scholarly journals CT-based morphometric analysis of the occipital condyle: focus on occipital condyle screw insertion

2016 ◽  
Vol 25 (5) ◽  
pp. 572-579 ◽  
Author(s):  
Jinsong Zhou ◽  
Alejandro A. Espinoza Orías ◽  
Xia Kang ◽  
Jade He ◽  
Zhihai Zhang ◽  
...  
Keyword(s):  
Morphometric Analysis ◽  
Sagittal Plane ◽  
Simulation Method ◽  
Entry Point ◽  
Screw Placement ◽  
Occipital Condyle ◽  
Hypoglossal Canal ◽  
Screw Length ◽  
Preoperative Simulation ◽  
The Mean

OBJECTIVE The segmental occipital condyle screw (OCS) is an alternative fixation technique in occipitocervical fusion. A thorough morphological study of the occipital condyle (OC) is critical for OCS placement. The authors set out to introduce a more precise CT-based method for morphometric analysis of the OC as it pertains to the placement of the segmental OCS, and they describe a novel preoperative simulation method for screw placement. Two new clinically relevant parameters, the height available for the OCS and the warning depth, are proposed. METHODS CT data sets from 27 fresh-frozen human cadaveric occipitocervical spines were used. All measurements were performed using a commercially available 3D reconstruction software package. The length, width, and sagittal angle of the condyle were measured in the axial plane at the base of the OC. The height of the OC and the height available for the segmental OCS were measured in the reconstructed oblique sagittal plane, fitting the ideal trajectory of the OCS recommended in the literature. The placement of a 3.5-mm-diameter screw that had the longest length of bicortical purchase was simulated into the OC in the oblique sagittal plane, with the screw path not being blocked by the occiput and not violating the hypoglossal canal cranially or the atlantooccipital joint caudally. The length of the simulated screw was recorded. The warning depth was measured as the shortest distance from the entry point of the screw to the posterior border of the hypoglossal canal. RESULTS The mean length and width of the OC were found to be larger in males: 22.2 ± 1.7 mm and 12.1 ± 1.0 mm, respectively, overall (p < 0.0001 for both). The mean sagittal angle was 28.0° ± 4.9°. The height available for the OCS was significantly less than the height of the OC (6.2 ± 1.3 mm vs 9.4 ± 1.5 mm, p < 0.0001). The mean screw length (19.3 ± 1.9 mm) also presented significant sex-related differences: male greater than female (p = 0.0002). The mean warning depth was 7.5 ± 1.7 mm. In 7.4% of the samples, although the height of the OC was viable, the height available for the OCS was less than 4.5 mm, thus making screw placement impractical. For these cases, a new preoperative simulation method of the OCS placement was proposed. In 92.6% of the samples that could accommodate a 3.5-mm-diameter screw, 24.0% showed that the entry point of the simulated screw was covered by a small part of the C-1 posterosuperior joint rim. CONCLUSIONS The placement of the segmental OCS is feasible in most cases, but a thorough preoperative radiological analysis is essential and cannot be understated. The height available for the OCS is a more clinically relevant and precise parameter than the height of the OC to enable proper screw placement. The warning depth may be helpful for the placement of the OCS.

scholarly journals Radiographic parameters and a novel fluoroscopic control view for posterior screw fixation of coracoid base fractures

SICOT-J ◽  
2020 ◽  
Vol 6 ◽  
pp. 9
Author(s):  
Hatem Galal Said ◽  
Tarek Nabil Fetih ◽  
Hosam Elsayed Abd-Elzaher ◽  
Simon Martin Lambert
Keyword(s):  
Sagittal Plane ◽  
Coracoid Process ◽  
Entry Point ◽  
Coronal Plane ◽  
Screw Placement ◽  
Posterior Fixation ◽  
Screw Insertion ◽  
Screw Length ◽  
Scapular Spine ◽  
The Mean

Introduction: Coracoid fractures have the potential to lead to inadequate shoulder function. Most coracoid base fractures occur with scapular fractures and the posterior approaches would be utilized for surgical treatment. We investigated the possibility of fixing the coracoid through the same approach without an additional anterior approach. Materials and methods: Multi-slice CT scans of 30 shoulders were examined and the following measurements were performed by an independent specialized radiologist: posterior coracoid screw entry point measured form infraglenoid tubercle, screw trajectory in coronal plane in relation to scapular spine and lateral scapular border, screw trajectory in sagittal plane in relation to glenoid face bisector line and screw length. We used the results from the CT study to guide postero-anterior coracoid screw insertion under fluoroscopic guidance on two fresh frozen cadaveric specimens to assess the reproducibility of accurate screw placement based on these parameters. We also developed a novel fluoroscopic projection, the anteroposterior (AP) coracoid view, to guide screw placement in the para-coronal plane. Results: The mean distance between entry point and the infraglenoid tubercle was 10.8 mm (range: 9.2–13.9, SD 1.36). The mean screw length was 52 mm (range: 46.7–58.5, SD 3.3). The mean sagittal inclination angle between was 44.7 degrees (range: 25–59, SD 5.8). The mean angle between screw line and lateral scapular border was 47.9 degrees (range: 34–58, SD 4.3). The mean angle between screw line and scapular spine was 86.2 degrees (range: 75–95, SD 4.9). It was easy to reproduce the screw trajectory in the para-coronal plane; however, multiple attempts were needed to reach the correct angle in the parasagittal plane, requiring several C-arm corrections. Conclusion: This study facilitates posterior fixation of coracoid process fractures and will inform the “virtual visualization” of coracoid process orientation.

scholarly journals Morphometric Evaluation of Occipital Condyles: Defining Optimal Trajectories and Safe Screw Lengths for Occipital Condyle-Based Occipitocervical Fixation in Indian Population

2018 ◽  
Vol 12 (2) ◽  
pp. 214-223 ◽  
Author(s):  
Aju Bosco ◽  
Prakash Venugopal ◽  
Ajoy Prasad Shetty ◽  
Rajasekaran Shanmuganathan ◽  
Rishi Mugesh Kanna
Keyword(s):  
Vertebral Artery ◽  
Morphometric Analysis ◽  
Three Dimensional ◽  
Vascular Anatomy ◽  
Application Rate ◽  
Screw Placement ◽  
Occipital Condyle ◽  
Screw Insertion ◽  
Occipitocervical Fixation ◽  
Screw Length

<sec><title>Study Design</title><p>Computed tomographic (CT) morphometric analysis.</p></sec><sec><title>Purpose</title><p>To assess the feasibility and safety of occipital condyle (OC)-based occipitocervical fixation (OCF) in Indians and to define anatomical zones and screw lengths for safe screw placement.</p></sec><sec><title>Overview of Literature</title><p>Limitations of occipital squama-based OCF has led to development of two novel OC-based OCF techniques.</p></sec><sec><title>Methods</title><p>Morphometric analysis was performed on the OCs of 70 Indian adults. The feasibility of placing a 3.5-mm-diameter screw into OCs was investigated. Safe trajectories and screw lengths for OC screws and C0–C1 transarticular screws without hypoglossal canal or atlantooccipital joint compromise were estimated.</p></sec><sec><title>Results</title><p>The average screw length and safe sagittal and medial angulations for OC screws were 19.9±2.3 mm, ≤6.4°±2.4° cranially, and 31.1°±3° medially, respectively. An OC screw could not be accommodated by 27% of the population. The safe sagittal angles and screw lengths for C0–C1 transarticular screw insertion (48.9°±5.7° cranial, 26.7±2.9 mm for junctional entry technique; 36.7°±4.6° cranial, 31.6±2.7 mm for caudal C1 arch entry technique, respectively) were significantly different than those in other populations. The risk of vertebral artery injury was high for the caudal C1 arch entry technique. Screw placement was uncertain in 48% of Indians due to the presence of aberrant anatomy.</p></sec><sec><title>Conclusions</title><p>There were significant differences in the metrics of OC-based OCF between Indian and other populations. Because of the smaller occipital squama dimensions in Indians, OC-based OCF techniques may have a higher application rate and could be a viable alternative/salvage option in selected cases. Preoperative CT, including three-dimensional-CT-angiography (to delineate vertebral artery course), is imperative to avoid complications resulting from aberrant bony and vascular anatomy. Our data can serve as a valuable reference guide in placing these screws safely under fluoroscopic guidance.</p></sec>

scholarly journals The Feasibility of Anterior Occipital Condyle Screw for the Reconstruction of Craniovertebral Junction: A Digital Anatomical and Cadaveric Study of a Novel Technique

2020 ◽  
Author(s):  
Dingli Xu ◽  
Haijiao Mao ◽  
Yang Wang ◽  
Kaifeng Gan ◽  
Weihu Ma
Keyword(s):  
Sagittal Plane ◽  
Three Dimensional ◽  
Craniovertebral Junction ◽  
Entry Point ◽  
Ct Scans ◽  
Occipital Condyle ◽  
Novel Technique ◽  
Screw Length ◽  
Mesh Cage ◽  
Technique Apply

Abstract Background: Anterior occipital condyle screw (AOCS) could be a feasible technique apply to the reconstruction of craniovertebral junction. This study was to analyze the feasibility of AOCS.Method: The craniovertebral junction computed tomography (CT) scans of 40 adults were enrolled and imported into Mimics software. Then the three-dimensional reconstruction digital model of craniovertebral junction were established to determine entry point, insertion angle and screw’s trajectory. After AOCS inserted into ten human cadaver spine specimens, CT scans were performed to verify the location between screws and important structures. Result: The optimal entry point is located caudally and medial to the ventral of occipital condyle. The optimal trajectory is in inclination angle (5.9°±3.4°) in the sagittal plane and diverge angle (26.7°±6.0°) in the axial plane with the screw length around 21.6±1.2mm. There were no screws invaded into hypoglossal canal and vertebral artery in all specimens.Conclusion: AOCS fixation is a feasible novel technique for anterior craniovertebral junction reconstruction, and it could be an effective alternative operation for anterior reconstruction with titanium mesh cage.

Computed tomography morphometric analysis for C-1 lateral mass screw placement in children

2009 ◽  
Vol 3 (1) ◽  
pp. 20-23 ◽  
Author(s):  
Roukoz B. Chamoun ◽  
William E. Whitehead ◽  
Daniel J. Curry ◽  
Thomas G. Luerssen ◽  
Andrew Jea
Keyword(s):  
Morphometric Analysis ◽  
Entry Point ◽  
Posterior Arch ◽  
Lateral Mass ◽  
Confined Space ◽  
Lateral Mass Screw ◽  
Screw Length ◽  
Entry Points ◽  
Left And Right ◽  
The Mean

Object The use of C-1 lateral mass screws provides an alternative to C1–2 transarticular screws in the pediatric population. However, the confined space of the local anatomy and unfamiliarity with the technique may make the placement of a C-1 lateral mass screw more challenging, especially in the juvenile or growing spine. Methods A CT morphometric analysis was performed in 76 pediatric atlases imaged at Texas Children's Hospital from October 1, 2007 until April 30, 2008. Critical measurements were determined for potential screw entry points, trajectories, and lengths, with the goal of replicating the operative technique described by Harms and Melcher for adult patients. Results The mean height and width for screw entry on the posterior surface of the lateral mass were 2.6 and 8.5 mm, respectively. The mean medially angled screw trajectory from an idealized entry point on the lateral mass was 16° (range 4 to 27°). The mean maximal screw depth from this same ideal entry point was 20.3 mm. The overhang of the posterior arch averaged 6.3 mm (range 2.1–12.4 mm). The measurement between the left- and right-side lateral masses was significantly different for the maximum medially angled screw trajectory (p = 0.003) and the maximum inferiorly directed angle (p = 0.045). Those measurements in children < 8 years of age were statistically significant for the entry point height (p = 0.038) and maximum laterally angled screw trajectory (p = 0.025) compared with older children. The differences between boys and girls were statistically significant for the minimum screw length (p = 0.04) and the anterior lateral mass height (p < 0.001). Conclusions A significant variation in the morphological features of C-1 exists, especially between the left and right sides and in younger children. The differences between boys and girls are clinically insignificant. The critical measurement of whether the C-1 lateral mass in a child could accommodate a 3.5-mm-diameter screw is the width of the lateral mass and its proximity to the vertebral artery. Only 1 of 152 lateral masses studied would not have been able to accommodate a lateral mass screw. This study reemphasizes the importance of a preoperative CT scan of the upper cervical spine to assure safe and effective placement of the instrumentation at this level.

scholarly journals CT-scan based anatomical study as a guidance for infra-acetabular screw placement

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Quanyi Lu ◽  
Runtao Zhou ◽  
Shichang Gao ◽  
Anlin Liang ◽  
Mingming Yang ◽  
...  
Keyword(s):  
Sagittal Plane ◽  
Three Dimensional ◽  
Anatomical Study ◽  
Ischial Tuberosity ◽  
Entry Point ◽  
Screw Placement ◽  
Minimum Thickness ◽  
Males And Females ◽  
The Relationship ◽  
Screw Group

Abstract Background The infra-acetabular corridor is quite narrow, which makes a challenge for the orthopedists to insert the screw. This study aimed to explore the relationship between the infra-acetabular corridor diameter (IACD) and the minimum thickness of medial acetabular wall (MTMAW), and to clarify the way of screw placement. Methods The Computed tomography (CT) data of 100 normal adult pelvises (50 males and 50 females respectively) were collected and pelvis three-dimensional (3D) reconstruction was performed by using Mimics software and the 3D model was imported into Geomagic Studio software. The perspective of acetabulum was carried out orienting from iliopubic eminence to ischial tuberosity and the IACD was measured by placing virtual screws which was vertical to the corridor transverse section of “teardrop”. The relationship between IACD and MTMAW was analyzed. When IACD was ≥5 mm, 3.5 mm all-in screws were placed. When IACD was < 5 mm, 3.5 mm in-out-in screws were placed. Results The IACD of males and females were (6.15 ± 1.24) mm and (5.42 ± 1.01) mm and the MTMAW in males and females were (4.40 ± 1.23) mm and (3.60 ± 0.81) mm respectively. The IACD and MTMAW in males were significantly wider than those of females (P < 0.05), and IACD was positively correlated with MTMAW (r = 0.859), the regression equation was IACD = 2.111 + 0.917 MTMAW. In the all-in screw group, 38 cases (76%) were males and 33 cases (66%) were females respectively. The entry point was located at posteromedial of the apex of iliopubic eminence, and the posterior distance and medial distance were (8.03 ± 2.01) mm and (8.49 ± 2.68) mm respectively in males. As for females, those were (8.68 ± 2.35) mm and (8.87 ± 2.79) mm respectively. In the in-out-in screw group, 12 cases (24%) were males and 17 cases (34%) were females, respectively. The posterior distance and medial distance between the entry point and the apex of iliopubic eminence were (10.49 ± 2.58) mm and (6.17 ± 1.84) mm respectively in males. As for females, those were (10.10 ± 2.63) mm and (6.63 ± 1.49) mm respectively. The angle between the infra-acetabular screw and the sagittal plane was medial inclination (0.42 ± 6.49) °in males, lateral inclination (8.09 ± 6.33) °in females, and the angle between the infra-acetabular screw and the coronal plane was posterior inclination (54.06 ± 7.37) °. Conclusions The placement mode of the infra-acetabular screw (IAS) can be determined preoperatively by measuring the MTMAW in the CT axial layers. Compared with all-in screw, the in-out-in screw entry point was around 2 mm outwards and backwards, and closer to true pelvic rim.

scholarly journals REPRODUCIBILITY OF S2-ALAR ILIAC SCREW MORPHOMETRIC ANALYSIS

2021 ◽  
Vol 29 (2) ◽  
pp. 97-100
Author(s):  
MARIANA DEMÉTRIO DE SOUSA PONTES ◽  
LUCAS AMÉRICO FRANCISCO ◽  
LUCAS KLAROSK ISMAEL ◽  
CARLOS FERNANDO PEREIRA DA SILVA HERRERO
Keyword(s):  
Morphometric Analysis ◽  
Sagittal Plane ◽  
Interobserver Reliability ◽  
Statistical Significance ◽  
Intraclass Correlation ◽  
Intraobserver Reliability ◽  
Axial Plane ◽  
Level Of Evidence ◽  
Screw Length ◽  
Trajectory Angle

ABSTRACT Objective: To evaluate the reproducibility of a S2-alar iliac (S2AI) screw parameters measurement method by inter and intraobserver reliability. Methods: Cross-sectional study, considering computed tomography exams. Morphometric analysis was performed by multiplanar reconstructions. Screw length, diameter and trajectory angles were the studied variables. To analyze the measurements reproducibility, intraclass correlation coefficient (ICC) was used. Results: Interobserver reliability was classified as strong for screw shortest length (ICC: 0.742) and diameter (ICC: 0.699). Interobserver reliability was classified as moderate for screw longest length (ICC: 0.553) and for screw trajectory angles in the axial plane for the longest (ICC: 0.478) and for the shortest lengths (ICC: 0.591). Intraobserver reliability was interpreted as excellent for screw shortest (ICC: 0.932) and longest lengths (ICC: 0.962) and diameter (ICC: 0.770) and screw trajectory angles in the axial plane for the screw longest (ICC: 0.773) and shortest lengths (ICC: 0.862). There were weak interobserver and strong intraobserver reliabilities for trajectory angle in sagittal plane, but no statistical significance was found. Conclusion: Inter and intraobserver reliability of S2AI screw morphometric parameters were interpreted from moderate to excellent in almost all studied variables, except for the screw trajectory angle in the sagittal plane measurement. Level of Evidence IV, Diagnostic Studies - Investigating a Diagnostic Test.

scholarly journals 205 Pediatric Occipital Condyle Morphometric Analysis Using Computed Tomography With Evaluation for Occipital Condyle Screw Placement

Neurosurgery ◽  
2018 ◽  
Vol 65 (CN_suppl_1) ◽  
pp. 117-117
Author(s):  
Khoi D Nguyen ◽  
Angela Viers ◽  
Jonathan A Tuttle ◽  
Ian M Heger
Keyword(s):  
Computed Tomography ◽  
Morphometric Analysis ◽  
Screw Placement ◽  
Occipital Condyle

scholarly journals Does robot-assisted navigation influence pedicle screw selection and accuracy in minimally invasive spine surgery?

2022 ◽  
Vol 52 (1) ◽  
pp. E4
Keyword(s):  
Minimally Invasive ◽  
Pedicle Screw ◽  
Surgical Navigation ◽  
Lumbar Fusion ◽  
Pedicle Screws ◽  
Screw Placement ◽  
Robotic Assistance ◽  
Pedicle Screw Placement ◽  
Screw Length ◽  
The Mean

OBJECTIVE The accuracy of percutaneous pedicle screw placement has increased with the advent of robotic and surgical navigation technologies. However, the effect of robotic intraoperative screw size and trajectory templating remains unclear. The purpose of this study was to compare pedicle screw sizes and accuracy of placement using robotic navigation (RN) versus skin-based intraoperative navigation (ION) alone in minimally invasive lumbar fusion procedures. METHODS A retrospective cohort study was conducted using a single-institution registry of spine procedures performed over a 4-year period. Patients who underwent 1- or 2-level primary or revision minimally invasive surgery (MIS)–transforaminal lumbar interbody fusion (TLIF) with pedicle screw placement, via either robotic assistance or surgical navigation alone, were included. Demographic, surgical, and radiographic data were collected. Pedicle screw type, quantity, length, diameter, and the presence of endplate breach or facet joint violation were assessed. Statistical analysis using the Student t-test and chi-square test was performed to evaluate the differences in pedicle screw sizes and the accuracy of placement between both groups. RESULTS Overall, 222 patients were included, of whom 92 underwent RN and 130 underwent ION MIS-TLIF. A total of 403 and 534 pedicle screws were placed with RN and ION, respectively. The mean screw diameters were 7.25 ± 0.81 mm and 6.72 ± 0.49 mm (p < 0.001) for the RN and ION groups, respectively. The mean screw length was 48.4 ± 4.48 mm in the RN group and 45.6 ± 3.46 mm in the ION group (p < 0.001). The rates of “ideal” pedicle screws in the RN and ION groups were comparable at 88.5% and 88.4% (p = 0.969), respectively. The overall screw placement was also similar. The RN cohort had 63.7% screws rated as good and 31.4% as acceptable, while 66.1% of ION-placed screws had good placement and 28.7% had acceptable placement (p = 0.661 and p = 0.595, respectively). There was a significant reduction in high-grade breaches in the RN group (0%, n = 0) compared with the ION group (1.2%, n = 17, p = 0.05). CONCLUSIONS The results of this study suggest that robotic assistance allows for placement of screws with greater screw diameter and length compared with surgical navigation alone, although with similarly high accuracy. These findings have implied that robotic platforms may allow for safe placement of the “optimal screw,” maximizing construct stability and, thus, the ability to obtain a successful fusion.

scholarly journals The posterior superior iliac spine and sacral laminar slope: key anatomical landmarks for freehand S2-alar-iliac screw placement

2018 ◽  
Vol 29 (4) ◽  
pp. 429-434 ◽  
Author(s):  
James D. Lin ◽  
Lee A. Tan ◽  
Chao Wei ◽  
Jamal N. Shillingford ◽  
Joseph L. Laratta ◽  
...  
Keyword(s):  
Spinal Deformity ◽  
3D Visualization ◽  
Screw Placement ◽  
Anatomical Landmarks ◽  
Posterior Superior Iliac Spine ◽  
Unaffected Side ◽  
Sciatic Notch ◽  
Starting Point ◽  
Screw Length ◽  
The Mean

OBJECTIVEThe S2-alar-iliac (S2AI) screw is an increasingly popular method for spinopelvic fixation. The technique of freehand S2AI screw placement has been recently described. The purpose of this study was to demonstrate, through a CT imaging study of patients with spinal deformity, that screw trajectories based on the posterior superior iliac spine (PSIS) and sacral laminar slope result in reliable freehand S2AI trajectories that traverse safely above the sciatic notch.METHODSFifty consecutive patients (age ≥ 18 years) who underwent primary spinal deformity surgery were included in the study. Simulated S2AI screw trajectories were analyzed with 3D visualization software. The cephalocaudal coordinate for the starting point was 15 mm cephalad to the PSIS. The mediolateral coordinate for the starting point was in line with the lateral border of the dorsal foramina. The cephalocaudal screw trajectory was perpendicular to the sacral laminar slope. Screw trajectories, lengths, and distance above the sciatic notch were measured.RESULTSThe mean sagittal screw angle (cephalocaudal angulation) was 44.0° ± 8.4° and the mean transverse angle (mediolateral angulation) was 37.3° ± 4.3°. The mean starting point was 5.9 ± 5.8 mm distal to the caudal border of the S1 foramen. The mean screw length was 99.9 ± 18.6 mm. Screw trajectories were on average 8.5 ± 4.3 mm above the sciatic notch. A total of 97 of 100 screws were placed above the sciatic notch. In patients with transitional lumbosacral anatomy, the starting point on the lumbarized/sacralized side was 3.4 mm higher than on the contralateral unaffected side.CONCLUSIONSThe PSIS and sacral laminar slope are two important anatomical landmarks for freehand S2AI screw placement.

scholarly journals Morphometric evaluation of occipital condyles for a safe transcondylar approach through skull base

2018 ◽  
Vol 7 (02) ◽  
pp. 078-084
Author(s):  
Vijisha Phalgunan ◽  
Suresh Narayanan
Keyword(s):  
Skull Base ◽  
Posterior Margin ◽  
Occipital Condyle ◽  
Hypoglossal Canal ◽  
Transcondylar Approach ◽  
South Indian ◽  
Important Landmark ◽  
The Mean ◽  
Occipital Condyles ◽  
Morphometric Evaluation

Abstract Aims and Objectives: Occipital condyle is an important landmark in transcondylar approach for surgery of lesions ventral to the brainstem, hence it is imperative to understand the anatomical aspects of occipital condyle. The aim of the present study is to analyse the morphometrical aspects of occipital condyle and to highlight its importance in surgical resection. Materials and method: Hundred occipital condyles of fifty dry skulls were used for this study. Twenty-six parameters were measured. The measurements were made separately for right and left sides. Results: The mean length of occipital condyle was found to be 22.92mm. The distance between the intracranial orifice of the hypoglossal canal and the posterior margin of occipital condyle was 12.55±0.05mm. The commonest location of intracranial orifice and extracranial orifice of hypoglossal canal was found to be at location 3 and location 2 respectively. Occipital condyle was oval in most skulls. Conclusion: Occipital condyle can be safely drilled for a distance of 12 mm from the posterior margin before encountering the hypoglossal canal. Surgeons operating in this area must consider the variations of parameters of south Indian skulls.

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