved by implantation of S2AIS or iliac screws (IS). S1 screws were implanted with the goal of achieving tricortical purchase. In all cases, instrumentation was performed with real-time spinal navigation and intraoperative screw positioning was assessed using intraoperative computed tomography (iCT), cone-beam CT (CBCT) and robotic cone-beam CT (rCBCT). Screw accuracy was evaluated based on radiographic criteria. To identify predictors of complications, univariate analysis was performed. Results Overall, 52 patients (85%) received S2AIS and nine patients (15%) received IS instrumentation. Intraoperative imaging and spinal navigation were performed with iCT in 34 patients, CBCT in 21 patients and rCBCT in six patients. A total number of 10/128 (7.8%) iliac screws underwent successful intraoperative correction due to misalignment. Tricortical purchase was successfully accomplished in 58/110 (53%) of the S1 screws with a clear learning curve in the course of time. S2AIS implantation was associated with significantly fewer surgical side infection-associated surgeries. Conclusions Real-time navigation facilitated spinopelvic instrumentation with increasing accuracy of S2AIS and tricortical S1 screws. Intraoperative imaging by iCT, CBCT or rCBCT permitted screw assessment with the chance of direct navigated revision of misplaced iliac screws to avoid secondary screw revision surgery.

Occipitocervical junction (OCJ) instability is commonly treated with fixation via open posterior approach. The use of intraoperative navigation allows us to perform occipitocervical fixation via minimally invasive approach. We report a series of patients treated with percutaneous occipitocervical fixation, describing the surgical procedure in detail and discussing the technique.We prospectively enrolled 8 patients affected by OCJ instability secondary to trauma and rheumatoid arthritis. Traumatic patients were preoperatively evaluated with CT scan and MRI scan if needed. Rheumatoid arthritis group was evaluated with both CT and MR. Patients underwent percutaneous occipitocervical fixation with the assist of intraoperative 3D imaging and navigation. All patients were functionally and radiologically evaluated pre-, at 6 weeks, and at 1 year postoperatively.Percutaneous occipitocervical fixation was successfully performed in all of the patients. 33 screws were placed. 29 (87.88%) were placed without any pedicle breach. In 3 (9.09%) screws we observed a minor; and in 1 (3.03%) screw we observed a major pedicle breach. We did not have any postoperative complications.Described method of occipitocervical fixation is a minimally invasive method that has a similar outcome to the open technique. It requires the experience in open techniques and the assist of intraoperative 3D imaging and navigation to be performed efficiently.

Clinical retrospective cohort study.To explore the application of the electromagnetic navigation system in Endo-TLIF.From May 2019 to March 2020, 76 patients with single-segment lumbar spondylolisthesis treated by electromagnetic navigation-assisted Endo-TLIF (NE group) and conventional Endo-TLIF (CE group) were enrolled in the study. Time of pedicle screw implantation, entire operation time, the number of intraoperative X-ray fluoroscopy exposures, total blood loss, incision length, ambulation time, accuracy of pedicle screws, complications, visual analog scale for back and leg pain, Oswestry Disability Index, Japanese Orthopedic Association score and postoperative fusion rates were recorded, respectively.There were no significant differences in preoperative demographics between the NE and CE groups (P 0.05). The mean number of intraoperative X-ray fluoroscopy exposures, guidewires insertion, entire operation time, total blood loss and adjustment rate of screws in the NE group were significantly less compared with the CE group (P 0.05, respectively). There were no significant differences in clinical parameters between the two groups at different time points in the follow-up period (P 0.05). There was no statistical difference in fusion rates between the two groups. In addition, one case of cage subsidence was observed after surgery in the CE group.Electromagnetic navigation systems could be applied throughout the entire surgical course and ameliorate the shortcomings of the conventional Endo-TLIF technique to reduce radiation exposure, improve accuracy, avoid repetitive operations and shorten surgery time and the required learning curve of the procedure.Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Posterior spinal fusion with pedicle screws is commonly used for the treatment of adolescent idiopathic scoliosis (AIS). To reduce radiation exposure, methods other than computed tomography (CT) are desirable for preoperative determination of pedicle diameter.Investigate the differences between magnetic resonance imaging (MRI) and CT measurements of pedicle diameter.Cross-sectional research.Twenty-one AIS Lenke type 1 patients (19 female and 2 males, mean age at surgery: 15.4 years) who underwent posterior spinal fusion between April 2009 and October 2019.Gap between CT and MRI pedicle diameters.The inner and outer diameters of the right and left pedicles from T1 to L3 were measured separately by two spine surgeons for statistical comparisons.The respective minimum and maximum CT-MRI values were -3.7 mm and 4.7 mm for inner diameter and -4.6 mm and 5.3 mm for outer diameter. Regarding inter-examiner error, the probability of a 2 mm difference in measurement was less than 5% for both modalities. The probability of a 1 mm difference was also less than 5%, and that of a 3 mm or more difference was 2.1% for the inner diameter and 2.9% for the outer diameter. Whereas low body weight was significantly associated with measurement differences, pedicle laterality was not.MRI does not have the reliability to measure pedicle size in AIS patients at present. However, with advancements in image processing technology, the accuracy of pedicle size measurement by MRI may soon improve.

Stereotactic intraoperative computer-assisted navigation has been shown to improve pedicle screw accuracy in spinal fusion surgery, but evidence of impact of navigation on clinical outcomes is lacking. The aim of this study is to compare rates of perioperative complications between navigated and nonnavigated procedures for deformity correction.An administrative database was queried for adult patients undergoing thoracolumbar fusion procedures for deformity. Nonelective cases and those involving malignancy, infection, or trauma were excluded. Individuals were divided into 2 cohorts based on the use of stereotactic intraoperative navigation and paired 1:1 for comparison based on a propensity score matching algorithm. Rates of unplanned reoperation and other perioperative complications were compared between matched groups. A multivariable Cox regression model was constructed to identify the impact of navigation on specific subgroups.A total of 6150 patients met eligibility criteria for the study; after propensity score matching, 456 patients who underwent conventional fusion were matched to 456 patients receiving intraoperative navigation. Navigated cases took an average of 30 minutes longer than nonnavigated cases. There were no significant differences in rates of complications between cohorts. A subgroup analysis revealed that use of navigation was associated with decreased hazard for reoperation in individuals undergoing interbody fusion.Despite increased surgical duration, the use of navigation does not seem to significantly impact rates of perioperative complications outside of procedures involving interbody fusion. Surgeons should elect to use navigation in cases expected to be of high operative complexity at their own discretion.

We sought to evaluate the accuracy of using patient-specific drill guides to place bilateral laminar screws in C1 and C2.Nine cervical specimens (8 males; mean age: 66.6 [56-73]) with the occiput attached (C0-C3) were used in this study. Preoperative computed tomography (CT) scans were used to create digital anatomic models for templating and guide creation. A total of 36 screws were placed with the aid of 3-dimensional printed, patient-specific guides (2 screws at C1 and C2). Postoperative CT scans were performed following screw insertion. The planned and actual trajectories were compared using preoperative and postoperative imaging based on the angular and entry point deviation. After screw placement and postoperative imaging, each specimen was dissected and performed a visual inspection for breaches.No breaches or violations were observed on postprocedural CT and visual inspection. The average variation of the entry point in the X, Y, and Z axes was 0.3 ± 0.28, 0.41 ± 0.38, and 0.29 ± 0.24, respectively. No statistically significant difference (P0.05) was observed between the planned and obtained entry points. There was no significant difference (P0.05) in the deviation analysis between the planned and obtained angles in the axial and coronal planes.The study demonstrates that patient-specific drill guides allow for accurate C1 and C2 bilateral laminar screw placement, with a low risk of cortical breach.

Minimally invasive surgery (MIS) techniques for posterior spine pedicle-screw fusion (PSF) may reduce the AIS surgery invasiveness, although they require a certain degree of patient selection based on the severity of the curve. The aim of this article is to systematically review the Literature to determine efficacy and safety of MIS-PSF in AIS correction, and to compare its outcomes with open-PSF. A systematic search of electronic databases from eligible articles was conducted. Only studies adopting MIS-PSF for AIS were included. Clinical and radiographic outcomes were extracted and summarized. Meta-analyses were performed. P-value 0.05 was considered significant. Thirteen studies for a total of 635 patients ungergoing MIS-PSF were included in this review. Pre-operative Cobb's angle ranged from 48.3°±4.2° to 59.8°±6.6°, coronal correction from 58.1% to 79.1%, average operative time ranged from 252 to 526.8 min, average estimated blood loss from 138.8 ± 50 to 1250 mL. Sixty-seven complications were recorded (9.9%), with 19 revisions (3.8%), resulting similar to those described in Literature using open-PSF. At meta-analysis, MIS-PSF (321 patients) compared to open-PSF (429 patients) showed lower coronal correction (although no statistically significant difference was found), estimated blood loss and length of hospital stay, but higher operative time. No differences in SRS-22, complications and revision rate were found. In conclusion, open-PSF shows a trend towards higher correction in the coronal plane and requires a shorter operative time when compared to MIS-PSF. It remains the gold standard for AIS correction, although MIS-PSF seems to be a viable and promising technique for selected patients. - KEYWORDS: minimally invasive surgery, minimally invasive techniques, adolescent idiopathic scoliosis, posterior spinal fusion, pedicle-screws-only instrumentation.