Thoracic Pedicle Screw Insertion Research Articles

Supraspinous ligament arc tangent guided freehand thoracic pedicle screw insertion technique: high parallelism between screws and upper endplate.

To propose a technique for placing pedicle screws in the thoracic spine using the Supraspinous ligament Arc Tangent (SLAT) as a guide to increase the safety and stability of screw placement. A retrospective analysis of postoperative anteroposterior and lateral x-ray images was performed for 118 patients with thoracic spine diseases who received conventional freehand technique from January 2016 to May 2020 and SLAT-guided technique since June 2020 to present. The diagnoses included thoracic spinal stenosis, deformity, fractures, infections, and tumors. The angle between the screw and the upper endplate was categorized as grade 1 (0°-5°), grade 2 (5°-10°), and grade 3 (>10°). Three surgeons with more than 10 years of experience in spinal surgery measured the angle between the screw and the upper endplate in the lateral view. Chi-square test was used for statistical analysis, and p < 0.05 was considered statistically significant. A total of 1315 pedicle screws were placed from T1 to T12 in all patients. In the conventional freehand technique group, 549 screws were grade 1, 35 screws were grade 2, and 23 screws were grade 3. In the SLAT-guided freehand technique group, 685 screws were grade 1, 15 screws were grade 2, and 8 screws were grade 3. The data of each group was p < 0.05 by Chi-squared test, which was statistically significant, indicating that the SLAT-guided freehand technique resulted in a higher rate of parallelism between the screws and the upper endplate. All patients underwent intraoperative neurophysiological monitoring, immediate postoperative neurological examination, postoperative x-ray examination, and assess the eventual recovery. The screws were safe and stable, and no complications related to pedicle screw placement were found. The SLAT-guided freehand technique for placing pedicle screws in the thoracic spine can achieve a higher rate of screw-upper endplate parallelism, making screw placement safer and more accurate. Our method provides a convenient and reliable technique for most spinal surgeons, allowing for increased accuracy and safety with less fluoroscopic guidance.

An investigation of the efficiency of pedicle screw simulator software in thoracic

Aim: Fennell et al. describe a simple, effective freehand technique for thoracic pedicle screw insertion. In this study, we aimed to compare the patients undergoing upper thoracic pedicle screw insertion with the Fennell technique simulated on Pedicle Screw Simulator (PSS) and those recruited to the same procedure utilizing C-arm fluoroscopy.&#x0D; Material and Method: First, we uploaded pre-operative CT images of 12 patients to the PSS module, which was used in our study to calculate the screw angle and visualize the pedicle screw entry point and trajectories. Then, we created three-dimensional vertebral models of the patients to simulate screw placement using visualization tool kit (VTK), open-source software for 3D computer graphics and visualization, available free of charge as part of 3D Slicer. Next, we placed pedicle screws through pre-determined anatomic regions. C-arm fluoroscopy-guided pedicle screws were placed in the patients in the control group. The amount of bleeding, operation times and correct screw placement data were recorded in both groups.&#x0D; Results: 24 patients were included in the study. The mean age of the patients was 32.3±4.1 years. We applied 80 pedicle screws to Group 1 and 72 to Group 2. According to the malposition classification by Rao et al. on postoperative CTs, 68 patients in Group 1 were classified as Grade 0, 8 as Grade 1, 4 as Grade 2. Yet, there were no statistical differences between the groups by Rao et al.’s classification (p&gt;0.05). While the mean operation time of Group 1 was 138±34 minutes, it was 162±44 minutes in Group 2. The groups significantly differed by operation time (p

Are 3D Printing Templates an Advantage in Upper Thoracic Pedicle Screw Fixation?

BackgroundThis study aims to compare the clinical results of patients with upper thoracic vertebral fractures treated with pedicle screw and posterior spinal fusion with preoperative surgical planning and 3-dimensional (3D) modeling and patients treated with freehand screws.MethodsFifty patients who underwent pedicle screw placement with a diagnosis of upper thoracic fracture between June 2018 and October 2020 were included in our study. Pedicle screws were used in 25 patients (group 1) after the planning was completed with the help of 3D preoperative printing and modeling. Pedicle screws were applied in 25 patients in the control group (group 2) using the freehand technique. Intraoperative bleeding amount, operation time, and correct screw placement data in both groups were recorded.ResultsThe operation time was 134 ± 22 minutes for group 1 and 152 ± 38 minutes for group 2. The difference in operation times was found to be statistically significant (p < 0.05). Based on axial and sagittal reconstruction images, the accuracy rate of pedicle screw placement (grades 0 and 1) in group I was 96.6% compared to 83.6% in group II. The minor perforation rate (grade 1, <2 mm) was 5.8% in group I compared to 11.8% in group II. The moderate perforation rate (grade 2, 2-4 mm) was 3.4% in group I compared to 14% in group II. The severe perforation rate (grade 3, >4 mm) was 2.3% in group II; however, misplaced screws were not associated with neurological deficits. The difference in overall accuracy rates between the two groups was significant (p < 0.05).ConclusionsFor 3D models of upper thoracic pedicle screw insertion, guide plates can be produced inexpensively and individually. It provides a new method for the accurate placement of upper thoracic pedicle screws with high accuracy and secure use in screw insertion.

In-vivo clinical validation of perpendicular to superior articular process as thoracic pedicle trajectory: A retrospective case series of 60 pediatric scoliosis

Study Design: This is a retrospective case series study. Objective: Thoracic pedicle screw insertion can be technically challenging because of narrow pedicles. Placement of thoracic pedicle screws in pediatric scoliosis and adult deformity surgeries, due to three-dimensional rotation of vertebrae, is even more challenging because the usual landmarks are less evident, and the sagittal trajectory is more difficult to correctly orientate due to the vertebral rotation. We describe a variation of freehand technique to guide sagittal trajectory of thoracic pedicle screw. Materials and Methods: The inferior articular process of cranially adjacent vertebrae is osteotomized using a Capener Gouge to expose the superior articular process (SAP) of the thoracic vertebrae to be instrumented. An O’Connell dissector is then placed flush on the SAP. The main shaft of the dissector is at right angle to the base plate; pedicle finder is placed parallel to the shaft and follows the same sagittal trajectory as the shaft. Results: A total of 390 pedicle screws were identified in a consecutive series of 60 scoliosis patients inserted using this technique. Only one screw was revised for lateral breach. There was no intra-operative complication or neurological sequelae in any of our patients. Conclusion: Freehand pedicle screw placement remains a very common technique, used particularly by pediatric scoliosis surgeons. One of the drawbacks of previous reports of the freehand technique is that the sagittal trajectory is not clearly defined. Our technique fills this gap, and this series demonstrates that the technique produces a reliable and consistent result.

Accuracy of the freehand (fennell) technique using a uniform entry point and sagittal trajectory for insertion of thoracic pedicle screws: A computed tomography-based virtual simulation study.

Thoracic spine has complex pedicle anatomy with a narrow canal diameter which makes pedicle screw insertion challenging. Fennell et al. have described a simple freehand technique of thoracic pedicle screw placement. We have tested the accuracy of Fennell technique using computed tomography-based (CT-based) simulation model with pedicle screw simulator (PSS). Normal CT thoracic spine obtained from CT thorax data of five patients were used in the 3D slicer environment using PSS for simulation. Entry points and axial trajectory as described by Fennell et al. and a sagittal trajectory parallel to the superior endplate were used for simulating the freehand technique using EA (entry angle) mode in the PSS. An ideal trajectory through the midsection of the pedicle from the same entry point and a sagittal trajectory parallel to the superior endplate were simulated using the ET (Entry Target) mode. Angle predicted by the software for an ideal axial trajectory was compared with the Fennell technique and this angle difference was noted at all the levels. Presence of pedicle breach was noted while simulating the Fennell technique. A total of 240 thoracic pedicle screw insertions were simulated, 120 screws by each technique. A sagittal trajectory parallel to the superior endplate caused no pedicle breach in the cranial-caudal direction at any level. No medial or lateral breach was noted while using an axial trajectory of 30° at T1-T2 and 20° from T3-T10. A 20° axial trajectory at T11 and T12 resulted in a breach of the medial cortex and the ideal mean axial angles at T11 and T12 were 2.8° and 6.5°, respectively. Fennell technique was effectively simulated using PSS. A uniform entry point and sagittal trajectory parallel to the superior endplate serves as a useful guide for freehand insertion of thoracic pedicle screws. At T11 and 12, ideal axial trajectories are less than 10°.

Computer-assisted surgery navigation of pedicle screw insertion by standardized trainees

Objective: To assess the precision and efficiency computer-assisted surgery navigation of pedicle screw insertion by standardized trainees. Methods: From September 2013 to June 2016, 360 thoracic pedicle screws were inserted into 100 patients by standardized trainees (n = 30). Screws on the left side were inserted by hands (control group), while the other side were inserted under the guidance of computer-assistant navigation system (guided group). The insertion time and volume of blood lost by each screw were retrospectively analyzed. The precision ratio was assessed by computerized tomography (CT) scan after operation. Results: The time consumed in screw insertion was significantly shorter in the guided group than that in the control group. The blood lost volume was lesser in the guided group. Post-operation CT scan revealed higher precision in the guided group than that in the control group. Conclusion: Computer-assistant navigation system facilitates the learning of standardized trainees, and reduces the time-consuming and bleeding in thoracic pedicle screw insertion.

Novel design for a customized, 3D-printed surgical template for thoracic spinal arthrodesis.

The integration of computer-aided design/computer-aided manufacturing (CAD/CAM) tools and medicine is rapidly developing for designing medical devices. A novel design for a 3D-printed patient-specific surgical template for thoracic pedicle screw insertion, using a procedure based on reverse engineering, is presented. The surgeon chooses the entry point on the vertebra. The optimal insertion direction and the size of the screws are defined via an algorithm on the basis of a patient-specific vertebra CAD model. The template features an innovative shape for a comfortable and univocal placement and a novel disengaging device. Three spinal fusions were performed to test the template. Excellent results were achieved in terms of the accuracy of the screw positioning, reduction in surgery duration, and number of X-rays. A novel design for a customized, 3D-printed surgical template for thoracic spinal arthrodesis was presented, and improvements in terms of precision, duration, and safety were achieved without changing the standard procedure.

Free-Hand Pedicle Screw Insertion of Thoracic Spine Using Fennell Technique: Initial Results and Review of Literature

Abstract Aim of the Study This article aims to study the safety and feasibility of Fennell technique of free-hand pedicle screw insertion in thoracic spine. Methods Consecutive 10 patients in whom 40 thoracic pedicle screw were inserted using Fennell’s technique were included in the study. Postoperative computed tomography scan was done in all the patients. Breach in individual pedicle was analyzed using Gertzbein classification. Results A total of 40 screws were placed in the thoracic spine in 10 patients by free-hand technique described by Fennell et al. Out of 40 pedicle screws, 26 were placed at the D10 to D12 level, 8 screws were placed at the D7 to D9 level, and 6 screws were placed at the D1 to D6 level. There was one pedicle with grade 1 lateral breach and one pedicle with grade 1 medial breach as per Gertzbein classification. All other screws were contained within the pedicle (Gertzbein grade 0). None of the patients had any added deficits or wound complications in the postoperative period. Conclusion Thoracic pedicle screw insertion is challenging in nature because of the anatomic variability and proximity of critical structures to the pedicles. Our experience suggests that Fennell technique is a reliable technique, which can be used to place thoracic pedicles consistently, with acceptable rates of pedicle breach. A study involving larger number of patients might prove to establish this technique as an easily reproducible and safe technique for free-hand pedicle screw insertion in thoracic spine.

Cortical Bone Trajectory Screws for Fixation Across the Cervicothoracic Junction: Surgical Technique and Outcomes.

Study Design:Clinical case series describing a novel surgical technique.Objective:Stabilization across the cervicothoracic junction (CTJ) poses technical difficulties which make this procedure challenging. The transition from cervical lordosis to thoracic kyphosis and the orientation of the lateral masses of the cervical spine compared with the pedicles of the thoracic spine create the need to accommodate for 2 planes of alignment when placing instrumentation. A novel surgical technique for instrumentation across the cervicothoracic junction is described.Methods:The use of cortical bone trajectory (CBT) technique for pedicle fixation in the upper thoracic spine is described in combination with cervical lateral mass or pedicle screws. The application in our first 12 patients for stabilization across the CTJ is described. Two case presentations illustrate the technique.Results:All the patients had rod screw constructs without the need to skip levels, there was no requirement for transverse connectors and only 1 plane of contouring was required.Conclusions:The use of CBT technique has not been described for the upper thoracic spine. This technique avoids many technical problems associated with posterior instrumentation of the CTJ. The facility of their use in this application arises from the similar coronal plane entry points as the cervical lateral mass screws compared with the more lateral starting point of traditional thoracic pedicle screws. The technique has clinical equipoise to traditional thoracic pedicle screw insertion but with the benefits of an easier ability to perform the instrumentation and saving levels of fusion.

Evaluation of a more ventral starting point for thoracic pedicle screws: higher maximal insertional arc and more medial and safer screw angulation.

OBJECTIVETo demonstrate that a more ventral starting point for thoracic pedicle screw insertion, produced by aggressively removing the dorsal transverse process bone down to the superior articular facet (SAF), results in a larger margin for error and more medial screw angulation compared to the traditional dorsal starting point (DSP). The margin for error will be quantified by the maximal insertional arc (MIA).METHODSThe study population included 10 consecutive operative patients with adult idiopathic scoliosis who underwent primary surgery. All measurements were performed using 3D visualization software by an attending spine surgeon. The screw starting points were 2 mm lateral to the midline of the SAF in the mediolateral direction and in the center of the pedicle in the cephalocaudal direction. The DSP was on the dorsal cortex. The ventral starting point (VSP) was at the depth of the SAF. Measurements included distance to the pedicle isthmus, MIA, and screw trajectories.RESULTSTen patients and 110 vertebral levels (T1-11) were measured. The patients' average age was 41.4 years (range 18-64 years). The pedicle isthmus was largest at T1 (4.04 ± 1.09 mm), and smallest at T5 (1.05 ± 0.93 mm). The distance to the pedicle isthmus was 7.47 mm for the VSP and 11.92 mm for the DSP (p < 0.001). The MIA was 15.3° for the VSP and 10.1° for the DSP (p < 0.001). Screw angulation was 21.7° for the VSP and 16.8° for the DSP (p < 0.001).CONCLUSIONSA more ventral starting point for thoracic pedicle screws results in increased MIA and more medial screw angulation. The increased MIA represents an increased tolerance for error that should improve the safety of pedicle screw placement. More medial screw angulation allows improved triangulation of pedicle screws.

Is free hand a safe technique for thoracic pedicle screw insertion? A CT based randomised study

Is free hand a safe technique for thoracic pedicle screw insertion? A CT based randomised study

Computer-assisted surgery navigation of pedicle screw insertion by standardized trainees

&lt;p&gt;&lt;strong&gt;Objective:&lt;/strong&gt; To assess the precision and efficiency computer-assisted surgery navigation of pedicle screw insertion by standardized trainees. &lt;strong&gt;Methods&lt;/strong&gt; From September 2013 to June 2016, 360 thoracic pedicle screws were inserted into 100 patients by standardized trainees (n = 30). Screws on the left side were inserted by hands (control group), while the other side were inserted under the guidance of computer-assistant navigation system (guided group). The insertion time and volume of blood lost by each screw were retrospectively analyzed. The precision ratio was assessed by computerized tomography (CT) scan after operation. &lt;strong&gt;Results&lt;/strong&gt; The time consumed in screw insertion was significantly shorter in the guided group than that in the control group. The blood lost volume was lesser in the guided group. Post-operation CT scan revealed higher precision in the guided group than that in the control group.&lt;strong&gt; Conclusion&lt;/strong&gt; Computer-assistant navigation system facilitates the learning of standardized trainees, and reduces the time-consuming and bleeding in thoracic pedicle screw insertion. Orthodontics training is the most important low-grade physician training in the orthopedic department1,2. Due to the complexity of spinal anatomy, professional required and high risk of spinal surgery, thoracic pedicle screw implantation has become a very demanding technique. Furthermore, the spine surgery learning is not conducive to the trainees. Since 2013, our department started to use the computer-assisted three-dimensional navigation technology to guide the implantation of screws3. We found that the computer-assisted navigation technology has greater advantage when compared with the traditional hand-implanted technology.&lt;/p&gt;

Are computer numerical control (CNC)-manufactured patient-specific metal templates available for posterior thoracic pedicle screw insertion? Feasibility and accuracy evaluation.

Accurate and safe posterior thoracic pedicle insertion (PTPI) remains a challenge. Patient-specific drill templates (PDTs) created by rapid prototyping (RP) can assist in posterior thoracic pedicle insertion, but pose biocompatibility risks. The aims of this study were to develop alternative PDTs with computer numerical control (CNC) and assess their feasibility and accuracy in assisting PTPI. Preoperative CT images of 31 cadaveric thoracic vertebras were obtained and then the optimal pedicle screw trajectories were planned. The PDTs with optimal screw trajectories were randomly assigned to be designed and manufactured by CNC or RP in each vertebra. With the guide of the CNC- or RP-manufactured PDTs, the appropriate screws were inserted into the pedicles. Postoperative CT scans were performed to analyze any deviations at entry point and midpoint of the pedicles. The CNC group was found to be significant manufacture-time-shortening, and cost-decreasing, when compared with the RP group (P<0.01). The PDTs fitted the vertebral laminates well while all screws were being inserted into the pedicles. There were no significant differences in absolute deviations at entry point and midpoint of the pedicle on either axial or sagittal planes (P>0.05). The screw positions were grade 0 in 90.3% and grade 1 in 9.7% of the cases in the CNC group and grade 0 in 93.5% and grade 1 in 6.5% of the cases in the RP group (P=0.641). CNC-manufactured PDTs are viable for assisting in PTPI with good feasibility and accuracy.

Accuracy of free hand technique of transpedicular screw fixation in correction of spinal deformities

Introduction: Pedicular screw fixation is now the novel technique to correct spinal deformities. Navigation or CT guided systems are not easily available in Indian scenario. Free hand technique of pedicle screw insertion is commonly practiced for degenerative spine and traumatic spine with fluoroscopic guidance, but for deformed spine fluoroscopy may not be always helpful. AIM: we intend to evaluate accuracy and safety free hand technique in kyphoscoliotic spine. Material and Methods: Twenty consecutive patients suffering from kyphoscoliosis underwent posterior stabilization using a total of 260 titanium/stainless steel transpedicular screws. The position of the screws inserted into the deformed spine was evaluated by postoperative computed axial tomography (CAT) scans. All patients underwent 3-mm thin-section postoperative CT. Pedicle perforations were classified as either medial or lateral breech and distance was measured of breach. Results: Of the 260 screws inserted into the deformed scoliotic spine 27 screws showed moderate lateral cortical perforation whereas 11 screws showed moderate medial cortical breech. These screws showed cortical perforation in the range of 2.1-4.0mm.One screw each showed cortical breech in the range of 4.1-6.0mm on medial and lateral side. Conclusion: This study concludes that with good knowledge of anatomy of spine, free hand thoracic pedicle screw insertion technique for the surgical treatment of normal and deformed thoracic spines without any radiographic guidance and/or intraoperative tracking devices appears to be a safe, and reliable procedure.

Different potential risk of injury from thoracic pedicle screw insertion between left and right main-stem bronchus in Lenke 1 type adolescent idiopathic scoliosis.

The changed relative anatomic position of trachea with increased potential risk of injury from thoracic pedicle screw (TPS) has been reported in Lenke 1 type adolescent idiopathic scoliosis (AIS) patients. However, such change of main-stem bronchus has not been investigated. The purposes of this study were to evaluate the altered positions of both left and right main-stem bronchus in Lenke 1 type patients and to assess the potential risks of main-stem bronchus injuries from TPS screw insertion in these patients. A total of 19 Lenke 1 type AIS patients and 15 normal teenagers were included. Axial computed tomography (CT) images at T5 level were obtained in all these subjects to evaluate the main-stem bronchus-vertebral distance (MVD, the closet distance between the main-stem bronchus and vertebral body) and main-stem bronchus-vertebral angle (MVA, defined as 0° when the main-stem bronchus was located directly lateral to the left and 180° when directly lateral to the right) on both left and right sides. The percentage of main-stem bronchus located adjacent to vertebrae and in the direction of screw passage was calculated to analyze potential risks of injuries from pedicle screw placement. Both the average left and right MVD were significantly smaller in AIS patients when compared with normal teenagers at T5 level (P<0.05). Both the mean left and right MVA were lower in AIS patients than those in normal teenagers at T5 level (P<0.05). All the AIS patients (100%) had the right main-stem bronchus with high risk of injury from right TPS placement and only five AIS patients (26.3%) had left main-stem bronchus with high risk of injury from left TPS placement at T5 level. No main-stem bronchus was found to be at risk of injury from TPS placement on both two sides in normal teenagers at this level. Both the right and left main-stem bronchus were located much closer to the vertebrae in Lenke 1 type AIS patients when compared with normal teenagers. However, the potential risk of injury of main-stem bronchus from TPS placement was higher on the right side than that on the left side.

Computer-Assisted Screw Size and Insertion Trajectory Planning for Pedicle Screw Placement Surgery.

Pathological conditions that cause instability of the spine are commonly treated by vertebral fixation involving pedicle screw placement surgery. However, existing methods for preoperative planning are based only on geometrical properties of vertebral structures (i.e., shape) without taking into account their structural properties (i.e., appearance). We propose a novel automated method for computer-assisted preoperative planning of the thoracic pedicle screw size and insertion trajectory. The proposed method extracts geometrical properties of vertebral structures by parametric modeling of vertebral bodies and pedicles in three dimensions (3D), and combines them with structural properties, evaluated through underlying image intensities in computed tomography (CT) images while considering the guidelines for pedicle screw design. The method was evaluated on 81 pedicles, obtained from 3D CT images of 11 patients that were appointed for pedicle screw placement surgery. In terms of mean absolute difference (MAD) and corresponding standard deviation (SD), the resulting high modeling accuracy of 0.39±0.31 mm for 3D vertebral body models and 0.31±0.25 mm for 3D pedicle models created an adequate anatomical frame for 3D pedicle screw models. When comparing the automatically obtained and manually defined plans for pedicle screw placement, a relatively high agreement was observed, with MAD ±SD of 0.4±0.4 mm for the screw diameter, 5.8±4.2 mm for the screw length, 2.0±1.4 mm for the pedicle crossing point and 7.6±5.8(°) for screw insertion angles. However, a statistically significant increase of 48±26% in the screw fastening strength in favor of the proposed automated method was observed in 99% of the cases.

Defining the Differences in Transverse Plane Trajectories for Thoracic Pedicle Screw Insertion: Anatomic Versus Medial

Study DesignComparing thoracic pedicle screw trajectories, screw lengths, and starting points by examining osteologic specimens. ObjectiveDescribe a medial screw trajectory (MST) compared to a screw trajectory along the anatomic pedicle angle (APA) in terms of trajectory, screw length, and starting point. Summary of Background DataAlthough thoracic pedicle screw insertion is commonly used for posterior fusion and instrumentation, there is little data to quantify an MST that avoids the great vessels and allows for greater screw purchase. MethodsThirty adult female skeleton thoracic vertebral columns from the University of New Mexico Maxwell Museum of Anthropology Osteology Collection were photographed from axial and right and left lateral views from T1 to T12. Axial plane measurements included APA and MST (both measured from the midline), screw lengths, and APA/MST intersection on the superior articular facet (SAF). The MST was defined as an insertion angle through the midpoint of the pedicle isthmus intersecting the anterior midpoint of the vertebral body. The intersection of each trajectory with the SAF was measured in relation to the lateral base of the SAF, reported as a percentage of the SAF base width from the lateral SAF border. ResultsAt every vertebral level, the APA was different from the MST for angle, screw length, and SAF intersection (p < .0001), with the largest difference at T12. The T12 differences were APA versus MST angles (−25.5°, 95% CI −22.7° to −28.4°), screw lengths (11.0 mm, 95% CI 9.2 mm to 12.9 mm), and percentage of SAF width from the lateral border of the SAF base (38.6%, 95% CI 29.1% to 48.1%). ConclusionsThe MST was approximately 8° to 10° greater at T1–T10 (19° at T11 and 25° at T12) than the traditional APA insertion angle. This resulted in a much more lateral starting point on the SAF and longer screw length, greatest at T12.

Cadaver Training Module for Teaching Thoracic Pedicle Screw Placement to Residents

Surgical training using simulators has been shown to be highly effective but is not available for some applications and is too expensive for many programs. The authors piloted a cadaver-based module with the goal of objectively measuring and significantly improving orthopedic residents' surgical skills in placing thoracic pedicle screws, an advanced procedure. An experienced spine surgeon placed thoracic pedicle screws in 7 cadavers (T1-T12) to establish the skilled accuracy rate. For this pilot study, 3 orthopedic residents unfamiliar with the procedure were given didactic training for safe thoracic pedicle screw insertion. Each resident instrumented alternating sides of 5 consecutive cadavers (T1-T12). Screw positions were graded by computed tomography in a blinded fashion, with accuracy defined as no shank breach of the pedicle or vertebral body. Results were reviewed with the residents, instruction was repeated, and alternating sides of 5 cadavers were instrumented by the residents. The experienced surgeon accurately placed 67 (82%) of 82 pedicle screws. Residents accurately placed 80 (44%) of 180 pedicle screws in the initial set of specimens and 105 (58%) of 180 pedicle screws in the second set of specimens (P=.01). Accuracy varied significantly among residents before but not after computed tomography review. The study's results show that a cadaver-based training module that resembles the clinical setting can be used to teach complex surgical skills to orthopedic residents.

Asymmetric T5 Pedicle Subtraction Osteotomy (PSO) for complex posttraumatic deformity

• Posterior approach for vertebral body access • Intraoperative navigation (O-arm) for insertion of high thoracic pedicle screws in major spinal deformities • To learn correction strategy in complex fixed sagittal and coronal spinal deformities • Performing an asymmetric PSO at the upper thoracic segment • Managing the spinal cord for upper thoracic spinal osteotomies • Correction technique by simultaneous internal and external manoeuvres.

The Superior Articular Process as an External Landmark for Determining the Transverse Plane Angulation of Thoracic Pedicles

Study DesignComputed tomographic (CT) study of thoracic spine pedicles. ObjectiveTo analyze the usefulness of the superior articular process (SAP) as an external landmark for determining the transverse plane angulation of thoracic pedicles. Summary of Background DataThe use of thoracic pedicle screws has become commonplace. Although most authors report them to be safe, their use poses a risk to neurovascular structures. Previous studies have provided useful information regarding thoracic pedicle anatomy, but this information is difficult to apply intra-operatively. To avoid neurovascular injury, it is important to determine the correct transverse plane angulation of screw insertion. MethodsTwo separate investigators reviewed thoracic spine CT scans of 53 patients, 26 years of age or younger. Measurements were taken of the angular relationship of the pedicle and the SAP of T4–T11. A 90° angle was subtended from a line parallel to the SAP with a starting point at the midpoint of the lateral half of the SAP. Measurements were then adjusted laterally for medial breeches and medially for lateral breeches, to align the trajectory down the middle of the pedicle. The degree of correction was recorded. Each investigator made 3 sets of measurements. We calculated kappa values to assess intra-observer/interobserver agreement. ResultsOf the 4,008 measurements, 95.2% were contained within bone, leaving 4.8% pedicle violations. The average correction made for medial and lateral breeches was 6.3% and 6.7%, respectively. The first rater had 92.6% agreement, and an intra-observer kappa value of 0.57. The second rater had a 95.3% agreement and an intra-observer kappa value of 0.40. ConclusionsThe results support the hypothesis that the SAP can be a useful external landmark for determining the transverse plane angulation of thoracic pedicle screw insertion.