Pedicle Screw Entry Point Research Articles

Three-Dimensional Printing Technology Based on Digital Orthopedics: 5-Point Positioning Point-Contact Pedicle Navigation Template in the Case of Scoliosis and Complex Pedicle.

Imperfect fitting of the navigation template leads to prolonged surgery time and increased blood loss. These problems have not been effectively addressed in previous research. This study explores the efficacy of a novel 5-point positioning point-contact pedicle navigation template in complex pedicle situations in scoliosis. This study employed a retrospective controlled design. From November 2019 to November 2023, 28 patients with scoliosis and complex pedicle were selected and underwent scoliosis correction surgery. A 5-point positioning point-contact pedicle navigation template was used intraoperatively to guide pedicle screw placement. Matched with 56 historical cases as a control group. The analysis included screw placement time, screw placement bleeding volume, fluoroscopy frequency, manual repositioning frequency, screw placement accuracy and grade, screw placement complications, and main curve correction rate. Continuous variables were compared using the independent samples t-test. Categorical data were analyzed with the chi-square test. All 28 patients successfully underwent surgery, with a total of 268 pedicle screws placed. The surgery duration ranged from 220 to 410 min, with an average of (283.16 ± 51.26) min. Intraoperative blood loss ranged from 630 to 1900 mL, with an average of (902.17 ± 361.25) mL. Pedicle screw placement time ranged from 60 to 130 min, with an average of (85.24 ± 24.65) min. Pedicle screw placement bleeding volume ranged from 40 to 180 mL, with an average of (76.47 ± 42.65) mL. Fluoroscopy frequency ranged from 3 to 7 times, with an average of (4.31 ± 1.14) times. Manual repositioning frequency ranged from 0 to 2 times, with an average of (0.46 ± 0.58) times. Pedicle screw placement grades: Grade I: 237 screws; Grade II: 25 screws; Grade III: 6 screws; Grade IV: 0 screws. There were no screw-related complications. The correction rate ranged from 46% to 68%, with an average of (55.83 ± 9.22)%. Compared to the experienced screw group, the differences in screw placement time, screw placement bleeding volume, fluoroscopy procedures, and manual redirections were statistically significant (p < 0.05). The 5-point positioning point-contact pedicle navigation template features a claw-like structure that securely adapts to various deformed vertebral facet joints, avoiding drift phenomena and ensuring accurate screw placement. Its pointed contact structure with the lamina of the spine avoids extensive and complete detachment of posterior structures, reducing blood loss, surgery time, and trauma. Predesigned pedicle screw entry points and directions reduce fluoroscopy frequency and surgery time.

Pulmonary disorders in pregnancy – Volume 85 multiple choice questions - Questions

The height and width of the iliac wing were measured using three-dimensional computed tomography(3D-CT), and the extent to which the iliac wing occluded the entry point of the 5th lumbar vertebra pedicle screw(L5PS) was observed and graded according to severity. The overall goal was to study the influence of the height and width of the iliac wing on L5PS insertion.This study included 350 cases (179 males and 171 females) where the L1-S2 region was obtained. We reconstructed 3D-CT in our study for anatomic analysis. The width and height of the iliac wing were measured on CT axial and oblique sagittal images, respectively. The degree of the L5PS entry point was determined by the data of iliac wing width and height, and divided into 0, I, II and III levels. The association between width and height of the iliac wing among males and females was also analyzed in this paper.The incidence of shielding of the L5PS entry point by the height and width of the ilium wing were 20.0 % and 19.4 %, respectively. The overall incidence of obstruction of L5PS by the width of the ilium wing was 27.3 % in males and 12.3 % in females. In total, there were 27, 14, and 8 male patients with level I, II, and III shielding, respectively. There were 12, 7, and 2 females with level I, II, and III shielding, respectively. The overall incidence with which the height of the ilium wing obstructed L5PS was 24.0 % in males and 14.6 % in females, of which there were 23 males with level Ⅰ shielding, 16 males with level Ⅱ shielding, 4 males with level Ⅲ shielding, 13 females with level Ⅰ shielding, 8 females with level Ⅱ shielding, and 4 females with level Ⅲ shielding.The height of the ilium caused obstruction of the L5PS more frequently than the width of the ilium, and males had a higher incidence of iliac wing occlusion than females at both the height and width. The degree of L5PS entry point shielding by the iliac wing width along the horizontal axis was not completely consistent with that of L5PS shielding on the oblique sagittal plane.

The "V" Sign: A Reliable Anatomic and Radiographic Landmark for Posterior Percutaneous S1 Screw Placement.

Sacral (S1) pedicle screw misplacement in posterior percutaneous fixation (PPF) can be related to anatomical variability and a lack of reliable radiographic landmarks. This study highlights a reproducible anatomical landmark (the "V" sign) for the safe localization of the S1 pedicle entry point under fluoroscopy. Human cadavers (n = 14) were dissected for the anatomical description of the "V" landmark and its relationship with the entry point of the S1 pedicle screw. The "V" landmark was defined medially by the lateral border of the superior articulating process of S1 and laterally by the posterior projection of the sacral ala. The mean distance was measured between the bottom point of the "V" landmark and the anatomical entry point to the S1 pedicle (V-S1 entry point distance). A similar measurement was conducted on computed tomography (CT) scans of 135 patients who underwent PPF using the "V" sign as a landmark for S1 pedicle screw placement (270 screws). These were retrospectively evaluated for appropriateness of S1 screw entry points and for proper S1 screw alignment and breaches. In the 14 cadavers, irrespective of the laterality and sex, the V-S1 entry point distance averaged 11.7 mm. On the medial-lateral axis, all entry points converged within 2 mm of a vertical line intersecting the base of the "V." Additionally, the CT scan analysis (135 patients, 270 screws) revealed an optimal entry point for 100% of the screws and a 3.3% (n = 9 screws) breach rate. Six of the 9 identified breaches were minor, and only 1 (0.4% of the 270 screws) warranted revision. The "V" sign serves as a reliable anatomical and radiographic landmark for identifying the S1 pedicle entry point under fluoroscopic guidance. This landmark can help surgeons overcome the radiographic ambiguity of the sacral anatomy and ultimately reduces the rate of S1 pedicle screw misplacement. Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Perpendicular probing and screwing technique: A simple method for accurate pedicle screw placement based on the human internal reference frame for angle estimation.

The pedicle screw (PS) is widely used for spinal fixation surgery. However, PS malpositioning can cause critical complications; thus, the accuracy of ascertaining PS trajectory is paramount. This study aimed to demonstrate the accuracy and safety of a simple and cost-effective PS placement technique using a human internal reference frame for angle estimation. Ex vivo lumbar porcine spine samples were fixed to a wooden board with rostrocaudal and mediolateral rotational angles adjusted by two angle vises. PS entry points (EPs) were identified using clear anatomical vertebral landmarks. PS placement was performed on one side using the perpendicular probing and screwing technique (PPST), wherein the attitude angle of the sample was adjusted such that the longitudinal axis of the target pedicle was perpendicular to the ground. The pedicle probe and PS driver were manually maintained perpendicular to the ground during probing and PS placement. PS placement on the contralateral side was performed freehand as a control. Offsets between the preoperatively planned and implanted PS rotational angles measured using computed tomography for PPST and freehand method were analyzed. Pedicle wall penetration was also evaluated. The mean ± standard error of the medial rotational offsets was 5.83° ± 0.57° in the freehand group versus 2.89° ± 0.31° in the PPST group (p <0.001), and the rostrocaudal rotational offsets were 4.81° ± 0.65° in the freehand group versus 2.92° ± 0.45° in the PPST group (p = 0.01). The mean pedicle wall penetration distance was significantly reduced by PPST (0.28 ± 0.12 mm vs 0.80 ± 0.17 mm in the freehand group, p = 0.0071). Thus, PPST improved PS positioning accuracy, resulting in reduced pedicle wall penetration and increased PS placement safety. This simple technique is also potentially cost-effective for institutions without computer-assisted surgical systems.

Convex–concave and anterior–posterior spinal length discrepancies in adolescent idiopathic scoliosis with major right thoracic curves versus matched controls

PurposeThe apical deformation in adolescent idiopathic scoliosis (AIS) is a combination of rotation, coronal deviation and passive anterior lengthening of the spine. In AIS surgery, posterior–concave lengthening or anterior–convex shortening can be part of the corrective maneuver, as determined by the individual surgeon’s technique. The magnitude of convex–concave and anterior–posterior length discrepancies, and how this needs to be modified to restore optimal spinal harmony, remains unknown.MethodsCT-scans of 80 pre-operative AIS patients with right convex primary thoracic curves were sex- and age-matched to 80 healthy controls. The spinal length parameters of the main thoracic curves were compared to corresponding levels in controls. Vertebral body endplates and posterior elements were semi-automatically segmented to determine the length of the concave and convex side of the anterior column and along the posterior pedicle screw entry points while taking the 3D-orientation of each individual vertebra into account.ResultsThe main thoracic curves showed anterior lengthening with a mean anterior–posterior length discrepancy of + 3 ± 6%, compared to a kyphosis of − 6 ± 3% in controls (p < 0.01). In AIS, the convex side was 20 ± 7% longer than concave (0 ± 1% in controls; p < 0.01). The anterior and posterior concavity were 7 and 22 mm shorter, respectively, while the anterior and posterior convexity were 21 and 8 mm longer compared to the controls.ConclusionsIn thoracic AIS, the concave shortening is more excessive than the convex lengthening. To restore spinal harmony, the posterior concavity should be elongated while allowing for some shortening of the posterior convexity.

Morphometric Study for C1 Pedicle Screw Placement in Thai Patients.

Background Traumatic atlantoaxial (upper cervical spine) leads to instability in weightbearing movement and neurological deficit. Presently, C1 (axial) lateral mass or pedicle screws for fixation are the most popular because of excellent mechanical performance for internal fixation. C1 pedicle screw fixation can reduce intraoperative blood loss and postoperative occipital neuralgia more than C1 lateral mass screws. However, screws cannot be inserted completely through the pedicle in some patients due to C1 size. Objective We aimed to determine the ideal pedicle screw entry point, angle of screw projection, and pedicle height in the Thai population. Methods Patient data were collected and measured using the INFINITT program at Mukdahan Hospital from September 2020 to June 2021. The C1 measurements, i.e., distance from the midline to the medial edge of the posterior arch (DPA) and medial edge transverse foramen (DTF), angle of screw projection, and length and height of the pedicle were recorded. Descriptive statistics and t -test were used to analyze the data. Results The mean Thai pedicle dimensions were DPA = 14.17 mm (range: 11.19-19.70 mm), DTF = 22.09 mm (range: 18.13-26.44 mm), ideal screw entry point = 18.13 mm (range: 15.19-22.00 mm), ideal angle of screw projection medial angulation = 2.67 degrees (range: 0-7 degrees), and height of posterior arch (pedicle) = 4.77 mm (range: 2.68-7.22 mm). Forty of 167 patients (24.0%) had a pedicle height less than 4.0 mm (bilateral 11 patients and unilateral 29 patients). Conclusions The ideal C1 pedicle screw entry point is approximately 18.13 mm from the midline. In the Thai samples with C1 pedicle height less than 4.0 mm, the screws cannot be inserted completely through the pedicle. Therefore, screw insertion should be partially through the pedicle (notching technique).

Application of a new anatomic hook-rod-pedicle screw system in young patients with lumbar spondylolysis: A pilot study.

BACKGROUNDThe pedicle screw-laminar hook system has strong fixation and is conducive to bone graft fusion for lumbar spondylolysis. However, the current pedicle screw-laminar hook fixation system is not specifically designed for lumbar spondylolysis.AIMTo investigate the clinical effects of a new anatomical hook-rod-pedicle screw system in the treatment of lumbar spondylolysis in young adults.METHODSWe designed a new anatomic hook-rod-pedicle screw system for young patients with lumbar spondylolysis. The isthmus and the corresponding pedicle screw entry point were exposed through the intermuscular approach. Autogenous iliac bone graft was obtained to bridge the isthmus defect, and then the anatomic hook-rod-pedicle screw system was used to fix the isthmus in 15 young patients.RESULTSAt 24 mo follow-up, the visual analogue scale score of low back pain decreased from 6.73 ± 0.88 to 0.73 ± 0.59, and the Oswestry disability index score decreased from 58.20 ± 8.99 to 7.87 ± 4.97. Computed tomography showed bilateral isthmic bone healing in 14 cases and unilateral isthmic bone healing in 1 case. Magnetic resonance imaging showed that the lumbar disc signal of diseased segment and adjacent segments had no change compared with that before surgery. The pain visual analogue scale score of the donor site was 0.20 ± 0.41 at the last follow-up. According to the Modified Macnab score, the excellent and good rate was 100%.CONCLUSIONThe application of this new anatomical hook-rod-pedicle screw system to treat young patients with lumbar spondylolysis has the advantages of less trauma, a simple operation and satisfactory clinical effects.

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

Usefulness of Preoperative Planning by Three-Dimensional Planning Software for Pedicle Screw Placement in Thoracolumbar Surgeries: Misplacement Rate and Associated Risk Factors.

Introduction A number of imaging technologies have been developed to reduce the risk of pedicle screw (PS) misplacement. For example, preoperative three-dimensional (3D) planning can reportedly enhance implant placement accuracy in some orthopedic surgeries. However, no study has investigated the effect of preoperative 3D planning on PS placement without intraoperative 3D navigation. Thus, in this study, we aim to examine the accuracy of PS placement and identify the risk factors for PS misplacement in thoracolumbar surgeries performed using preoperative 3D planning software with intraoperative fluoroscopic guidance in a retrospective study. Methods In total, 25 consecutive patients (197 PSs) underwent thoracic or lumbar spinal fusion surgeries using preoperative 3D planning with intraoperative fluoroscopic guidance. PS misplacement was graded based on the degree of perforation (Grade 0, no perforation; Grade 1, <2 mm; Grade 2, 2-4 mm; Grade 3, >4 mm) observed in postoperative computed tomography (CT). Deviations between planned and actual PSs were evaluated by matching preoperative and postoperative CT volume images for each vertebra. Results The overall PS misplacement rate was 6.6% (Grade 1: 4.0%, Grade 2: 1.5%, Grade 3: 1.0%). The median linear deviations of PS entry points between planned and actual locations were determined to be 3.3 mm and 3.3 mm for the horizontal and vertical axes, respectively. The median angular deviations of the PS axis were 6.2° and 4.5° for the transverse and sagittal planes, respectively. Multivariate analysis revealed that horizontal deviation of the PS entry point was the sole factor associated with Grade ≥1 PS misplacement (odds ratio=2.47, p<0.001). Conclusions Preoperative 3D planning software without intraoperative 3D navigation was able to achieve a relatively low PS misplacement ratio among the reported ratio of conventional techniques without navigation. Surgeons should carefully ensure that the entry point is consistent with preoperative planning, especially in the mediolateral direction to avoid misplacement in this method.

Anatomical relationship between the accessory process of the lumbar spine and the pedicle screw entry point.

The vertebra accessory process (or tubercle) of the lumbar spine is an understated landmark which lies caudal to the mammillary process at the base of the transverse process. To our knowledge, no studies compare its relation to pedicle entry point for screw placement. We proposed to evaluate whether a valid and reliable relationship exists between the accessory process and the projected pedicle axis. The distance between the tip of the accessory process and the entry point of the pedicle screw was measured for 50 pedicles. The angle between this axis and the midline was measured. Interrater reliability was assessed intraclass correlation coefficient for two raters. Statistical analysis of the results was performed using SPSS. The mean distance between the tip of accessory process and pedicle screw entry point was 6.58 mm (SD ±2.05), and the mean angle between this axis and the midline was 29.4° medial (SD ±10.08). The ICC for the two raters for the mean distance and the mean angle was 0.974 and 0.894. The calculated mean distance between the tip of the accessory process and pedicle screw entry point was 3.2 mm (SD ±1.3) and 5.7 mm (SD ±1.9) medial and cranial respectively. The accessory process is a consistent and reliable landmark to guide pedicle screw entry point, and compliments other screw insertion techniques. To our knowledge, this is the first study in the published literature to assess this relationship.

CT observation of L5 pedicle screw fixation shielding by the iliac wing width and height

ObjectiveThe height and width of the iliac wing were measured using three-dimensional computed tomography(3D-CT), and the extent to which the iliac wing occluded the entry point of the 5th lumbar vertebra pedicle screw(L5PS) was observed and graded according to severity. The overall goal was to study the influence of the height and width of the iliac wing on L5PS insertion. Patients and methodsThis study included 350 cases (179 males and 171 females) where the L1-S2 region was obtained. We reconstructed 3D-CT in our study for anatomic analysis. The width and height of the iliac wing were measured on CT axial and oblique sagittal images, respectively. The degree of the L5PS entry point was determined by the data of iliac wing width and height, and divided into 0, I, II and III levels. The association between width and height of the iliac wing among males and females was also analyzed in this paper. ResultsThe incidence of shielding of the L5PS entry point by the height and width of the ilium wing were 20.0 % and 19.4 %, respectively. The overall incidence of obstruction of L5PS by the width of the ilium wing was 27.3 % in males and 12.3 % in females. In total, there were 27, 14, and 8 male patients with level I, II, and III shielding, respectively. There were 12, 7, and 2 females with level I, II, and III shielding, respectively. The overall incidence with which the height of the ilium wing obstructed L5PS was 24.0 % in males and 14.6 % in females, of which there were 23 males with level Ⅰ shielding, 16 males with level Ⅱ shielding, 4 males with level Ⅲ shielding, 13 females with level Ⅰ shielding, 8 females with level Ⅱ shielding, and 4 females with level Ⅲ shielding. ConclusionsThe height of the ilium caused obstruction of the L5PS more frequently than the width of the ilium, and males had a higher incidence of iliac wing occlusion than females at both the height and width. The degree of L5PS entry point shielding by the iliac wing width along the horizontal axis was not completely consistent with that of L5PS shielding on the oblique sagittal plane.

Posterior Approach Combined with Thoracic Intervertebral Foramen Posterior Wall Opening and Spinal Reconstruction for Complex Thoracic Intervertebral Foramen Lesions: a Single-Centre Experience

Background: Thoracic intervertebral foramen (TIF) lesions were really difficult to expose through posterior or transforaminal approaches. There was no effective treatment strategy, especially for complex ones. Methods: Between 2013 and 2015, 22 patients presenting with complex TIF lesions underwent posterior approach combined with TIF posterior wall opening and spinal reconstruction were retrospectively reviewed. After ascertaining the precise location of complex TIF lesions, incisions should allow for exposure of the lesion’s adjacent vertebral pedicle screw entry point. The adjacent pair of vertebral lamina and spinous processes is typically removed in a single piece, such that the intra-spinal section can be fully exposed. The posterior wall of the TIF is subsequently opened, allowing the intra-TIF and extra-spinal sections to be sufficiently exposed. Subsequently, spinal reconstruction at the appropriate level is required. When the ventral spinal column is intact, dorsal reconstruction is typically performed using the screw and rod fixation technique (SRFT). After the dorsal surface of the spine has been burnished, the removed vertebral lamina and spinous process are rendered granular to allow reconstruction of the TIF and fusion of adjacent vertebrae. Results: All patients presenting with complex TIF lesions were successfully treated with this approach. No patient had experienced any complications arising from SRFT use. No patient suffered intraspinal infection, incision splits, or CSF leakage in the short-term (between 1 and 3 months) or fixation loosening or spinal instability in the long-term (6–24 months). Imaging studies confirmed that the TIF and spinal reconstruction outcomes were favorable. Conclusion: A posterior approach combined with TIF posterior wall opening and spinal reconstruction is a rapid, effective, and reliable method in the treatment of complex TIF lesions. This technique can provide total lesion resection while reconstructing spinal stability. Keywords: posterior approach; thoracic intervertebral foramen (TIF); intervertebral articular process (IAP); spinal reconstruction; screw and rod fixation technique (SRFT)

Does the Severity of the Curve in Lenke 1 and 2 Adolescent Idiopathic Scoliosis Patients Affect the Distance and Position of the Aorta From Vertebra?

Retrospective study of a prospectively-collected data. To determine whether the severity of the curve magnitude in Lenke 1 and 2 Adolescent Idiopathic Scoliosis (AIS) patients affects the distance and position of the aorta from the vertebra. There were studies that looked into the position of the aorta in scoliotic patients but none of them documented the change in distance of the aorta to the vertebra in relation to the magnitude of the scoliosis. Patients with Lenke 1 and 2 AIS who underwent posterior spinal fusion using pedicle screw construct and had a preoperative computed tomography (CT) scan performed were recruited. The radiological parameters measured on preoperative CT scan were: Aortic-Vertebral Distance (AVD), Entry-Aortic Distance (EAD), Aortic-Vertebral angle (AVA), Pedicle Aorta angle/Aortic Alpha angle (α angle), and Aortic Beta angle (β angle). Thirty-nine patients were recruited. Significant moderate to strong positive correlation was found between AVD and Cobb angle from T8 to T12 vertebrae (r = 0.360 to 0.666). The EAD was generally small in the thoracic region (T4-T10) with mean EAD of less than 30 mm. Among all apical vertebrae, the mean AVD was 5.9 ± 2.2 mm with significant moderate-strong positive correlation to Cobb angle (r = 0.580). The mean α angle was 37.7 ± 8.7° with significant weak positive correlation with Cobb angle (r = 0.325). The larger the scoliotic curve, the aorta was located further away from the apical vertebral wall. The aorta has less risk of injury from the left lateral pedicle screw breach in larger scoliotic curve at the apical region. The distance from the pedicle screw entry point to the wall of the aorta was generally small (less than 30 mm) in the thoracic region (T4-T10). 4.

Spinal Navigation during Orthopedic Residency Training: A Double-Edged Sword?

BackgroundOrthopedic residents in our institute have the opportunity to participate in navigation-assisted spine surgery during their residency training. This paves the way for a new dimension of learning spine surgery, which the previous generation was not exposed to. To study this in detail, we conducted a cross-sectional descriptive survey among our residents to analyse their perception, understanding, and competency regarding pedicle screw application using spinal navigation.MethodsWe selected orthopedic residents (n = 20) who had completed 3 years of training that included at least one rotation (4–6 months) in our spine division. They were asked to respond to a four-part questionnaire that included general and Likert scale-based questions. The first two parts dealt with various parameters regarding spinal navigation and free-hand technique for applying pedicle screws. The third part dealt with residents' opinion regarding the advantages and disadvantages of spinal navigation. The final part was an objective analysis of residents' ability to identify the pedicle screw entry points in selected segments.ResultsWe found that our residents were better trained to apply pedicle screws using spinal navigation. The mean Likert scale score for perception regarding their competency to apply pedicle screws using spinal navigation was 3.65 ± 0.81, compared to only 2.8 ± 0.77 when using the free-hand technique. All residents agreed that spinal navigation is an excellent teaching tool with higher accuracy and greater utility in anatomically critical cases. However, 35% of the residents were not able to identify the entry points correctly in the given segments.ConclusionsAll selected residents were perceived to be competent to apply pedicle screws using spinal navigation. However, some of them were not able to identify the entry points correctly, probably due to overreliance on spinal navigation. Therefore, we encourage residents to concentrate on surface anatomy and tactile feedback rather than completely relying on the navigation display monitor during every screw placement. In addition, incorporating cadaveric and saw bone workshops as a part of teaching program can enhance better understanding of surgical anatomy.

Patient-specific interactive software module for virtual preoperative planning and visualization of pedicle screw entry point and trajectories in spine surgery.

Lumbar pedicle screw insertion involves a steep learning curve for novice spine surgeons and requires image guidance or navigation. Small volume centers may be handicapped by the lack of cost-effective user-friendly tools for preoperative planning, guidance, and decision making. We describe a patient-specific interactive software module, pedicle screw simulator (PSS), for virtual preoperative planning to determine the entry point and visualize the trajectories of pedicle screws. The PSS was coded in Python for use in an open source image processing software, 3D Slicer. Preoperative computed tomography (CT) data of each subject was loaded into this module. The entry-target (ET) mode calculates the ideal angle from the entry point through the widest section of the pedicle to the desired target in the vertebral body. The entry-angle (EA) mode projects the screw trajectory from the desired entry point at a desired angle. The performance of this software was tested using CT data from four subjects. PSS provided a quantitative and qualitative feedback preoperatively to the surgeon about the entry point and trajectories of pedicle screws. It also enabled the surgeons to visualize and predict the pedicle breach with various trajectories. This interactive software module aids in understanding and correcting the orientation of each vertebra in three-dimensions, to identify the ideal entry points, angles of insertion and trajectories for pedicle screw insertion to suit the local anatomy.

Coronal Multiplane Reconstructed Computed Tomography Image Determining Lateral Vertebral Notch-Referred Pedicle Screw Entry Point in Subaxial Cervical Spine: A Preclinical Study.

To evaluate feasibility of computed tomography (CT) coronal multiplane reconstruction image (CMRI) to determine subaxial cervical pedicle screw (PS) entry point and guide lateral vertebral notch (LVN)-referred technique for subaxial cervical PS insertion. Cervical CT scans were performed in 40 volunteers. PS entry point was determined by quantitating PS entry point related to LVN on CMRI. Pedicle mediolateral angle (α) and cephalocaudad angle (β) were also measured to guide the trajectory of PS insertion. Based on these quantitations, 12 human cadaveric subaxial cervical pedicles were inserted with PS referring to LVN. Cortical integrity of each pedicle was evaluated after dissecting the cadaveric vertebrae one by one and confirmed by radiography and CT. The cortical penetration and PS position were classified into 4 grades: 0 (excellent position), I(goodposition), II (fair position), and III (poor position). On CT CMRI, PS entry point was consistently located approximately 2.2 mm medial to LVN from C3 to C7 and approximately 1.4 mm lower to LVN from C3 to C6, but 1.2 mm higher at C7. Bilateral α angle and β angle showed substantial decrease from cranial to caudal. Cortical integrity of PS positions was excellent and good in 88.33%, fair in 8.33%, and poor in 3.33%. CMRI is reliable for determining subaxial cervical PS entry point. LVN is a consistent landmark for the notch-referred technique, which is a practical and easy to master technique for subaxial cervical spine PS insertion.

The segment-dependent changes in lumbar intervertebral space height during flexion-extension motion.

ObjectivesMany studies have investigated the kinematics of the lumbar spine and the morphological features of the lumbar discs. However, the segment-dependent immediate changes of the lumbar intervertebral space height during flexion-extension motion are still unclear. This study examined the changes of intervertebral space height during flexion-extension motion of lumbar specimens.MethodsFirst, we validated the accuracy and repeatability of a custom-made mechanical loading equipment set-up. Eight lumbar specimens underwent CT scanning in flexion, neural, and extension positions by using the equipment set-up. The changes in the disc height and distance between adjacent two pedicle screw entry points (DASEP) of the posterior approach at different lumbar levels (L3/4, L4/5 and L5/S1) were examined on three-dimensional lumbar models, which were reconstructed from the CT images.ResultsAll the vertebral motion segments (L3/4, L4/5 and L5/S1) had greater changes in disc height and DASEP from neutral to flexion than from neutral to extension. The change in anterior disc height gradually increased from upper to lower levels, from neutral to flexion. The changes in anterior and posterior disc heights were similar at the L4/5 level from neutral to extension, but the changes in anterior disc height were significantly greater than those in posterior disc height at the L3/4 and L5/S1 levels, from neutral to extension.ConclusionsThe lumbar motion segment showed level-specific changes in disc height and DASEP. The data may be helpful in understanding the physiologic dynamic characteristics of the lumbar spine and in optimising the parameters of lumbar surgical instruments.Cite this article: M. Fu, Q. Ye, C. Jiang, L. Qian, D. Xu, Y. Wang, P. Sun, J. Ouyang. The segment-dependent changes in lumbar intervertebral space height during flexion-extension motion. Bone Joint Res 2017;6:245–252. DOI: 10.1302/2046-3758.64.BJR-2016-0245.R1.

The accuracy of the lateral vertebral notch-referred pedicle screw insertion technique in subaxial cervical spine: a human cadaver study

This is a cadaver specimen study to confirm new pedicle screw (PS) entry point and trajectory for subaxial cervical PS insertion. To assess the accuracy of the lateral vertebral notch-referred PS insertion technique in subaxial cervical spine in cadaver cervical spine. Reported morphometric landmarks used to guide the surgeon in PS insertion show significant variability. In the previous study, we proposed a new technique (as called "notch-referred" technique) primarily based on coronal multiplane reconstruction images (CMRI) and cortical integrity after PS insertion in cadavers. However, the PS position in cadaveric cervical segment was not confirmed radiologically. Therefore, the difference between the pedicle trajectory and the PS trajectory using the notch-referred technique needs to be illuminated. Twelve cadaveric cervical spines were conducted with PS insertion using the lateral vertebral notch-referred technique. The guideline for entry point and trajectory for each vertebra was established based on the morphometric data from our previous study. After 3.5-mm diameter screw insertion, each vertebra was dissected and inspected for pedicle trajectory by CT scan. The pedicle trajectory and PS trajectory were measured and compared in axial plane. The perforation rate was assessed radiologically and was graded from ideal to unacceptable: Grade 0 = screw in pedicle; Grade I = perforation of pedicle wall less than one-fourth of the screw diameter; Grade II = perforation more than one-fourth of the screw diameter but less than one-second; Grade III = perforation more than one-second outside of the screw diameter. In addition, pedicle width between the acceptable and unacceptable screws was compared. A total of 120 pedicle screws were inserted. The perforation rate of pedicle screws was 78.3% in grade 0 (excellent PS position), 10.0% in grade I (good PS position), 8.3% in grade II (fair PS position), and 3.3% in grade III (poor PS position). The overall accepted accuracy of pedicle screws was 96.7% (Grade 0 + Grade I + Grade II), and only 3.3% had critical breach. There was no statistical difference between the pedicle trajectory and PS trajectory (p > 0.05). Compared to the pedicle width (4.4 ± 0.7mm) in acceptably inserted screw, the unacceptably screw is 3.2 ± 0.3mm which was statistically different (p < 0.05). The accuracy of the notch-referred PS insertion in cadaveric subaxial cervical spine is satisfactory.

Cadaveric study for ideal dorsal pedicle screw entry point.

Objective:To determine the entry for the dorsal pedicular screw in relation to the notch present at the junction of base of the lateral margin of superior articular process with superior border of transverse process in dorsal spine. The advantage of this technique is a constant and easily identifiable entry point which does not involve partial resection of the inferior facet, thus maintaining stability and maintaining the well defined transverse and sagittal screw angles and decreasing the incidence of medial and inferior pedicle violation.Materials and Methods:The study was carried out using ten cadavers (four male and six female). Spinal column was dissected completely from cadavers. Before the experiment, normal anatomy was confirmed on all cadavers excluding cases of spinal deformity. Dissection was done by the spine surgeons taking care to preserve all the bony landmarks near the entry point. This study was carried out bilaterally on pedicles between the first and twelfth thoracic (T) vertebrae.Results:The relation of the superior articular notch and transverse process to the thoracic spine pedicles was studied. It was found that superior third of the pedicle was related to the superior articular notch and the transverse process in the first five thoracic vertebrae. The relation of these structures to the pedicle of the sixth thoracic vertebra was somewhat equally distributed between the superior and middle third of the pedicle. From the 7th to 12th thoracic vertebrae the superior articular process and transverse process were related to the middle third of the pedicle in almost all the cases. It is important to note that the inferior 1/3rd of the pedicle was not related to these landmarks at any of the levels.Conclusion:We conclude that the ideal pedicle entry point described here should be considered by surgeons during thoracic pedicle screw instrumentation. The notch at the base of the superior articular process will always remain constant and therefore an important anatomical landmark in guiding the screw toward the entry of the pedicle.

Feasibility Study of Free-Hand Technique for Pedicle Screw Insertion at C7 without Fluoroscopy-Guidance.

Study DesignRetrospective interventional study.PurposeTo introduce a free-hand pedicle screw (PS) insertion technique without fluoroscopic guidance in the C7 vertebra and evaluate the procedure's feasibility and radiologic outcomes.Overview of LiteratureAlthough PS insertion at C7 has been recognized as a critical procedure in posterior cervical fusion surgery, conventional techniques for C7 PS have several limitations.MethodsThirty two patients (64 screws) who underwent PS insertion in C7 with the novel technique were included in this study. Postoperative clinical and radiological outcomes were evaluated. Special attention was paid to the presence of any problems in the screw position including cortical breaches of the PS and encroachment of the PS into the spinal canal or the vertebral foramen. This novel technique for PS insertion in C7 without fluoroscopy guidance had three key elements. First, the ideal PS entry point was chosen near the C6–7 facet joint using preoperative images. Second, the convergent angle distance was measured at axial computed tomography (CT) imaging, which defined the distance between the tip of C7 spinous process and the extended line passing through the pedicle axis from the ideal entry point. Third, the cranial-caudal angle distance was measured in sagittal CT images, which defined the distance between the tip of the C7 spinous process and the extended line passing through the pedicle axis.ResultsCortical breach on postoperative CT images was observed in three screws. All violated only the lateral wall of the affected pedicle. The breached screws occurred in the initial five cases. Postoperative neurologic deterioration was not observed in any patient, regardless of cortical breaching.ConclusionsThe novel technique successfully allows for C7 PS to be placed and is associated with a low rate of cortical breach.