C2 Pedicle Screw Research Articles

Single-Staged Transoral Intra-Lesional Excision of Aneurysmal Bone Cyst of Axis (C2) Vertebra and Temporary Stabilization of Upper Cervical Spine in an Adolescent: A Case Report

Aneurysmal bone cyst (ABC) infrequently occurs within the upper cervical vertebrae. Various therapeutic options have been reported in the literature. We would like to share our experience in managing a case of a 16-year-old girl diagnosed with ABC at the body of axis (C2) vertebra. Serious attention had to be given on the stability of the cervical spine following tumour resection, which can be affected by the mode of treatment chosen. Instability can have a detrimental effect on the cervical spine, in which case may necessitate further surgery. We performed a single-staged intra-lesional curettage via a transoral approach and temporary non-fusion posterior stabilization of C1 lateral mass screw and C2 pedicle screw. The implants were removed after six months once ossification of C2 has taken place to regain full motion of the neck. There was no evidence of recurrence or instability of the cervical spine three years following surgery.

A Novel Construct Incorporating C2 Unilateral Pedicle and Contralateral Translaminar Screws for Occipitocervical Internal Fixation: An In Vitro Biomechanical Study

Occipitocervical fixation using bilateral C2 pedicle screws (C0-C2BiPS) and occipitocervical fixation using bilateral C2 translaminar screws (C0-C2BiLS) provide satisfactory stability. Bilateral fixation is not feasible for cases of C2 unilateral pedicle morphology abnormality and ipsilateral laminectomy. This study proposed and evaluated novel occipitocervical fixation using C2 unilateral pedicle screw and contralateral translaminar screws (C0-C2PSLS). In 6 human cadaveric specimens, an invitro experiment was performed with 2.0-Nm moment control in flexion-extension, lateral bending, and axial rotation to investigate biomechanical stability. Neutral zone and range of motion (ROM) between the occiput (C0) and C2 were measured in the intact state, after destabilization, and after sequential stabilization using C0-C2BiPS, C0-C2BiLS, and C0-C2PSLS constructs. Flexion-extension ROM of the intact specimens at C0-C2 was 27.4° ± 2.4°. Instrumentation with C0-C2PSLS, C0-C2BiPS, and C0-C2BiLS reduced flexion-extension ROM to 3.7° ± 1.3°, 4.7° ± 1.4°, and 4.5° ± 1.4°, respectively. In lateral bending, ROM values were 7.0° ± 0.6°, 4.5° ± 1.4°, 4.2° ± 1.4°, 2.7° ± 1.0°, respectively. In axial rotation, ROM values were 65.3° ± 5.7°, 2.5° ± 0.5°, 1.4° ± 0.5°, and 0.9° ± 0.6°, respectively. Comparing destabilized and intact specimens, all 3 constructs significantly reduced ROM and neutral zone values in flexion-extension, lateral bending, and axial rotation (P<0.05). Direct comparisons between the 3 constructs revealed no significant difference (P > 0.05). Novel C0-C2PSLS provides similar stabilization effect as C0-C2BiPS and C0-C2BiLS constructs and has potential for clinical use, especially for cases of C2 unilateral pedicle morphology abnormality and ipsilateral laminectomy.

Comparison of the Accuracy of C1 Pedicle Screw Fixation Using Fluoroscopy and Free-Hand Techniques in Patients With Posterior Arch Thickness of Less Than 4 mm.

C1 pedicle screw insertion is not easy, and more fluoroscopy can be required for safe insertion. Fluoroscopy is time consuming and increases patient radiation exposure. There have been no studies comparing the accuracy of C1 pedicle screw insertion using the fluoroscopy and free-hand techniques. To describe a free-hand C1 pedicle screw insertion method in patients with the posterior arch thickness of less than 4 mm in the thinnest part of the groove, and to compare the clinical and radiological outcomes of C1 pedicle screw insertion using fluoroscopy vs using the free-hand technique. A total of 25 patients who had atlantoaxial instability with a C1 posterior arch<4 mm and were treated with C1 pedicle screw insertion were included. In 10 patients, fluoroscopy was used for C1 pedicle screw insertion, and 15 patients underwent the free-hand technique. We compared the radiologic and clinical outcomes between the 2 groups. In patients who underwent the free-hand technique, 96.5% of screws were rated as safe (grade A or B), and 80.0% of screws in the fluoroscopy group were rated as safe. Postoperative occipital neuralgia occurred in one patient in the fluoroscopy group and did not occur in the free-hand technique group. There was no significant difference in the improvement of Nurick grade between the 2 groups. C1 pedicle screw insertion using the free-hand technique is feasible and safe in patients with a C1 posterior arch<4 mm.

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

A C1 laminar hook can theoretically avoid vertebral artery injury and is less technically demanding. However, only few studies with small samples analyzed the short-term outcomes of C2 pedicle screws combined with C1 laminar hooks (C2PS-C1LH) technique in the treatment of atlantoaxial dislocation. Furthermore, it is not confirmed whether similar clinical outcomes can be achieved with C1-C2 pedicle screw and rod construct (PSRC). To evaluate the outcomes of C2PS-C1LH and C1-C2 PSRC fixation techniques for treating atlantoaxial dislocation. Data of 52 patients with atlantoaxial dislocation treated by C1-C2 PSRC or C2PS-C1LH fixation were retrospectively reviewed. Outcomes evaluated by visual analog scale score for neck pain (VASSNP), Neck Disability Index (NDI), atlantodental interval (ADI), and the perioperative parameters including blood loss and operation time were analyzed and compared between 2 techniques. Patient satisfaction at final follow-up was also investigated. There were no complications related to the surgical approach and instrumentation in either group. The mean bone fusion time was 5.06±1.65 mo for the C2PS-C1LH group and 3.93±0.99 mo for the C1-C2 PSRC group (P > .05). Hundred percent of fusion rates were achieved in both groups at month 12 after operation. The ADI, VAS scores, the NDI scores, and the JOA scores were greatly improved in both the groups (P<.05), but there were no significant differences between the 2 groups. C2PS-C1LH fixation technique was comparable to C1-C2 PSRC in the treatment of reducible atlantoaxial dislocation. C2PS-C1LH fixation was an ideal alternative strategy to C1-C2 PSRC fixation.

Short Segment Rigid Fixation for a Patient of Basilar Invagination and Assimilated C1 With Quadriparesis

Background &amp; Importance: Atlas assimilation is the congenital Atlas fusion with the base of the occipital bone. Case Presentation: A patient was presented with neck pain, dysaesthesia and tingling of hands and feet and difficulty in walking for 4 years. On examinations, the patient had a short neck with rigidity in neck muscles and there were exaggerated jerks with bilateral Babinski sign. Cervical spinal x-ray indicated basilar invagination with the absence of a C1 arch and CT scan of the cervical spine showed assimilation of C1 with basilar invagination. Occipitocervical stabilization has been commonly proposed for the operational fusion. The iliac crest interposing bone graft was performed for fusion and stabilization of the occipitocervical region. The patient was treated surgically and soon after operation became painless and was able to move easily. Conclusion: In C1 assimilation with basilar invagination, bicortical occipital screws and C2 pedicle screws with interposition bone graft can be the way to optimize the shortest segmental stabilization and fusion procedure for occipitocervical fusion.

Techniques and Tips for Freehand Placement of C7 Pedicle Screws With Respect to Cervicothoracic Constructs: 2-Dimensional Operative Video.

We present a surgical video highlighting the technical pearls for C7 pedicle screw placement with respect to cervicothoracic constructs. Pedicle screw placement into C7 has been shown to enhance the biomechanical stability of both cervical and cervicothoracic constructs and is safe for patient related outcomes.1,2 Rod placement across the cervicothoracic junction is known to be difficult because of the variable starting point of the C7 pedicle screw, which may cause misalignment of the polyaxial heads with respect to the C7 and C6 screw heads. Using our step-wise method of anatomic screw placement, this potential pitfall is minimized. The T1 pedicle screw is placed first. The C6 lateral mass screw starting point is displaced slightly superiorly from the midpoint of the lateral mass in order to make room for the polyaxial head of the C7 pedicle screw. A small laminotomy is performed in order to find the medial border of the C7 pedicle. Palpation of the medial border allows for an approximation of the pedicle limits. The cranial-caudal angle of drilling is perpendicular to the C7 superior facet, and the medial-lateral trajectory typically falls between 15 and 20 degrees medial. Once the pedicle is cannulated, a ball-tipped probe is used to confirm intraosseous position. A rod is cut and contoured to the appropriate length of the construct. The C7 pedicle screw should capture the rod easily with slight displacement of the polyaxial head. Postinstrumentation anteroposterior and lateral fluoroscopy are performed to confirm good position of the lateral mass and pedicle screws. Patient consent was not required for this cadaveric surgical video.

Outcomes of occipitocervical fixation using a spinous process screw in C2 as a third anchor point for occipitocervical fixation: a case presentation

BackgroundPosterior occipitocervical fixation and fusion are often required to address occipitocervical instability. Safe, stable internal fixation with screws is vital for the success of such surgery. Thus, poor selection of an internal fixation technique may cause fixation and fusion failure, possibly leading to neurovascular injury. Hence, in certain cases, such as in patients with severe instability of an occipitocervical deformity or osteoporosis, we hypothesized that having a third anchor point (a screw in C2) could enhance the stability of the occipitocervical fixation.Case presentationA 31-year-old man with occipitocervical deformity and spinal cord edema underwent a traditional occipitocervical fixation procedure but with the addition of a spinous process screw in C2 as a third anchor point. The procedure included posterior internal fixation and fusion. The occipitocervical fixation was completed by inserting occipital screws, bilateral C2 pedicle screws, C3 lateral mass screws, and a spinous process screw in C2 as a third anchor point. There were no neurovascular complications or incision-site infections. Postoperatively, radiography and computed tomography showed that the occipitocervical reduction and internal fixation had resulted in good spinal alignment, and magnetic resonance imaging showed no obvious spinal cord compression. At 4 months after the surgery, fusion was observed, and the occipitocervical screws remained well positioned. The patient continued to be monitored for 24 months postoperatively. At the 24-month follow-up visit, the muscle strength of the limbs was grade 5, and the patient’s sensation function had improved over his preoperative condition.ConclusionsUse of a C2 spinous process screw as a third anchor point may enhance the stability of occipitocervical fixation. Further biomechanical and clinical studies are needed to validate this result.

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.

Biomechanical study of C1 posterior arch crossing screw and C2 lamina screw fixations for atlantoaxial joint instability

BackgroundThe biomechanics of C1 posterior arch screw and C2 vertebral lamina screw techniques has not been well studied, and the biomechanical performance of the constructs cannot be explained only by cadaver testing.MethodsFrom computed tomography images, a nonlinear intact three-dimensional C1-2 finite element model was developed and validated. And on this basis, models for the odontoid fractures and the three posterior internal fixation techniques were developed. The range of motion (ROM) and stress distribution of the implants were analyzed and compared under flexion, extension, lateral bending, and axial rotation.ResultsAll three kinds of fixation techniques completely restricted the range of motion (ROM) at the C1-2 operative level. The C1-2 pedicle screw fixation technique showed lower and stable stress peak on implants. The C1 posterior arch screw + C2 pedicle screw and C1 pedicle screw + C2 lamina screw fixation techniques showed higher stress peaks on implants in extension, lateral bending, and axial rotation.ConclusionsAs asymmetrical fixations, C1 posterior arch screw + C2 pedicle screw and C1 pedicle screw + C2 lamina screw fixations may offer better stability in lateral bending and axial rotation, but symmetrical fixation C1-2 pedicle screw can put the implants in a position of mechanical advantage.

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.

Letter to the Editor Regarding “Proposal of a New Safety Margin for Placement of C2 Pedicle Screws on Computed Tomography Angiography”

Letter to the Editor Regarding “Proposal of a New Safety Margin for Placement of C2 Pedicle Screws on Computed Tomography Angiography”

In Reply to Letter to the Editor Regarding “Proposal of a New Safety Margin for Placement of C2 Pedicle Screws on Computed Tomography Angiography”

In Reply to Letter to the Editor Regarding “Proposal of a New Safety Margin for Placement of C2 Pedicle Screws on Computed Tomography Angiography”

Comparative Analysis of Surgical Outcomes of C1–2 Fusion Spine Surgery between Intraoperative Computed Tomography Image Based Navigation-Guided Operation and Fluoroscopy-Guided Operation

ObjectiveFixation of the C1–2 segment is challenging because of the complex anatomy in the region and the need for a high degree of accuracy to avoid complications. Preoperative 3D-computed tomography (CT) scans can help reduce the risk of complications in the vertebral artery, spinal cord, and nerve roots. However, the patient may be susceptible to injury if the patient’s anatomy does not match the preoperative CT scans. The intraoperative 3D image-based navigation systems have reduced complications in instrument-assisted techniques due to greater accuracy. This study aimed to compare the radiologic outcomes of C1–2 fusion surgery between intraoperative CT image-guided operation and fluoroscopy-guided operation. MethodsWe retrospectively reviewed the radiologic images of 34 patients who underwent C1–2 fusion spine surgery from January 2009 to November 2018 at our hospital. We assessed 17 cases each of degenerative cervical disease and trauma in a study population of 18 males and 16 females. The mean age was 54.8 years. A total of 139 screws were used and the surgical procedures included 68 screws in the C1 lateral mass, 58 screws in C2 pedicle, nine screws in C2 lamina and C2 pars screws, four lateral mass screws in sub-axial level. Of the 34 patients, 19 patients underwent screw insertion using intraoperative mobile CT. Other patients underwent atlantoaxial fusion with a standard fluoroscopy-guided device. ResultsA total of 139 screws were correctly positioned. We analyzed the positions of 135 screws except for the four screws that performed the lateral mass screws in C3 vertebra. Minor screw penetration was observed in seven cases (5.2%), and major pedicle screw penetration was observed in three cases (2.2%). In one case, the malposition of a C2 pedicle screw was confirmed, which was subsequently corrected. There were no complications regarding vertebral artery injury or onset of new neurologic deficits. The screw malposition rate was lower (5.3%) in patients who underwent intraoperative CT-based navigation than that for fluoroscopy-guided cases (10.2%). And we confirmed that the operation time can be significantly reduced by surgery using intraoperative O-arm device. ConclusionSpinal navigation using intraoperative cone-beam CT scans is reliable for posterior fixation in unstable C1-2 pathologies and can be reduced the operative time.

Craniovertebral junction fixation in children less than 5years.

Whilst rigid fixation for craniovertebral instability is the gold standard, in very young, small children conventional management may have to be modified. We present a single-centre experience of craniocervical fixation in children under 5years. A retrospective review of cases that had undergone atlantoaxial (AA) or occipitocervical (OC) fixation aged under 5years. Fusion was assessed using computerised tomography or flexion extension X-rays. Twenty-six children (median age 2.3, range 0.8-4.9years, 19 under the age of 3) underwent OC (n = 19) or AA (n = 7) fusion between 1999 and 2016. Pathology comprised 17 congenital, five trauma, two tumour and two post-infection cases. Twenty-one patients underwent sublaminar cable fixation with calvarial, autologous bone graft and halo-body orthosis immobilisation. An occipital plate and rods to sublaminar wire construct were used in four cases. A rigid instrumented fixation with occipital plate and C2 pedicle screws was utilised in one case. Follow-up was for a median of 2.8years (range 0.03-16.3years). Initial fusion rate was 91%, reaching 100% following two re-operations. Ninety-two per cent of patients were neurologically stable or improved following surgery. Twenty-one patients had a good overall outcome. Two patients had post-operative neurological deteriorations, and four died due to non-procedure related causes. Pin site morbidity secondary to halo use occurred in five cases. High fusion rates with good outcomes are achievable using semi-rigid fixation in the under 5-year-olds. Full thickness, autologous calvarial bone graft secured with wire cables and halo external orthosis offers a safe and effective alternative technique when traditional screw instrumentation is not feasible. These slides can be retrieved under Electronic Supplementary Material.

Utility of intraoperative electromyography in placing C7 pedicle screws.

The C7 vertebral body is morphometrically unique; it represents the transition from the subaxial cervical spine to the upper thoracic spine. It has larger pedicles but relatively small lateral masses compared to other levels of the subaxial cervical spine. Although the biomechanical properties of C7 pedicle screws are superior to those of lateral mass screws, they are rarely placed due to increased risk of neurological injury. Although pedicle screw stimulation has been shown to be safe and effective in determining satisfactory screw placement in the thoracolumbar spine, there are few studies determining its utility in the cervical spine. Thus, the purpose of this study was to determine the feasibility, clinical reliability, and threshold characteristics of intraoperative evoked electromyographic (EMG) stimulation in determining satisfactory pedicle screw placement at C7. The authors retrospectively reviewed a prospectively collected data set. All adult patients who underwent posterior cervical decompression and fusion with placement of C7 pedicle screws at the authors' institution between January 2015 and March 2019 were identified. Demographic, clinical, neurophysiological, operative, and radiographic data were gathered. All patients underwent postoperative CT scanning, and the position of C7 pedicle screws was compared to intraoperative neurophysiological data. Fifty-one consecutive C7 pedicle screws were stimulated and recorded intraoperatively in 25 consecutive patients. Based on EMG findings, 1 patient underwent intraoperative repositioning of a C7 pedicle screw, and 1 underwent removal of a C7 pedicle screw. CT scans demonstrated ideal placement of the C7 pedicle screw in 40 of 43 instances in which EMG stimulation thresholds were > 15 mA. In the remaining 3 cases the trajectories were suboptimal but safe. When the screw stimulation thresholds were between 11 and 15 mA, 5 of 6 screws were suboptimal but safe, and in 1 instance was potentially dangerous. In instances in which the screw stimulated at thresholds ≤ 10 mA, all trajectories were potentially dangerous with neural compression. Ideal C7 pedicle screw position strongly correlated with EMG stimulation thresholds > 15 mA. In instances, in which the screw stimulates at values between 11 and 15 mA, screw trajectory exploration is recommended. Screws with thresholds ≤ 10 mA should always be explored, and possibly repositioned or removed. In conjunction with other techniques, EMG threshold testing is a useful and safe modality in determining appropriate C7 pedicle screw placement.

Biomechanical evaluation of two alternative techniques to the Goel-Harms technique for atlantoaxial fixation: C1 lateral mass-C2 bicortical translaminar screw fixation and C1 lateral mass-C2/3 transarticular screw fixation.

The authors conducted a study to investigate the biomechanical feasibility and stability of C1 lateral mass-C2 bicortical translaminar screw (C1LM-C2TL) fixation, C1 lateral mass-C2/3 transarticular screw (C1LM-C2/3TA) fixation, and C1LM-C2/3TA fixation with transverse cross-links (C1LM-C2/3TACL) as alternative techniques to the Goel-Harms technique (C1 lateral mass-C2 pedicle screw [C1LM-C2PS] fixation) for atlantoaxial fixation. Eight human cadaveric cervical spines (occiput-C7) were tested using an industrial robot. Pure moments that were a maximum of 1.5 Nm were applied in flexion-extension (FE), lateral bending (LB), and axial rotation (AR). The specimens were first tested in the intact state and followed by destabilization (a type II odontoid fracture) and fixation as follows: C1LM-C2PS, C1LM-C2TL, C1LM-C2/3TA, and C1LM-C2/3TACL. For each condition, the authors evaluated the range of motion and neutral zone across C1 and C2 in all directions. Compared with the intact spine, each instrumented spine significantly increased in stability at the C1-2 segment. C1LM-C2TL fixation demonstrated similar stability in FE and LB and greater stability in AR than C1LM-C2PS fixation. C1LM-C2/3TA fixation was equivalent in LB and superior in FE to those of C1LM-C2PS and C1LM-C2TL fixation. During AR, the C1LM-C2/3TA-instrumented spine failed to maintain segmental stability. After adding a cross-link, the rotational stability was significantly increased in the C1LM-C2/3TACL-instrumented spine compared with the C1LM-C2/3TA-instrumented spine. Although inferior to C1LM-C2TL fixation, the C1LM-C2/3TACL-instrumented spine showed equivalent rotational stability to the C1LM-C2PS-instrumented spine. On the basis of our biomechanical study, C1LM-C2TL and C1LM-C2/3TACL fixation resulted in satisfactory atlantoaxial stabilization compared with C1LM-C2PS. Therefore, the authors believe that the C1LM-C2TL and C1LM-C2/3TACL fixation may serve as alternative procedures when the Goel-Harms technique (C1LM-C2PS) is not feasible due to anatomical constraints.

Freehand Placement of the C1 Pedicle Screw Using Direct Visualization of the Pedicle Anatomy and Serial Dilatation.

ObjectiveWe designed a method for inserting C1 pedicle screws using the direct visualization technique of the pedicle and serial dilatation technique to reduce complications and malposition of screw, and assessed the accuracy of this method.MethodsFree-hand C1 pedicle screw insertion using the direct visualization technique of the pedicle and serial dilatation technique was performed on 5 consecutive patients with C1–2 instability at a single institute from March to December 2018. The method involved protecting the vertebral artery (VA) and C1 root using the Penfield No. 1, securing the entry point of the posterior arch screw and the pedicle was visible directly in Trendelenburg position. The hole at the entry point of the C1 posterior arch was serially dilated using a 2.5×3.0 mm drill bit, and the C1 pedicle screw was inserted with the free hand technique. We measured postoperative radiological parameters and recorded intraoperative complications, postoperative neurological deficits and the occurrence of occipital neuralgia. Postoperative computed tomography (CT) was performed to check screw malposition or construction failure.ResultsOf the 10 C1 pedicle screws on postoperative CT, 20% of screws (grade A) were in the ideal position while 80% of screws (grade B) occupied a safe position. Overall, 100% of screws were safe (grade A or B). There were no iatrogenic neurological deficits, VA injury.ConclusionFreehand placement of the C1 pedicle screw through the direct visualization technique of the pedicle and serial dilatation technique is safe and effective without intraoperative fluoroscopy guidance.

Feasibility of mixed reality-based intraoperative three-dimensional image-guided navigation for atlanto-axial pedicle screw placement.

This study aimed to evaluate the safety and accuracy of mixed reality-based intraoperative three-dimensional navigated pedicle screws in three-dimensional printed model of fractured upper cervical spine. A total of 27 cervical model from patients of upper cervical spine fractures formed the study group. All the C1 and C2 pedicle screws were inserted under mixed reality-based intraoperative three-dimensional image-guided navigation system. The accuracy and safety of the pedicle screw placement were evaluated on the basis of postoperative computerized tomography scans. A total of 108 pedicle screws were properly inserted into the cervical three-dimensional models under mixed reality-based navigation, including 54 C1 pedicle screws and 54 C2 pedicle screws. Analysis of the dimensional parameters of each pedicle at C1/C2 level showed no statistically significant differences in the ideal and the actual entry points, inclined angles, and tailed angles. No screw was misplaced outside the pedicle of the three-dimensional printed model, and no ionizing X-ray radiation was used during screw placement under navigation. It is easy and safe to place C1/C2 pedicle screws under MR surgical navigation. Mixed reality-based navigation is feasible within upper cervical spinal fractures with improved safety and accuracy of C1/C2 pedicle screw insertion.

Efficacy and Safety of Atlantoaxial Fluoroscopy-guided Pedicle Screw Fixation in Patients Younger Than 12 Years: A Radiographic and Clinical Assessment.

A retrospective clinical study. The aim of this study was to evaluate the efficacy and safety of fluoroscopy-guided atlantoaxial pedicle screw fixation in patients younger than 12 years. C1-C2 pedicle screw fixation is a widely accepted treatment method for atlantoaxial dislocation (AAD). However, data regarding its use for atlantoaxial fusion (AAF) in children are limited. Thirty-six consecutive patients younger than 12 years underwent C1-C2 pedicle screw fixation for AAD between 2007 and 2017. Anatomical parameters of the C1 pedicle were measured on preoperative computed tomography (CT). Accuracy of pedicle screw fixation was assessed on postoperative CT using the following definitions: Type I, screw threads completely within the bone; Type II, less than half the diameter of the screw violating the surrounding cortex; and Type III, clear violation of the transverse foramen or spinal canal. Demographic, surgical, radiation dose, and clinical data were recorded. Patients underwent 144 screw fixations (67 C1 pedicle screws, 68 C2 pedicle screws, 5 C1 lateral mass screws, and 4 C-2 laminar screws) for a variety of pediatric AADs, with 36.5 ± 8.5 months of follow-up. Among the 135 pedicle screws, 96.3% were deemed "safe" (Type I or II) and 80.7% (109/135) of the screws were rated as being ideal (Type I); five screws (3.7%) were identified as unacceptable (Type III). Average estimated blood loss (EBL) was 92 mL, and the average total radiation exposure during the operation was 6.2 mGy (in the final 26 cases). There were no neurovascular injuries. All patients showed radiographic stability and symptom resolution. C1-C2 pedicle screw fixation under fluoroscopy is safe and effective for the treatment of AAD in children younger than 12 years. However, it may be technically challenging owing to the special anatomical features of children and should be performed by experienced surgeons. 3.

The Effect of Straight or Lordotic Rods on Cervical Subaxial Alignment While Fusing C1-C2

The C1 lateral mass and C2 pedicle screw with rod fixation system has been used commonly in recent years. Despite the numerous reports on this technique in the literature, there are no studies regarding the effect of the angle of the rod used. We investigated the effect of rod angle on subaxial lordosis, cervical sagittal balance, and pain scores. Clinical records and radiologic images of 58 patients who underwent procedures between 2011 and 2016 at our clinic were assessed retrospectively. We recorded clinical findings, visual analog scale (VAS) scores, angles of cervical and segmental lordosis, and the distance between the C2 sagittal vertical axis (SVA) and the C7 posterior-superior corner. A total of 36 male and 22 female patients were enrolled. A negative correlation was found between the C1-C2 lordosis angle and the C2-C7 lordosis angle irrespective of surgical technique. In patients who were operated on using 30°-angled rods, there was a postoperative increase in C1-C2 lordosis degree and an improvement in C2 cervical SVA values. Postoperative month 6 VAS scores were significantly better in the patients who were operated on with angled rods compared with those who received straight rods. We believe this is because of the positive effect of the angled rod on sagittal balance. Nevertheless, prospective case-control studies should be conducted with larger groups of subjects. Furthermore, every patient should be evaluated considering the whole spinal sagittal balance.