The Era of Cortical Bone Trajectory Screws in Spine Surgery: A Qualitative Review with Rating of Evidence

Effectiveness and safety of robot-assisted versus fluoroscopy-assisted cortical bone trajectory screw instrumentation in spinal surgery: a systematic review and meta-analysis

Robot-assisted (RA) technology has been shown to be a safe aid in spine surgery, this meta-analysis aims to compare surgical parameters and clinical indexes between robot-assisted cortical bone trajectory (CBT) and fluoroscopy-assisted (FA) cortical bone trajectory in spinal surgery. We searched databases such as PubMed, Web of Science, the Cochrane Library, and the China National Knowledge Infrastructure. The study selection process was guided by the PICOS (Patient/Problem, Intervention, Comparison, Outcome, Study Design) strategy. The risk of bias in non-randomized comparative studies was assessed using the risk of bias in non-randomized studies of interventions (ROBINS-I) tool. We performed this meta-analysis using RevMan 5.3 software (Cochrane Collaboration, Copenhagen, Denmark), and the level of statistical significance was set at P < 0.05. Six articles involving 371 patients and 1535 screws were included in this meta-analysis. RA-CBT outperformed FA-CBT in terms of various parameters, such as accuracy of pedicle screw position (both Gertzbein-Robbins scale and Ding scale), avoidance of superior facet joint violation (FJV), and reduction of neurological injury. Our meta-analysis offered a thorough evaluation of the efficacy and safety of RA-CBT in spinal surgery. The findings revealed that RA-CBT produced statistically significant results in terms of pedicle screw position accuracy and superior facet joint violation prevention. In terms of surgical parameters and clinical indexes, future research and clinical practice should investigate the efficacy of RA-CBT further. The study was registered in the PROSPERO (CRD42023466280).

The effect of the cortical bone trajectory screw fixation and traditional pedicle screw fixation on surgical site wound infection in posterior lumbar fusion wound: A meta-analysis

A meta-analysis investigation was performed to measure the influence of cortical bone trajectory screw fixation (CBTSF) and traditional pedicle screw fixation (TPSF) on surgical site wound infection (SSWI) in posterior lumbar fusion (PLF). A comprehensive literature inspection till February 2023 was applied and 1657 interrelated investigations were reviewed. The 13 chosen investigations enclosed 1195 individuals with PLF in the chosen investigations' starting point, 578 of them were using CBTSF, and 617 were using TPSF. Odds ratio (OR) in addition to 95% confidence intervals (CIs) were utilised to compute the value of the effect of the CBTSF and TPSF on SSWI in PLF by the dichotomous approaches and a fixed or random model. No significant difference was found between individuals using CBTSF and TPSF in SSWI (OR, 0.68; 95% CI, 0.35-1.33, P = .26), superficial SSWI (OR, 0.62; 95% CI, 0.22-1.79, P = .38), and deep SSWI (OR, 0.30; 95% CI, 0.06-1.50, P = .14) in PLF. No significant difference was found between individuals using CBTSF and TPSF in SSWI, superficial SSWI, and deep SSWI in PLF. However, care must be exercised when dealing with its values because of the small sample sizes of several chosen investigations for this meta-analysis and the low number of selected investigations for a certain type of SSWI.

Biomechanical investigation of the hybrid lumbar fixation technique with traditional and cortical bone trajectories in transforaminal lumbar interbody fusion: finite element analysis

OBJECTIVE

To compare the biomechanical performance of the hybrid lumbar fixation technique with the traditional and cortical bone trajectory techniques using the finite element method.

METHODS

Four adult wet lumbar spine specimens were provided by the Department of Anatomy and Research of Xinjiang Medical University, and four L1-S1 lumbar spine with transforaminal lumbar interbody fusion (TLIF) models at L4-L5 segment and four different fixation techniques were established: bilateral traditional trajectory screw fixation (TT-TT), bilateral cortical bone trajectory screw fixation (CBT-CBT), hybrid CBT-TT (CBT screws at L4 and TT screws at L5) and TT-CBT (TT screws at L4 and CBT screws at L5). The range of motion (ROM) of the L4-L5 segment, von Mises stress of cage, internal fixation, and rod were compared in flexion, extension, left and right bending, and left and right rotation.

RESULTS

Compared with the TT-TT group, the TT-CBT group exhibited lower ROM of L4-L5 segment, especially in left-sided bending; the CBT-TT group had the lowest ROM of L4-L5 segment in flexion and extension among the four fixation methods. Compared with the CBT-CBT group, the peak cage stress in the TT-CBT group was reduced by 9.9%, 18.1%, 21.5%, 23.3%, and 26.1% in flexion, left bending, right bending, left rotation, and right rotation conditions, respectively, but not statistically significant (P > 0.05). The peak stress of the internal fixation system in the TT-CBT group was significantly lower than the other three fixation methods in all five conditions except for extension, with a statistically significant difference between the CBT-TT and TT-CBT groups in the left rotation condition (P = 0.017). In addition, compared with the CBT-CBT group, the peak stress of the rod in the CBT-TT group decreased by 34.8%, 32.1%, 28.2%, 29.3%, and 43.0% under the six working conditions of flexion, extension, left bending, left rotation, and right rotation, respectively, but not statistically significant (P > 0.05).

CONCLUSIONS

Compared with the TT-TT and CBT-CBT fixation methods in TLIF, the hybrid lumbar fixation CBT-TT and TT-CBT techniques increase the biomechanical stability of the internal fixation structure of the lumbar fusion segment to a certain extent and provide a corresponding theoretical basis for further development in the clinic.

Clinical outcomes, MRI evaluation and predictive factors of indirect decompression with lateral transpsoas approach for lumbar interbody fusion: a multicenter experience

Introduction

Evaluating the effects of indirect decompression obtained through lateral lumbar interbody fusion (LLIF) by clinical improvements and radiological parameters on MRI scans. Identifying predictors of better decompression and clinical outcome.

Materials and methods

From 2016 to 2019, patients who underwent single- or double-level indirect decompression LLIF were consecutively reviewed. Radiological signs of indirect decompression were evaluated in preoperative and follow-up MRI studies and were subsequently correlated to clinical data, expressed as axial/radicular pain (VAS back/leg), index of disability (Oswestry Disability Index) and clinical severity of lumbar stenosis (Swiss Spinal Stenosis Questionnaire).

Results

72 patients were enrolled. The mean follow-up was 24 months. Differences in vertebral canal area (p &lt; 0.001), height of the foramina (p &lt; 0.001), thickness of the yellow ligament (p = 0.001) and anterior height of the interbody space (p = 0.02) were observed. Older age (p = 0.042), presence of spondylolisthesis (p = 0.042), presence of intra-articular facet effusion (p = 0.003) and posterior height of the implanted cage (p = 0.020) positively affected the increase of the canal area. Change in root canal area (p &lt; 0.001), height of the implanted cage (p = 0.020) and younger age (p = 0.035) were predictive factors of root pain relief, while increased vertebral canal area (p = 0.020) and height of the interbody fusion cage (p = 0.023) positively affected the severity of clinical stenosis.

Conclusions

LLIF indirect decompression showed both clinical and radiological improvements. Presence and degree of spondylolisthesis, presence of intra-articular facet effusion, age of the patient and height of the cage were predictive factors of major clinical improvements.

Residual motion of cortical versus pedicle screw constructs after decompression, interbody fusion and cross-link augmentation

PURPOSE

To compare the residual range of motion (ROM) of cortical screw (CS) versus pedicle screw (PS) instrumented lumbar segments and the additional effect of transforaminal interbody fusion (TLIF) and cross-link (CL) augmentation.

METHODS

ROM of thirty-five human cadaver lumbar segments in flexion/extension (FE), lateral bending (LB), lateral shear (LS), anterior shear (AS), axial rotation (AR), and axial compression (AC) was recorded. After instrumenting the segments with PS (n = 17) and CS (n = 18), ROM in relation to the uninstrumented segments was evaluated without and with CL augmentation before and after decompression and TLIF.

RESULTS

CS and PS instrumentations both significantly reduced ROM in all loading directions, except AC. In undecompressed segments, a significantly lower relative (and absolute) reduction of motion in LB was found with CS 61% (absolute 3.3°) as compared to PS 71% (4.0°; p = 0.048). FE, AR, AS, LS, and AC values were similar between CS and PS instrumented segments without interbody fusion. After decompression and TLIF insertion, no difference between CS and PS was found in LB and neither in any other loading direction. CL augmentation did not diminish differences in LB between CS and PS in the undecompressed state but led to an additional small AR reduction of 11% (0.15°) in CS and 7% (0.05°) in PS instrumentation.

CONCLUSION

Similar residual motion is found with CS and PS instrumentation, except of slightly, but significantly inferior reduction of ROM in LB with CS. Differences between CS and PS in diminish with TLIF but not with CL augmentation.

Three-Dimensional Patient-Matched Template Guides Are Able to Increase Mean Diameter and Length and to Improve Accuracy of Cortical Bone Trajectory Screws: A 5-Year International Experience

OBJECTIVE

To analyze whether significant differences exist between free-hand three-dimensional (3D) planning-guided cortical bone trajectory (CBT) screw placement and 3D-printed template-guided CBT screw positioning in terms of accuracy, size of screws, and potential complications.

METHODS

In this retrospective study, data of adult patients in whom CBT screws were placed for lumbar degenerative pathologies were extracted from a prospectively collected database and analyzed. Patients in whom screws were placed using free-hand 3D planning-guided technique were compared with patients in whom screws were positioned using customized 3D-printed templates. Size of the screws, accuracy, clinical outcomes, and complications were analyzed.

RESULTS

The study evaluated 251 patients (1004 screws). The free-hand 3D planning-guided group included 158 patients (632 screws), and the 3D-printed template-guided group included 93 patients (372 screws). The 3D-printed template-guided group involved screws of larger size from L3 to S1. Differences between the 2 groups in terms of accuracy parameters reached statistical significance (P ≤ 0.05).

CONCLUSIONS

With the use of 3D patient-matched template guides, mean diameter and length of CBT screws could be safely increased due to improved accuracy of screw placement. Based on previous evidence regarding CBT biomechanical properties, these advantages could allow increased fixation strength over traditional convergent pedicle screw trajectories. Further biomechanics studies are needed.

Analysis of Fast-Track Surgery with Pain Care on Postoperative Pain Improvement and Complication Prevention in Perioperative Spine Surgery Patients

Objective

The study aimed to analyze the effect of fast-track surgery with pain care on the improvement of postoperative pain and the prevention of postoperative complications in perioperative spinal surgery patients.

Methods

A total of 126 patients undergoing spinal surgery from January 2021 to September 2021 were chosen as the study population, and the patients were classified into the regular group, the FTS group, and the combined group by random grouping, with 42 cases in each group. Patients in the regular group used routine perioperative care in spine surgery, patients in the FTS group used the FTS care model, and patients in the combined group combined special pain care on the basis of the FTS group. We compared the numeric rating scale (NRS) and pain severity of patients in the three groups post-op, 30 min, 1 h, 3 h, 6 h, and 24 h after surgery; we compared the time to get out of bed, length of stay, and occurrence of postoperative adverse effects in the three groups, compared the incidence of complications in the three groups, and compared the satisfaction of care in the three groups.

Results

The NRS scores at 12 h, 24 h, 48 h, and 72 h post-op in the combined group and FTS group were lower than those in the regular group, and the NRS scores at 12 h and 24 h post-op in the combined group were lower than those in the FTS group (all P < 0.05); the post-op bed activity time, post-op hospitalization time, post-op adverse reaction rate, and post-op complication rate in the combined group and FTS group were shorter or lower than those of the regular group. Nursing satisfaction was higher than that of the regular group, the post-op time to bed activity in the combined group was shorter than that of the FTS group, and nursing satisfaction was higher than that of the FTS group (all P < 0.05).

Conclusion

The use of FTS with pain care interventions helps relieve postoperative pain in perioperative patients in spine surgery, reduce the incidence of post-op adverse effects and complications in patients, accelerate their postoperative recovery, and improve nursing satisfaction.

Obesity and Spine Surgery: A Qualitative Review About Outcomes and Complications. Is It Time for New Perspectives on Future Researches?

STUDY DESIGN

Literature review.

OBJECTIVES

An increasing number of obese patients requires operative care for degenerative spinal disorders. The aim of this review is to analyze the available evidence regarding the role of obesity on outcomes after spine surgery. Peri-operative complications and clinical results are evaluated for both cervical and lumbar surgery. Furthermore, the contribution of MIS techniques for lumbar surgery to play a role in reducing risks has been analyzed.

METHODS

Only articles published in English in the last 10 years were reviewed. Inclusion criteria of the references were based on the scope of this review, according to PRISMA guidelines. Moreover, only paper analyzing obesity-related complications in spine surgery have been selected and thoroughly reviewed. Each article was classified according to its rating of evidence using the Sacket Grading System.

RESULTS

A total number of 1636 articles were found, but only 130 of them were considered to be relevant after thorough evaluation and according to PRISMA checklist. The majority of the included papers were classified according to the Sacket Grading System as Level 2 (Retrospective Studies).

CONCLUSION

Evidence suggest that obese patients could benefit from spine surgery and outcomes be satisfactory. A higher rate of peri-operative complications is reported among obese patients, especially in posterior approaches. The use of MIS techniques plays a key role in order to reduce surgical risks. Further studies should evaluate the role of multidisciplinary counseling between spine surgeons, nutritionists and bariatric surgeons, in order to plan proper weight loss before elective spine surgery.

Minimally Invasive Spine Surgery: An Overview

Spinal surgery is undergoing a major transformation toward a minimally invasive paradigm. This shift is being driven by multiple factors, including the need to address spinal problems in an older and sicker population, as well as changes in patient preferences and reimbursement patterns. Increasingly, minimally invasive surgical techniques are being used in place of traditional open approaches due to significant advancements and implementation of intraoperative imaging and navigation technologies. However, in some patients, due to specific anatomic or pathologic factors, minimally invasive techniques are not always possible. Numerous algorithms have been described, and additional efforts are underway to better optimize patient selection for minimally invasive spinal surgery (MISS) procedures in order to achieve optimal outcomes. Numerous unique MISS approaches and techniques have been described, and several have become fundamental. Investigators are evaluating combinations of MISS techniques to further enhance the surgical workflow, patient safety, and efficiency.

Accuracy and safety of robot-assisted cortical bone trajectory screw placement: a comparison of robot-assisted technique with fluoroscopy-assisted approach

Objective

To compare the safety and accuracy of cortical bone trajectory screw placement between the robot-assisted and fluoroscopy-assisted approaches.

Methods

This retrospective study was conducted between November 2018 and June 2020, including 81 patients who underwent cortical bone trajectory (CBT) surgery for degenerative lumbar spine disease. CBT was performed by the same team of experienced surgeons. The patients were randomly divided into two groups—the fluoroscopy-assisted group (FA, 44 patients) and the robot-assisted group (RA, 37 patients). Robots for orthopedic surgery were used in the robot-assisted group, whereas conventional fluoroscopy-guided screw placement was used in the fluoroscopy-assisted group. The accuracy of screw placement and rate of superior facet joint violation were assessed using postoperative computed tomography (CT). The time of single screw placement, intraoperative blood loss, and radiation exposure to the surgical team were also recorded. The χ² test and Student’s t-test were used to analyze the significance of the variables (P < 0.05).

Results

A total of 376 screws were inserted in 81 patients, including 172 screws in the robot-assisted group and 204 pedicle screws in the fluoroscopy-assisted group. Screw placement accuracy was higher in the RA group (160, 93%) than in the FA group (169, 83%) (P = 0.003). The RA group had a lower violation of the superior facet joint than the FA group. The number of screws reaching grade 0 in the RA group (58, 78%) was more than that in the FA group (56, 64%) (P = 0.041). Screw placement time was longer in the FA group (7.25 ± 0.84 min) than in the RA group (5.58 ± 1.22 min, P < 0.001). The FA group had more intraoperative bleeding (273.41 ± 118.20 ml) than the RA group (248.65 ± 97.53 ml, P = 0.313). The radiation time of the FA group (0.43 ± 0.07 min) was longer than the RA group (0.37 ± 0.10 min, P = 0.001). Furthermore, the overall learning curve tended to decrease.

Conclusions

Robot-assisted screw placement improves screw placement accuracy, shortens screw placement time, effectively improves surgical safety and efficiency, and reduces radiation exposure to the surgical team. In addition, the learning curve of robot-assisted screw placement is smooth and easy to operate.

Clinical and radiographic performance of indirect foraminal decompression with anterior retroperitoneal lumbar approach for interbody fusion (ALIF)

STUDY DESIGN

Retrospective study BACKGROUND: Indirect decompression with ALIF allows the restoration of the disk and foraminal height with limited soft tissue damage. However, it does not offer a direct view of the neural structure and a direct intraoperative assessment of the results of the decompression is not possible. For this reason, ALIF is often accompanied by posterior, direct decompression. So far, there is no consensus on the effects of indirect decompression alone for L5-S1 foraminal stenosis.

OBJECTIVE

Evaluation of the clinical and mechanical performance of indirect decompression with anterior lumbar interbody fusion (ALIF) in L5-S1 foraminal stenosis.

METHODS

All patients who underwent ALIF at our institution and had a minimum follow-up of six months were assessed for inclusion. Radiographic parameters (anterior and posterior disc height, foraminal height and surface, L5-S1 angle, pelvic incidence, pelvic tilt and lumbar lordosis) and clinical data (Oswestry Disability Index - ODI and Numeric Rating Scale - NRS) before ALIF and at the last follow-up were compared. A regression analysis was performed to investigate the correlation between radiographic and clinical outcomes.

RESULTS

Thirty-four patients were available for the study (55.9% female, mean age 53.4±11.5 years), mean follow-up was 26.4±11.1 months. At the last follow-up, a significant increase in foraminal height (14.6±4.0 vs. 17.9±3.9 mm, p<0.001), posterior disc height (6.5±2 vs. 9.1±2 mm, p<0.001) was observed. ODI and NRS back and leg improved significantly. The NRS leg correlated with foraminal height (r=-0.45), foraminal surface (r=-0.36) and anterior (r=-0.41) and posterior disc height (r=-0.43).

CONCLUSION

ALIF provided significant indirect foraminal decompression and improvement of radicular pain. The increase of foraminal height, surface, and posterior disc height is directly associated with radicular pain improvement.

LEVEL OF EVIDENCE

IV AVAILABILITY OF DATA AND MATERIAL: The datasets used and/or analyzed in the present study are available from the corresponding author on reasonable request.

Adjacent-segment effects of lumbar cortical screw-rod fixation versus pedicle screw-rod fixation with and without interbody support

OBJECTIVE

Cortical screw-rod (CSR) fixation has emerged as an alternative to the traditional pedicle screw-rod (PSR) fixation for posterior lumbar fixation. Previous studies have concluded that CSR provides the same stability in cadaveric specimens as PSR and is comparable in clinical outcomes. However, recent clinical studies reported a lower incidence of radiographic and symptomatic adjacent-segment degeneration with CSR. No biomechanical study to date has focused on how the adjacent-segment mobility of these two constructs compares. This study aimed to investigate adjacent-segment mobility of CSR and PSR fixation, with and without interbody support (lateral lumbar interbody fusion [LLIF] or transforaminal lumbar interbody fusion [TLIF]).

METHODS

A retroactive analysis was done using normalized range of motion (ROM) data at levels adjacent to single-level (L3-4) bilateral screw-rod fixation using pedicle or cortical screws, with and without LLIF or TLIF. Intact and instrumented specimens (n = 28, all L2-5) were tested using pure moment loads (7.5 Nm) in flexion, extension, lateral bending, and axial rotation. Adjacent-segment ROM data were normalized to intact ROM data. Statistical comparisons of adjacent-segment normalized ROM between two of the groups (PSR followed by PSR+TLIF [n = 7] and CSR followed by CSR+TLIF [n = 7]) were performed using 2-way ANOVA with replication. Statistical comparisons among four of the groups (PSR+TLIF [n = 7], PSR+LLIF [n = 7], CSR+TLIF [n = 7], and CSR+LLIF [n = 7]) were made using 2-way ANOVA without replication. Statistical significance was set at p < 0.05.

RESULTS

Proximal adjacent-segment normalized ROM was significantly larger with PSR than CSR during flexion-extension regardless of TLIF (p = 0.02), or with either TLIF or LLIF (p = 0.04). During lateral bending with TLIF, the distal adjacent-segment normalized ROM was significantly larger with PSR than CSR (p < 0.001). Moreover, regardless of the types of screw-rod fixations (CSR or PSR), TLIF had a significantly larger normalized ROM than LLIF in all directions at both proximal and distal adjacent segments (p ≤ 0.04).

CONCLUSIONS

The use of PSR versus CSR during single-level lumbar fusion can significantly affect mobility at the adjacent segment, regardless of the presence of TLIF or with either TLIF or LLIF. Moreover, the type of interbody support also had a significant effect on adjacent-segment mobility.

Fluoroscopic versus CT-guided cortical bone trajectory pedicle screw fixation: Comparing trajectory related complications

Cortical bone trajectory (CBT) pedicle screw fixation is an emerging technique for treatment of degenerative spine disease which requires either intraoperative fluoroscopy or intraoperative CT guidance (iCT). To date, there has been no direct comparison of these two navigation modalities; here we compare fluoroscopic versus iCT navigation for CBT pedicle screw fixation. We retrospectively reviewed all patients who underwent CBT screw fixation with either fluoroscopic or iCT guidance for lumbar degenerative disease by the senior author. Trajectory-related complications such as medial or lateral breach were compared on postoperative CT, in addition to the incidence of trajectory-related dural tear. We also compared general surgical complications such as postoperative infection and decompression related durotomies. Thirty-eight patients (19 fluoroscopic, 19 CT-guided) who underwent placement of 182 cortical screws (88 fluoroscopic, 94 CT-guided) were identified. In terms of trajectory-related complications, the iCT cohort had fewer medial breaches (1/94) compared to the fluoroscopic cohort (6/88) (p = 0.05). Each group had one lateral breach (p = 0.73). There was one case of CSF leak from screw placement in the fluoroscopic cohort, but none in the iCT cohort (p = 0.48). Overall, there were eight trajectory-related complications in the fluoroscopic cohort versus two in the iCT cohort (p = 0.04). Our data suggests statistically significant decreased trajectory-related complications with iCT-guided CBT screw fixation as compared to fluoroscopically guided. In terms of general surgical complications, while we observed increased postoperative infections in our fluoroscopic cohort, there was no statistically significant difference.

Augmented Reality in Medical Practice: From Spine Surgery to Remote Assistance

Background: While performing surgeries in the OR, surgeons and assistants often need to access several information regarding surgical planning and/or procedures related to the surgery itself, or the accessory equipment to perform certain operations. The accessibility of this information often relies on the physical presence of technical and medical specialists in the OR, which is increasingly difficult due to the number of limitations imposed by the COVID emergency to avoid overcrowded environments or external personnel. Here, we analyze several scenarios where we equipped OR personnel with augmented reality (AR) glasses, allowing a remote specialist to guide OR operations through voice and ad-hoc visuals, superimposed to the field of view of the operator wearing them.

Methods: This study is a preliminary case series of prospective collected data about the use of AR-assistance in spine surgery from January to July 2020. The technology has been used on a cohort of 12 patients affected by degenerative lumbar spine disease with lumbar sciatica co-morbidities. Surgeons and OR specialists were equipped with AR devices, customized with P2P videoconference commercial apps, or customized holographic apps. The devices were tested during surgeries for lumbar arthrodesis in a multicenter experience involving author's Institutions.

Findings: A total number of 12 lumbar arthrodesis have been performed while using the described AR technology, with application spanning from telementoring (3), teaching (2), surgical planning superimposition and interaction with the hologram using a custom application for Microsoft hololens (1). Surgeons wearing the AR goggles reported a positive feedback as for the ergonomy, wearability and comfort during the procedure; being able to visualize a 3D reconstruction during surgery was perceived as a straightforward benefit, allowing to speed-up procedures, thus limiting post-operational complications. The possibility of remotely interacting with a specialist on the glasses was a potent added value during COVID emergency, due to limited access of non-resident personnel in the OR.

Interpretation: By allowing surgeons to overlay digital medical content on actual surroundings, augmented reality surgery can be exploited easily in multiple scenarios by adapting commercially available or custom-made apps to several use cases. The possibility to observe directly the operatory theater through the eyes of the surgeon might be a game-changer, giving the chance to unexperienced surgeons to be virtually at the site of the operation, or allowing a remote experienced operator to guide wisely the unexperienced surgeon during a procedure.

Application study of three-dimensional printed navigation template between traditional and novel cortical bone trajectory on osteoporosis lumbar spine

To investigate the safety, accuracy and indications of traditional and novel cortical bone screws placement for osteoporosis lumbar spine, 4 lumbar vertebra specimens (2 males and 2 females) were used for this study. After the computed tomography scanning data of the above anatomical specimens were three-dimensional (3D) reconstructed, one side of each anatomical specimen was randomly chosen to place traditional cortical bone screws, and the other side received novel technical placement. The safety screw trajectory was designed, and a 3D navigation template complementary to the surface anatomical structure of lumbar isthmus lateral margin-vertebral plate-spinous process part was established. The designed supporting navigation template was substantialized, and the navigation template replicated different cortical bone screw trajectory at different sides of the same one lumbar vertebra. Forty cortical bone screws were firstly placed in 3D printed vertebra and then 40 were placed in real anatomical specimens. In 3D printed specimens, the success rates of screw placement with navigation template using traditional and novel techniques were both 100%. While in anatomical specimens, the success rate of screw placement using traditional and novel navigation template was 97.5% (one out of 40 went wrong). Therefore, it is safe, accurate and reliable to place traditional and novel cortical bone screws on osteoporosis lumbar spine using 3D printed navigation template. Traditional and novel screw placement methods should be flexibly applied or combined according to specific sequence and form of vertebra.

Management of Extramedullary Intradural Spinal Tumors: The Impact of Clinical Status, Intraoperative Neurophysiological Monitoring and Surgical Approach on Outcomes in a 12-Year Double-Center Experience

Objective: Intradural Extramedullary (IDEM) tumors are usually treated with surgical excision. The aim of this study was to investigate the impact on clinical outcomes of pre-surgical clinical conditions, intraoperative neurophysiological monitoring (IONM), surgical access to the spinal canal, histology, degree of resection and intra/postoperative complications.

Methods: This is a retrospective observational study analyzing data of patients suffering from IDEM tumors who underwent surgical treatment over a 12 year period in a double-center experience. Data were extracted from a prospectively maintained database and included: sex, age at diagnosis, clinical status according to the modified McCormick Scale (Grades I-V) at admission, discharge, and follow-up, tumor histology, type of surgical access to the spinal canal (bilateral laminectomy vs. monolateral laminectomy vs. laminoplasty), degree of surgical removal, use and type of IONM, occurrence and type of intraoperative complications, use of Ultrasonic Aspirator (CUSA), radiological follow-up.

Results: A total number of 249 patients was included with a mean follow-up of 48.3 months. Gross total resection was achieved in 210 patients (84.3%) mostly in Schwannomas (45.2%) and Meningiomas (40.4%). IONM was performed in 162 procedures (65%) and D-wave was recorded in 64.2% of all cervical and thoracic locations (99 patients). The linear regression diagram for McCormick grades before and after surgery (follow-up) showed a correlation between preoperative and postoperative clinical status. A statistically significant correlation was found between absence of worsening of clinical condition at follow-up and use of IONM at follow-up (p = 0.01) but not at discharge. No associations were found between the choice of surgical approach and the extent of resection (p = 0.79), the presence of recurrence or residual tumor (p = 0.14) or CSF leakage (p = 0.25). The extent of resection was not associated with the use of IONM (p = 0.91) or CUSA (p = 0.19).

Conclusion: A reliable prediction of clinical improvement could be made based on pre-operative clinical status. The use of IONM resulted in better clinical outcomes at follow-up (not at discharge), but no associations were found with the extent of resection. The use of minimally invasive approaches such as monolateral laminectomy showed to be effective and not associated with worse outcomes or increased complications.

The C2 Cortical Screw, an Alternative Fixation Technique for the C2 Segment During High Cervical Spine Surgery: Technical Note

BACKGROUND

For posterior fixation of C2 vertebra (the axis), several fixation techniques such as pedicle screw, laminar screw, and pars screw have been reported. A pedicle screw (PS) is considered the strongest among the techniques, but certain situations make PS fixation impossible or difficult. These include patients with a narrow C2 pedicle or high-riding vertebral artery. We introduced an alternative screw technique for C2 that addressed the aforementioned problems with safely placing it, which we termed a cortical screw (CS) for C2.

METHODS

Among a total of 28 cases using C2 CS for high cervical spine surgery, 2 cases using C2 CS were described. One patient was a 76-year old woman with a gait disturbance and myelopathic symptoms and diagnosed with C1-C2 myelopathy and translational instability. The other case was 54-year old man with posterior neck pain after traffic accident and diagnosed with C1-C2 fracture-dislocation. We used the C2 CS as an alternative technique for high cervical spine surgery in these patients and describe the ideal entry point and trajectory.

RESULTS

A postoperative computed tomography scan confirmed proper positioning of the C1 posterior arch screw and C2 CS, with satisfactory reduction of the C2 dens and adequate restoration of the C1-C2 spinal canal. The patient experienced no screw-related postoperative complications, and postoperative 1-year computed tomography images showed that solid union and good alignment of C1-2 segment was achieved.

CONCLUSIONS

C2 CS can be suitable alternative for C2 screw fixation technique in posterior high cervical spine fusion surgery.