Thoracic Screws Research Articles

Assessing the Accuracy and Safety Thresholds of Patient-Specific Screw Guide Template System in Cervical and Thoracic Spine Surgeries Using DAST Measurements.

To analyze the reliability of the newly developed patient-specific Screw Guide Template (SGT) system as an intraoperative navigation device for spinal screw insertion. We attempted to place 428 screws for 51 patients. The accuracy of the screw track was assessed by deviation of the screw axis from the preplanned trajectory on postoperative CT. The safety of the screw insertion was evaluated by the bone breach of the screw. The bone diameter available for screw trajectory (DAST) was measured, and the relations to the bone breach were analyzed. In the inserted screws, 98.4% were defined as accurate, and 94.6% were contained in the target bone. In the cervical spine, the screw deviation between breaching (0.57 mm) and contained screws (0.43 mm) did not significantly differ, whereas DAST for breaching screws (3.62 mm) was significantly smaller than contained screws (5.33 mm) (p<0.001). Cervical screws with ≥4.0 mm DAST showed a significantly lower incidence of bone breach (0.4%) than ≤3.9 mm DAST (28.3%) (p<0.001). In the thoracic spine, screw deviation and DAST had significant differences between breaching (1.54 mm, 4.41 mm) and contained (0.75 mm, 6.07 mm) (p<0.001). The incidence of the breach was significantly lower in thoracic screws with ≥5.0 mm (1.9%) than ≤4.9 (21.9%) DAST (p<0.001). This study demonstrated that our SGT system could support precise screw insertion for 98.4% accuracy and 94.6% safety. DAST was recommended to be ≥4.0 and ≥5.0 mm in the cervical and thoracic spines for safe screw insertion.

Decreasing the Pedicle Screw Misplacement Rate in the Thoracic Spine With Robot-guided Navigation.

A retrospective chart review. The aim of this study was to evaluate the screw accuracy of thoracic pedicle screws placed with a robot-guided navigation system. Thoracic pedicles are smaller in diameter than lumbar pedicles, making pedicle screw placement difficult. Misplaced pedicle screws may present complications including decreased construct stability, and increased risks of neurological deficits and blood vessel perforation. There is a dearth of knowledge on thoracic pedicle screw accuracy placed with a robot. A retrospective analysis of the robot-assisted placement of thoracic pedicle screws was performed. Preoperative and postoperative computed tomography (CT) scans of the implanted thoracic screws were collected to assess screw placement accuracy, pedicle breadth, and placement deviations. A CT-based Gertzbein and Robbins System was used to classify pedicle screw accuracy in 2mm increments. A custom image overlay software was used to determine the deviations between the preoperatively planned trajectory of pedicle screws and final placement at screw entry (tail), and tip in addition to the angular deviation. Seventy-five thoracic pedicle screws were implanted by navigated robotic guidance in 17 patients, only 1.3% (1/75) were repositioned intraoperatively. Average patient age and body mass index were 57.5 years and 25.9kg/m 2 , respectively, with 52.9% female patients. Surgery diagnoses were degenerative disk disease (47.1%) and adjacent segment disease (17.6%). There were zero complications, with no returns to the operating room. According to the CT-based Gertzbein and Robbins pedicle screw breach classification system, 93.3% (70/75) screws were grade A or B, 6.6% (5/75) were grade C, and 0% were grade D or E. The average deviation from the preoperative plan to actual final placement was 1.8±1.3mm for the screw tip, 1.6±0.9mm for the tail, and 2.1±1.5 degrees of angulation. The current investigation found a 93.3% accuracy of pedicle screw placement in the thoracic spine. Navigated robot assistance is a useful system for placing screws in the smaller pedicles of the thoracic spine. Level III-retrospective nonexperimental study.

Evaluation of the safety, radiographic and resident training results of thoracic pedicle screws placement using resection of the transverse process

Objective This study aimed at the evaluation and assessment of a simple method, the transverse process resection (TPR) technique, for freehand thoracic pedicle screw placement and the learning curve for trainee surgeons. Methods In the TPR technique, the tip of the thoracic transverse process (TP) is removed to create an entry point in the cancellous bone of the TP, and the thoracic pedicle is cannulated from the TP. We retrospectively evaluated the safety and radiographic results of the TPR technique and compared with that of conventional pedicle screws. The training performance of seven neurosurgical residents with TPR techniques were evaluated. Results Among 46 patients, a total of 322 thoracic screws were analyzed, including 178 screws placed using the TPR technique and 144 screws using the conventional straight-forward (SF) technique. TPR screws had greater medial angulations in all levels from T2 to T12 compared to SF screws (p < 0.001). The incidence of pedicle breach was lower in the TPR screws compared to SF screws (6.2% vs. 21.5%, p < 0.001), especially for screws placed by residents (6.7% vs. 29.6%, p < 0.001). Residents had improved performance following a cadaveric training course on the TPR technique (p = 0.001). Conclusion This study demonstrated the safety of the TPR technique for thoracic pedicle screw placement and its short learning curve for trainee surgeons.

Airo® navigation versus freehand fluoroscopy technique: A comparative study of accuracy and radiological exposure for thoracolumbar screws placement

PurposeThe aim was to compare the accuracy of freehand fluoroscopy and CT based navigation on thoracolumbar screws placement and their respective effects on radiological exposure to the patient. No previous study directly compared the Airo® navigation system to freehand technique. MethodsIn this monocentric retrospective study, 156 consecutive patients who underwent thoracolumbar spine surgery were included. Epidemiological data and surgical indications were noted. Heary classification was used for thoracic screws and Gertzbein-Robbins classification for lumbar screws. Radiological exposure was collected for each surgery. ResultsA total of 918 screws were implanted. We analyzed 725 lumbar screws (Airo® 287; freehand fluoroscopy 438) and 193 thoracic screws (Airo® 49; freehand fluoroscopy 144). Overall, lumbar screws accuracy (Gertzbein-Robbins grade A and B) was good in both groups (freehand fluoroscopy 91.3%; Airo® 97.6%; P<0.05). We found significantly less Grade B and C in the Airo® group. Thoracic accuracy was also good in both groups (Heary 1 and 2; freehand fluoroscopy 77.8%; Airo® 93.9%), without reaching statistical significance. Radiological exposure was significantly higher in the Airo® group with a mean effective dose of 9.69 mSv versus 0.71mSv for freehand fluoroscopy. ConclusionOur study confirmed that the use of Airo® navigation yielded good accuracy. It however exposed the patient to higher radiological exposure compared with freehand fluoroscopy technique. Level of evidenceLevel 3.

High Rate of Pulmonary Cement Embolism after Cement-Augmented Pedicle Screw Fixation: A 12-Year Single-Center Study.

The global trend toward increased life expectancy because of remarkable improvements in health care quality has drawn increased attention to osteoporotic fractures and degenerative spine diseases. Cement-augmented pedicle screw fixation has been established as the mainstay treatment for patients with poor bone quality. This study aimed to determine the number of patients with cement leakage and pulmonary cement embolism (PCE) as detected on thoracic computed tomography (CT), and to assess the potential risk factors for PCE. Patients undergoing cement-augmented pedicle screw placement in our institution between May 2008 and December 2020 were included. Data regarding baseline characteristics, complications, and cement leakage rates were collected. Indications for the performance of a postoperative thoracic CT due to the suspicion of PCE were intra- or postoperative complications, or postoperative oxygen supplementation. Moreover, PCE was accidently diagnosed because the thoracic CT was performed for medical reasons other than the suspicion of PCE (tumor staging, severe pneumonia, or exacerbated chronic pulmonary obstructive disease). A total of 104 patients with a mean age of 72.8 years (standard deviation of 6.7) were included. Of 802 screws, 573 were cement augmented. Of the 104 patients, 44 (42.3%) underwent thoracic CT scans to diagnose PCE; additionally, 67 (64.4%) demonstrated cement leakage, of whom 27 developed PCE and 4 were symptomatic. Cement-augmented thoracic screws were a risk factor for PCE (odds ratio: 1.5; 95% confidence interval: 1.2-2.1; p = 0.004). This study showed a high prevalence of cement leakage after cement-augmented pedicle screw insertion, with a relatively frequent incidence of PCE, as tracked by thoracic CT scans. Cement-augmented thoracic screw placement was a unique risk factor for PCE.

Pedicle Screw Placement Aided byC-Arm Fluoroscopy: A "Nevermore without" Technology to Pursue Optimal Spine Fixation.

The surgical technique and the intraoperative technology that support spinal pedicle screw placement have consistently evolved over the past decades to decrease the misplacement rate of pedicle screws. We retrospectively evaluated our case series by analyzing the period 2016-2020. Patients undergoing pedicle screw fixation for cervical, thoracic, or lumbar spine degenerative diseases have been included. Surgery was carried out with the aid of intraoperative 3D C-arm fluoroscopy to assess and optimize screw placement and/or correct possible mispositioning. Each patient underwent a postoperative CT scan. Our aim was to evaluate the safety and accuracy of pedicle screw placement and estimate the variation in mispositioning rates. We carried out 329 surgical procedures, as follows: 70 cervical, 78 thoracic spine, and 181 lumbar spine surgeries. An excellent overall pedicle screw positioning was obtained, with slight differences between the cervical (98.6%), thoracic (100%), and lumbar (98.9%) tracts. Accordingly, only three patients required a revision surgery owing to mispositioning (0.91%). In particular, intraoperative C-arm fluoroscopy significatively improved the accuracy of thoracic screw positioning, as shown by postoperative CT scans. Our experience proves the crucial role of intraoperative C-arm fluoroscopy in pursuing optimal technical results and improving patient outcomes at follow-up.

Spinal navigation with preoperative computed tomography

Safe placement of posterior cervical-sacral pedicle screws, S2-Ala-iliac screws, iliac screws, transarticular screws C1/2, translaminar screws C2 or cervical lateral mass screws under the guidance of spinal navigation. All posterior spinal instrumentations with screws: instabilities and deformities of rheumatic, traumatic, neoplastic, infectious, iatrogenic or congenital origin; multilevel cervical spinal stenosis with degenerative instability or kyphosis of the affected spinal segment. There are no absolute contraindications for spinal navigation. Cervical spine: Prone position on agel mattress, rigid head fixation, e.g., with Mayfield tongs; if appropriate, closed reduction under lateral image intensification; thoracic + lumbar spine: prone position on acushioned frame; midline posterior surgical approach at the level of the segments to be instrumented; if necessary, open reduction; insertion of the cervical/upper thoracic screws under the guidance of spinal navigation; if necessary, posterior decompression; instrumentation longitudinal rods; if fusion is to be obtained, decortication of the posterior bone elements with ahigh-speed burr and onlay of cancellous bone or bone substitutes. In stable instrumentations, no postoperative immobilization with orthosis is necessary, removal of drains (if used) 2-3days postoperatively (postop), removal of the sutures 14days postop, clinical and x‑ray controls 3and 12months postop or in case of clinical or neurological deterioration. Numerous studies showed that the use of spinal navigation significantly reduces implant malplacement rates, complications, and revision surgery. Furthermore, intraoperative radiation exposure to the operation team can be reduced by up to 90%.

The effect of the caudal insertion angle of pedicle screws on postoperative thoracic kyphosis in adolescent idiopathic scoliosis: a pilot study.

The study was a prospective analysis of collected data to compare the effect of the insertion angle (parallel or oblique relative to the upper-end plates) of thoracic pedicle screws on postoperative thoracic kyphosis in patients with idiopathic thoracic scoliosis. This study was conducted on idiopathic adolescent scoliosis (AIS) patients. Two groups of patients were defined according to the insertion angle of thoracic pedicle screws in relation to the upper-end plate of the corresponding vertebra, the insertion angles being either oblique or parallel. Seven consecutive AIS patients were compared in each group. Pre- and postoperative standing X-rays were obtained. Cobb's angles, sagittal parameters such as thoracic kyphosis (TK) (T1-T12) and lumbar lordosis (LL) (L1-S1) were all measured. The average of the main curve or compensatory curve corrections showed no significant differences between the two groups. From a sagittal profile perspective, the mean TK in the oblique screw group was 39.3 ± 11.5 preoperatively, which was reduced to 30.9 ± 6.41 after surgery. The mean TK in the parallel group was 36.4 ± 14 preoperatively and 42.1 ± 13.9 postoperatively. There was a significant reduction in TK in the oblique screws group compared with the second group ( P = 0.038). The insertion angle of pedicle screws had no significant effect on Cobb's angle and lumbar lordosis changes. However, oblique insertion of thoracic screws decreased thoracic kyphosis postoperatively, which could be considered a negative point. As such, the insertion of thoracic screws in a caudal direction should not be routinely used because of its lordogenic effect.

Predictors of the Pedicle Screw Misplacement in Patients with Thoracolumbar Fracture

Objectives: To investigate the prevalence and risk factors of the misplacement of the pedicle screw in patients with thoracolumbar spine fracture. Methods: Patients who underwent posterior stabilization procedure due to thoracolumbar spine fracture were included. Association between potential risk factors and the misplacement of the pedicle screw were evaluated by logistic regression analysis. Results: A total of 88 consecutive patients with thoracolumbar spine fracture who underwent posterior stabilization surgery using pedicle screws and rods (mean age 43 ± 14, male 52.3 %). On post-operation CT evaluation, 98 (14.8 %) pedicle screws were misplaced (34 thoracic screws and 64 lumbar screws) and the prevalence of the misplaced pedicle screw was not significantly different between thoracic and lumbar screws (13.2 % vs. 15.8 %, p = 0.347). Among risk factors including location of spine fracture, multiple spine fracture and location of screws, the AO classification of spine fracture was significantly associated with the misplacement of the pedicle screw (OR = 1.27, 95 % CI 1.06 - 1.53, p = 0.011). Conclusion: High grade spine fracture, as assessed by the AO classification, was significantly associated with pedicle screw misplacement in patients with thoracolumbar spine fracture.

Augmented reality in minimally invasive spine surgery: early efficiency and complications of percutaneous pedicle screw instrumentation

Augmented reality (AR) employs an optical projection directly onto the user's retina, allowing complex image overlay on the natural visual field. In general, pedicle screw accuracy rates have improved with increasingly use of technology, with navigation-based instrumentation described as accurate in 89%-100% of cases. Emerging AR technology in spine surgery builds upon current spinal navigation to provide 3-dimensional imaging of the spine and powerfully reduce the impact of inherent ergonomic and efficiency difficulties. This publication describes the first known series of in vivo pedicle screws placed percutaneously using AR technology for MIS applications. After IRB approval, 3 senior surgeons at 2 institutions contributed cases from June, 2020 - March, 2022. 164 total MIS cases in which AR used for placement of percutaneous pedicle screw instrumentation with spinal navigation were identified prospectively. 155 (94.5%) were performed for degenerative pathology, 6 (3.6%) for tumor and 3 (1.8%) for spinal deformity. These cases amounted to a total of 606 pedicle screws; 590 (97.3%) were placed in the lumbar spine, with 16 (2.7%) thoracic screws placed. Patient demographics and surgical metrics including total posterior construct time (defined as time elapsed from preincision instrument registration to final screw placement), clinical complications and instrumentation revision rates were recorded in a secure and de-identified database. The AR system used features a wireless headset with transparent near-eye display which projects intra-operative 3D imaging directly onto the surgeon's retina. After patient positioning, 1 percuntaneous and 1 superficial reference marker are placed. Intra-operative CT data is processed to the headset and integrates into the surgeon's visual field creating a "see-through" 3D effect in addition to 2D standard navigation images. MIS pedicle screw placement is then carried out percutaneously through single line of sight using navigated instruments. Time elapsed from registration and percutaneous approach to final screw placement averaged 3 minutes and 54 seconds per screw. Analysis of the learning curve revealed similar surgical times in the early cases compared to the cases performed with more experience with the system. No instrumentation was revised for clinical or radiographic complication at final available follow-up ranging from 6-24 months. A total of 3 screws (0.49%) were replaced intra-operatively. No clinical effects via radiculopathy or neurologic deficit postoperatively were noted. This is the first report of the use of AR for placement of spinal pedicle screws using minimally invasive techniques. This series of 164 cases confirmed efficiency and safety of screw placement with the inherent advantages of AR technologies over legacy enabling technologies.

Safety and Accuracy of Freehand Pedicle Screw Placement and the Role of Intraoperative O-Arm: A Single-Institution Experience.

Retrospective cohort study. The aim was to investigate the accuracy of pedicle screw placement by freehand technique and to compare revision surgery rates among three different imaging verification pathways. Studies comparing different imaging modalities in freehand screw placement surgery are limited. A single-institution retrospective chart review identified adult patients who underwent freehand pedicle screw placement in the thoracic, lumbar or sacral levels. Patients were stratified into three cohorts based on the intraoperative imaging modality used to assess the accuracy of screw position: intraoperative X-rays (cohort 1); intraoperative O-arm (cohort 2); or intraoperative computed tomography (CT)-scan (cohort 3). Postoperative CT scans were performed on all patients in cohorts 1 and 2. Postoperative CT scan was not required in cohort 3. Screw accuracy was assessed using the Gertzbein-Robbins grading system. A total of 9179 pedicle screws were placed in the thoracic or lumbosacral spine in 1311 patients. 210 (2.3%) screws were identified as Gertzbein-Robbins grades C-E on intraoperative/postoperative CT scan, 137 thoracic screws, and 73 lumbar screws ( P <0.001). Four hundred and nine patients underwent placement of 2754 screws followed by intraoperative X-ray (cohort 1); 793 patients underwent placement of 5587 screws followed by intraoperative O-arm (cohort 2); and 109 patients underwent placement of 838 screws followed by intraoperative CT scan (cohort 3). Postoperative CT scans identified 65 (2.4%) and 127 (2.3%) malpositioned screws in cohorts 1 and 2, respectively. Eleven screws (0.12%) were significantly malpositioned and required a second operation for screw revision. Nine patients (0.69%) required revision operations: eight of these patients were from cohort 1 and one patient was from cohort 2. When compared to intraoperative X-ray, intraoperative O-arm verification decreased the revision surgery rate for malpositioned screws from 0.37% to 0.02%. In addition, our analysis suggests that the use of intraoperative O-arm can obviate the need for postoperative CT scans.

P120. Augmented reality navigation for percutaneous thoracolumbar pedicle screws: a prospective clinical study

<h3>BACKGROUND CONTEXT</h3> Conventional navigation systems depend on a separate imaging system and use of passive infra-red cameras with a bulky dynamic reference frame (DRF) attached to the spine and to the instruments for live tracking. This often leads to 1) issues with line of sight 2) need for an invasive procedure to attach the DRF 3) lowered accuracy due to inadvertent bumping of the DRF and when point of interest is further from the location of the DRF and 4) a need for repeated re-registrations that can affect the surgical workflow and impact the procedure time. These common issues that impede the adoption of navigation can be bypassed using an Augmented Reality Surgical Navigation system (ARSN), that combines the use of superior quality 3D intra-operative imaging and optical camera based Augmented Reality Navigation (ARN), noninvasive dynamic patient monitoring and on-shaft optical trackers on the Jamshidi needles to provide real time visual feedback of instrument location, without relying on fluoroscopy. <h3>PURPOSE</h3> To determine the accuracy of percutaneous pedicle screw placement when using ARSN. <h3>STUDY DESIGN/SETTING</h3> A single-arm, prospective multicenter clinical study. <h3>PATIENT SAMPLE</h3> A total of 211 pedicle screws were placed percutaneously in 39 patients between levels T2 and S1. The predominant indication was trauma (42%). However, patients with instability of the spine due to degenerative and neoplastic diseases were also included. <h3>OUTCOME MEASURES</h3> Accuracy of pedicle screw placement according to Gertzbein grading (Grade 0: no breach; Grade 1: 4mm breach) determined by three independent reviewers. The median time required to insert the pedicle screw in the right location when using the system was also noted. <h3>METHODS</h3> Navigation was performed in a hybrid OR including surgical table, motorized flat detector C-arm with intraoperative 2D/3D imaging capabilities, optical video cameras integrated in the detector for ARN, and patient motion tracking using skin markers. The C-arm rotated 180 degrees in 10 seconds during acquisition, creating a 3D Cone-Beam CT (CBCT) of the area of interest of 4-8 levels. A disposable Jamshidi needle with optical markers etched on the shaft was used to guide the needle to the desired location in the vertebral body using ARN. <h3>RESULTS</h3> Overall accuracy (Gertzbein 0-1) was 98.1% (95% CI 95.2-99.5). For thoracic screws (n=69), accuracy was 95.7%, for lumbar screws (n=126) 99.2%. Grade 0 screws (no breach) were 93% overall (86% in thoracic and 96% in lumbar levels). Four screws were graded as 2 (2-4 mm breach), with a medial positioning. Three of them were in the upper thoracic spine. None was associated with a neurological consequence. No screw was highly misplaced (> 4mm error). Six screws (2.7%) were intraoperatively revised. Median time per screw was 6 minutes and 25 sec (± 3.3 min). <h3>CONCLUSIONS</h3> Use of ARN leads to a high rate of accurate pedicle screw placement. The use of ARSN favorably compares to screw placement times reported in literature. <h3>FDA DEVICE/DRUG STATUS</h3> ClarifEye surgical navigation system (Philips Healthcare) (Approved for this indication)

179. Safety and accuracy of freehand pedicle screw placement and the role of intraoperative O-arm: a single institution experience

179. Safety and accuracy of freehand pedicle screw placement and the role of intraoperative O-arm: a single institution experience

A systematic review with meta-analysis of the diagnostic test accuracy of pedicle screw electrical stimulation.

To provide a systematic review with meta-analysis providing evidence of the current diagnostic test accuracy (DTA) of pedicle screw electrical stimulation. A systematic database search on PubMed, Scopus and Web of Science was performed according to the PRISMA-DTA guidelines, and eligibility criteria applied to reduce the results to: (1) only journal articles reporting electrical stimulation of the pedicle screw head, (2) screw position confirmation by imaging techniques, and (3) enough information allowing the calculation of a 2 × 2 contingency table. Sample characteristics, image confirmation method, electrical current threshold and stimulation results were retrieved and analyzed using according to appropriate DTA analysis methods, and allowing the calculation of specificity, sensitivity for pedicle screws insertion at the lumbar and thoracic levels. Lumbar screw stimulation presents a higher sensitivity (0.586 [0.336, 0.798] and specificity (0.984 [0.958, 0.994]) than thoracic screws (sensitivity: 0.270 [0.096; 0.562]; specificity: 0.958 [0.931, 0.975]). The same is observed in terms of the diagnostic odds ratio for lumbar (88.32 [32.136, 242.962]) and thoracic (8.460 [2.139, 33.469]) levels. When performing a sub-group analysis, it is possible to divide the lumbar stimulation threshold as 8 and 10-12mA, and the thoracic threshold as 6 and 9-12mA. A threshold of 8mA at the lumbar level provides higher sensitivity and specificity. Increasing the threshold results in higher specificity but not sensitivity. In fact, at the range of 10-12mA, the diagnostic validity is too low to confer this technique any robust diagnostic validity.Similarly, at the thoracic level, lower threshold currents are associated with increased sensitivity, but their diagnostic validity is very low. Electrical stimulation of the pedicle screw can be used as an adequate diagnostic capability at the lumbar level with a threshold of 8mA. However, thoracic stimulation is currently not reliable, with very low sensitivity and diagnostic validity at 6mA or higher.

How to Optimize Pedicle Screw Parameters for the Thoracic Spine? A Biomechanical and Finite Element Method Study.

Pedicle screw study. The selection of pedicle screw parameters usually involves the surgeon's analysis of preoperative CT imaging along with anatomical landmarks and tactile examination. However, there is minimal consensus on a standardized guideline for selection methods on pedicle screws. We aimed to determine the effects of thoracic screw diameter to pedicle width on pullout strength determined by cortical bone purchase. Biomechanical study performed with human cadaveric thoracic vertebrae and experimentally validated three-dimensional finite element model instrumented with pedicle screws of various diameters. We used a variable (SD/PW) ratio to express the screw selection. We hypothesized a positive correlation between the pullout load determined by the bone purchase and the SD/PW. This relationship was first investigated in a validated finite element model considering bone purchase related to the strength of an upper thoracic vertebra. Then, the correlation to the entire spine is evaluated. The failure load ranged from 371.3 to 1601.0N, respectively, for 3 and 6mm screws. The determinant coefficient was increased to R2=.421 when a linear relationship between pullout load and the SD/PW ratio was used. The peak loads of 1216 and 1288N were found for an SD/PW ratio of .83. We have found that the screw pullout load is more correlated to SD/PW than other pedicle measures for a maximized SD/PW ratio of .83. This particular value should be considered the upper limit of the indicated SD/PW ratio and a means to determine the optimal screw diameter to enhance pullout strength.

Mechanical Analysis of 3 Posterior Fusion Assemblies Intended to Cross the Cervicothoracic Junction.

This was a biomechanical comparison study. The objective of this study is to evaluate the mechanical properties of 3 posterior spinal fusion assemblies commonly used to cross the cervicothoracic junction. When posterior cervical fusions are extended into the thoracic spine, an instrumentation transition is often utilized. The cervical rod (3.5 mm) can continue using thoracic screws designed to accept the cervical rods. Alternatively, traditional thoracic screws may be used to accept thoracic rods (5.5 mm). This requires the use of a 3.5-5.5 mm transition rod or a separate 5.5 mm rod and a connector to fix the 3.5 and 5.5 mm rod together. Fusion success depends on the immobilization of vertebrae, yet the mechanics provided by these different assemblies are unknown. Three titanium alloy posterior fusion assemblies intended to cross the cervicothoracic junction underwent static compressive bending, tensile bending, and torsion as described in ASTM F1717 to a torque of 2.5 Nm. Five samples of each assembly were attached to ultrahigh molecular weight polyethylene blocks via multiaxial screws for testing. Force and displacement were recorded, and the stiffness of each construct was calculated. The 2 assemblies that included a 5.5 mm rod were found to be stiffer and have less range of motion than the assembly that used only 3.5 mm rods. The results of this study indicate that incorporating a 5.5 mm rod in a fusion assembly adds significant stiffness to the construct. When the stability of a fusion is of heightened concern, as demonstrated by the ASTM F1717 vertebrectomy (worst-case scenario) model, including 5.5 mm rods may increase fusion success rates. Level V.

Multi-slice Computed Tomography Scan Assessment of Accuracy and Safety of Free-hand Pedicle Screw Fixation in Adolescent Idiopathic Scoliosis

Background Data: Various methods to help guidance of screw purchase in AIS have been described in the literature. Free-hand technique is a relatively easy and is as accurate as other methods. MSCT scan, the most accurate method of postoperative evaluation of screw purchase still needs more research. Purpose: The aim of this study is to evaluate the accuracy and safety of the pedicle screw fixation (PSF) with free-hand technique in AIS using postoperative MSCT scan. Study Design: Prospective clinical case study. Patients and Methods: In this prospectively study all patients with AIS underwent correction using the free-hand PSF were reported. All patients underwent whole spine X-ray and MSCT scan during the follow up. Screw purchases were evaluated according to Gertzbein Robbin classification. Results: A total of 45 patients were recruited for this study with mean age 14.7±1.7 including 39 females and 6 males. Of the total 870 pedicle screws, 85.1% (740) screws were accurate within the pedicle, while 14.9% (130) screws penetrated the pedicle including medial wall penetration in (5.9%) and lateral penetration in (9.0%). Overall, 18.3% of thoracic screws penetrated the pedicle while 5.9% of lumbar screws penetrated the pedicle. Correlation of screw purchase accuracy to age, sex, curve type, Cobb angle, spinal region showed no statistically significant correlation. Conclusions: The data of this prospective study suggest that pedicle screw fixation with free-hand technique in adolescent idiopathic scoliosis population appears to be an accurate and safe procedure. (2022ESJ263)

Pulse-train versus single-pulse t-EMG stimulation for intraoperative neurophysiologic monitoring of thoracic pedicle screws in adolescent idiopathic scoliosis

ObjectiveTo assess the PTS method in neuromonitoring of thoracic pedicle screws in a young cohort of AIS patients. The accuracy of both PTS (Pulse-train stimulation) and SPS (Single-pulse stimulation) techniques in the detection of misplaced thoracic screws was compared with special reference to the screws placed at the concavity and the convexity of the curve. Patients and methodsA single-center prospective clinical cohort study. Level of evidence II. Twelve AIS patients who underwent elective surgery were included in this study. Screw stimulation using repetitive constant-current stimulus train of variable intensities was first performed after screw insertion. SPS was performed immediately after PTS. Postoperatively, CT scan was used to check the final position of the screws. A total of 246 thoracic pedicle screws were placed. Thresholds of screws placed in the convexity and the concavity were compared. ResultsInvasion of the spinal canal was postoperatively confirmed in 29 of the pedicle screws. The SPS technique detected three (10.3%) of these screws using a threshold limit of 12 mA. The PTS technique detected 25 (86.2%) of the 29 misplaced screws using threshold of 30 mA (negative predictive value, 93.1%). When using a PTS threshold of < 20 mA, the positive predictive value was 70%. SPS did not detect any of the misplaced screws at the apex level of the scoliotic curves, and PTS detected 10 out of 17 of these screws. Overall, area under the ROC curve was 0.82 for PTS and 0.61 for SPS. ConclusionsPTS is a reliable method for detecting medially misplaced screws among young AIS patients undergoing scoliosis surgery. PTS provides more accurate predictions than SPS and improves the identification of screws invading the spinal canal at the apex or near the apex levels.

Evaluation of the implantation of transpedicular screws in spinal instrumentation with free-hand technique and navigation-assisted with intraoperative computed tomography: An analytical-positional study.

Spinal instrumentation using transpedicular screws has been used for decades to stabilize the spine. In October 2018, an intraoperative CT system was acquired in the Neurosurgery service of the University Hospital Complex of Vigo, this being the first model of these characteristics in the Spanish Public Health System, so we began a study from January 2015 to December 2019 to assess the precision of the transpedicular screws implanted with this system compared with a control group performed with the classical technique and final fluoroscopic control. The study was carried out in patients who required transpedicular instrumentation surgery, in total 655 screws were placed, 339 using the free-hand technique (Group A) and 316 assisted with intraoperative CT navigation (Group B) (p>0.05). Demographic characteristics, related to surgery and the screw implantation grades were assessed using the Gertzbein-Robbins classification. 92 patients were evaluated, between 12 and 86 years (average: 57.1 years). 161 thoracic screws (24.6%) and 494 lumbo-sacral screws (75.4%) were implanted. Of the thoracic screws, 33 produced a pedicle rupture. For the lumbo-sacral screws, 71 have had pedicle violation. The overall correct positioning rate for the free-hand group was 72.6% and for the CT group it was 96.5% (p<0.05). The accuracy rate is higher in thoracic-lumbar instrumentation in the navigation group versus free-hand group with fluoroscopic control.

Evaluation of the implantation of transpedicular screws in spinal instrumentation with free-hand technique and navigation-assisted with intraoperative computed tomography: An analytical-positional study

BackgroundSpinal instrumentation using transpedicular screws has been used for decades to stabilize the spine. In October 2018, an intraoperative CT system was acquired in the Neurosurgery service of the University Hospital Complex of Vigo, this being the first model of these characteristics in the Spanish Public Health System, so we began a study from January 2015 to December 2019 to assess the precision of the transpedicular screws implanted with this system compared with a control group performed with the classical technique and final fluoroscopic control. MethodsThe study was carried out in patients who required transpedicular instrumentation surgery, in total 655 screws were placed, 339 using the free-hand technique (Group A) and 316 assisted with intraoperative CT navigation (Group B) (p>0.05). Demographic characteristics, related to surgery and the screw implantation grades were assessed using the Gertzbein–Robbins classification. Results92 patients were evaluated, between 12 and 86 years (average: 57.1 years). 161 thoracic screws (24.6%) and 494 lumbo-sacral screws (75.4%) were implanted. Of the thoracic screws, 33 produced a pedicle rupture. For the lumbo-sacral screws, 71 have had pedicle violation. The overall correct positioning rate for the free-hand group was 72.6% and for the CT group it was 96.5% (p<0.05). ConclusionThe accuracy rate is higher in thoracic-lumbar instrumentation in the navigation group versus free-hand group with fluoroscopic control.