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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.

Background Context: Intraoperative detection of a pedicle wall breach implicitly reduces surgical risk, but the reliability of intraoperative neuromonitoring has been contested. Hydroxyapatite has been promulgated to increase pedicle screw resistance and negatively influence the accuracy of electromyography. Purpose: The primary purpose of this experiment is to evaluate the effect of HA on pedicle screw electrical resistance using a controlled laboratory model. Study Design: Controlled Laboratory Study. Methods: Stimulation of pedicle screws was performed in normal saline (0.9% NaCl). The experimental group included eight HA coated (HAC) pedicle screws and matched manufacturer control pedicle screws without HAC (Ti6Al4V). All screws were stimulated at 5, 10-, 15-, 20-, and 25-mm submersion depths. Circuit current return was recorded, and pedicle screw electrical resistance was calculated according to Ohm's Law. Data were assessed for normality and variance. Mann-Whitney U and Kruskal-Wallis tests compared groups with Bonferroni correction for multiple testing. Effect size is reported with 95% confidence intervals (95CI). P-values Results: Current return was detected for all screws (N= 24) following subclinical 8.5 µA stimulation at 5, 10-, 15-, 20-, and 25-mm submersion depths (N=144). The effect estimate of HA on pedicle screw electrical resistance is -0.07 (-0.17-0.01 95CI). The estimated effect of HA on pedicle screw electrical resistance did not differ across manufacturers. Electrical resistance values were inversely related to submersion depth. Electrical resistance values were lower in the experimental group at 10mm (P=0.04), 15mm (P=0.04), and 25mm (P=0.02) submersion depths. The HA effect ranged from -0.03 to -0.08 as submersion depth varied. Conclusion: We found no evidence that HA increased pedicle screw electrical resistance in a matched manufacturer control laboratory model. Clinical Significance: Electrical stimulation of pedicle screws may be reliable for pedicle breach detection in the presence of HA. Future research should investigate if laboratory findings translate to clinical practice and confirm that electrical stimulation of pedicle screws is a reliable method to detect pedicle breach in the presence of HA.

OBJECTIVE Previous reports have focused on the complications of L5 nerve root injury caused by anterolateral misplacement of the S1 pedicle screws. Anatomical knowledge of the L5 nerve root in the pelvis is essential for safe and effective placement of the sacral screw. This cadaveric study aimed to investigate the course of the L5 nerve root in the pelvis and to clarify a safe zone for inserting the sacral screw. METHODS Fifty-four L5 nerve roots located bilaterally in 27 formalin-fixed cadavers were studied. The ventral rami of the L5 nerve roots were dissected along their courses from the intervertebral foramina to the lesser pelvis. The running angles of the L5 nerve roots from the centerline were measured in the coronal plane. In addition, the distances from the ala of the sacrum to the L5 nerve roots were measured in the sagittal plane. RESULTS The authors found that the running angles of the L5 nerve roots changed at the most anterior surface of the ala of the sacrum. The angles of the bilateral L5 nerve roots from the right and left L5 intervertebral foramina to their inflection points were 13.77° ± 5.01° and 14.65° ± 4.71°, respectively. The angles of the bilateral L5 nerve roots from the right and left inflection points to the lesser pelvis were 19.66° ± 6.40° and 20.58° ± 5.78°, respectively. There were no significant differences between the angles measured in the right and left nerve roots. The majority of the L5 nerves coursed outward after changing their angles at the inflection point. The distances from the ala of the sacrum to the L5 nerve roots in the sagittal plane were less than 1 mm in all cases, which indicated that the L5 nerve roots were positioned close to the ala of the sacrum and had poor mobility. CONCLUSIONS All of the L5 nerve roots coursed outward after exiting the intervertebral foramina and never inward. To prevent iatrogenic L5 nerve root injury, surgeons should insert the S1 pedicle screw medially with an angle > 0° toward the inside of the S1 anterior foramina and the sacral alar screw laterally with an angle > 30°.

This study presents a nondestructive technique to assess the influence of accessory rods and connectors on the mechanical response of spine fixation. Eighteen spine specimens were divided into three construct groups such as group I (2 rods [2R]), II (2 primary rods + 2 accessory rods with 2 transverse connectors [4R + 2TC]) and III (2 primary rods + 2 accessory rods with 4 transverse connectors [4R + 4TC]). Anterior corpectomy was performed for all specimens. A custom test setup was built to assess the dynamic responses of constructs in flexion-extension (FE) and left-right lateral bending (LRLB) motions. This setup can slide in lateral direction, and it is excited with an electrodynamic shaker vibrated at band limited random frequencies. Accelerometer and reusable dynamic strain sensors were installed on constructs to monitor the dynamic responses. Quasi-static eccentric loading tests were performed to determine the range of motion (RoM). The results demonstrated that accessory rods significantly increase the resonance frequency (RF) and decrease the strain over standard 2R construction. Although 4R + 4TC provided greatest reduction in rod strain over 4R + 2TC and 2R, additional 2 connectors have no significant influence on dynamic response in FE motion. The findings suggest that 4R + 4TC has a role in the improvement of the fixation's integrity in FE and LRLB motions. However, the additional transverse connectors have significant involvements only in LRLB motion. Hence, the 4R + 4TC configuration is useful for a construct that is subjected to high LRLB moment, as well as excessive compressive stress and fatigue. Furthermore, RF obtained from dynamic tests correlated with the RoM which indicates that the technique could be used as an addendum to the quasi-static test.

OBJECTIVE Augmented reality (AR) is a novel technology which, when applied to spine surgery, offers the potential for efficient, safe, and accurate placement of spinal instrumentation. The authors report the accuracy of the first 205 pedicle screws consecutively placed at their institution by using AR assistance with a unique head-mounted display (HMD) navigation system. METHODS A retrospective review was performed of the first 28 consecutive patients who underwent AR-assisted pedicle screw placement in the thoracic, lumbar, and/or sacral spine at the authors’ institution. Clinical accuracy for each pedicle screw was graded using the Gertzbein-Robbins scale by an independent neuroradiologist working in a blinded fashion. RESULTS Twenty-eight consecutive patients underwent thoracic, lumbar, or sacral pedicle screw placement with AR assistance. The median age at the time of surgery was 62.5 (IQR 13.8) years and the median body mass index was 31 (IQR 8.6) kg/m2. Indications for surgery included degenerative disease (n = 12, 43%); deformity correction (n = 12, 43%); tumor (n = 3, 11%); and trauma (n = 1, 4%). The majority of patients (n = 26, 93%) presented with low-back pain, 19 (68%) patients presented with radicular leg pain, and 10 (36%) patients had documented lower extremity weakness. A total of 205 screws were consecutively placed, with 112 (55%) placed in the lumbar spine, 67 (33%) in the thoracic spine, and 26 (13%) at S1. Screw placement accuracy was 98.5% for thoracic screws, 97.8% for lumbar/S1 screws, and 98.0% overall. CONCLUSIONS AR depicted through a unique HMD is a novel and clinically accurate technology for the navigated insertion of pedicle screws. The authors describe the first 205 AR-assisted thoracic, lumbar, and sacral pedicle screws consecutively placed at their institution with an accuracy of 98.0% as determined by a Gertzbein-Robbins grade of A or B.

OBJECTIVE The aim of this study was to evaluate the clinical outcomes and the coronal correction rate of the main and accompanying curves of adolescent idiopathic scoliosis (AIS) corrected with pedicle screws inserted consecutively or intermittently. METHODS The prospectively collected data of 60 patients (8 men and 52 women; mean age: 14.6±2.5 years) who underwent corrective surgery for AIS between January 2010 and December 2015 were reviewed retrospectively. Two groups were constituted according to the pedicle screw construct type: consecutive pedicle screw construct (CPSC) and intermittent pedicle screw construct (IPSC) groups. The preoperative, early postoperative, and 24-month follow-up radiographs and the Scoliosis Research Society-22 (SRS-22) scores were reevaluated. The Cobb angle of the main and accompanying curves, the correction rate, and the flexibility of the curves were calculated. RESULTS The mean preoperative Cobb angles were 57.03° and 57.46°, the mean postoperative Cobb angles were 14.93° and 14.4°, and the mean correction rates were 76.22% and 75.31% in IPSC and CPSC groups, respectively (p>0.05). The preoperative and postoperative accompanying curve magnitudes and correction rates were similar (p>0.05). These radiographic outcomes were also consistent with the SRS-22 scores. CONCLUSION Both the pedicle screw constructs had satisfactory outcomes following the surgery, which were confirmed by both the SRS-22 scores and radiographs taken perioperatively and at follow-ups. The IPSC and CPSC groups did not demonstrate a significant change in the correction rate of the main and minor or major accompanying structural and nonstructural curves, and also in the SRS-22 scores. LEVEL OF EVIDENCE Level III, Retrospective comparative study.

A screw-rod system is the most widely used technique for atlantoaxial instability (AAI). However, neglecting anomalies of the vertebral artery and axis could lead to fatal complications. Whether or not the presence of AAI is associated with a more complicated anatomy for instrumentation is unclear.To analyze the association between AAI and anomalies of the vertebral artery and axis in patients with and without AAI.A retrospective comparative study.One hundred and twenty patients who underwent preoperative 3-dimensional computed tomography with vertebral angiography of the cervical spine at our institution from 2012 to 2020.The C2 isthmus height, internal height of the C2 lateral mass, and C2 pedicle width were radiologically assessed.A case control study with matched cohort analysis was conducted. One hundred and twenty patients were divided into 2 groups according to presence of AAI, and the presence of high-riding vertebral artery (HRVA) and a narrow pedicle for insertion of the C2 pedicle screw was assessed, as was the prevalence of extraosseous vertebral artery anomaly.The C2 isthmus height, C2 internal height, and C2 pedicle width were significantly narrower in the AAI group (p.01,.01, and.01, respectively). A significantly greater proportion of patients with AAI had HRVA and a narrow pedicle than those without (p.01 and0.01, respectively). Among patients with AAI, the C2 internal height was significantly narrower in patients with rheumatoid arthritis (p.01). Five patients (8.3%) with AAI had vertebral artery anomaly (3 fenestration, 2 persistent first intersegmental artery), while there were no vertebral artery anomalies in patients without AAI (p.01).Vertebral artery anomalies are more common in patients with AAI. Furthermore, posterior instrumentation in patients with AAI has a narrower safe zone compared to that in patients without AAI, which may be caused by a long-lasting deformity rather than a congenital deformity. Therefore, more thorough preoperative evaluation of the anatomy should be performed in these patients.

Cortical bone trajectory (CBT) for posterior fixation with pedicle screws is considered a relatively new alternative trajectory that travels in the medio-lateral direction in the transverse plane and in the caudo-cephalad path in the sagittal plane. Various biomechanical studies have already validated its superior pullout strength and mechanical stability over the traditional trajectory of convergent pedicle screws. Due to the relatively medial starting point of this trajectory, the CBT also poses the clinical advantage of requiring a smaller surgical field of exposure, thus minimizing tissue and muscle injury while reducing operative time and intraoperative blood loss. The evolution of CBT through time has closely been linked to the unwavering philosophy of prioritizing patient outcomes, advancements in neuronavigational technology, and the mounting biomechanical, morphometric, and clinical evidence. In this historical review, we provide a unique perspective on how CBT surgical technique has developed through time, highlighting key milestones and attempting to explain its explosive rise in popularity.

Objective This study aimed to demonstrate the utility of power tools and intraoperative neuromonitoring of percutaneous pedicle screw (PPS) insertion (so-called PPS monitoring) by SINGLE-position surgery (SPS) after lateral lumbar interbody fusion. Methods A retrospective analysis of medical records from a single center was performed to identify patients who underwent SPS for lateral lumbar interbody fusion and posterior fixation using PPS during intraoperative computed tomography navigation from 2020 to 2021. We investigated the PPS insertion time and screw positional accuracy of patients who underwent SPS involving power tools and PPS monitoring during this period. In this technical note, we report on this surgical technique. Results Twenty-four patients (mean age 72.0 ± 8.5 years, range 53–81 years) were included in this study. There were no intraoperative complications in all cases. Posterior fixation using PPS was added in all cases, and a total of 106 PPSs were inserted. It took an average of 6.2 ± 2.4 seconds to insert the PPS from the PPS insertion point to the end using a power tool and PPS monitoring. Moreover, there were no cases of pedicle breaches. Conclusions Similar to previous reports related to power tools in the prone position, the lateral decubitus SPS technique can also use power tools to save PPS insertion time. Furthermore, we suggest that the use of PPS monitoring may prevent erroneous PPS insertions by using intraoperative computed tomography navigation in advance.

Background Cervical pedicle screws (CPS) in the subaxial cervical spine (C3-C6) are faced with high incidence of perforating the lateral pedicular cortex endangering the vertebral artery (VA). The present study analyzes the pedicle width (PW) from C3 to C6 and defines the relation of VA with regard to pedicle and transverse foramen (TF) to determine the safety margin in cases of lateral pedicular breach. Methods Computed tomography angiograms of 500 patients were retrospectively studied to identify the pedicle width (PW), VA area, TF area, and the lateral pedicle to vertebral artery distance (LPVA). Occupancy ratio (OR; the percentage area of transverse foramen occupied by VA) and safety margin (SM; permissible displacement of VA in TF), along with LPVA were considered to be protective parameters against VA injury if lateral pedicle breach happens. Results PW was 4.7 mm at C3, 4.83 mm at C4, 5.26 mm at C5 and 5.41 mm at C6. Mean LPVA at different levels was between 0.97 mm and 1.15 mm, OR was around 20% at all levels, and mean SM was between 2.34 mm and 2.92 at various levels. Sex differences were statistically significant for PW but not for LPVA, SM, or OR. Conclusions This study gives us an idea about the various parameters in placement of cervical pedicle screw in subaxial cervical spine and the probable reasons there are few vertebral artery injuries despite high incidence of cervical pedicle breach. LPVA, safety margin, and OR may explain why even very significant CPS misplacement does not lead to vascular injury or neurologic deficit.

Purpose : To compare the effectiveness of O-arm navigation with that of conventional fluoroscopic guidance in corrective posterior fixation for cervical spinal injury. Methods : This retrospective comparative study involved 11 consecutive patients who underwent corrective posterior fixation using O-arm navigation or conventional fluoroscopy for cervical spinal injury between February 2016 and May 2021. Patient-specific characteristics (age and sex), number of screws, number of pedicle screws, accuracy of pedicle screw insertion, number of vertebral bodies fixed, operating time, and length of hospital stay were analyzed using the t-test. A P-value 0.05 was considered statistically significant. Results : Corrective posterior fixation was performed under O-arm navigation in 5 patients and under conventional fluoroscopic guidance in 6. A significantly greater number of pedicle screws was used in the O-arm group (6.4 vs 2.7, P = 0.046). According to the Neo classification for pedicle screw placement, there were no grade 2 or 3 breaches. No other items showed a significant difference between the groups (P 0.05). Conclusion : O-arm navigation can improve the accuracy of cervical pedicle screw insertion. Its introduction could expand the indications for use of pedicle screws in posterior fixation of cervical spinal injury beyond those that are possible using conventional fluoroscopy. J. Med. Invest. 69 : 273-277, August, 2022.

BACKGROUND In robot-assisted (RA) spine surgery, the relationship between the surgical outcome and the learning curve remains to be evaluated. AIM To analyze the learning curve of RA pedicle screw fixation (PSF) through fitting the operation time curve based on the cumulative summation method. METHODS RA PSFs that were initially completed by two surgeons at the Beijing Jishuitan Hospital from July 2016 to March 2019 were analyzed retrospectively. Based on the cumulative sum of the operation time, the learning curves of the two surgeons were drawn and fit to polynomial curves. The learning curve was divided into the early and late stages according to the shape of the fitted curve. The operation time and screw accuracy were compared between the stages. RESULTS The turning point of the learning curves from Surgeons A and B appeared in the 18th and 17th cases, respectively. The operation time [150 (128, 188) min vs 120 (105, 150) min, P = 0.002] and the screw accuracy (87.50% vs 96.30%, P = 0.026) of RA surgeries performed by Surgeon A were significantly improved after he completed 18 cases. In the case of Surgeon B, the operation time (177.35 ± 28.18 min vs 150.00 ± 34.64 min, P = 0.024) was significantly reduced, and the screw accuracy (91.18% vs 96.15%, P = 0.475) was slightly improved after the surgeon completed 17 RA surgeries. CONCLUSION After completing 17 to 18 cases of RA PSFs, surgeons can pass the learning phase of RA technology. The operation time is reduced afterward, and the screw accuracy shows a trend of improvement.

PURPOSE OF REVIEW: Imaging technologies (X-ray, CT, MRI, and ultrasound) have revolutionized orthopedic surgery, allowing for the more efficient diagnosis, monitoring, and treatment of musculoskeletal aliments. The current review investigates recent literature surrounding the impact of augmented reality (AR) imaging technologies on orthopedic surgery. In particular, it investigates the impact that AR technologies may have on provider cognitive burden, operative times, occupational radiation exposure, and surgical precision and outcomes. RECENT FINDINGS: Many AR technologies have been shown to lower provider cognitive burden and reduce operative time and radiation exposure while improving surgical precision in pre-clinical cadaveric and sawbones models. So far, only a few platforms focusing on pedicle screw placement have been approved by the FDA. These technologies have been implemented clinically with mixed results when compared to traditional free-hand approaches. SUMMARY: It remains to be seen if current AR technologies can deliver upon their multitude of promises, and the ability to do so seems contingent upon continued technological progress. Additionally, the impact of these platforms will likely be highly conditional on clinical indication and provider type. It remains unclear if AR will be broadly accepted and utilized or if it will be reserved for niche indications where it adds significant value. One thing is clear, orthopedics’ high utilization of pre- and intra-operative imaging, combined with the relative ease of tracking rigid structures like bone as compared to soft tissues, has made it the clear beachhead market for AR technologies in medicine.

Resumen: La artrodesis posterior instrumentada con tornillos pediculares mediante manos libres y con monitorización neurofisiológica intraoperatoria es la técnica quirúrgica más común en cirugía de escoliosis idiopática del adolescente. Una complicación descrita durante este tipo de intervenciones es el neumotórax. La estimulación de los tornillos pediculares es la técnica neurofisiológica empleada para la detección del mal posicionamiento de los mismos y para prevenir lesiones neurológicas iatrogénicas. Presentamos 2 casos clínicos en los que la caída unilateral de los umbrales de los tornillos pediculares se asocia a neumotórax ipsilateral. Para detectar un neumotórax, hay que realizar una radiografía de tórax postoperatoria. Sin embargo, esta práctica ha sido cuestionada debido a la baja incidencia de esta complicación. A raíz de la asociación descrita en este trabajo, consideramos que ante un descenso o asimetría en los umbrales de los tornillos pediculares debemos sospechar y descartar la existencia de un neumotórax. Abstract: Posterior spinal instrumentation and fusion with pedicle screws inserted by free-hand technique and controlled by multimodal intraoperative monitoring is the most common technique in adolescent idiopathic scoliosis surgery. Pneumothorax is a described complication of this kind of procedure. Triggered electromyography is used to identify pedicle wall breakthrough and prevent neurological injuries. We report 2 clinical cases in which unilateral decrease in triggered electromyography values associate with ipsilateral pneumothorax. Postoperative chest radiographs need to be done in order to diagnose a pneumothorax. However, routinely performing a chest radiograph has been questioned because of the low incidence of this surgical complication. As a result of the association described in this article, we consider that when a unilateral decrease in triggered electromyography values is detected, a hidden pneumothorax should be suspected and ruled out.

Background: Pedicle screws provide excellent fixation for a wide range of indications. However, their adoption in the cervical spine has been slower than in the thoracic and lumbar spine, which is largely due to the smaller pedicle sizes and the proximity to the neurovascular structures in the neck. In recent years, technology has been developed to improve the accuracy and thereby the safety of cervical pedicle screw placement over traditional fluoroscopic techniques, including intraoperative 3D navigation, computer-assisted Systems and 3D template moulds. We have performed a systematic review into the accuracy rates of the various systems. Methods: The PubMed and Cochrane Library databases were searched for eligible papers; 9 valid papers involving 1427 screws were found. Results: fluoroscopic methods achieved an 80.6% accuracy and navigation methods produced 91.4% and 96.7% accuracy for templates. Conclusion: Navigation methods are significantly more accurate than fluoroscopy, they reduce radiation exposure to the surgical team, and improvements in technology are speeding up operating times. Significantly superior results for templates over fluoroscopy and navigation are complemented by reduced radiation exposure to patient and surgeon; however, the technology requires a more invasive approach, prolonged pre-operative planning and the development of an infrastructure to allow for their rapid production and delivery. We affirm the superiority of navigation over other methods for providing the most accurate and the safest cervical pedicle screw instrumentation, as it is more accurate than fluoroscopy and lacks the limitations of templates.

Introduction: Spinal instrumentation in idiopathic adolescent scoliosis (AIS) aims to correct spinal deformity, and maintain spinal stability. Proximal junctional kyphosis (PJK) is a relatively common postoperative complication. Posterior-only fusion using diverse instruments such as pedicle screw and hybrid hook plus screw is favored to correct spinal deformity. The current study aims to compare PJK incidence between pedicle screw versus hybrid hook plus screw. Methods: This non-randomized clinical trial has been conducted on 71 AIS patients undergone posterior-only spinal deformity fusion using pedicle screw only (n=42) or hook plus pedicle (n=29) implantation in 2015-20. The proximal thoracic (PT), main thoracic (MT), T5-T12 sagittal Cobb angles and proximal junctional angle (PJA) were evaluated through radiographies taken at baseline, immediately postoperative, within 6 and 18 months. PJK was defined as PJA >10 degrees. Results: Using both pedicle screw only and hook plus pedicle have led to significant improvement in MT, PT, PJA and T5-T12 angles (P-value0.05). Seventeen cases (23.9%) presented PJK among which 11 (26.2%) and 6 (20.7%) ones were in the predicle screw versus hook plus screw implantation groups, respectively (P-value=0.54). The comparison of PJA and T5-T12 Cobb angles revealed significant difference between the PJK versus non-PJK cases (P-value

STUDY DESIGN A prospective analysis. OBJECTIVE To test if threshold-based monitoring of compound muscle action potentials (CMAPs) by stimulating the screw loaded to uninsulated extender sleeve provides a valid safety warning for percutaneous pedicle screw (PPS) placements in the lumbosacral spine. SUMMARY OF BACKGROUND DATA Utility of the CMAP monitoring to PPS procedures remains controversial. METHODS A series of 202 patients underwent a total of 1664 lumbosacral PPS placements under CMAP monitoring without fluoroscopic guidance. The monitoring consisted of stimulating the PPS assembled to uninsulated extender sleeve and recording CMAPs from the vastus medialis, biceps femoris, tibialis anterior, and medial gastrocnemius. Automated steps of a threshold hunting algorithm using 0.2-ms duration pulses of increasing intensities delivered at 2/s allowed quick determination of a minimum stimulation current to evoke >100-μV amplitude CMAPs. RESULTS At L2 through S1 spines, postoperative CT scans identified 51 medial or inferior pedicle wall breaches of 1536 screws (3.3%) without neurologic complications. The ROC curve analysis determined the critical cut-off threshold value of 27 mA (74% sensitivity and 95% specificity) for predicting 35 breaches of 627 screws (5.6%) at L2 and L3, and of 17 mA (100% sensitivity, 98% specificity) for 16 of 909 (1.8%) at L4 through S1. While advancing the screw, 3 breaches (5.9%) showed a particularly low threshold of ≤6-mA, allowing the surgeon to immediately redirect the screw and retest the new trajectory as safe. CONCLUSION Screw stimulation with threshold hunting algorithm has a distinct advantage over the time-consuming insulated pilot hole stimulation, allowing an uninterrupted flow of the surgery. The present findings have documented practical usefulness and reliability of CMAP monitoring using direct stimulation of the PPS assembled to uninsulated extender sleeve.Level of Evidence: 2.

The Cirq is a surgeon-controlled robotic arm that provides a new technique for accurately placing transpedicular screws. This report aims to present a technical report and our experience with this new robotic arm combined with intraoperative navigation. Technique and workflow using the Cirq robotic arm with intraoperative navigation is described. A retrospective review was conducted of all patients undergoing elective open thoracic/lumbar fusion surgery by a single surgeon in the first year of using the novel Cirq robotic arm. Descriptive analysis of patient and operative variables was performed. A total of 84 patients underwent placement of a total 714 transpedicular screws using the Cirq robotic arm. Most (69.1%) underwent 3–6 level fusion procedures. Mean operative time was 198 min total and 28 min when adjusted per screw. There was a learning curve with operative time per screw decreasing from 32 to 25 min from the first to second half of cases (p = 0.057). There were no intraoperative screw revisions and 2.4% (2/84) required instrumentation revision and return to the operating room. The Cirq robotic arm is seamlessly incorporated into the workflow of a transpedicular fusion. Our experience with over 700 pedicle screw placements using the Cirq robot demonstrates efficacy and safety although further comparative studies are needed.

Objective Traditional iliac (TI) screws require extensive dissection, involve offset-connectors, and have prominent screw heads that may cause patient discomfort. S2 alar-iliac (S2AI) screws require less dissection, do not need offset connectors, and are less prominent. However, the biomechanical consequences of S2AI screws crossing the alar-iliac joint is unknown. The present study investigates the fixation strength of a modified iliac (MI) screw, which has a more medial entry point and reduced screw prominence, but does not cross the alar-iliac joint. Methods Eighteen sacropelvic spines were divided into 3 groups (n = 6): TI, S2AI, and MI. Each specimen was fixed unilaterally with S1 pedicle screws and pelvic fixation according to its group. Screws were loaded at ±10 Nm at 3Hz for 1000 cycles. Motion of each screw and rod strain above and below the S1 screw was measured. Results Toggle of the S1 screw was lowest for the TI group, followed by the MI and S2AI groups, but there were no significant differences (P = 0.421). Toggle of the iliac screw relative to the pelvis was also lowest for the TI group, followed by the MI group, and was greatest for the S2AI group, without significant differences (P = 0.179). Rod strain was similar across all groups. Conclusions No statistically significant differences were found between the TI, S2AI, and MI techniques with regard to screw toggle or rod strain. Advantages of the MI screw include its lower profile and a medialized starting point eliminating the need for offset-connectors.

Over the past decade, several review articles have evaluated the techniques and outcomes of robotics vs traditional methods in spine surgery. Recently, robot-assisted pedicle screw placement has emerged, representing an important milestone in the evolution of spine surgery. In the present article, the authors aim to provide the historical context regarding the use and growth of spinal robotics through the lens of the Industrial Revolution and the personal computer revolution. While the former provides insight into the current implications of robotics in spine surgery, the latter predicts future steps in this arena.

Introduction: Pedicle screw fixation systems are widely used for treatment of various spinal pathologies, including spinal stenosis, scoliosis, spinal deformities and fractures. Stress shielding is considered to be a major factor contributing to insufficient fixation strength, leading to screw loosening. In this study, the influence of pedicle screw thread width on the displacement of pedicle screw and stress transfer is analyzed using 2-Dimensional axisymmetric finite element (FE) model. Methods: FE model consisting of cancellous and cortical bone, along with pedicle screw is developed for this study. The pedicle screw thread width is varied between 0.1 mm and 0.6 mm in steps of 0.1 mm, while the other geometric parameters, including screw half-angle, pitch, diameter, and length are kept constant. Three different contact conditions between screw and bone, such as frictionless, frictional, and bonded are considered to simulate hours, days, and months after surgery, respectively. The material properties and boundary conditions are applied based on previous studies. An axial force of 80 N is applied on the screw head to simulate axial pull-out test. Results: Similar patterns of stress distribution are observed for all screw models, with high stress concentration above the first thread. The highest displacement in screw is observed shortly after surgery, while the highest displacement in cancellous and cortical bone is observed few days and months after the surgery, respectively. The average von Mises stress in screw decreases with increase in thread width for all contact conditions. In few hours/days after the surgery, stress transfer parameter increases with increase in thread width, up to a thread width of 0.5 mm and then decreases. The changes in stress transfer parameter are negligible few months after the surgery. Conclusion: This study highlights the influence of thread width on displacement and stress transferred to the bone, at different durations after the surgery. It is observed that a thread width of 0.5 mm exhibits the highest stress transfer, leading to reduced stress shielding and improved bone remodeling. It appears that this study might aid in developing better pedicle screws for the treatment of various spinal pathologies.

For surgical treatment of instable upper cervical injuries, the Harms technique using lateral mass screws provides rigid fixation and favourable clinical outcomes. The use of the posterior arch of C1 as a “pedicle” allows for screw anchorage, giving improved biomechanical stability. Therefore, the aim of this study was to introduce a bilateral safe zone for C1 pedicle screws, regarding screw angulation and pedicle height. We retrospectively reviewed the CT scans of 500 patients. Three-dimensional reformats were generated for detailed measurements. Centre screw entry point (EP), length of lateral mass as screw trajectory, lateral mass width (LMW), length of screw trajectory (ST), maximal divergence (DI) and maximal convergence (CON) from EP without perforation, and pedicle height (PH) of the posterior arch were measured. The 500 cases consisted of 335 males and 165 females, with a mean age of 49.5 years. Measurements did not demonstrate significant side-related differences. The mean screw entry point was 22.8 mm from the midline-axis (left 22.6 mm; right 23.0 mm). From this point, a safe zone between 11.6° of divergence and 19.6° of convergence was detected. Measurements of female patients were generally smaller, with significant differences from male patients (p

Objective To assess the biomechanical effect of lateral inclination C1 and C2 pedicle screws on the atlantoaxial fixation through vitro human cadaveric study. Methods From January 2016 to December 2017, fresh-frozen cadaveric cervical spines with intact ligaments from eight donated cadavers at an average age of 71.5 ± 10.6 years, comprising of six males and two females, were collected. There were no fracture and congenital malformation in all specimens according to the imaging examination. The range of motion (ROM) of the specimens were tested in their intact condition and destabilized condition. Next, the specimens were randomly divided into two groups to ensure no differences in sex and age: Group 1 was medial inclination C1 pedicle screw and C2 pedicle screws (C1 MPS-C2 PS) and Group 2 was lateral inclination C1 pedicle screw and C2 pedicle screws (C1 LPS-C2 PS). The ROM of the fixation scenarios were recorded. Thereafter, all the specimens with fixation constructs were tested for 1,000 cycles of axial rotation and tensile loading to failure was carried out collinearly to the longitudinal axis of all the screws, the data were documented as screw pullout strength (SPS) in newtons. All the recorded data subjected to quantitative analysis. Results The ROM of specimens was increased significantly in destabilized condition and significantly reduced in fixation condition compared with intact condition. In C1 LPS-C2 PS groups, the C1 -C2 cervical segment showed 3.96° ±1.21° and 3.75° ± 1.33° in flexion and extension direction, 2.85° ± 0.91° and 2.96° ± 0.71° in right and left lateral bending, 2.20° ± 0.43° and 2.15° ± 0.40° in right and left axial rotation. In C1 MPS-C2 PS groups, it showed 4.24° ±1.31° and 3.98° ± 1.21° in flexion and extension direction, 2.76° ± 1.10° and 3.23° ± 0.62° in right and left lateral bending, 2.20° ± 0.46° and 2.21° ± 0.42° in right and left axial rotation. There was no statistically significant difference on ROM and screw pullout strengths (764.29 ± 129.00 N vs 714.55 ± 164.63 N) between the two groups. However, there was one specimen in the C1 MPS-C2 PS group showing rupture the inferior wall of the left screw trajectory owing to the relatively thin posterior arch of the atlas, the screw pullout strength was significantly reduced (left pullout strength value: 430.5 N, right pullout strength value: 748.4 N). Therefore, in the case of the thin posterior arch of the atlas, the C1 LPS-C2 PS group had strong long-term biomechanics. Conclusion The lateral inclination C1 pedicle screw can achieve the same biomechanical strength as the traditional atlas pedicle screw. However, for the case where the posterior arch of the atlas is relatively thin, a lateral inclination C1 pedicle screw is more suitable.

Study design Retrospective observational study. Objective This study aimed to determine the effect of reducing the radiation dose of intraoperative cone beam computed tomography (CBCT) during posterior spinal fusion (PSF) for pediatric scoliosis on the rate of pedicle screw (PS) violation. Summary of background data Intraoperative CBCT for pediatric scoliosis improves the accuracy of PS insertion in PSF. However, few reports have addressed the PS perforation rate from reduced radiation doses in hybrid navigation. Methods We evaluated 855 PSs inserted into 58 pediatric scoliosis patients (11 male and 47 female, mean age: 16.6 years) who underwent PSF using CBCT. A radiation dose of 1/3 or 1/5 of the normal dose (ND) was defined as a low dose (LD). After PS insertion, intraoperative CBCT images were reviewed to assess the degree of PS perforation. G2-3 (i.e., perforations of 4 mm or more) was defined as a violation. The PS violation rate was compared between the groups, and factors associated with violations were examined. Results A total of 567 and 288 screws were inserted in the ND group and LD group, respectively. The PS violation rate was comparable at 1.8% in the ND group and 1.7% in the LD group. Multiple logistic regression analysis showed that distance from the upper instrumented vertebra (UIV) was an independently associated factor of PS violation (+1 vertebra, OR 0.73, P = 0.038). In addition, the mean height of patients with PS violations (148.8 ± 3.6 cm) was significantly shorter than that of patients without violations (157.9 ± 1.2 cm) (P = 0.034). Conclusion There was no increase in PS violation rate with lower doses of radiation for intraoperative navigation CBCT. Extra care is warranted for vertebrae close to the UIV and patients of shorter stature.Level of Evidence: 3.

BACKGROUND: Pedicle screw fixation in spinal constructs can be subject to failure requiring revision surgery. In cases of aseptic loosening various salvage techniques have been described. Revision screws augmented with cement have become popular but are not without risks. Larger diameter screws are often used but result in reducing bone stock or expanding the pedicles. We present a novel technique of pedicle screw revision by impaction bone allografting and a case series. METHODS: The failed screws are removed. The screw track is probed to check its integrity. Milled bone allograft is funneled into the screw hole and sequentially impacted, before insertion of a replacement screw. We report a case series and describe a single case where this method has been used. Information was gathered from the electronic patient record in our hospital. RESULTS: Ten screws were revised in 7 patients. Mean age at first surgery was 60.86 (48–76) years. Average time between first surgery and revision was 12.6 (4.7–49.9) months. Average follow-up was 26.2 (5.7–62.2) months and no screws showed any signs of loosening. CONCLUSIONS: Impaction grafting with bone allograft is a technique for pedicle screw salvage that can be used safely and effectively as an alternative to cemented screws, when pedicle screws have failed by aseptic loosening. It avoids the risks associated with cemented screws and in our series was successful.

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.

Pedicles on the concave side of the proximal thoracic (PT) curve in adolescent idiopathic scoliosis (AIS) patients with Lenke II and IV deformities tend to be narrow and dysplastic, making pedicle screw (PS) insertion challenging. The aim of this study was to evaluate the feasibility for PS placement in these patients using pedicle chord length, diameter, and channel morphology. In this retrospective study, 56 consecutive AIS patients with Lenke II or IV curves who underwent instrumented posterior spinal fusion (PSF) were studied. The mean age at surgery was 14.8 years and the mean PT curve measured 45°. Two independent investigators evaluated all visible pedicles from T1 to T6 vertebral levels using axial images from intraoperative computed tomography-guided navigation recording the pedicle: (1) maximum transverse diameter ‘d’ at the isthmus, (2) maximum chord length ‘l’, and (3) qualitative assessment of the channel morphology (types A–D). Two hundred and sixty-eight concave and 264 convex pedicles were measured. The mean ‘d’ of the concave pedicles at T3 and T4 was 5.0 mm for the convex counterparts (p

Spondylolysis has never been found in a newborn. Repetitive cyclic loading ultimately results in a stress fracture. Impingement between the inferior articular process of the cephalad verbetra and the superior articular process of the caudal vertebra creates pending moment that must be resisted by the pars. The hard cortical bone of the pars predisposes it to fatigue fracture, as well as nonunion, decreasing the likelihood of spontaneous healing. If healing occurs, the pars often heal in an elongated position. Either non-union or healing with elongation permits vertebral subluxation. This fundamental change in bony anatomy exposes the disc to increased shear load, even though the axial load remains unchanged. When the stiffness of the cortical bone is reduced by an underlying condition (congenital dysplasia), smaller amounts of tensile forces are required to produce a fatigue fracture. Another possible mechanism is an extension torque which is developed by the erector spinae acting through its attachment to the spinous process, resulting in a stress concentration at the pars. The aim of the study is to analyze the post-operative outcomes in, in-situ posterior spinal fusion with pedicle screws and rods in Grade I and Grade II isthmic and degenerative spondylolisthesis.

This case study presents a 47-year-old male who was diagnosed with Gorham-Stout syndrome (GSS) 10 years ago in the occipitocervical junction. The pathology caused the resorption of the suboccipital bone, clivus, foramen magnum, and C1-C3 laminae. After his first fusion attempt in 2010 using occipital plate-cervical lateral mass screws, he needed many revision surgeries either for the progression of the pathology or for instrumentation failure and wound healing problems. Eventually, a new occipital plate and cervical pedicle screws were applied to obtain the exact solution. The involvement of the craniovertebral junction in GSS may be challenging for spinal surgeons due to the inadequate bone reserve for stabilization. As lateral mass screws cannot provide a strong pull-out force, cervical pedicular screws may be used as the first choice for unstable cervical GSS cases.

Study Design: Systematic review. Objectives: To summarize the results of clinical studies investigating spinal instrumentation techniques aiming to reduce the postoperative incidence of proximal junctional kyphosis (PJK) and/or failure (PJF) in adult spinal deformity (ASD) patients. Methods: EMBASE and Medline® were searched for articles dating from January 2000 onward. Data was extracted by 2 independent authors and methodological quality was assessed using ROBINS-I. Results: 18 retrospective- and prospective cohort studies with a severe or critical risk of bias were included. Different techniques were applied at the upper instrumented vertebra (UIV): tethers in various configurations, 2-level prophylactic vertebroplasty (2-PVP), transverse process hooks (TPH), flexible rods (FR), sublaminar tapes (ST) and multilevel stabilization screws (MLSS). Compared to a pedicle screw (PS) group, significant differences in PJK incidence were found using tethers in various configurations (18% versus 45%, P = 0.001, 15% versus 38%, P = 0.045), 2-PVP (24% vs 36%, P = 0.020), TPH (0% vs. 30%, P = 0.023) and FR (15% versus 38%, P = 0.045). Differences in revision rates for PJK were found in studies concerning tethers (4% versus 18%, P = 0.002), 2-PVP (0% vs 13%, P = 0.031) and TPH (0% vs 7%, P = n.a.). Conclusion: Although the studies are of low quality, the most frequently studied techniques, namely 2-PVP as anterior reinforcement and (tensioned) tethers or TPH as posterior semi-rigid fixation, show promising results. To provide a reliable comparison, more controlled studies need to be performed, including the use of clinical outcome measures and a uniform definition of PJF.

As physician burnout and wellness become increasingly recognized as vital themes for the medical community to address, the topic of chronic work-related conditions in surgeons must be further evaluated. While improving ergonomics and occupational health have been long emphasized in the executive and business worlds, particularly in relation to company morale and productivity, information within the surgical community remains relatively scarce. Chronic peripheral nerve compression syndromes, hand osteoarthritis, cervicalgia and back pain, as well as other repetitive musculoskeletal ailments affect many spinal surgeons. The use of ergonomic training programs, an operating microscope or exoscope, powered instruments for pedicle screw placement, pneumatic Kerrison punches and ultrasonic osteotomes, as well as utilizing multiple surgeons or microbreaks for larger cases comprise several methods by which spinal surgeons can potentially improve workspace health. As such, it is worthwhile exploring these areas to potentially improve operating room ergonomics and overall surgeon longevity.

PURPOSE Although pediatric spinal deformity correction using pedicle screws has a very low rate of complications, the long-term consequences of screw malposition is unknown. CT navigation has been proposed to improve screw accuracy. The aim of this study was to determine whether intraoperative navigation during pedicle screw placement in pediatric scoliosis makes screw placement more accurate. We also examined radiation exposure, operative time blood loss and complications with and without the use of CT navigation in pediatric spinal deformity surgery. METHODS A systematic review of the literature was conducted. After screening, 13 articles were qualitatively and quantitatively analyzed to be used for the review. A random effects meta-analysis using REML methodology was employed to compare outcomes of screw accuracy, estimated blood loss, radiation exposure, and surgical duration. RESULTS Screws placed with CT navigation surgery were three times as likely to be deemed "acceptable" compared with screws placed with freehand and 2D fluoroscopy assistance, twice as likely to be "perfect", and only 1/3 as likely to be potentially unsafe (all p value

OBJECTIVE To explore the corridor for atlas pedicle screw placement perpendicular to the coronal plane and to develop patient-specific navigation templates for pedicle screw placement. METHODS This study is a retrospective analysis. A total of 71 patients (41 males and 30 females) were involved in this study from June 2016 to June 2018, and they were divided into a template group (39 patients) and a conventional group (32 patients). The CT-based 3D reconstruction models were analyzed in the template group. From the perspective of the 3D atlas in a coronal view, the pedicle corridor was obtained. Taking the center of the tangential circle of the pedicle as the entry point, we simulated screw placement perpendicular to the coronal plane. Then, the individual navigation template was designed and used in surgery. In the conventional group, free-hand pedicle screw placement was performed perpendicular to the coronal plane. The diameter of the maximum tangential circle and screw length of the pedicle corridor were measured in the template group. The surgical time, radiation exposure time, screw grading criteria and so on were evaluated and compared between the two groups after surgery. RESULTS ;The diameter of the maximum tangential circle and the distance between the entry point and posterior tubercle were significantly greater in males than in females. The operation was successfully completed in all patients, without aggravation of nerve injury, and the follow-up was 12-20 months, with an average of 15.6 months. A total of 78 screws were inserted in the template group, and 64 screws were inserted in the conventional group. The surgical times in the template group and conventional group were 76.47±24.44 min and 125.63±36.41 min, respectively. The radiation exposure times in the template group and conventional group were 3.51±1.77 and 10.15±4.95, respectively, and there was a significant difference between the two groups. In the template group, the deviation in the screw entry point and screw angle were 1.92±1.67 mm and 2.08±1.98°, respectively. The medial angle deviation between the left and right sides was 2.71±1.88° in the template group, which was significantly less than the deviation of 3.76±2.22° in the conventional group. CONCLUSION A pedicle screw trajectory perpendicular to the coronal plane can be quickly obtained based on the perspective of 3D models. The technique of screw placement perpendicular to the coronal plane assisted by navigation templates has a shorter operative time, lessintraoperative fluoroscopy and a higher safety of screw placement than traditional surgery.

BACKGROUND CONTEXT A few meta-analyses have compared conventional pedicle screws (PS) with cortical bone trajectory-pedicle screws (cortical screw [CS]) in posterior lumbar fusion surgery. However, these studies did not control for diagnosis, which has been shown to impact surgical outcomes. PURPOSE To compare PS with CS as a posterior fixation technique in posterior lumbar interbody fusion (PLIF) for degenerative spondylolisthesis (DS). STUDY DESIGN Systematic review and meta-analysis. METHODS We searched the Cochrane, Embase, and Medline databases for articles that compared postoperative outcomes between PS and CS for posterior stabilization in PLIF for DS with November 11, 2020, as the publication cutoff. The differences in primary and secondary outcome measures were calculated and analyzed for significance (p RESULTS A total of 916 publications were assessed; 5 studies met all the study criteria. The fusion rates between PS and CS groups were not significantly different (p=.41). Blood loss and operative time were significantly less in the CS group than the PS group (p=.04 and 0.02, respectively), but the length of stay was not significantly different (p=.08). The total complication rate was significantly less in CS group than that in PS group (p=.002). The rates of adjacent segment pathology (ASP) and operation for ASP in the CS group were significantly less than the PS group (p=.03 and .04, respectively). CONCLUSIONS Though CS and PS appear to have similar 1-year fusion rates and length of stay, there appears to lower blood loss and operative time with CS. Though encouraging, these findings were based on low-quality evidence from a small number of retrospective studies that are prone to bias.

To report our experience using the scan-and-plan workflow and review current literature on surgical efficiency, safety, and accuracy of next-generation robot-assisted (RA) spine surgery.The records of patients who underwent RA pedicle screw fixation were reviewed. The accuracy of pedicle screw placement was determined based on the Ravi classification system. To evaluate workflow efficiency, 3 demographically matched cohorts were created to analyze differences in time per screw placement (defined as operating room [OR] time divided by number of screws placed). Group A had4 screws placed, Group B had 4 screws placed, and Group C had4 screws placed. Intraoperative errors and postoperative complications were collected to elucidate safety.Eighty-four RA cases (306 pedicle screws) were included for analysis. The mean number of screws placed was 2.1 ± 0.3 in Group A and 6.4 ± 1.2 in Group C; 4 screws were placed in Group B patients. The accuracy rate (Ravi grade I) was 98.4%. Screw placement time was significantly longer in Group A (101 ± 37.7 minutes) than Group B (50.5 ± 25.4 minutes) or C (43.6 ± 14.7 minutes). There were no intraoperative complications, robot failures, or in-hospital complications requiring a return to the OR.The scan-and-plan workflow allowed for a high degree of accuracy. It was a safe method that provided a smooth and efficient OR workflow without registration errors or robotic failures. After the placement of 4 pedicle screws, the per-screw time remained constant. Further studies regarding efficiency and utility in multilevel procedures are necessary.

Background The penetrating end plate screw (PES) technique improved the fixation strength of the pedicle screw by penetrating the end plate in posterior fusion. The "double" PES, which is a trajectory that penetrates both the upper end plate of the corresponding vertebra and the lower end plate of the upper adjacent vertebral body, provides a stronger tricortical fixation but requires a stricter trajectory. The purpose of this study was to measure the cephalad angles from T7-L5 that would allow a safe trajectory for “double” PES. Methods We analyzed 1078 pedicles of 539 vertebral bodies of 50 consecutive cases (27 males and 23 females, mean age, 63.3 years) who underwent computed tomography (CT) myelography for evaluation of spinal disorders. The mean cephalad angle to obtain the double PES trajectory of each vertebra was examined, except for cases in which the appropriate trajectory would perforate the pedicles. Results The cephalad angle for the appropriate trajectory of “double” PES ranged from 23.4 to 37.6 degrees in the thoracic spine and 34.8 to 40.8 degrees in the lumbar spine. The ratio of pedicle perforation was significantly higher at T7 (16%), L4 (26%), and L5 (52%). Conclusions It is important to measure the optimal cephalad angle by preoperative computed tomography imaging according to the vertebral level. In L4 and L5, “double” PES should be avoided because it is often unsafe.

Background The choice of implants in neuromuscular scoliosis (NMS) surgery remains controversial. Sublaminar polyester bands (SPBs) seem to be a promising alternative implant. The purpose of current study was to compare clinical and radiologic results of posterior instrumentation and fusion using hybrid constructs versus only pedicle screws for NMS treatment. Methods In 24 patients, pedicle screws were used in all segments, and 18 patients underwent hybrid fixation. Cobb angle, thoracic kyphosis, lumbar lordosis angles, and pelvic obliquity were compared before and immediately after surgery, at the last follow-up radiographs. Demographic, clinical information, duration of surgery, estimated blood loss (EBL), blood transfusion, and complications were compared between groups. Additionally, patients were assessed for pain with visual analog scale (VAS) and quality of life with Short Form 36 (SF-36) and the Oswestry scale. Results Baseline characteristics of patients were similar except for EBL (P = 0.002) and follow-up duration (P = 0.004). The mean curve correction was 58.1% in the hybrid group, and 67.6% in the screw group (P = 0.07), and loss of correction was significantly lower in hybrid group (2.72° ± 1.48° vs. 3.66° ± 1.52°, P = 0.049). Functional scores at final follow-up were equal in both groups (VAS P = 0.865, Oswestry P = 0.097, SF-36 Physical P = 0.358, SF-36 Mental P = 0.145). Conclusions SPBs might be a better fixation alternative at the apex of rigid spinal deformity in NMS. The deformity can be corrected with less blood loss and at a similar rate of correction, with similar rate complications compared with pedicle screws.

Objective Previous studies have shown that pedicle screw stimulation thresholds ≤6−8 mA yield a high diagnostic accuracy of detecting misplaced screws. Our objective was to determine the optimal “low” stimulation threshold to predict new postoperative neurologic deficits and identify additional risk factors associated with deficits. Methods We included patients with complete pedicle screw stimulation testing who underwent posterior lumbar spinal fusion surgeries from 2010−2012. We calculated the diagnostic accuracy of pedicle screw responses of ≤4 mA, ≤6 mA, ≤8 mA, ≤10 mA, ≤12 mA, and ≤20 mA to predict new postoperative lower-extremity (LE) neurologic deficits. We used multivariate modeling to determine the best logistic regression model to predict LE deficits and identify additional risk factors. Statistics software packages used were Python3.8.5, NumPy 1.19.1, Pandas 1.1.1, and SPSS26. Results We studied 1179 patients who underwent 8584 pedicle screw stimulations with somatosensory evoked potential and free-run electromyographic monitoring for posterior lumbar spinal fusion. Twenty-five (2.1%) patients had new LE neurologic deficits. A stimulation threshold of ≤8 mA had a sensitivity/specificity of 32%/90% and a diagnostic odds ratio/area under the curve of 4.34 [95% confidence interval: 1.83, 10.27]/0.61 [0.49, 0.74] in predicting postoperative deficit. Multivariate analysis showed that patients who had pedicle screws with stimulation thresholds ≤8 mA are 3.15 [1.26, 7.83]× more likely to have postoperative LE deficits while patients who have undergone a revision lumbar spinal fusion surgery are 3.64 [1.38, 9.61]× more likely. Conclusions Our results show that low thresholds are indicative of not only screw proximity to the nerve but also an increased likelihood of postoperative neurologic deficit. Thresholds ≤8 mA prove to be the optimal “low” threshold to help guide a correctly positioned pedicle screw placement and detect postoperative deficits.

Study Design: Retrospective cohort study. Objective: To (1) define utilization trends for navigated instrumented posterior lumbar fusion (PLF), (2) compare reasons and rates of revision at 30-day, 60-day, 90-day, and 1-year follow-up, and (3) compare 90-day perioperative complications between navigated versus conventional instrumented PLF. Methods: Patients who underwent navigated or conventional instrumented PLF were identified from the Humana insurance database using the PearlDiver Patient Records between 2007-2017. Usage of navigation was characterized. Patient demographics and operative characteristics (number of levels fused, interbody usage) were compared between the 2 treatment groups. Propensity score matching was done and comparisons were made for revision rates at different follow-up periods (categorized by reasons) and other 90-day perioperative complications. Results: This study included 1,648 navigated and 23 429 conventional instrumented PLF. Navigated cases increased over the years studied to approximately 10% in 2017. Statistical analysis after propensity score matching revealed significantly lower rates of hardware-related revision at 90-day follow-up in the navigated cohort (0.49% versus 1.15%, P = .033). At 1-year follow-up, the navigated cohort continued to have significantly lower rates of hardware-related revision (1.70% versus 2.73%, P = .044) as well as all cause revision (2.67% versus 4.00%, P = .032). There were no statistical differences between the 2 cohorts in any of the 90-day perioperative complications studied, such as cellulitis and blood transfusion ( P > .05 for all). Conclusions: These findings suggest that navigation is associated with reductions in hardware-related revisions after instrumented PLF. However, these results should be interpreted cautiously in the setting of potential confounding by other unmeasured variables.

Introduction For safe pedicle screws placement, knowledge of pedicle morphometry is essential, because an inconsistency between pedicle width and the screw diameter may lead to severe complications like nerve, vessel or visceral injuries. Objectives To study the spinal pedicle width and height of lumbar spine, using multidetector CT (MDCT), among the Indian population. To study the spinal pedicle angulation of lumbar spine, using MDCT, among the Indian population. Method The study was conducted at a tertiary care multispecialty hospital. In the present study, a total of 321 patients were included, who underwent MDCT scan without contrast at our institution, over a period of 2 years, from May 2017 to May 2019. The study population (n = 321) was divided into different subgroups on the basis of the age. The data was taken from the workstation. Comparison was made separately between each subgroup. Results In our subset of population, the 10 to 90 years age group, pedicle dimensions are as follow: The pedicle diameter from L1 to L5 is 4.46 to 11.92 mm. The pedicle height from L1 to L5 is 7.38 to 11.01 mm. The pedicle axial angulation from L1 to L5 is 22.27 to 36.08 degree. The pedicle lateral angulation from L1 to L5 is 16.12 to 22.47 degree. Conclusion Knowledge of the pedicle morphometry (pedicle width, height and angulation) of lumbar spine will help the neurosurgeons standardize the size of pedicle screws which is required for spinal fixation surgery at various lumbar vertebra levels.

Objective: To study the thoracic spine anatomy for accurate placement of pedicle screws using computerized tomography. Material and Methods: CT scans of 200 patients were included in our study. T1 to T12 vertebrae morphology was studied for each patient. Following measurements were taken, 1: Transverse pedicle width, 2 = Depth of anterior cortex along pedicle axis, 3 = Transverse pedicle angle, 4 = canal dimensions, 5 = vertebral body height anterior and posterior, 6 = mid vertebral body width. Results: Transverse pedicle width decreased from T1 (4.06 ± 0.50 mm) to T4 (3.72 ± 0.17 mm) and then gradually increases to T12 (6.08 ± 0.60 mm). Depth of the anterior vertebral cortex remained constant from T1 to T4 and gradually increases up to T12. Transverse pedicle angle remained constant from T1 to T4 with a maximum at T4 (23.39 ± 3.15 mm) and then gradually decreased to T12 (3.99 ± 2.16 mm). Anteroposterior (AP) canal dimensions were minimum at T7 (17.03 ± 1.01 mm) and maximum at T2 (21.2 ± 1.07 mm). Interpedicular (IPD) canal dimensions were minimum at T6 (19.18 ± 1.6 mm) and maximum at T3 (23.18 ± 1.2 mm). Anterior vertebral body height was minimum at T1 (16.9 ± 1.34 mm) and maximum at T12 (27.14 ± 1.34mm). Posterior vertebral body height was minimum at T1 (18.8 ± 1.13 mm) and maximum at T12 (29.76 ± 1.43 mm). Conclusion: A detailed anatomy of the thoracic spine is essential for surgical planning to decrease postoperative complications.

Objectives This study aims to explore a novel intraoperative trajectory-determined strategy of grouped patient-specific drill templates (PDTs) for transoral C2 pedicle screw insertion (C2 TOPI) for atlantoaxial dislocation (AAD) with incomplete reduction and to evaluate its efficiency and accuracy. Methods Ten cadaveric C2 specimens were scanned by computed tomography (CT) and randomly divided into two groups (the PDT and freehand groups). A novel intraoperative trajectory-determined strategy of grouped PDTs was created for AAD with incomplete reduction. C2 TOPI was performed by use of the PDT technique and the fluoroscopy-guided freehand technique. After surgery, the screw deviations from the centroid of the cross-section at the midpoint of the pedicle and screw position grades were assessed in both groups. Results Compared to the freehand group, the PDT group had a significantly shorter surgery time than the freehand group (47.7 vs 61.9 min, P 0.05). Conclusion The novel intraoperative trajectory-determined strategy of grouped PDTs can be used as an accurate and feasible method for C2 TOPI for AAD with incomplete reduction.

BACKGROUND/INTRODUCTION Pedicle screws have long been part of the continued advancements in spine surgery. Despite the many techniques that have been devised for their safe placement, malposition of screws continues to occur. Studies have evaluated the possible safe limits of screw malposition, and have given some insight on anatomic variation in spinal deformity. Review of the literature reveals several cases of deleterious long-term sequelae of malpositioned screws. DISCUSSION With the current experience, proposed recommendations are provided to detect and avoid the potential long-term sequelae. Though the literature has helped to define possible concerning screws, there are no good studies predicting long-term risk. CONCLUSION Improvements in technology and techniques, advancements in intraoperative confirmation and postoperative surveillance, studies that assist risk stratification, and expert consensus evaluations will help guide surgeons in their decision for addressing misplaced screws.

Study design Retrospective cohort study. Objective This study was performed to evaluate the accuracy of cervical pedicle screw (CPS) placement with use of a navigated surgical drill (ND) and to compare it with navigated manual probe (MP) at C3–C6. Methods 47 consecutive patients (27 males and 20 females, 67.2 [33–91] years) underwent a posterior cervical fixation using CPSs under an intraoperative 3D - – CT based navigation system (total 207 CPSs). For initial probing, ND with 2.2-mm steel burr was used since Apr. 2017 (Group ND; 33 patients, 152 CPSs). MP was used earlier (Group MP; 14 patients, 55 CPSs). There were no other different procedures between the two groups. The accuracy of CPS placement was graded with postoperative CT and compared between the two groups. Results There were no significant differences in the total perforation rates both in axial and sagittal planes between Groups ND and MP (axial; 7.2% vs. 14.5%, p = 0.25, sagittal; 10.5% vs. 14.5%, p = 0.46). However, the lateral and rostral perforation rates were significantly reduced in Group ND compared to Group MP (lateral: 36.4% vs. 87.5%, p = 0.04; rostral: 6.3% vs. 100%, p = 0.001). Conclusion Although ND did not decrease the total perforation rate significantly, it reduced the incidence of lateral and rostral perforation. ND is likely to make initial probing easier without a forcible manipulation which might cause vertebral rotation.