Atlantoaxial Pedicle Screw Research Articles

Mazor X robot-assisted upper and lower cervical pedicle screw fixation: a case report and literature review

BackgroundManual placement of cervical pedicle screws is risky, and robot-assisted placement of atlantoaxial pedicle screws has not been reported.Case reportWe describe a 74-year-old female patient with atlantoaxial fracture and dislocation combined with spinal cord injury caused by a car accident. The left lower limb muscle strength was grade 0, the right upper limb muscle strength was grade 1, and the right lower limb muscle strength was grade 2. Loss of sensation below the clavicle level, decreased superficial sensation in the extremities, loss of deep sensation in the left lower extremity, and incontinence were observed. We successfully placed atlas pedicle screws with the assistance of the Mazor X robot. One week after the operation, radiological imaging revealed that the reduction effect was good, the placement of the pedicle screws was satisfactory, the left upper limb and left lower limb muscle strength was level 2, the right upper limb and the muscle strength of the right lower limb were grade 3, and the sensory function was partially restored. No complications related to screw placement were found at the 3-month postoperative follow-up.ConclusionsMazor X robot-assisted descending pedicle screw fixation of the atlas is feasible and safe.

Comparative study of computer-assisted and robot-assisted atlantoaxial pedicle screw implantation for reversible atlantoaxial dislocation

To investigate the effectiveness of computer-assisted and robot-assisted atlantoaxial pedicle screw implantation for the treatment of reversible atlantoaxial dislocation (AAD). The clinical data of 42 patients with reversible AAD admitted between January 2020 and June 2023 and met the selection criteria were retrospectively analyzed, of whom 23 patients were treated with computer-assisted surgery (computer group) and 19 patients were treated with Mazor X spinal robot-assisted surgery (robot group). There was no significant difference in gender, age, T value of bone mineral density, body mass index, etiology, and preoperative Japanese Orthopaedic Association (JOA) score, Neck Dysfunction Index (NDI) between the two groups ( P>0.05). The operation time, screw implantation time, intraoperative blood loss, hand and wrist radiation exposure, and complications were recorded and compared between the two groups. Gertzbein classification was used to evaluate the accuracy of screw implantation. JOA score and NDI were used to evaluate the function before operation, at 3 days after operation, and at last follow-up. At last follow-up, the status of screws and bone fusion were observed by neck three-dimensional CT. The operation time and hand and wrist radiation exposure of the computer group were significantly longer than those of the robot group ( P<0.05), and there was no significant difference in the screw implantation time and intraoperative blood loss between the two groups ( P>0.05). All patients were followed up 11-24 months, with an average of 19.6 months. There was no significant difference in the follow-up time between the two groups ( P>0.05). There was no significant difference in the accuracy of screw implantation between the two groups ( P>0.05). Except for 1 case of incision infection in the computer group, which improved after antibiotic treatment, there was no complication such as nerve and vertebral artery injury, screw loosening, or breakage in the two groups. The JOA score and NDI significantly improved in both groups at 3 days after operation and at last follow-up ( P<0.05) compared to those before operation, but there was no significant difference between the two groups ( P>0.05). At last follow-up, 21 patients (91.3%) in the computer group and 18 patients (94.7%) in the robot group achieved satisfactory atlantoaxial fusion, and there was no significant difference in the fusion rate between the two groups ( P>0.05). Computer-assisted or robot-assisted atlantoaxial pedicle screw implantation is safe and effective, and robotic navigation shortens operation time and reduces radiation exposure.

Effect of a new type of head and neck fixation and traction device in the surgical treatment of patients with irreducible atlantoaxial dislocation

BackgroundIn order to improve the clinical medical technology, enhance the clinical effect and improve the disease detection rate, the clinical incidence rate of atlantoaxial dislocation and vertebral body malformation that are difficult to summarize is increasing year by year.MethodsA total of 80 patients with atlantoaxial dislocation deformity treated in our hospital from January 2017 to May 2021 are selected for this study. According to the number table method, 80 patients are randomly divided into the auxiliary group and the traditional group, with 40 cases in each group. The traditional group is treated with posterior atlantoaxial pedicle screw system internal fixation and intervertebral fusion, and the auxiliary implementation and application of a new head and neck fixation and traction device through nasal cannula and oral release decompression fixation for posterior fusion. The patients in the two groups are compared changes and differences in efficacy, spinal cord function index, pain score, surgery, and quality of life.ResultsCompared with the traditional group, the total clinical effective rate, cervical spine extension and flexion range of motion, physical function, physical function, psychological function, and social function in the auxiliary group are significantly improved. The operation time, intraoperative blood loss, and VAS score are significantly reduced (P < 0.05).ConclusionThe new head and neck fixation traction device can improve the surgical efficacy and quality of life of patients with irreversible atlantoaxial dislocation, enhance spinal cord function, reduce pain symptoms and surgical risks, and is worthy of clinical application.

Individualized 3D printed navigation template-assisted atlantoaxial pedicle screws vs. free-hand screws for the treatment of upper cervical fractures.

ObjectiveThis study aims to compare the efficacy and safety of freehand atlantoaxial pedicle screws against custom 3D printed navigation template screws in the treatment of upper cervical fractures.MethodsIn our institution from 2010 to 2020, a retrospective cohort analysis of 23 patients with upper cervical fractures was done. These patients were separated into two groups: group A (N = 12), which received customized 3D printed navigation template-assisted screws with virtual reality techniques, and group B (N = 11), which received freehand screws assisted by intraoperative fluoroscopy. Every patient was monitored for more than 1 year. The two groups were contrasted in terms of screw implant accuracy, cervical spine Japanese Orthopaedic Association (JOA) score, American Spinal Injury Association (ASIA) score, visual analogue scale (VAS) score, surgical time, fluoroscopy times, and intraoperative blood loss.ResultsA total of 88 atlantoaxial pedicle screws in all, 46 in group A and 42 in group B, were implanted. In group A, the screw insertion accuracy rate was 95.7%, compared to 80.0% in group B (P < 0.05). When compared to group B, group A had shorter surgery times, less blood loss, fewer fluoroscopies, a higher short-term JOA score, and overt pain reduction (P < 0.05). However, there was no discernible difference between the two groups' VAS scores, long-term JOA scores, or ASIA scores (sensory and motor), at the most recent follow-up.ConclusionIndividualized 3D printed guide leads to significant improvement in the screw safety, efficacy, and accuracy, which may be a promising strategy for the treatment of upper cervical fractures.

Biomechanical analysis of atlantoaxial intraarticular fusion cages with posterior pedicle screws fixation using finite element method

BackgroundCadaveric biomechanical studies indicated that atlantoaxial intraarticular fusion cages with posterior pedicle screws fixation could increase the multi-axial rigidity. However, the stress distribution of the fixation construct is still unclear. MethodsFrom computed tomography images, a nonlinear intact three-dimensional C0–2 finite element model was developed and validated. Four finite element models were reconstructed: intact model, unstable model, bilateral atlantoaxial pedicle screws combined bilateral cages model, bilateral atlantoaxial pedicle screws model. The range of motion and maximum von Mises stresses were compared under flexion, extension, lateral bending, and axial rotation. FindingsCompared with unstable model, both bilateral atlantoaxial pedicle screws combined bilateral cages model and bilateral atlantoaxial pedicle screws model fixation techniques reduced range of motion by >99% in extension, flexion, lateral bending and axial rotation. For bilateral atlantoaxial pedicle screws combined bilateral cages model, the maximum von Mises stress was in the base of the C2 screw head site. In the bilateral atlantoaxial pedicle screws model was stressed at the rod linked C1 and C2 screws. Compared with bilateral atlantoaxial pedicle screws model, bilateral atlantoaxial pedicle screws combined bilateral cages model reduced the maximum von Mises stress on the implants by >90% in extension, flexion, lateral bending and axial rotation. InterpretationThe finite element model study indicated that, compared with posterior C1-C2 pedicle screws fixation, atlantoaxial intraarticular fusion cages with posterior pedicle screws fixation could not only significantly restore stability to the atlantoaxial junction, but also dramatically reduce the maximum von Mises stress in the C1-C2 pedicle screws.

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.

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.

267. One stage atlantoaxial pedicle screw fixation for unstable atlas burst fracture

BACKGROUND CONTEXT Treatment of unstable atlas fracture is controversial. Some studies showed external fixation could achieve good clinical effect. Some showed internal fixation could get initial stability and perfect reduction. PURPOSE To assess the clinical results of one stage the posterior atlantoaxial pedicle screw fixation and fusion for unstable atlas burst fracture combined with atlantoaxial instability. STUDY DESIGN/SETTING A retrospective study. PATIENT SAMPLE Twenty-eight (9 females, 19 males) patients with an average age of 41.8 (22-59) years between May 2016 and December 2018 were studied. OUTCOME MEASURES The preoperative atlanto-dens interval (ADI) and lateral mass distance (LMD) were measured. All patients were assessed clinically for neurologic recovery, atlantoaxial reduction and bone graft fusion. METHODS Twenty-eight (9 females, 19 males) patients with an average age of 41.8 (range, 22-59) years between May 2010 and December2012 were studied. The patients had various degrees of occipital neck pain, limited mobility and associated with neurological dysfunction. Degree C in 1 case and degree D in 5 cases were assessed by the ASIA impairment scale. The preoperative atlanto-dens interval (ADI) and lateral mass distance (LMD) were measured. Patients were treated with posterior atlantoaxial pedicle screw fixation and fusion. All patients were assessed clinically for neurologic recovery, atlantoaxial reduction and bone graft fusion. RESULTS All 28 patients were followed up for an average of 15.6 months (range, 10-24 months). No intraoperative vertebral artery injury and spinal cord injury were noted. Postoperative cervical spine x-ray and CT showed that the sagittal cervical spine alignment was restored and no spinal cord compression was found. At last follow-up, solid bony fusion was achieved in all patients with no loosening, displacement, instability or breakage of the screws. All patients except 1 were substantially improved neurological status. At last follow-up the ADI and LMD were statistically significant difference between pre- and postoperation. CONCLUSIONS The posterior atlantoaxial pedicle screw instead of occipitocervical fusion for unstable atlas burst fracture combined with atlantoaxial instability seems to be effective, but it is technically demanding to place screw into the lateral mass of the atlas. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Suboccipital neuralgia after C1 pedicle screw insertion: do we neglect atlantooccipital joint violation? - Case report and literature review

BackgroundOccipital neuralgia is one of the postoperative complications of C1 lateral mass screw insertion, which was deemed to be related with the C2 nerve root dysfunction.Case presentationA 52-year-old female patient presented with gradually progressive numbness and weakness in her extremities for 6 months. X-ray and computed tomography (CT) scan revealed obvious anterior atlantoaxial dislocation (ADD), which was reducible on extensive view. Atlantoaxial pedicle screw fixation and bone graft was performed. Immediately after the operation, the neurological symptom significantly improved. The patient complained of restricted cervical rotation and suboccipital neuralgia which was exacerbated by rotation with an intensity of 7 on a visual analog scale (VAS) ranging from 0 to 10 at postoperative day 5. While a satisfactory reduction was detected in the postoperative CT, violation of the left atlantooccipital joint was observed in the left C1 screw. Nimesulide (daily dosage of 0.2 g) and bracing were recommended immediately. At the 2 month follow-up, both the neurological improvement and reduction were maintained. The VAS of suboccipital neuralgia is 3 and decreased to 1 at 6 months postoperative. Bony fusion of the left atlantooccipital joint was confirmed by CT scan at 6 months postoperative. The patient complained that the suboccipital neuralgia was tolerable without the assistance of braces or medications for pain. At the 18 month follow-up, only stiffness of head flexion and rotation was observed without suboccipital neuralgia.ConclusionSuboccipital neuralgia after atlantooccipital joint violation of C1 pedicle screw placement most likely results from C1 nerve root irritation. As the corresponding dermatome differs from the distributing region and aggravated factor of C2 nerve root dysfunction, neuralgia due to C1 irritation was only localized at suboccipital region and exacerbated by rotation.

Injury to upper cervical spine treated by posterior internal fixation without bone graft fusion

Objective To investigate the clinical efficacy of treating injury to the upper cervical spine with posterior internal fixation without bone graft fusion. Methods Included in this retrospective study were 35 patients with upper cervical injury who had been treated at Department of Orthopedics, The Second Affiliated Hospital to Soochow University from June 2010 to August 2017. They were 21 males and 14 females with an average age of 44.1 years (from 26 to 56 years). They were all treated firstly by posterior occipitocervical internal fixation or internal fixation with atlantoaxial pedicle screws without bone graft fusion. The internal fixation was then removed after a solid bone union was confirmed by X-ray. The scores of Japanese Orthopedic Association (JOA), visual analogue scale (VAS), Neck disability index (NDI) and neck stiffness were used to evaluate the functional recovery of the upper cervical spine. We also observed the rotational range of the upper cervical spine using functional CT scan of C1-C2. Results All the pedicle screws were successfully implanted after satisfactory intraoperative reduction, leading to no injury to the vertebral artery or spinal cord. All patients were followed up for an average of 18.1 months (from 7 to 28 months). At preoperation, post-implantation and final follow-up, the JOA scores were 6.5±1.4, 7.7±1.5 and 16.1±0.8 points, the VAS scores 6.1±1.6, 2.8±0.8 and 1.1±0.9 points, and the NDI scores 37.9±2.6, 20.3±3.8 and 3.7±1.7 points, showing significant improvements after internal fixation and after removal of internal fixation (P<0.05). Serious neck stiffness was observed in none of the 35 patients, mild neck stiffness in 12 patients and freedom from neck stiffness in 23 patients. The postoperative radiological analysis revealed fine fracture reduction and bony union in all. After 6 to 12 months the rotation of upper cervical spine was obviously improved and the left-to-right range of rotation of C1-C2 was 35.4°±2.6° as revealed by functional CT scan. Conclusion For the middle aged and young patients with new injury to the upper cervical spine, the posterior occipitocervical internal fixation or internal fixation with atlantoaxial pedicle screws can be performed without bone graft fusion at the first stage and removal of internal fixation can be done at the second stage so that the atlantoaxial rotation can be preserved to ensure satisfactory clinical efficacy while bone union can be also ensured and pain reduced. Key words: Cervical spine; Wounds and injuries; Bone nails; Posterior fixation; Non-fusion

Design and basic research on accuracy of a novel individualized three-dimensional printed navigation template in atlantoaxial pedicle screw placement.

ObjectiveTo design and evaluate the accuracy of a novel navigation template suitable for posterior cervical screw placement surgery by using 3D printing technology to improve the existing guiding template design.MethodsThe researchers (including spine surgeons and technicians) used CT to perform thin-slice scanning on 12 cases of normal upper cervical vertebral specimens and defined the screw channels that were completely located in the pedicle without penetrating the cortex as ideal screw channels, then designed the ideal channel of the upper cervical vertebral (atlantoaxial) pedicle screw by computer software which was regarded as the preset values, and recorded the screw entrance point, transverse angle and sagittal angle of the ideal channel. Then, researchers designed the novel navigation templates for placement pedicle screw according to the ideal screw channel preset values and manufactured them with one for every single vertebra by 3D printer. A senior spine surgeon performed the posterior surgery to implant pedicle screw on the specimens by the novel navigation templates, then performed CT thin-slice scanning on the specimens again after removing the screws, and reconstructed the actual screws channel by computer software, recorded the screw entrance point, transverse angle and sagittal angle of the actual channels which were defined as the actual values and evaluated them according to Kawaguchi’s pedicle screw evaluation standard finally. The differences between the preoperative preset values of ideal screw channel and the postoperative actual values of actual screw channel were compared by a nonparametric paired rank test.Results48 screws were placed on 12 cases of upper cervical vertebral specimens in total. It showed that the grade 0, I, II, III channels in this study were 47, 1, 0, 0, respectively. The grade 0 channels accounted for 97.92% of the total number of channels. There was no significant difference with regard to the screw entrance point, the transverse angle, and the sagittal angle between the preoperative preset values of ideal screw channels and the postoperative actual values of actual screw channels.ConclusionTo implant pedicle screw assisted with the novel individually navigation template designed by 3D printed in the posterior cervical surgery can improve accuracy of pedicle screw placement and safety of the surgery.

Clinical Application and Efficacy Analysis of 3D Navigation Module in the Treatment of Atlantoaxial Instability

Background: Posterior cervical atlantoaxial pedicle screw fixation is a very effective treatment for atlantoaxial instability (AAI). However, due to the complex anatomy of the cranial-cervical junction, the accuracy and safety of posterior atlantoaxial pedicle screw placement remains extremely challenging. Objective: To quantitatively evaluate the safety and accuracy of the 3D navigation module to assist the posterior atlantoaxial fixation. Methods: A total of 20 AAI patients were selected between June 2014 and September 2015. The Mimics v10.1 and 3-matic software were used. The 3D navigation module was designed as a double-sided positioning hole guide with a guide rod. All patients underwent posterior atlantoaxial posterior pedicle screw fixation with 3D navigation module. The actual entry point and screw trajectory were measured after operation, which were compared with the ideal entry point and screw trajectory. The Japanese Orthopaedic Association (JOA) score was measured before and after surgery to evaluate the neurological function improvement. The average operation time, blood loss, and frequency of intraoperative fluoroscopy were counted. Results: The posterior atlantoaxial pedicle screw fixation with a 3D navigation module was successfully performed in all patients. A total of 80 atlantoaxial pedicle screws were implanted in the 20 patients. Postoperative CT scan showed that two pedicle screws deviated from the medial aspect of the atlas pedicle cortex and entered the spinal canal approximately 1 mm, without causing neurological complications. There was no significant difference between the ideal and actual entry points or ideal and actual screw trajectories of the atlas and axis (P &gt; 0.05). The preoperative JOA score was 12.45 ± 1.15 and postoperative JOA score was 15.5 ± 0.89, with statistically significant difference (P &lt; 0.05). Conclusion: It was safe and effective to use the 3D navigation module to assist the posterior atlantoaxial pedicle insertion, with a high accuracy of pedicle screw placement. Keywords: atlantoaxial instability, pedicle screw, 3D navigation module, rapid prototyping

Clinical analysis of pedicle screw fixation in the treatment of type II odontoid fracture with bone grafting and non-bone grafting

Objective To explore the clinical efficacy of bone grafting in the treatment of type Ⅱ odontoid fracture with pedicle screw fixation. Methods Of 14 cases with type Ⅱ odontoid fractures, 8 patients in group A received pedicle screw, lamina autologous bone grafts, 6 cases of group B received simple posterior pedicle screw fixation.The operative time, the amount of surgical bleeding and the postoperative cervical spine flexion and rotation were observed at 3 months postoperatively, and the patients were followed up for 5-45 months. Results All patients were followed up for 5-45 months, with an average of 26.5 months.The operation time was (1.83±0.5)h in the bone graft group, and (1.58±0.9)h in the non-bone graft group, the difference was statistically significant (t=2.842, P>0.05). The blood loss of the bone graft group was (150±16)mL, which of the non-bone graft group was (120±14)mL, the difference between the two groups was statistically significant (t=3.57, P>0.05). After 3 months, the flexion of the cervical spine of the bone graft group was (31.2±4.6)°, which in the non-grafted group was (32.3±5.7)°, the difference was statistically significant (t=0.675, P<0.05). The rotation of the bone graft group was (40.6±4.5)°, which in the non-graft group was (41.3±3.5)°, the difference was statistically significant (t=0.278, P<0.05). Both two groups had no vertebral artery and spinal cord injury, wound healing.During the follow-up period, the two groups of patients had a good reduction of cervical spine, no internal fixation lossening, fracture, fracture healing well, group A bone graft fusion. Conclusion For this type of fracture, simple atlantoaxial pedicle screw fixation compared with autologous iliac bone graft fusion treatment, can save the operation time, reduce the amount of bleeding. Key words: Fracture, bone; Pedicle screw; Cervical vertebrae

Long-Term Influence of C1-C2 Pedicle Screw Fixation on Occipitoatlantal Angle and Subaxial Cervical Spine in the Pediatric Population

Objective: The goal of this study was to evaluate the impact of C₁-C₂ pedicle screw fixation on the occipitoatlantal angle and subaxial cervical spine for a pediatric population, and the clinical efficacy and adjacent-segment degeneration after C₁-C₂ pedicle screw fixation with a minimum of 2 years of follow-up. Methods: Twenty-two pediatric patients with atlantoaxial dislocation who were enrolled in this study underwent atlantoaxial pedicle screw fixation. The correlation between C₀-C₁, C₂-C₇, and C₁-C₂ pre- and postoperative sagittal angles was assessed using plain radiographs, and adjacent-segment degeneration (ASD) and JOA scores (Japanese Orthopaedic Association scores) were evaluated after atlantoaxial pedicle screw fixation. Results: The C₁-C₂ angle increased from 16.1 ± 13.37 to 28.1 ± 5.1° (p < 0.01). The pre- and postoperative C₁-C₂ angles were negatively correlated with the pre- and postoperative C₀-C₁ and C₂-C₇ angles, respectively. In accordance with the optimal atlantoaxial fusion angle (25-30°) obtained from the literature, postoperative JOA scores were greater in the groups with angles of more than 30° and less than 25°, although the difference in ASD was not statistically significant. Postoperative JOA scores were not relevant to the postoperative C₁-C₂ angle; however, there was a positive correlation between JOA improvement rate and the change of the C₁-C₂ angle postoperatively. Conclusion: Atlantoaxial pedicle screw fixation can be used easily to reduce atlantoaxial dislocation in the pediatric population; however, outside the range of the optimal atlantoaxial fusion angle it can change the occipitoatlantal angle and subaxial alignment, which induces ASD and influences the clinical efficacy. It is necessary to achieve an optimal atlantoaxial angle when using atlantoaxial pedicle screw fixation.

Clinical Application of Atlantoaxial Pedicle Screw Placement Assisted by a Modified 3D-Printed Navigation Template

OBJECTIVES:To investigate the primary clinical value of atlantoaxial pedicle screw placement assisted by a modified 3D-printed navigation template.METHODS:We retrospectively analyzed the cases of 17 patients treated from June 2015 to September 2016 with atlantoaxial pedicle screw placement assisted by a modified 3D-printed navigation template. All procedures were performed prior to surgery, including thin-slice CT scanning, medical image sampling and computerized 3D modeling of the atlantoaxial joint, optimal pedicle screw trajectory determination, and anatomical trait acquisition for the atlantoaxial pedicle, spinous process of the axis, vertebral lamina and posterior lateral mass, and design of a reverse template. During surgery, a navigation template was tightly attached to the atlantoaxial joint to assist in pedicle screw placement. Surgeons subsequently used an electric drill to remove the template through a guide channel and then placed the atlantoaxial pedicle screw. Observed indexes included the VAS score, JOA improvement rate, surgery duration, and blood loss.RESULTS:Surgery was successful in all 17 patients, with an average operation duration of 106±25 min and an average blood loss of 220±125 ml. Three days postoperatively, the VAS score decreased from 6.42±2.21 to 3.15±1.26. Six months postoperatively, the score decreased to 2.05±1.56. The postoperative JOA score increased significantly from 7.68±2.51 to 11.65±2.72 3 d after surgery and to 13.65±2.57 after 6 months. Sixty-eight pedicle screws were inserted successfully, with 34 in the atlas and 34 in the axis. According to the Kawaguchi standard, 66 screws were in grade 0 (97.06%), and 2 were in grade 1 (2.94%). The pre- and postoperative transverse and sagittal screw angles showed no significant differences.CONCLUSIONS:Atlantoaxial pedicle screw placement assisted by a modified 3D-printed navigation template is worth recommending due to the improved accuracy in screw placement, improved patient safety and beneficial clinical effects.

Research on application of advanced 3D printing navigation templates in assisting placement of atlantoaxial pedicle screw

Objective To explore the accuracy and clinical efficacy of advanced 3D printing navigation templates in assisting placement of atlantoaxial pedicle screw. Methods A retrospective analysis was carried out on 49 cases of patients with atlanto-axial vertebral fractures and dislocations between June 2013 and June 2016, and all of them were given posterior incision, reduction and internal fixation of atlantoaxial pedicle screw. The patients were divided into advanced 3D printing navigation template group (14 cases), early 3D printing navigation template group (16 cases), and routine pedicle screw placement group (19 cases). Atlantoaxial CT data of patients in advanced 3D printing navigation template group and early 3D printing navigation template group were input into Mimics 17.0, then advanced 3D printing navigation template group and early 3D printing navigation which were used in clinic surgery were designed and printed. The relationship between positions of pedicle screw with the pedicle and bone cortex in plain CT image was observed after operation. The quality of the screw position was assessed and the accuracy of three kinds of screwing methods was compared. The accuracy of the screwing angle was assessed by comparing with the differences between the preoperative designed channel inclination angle and postoperative actual screwing angle. Three groups were compared for differences between operation time, intraoperative blood loss, and scores of cervical nerve scale and visual analogue scale (VAS) of neck and shoulder pain by Japanese Orthopaedic Association (JOA). Results All 49 cases of patients successfully completed the surgery. Patients of the routine pedicle screw placement group, early 3D group and advanced 3D group correspond operation time for 141.2±20.7 min, 112.5±12.1 min and 103.1±10.4 min, intraoperative blood loss for 314.0±81.4 ml, 243.6±71.2 ml and 181.0+59.1 ml; total accuracy of screwing for 75.0%(54/72), 93.75%(60/64) and 96.43%(54/56). There were statistically significant differences among the routine group, 3D group and advanced 3D group in the mentioned programs. There were no statistical differences between advanced 3D group and 3D group in the inclination angle and head tilt angle with the pre-designed values, while there was statistically significant difference between the routine group and the pre-designed value. The accuracy of the inclination angle and head tilt angle screwing angle were obviously superior in the advanced 3D group and early 3D group to that of the routine group. There were statistically significant differences between preoperative with postoperative VAS scores and JOA scores in the same group, while there were no statistically significant differences among groups in JOA. But there was statistically significant difference between the routine group and the advanced 3D in VAS, and there was no statistically significant difference between the routine pedicle screw placement group and the early 3D in VAS. All three groups of patients had bony fusion of atlanto-axial vertebral body, without loosening, dislocation and fracture of the internal fixators. Conclusion Advanced 3D printing templates in assisting the surgical treatment for atlantoaxial fracture and dislocation can improve the accuracy of pedicle screwing and safety of the surgery, reduce the surgery risk, and obtain satisfied clinical curative effects. Key words: Cervical atlas; Axis; Spinal fusion; Bone screws; Surgery, computer-assisted

Design and Application of a Novel Patient-Specific Three-Dimensional Printed Drill Navigational Guiding in Atlantoaxial Pedicle Screw Placement.

To explore accuracy and clinical efficacy of a novel patient-specific three-dimensional (3D) printed drill navigational guiding template in atlantoaxial pedicle screw placement. A retrospective analysis of 49 patients with atlantoaxial vertebral fractures and dislocations was performed. Patients were divided into a 3D printed navigational guiding template group (n= 25) and traditional group (n= 14). Safety of screw position was assessed, and accuracy of 2 screw placement methods was compared. Accuracy of screw placement was assessed by comparing differences between preoperative designed channel transverse angle and postoperative actual screw placement angle. Two groups were compared to find differences between operative time, intraoperative blood loss, screw placement time, number of fluoroscopy examinations, visual analog scale score, and Japanese Orthopaedic Association score. There were statistically significant differences between the guiding template group and traditional group in operative time, intraoperative blood loss, screw placement time, and number of fluoroscopy examinations. No statistically significant differences were found between groups in transverse and sagittal angles with ideal values. There were statistically significant differences between preoperative and 1-week, 1-month, 3-month, 6-month, and 1-year postoperative visual analog scale and Japanese Orthopaedic Association scores in the same group, whereas there were no statistically significant differences between the groups. Use of the novel patient-specific 3D printed drill navigational guiding template in surgical treatment of atlantoaxial fracture and dislocation can improve accuracy of pedicle screw placement and safety of the surgery, can reduce surgical risks, and can obtain satisfactory clinical curative effects.

C1-C2 Pedicle Screw Fixation for Pediatric Atlantoaxial Dislocation: Initial Results and Long-term Follow-up.

There are few studies reporting the use of atlantoaxial pedicle screws and the long-term effects of C1-C2 posterior fusion in children. Our study is to investigate the initial results of C1-C2 pedicle screw fixation for pediatric atlantoaxial dislocation (AAD) and assessed spontaneous change of postoperative radiography after a long-term follow-up period. Posterior pedicle screw fixations were performed in 21 pediatric patients with AAD. All the patients underwent implant removal 1 year after their initial surgery and had regular follow-up with an average duration of 76.4 months (range, 52 to 117 mo). Clinical and radiographic data were then collected and compared. Frankel Grade was significantly improved at 3 months follow-up compared with pretreatment values. All patients had good bony fusion at a mean of 4.2±0.9 months (range, 3 to 6 mo) after treatment. None of the patients experienced worsening neurological symptoms or injury to the vertebral artery. However, 2 cases experienced minor complications. Following removal of the implants, no spinal deformities or subaxial instabilities were found. The mean angle of sagittal curvature increased from 12.1±2.4 degrees (range, 0 to 22 degrees) immediately postoperatively to 19.1±2.7 degrees (range, 6 to 31 degrees) at the final follow-up (P>0.05). The results demonstrated that C1-C2 pedicle screw fixation could achieve satisfactory initial results for the management of the pediatric AAD. Moreover, removal of the metal implant after bony fusion did not increase the risk of spinal deformity or subaxial instability at long-term follow-up.

A Modified Personalized Image-Based Drill Guide Template for Atlantoaxial Pedicle Screw Placement: A Clinical Study

BackgroundAtlantoaxial posterior pedicle screw fixation has been widely used for treatment of atlantoaxial instability (AAI). However, precise and safe insertion of atlantoaxial pedicle screws remains challenging. This study presents a modified drill guide template based on a previous template for atlantoaxial pedicle screw placement.Material/MethodsOur study included 54 patients (34 males and 20 females) with AAI. All the patients underwent posterior atlantoaxial pedicle screw fixation: 25 patients underwent surgery with the use of a modified drill guide template (template group) and 29 patients underwent surgery via the conventional method (conventional group). In the template group, a modified drill guide template was designed for each patient. The modified drill guide template and intraoperative fluoroscopy were used for surgery in the template group, while only intraoperative fluoroscopy was used in the conventional group.ResultsOf the 54 patients, 52 (96.3%) completed the follow-up for more than 12 months. The template group had significantly lower intraoperative fluoroscopy frequency (p<0.001) and higher accuracy of screw insertion (p=0.045) than the conventional group. There were no significant differences in surgical duration, intraoperative blood loss, or improvement of neurological function between the 2 groups (p>0.05).ConclusionsBased on the results of this study, it is feasible to use the modified drill guide template for atlantoaxial pedicle screw placement. Using the template can significantly lower the screw malposition rate and the frequency of intraoperative fluoroscopy.