Lateral Mass Of Atlas Research Articles

Morphometric analysis of atlas lateral mass in Down syndrome cases with relevance to surgical intervention.

Surgical stabilization of the Atlas vertebrae is indicated for severe atlantoaxial instability (AAI) in patients with Down syndrome (DS). This study aims to evaluate the morphological characteristics of the Atlas lateral mass (ALM) in patients with DS with regard to safe instrumentation for surgical stabilization and to compare them with non-syndromic group. This multicenter, retrospective, case-control study included age- and sex-matched patients with and without DS aged > 7 years with a cervical computed tomography (CT) scan. After three-dimensional CT reconstruction, nine parameters were evaluated for both groups. All included measurements were performed by a neuroradiologist who was blinded to clinical data. Forty-three of 3,275 patients with DS were included in this study. Matching number of consecutive patients without DS were identified (mean age: 16 years). Patients with DS were significantly shorter than those without DS. Seven of nine parameters related to ALM were significantly lower in patients with DS than in those in the control group, including anterior wall height (AH), posterior wall height (PH), their ratio, and arch-ALM angle. On adjusting data for patient height, patients with DS had a smaller PH, lower PH/AH ratio, and steeper arch-ALM angle than the control group. Patients with DS had a smaller posterior ALM wall and a steeper arch-ALM angle than the control group without DS. This information is important for surgical planning of safe posterior ALM exposure and safe instrumentation for surgical stabilization in patients with DS.

The New Alternative Technique Outcomes: Atlas Lateral Mass Screw and C2-3 Transfacet Screw Fixation for Complex Atlantoaxial Instability in Patients with Thin C2 Pedicle or High-Riding Vertebral Artery

The study aimed to evaluate the safety, feasibility, effect on fusion, and clinical efficacy of atlas lateral mass and C2-3 transfacet screw fixation technique, serves as an alternative method to traditional posterior atlantoaxial fixation. Patients with atlantoaxial instability who underwent atlas lateral mass and C2-3 transfacet fixation surgery were included. The duration of the surgery and the quantity of blood lost during the operation were recorded. Patients were monitored via X-ray and computed tomography scans to evaluate the degree of fusion at the 1-month and 12-month follow-up. The Neck Visual Analog Scale and Neck Disability Index were evaluated preoperatively, in the postoperative first week, and at the 12-month follow-up for clinical follow-up. A total of 8 patients with atlantoaxial instability due to odontoid fracture or Arnold- Chiari malformation accompanied by bony or vascular abnormalities were included in the study between 2017 and 2024. All 8 patients underwent successful atlas lateral mass and C2-3 transfacet screw fixation, with no neurovascular injury noted during surgery. All patients with fracture exhibited fusion at the 12-month mark, and both the Neck Visual Analog Scale and Neck Disability Index scores demonstrated significant improvement at both the 1-week and 12-month postoperative periods (P < 0.05). The atlas lateral mass and C2-3 transfacet screw fixation technique, an alternative to conventional posterior fixation, has been demonstrated to be an efficacious method for providing adequate stabilization and fusion in patients with atlantoaxial instability, even in the cases of thin C2 pedicle, high-riding vertebral artery, previous failed surgeries, or reoperation.

Strategies to avoid internal carotid artery injury in "sandwich" atlantoaxial dislocation patients during surgery.

To elucidate the anatomic relationship between the internal carotid artery (ICA) and the bony structures of the craniovertebral junction among "sandwich" atlantoaxial dislocation (AAD) patients, and to analyze the risks of injury during surgical procedures. The distance from the medial wall of ICA to the midsagittal plane (D1), the shortest distance between the ICA wall and the anterior cortex of the lateral mass of atlas (LMA) (D2) on the most caudal and cranial levels of LMA and the angle (A) between the sagittal plane passing through the screw entry point of C1 lateral mass(C1LM) screw and the medial tangent line of the vessel passing through the entry point were measured. Besides, the location of ICA in front of the atlantoaxial vertebra was divided into 4 categories (Z1-Z4). There was a statistically difference between the male and female patients regarding D1, and the difference between D2 at level a and level b as well as angle A between the left and right sides were statistically different (p < 0.05). Ninety-two ICAs (57.5%) were anteriorly located in Z3, 50 (31.3%) were located in Z4, 17 were located in Z2, and only one ICA was located in Z1 in all 80 patients. In "sandwich" AAD patients, particular attention should be paid to excessively medialized ICA to avoid ICA injury during trans-oral procedures, and the risk of injuring the ICA with more cranially and medially angulated C1LM screw placement was relatively less during posterior fixation procedures. A novel classification of ICA location was used to describe the relationship between ICA and LMA.

Atlas (C1) lateral mass screw placement using the intersection between lateral mass and inferomedial edge of the posterior arch: a cadaveric study.

To compare the Atlas (C1) lateral mass screw placement between screw trajectories of 0° and 15° medial angulation while using the intersection between lateral mass and inferomedial edge of the posterior arch. Forty-eight Atlas lateral masses were prepared and divided into 2 groups: Group 1; screws inserted at 3mm lateral to the reference point with screw trajectory of 0° angulation(N = 24) and Group 2; those inserted with screw trajectory of 15° medial angulation(N = 24). We evaluated the atlas anatomy, screw purchase and the presence of any breaches using CT scan. The radiographic parameters for Groups 1 and 2 were found statistically different (p-value < 0.05): bilateral intraosseous screw lengths (17.92 ± 1.47mm. vs. 20.71 ± 2.4mm.), bilateral screw length (29.92 ± 1.72mm. vs. 33.13 ± 1.78mm.), left screw medial angulation (x°) (0.67° ± 0.78° vs.14.17° ± 3.51°), right screw medial angulation (y°) (0.83° ± 1.03° vs.14.25° ± 2.53°) and bilateral screw medial angulation (0.75° ± 0.9° vs. 14.21° ± 2.99°). Twenty-two screws (91.67%) using the 0° medial angulation and nineteen screws (79.17%) using the 15° medial angulation had no cortical violations (Grade 0). However, two screws (8.33%) with 0° medial angulation and five screws (20.83%) with 15° medial angulation had breach less than 2mm (Grade 1). There were no screws with breach between 2 and 4mm (Grade 2) or greater than 4mm. (Grade 3). A starting point of 3-mm lateral to the intersection between lateral mass and inferomedial edge of the Atlas posterior arch can be safely and effectively used to insert C1 lateral mass using both 0° and 15° medial angulation.

Suitability of 3.5-mm screw for the atlas in children: a retrospective computed tomography analysis.

The growth and development of the atlas in children has not been studied to date using a large sample size. To study whether a 3.5-mm screw is suitable for the atlas in children, to explore the anatomical size and development of the atlas in 0-14-year-old children, and to provide morphological basis for lateral mass screw internal fixation. A Computed Tomography (CT) morphometric analysis was performed on 420 pediatric atlases. In the atlas, D1, D2, D3, D4, and α of the atlas lateral mass were measured. Statistical analysis was performed using one-way ANOVA and Students' t test. The least square method was used for the regression analysis of the change trend in anatomical structure. The curve with the greatest goodness of fit was used as the anatomic trend regression curve. D1, D2, D3, and D4 generally showed an increasing trend with age. The ranges of averages of D1, D2, D3, D4, and α in 0-14year-old children were as follows: 4.576-9.202mm, 9.560-25.100mm, 3.414-10.554mm, 11.150-27.895, and 12.41°-20.97°, respectively. The trends of the fitting curves of L1 and L3 were power functions, and those of L2 and L4 were logarithmic curves. CT examination could help in preoperative decision-making, and 3.5-mm screw was found to be suitable for lateral mass screw internal fixation in children aging 2years and older. D1-D4 increased with age. This provided a certain reference to perform posterior atlantoaxial fusion in children and is of great significance to design posterior atlantoaxial screw in children.

The Intersection Between Lateral Mass and Inferomedial Edge of the C1 Posterior Arch: A Reference Point for C1 Lateral Mass Screw Insertion

ObjectiveTo determine the ideal Atlas (C1) lateral mass screw placement and trajectory using the intersection between the lateral mass and inferomedial edge of the posterior arch as an easily identifiable and reproducible medial reference point. Selection of an ideal entry point and trajectory of C1 lateral mass screw insertion can help to minimize neurovascular injuries. While various techniques for screw insertion have been proposed in the past, they all require extensive dissection of the C1 lateral mass, which can cause profuse bleeding. MethodsNinety-three 3-dimensional computed tomography reconstructed images of C1 lateral masses in adult patients were utilized to simulate the placement of C1 lateral mass screws via 4 entry points and 2 trajectory angles referencing off of a medial reference point using Vero’s VISI 17 software. The safety during screw insertion simulation, as well as the screw length, were evaluated. ResultsWe found that C1 lateral mass screws could be safely placed bilaterally at 3 mm lateral to the reference point in both 0° and 15° medial screw angulation without violation of the cortex. The 15° medial angulation allowed for longer (18 mm) screws than the 0° angulation. ConclusionWe recommend starting C1 lateral mass screws 3 mm lateral to the intersection between the lateral mass and inferomedial edge of the posterior arch at a 15° medial angulation.

Morphometric measurements of safety zones and orientation angles for freehand placement of revision screws in atlas lateral mass.

To demonstrate the possibility of revision screw placement to the atlas, as well as define the safety zones and orientation angles. This retrospective study analysed the records of four patients who were operated for AAI earlier. Because they needed revision of Atlas screws, they were re-operated after obtaining the measurements mentioned in this study. In addition, measurements of 50 healthy subjects were included in the study as the control group. Maximum screw lengths were also measured. Safe zone in the ideal sagittal direction were wider. As the screw projection becomes more cephalic direction in the sagittal plane, the safe zone for the screw becomes narrower. With the sagittal angle moving forwards cranially, the screw length becomes longer. Atlas lateral mass screws could be safely revised whenever needed. The fact that needs to be considered is that the angular range becomes narrower, and the screw length becomes longer when the screw is directed more cranially.

Application of electric drill drive technique in atlantoaxial posterior screw trajectory preparation

Objective To investigate the application effect of electric drill drive in the preparation of atlanto-axial posterior screw trajectory. Methods A retrospective case-control study was conducted to analyze the clinical data of 29 patients with atlanto-axial fracture and dislocation admitted to the Lanzhou University Second Hospital from February 2016 to March 2019. There were 19 male and 10 females, aged from 10 to 72 years, with an average of 44.6 years. All patients received posterior atlantoaxial screw fixation. Electric drill drive was adopted in 14 patients to prepare the screw trajectory (electric drill group), and bare hand technique was used in 15 patients (bare hand group). In the electric drill group, 28 atlantal lateral screws and 28 axial pedicle screws were implanted; in the free hand group, 30 atlantal lateral screws and 30 axial pedicle screws were implanted. The trajectory preparation time and intraoperative blood loss between the two groups were compared. After the operation, the X-ray films and 3D CT were taken to observe the lateral mass of atlas as well as the position, loosening or rupture, and bone healing of axial pedicle screws, and complications. Frankel grading and visual analogue scale (VAS) at the last follow-up were compared between the two groups. Results All patients were followed up for 3 to 36 months, with an average of 21 months. The electric drill group took significantly shorter time in preparing both atlantal and axial pedicle screw trajectories than the bare hand group [(8.8±4.2)minutes ∶(16.5±9.7)minutes; (4.1±1.2)minutes∶ (6.1±3.2)minutes] (P 0.05). In the electric drill group, the penetration rate of atlantal screws was 0, the complete position rate was 96% (27/28), and the good rate of screw placement was 100% (28/28), superior to 23% (7/30), 73% (22/30) and 73%(22/30) in the bare hand group (P 0.05). There were no complications such as cerebrospinal fluid leakage, spinal cord injury, cerebellar infarction, loosening and fracture of internal fixation, and nonunion of bone. At the last follow-up, Frankel grading and VAS of the two groups were improved to different degrees (P 0.05). Conclusion For atlantoaxial fracture and dislocation, preparation of atlantoaxial internal fixation screw trajectories by electric power can significantly shorten the operation time and improve the accuracy of atlas screw placement. Key words: Atlanto-axial joint; Fracture fixation, internal; Electric drill

89. 3D evaluation and classification of the anatomy variations of vertebral artery at the craniovertebral junction

BACKGROUND CONTEXT Patients with basilar invagination (BI) and atlas occipitalization usually present abnormal anatomy of the vertebral arteries (VAs) at the craniovertebral junction (CVJ). PURPOSE To describe and further classify different types of VA variations at the CVJ with 3D visualization technology. STUDY DESIGN/SETTING To display the 3D structures of the VA and bone with different colors to summarize different types of VA variations. PATIENT SAMPLE A total of 120 patients with BI and atlas occipitalization who had undergone 3D-CTA were retrospectively studied. OUTCOME MEASURES Abnormal anatomy of the VA at the CVJ was categorized and related anatomic parameters were measured. METHODS Imaging data were processed via the separating, fusing, opacifying and false coloring-volume rendering (SFOF-VR) technique. RESULTS Seven different types were classified. Type I, the VA enters the cranium after leaving the VA groove on the posterior arch of atlas (26.7% of 240 sides). Type II, the VA enters an extraosseous canal created in the assimilated atlas lateral mass-occipital condyle complex before reaching the cranium (53.3%). Type III, the VA course above the axis facet or curves below the atlas lateral mass then enters the cranium (11.7%). Type IV, the VA enters the spinal canal under the axis lamina (1.3%). Type V, high-riding VA (31.3%). Type VI, fenestrated VA (2.9%). Type VII, absent VA (4.2%). Distance from the canal of Type II VA to the posterior facet surface of atlas lateral mass(5.51±2.17mm) means a 3.5 mm screw can be safely inserted usually. Shorter distance from the midline (13.50±4.35) illustrates potential Type III VA injury during exposure. Decreased height and width of axis isthmus in Type V indicate increased VA injury risks. CONCLUSIONS The courses of VA variations in patients with BI and atlas occipitalization were described and classified into seven different types utilizing the SFOF-VR technique, which is highly recommended as a convenient and concise method for the preoperative evaluation. This new classification system and related anatomical parameters allow for improved understanding of the 3D relationship between the course of VA variations and CVJ anatomy, which is important for minimizing the risk of intraoperative VA injury in patients with congenital anomalies at the CVJ. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Medico-Legal Implications of C1 Vertebral Fractures. Case Report

Abstract Introduction: The upper C1-C2 column is the subject of several erroneous diagnostics. The most common mechanisms of injuries include fall from high-impact skulls, car accidents, etc. Vertebra C1 can also be injured by mild trauma. The Japanese show that atlas fractures occur in about 2-13% of the cervical spine fractures and about 1.3% of the total spinal cord injuries. It is underlined that CT examination is the most useful diagnostic method. The Czechs show that the atlas lesions appear in 1-2% of the cervical spine lesions. Americans reported fracture of the atlas in 7% of the cervical spine fractures. Even if CT has shown its value, lateral radiography is recommended in C1-C2 fractures. When victims are children or people injured in high-speed car crashes, the reported mechanisms were the fall from a high level and the impact on the tip of the flexed skull. The Italians mention that the C1-C2 area is the most exposed diagnostic area with errors. Material and methods: given the difficulty of establishing a diagnosis of C1 type fractures, we present in this paper such a case. We highlight the value of a CT scan. The victim is a 26-year-old woman with a trauma from the wall. The main issue in this case is that the diagnosis made by the radiologist seems to be wrong, the electronic and imprinted copies are of inferior quality. A second opinion revealed a very fine fracture that seemed to come from an older date than the date when the victim claimed she was assaulted. The better the lesions, the more misleading the interpretations. Any imaginary imaging lesion, especially if it is obvious in electronic reconstructions, must be brought to the attention of the physician if they are taken into account by "image". The axial CT sections may omit some lesions under certain conditions, for example at the upper and lower poles of a spherical, ovoid or cubic structure, such as the atlas lateral mass. Conclusions: the diagnostic solution in this case is the reconstruction of the axial sections in several planes. The crack can be highlighted, in the case of a reconstructed image, only after stacking the axial images. The mechanism could be through sudden compression, during a sudden head movement, uninitiated and uncontrolled by the neck muscles, when a movement occurs over the degree of elasticity of the occiput-atlas joint, the occipital condyles compressing abruptly, unilaterally one of the atlas masses. In such clinical cases, we experience pain, muscle contraction and torticollis, on a normal neurological background.

Ponticulus posticus: Its prevalence and implications for screw insertion into lateral mass of atlas: Using plain cervical radiograph

Ponticulus posticus: Its prevalence and implications for screw insertion into lateral mass of atlas: Using plain cervical radiograph

Atlas instrumentation guided by the medial edge of the posterior arch: An anatomic and radiologic study.

Study Design:This was an interventional human cadaver study and radiological study.Objectives:Atlas instrumentation is frequently involved in fusion procedures involving the craniocervical junction area. Identification of the entry point at the center of atlas lateral mass (ALM) is challenging because of its rounded posterior surface and the surrounding venous plexus. This report examines using the medial edge of atlas posterior arch (MEC1) as a fixed and reliable anatomic reference to guide the entry point of ALM screws.Methods:Fifty, normal, cervical spine computed tomography studies were reviewed. ALM screw trajectories were planned at one point along MEC1 and another point 2 mm lateral to MEC1. Free-hand ALM instrumentation was performed in ten fresh human cadavers using the 2 mm entry point, with a sagittal trajectory parallel to atlas inferior arch (IAC1); three-dimensional imaging was then performed to confirm instrumentation accuracy.Results:The average ALM diameter was 12.35 mm. Inserting a screw using the entry point 2 mm lateral to MEC1 was closer to ALM midpoint than using the entry point along MEC1 (P < 0.0001). Twenty ALM screws were successfully inserted in the ten cadavers. No encroachments into the spinal canal or foramen transversarium occurred. However, two screws were superiorly directed and violated the occipitocervical joint; they were not parallel to IAC1.Conclusion:MEC1 provides a fixed and reliable landmark for ALM instrumentation. An entry point 2 mm point lateral to MEC1 is close to ALM midpoint. IAC1 also provides a guide for the sagittal trajectory. Attention to anatomic landmarks may help reduce complications associated with atlas instrumentation but should be verified in future clinical studies.

Minimally invasive surgical treatment for Kimmerle anomaly.

Introduction:Kimmerle anomaly is the bony ridge between the lateral mass of atlas and its posterior arch or transverse process. This bony tunnel may include the V3 segment of the vertebral artery, vertebral vein, posterior branch of the C1 spinal nerve, and the sympathetic nerves, which results in the clinical symptoms of this disease. Reports on the surgical treatment of Kimmerle anomaly are rare. There are no reports on minimally invasive surgical treatment of this pathology.Materials and Methods:Six patients with Kimmerle anomaly were treated from 2015 until 2016. Three patients underwent routine surgery through the posterior midline (posterior midline approach [PMA] group). The other three patients underwent decompression with a paravertebral transmuscular approach (PTMA group). The operation time, intraoperative blood loss, clinical symptoms before and after surgery as well as intra- and post-operative complications were compared between the PTMA and PMA groups.Results:The results of the surgical treatments were assessed at discharge and 1 year later. Blood loss, operation time, and intensity of pain at the postoperative wound area were lower in the PTMA group. There were no postoperative complications. The delayed surgical treatment outcomes did not depend on the method of artery decompression.Conclusions:Surgical treatment of vertebral artery compression in patients with Kimmerle anomaly is preferable in cases where conservative treatment is inefficient. A minimally invasive PTMA is an alternative to the routine midline posterior approach, providing direct visualization of the compressed V3 segment of the vertebral artery and minimizing postoperative pain.

Individualized transoral anterior surgery for complex craniocervical junction disorder with assistance of 3D printing technology

Objective To evaluate the value of 3D printing technology in transoral anterior surgery for complex craniocervical junction disorder. Methods From December 2009 to December 2013, 48 cases of atlantoaxial dislocation associated with complex craniocervical malformation were operated with the assistance of 3D printing technology. There were 19 males and 29 females, with mean 35 years of age (range, 6 to 59 years). Preoperative complications included 28 cases of atlas assimilation, 19 cases of os odontoideum, 17 cases of C2-3 fusion, 1 case of C2-5 fusion, 1 case of C1 posterior arch disconnection, and 1 case of C1 posterior arch aplasia. All cases had symptoms of spinal compression such as numbness and weakness of the extremity, standing or walking unsteady, etc. Preopoerative cervical MRI examinations showed the enlargement of anterior atlas-dens interval (ADI) or atlantoaxial dislocation. All cases' CT data in Dicom form were input into the Simpleware software to reconstruct 3D image, and then the image in STL form was imported to the 3D printer to make a fast prototyping model for the operation with same size as the cases' cervical spine. Based on above works, all cases underwent transoral anterior reduction plate (TARP) fixation in the craniocervical junction zone, including combined anterior-posterior surgery in 1 case. ADI was measured to evaluate the reduction of atlantoaxial dislocation, cervical-medullary angle (CMA) was measured to evaluate the improvement of compression on the medulla, and Japanese Orthopedic Association (JOA) scoring system was used to evaluate the improvement of spinal function. Results All cases went through successful surgery. Mean operation time was (145±45)min and mean blood loss was (53±15)ml. A total of 96 atlas lateral mass screws, 62 reverse axis pedicle screws and 36 axis vertebral body screws, 1 posterior axis pedicle screw and 1 axis translaminar screw were used. Postoperative CT scans showed all screw trajectories were good except that 4 reverse axis pedicle screws violated into the vertebrae artery foramen due to large outward inclination angle. No neurologic defect was found in all cases. Excellent rate of screw placement was 98%. Postoperative CT reconstruction images showed significant atlantoaxial reduction. ADI improved from (8.7±4.9)mm preoperatively to (2.7±1.9)mm postoperatively (P<0.05). CMA changed from preoperative (123±17)° to postoperative (159±18)° (P<0.05). All cases had obvious improvement of spinal compression symptoms. JOA scores improved from (9.5±1.7)points preoperatively to (15.7±0.9)points at 3 months postoperatively (P<0.05). All cases achieved bone union at a follow-up of 10-58 months. Conclusion 3D printing technology is helpful to the operation plan and manipulation for atlantoaxial dislocation associated with complex craniocervical deformities, which may improve the accuracy and safety during the procedure. Key words: Atlanto-axial joint; Dislocations; Imaging, three-dimensional; Computer-assisted design

Atlas Instrumentation Guided by the Medial Edge of the Posterior Arch: An Anatomic Study

Atlas lateral mass (ALM) central point is required for accurate instrumentation. It is described as midway between medial ALM border and C1-transverse foramen. This may be challenging given the rich venous plexus in lateral dissection and the rounded ill-defined medial border of ALM.

Prevalence of ponticuli posticus among patients referred for dental examinations by cone-beam CT

Background contextPonticulus posticus (PP) is the bony bridge that can completely or partially embrace the vertebral artery and the suboccipital nerve root at the atlas posterior arch. The PP can be a possible cause of vertigo, vertebrobasilar insufficiency, neck pain, shoulder pain, and cervicogenic headache. Moreover, the vertebral artery injury may happen during atlas lateral mass screw insertion in the presence of PP. PurposeThe purpose of this study was to determine the prevalence of PP in a population of patients undergoing dental cone-beam computed tomography (CBCT) and the association between PP and atlas superior articular facet (SAF). Study designThis is a retrospective study. Patient sampleFive hundred consecutive patients who had undergone dental CBCT scans were included. Outcome measuresOutcome measures were age, sex, and radiologic measures. MethodsThe maximum anteroposterior and transverse dimensions of atlas SAF were measured on the axial image, and then the area was calculated by using the formula for an elliptical area. The left-right differential ratios of the SAF in patients with unilateral PP were compared with those in age- and gender-matched patients without PP. The relationships among imaging findings, age, and sex were assessed with the two-tailed paired t test, χ2 test, and logistic regression model, as appropriate. ResultsThe overall prevalence of PP was 7% (35 of 500 patients). There were no significant differences in the prevalence of PP with gender and age. The anteroposterior dimension, transverse dimension, and area of atlas SAF on the PP side were significantly larger than those on the non-PP side in the 18 unilateral complete PP patients (p<.001, p<.001, and p<.001, respectively) and in the 11 unilateral partial PP patients (p=.001, p=.007, and p<.001, respectively). The SAF area differential ratios in patients with unilateral PP were greater than those in the patients without PP (29.8% vs. 2.9%, p=.002 for 18 complete lesions, and 23.5% vs. 1.8%, p<.001 for 11 partial lesions). ConclusionsThe prevalence of PP and the measurement of SAF can be assessed by CBCT. The imaging findings show the larger SAF on the PP side and greater left-right difference of SAF area in the patients with unilateral PP.

Anatomic research on atlantoaxial reduction and plate fixation via transoral approach in children

Objective To investigate the feasibility of using transoral anterior reduction plate (TARP) for the atlantoaxial reduction and fixation in pediatric patients.Methods 30 complete sets of cervical CT scan images were obtained from the pediatric patients who had been treated in our department from January 2010 to December 2012.They were 15 boys and 15 girls,with an age range of 5 to 15 years (mean,8.9 ±3.6 years).The children were divided into group A (15 cases,from 5 years old to 9 years old) and group B (15 cases,from 10 years old to 15 years old).The following parameters were measured using tools in the PACS software:transverse and longitudinal diameters,inner and outer heights and width of atlas lateral mass,length of virtual atlas screw path,outward angle of atlas screw,length of axis screw,length of reverse axis pedicle screw,and outward angle of axis reverse pedicle screw.Results The size of lateral mass in both groups could accommodate a 3.5 mm screw.The length of screw path in group A (13.9 ±2.8 mm) was significantly shorter than that in group B (15.9 ± 2.8 mm) (t =2.487,P =0.033).The outward angle of atlas screw in group A (12.4° ± 2.9°) was not significantly different from that in group B (12.0° ± 3.9°) (t =1.546,P =0.136).Group A exhibited a significantly smaller proportion of pedicle width ＞ 3.5 mm [46.7 ％ (7 / 15)],a significantly shorter length of pedicle screw (10.8 ± 2.5 mm) and a significantly shorter length of reverse axis pedicle screw (17.0 ± 2.0 mm) than group B [73.3％ (11/15),11.9 ± 2.7 mm and 20.9 ± 2.3 mm,respectively] (P ＜ 0.05).Conclusions It is basically feasible to use TARP for atlantoaxial reduction and fixation in pediatric patients from 5 to 15 years old,but older children allow for a longer screw path than younger ones.An individualized screw placement is advised when placing screws via transoral approach in pediatric patients. Key words: Children; Anatomy; Atlanto-axial joint; Internal fixators

The selective odontoidectomy: endoscopic endonasal approach to the craniocervical junction.

The resection of the odontoid process via an extended endoscopic endonasal approach has been recently proposed as an alternative to the microscopic transoral method. We aimed to delineate a minimally invasive endoscopic transnasal odontoidectomy and to describe the endoscopic anatomy of the anterior craniovertebral junction (CVJ). The anterior CVJ of 14 fresh adult cadavers were selectively accessed via a binostril endoscopic endonasal approach using 0- and 30-degree endoscopes. The nasopharynx was widely exposed without removing any of the turbinates and without performing a sphenoidotomy. Occipital condyles and lateral masses of the C1 vertebra have been exposed inferiorly at lateral margins of the exposure, in addition to the foramen lacerum, which came into view at the superolateral corner of the operative field. The anterior arch of C1 and the upper 1.5 cm of the odontoid process of C2 have been removed via a minimally invasive endoscopic transnasal approach in all dissections. We propose the selective odontoidectomy as a minimally invasive method for the endoscopic endonasal removal of the odontoid process. By using this approach, turbinates and the sphenoid sinus remain unharmed. In addition, this approach may be used in exposing pathologies situated laterally at the anterior CVJ, such as the lateral masses of atlas and occipital condyles.

Atlas Lateral Mass Screw Fixation in Atlanto-Axial Instability, Clinical Case Series

Background Data: Segmental spinal screw fixation has been used effectively for subaxial spine instability for long time. However, atlantoaxial fixation is still challenging due to complex topographical anatomy. So, sublaminar wires werefrequently used despite their complications. Unlike transarticular atlantoaxial screws which necessitate perfect reduction before insertion, C1 lateral mass screws are inserted independently of C2. Purpose: The aim of this work is to assess the safety and efficiency of C1 lateral mass screw fixation in cases with atlantoaxial instability. Study Design: A prospective clinical case study. Patients and Methods: This study was conducted in Al-Manial university hospital, Kasr Al-Aini Medical School, Cairo University, between 2008 and 2013. Ten patients underwent segmental atlantoaxial screw fixation using atlas lateral mass screws and either transpars interarticularis or transpedicular axis screws. Clinical results were evaluated by using the criteria of Japanese Orthopaedic Association Scoring System for Cervical Myelopathy (JOA score). The surgical technique, results and morbidity and mortality were assessed. Results: There were 6 females and 4 males; the average age was 30.2 ±17.5 y (range from 4y-61 years). The most common cause of atlantoaxial instability wastrauma (6 patients), followed by os odontoideum (2 patients ). The most common presentation was quadriparesis (5 patients) followed by neck pain and paresthesia. At the end of follow up (mean 8.5± 4.2 months) the average preoperative JOA score improved from 13.1±1.9 to 15.2±1.6 (P=0.005) and the average recovery rate was48.3±17.8%. Twenty screws were inserted in lateral mass of atlas successfully. The average screw length was 27.8±1.5mm (range 24-31mm). Postoperative CT scans showed the mean atlantodens interval improved from 5.4±1.9 to 1±1.4 (P=0.004), MRI showed that the mean cervico-medullary angle changed from 126.2°±9.4°to 141.1°±12.4° (P=0.005). There was no mortality or vertebral artery injury. One patient had profuse venous bleeding and one unit of blood was transfused and one patient had superficial wound infection and managed conservatively.Conclusion: C1 lateral mass screw fixation is a safe and effective method of atlantoaxial fixation with low complication rate. (2013ESJ052)

Clinical evaluation of three types of combined posterior atlantoaxial internal fixation techniques for treatment of atlantoaxial instability

Objective To assess clinical curative effect of three types of combined posterior atlantoaxial internal fixation techniques in treatment of atlantoaxial instability. Methods The study involved 68 patients with atlantoaxial instability treated with different fixation techniques from August 2002 to March 2008. ( 1 ) Transpedicular fixation was performed in 32 patients including 20 patients with Anderson Ⅱ odontoid fractures (seven with old odontoid fracture and 13 with fresh fractures), six with type Anderson Ⅲ fresh odontoid fractures, four with disrupt of transverse ligament of the atlas and two with congenital loose odontoid process combined with atlantoaxial instability. (2) Transpedicular internal fixation with screws of atlas incorporating C2 laminar screws was performed in 20 patients with upper cervical injury including eight with type Ⅱ odontoid process fractures combined with atlantoaxial backward dislocation,four with type Ⅱ odontoid process fractures combined with atlantoaxial forward dislocation, two with nonunion of odontoid process fractures, three with type Ⅲ odontoid process fractures combined with atlantoaxial unsteadiness and three with atlantoaxial dislocation combined with disrupt of transverse ligament of atlas. (3)A total of 16 patients with traumatic atlantoaxial instability, reducible atlantoaxial dislocation and irreducible atlantoaxial dislocation were treated with four-point internal fixation technique using autologous iliac bone grafts. Results (1) A total of 120 screws were implanted in 32 patients, with no spinal cord or vertebral artery injury after surgery. Atlas lateral mass fixation was adopted in three patients because of broken posterior arch of the atlas. Postoperative CT showed that two screws were inserted into the vertebral artery hole and that one screw was inserted medially into the spinal canal and caused medial correx rupture, but both with no clinical symptoms. All 32 patients were followed up for 6-42 months ( average 26 months), which showed solid fusion in all patients. The postoperative JOA scores ranged from 13.2 points to 16.8 points (average 14. 8 points). (2) Thirty-two screws were implanted in 20 patients,with no spinal cord or vertebral artery injury. The patients were followed up for mean six months ( range 6-14 months). Postoperative X-ray showed sound bone fusion, with no cervical instability, loosening or breakage of the screws. (3) The symptoms of all the patients were improved at different degrees, with no neurological deterioration or severe complications, such as nerve blood vessel injury. All 16 patients were followed up for 8-26 months ( average 16 months), which showed bony fusion in all patients at 3-6 months after surgery. The spinal cord function was improved markedly in five patients, good in eight, mild in two but unchanged in one. Conclusions Three types of combined posterior atlantoaxial internal fixation techniques have advantages of rigid, short-segmental and three-dimensional fixation and hence are effective methods for treatment of upper cervical injuries. The combination mode can be varied according to specific condition of the patients. Key words: Atlanto-axial joint; Joint instability; Internal fixation; Spinal fusion