C2 Screw Research Articles

Bicortical Short C2 Pars Screw Fixation for High-Riding Vertebral Artery Provided Sufficient Biomechanical Stability: A Finite Element Study.

Finite element analysis. To determine and compare the biomechanical stability of the bicortical short C2 pars screw fixation for high-riding vertebral artery (HRVA) with the C2 pedicle screw and C2 translaminar screw fixation in finite element models. Fixation of C2 is technically demanding in the case of HRVA. However, there is no consensus on the alternative technique for the C2 screw fixation for HRVA in the literature. A finite element model of the upper cervical spine (C0-C2) with HRVA had been developed. C1 pedicle screw was applied at C1 by using notching technique. Bicortical short C2 pars screws, C2 pedicle screws, and C2 translaminar screws were used in each model. Then a vertical load of 50 N and a 1.5 Nm torque were applied to the C0 to simulate flexion, extension, lateral bending, and axial rotation respectively. Compared with C2 pedicle screw fixation, the bicortical short C2 pars screw fixation increased the range of motion by -1.45%, 2.13%, 62.0%, and 22.0% under flexion, extension, lateral bending, and axial rotation, respectively. However, the C2 translaminar screw fixation increased the range of motion by 43.6%, 17.8%, 423.4%, and 19.9%, respectively. In terms of the peak von Mises stress, compared with C2 pedicle screw fixation, bicortical short C2 pars screw decreased 46.1%, 41.6%, 71.3%, and -12.5% under flexion, extension, lateral bending, and axial rotation, respectively; C2 translaminar screw decreased -2.66%, -4.87%, 73.0%, and -10.1%, respectively. For a patient with HRVA, bicortical short C2 pars screw fixation provides sufficient stability and exhibited a smaller von Mises distribution on the screw-rod construct, indicating it could be an effective C2 internal fixation method for HRVA to promote C1-C2 stability and avoid the vertebral artery injury.Level of Evidence: N/A.

A Computed Tomographic Study to Document Anatomical Variations of First Cervical Vertebra: Prevalence, Classification and Possible Clinical Implications

Background - First cervical vertebra has different anatomical features as compared to other cervical vertebrae. It holds globe of skull and lacks body and spine. It is composed of 2 lateral masses linked by anterior and posterior arches. Posterior atlanto-occipital membrane is attached to posterior arch. Lateral edge of this membrane sometimes ossifies thus converting groove into canal. Consequently, neurovascular groove gets converted into a bony ring “ponticulus posticus”. It is considered as potential cause of neck pain and headache. Knowledge of this variation is important during procedures like instrumentation of atlas including C1 lateral mass screw placement which requires mobilization of C2 nerve root and screw insertion inferior to bony arch of atlas directly into lateral mass. In patients with ponticulus posticus, if not identified pre-operatively may give impression of wide bony arch for screw placement, which may result in vertebral artery injury due to a breach of this variation. Congenital defects of atlantal arch a developmental failure of chondrogenesis is a rare anomaly. These defects are a benign variation discovered incidentally. Detection of these anomalies is clinically important as they can cause acute neurologic deficits, which is associated with neck extension. Currarino et al proposed classification of posterior arch anomalies Type A Failure of posterior midline fusion of the 2 hemi arches. Type B Unilateral cleft. Type C Bilateral cleft with persistent dorsal part of arch. Type D Absence of posterior arch with persistent posterior tubercle. Type E Absence of entire posterior arch Objective Objectives this study is to find the prevalence of Ponticulus posticus Congenital anomalies of atlantal arch and classify them Material and Method- 250 computerized tomography (CT) head and neck in axial and sagittal sections from Picture Archiving and Communication System (PACS) of Dr RMLIMS, Lucknow was studied as CT is the best method to study the bony landmarks and any anomaly. Prevalence of variations was calculated. Data was analyzed statistically using SPSS version 21 by Chi-square test. Result- Prevalence of ponticulus posticus was 32.4%. Males had higher prevalence (20.4%) than females (12%). Incomplete ponticulus posticus (24.4%) was more than complete variant (8%). There was predominance of left sided ponticulus posticus(12% vs 8.4%) Deficient posterior arch was found in 9(3.6%) cases. 6 were of type A 3 were of type B. Conclusion- This study will help in determining cause of neurological deficit in patients due to presence of above variations. Significance Accurate evaluation of anatomic landmarks in patient with migraine or neck ache is important because changes in anatomy of atlas may be index pointing towards underlying disease process like vertebrobasilar insufficiency. Asymmetrical deviations of atlas in form, size, shape, and contour are often multiple and confusing. Therefore, they must not only be studied with care and precision and meticulously recorded. In our future project we plan to carry out computed tomographic study to find association of these variations in patients with migraine and cervical pain.

Fluoroscopic landmarks and trajectories for safe posterior percutaneous transarticular C1-C2 screw insertion: a CT-based simulation study.

To determine the safe screw trajectory for posterior transarticular fixation of C1-C2 without direct visualisation of C2 lateral masses and by using fluoroscopic landmarks only. Fluoroscopic models of the craniovertebral region in frontal and sagittal planes were reconstructed using 1-mm interval computed tomography scans of the cervical spine in 30 patients. The imitation model of the screw trajectory was then applied with verification of the exact screw localisation using multiplanar reconstruction. Twenty-seven trajectories for 60 oblique C1-C2 reformations were tested. In the frontal plane, all correct trajectories passed through the medial waistline point (WstP) of C3 and through the middle of the lateral mass of C1. In the lateral plane, the posterior spinal process-lateral mass (SpLM) point-middle C1 anterior tuberculum point (ATP), middle SpLM-upper ATP, and lower SpLM-odontoid point (ODP)-had relatively low rates of vertebral artery (VA) injury (2.3%, 4.6%, and 7%, respectively) and other screw malpositions (6.9%, 4.6%, and 4.6%, respectively). In cases of an isthmus height exceeding 8mm, there were no incidences of VA injury. Patients with an isthmus width greater than 7mm had a lower risk of screw malposition. We identified potentially safe trajectories for percutaneous posterior transarticular fixation of C1-C2. Using SpLM, ATP, and ODP landmarks in the lateral plane, and WstP and C1 middle landmarks in the frontal plane, it is possible to achieve an acceptable screw position without direct visualisation of the C2 lateral mass.

Letter: C2 Pedicle Screws Combined With C1 Laminar Hooks for Reducible Atlantoaxial Dislocation: An Ideal Salvage Technique for C1-C2 Pedicle Screws.

To the Editor: We read the article by Han et al1 with great interest in which the authors describe an innovative option to salvage C1-C2 fusion using laminar hooks instead of pars screws. We take this opportunity to share a similar experience and agree that it is not always possible to place screws in C1 or C2. C1-C2 fusion using C1 lateral mass and C2 pars or pedicle screws is a safe modality for the reduction and fusion of abnormal C1-C2 alignment and instability, including cases of post-traumatic C1-C2 subluxation.2-4 We managed a case of a 4-yr-old child who suffered odontoid tip fracture with rotatory atlantoaxial dislocation (Figure 1) following a fall from a height and presenting with torticollis and quadriparesis. The patient presented to us 2 wk after the fall. A 3-dimensional (3D) computed tomography (CT) reconstruction revealed a thin C2 pars and lamina. Based on CT measurements, a high chance of cortical breach of C2 while placing 3.5-mm pars or pedicle screws was anticipated during preoperative planning. Hence, that laminar screws over C2 could be an option during surgery was kept as an alternative salvaging procedure. The subluxation reduced under traction as soon as bilateral C1-C2 joints were opened and further distracted using dissectors. Then C1-C2 joint surfaces were curetted, and bone chips from iliac crest were inserted. The placement of C2 pedicle, pars, or laminar screws is considered to be more technically demanding than C1 lateral screw placement.5 Often, it is the C2 screw placement that more commonly leads to vascular or neural injury.6 This is particularly true in the case of children in which the small dimension of C2 makes it even more difficult to place screws of diameter 3.5 mm, which is the commonly available size.FIGURE 1.: Preoperative imaging of the patient showing the odontoid fracture and atlantoaxial dislocation A in the sagittal view. In the 3D CT angiogram, the right lateral mass of C1 is not visible B from the posterior view, which is seen subluxated anteriorly in the anterior view C.C1 lateral mass screws were placed according to the technique described by Goel et al.7 Because C2 dimensions were very thin for 3.5-mm screws, laminar hooks were placed bilaterally over C2 and minirods placed between C1 lateral mass screws and C2 laminar hooks. Finally, the C1 and C2 laminae were decorticated and iliac crest graft placed to achieve posterior bony fusion as well. A repeat scan at 3 mo showed good decompression of the craniovertebral junction and cord along with the implant in Situ (Figure 2). The patient's myelopathy has improved and is now mobilized independently. Therefore, in cases in which certain factors preclude the use of C2 pars/pedicle or lamina screws, C2 laminar hooks can be a useful rescue adjunct.FIGURE 2.: Postoperative CT showing a good reduction achieved with restoration of canal space in the sagittal view A. The 3D color rendering on maximum intensity projection B shows the C1 lateral mass screws and C2 laminar hooks in Situ.Funding This study did not receive any funding or financial support. Disclosures The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.

An alternative way of C1 screwing: Supralaminar C1 lateral mass screws.

Study Design:This study involves literature review, technical note, and case series.Objectives:The objectives were to analyze indications and contraindications, advantages, and disadvantages for C1 lateral mass screw (LMS) insertion above or partially above the arch, to descript technical features, and to give examples of the practical application of this technique and investigated its safety.Methods:A literature review was carried out in English and Russian in PubMed, Google Scholar, and eLibrary databases. We selected four patients, treated in our clinic, which was carried out partially supralaminar C1 LMS.Results:Only three descriptions of supralaminar C1 LMS were found in the literature. Four adult patients underwent posterior C1–C2 screw fixation with C1 LMS along the superior edge of the C1 arch at our clinic. Partially supralaminar C1 screws were inserted on one of the sides due to the difficulties of using classical techniques. The main reasons for supralaminar screw fixation were narrow C1 lamina, hypertrophied venous plexus, and intraoperative failures of classic techniques application (broken screw trajectory, profuse venous bleeding from the plexus). The average follow-up time for the patients was 2.7 years, no complications were noted, and all had a satisfactory spinal fusion.Conclusions:The proposed types of C1 LMS above or partially above the C1 arch can be useful alternative method of C1 screwing in selected patients. Indications for the use of the supralaminar C1 LMS method can be narrow C1 posterior arch and pedicle, pronounced C1-C2 venous plexus, some V3 segment anomalies at C1 level, small arthritic inferior part of lateral mass, and intraoperative failures of classic techniques application.

Study of the functional results of the percutaneous surgical treatment of subtle injuries of the tarso-metatarsian complex

Introduction and objectivesThe concept "subtle Lisfranc" defines low energy lesions of the tarsometatarsal joint complex (TMC) that involve joint instability. Often unnoticed, with long-term sequelae.The objective is to evaluate the clinical-functional results of patients with MTC ligament damage grade II-III (Nunley and Vertullo classification) treated with percutaneous surgery. Material and methodsRetrospective study of 16 patients who underwent percutaneous surgery for MLC ligament damage. Demographic data, days of delay in diagnosis, surgical technique, joint reduction in load (adequate if C1-M2 space is less than 2 mm) and Manchester-Oxford scale (MOXFQ) score were collected. The sample consisted of 9 males and 7 females, mean age 43.6 years (17–71) and mean follow-up of 22 months (12–28). ResultsDiagnosis was delayed for more than 24 h in 4 patients (3–6 days). In 11 patients the treatment consisted of closed reduction and percutaneous synthesis with cannulated screws from M2 to C1 and from C1 to C2. In 3 patients it was supplemented with Kirschner wires in the lateral radii. 2 patients were treated with only M2 to C1 screws. An anatomical reduction was not achieved in 6 patients, with a mean of 2.6 mm between C1-M2 (2.1−3 mm); the mean functional MOXFQ score of these patients was 41.1% (IC95% 23.1%–59.1%), worse results compared to the anatomical reduction: 17.2% (IC95% 5.7–28.7); statistically significant difference (p < 0.01). ConclusionSubtle injuries from MTC are rare and can go unnoticed. Surgical treatment with percutaneous synthesis offers good clinical-functional results in the medium term. The anatomical reduction is a determining factor for the good functional result of our patients.

Evaluation of the Accuracy of Free-hand C1 and C2 Screw Placement

Objective Posterior atlantoaxial fixation is an effective treatment for various pathologies. The anatomies of the atlas and axis are highly complex, and thus, freehand placement of C1, 2 instrumentation is technically challenging. The objective of this study was to evaluate the accuracy and safety of C1, 2 screw placement without fluoroscopic or any other guidance method by a 2-year spine surgeon. Methods A retrospective analysis of radiologic data was performed on all patients that underwent C1 or C2 instrumentation from April 2019 to January 2020; all procedures were performed by a 2-year spine surgeon. Computed tomography was used to assess cortical breaches of screw placement at C1 or C2. Severities of breaches were quantified using percentages screw diameter beyond cortical edges (0=cortical touch, 1≤25%; II=26-50%; III=51-75%; IV=76-100%). Results The surgeon placed 16 C1 screws and 20 C2 screws in 10 consecutively treated patients. For C1 screws, there were 4 breaches (25%), of which 3 were medial (18%) and 1 was anterior (7%), and for C2 screws, there were 3 total breaches (15%), of which 2 were anterior (10%) and 1 was medial (5%). Breaches were classified as grade I in 3 cases (42.8%), grade III in 1 case (14.4%), and grade IV in 3 cases (42.8%). No clinical sequelae were attributed to these breaches. Conclusion Although 25% of C1 screws and 15% of C2 screws placed using a freehand technique without guidance may be achieved accurately and safely. Preoperative morphometric evaluation and controlled exposure to this unique anatomy are essential to improve screw placement. Key Words: Accuracy of screws; Free hand technique; Malposition; Posterior atlantoaxial fixation; VA injury

Comparative study of 3D printed navigation template-assisted atlantoaxial pedicle screws versus free-hand screws for type II odontoid fractures

The objective of the study was to compare the safety, efficacy, and accuracy of the pedicle screws with the three-dimensional (3D) printed navigation template to the free-hand screws for type II odontoid fractures. A total of 60 patients with type II odontoid fractures, treated with either template guiding pedicle screws or free-hand screws, were retrospectively assessed. The guiding group was treated with pedicle screws with the assistance of a virtual reality (VR) software-designed, 3D printed navigation template with two guide tubes. The safety rate and treatment efficacy of the screw placement, as well as the trajectory accuracy, were evaluated by respective measures and compared between two surgical groups. There were reduced surgical time (P < 0.05), blood loss (P < 0.01), and C-arm shots (P < 0.01) with 3D printed template guiding screws. The rates of safe pedicle screws in both C1 and C2 were significantly higher in 3D guiding group (P < 0.01) compared to the free-hand group, and the scores of visual analogue scale (VAS) and impairment scale (ASIA) were improved in guiding group at 1week post-surgery (P < 0.01 and P < 0.05, respectively). Postoperative CT and image reconstruction showed the 3D guiding group had better horizontal screw accuracy on both sides of C1 (L: P < 0.001, R: P < 0.01) and C2 (L: P < 0.001, R: P < 0.01) than free-hand group. The herein screw technique using 3D printed navigation template leads to greater improvement in the screw safety, efficacy, and accuracy, which may be a promising alternative to free-hand surgery for the treatment of odontoid fractures.

Usefulness of ipsilateral translaminar C2 screws insertion for cervical fixation in children with a low laminar profile: a technical note.

The fusion of the upper cervical spine in children is demanding due to its reduced size, its anatomical complexity, or a severe pathology of the cranio-cervical junction. In some pediatric patients with today's more popular C1-C2 or, occipito-C2 techniques, it is impossible, or very risky to perform a short upper cervical fixation. We present the utility and good results of ipsilateral laminar C2 screws insertion technique in two pediatric cases with low C2 laminar profile. Case 1: a 5-year-old child with a C1-C2 unstable subluxation, and a condylar assimilation of C1, where we performed an occipito-C2 fixation using an occipital plate and this modified translaminar C2 screw technique. Case 2: a 8-year-old Down syndrome boy who suffered an unstable subluxation of C1-C2 upon whom we performed a C1-C2 screw fixation using the same technique. Both cases have been followed up over a period of 7 and 2 years respectively, with good clinical results. We describe the technique and the feasibility of the ipsilateral insertion of translaminar C2 screws in children with low laminar profiles, as a good alternative to other techniques when the anatomy of the C2 does not permit its use or make them very risky.

Resultados funcionales del tratamiento quirúrgico percutáneo de las lesiones sutiles del complejo tarso-metatarsiano

Introduction and ObjectivesThe concept subtle Lisfranc defines low energy lesions of the tarsometatarsal joint complex (TMC) that involve joint instability. Often unnoticed, with long-term sequelae. The objective is to evaluate the clinical-functional results of patients with MTC ligament damage grade II-III (Nunley and Vertullo classification) treated with percutaneous surgery. Material and MethodsRetrospective study of 16 patients who underwent percutaneous surgery for MLC ligament damage. Demographic data, days of delay in diagnosis, surgical technique, joint reduction in load (adequate if C1-M2 space is less than 2 mm) and Manchester-Oxford scale (MOXFQ) score were collected. The sample consisted of nine males and seven females, mean age 43.6 years (17-71) and mean follow-up of 22 months (12-28). ResultsDiagnosis was delayed for more than 24 hours in four patients (3-6 days). In 11 patients the treatment consisted of closed reduction and percutaneous synthesis with cannulated screws from M2 to C1 and from C1 to C2. In three patients it was supplemented with Kirschner wires in the lateral radii. Two patients were treated with only M2 to C1 screws. An anatomical reduction was not achieved in six patients, with a mean of 2.6 mm between C1-M2 (2.1-3 mm); the mean functional MOXFQ score of these patients was 41.1% (IC 95% 23.1-59.1%), worse results compared to the anatomical reduction: 17.2% (IC 95% 5.7-28.7); statistically significant difference (p < 0.01). ConclusionSubtle injuries from MTC are rare and can go unnoticed. Surgical treatment with percutaneous synthesis offers good clinical-functional results in the medium term. The anatomical reduction is a determining factor for the good functional result of our patients.

The internal carotid artery and the atlas: anatomical relationship and implications for C1 lateral mass fixation.

The internal carotid artery (ICA) is potentially at risk during posterior fixation of C1. In this study, we performed a CT-based anatomical analysis of the relationship between the internal carotid artery and the lateral mass of the atlas. We analysed 30 CT angiography of the cervical spine, and we measured on both sides the distance of the carotid artery from the midline, distance of the ICA from the anterior cortex of C1 and from the ideal C1 screw entry point. We measured the angle between the sagittal plane passing through the entry point and the tangent line of the vessel. Separated statistical analysis between left and right sides, between male and female patients, and differentiation by age were also performed. Sixty ICAs were studied. The mean distance of the ICA from the midline was 23.3 ± 4.3mm, with a minimum of 15mm. The distance between the ICA and the anterior cortical layer of C1 was 4.8 ± 2.7mm, with a minimum of 1.1mm. The distance between the screw entry point and the arterial wall was 22.6 ± 2.8mm, with a minimum of 17.5mm. The mean angle was 10.4°, with a minimum of 11°. Although rare, intraoperative lesion of the ICA is reported and the spine surgeon must be aware of this risk. Careful preoperative planning is mandatory and the position of the ICA in relation to C1 must be assessed. The anatomical parameters presented in this paper can be useful to reduce the risk of ICA injury.

Technical outcome of atlantoaxial transarticular screw fixation without supplementary posterior construct for rheumatoid arthritis.

Background: transarticular screw (TAS) fixation without a supplementary posterior construct, even in rheumatoid arthritis (RA) patients, provides sufficient stability with acceptable clinical results. Here, we present our experience with 15 RA patients who underwent atlantoaxial (AA) TAS fixation without utilizing a supplementary posterior fusion.Methods: To treat AA instability, all 15 RA patients underwent C1–C2 TAS fixation without a supplementary posterior construct. Patients were followed for at least 24 months. Pre- and postoperative sagittal measures of C1– C2, C2–C7, and C1–C7 angles, atlanto-dens interval (ADI), posterior atlanto-dens interval (PADI), and adjacent segment (i.e., C2–C3) anterior disc height (ADH) were retrospectively recorded from lateral X-ray imaging. The presence or absence of superior migration of the odontoid (SMO), cervical subaxial subluxation, C1–C2 bony fusion, screw pull-out, and screw breakage were also noted.Results: There was little difference between the pre- and postoperative studies regarding angles measured. Following TAS fixation, the mean ADI shortened, and mean PADI lengthened. There was no difference in the mean measures of C2–C3 ADH. There was no evidence of SMO pre- or postoperatively. Two patients developed anterior subluxation at C5–C6; one of the two also developed anterior subluxation at C2–C3. All patients subsequently showed C1–C2 bony fusion without screw pull-out or breakage.Conclusion: In RA patients who have undergone C1–C2 TAS fixation, eliminating a supplementary posterior fusion resulted in adequate stability.

Mobilization of the high-riding vertebral artery for C2 screw insertion.

The basic surgical steps in the Goel technique of atlantoaxial fixation involve exposure of the atlantoaxial articulation, denuding of the articular cartilage, stuffing of bone graft pieces within the articular cavity, and subsequent instrumentation.“High-riding” vertebral artery in relationship to the pedicle-facet of C2 has been widely recognized to be a factor that makes insertion of the C2 pedicle-facet screw difficult or impossible. In this video, a technique of exposure and mobilization of the high-riding vertebral artery to permit safe C2 screw insertion is shown. An alternative option in the presence of such a high-riding vertebral artery is to use either C2 laminar or inferior facetal screw insertion.The video can be found here: https://youtu.be/LjxxINmzph0

Comparison of Atlantoaxial Fusion with Transarticular Screws and C1 Lateral Mass–C2 Screws Using Intraoperative O-Arm Navigation

This study compared the surgical outcomes of atlantoaxial fusion with transarticular screws (TASs) and C1 lateral mass-C2 screws (screw-rod constructs [SRCs]) using the intraoperative O-arm navigation system (O-arm). Among a total of 28 patients who underwent atlantoaxial fixation, 13 underwent TAS fixation and 15 underwent SRC fixation using the O-arm. All patients underwent Brooks procedure with iliac bone graft in addition to screw fixation. TAS fixation was performed for cases without high-riding vertebral artery (hVA). In the SRC group, pars or lamina screws were inserted for the side with a C2 hVA. Operative time, intraoperative bleeding, perioperative complications, screw accuracy, and bone union were evaluated. There were statistically significant differences in mean operative time between the 2 procedures (166 minutes in the TAS group vs. 212 minutes in the SRC group, P < 0.05) and in mean blood loss (80 vs. 185 mL, respectively; P < 0.01). Two patients developed temporary postoperative occipital neuralgia probably related to C2 nerve root in the SRC group. No screws violated the cortex in either group. Complete bone union was observed in all cases. O-arm-assisted TAS fixation had less intraoperative blood loss, shorter operative time, and fewer screw insertion complications than O-arm-assisted SRC fixation. O-arm-assisted TAS fixation is preferable for atlantoaxial fusion in patients without hVA.

The C2 Cortical Screw, an Alternative Fixation Technique for the C2 Segment During High Cervical Spine Surgery: Technical Note

For posterior fixation of C2 vertebra (the axis), several fixation techniques such as pedicle screw, laminar screw, and pars screw have been reported. A pedicle screw (PS) is considered the strongest among the techniques, but certain situations make PS fixation impossible or difficult. These include patients with a narrow C2 pedicle or high-riding vertebral artery. We introduced an alternative screw technique for C2 that addressed the aforementioned problems with safely placing it, which we termed a cortical screw (CS) for C2. Among a total of 28 cases using C2 CS for high cervical spine surgery, 2 cases using C2 CS were described. One patient was a 76-year old woman with a gait disturbance and myelopathic symptoms and diagnosed with C1-C2 myelopathy and translational instability. The other case was 54-year old man with posterior neck pain after traffic accident and diagnosed with C1-C2 fracture-dislocation. We used the C2 CS as an alternative technique for high cervical spine surgery in these patients and describe the ideal entry point and trajectory. A postoperative computed tomography scan confirmed proper positioning of the C1 posterior arch screw and C2 CS, with satisfactory reduction of the C2 dens and adequate restoration of the C1-C2 spinal canal. The patient experienced no screw-related postoperative complications, and postoperative 1-year computed tomography images showed that solid union and good alignment of C1-2 segment was achieved. C2 CS can be suitable alternative for C2 screw fixation technique in posterior high cervical spine fusion surgery.

Mobilization of the Vertebral Artery-Surgical Option for C2 Screw Fixation in Cases With "High Riding" Vertebral Artery.

Mobilization of intraosseous course of vertebral artery for safe screw insertion into pedicle of axis in cases with high riding vertebral artery is discussed. To show drilling, exposure, and mobilization of the "high-riding" vertebral artery loop during its course in relationship with superior facet/pedicle of C2 vertebra can provide safety to techniques of atlantoaxial fixation that involve insertion of screws in the pars/pedicle/facet of C2. During the period June 2016 to April 2018, 15 patients operated for atlantoaxial stabilization underwent vertebral artery exposure and mobilization using the technique discussed. The ages of the patients ranged from 6 to 48 yrs. Four patients had mobile and reducible atlantoaxial dislocation. Seven patients had basilar invagination. Four patients had os-odontoideum. Gentle and precise drilling of bone that covers the "high-riding" vertebral artery can lead to its safe and wide surgical exposure. The arterial loop can then be either completely or partially mobilized out of the vertebral artery groove such that C2 screw insertion can be conducted under direct surgical visualization of the vertebral artery. During the average follow-up period of 14 mo, there have been no complications related to the surgical procedure, metal implant, or vertebral artery. Vertebral artery exposure and mobilization is rather simple and safe procedure and is remarkably effective in providing a space for C2 screw implantation.

C2 medial pedicle screw: a novel "in-out-in" technique as an alternative option for posterior C2 fixation in cases with a narrow C2 isthmus.

The authors describe a novel "in-out-in" technique as an alternative option for posterior C2 screw fixation in cases that involve narrow C2 isthmus. Here, they report the preliminary radiological and clinical outcomes in 12 patients who had a minimum 12-month follow-up period. Twelve patients with basilar invagination and atlantoaxial dislocation underwent atlantoaxial reduction and fixation. All patients had unilateral hypoplasia of the C2 isthmus that prohibited insertion of pedicle screws. A new method, the C2 medial pedicle screw (C2MPS) fixation, was used as an alternative. In this technique, the inner cortex of the narrow C2 isthmus was drilled to obtain space for screw insertion, such that the lateral cortex could be well preserved and the risk of vertebral artery injury could be largely reduced. The C2MPS traveled along the drilled inner cortex into the anterior vertebral body, achieving a 3-column fixation of the axis with multicortical purchase. Satisfactory C2MPS placement and reduction were achieved in all 12 patients. No instance of C2MPS related vertebral artery injury or dural laceration was observed. There were no cases of implant failure, and solid fusion was demonstrated in all patients. This novel in-out-in technique can provide 3-column rigid fixation of the axis with multicortical purchase. Excellent clinical outcomes with low complication rates were achieved with this technique. When placement of a C2 pedicle screw is not possible due to anatomical constraints, the C2MPS can be considered as an efficient alternative.

Temporary Bridge Occipitocervical Fixation for Comminuted Atlantoaxial Fracture

We sought to evaluate the feasibility of temporary bridge occipitocervical fixation temporary bridge occipitocervical fixation (T-BOCF) for comminuted atlantoaxial fractures. A 57-year-old man presented with multiple trauma including a comminuted, undisplaced atlantoaxial fracture; subdural hemorrhage; skull base fracture; scalp laceration; right second finger tendon injury; and right distal femur open fracture. T-BOCF was performed to preserve neck motion while providing rigid stability to atlantoaxial fracture. Occipital plate and bilateral lateral mass screws were inserted at C3, C4, and C5, avoiding the fracture site; this was followed by rod connection without fusion. The screw-rod construct was removed after confirmation of bone union in the fracture site 12 months after the initial operation. Computed tomography performed at 12 months after the operation demonstrated solid bone union. Dynamic radiographs taken 12 months after implant removal demonstrated a flexion-extension range of motion of 16 degrees at C0‒C2 and 19.8 degrees at C2‒C7. The total flexion-extension range of motion was 35.8 degrees. T-BOCF is a viable option for treatment of comminuted, undisplaced atlantoaxial fractures. The technique is easier than direct C1‒C2 fusion and can avoid complications associated with occipitocervical fusion or C1‒C2 screw fixation. The blood supply to the fracture site is preserved by avoiding subperiosteal stripping, and semispinalis cervicis insertion at the C2 spinous process is also circumvented. Furthermore, neck motion is preserved after implant removal.

Posterior fusion of the craniocervical junction in the pediatric spine: Wright's translaminar C2 screw technique provides for more safety and effectiveness.

Posterior fusion of the craniocervical junction (CCJ) has always been challenging in children with rare congenital diseases and malformations. At our institution, the introduction of the translaminar C2 screw technique led to a significant improvement in the quality of treatment. Retrospective analysis of a pediatric cohort at a single institution whounderwent CCJposterior fusion between 2007 and 2018. Patients were divided into group 1 (other posterior fusion techniques, n = 12) and group 2 (translaminar axis screw placement, n = 19). Diagnosis, sex, age at surgery, surgical technique, immobilization, revisions, fusion, reduction, and complications were assessed. Follow-up ranged from 12 to 145months (mean 50.7). The initial fusion rate detected at 3months by CT differed significantly (66, 7% in group 1 vs. 100% in group 2, p = 0.018). Full reduction of C1/C2 malalignments was achieved in 41, 6% of group 1 versus 84, 2% of group 2 (p = 0.007). Immobilization was applied in 83, 3% of group 1 versus 26, 3% of group 2 (p = 0.0032). Ten complications were treated conservatively, and 15 events required revision surgery (80% in group 1 vs. 20% in group 2). Eight complications were related to immobilization. The implementation of the translaminar C2 technique resulted in significantly more safety and efficiency regarding pediatric posterior fusion CCJ surgery at our institution, with significantly higher rates of rigid fixation, full reduction, and fusion, and significantly lower rates of complications and immobilization. These slides can be retrieved under Electronic Supplementary Material.

Morphometry of the C2 Pedicle and Lamina in Thai Patients.

Background:Traumatic upper cervical spine leads to instability and neurological deficit. At present, C2 (axis) pedicle or lamina screws for fixation are popular because further external immobilization is not needed. However, these techniques demand experience inserting the screws and carry the risk of vertebral artery or spinal cord injury. In some patients, the C2 screws cannot be inserted because of limited C2 size.Objective:To determine the width, length, height, and angle in the C2 pedicle and lamina in the Thai population.Materials and Methods:Patient data were collected from the Picture Archiving and Communication System at the Faculty of Medicine, Prince of Songkla University from January 2016 to December 2017. The C2 parameters, i.e., width, length, height, and angle of the pedicle and lamina were recorded.Results:The CT C-spine scans of 270 patients were enrolled. The mean Thai C2 pedicle dimensions were width 5.51 mm, length 23.78 mm, angle 39.04°, and height 8.64 mm. The mean C2 lamina dimensions were width 5.88 mm, length 32.17 mm, angle 49.46°, and height 12.27 mm. Twenty-four patients from the 270 patients (8.8%) had a pedicle width <3.5 mm but all patients had a lamina width ≥3.5 mm.Conclusion:In the Thai samples, 8.8% had a C2 pedicle width <3.5 mm which would not allow insertion of screws; however, they could be replaced with lamina screws since the lamina width was ≥3.5 mm. In this study, all of the patients who could not be inserted pedicle can be replaced with lamina screws inserted.