Treating Pediatric Irreducible Atlantoaxial Rotatory Fixation (IAARF) by Unlocking Facet Joint Through Transoral Approach and Fixing With Slim-TARP Plate (15 Cases Series).

BACKGROUND: Irreducible atlantoaxial rotatory fixation (IAARF) often requires surgical treatment. Transoral unlocking the facet joints is a key measure for the treatment of IAARF. We investigate a novel method for treating pediatric IAARF by unlocking facet joint through transoral appraoch and fixed with slim-tarp plate in same stage with same approach. OBJECTIVE: The objective of this study is to investigate the method and efficacy of a unique transoral approach to unlock facet joints and fixation with slim-shaped transoral anterior reduction plate (slim-TARP) plate in the treatment of IAARF. METHODS: Fifteen patients diagnosed with AARF were transferred to our hospital. After 1 week of bidirectional cervical cranial traction, they were diagnosed with irreducible AARF that, and then underwent transoral release and fixation with slim-TARP plate procedures. Postoperative computed tomography and magnetic resonance were used to evaluate the reduction effect, bone fusion, and fusion time. Japanese orthopaedic association scores were used to compare the recovery of spinal cord function in patients before and after surgery. Complications such as wound infection, neurovascular injury, and loosening of internal fixation were evaluated too. RESULTS: All 15 patients underwent transoral unlocking facet joint and fixation with slim-TARP procedures smoothly. The operation time were 129.2±11.9 minutes, blood loose were 83±23 mL. There were no neurological injury, wound infections, verified or suspected vertebral artery injury, etc. All patients were followed up for a mean of 17.8±6.6 months (range: 12 to 36 mo). Bony fusion was achieved in all patients. Mean fusion time was 3.6±1.2 months (range: 3 to 6 mo). Complete correction of torticollis was achieved in all 15 cases. Preoperative symptoms of neck pain and limitation of neck movement were effectively alleviated at 3 months after surgery. The 3 patients with preoperative neurological deficits had significant relief after surgery, and their latest follow-up results showed that their Japanese orthopaedic association scores increased from 13.0±1.0 to 16.3±0.6. CONCLUSIONS: Transoral release and fixation with slim-TARP plate by transoral approach is a feasible and safe method for treating pediatric irreducible atlantoaxial rotatory fixation.

Treatment of irreducible atlantoaxial dislocation by bony deformity osteotomy, remodeling, releasing, and plate fixating through transoral approach.

OBJECTIVE: Investigate a novel method for treating irreducible atlantoaxial dislocation (IAAD) or with basilar invagination (BI) by bony deformity osteotomy, remodeling, releasing, and plate fixating through transoral approach. METHOD: From March 2015 to December 2019, 213 consecutive patients diagnosed as IAAD/BI were treated with transoral bony deformity remodeling and releasing combined with plate fixation. The main clinical symptoms include neck pain, headache, numbness of the limbs, weakness, unstable walking, inflexible hand-held objects, and sphincter dysfunction. The bony factors that impact reduction were divided into as follows: type A1 (sloping of upper facet joint in C2), type A2 (osteophyte in lateral mass joints between C1 and C2), type A3 (ball-and-socket deformity of lateral mass joint), type A4 (vertical interlocking between lateral mass joints of C1-C2), type A5 (regional bone fusion in lateral mass joints), type B1 (bony factor hindering reduction between the atlas-dens gap), type B2 (uncinate odontoid deformity), and type B3 (hypertrophic odontoid deformity). All of them were treated with bony deformity osteotomy, remodeling, and releasing techs. RESULT: The operation time was 144 [Formula: see text] 25 min with blood loss of 102 [Formula: see text] 35 ml. The average pre-operative ADI improved from 7.5 [Formula: see text] 3.2 mm pre-surgery to 2.5 [Formula: see text] 1.5 mm post-surgery (p < 0.05). The average VDI improved from 12.3 [Formula: see text] 4.8 mm pre-surgery to 3.3 [Formula: see text] 2.1 mm post-surgery (p < 0.05). The average pre-operative CMA improved from 115 [Formula: see text] 25° pre-surgery to 158 [Formula: see text] 21° post-surgery (p < 0.05); the pre-operative CAA changed from 101 [Formula: see text] 28° pre-surgery to 141 [Formula: see text] 10° post-surgery. After the operation, the clinic symptoms improved, and the JOA score improved from 9.3 [Formula: see text] 2.8 pre-operatively to 13.8 [Formula: see text] 2.5 in the sixth months of follow-up. CONCLUSION: In addition to soft tissue factors, bony obstruction was another important factor impeding atlantoaxial reduction. Transoral bony deformity osteotomy, remodeling, releasing combined with plate fixating was effective in treating IAAD/BI with bony obstruction factors.

A comprehensive analysis and literature review of vertebral artery variation in craniovertebral junction using three-dimensional computed tomography angiography.

PURPOSE: To describe vertebral artery (VA) variation in patients with or without osseous anomalies at congenital craniovertebral junction (CVJ). METHODS: In the present study, we retrospectively analyzed 258 patients with VA variation who underwent three-dimensional computed tomography angiography (3D CTA) in our hospital from March 2017 to October 2019. RESULTS: Among 258 patients, 180 were accompanied by skeleton structural malformation, including 105 cases of occipital ossification of the atlas, 8 cases of the bipartite atlas, 7 cases of hypoplasia of the posterior arch of the atlas, 45 cases of C2/3 congenital fusion, 2 cases of C2/3/4 congenital fusion, and 13 cases of congenital os odontoid. VA variation was divided into type A (VA variation in the CVJ area without osseous anomalies) and type B (VA variation in the CVJ area with osseous anomalies). There are totally 10 subtypes, including type A1 (atlas occipitalization with VA entrance approach close to middle line, 20.2%); type A2 (atlas occipitalization with VA entrance approach far from middle line, 30.2%); type A3 (first intersegmental VA in C1-C2, 1.9%); type A4 (fenestration of the VA, 2.3%); type A5 (VA bulging type, 6.6%); type A6 (VA exposures with the absence of the posterior atlas arch, 2.3%); type A7 (C2 inner wall type, 0.4%); type A8 (single vertebral artery, 2.3%); type B1 (posterior ponticuli, 2.7%); and type B2 (high-riding VA, 31.4%). CONCLUSION: This study is expected to take the lead in the most comprehensive classification of VA variation.

Research on pharyngeal bacterial flora in transoral atlantoaxial operation and the postoperative follow-up study.

OBJECTIVES: To study the changes of bacterial flora after a series of preoperative oral disinfection and the postoperative recovery of nerve function of patients with craniovertebral junction disorders who were treated with transoral approach operations. METHODS: This research analyzed 20 cases collected from October 2009 to May 2010. All these patients were with CVJ disorders, including 8 males and 12 females, aged 2 to 66 (38.1 on average), and they were all treated with transoral approach operations. The mucosa samples of the posterior pharyngeal wall were sent for bacteria culture. These samples were collected by sterile cotton swabs at four crucial points, including 3 days before operation/before gargling, 3 days after continuous gargling/after anesthesia intubation on the day of operation, after intraoperative cleaning and washing of the mouth, and after intraoperative iodophor immersion. The microflora was stained by means of smear and further counted after an investigation by microscope. The neural function of patients was evaluated by the ASIA classification and the JOA scores. All patients but two with posterior stabilization performed respectively underwent transoral atlantoaxial reduction plate (TARP) fixation consecutively in the same sitting. A regular reexamination of cervical vertebra with lateral and open mouth X-ray, CT and MRI was conducted after operation to evaluate the reduction of atlantoaxial dislocation, internal fixation position, bone graft fusion, inflammatory lesions and tumor recurrence. RESULTS: This bacteriological research showed that the mucosa of the posterior pharyngeal wall of all the patients was in a sterile state after a series of oral preoperative preparations and intraoperative iodophor disinfection, which was considered as type I incision. The bacterial culture results of the mucosa samples of the posterior pharyngeal wall collected at different time points showed significant differences (χ2 = 42.762, P = 0.000). All the patients had improvement in ASIA, and their neural functions were improved to different levels after operation. There was a significant difference in JOA scores before and after operation (t = 8.677, P = 0.000). Postoperative imaging examination showed that the atlantoaxial screw position was good and firm, and the CVJ disorders were treated appropriately. CONCLUSION: It is safe and effective to cut the posterior pharyngeal muscle layer and implant internal fixation by means of transoral approach.

Usefulness of a Three-Dimensional-Printed Model in the Treatment of Irreducible Atlantoaxial Dislocation with Transoral Atlantoaxial Reduction Plate.

OBJECTIVE: To evaluate the usefulness of a 3D-printed model for transoral atlantoaxial reduction plate (TARP) surgery in the treatment of irreducible atlantoaxial dislocation (IAAD). METHODS: A retrospective review was conducted of 23 patients (13 men, 10 women; mean age 58.17 ± 5.27 years) with IAAD who underwent TARP from January 2015 to July 2017. Patients were divided into a 3D group (12 patients) and a non-3D group (11 patients). A preoperative simulation process was undertaken for the patients in the 3D group, with preselection of the TARP system using a 3D-printed 1:1 scale model, while only imaging data was used for the non-3D group. Complications, clinical outcomes (Japanese Orthopaedic Association [JOA] and visual analogue score [VAS]), and image measurements (atlas-dens interval [ADI], cervicomedullary angle [CMA], and clivus-canal angle [CCA]) were noted preoperatively and at the last follow up. RESULTS: A total of 23 patients with a follow-up time of 16.26 ± 4.27 months were included in the present study. The surgery duration, intraoperative blood loss, and fluoroscopy times in the 3D group were found to be shorter than those in non-3D group, with statistical significance. The surgery duration was 3.29 ± 0.45 h in the 3D group and 4.68 ± 0.90 h in the non-3D group, and the estimated intraoperative blood loss was 131.67 ± 43.03 mL in the 3D group and 185.45 ± 42.28 mL in the non-3D group. No patients received blood transfusions. The intraoperative fluoroscopy times were 5.67 ± 0.89 in the 3D group and 7.91 ± 1.45 in the non-3D group. Preoperatively and at last follow up, JOA and VAS scores and ADI, CCA, and CMA were improved significantly within the two groups. However, no statistical difference was observed between the two groups. However, surgical site infection occurred in 1 patient in the 3D group, who underwent an emergency revision operation of the removal of TARP device and posterior occipitocervical fixation; the patient recovered 2 weeks after the surgery. In 2 patients in the traditional group, a mistake occurred in the placement of screws, with no neurological symptoms related to the misplacement. CONCLUSION: Preoperative surgical simulation using a 3D-printed real-size model is an intuitive and effective aid for TARP surgery for treating IAAD. The 3D-printed biomodel precisely replicated patient-specific anatomy for use in complicated craniovertebral junction surgery. The information was more useful than that available with 3D reconstructed images.

Classification and Surgical Treatment of Developmental Spinal Canal Stenosis at Atlas Level: A 15-Case Study.

STUDY DESIGN: A retrospective study. OBJECTIVE: Investigate the diagnosis and surgery strategy for treatment of development spinal canal stenosis (DSSA) at atlas plane based on computerized tography (CT) image characters. SUMMARY OF BACKGROUND DATA: The occurrence of spinal canal stenosis in the atlas plane is relatively rare compared with lower cervical. METHODS: Fifteen patients diagnosed with DSSA were included from 2014 to 2018. They are divided into four subgroups based on the character of CT images: group I (small size atlas), group II (hypertrophy of posterior arch of the atlas [PAA]), group III (incurved of PAA), and group IV (hypertrophy odontoid). RESULTS: There are type I 7, type II 3, type III 2, and group IV 3 in the 15 cases. All the patients received different surgery procedures respectively: (1) posterior arch osteotomy were performed for group I/III//IV without atlantoaxial dislocation, (2) posterior arch resect and replantation were performed for group II, (3) occipital cervical fixation and fusion were added to the patients with associated atlantoaxial dislocation (AAD), (4) a new method of odontoid reduce and atlantoaxial fixation by transoral approach were performed for group IV with associated AAD. All cases underwent surgery successfully which included posterior occipitocervical fixation (OCF) + posterior arch resection (PAR) eight cases, PAR four cases, posterior arch remodeling and re-implantation (PARR) two cases, and Dens remodeling + trans-oral anterior reduction and plate fixation (DR+TARP) one case without severe complications. All patients show different improvement in the symptoms. Japanese orthopaedic association score improved from 9.2 to 14.7 in 1 year follow-up. CONCLUSION: DSSA could be easily diagnosed and divided into four subgroups according to the character of CT image, corresponding surgery strategy could receive a fine clinical result.Level of Evidence: 4.

A biomechanical comparison of crossed and parallel rod configurations in atlantoaxial internal fixation.

BACKGROUND: Posterior atlantoaxial fixation with screw rod forms an approximate "II" shape or "H" increasing transverse link for better stability. In order to improve stability and in consideration of difficult placement of transverse connecting rod, possibility of inadequate bone graft, some scholars have preliminarily researched biomechanics of a novel crossed rod as an approximate "X" configuration of screw rod. PURPOSE: The aim of this study was to evaluate and compare the biomechanics of the crossed and parallel rod configurations in the screw rod system for posterior atlantoaxial fixation on a cadaveric model. METHODS: Six fresh cervical specimens were used to complete the range of motion (ROM) testing by applying pure moments of ± 2.0 nm. Following intact state and under destabilization testing, screws were implanted. The specimens were then tested in the following sequence: Group BLS + PR (C2 bilateral laminar screws + parallel rod), Group BLS + CR (C2 bilateral laminar screws + crossed rod), LPRLS + PR (C2 left pedicle screw and right laminar screw + parallel rod), LPRLS + CR (C2 left pedicle screw and right laminar screw + crossed rod), BPS + PR (C2 bilateral pedicle screws + parallel rod) and BPS + CR (C2 bilateral pedicle screws + crossed rod). The ROM of the C1-2 segments was measured in flexion-extension, lateral bending and axial rotation. Six surgical constructs were compared between the groups and with intact condition, respectively. RESULTS: The six fixed modes significantly increased stability compared with both the intact and destabilization group in flexion-extension, lateral bending and axial rotation (p < .05). In extension, BPS + CR and BLS + CR showed greater stability than BLS + PR (p < .05). During flexion, the six fixation methods showed no statistical significance (p > .05). In left lateral bending, stability of the other five screw rod fixation techniques significantly increased when compared with BLS + PR (p < .05). In the right lateral bending direction, the stability of BLS + PR was worse than that of BPS + CR and BPS + PR (p < .05). In the left axial rotation, stability of BLS + CR, LPRLS + CR and BPS + CR was greater than that of BLS + PR, LPRLS + PR and BPS + PR (p < .05). In the right axial rotation, the stability of BPS + CR and BLS + CR was greater than that of BLS + PR (p < .05). CONCLUSION: The six investigated fixation methods provide sufficient biomechanical stability. The crossed rod configuration can further enhance the axial rotation stability of the screw rod system, which consists of C1 bilateral pedicle and C2 pedicle, or C2 lamina screws. The crossed rod can also improve the stability of the screw rod system made up of C1 bilateral pedicle and C2 lamina screws in lateral bending and extension. The crossed rod configuration is reliable and provides superior stability for clinical application.

Relationship between the laminectomy extension and spinal cord injury caused by acute spinal shortening: goat in vivo experiment.

OBJECTIVE: To investigate the relationship between different types of laminectomy extension and spinal cord injury subsequent to acute spinal shorting after 3-column osteotomy in living goat model. METHODS: A total of 18 healthy goats were selected, and a procedure of bivertebral column resections and total laminectomy of T13 and L1 was completed followed by different laminectomy extensions under the somatosensory evoked potential (SSEP) monitoring. The samples were divided into three groups according to types of subsequent laminectomy extension. In the first group (enlarged resection of upper lamina group), laminectomy extension was performed on 10 mm caudal to T12; in the second group (equidistant enlarged resection of upper and lower lamina group), laminectomy extension was performed on 5 mm caudal to T12 and 5 mm cranial to L2 simultaneously; and in the third group (enlarged resection of lower lamina group), laminectomy extension was performed on 10 mm cranial to L2. The SSEP measured after vertebral resection was set as the baseline, and the SSEP decreased by 50% from the baseline amplitude and/or delayed by 10% relative to the baseline peak latency was set as positive results, which indicated spinal cord injury. Spinal column was gradually shortened until the SSEP monitoring just did not show a positive result. The shortened distance (ΔH) and the changed angle of the spinal cord buckling (Δα) were measured in each group. Neurologic function was recorded by the Tarlov scores at 2 days after the surgery. RESULTS: The safe shortening distances of three groups were 38.6 ± 1.2 mm, 41.5 ± 0.7 mm, 43.7 ± 0.8 mm, respectively; the corresponding changed angles of the spinal cord buckling were 62.8 ± 6.9°, 82.8 ± 7.5°, and 98.5 ± 7.0°. Significant differences of ΔH and Δα were found among the three groups by LSD multiple comparison test (P < 0.05). Strong correlation between ΔH and Δα was shown in each group by Pearson's correlation test. CONCLUSIONS: Different laminectomy extensions after 3-column osteotomy have different effects on the prevention of SCI caused by acute spinal shortening. The enlarged resection of lower lamina is superior to equidistant enlarged resection of upper and lower laminas which is superior to enlarged resection of upper lamina in preventing SCI. These slides can be retrieved under Electronic Supplementary Material.

Anterior Transoral Débridement Combined with Posterior Fixation and Fusion for Atlantoaxial Tuberculosis.

BACKGROUND: Atlantoaxial tuberculosis (TB) is rare in clinical practice, accounting for only about 0.3%-1% of spinal TB. An anterior-only surgical approach cannot provide strong fixation, whereas a posterior approach cannot achieve complete removal of lesions. A method combining anterior and posterior approaches to treat atlantoaxial TB is advisable. The aim of this study was to evaluate the effectiveness of anterior transoral débridement combined with posterior fixation and fusion for atlantoaxial TB. METHODS: Clinical data of 20 patients with atlantoaxial TB who underwent anterior transoral débridement combined with posterior fixation and fusion in our hospital were retrospectively analyzed. Antituberculosis drugs were administered for 18 months after surgery. Neurologic status, clinical symptoms, fusion, reduction, and complications were evaluated. RESULTS: Surgeries were performed successfully in all 20 cases with no injuries to spinal cord, nerves, or blood vessels. Clinical symptoms were relieved in all 20 patients (100%). Postoperative Japanese Orthopaedic Association score, occipitocervical visual analog scale score, and atlantodental interval were significantly improved (P < 0.05). Average follow-up duration was 33 months (range, 24-48 months). Bony fusion was achieved in all 20 cases. No serious complications were documented during follow-up. CONCLUSIONS: Anterior transoral débridement combined with posterior fixation and fusion is an effective treatment for atlantoaxial TB, achieving removal of lesions and stability.

An 11-Year Review of the TARP Procedure in the Treatment of Atlantoaxial Dislocation.

STUDY DESIGN: Retrospective study. OBJECTIVE: The aim of the study was to introduce the surgical techniques and evaluate the clinical outcomes of transoral atlantoaxial reduction plate (TARP) for the treatment of atlantoaxial dislocation. SUMMARY OF BACKGROUND DATA: Researchers have reported on transoral plate internal fixation for the treatment of irreducible atlantoaxial dislocation (IAAD) without long-term follow-up and detailed clinical experience. METHODS: The clinical records of 388 patients with atlantoaxial dislocation (IAAD, 340 cases; fixed atlantoaxial dislocation [FAAD], 48 cases) who received the TARP procedure from April 2003 to September 2014 were retrospectively reviewed. They were treated separately with TARP-I or TARP-II (82 cases), TARP-III (248 cases), or TARP-IV (58 cases). X-ray and magnetic resonance imaging were used to evaluate the efficacy of reduction and the degree of decompression, respectively. The long-term clinical outcome was evaluated by Japanese Orthopaedic Association scoring and the Symon and Lavender standard. RESULTS: Immediate reduction was achieved for all the patients with IAAD (340/340), whereas anatomical reduction was achieved for 98.2% of patients (334/340). Anatomical reduction was achieved in 87.5% of patients with FAAD (42/48). The average degree of spinal cord decompression ranged from 75% to 100% with an average of 88.4%. The clinical data of 106 patients were evaluated in the latest follow-up (12-108 mo, average 60.5 mo). The average spinal cord improvement rate by Japanese Orthopaedic Association scoring was 62.1%. According to the Symon and Lavender standard, there were 85 cases rated as markedly effective, 104 cases as effective, and 2 cases as noneffective. The overall markedly effective rate was 80% and the effective rate was 98%. CONCLUSION: The TARP procedure showed good anterior atlantoaxial release, reduction, decompression, and internal fixation for patients with IAAD and FAAD through a single anterior approach. It has the advantages of three-dimensional immediate atlantoaxial reduction and sufficient decompression. LEVEL OF EVIDENCE: 3.

Treatment of Basilar Invagination With Klippel-Feil Syndrome: Atlantoaxial Joint Distraction and Fixation With Transoral Atlantoaxial Reduction Plate.

BACKGROUND: Klippel-Feil syndrome (KFS) is characterized by congenital vertebral fusion of the cervical spine and a wide spectrum of associated anomalies. In patients with KFS with basilar invagination (BI), compression of the brainstem and upper cervical cord results in neurological deficits, and decompression and occipitocervical reconstruction are required. The highly varied anatomy of KFS makes a posterior occipitocervical fixation strategy challenging. For these patients, the transoral atlantoaxial reduction plate (TARP) operation is an optimal option to perform a direct anterior fixation to achieve stabilization. OBJECTIVE: To evaluate the effectiveness of TARP internal fixation for the treatment of BI with KFS. METHODS: Ten consecutive patients with BI and KFS who underwent TARP reduction and fixation from 2010 to 2012 were reviewed. Clinical assessment and image measurements were performed preoperatively and at the most recent follow-up. Nine patients (9/10) were followed for an average of 31.44 months. RESULTS: Symptoms were alleviated in 9 of 9 patients (100.00%). The odontoid process was ideally corrected with the TARP system. The mean clivus canal angle improved from 124° preoperatively to 152° postoperatively. The average preoperative and postoperative Japanese Orthopedic Association scores were 10.56 (n = 9) and 14.67 (n = 9), respectively, indicating 63.82% improvement. There was bony bridge catenation on the computed tomography scans and no evidence of hardware failure at 6 months. CONCLUSION: The TARP operation is effective and safe for treating patients with BI with KFS. The midterm clinical results were satisfactory.

Influence of vertebral column distraction on spinal cord volume: an experimental study in a goat model.

INTRODUCTION: Spinal cord injury may be related to excessive distraction of the spinal cord during surgical correction of spinal deformities by vertebral column resection. This study aimed to investigate how vertebral column distraction influences spinal cord volume to establish the safe range in a goat model. MATERIALS AND METHODS: A vertebral column resection was performed on the tenth thoracic vertebra of 11 goats. The spinal cord was distracted until the somatosensory evoked potential signals were decreased to 50 % from baseline amplitude or were delayed by 10 % of the baseline peak latency. The osteotomy segment was stabilized with a PEEK mesh cage filled with bone graft, and the pedicle screws on the rods were then tightened in this position. Spinal cord volume was calculated using Mimics software, and T10 height, disk height, osteotomy segment height, and spinal segment height were measured using the MRI image workstation. RESULTS: Three goats were excluded, and data obtained from the eight remaining goats were analyzed. The safe limit of distraction distance was 11.8 ± 3.65 mm, and the distraction distance was strongly correlated with the difference between the pre- and postoperative measurements (d value) of spinal cord volume per 1 mm of osteotomy segment height (r = -0.952, p < 0.001), but was not correlated with T10 body height (r = 0.16, p = 0.71), spinal segment height (r = 0.29, p = 0.49), disk height (r = -0.12, p = 0.98), or the d value (pre-post) of spinal cord volume per 1 mm of spinal segment height (r = 0.45, p = 0.26). The mean d value (pre-post) of spinal cord volume per 1 mm of osteotomy segment height was 10.05 ± 0.02 mm(3) (range 10.02-10.08 mm(3)). CONCLUSION: The maximum change in spinal cord volume per 1-mm change in height was in the osteotomy segment, and its safe limit was 10.05 ± 0.02 mm(3). The safe limit of spinal cord distraction can be calculated using the spinal cord volume per unit 1-mm change in height.

Relationship between Spinal Cord Volume and Spinal Cord Injury due to Spinal Shortening.

Vertebral column resection is associated with a risk of spinal cord injury. In the present study, using a goat model, we aimed to investigate the relationship between changes in spinal cord volume and spinal cord injury due to spinal shortening, and to quantify the spinal cord volume per 1-mm height in order to clarify a safe limit for shortening. Vertebral column resection was performed at T10 in 10 goats. The spinal cord was shortened until the somatosensory-evoked potential was decreased by 50% from the baseline amplitude or delayed by 10% relative to the baseline peak latency. A wake-up test was performed, and the goats were observed for two days postoperatively. Magnetic resonance imaging was used to measure the spinal cord volume, T10 height, disc height, osteotomy segment height, and spinal segment height pre- and postoperatively. Two of the 10 goats were excluded, and hence, only data from eight goats were analyzed. The somatosensory-evoked potential of these eight goats demonstrated meaningful changes. With regard to neurologic function, five and three goats were classified as Tarlov grades 5 and 4 at two days postoperatively. The mean shortening distance was 23.6 ± 1.51 mm, which correlated with the d-value (post-pre) of the spinal cord volume per 1-mm height of the osteotomy segment (r = 0.95, p < 0.001) and with the height of the T10 body (r = 0.79, p = 0.02). The mean d-value (post-pre) of the spinal cord volume per 1-mm height of the osteotomy segment was 142.87 ± 0.59 mm3 (range, 142.19-143.67 mm3). The limit for shortening was approximately 106% of the vertebral height. The mean volumes of the osteotomy and spinal segments did not significantly change after surgery (t = 0.310, p = 0.765 and t = 1.241, p = 0.255, respectively). Thus, our results indicate that the safe limit for shortening can be calculated using the change in spinal cord volume per 1-mm height.

Electrically pumped random lasing with an onset voltage of sub-3 V from ZnO-based light-emitting devices featuring nanometer-thick MoO3 interlayers.

We have previously reported on electrically pumped random lasing (RL) with onset voltages at least 3.3 V from ZnO-based light-emitting devices with metal-insulator-semiconductor (MIS) structures in the form of Au/SiO2/ZnO. Here, by inserting an ∼5 nm thick MoO3 layer between SiO2 and ZnO films in the aforementioned MIS structured device, the RL onset voltage is decreased to only ∼2.6 V and, moreover, the output optical power is multiplied several times. Such improved RL performance is ascribed to the enhanced injection of holes into ZnO via the MoO3 interlayer that features a low-lying conductive band and therefore a large work function.

The development and evaluation of individualized templates to assist transoral C2 articular mass or transpedicular screw placement in TARP-IV procedures: adult cadaver specimen study.

OBJECTIVES: The transoral atlantoaxial reduction plate system treats irreducible atlantoaxial dislocation from transoral atlantoaxial reduction plate-I to transoral atlantoaxial reduction plate-III. However, this system has demonstrated problems associated with screw loosening, atlantoaxial fixation and concealed or manifest neurovascular injuries. This study sought to design a set of individualized templates to improve the accuracy of anterior C2 screw placement in the transoral atlantoaxial reduction plate-IV procedure. METHODS: A set of individualized templates was designed according to thin-slice computed tomography data obtained from 10 human cadavers. The templates contained cubic modules and drill guides to facilitate transoral atlantoaxial reduction plate positioning and anterior C2 screw placement. We performed 2 stages of cadaveric experiments with 2 cadavers in stage one and 8 in stage two. Finally, guided C2 screw placement was evaluated by reading postoperative computed tomography images and comparing the planned and inserted screw trajectories. RESULTS: There were two cortical breaching screws in stage one and three in stage two, but only the cortical breaching screws in stage one were ranked critical. In stage two, the planned entry points and the transverse angles of the anterior C2 screws could be simulated, whereas the declination angles could not be simulated due to intraoperative blockage of the drill bit and screwdriver by the upper teeth. CONCLUSIONS: It was feasible to use individualized templates to guide transoral C2 screw placement. Thus, these drill templates combined with transoral atlantoaxial reduction plate-IV, may improve the accuracy of transoral C2 screw placement and reduce related neurovascular complications.

The development and evaluation of individualized templates to assist transoral C2 articular mass or transpedicular screw placement in TARP-IV procedures: adult cadaver specimen study

OBJECTIVES: The transoral atlantoaxial reduction plate system treats irreducible atlantoaxial dislocation from transoral atlantoaxial reduction plate-I to transoral atlantoaxial reduction plate-III. However, this system has demonstrated problems associated with screw loosening, atlantoaxial fixation and concealed or manifest neurovascular injuries. This study sought to design a set of individualized templates to improve the accuracy of anterior C2 screw placement in the transoral atlantoaxial reduction plate-IV procedure. METHODS: A set of individualized templates was designed according to thin-slice computed tomography data obtained from 10 human cadavers. The templates contained cubic modules and drill guides to facilitate transoral atlantoaxial reduction plate positioning and anterior C2 screw placement. We performed 2 stages of cadaveric experiments with 2 cadavers in stage one and 8 in stage two. Finally, guided C2 screw placement was evaluated by reading postoperative computed tomography images and comparing the planned and inserted screw trajectories. RESULTS: There were two cortical breaching screws in stage one and three in stage two, but only the cortical breaching screws in stage one were ranked critical. In stage two, the planned entry points and the transverse angles of the anterior C2 screws could be simulated, whereas the declination angles could not be simulated due to intraoperative blockage of the drill bit and screwdriver by the upper teeth. CONCLUSIONS: It was feasible to use individualized templates to guide transoral C2 screw placement. Thus, these drill templates combined with transoral atlantoaxial reduction plate-IV, may improve the accuracy of transoral C2 screw placement and reduce related neurovascular complications. .

Application of three-dimensional model in the management of irreducible atlanto-axial dislocation.

OBJECTIVE: The aim of this study was to describe the application of the rapid prototyping (RP) life-size 3-dimensional model used to improve accuracy of screw insertion in irreducible atlanto-axial dislocation (IAD). METHODS: The study included 10 patients with IAD. All patients were assessed using the Japanese Orthopedic Association (JOA) score. Radiographs, MRI and CT were conducted during the preoperative and postoperative procedure. A 3D RP model was created for each patient. The model was used to obtain detailed information of each pedicle and used as an intraoperative reference. Assisted by the model, transoral atlanto-axial reduction plate fixation was performed in each case. RESULTS: The average operation time was 145 (range: 90 to 180) minutes and average blood loss was 120 (range: 60 to 250) ml. JOA scores improved after surgery. All 40 transoral pedicle/lateral mass screws were placed without serious complications or internal fixation failure. Postoperative radiographs and CT scan showed 38 transoral pedicle/lateral mass screws located in the pedicle tracts. Satisfactory reduction was achieved in 95% of screws. Two screws perforated the lateral wall of the C2 pedicles in an extremely narrow pedicle case. No neurologic sequelae or vertebral artery injury were detected. CONCLUSION: The RP technique is effective and reliable in achieving an accurate and safe screw insertion during IAD surgery, especially in anatomically abnormal cases.

Clinical application of computer-aided design-rapid prototyping in C1-C2 operation techniques for complex atlantoaxial instability.

STUDY DESIGN: This is a retrospective clinical study. OBJECTIVE: To evaluate the clinical efficacy of computer-aided design-rapid prototyping (CAD-RP) techniques in surgical treatments for atlantoaxial instability (AAI). SUMMARY OF BACKGROUND DATA: The complexity of the upper cervical anatomic structures makes the procedures for the treatment of AAI particularly challenging for surgeons. The present study represents a series of C1-C2 surgery for AAI aided by CAD-RP. METHODS: A total of 49 patients (21 men and 28 women) with AAI were treated in our department. According to the use of the CAD-RP technique, the patients were divided into RP group and No RP group. Preoperative CT scans of the upper cervical spine were performed for each patient. For the RP group, physical RP models of the upper cervical spine were manufactured from the 3-dimensional CT data and were used for intraoperative guidance. Personalized surgeries were performed for each case of the 2 groups. The screw malposition rate, frequency of using intraoperative fluoroscopy, operation time, blood loss, and improvement of neurological function were compared between the 2 groups. The mean follow-up duration was 32 months (range, 24-50 mo). RESULTS: The operations were successfully performed in 48 cases expect for 1 case in the No RP group. A total of 204 screws were placed. The intraoperative fluoroscopy frequency and operation time were significantly lower in the RP group than that in the No RP group in both posterior and anterior approaches, whereas the screw malposition rate showed no difference between the 2 groups for both approaches. After the operation, 48 cases achieved satisfactory decompression of the cervical cord and repositioning of the atlantoaxial spine. During follow-up, 47 cases presented improvements in the spinal nerve function within 2 years. CONCLUSIONS: CAD-RP techniques have significant benefits for surgeons providing personalized treatments for AAI, especially cases with complicated deformities.

Anterior pedicle screw fixation of C2: an anatomic analysis of axis morphology and simulated surgical fixation.

STUDY DESIGN: Human cadaveric study measuring the morphology of C2 vertebra, description of anterior placement of pedicle screw with post-fixation computed tomography (CT) analysis. OBJECTIVE: To assess the potential feasibility and safety anterior placement of C2 pedicle screws. SUMMARY OF BACKGROUND DATA: Posterior pedicle screw fixation has become an established technique for upper cervical reconstruction. To our knowledge few reports in the previous literature have described the placement of or anatomy related to anteriorly approach C2 pedicle screws. METHODS: The morphology of 60 human C2 vertebrae was measured directly to assess the size, position, and relative approach angle of the pedicles from an anterior perspective. In an additional 20 cadaveric cervical spines, bilateral 3.5 mm titanium C2 pedicle screws were placed and analyzed for pedicle morphology and placement accuracy with thin cut, 1 mm axial CT. RESULTS: The mean C2 pedicle width measured directly and by CT scan was 7.8 and 6.6 mm, and the average length of the right and left pedicle was 26.4 and 25 mm, respectively. The mean transverse angle (α) was 17.6° and 21.4°, whereas declination angle (ß) anterior to posterior was 13.8° and 10.6°, respectively. CONCLUSIONS: Quantitative data regarding C2 pedicle shape and location with respect to the anterior placement of pedicle screws have not been previously reported. This study indicates that anterior placement of 3.5 mm C2 pedicle screws through a transoral approach may be both feasible and safe and also provides an important anatomic analysis that may guide clinical application.

Personalised modified osteotomy using computer-aided design-rapid prototyping to correct thoracic deformities.

The correction of severe thoracic deformities is challenging. However, the usual imaging modalities are not sufficient for performing the surgery. Our objective was to describe the procedure and results of posterior modified wedge osteotomy aided by the techniques of computer-aided design-rapid prototyping (CAD-RP) to correct thoracic deformities. Twenty-one patients with thoracic deformities (eight males; 13 females) formed the study group. All patients underwent computed tomography (CT) scanning and CAD-RP, and a model of thoracic deformities and navigation templates of pedicles were created for each patient and used to analyse the spinal deformities and serve as anatomical reference. Aided by these models, personalised modified wedge osteotomy combining the eggshell technique and posterior vertebral column resection was performed. Using CAD-RP improved the safety and accuracy of surgery and screw placement in the 21 patients in whom 41 vertebrae were removed and 216 pedicle screws were placed. The average operation time was 260 (200-420) min, with an average blood loss of 1,900 ml (range 800-3560 ml). The percentage of deformity correction was 56.3% (from 72.1° to 31.5°) in the coronal plane and 60.4% (from 81.6° to 32.3°) in the sagittal plane. No patient had serious complications or implant failure. Personalised single-stage posterior modified wedge osteotomy is an effective procedure for treating thoracic deformities. Using CAD-RP and the RP models have significant benefits for personalised surgical treatment of complex thoracic deformities.