Posterior Atlantoaxial Fusion Research Articles

Imaging study on determining the rationality of atlantoaxial fixation angle based on the ratio of line segments between anatomical markers on lateral X-ray films

Objective: To propose a method to determine the unreasonableness of the fixed angle in posterior atlantoaxial fusion surgery based on the ratio of line segments between anatomical landmarks of the atlantoaxial joint. Methods: A cross-sectional study was conducted. According to the inclusion criteria, a screening was performed on the database of asymptomatic volunteers who had full-spine lateral X-ray films taken at the Second Affiliated Hospital of Wenzhou Medical University from May 2016 to May 2021. A total of 207 volunteers were included, comprising 98 males with an age of (40.68±13.87) years and 109 females with an age of (42.64±14.45) years. On the lateral X-ray film, a line (L) parallel to the posterior margin of the odontoid process was drawn at the posterior edge of the lower articular surface of the axis (a), intersecting the atlas at points b, c, and d. The line segments ab, bd, bc, and the C1-C2 angle were measured, and the ratios of bd/ab and bc/ab were calculated. The ability of bd/ab and bc/ab to predict the unreasonable fixed angle of the atlantoaxial joint (≥22°) was analyzed by receiver operating characteristic (ROC) curve analysis in both male and female. The areas under the ROC curves (AUC) were calculated, and the performance of the two prediction methods was compared using the Delong's test. The cutoff value for distinguishing the unreasonableness of the C1-C2 angle and the sensitivity and specificity were calculated. Results: The ROC curve analysis in the male group showed that the AUC of bc/ab for predicting the unreasonable C1-C2 angle was 0.791 (95%CI: 0.696-0.867, P<0.001), with a cutoff value of 0.449, sensitivity of 97.3%, and specificity of 70.0%. The performance was significantly better than that of bd/ab (cutoff value 1.100, AUC=0.532, 95%CI: 0.428-0.634, sensitivity 26.3%, specificity 83.3%, P<0.001). The ROC curve analysis in the female group showed that the AUC of bc/ab for predicting the unreasonable C1-C2 angle was 0.804 (95%CI: 0.745-0.852, P<0.001), with a cutoff value of 0.488, sensitivity of 90.5%, and specificity of 58.6%. The performance was significantly better than that of bd/ab (cutoff value 0.960, AUC=0.687, 95%CI: 0.624-0.748, sensitivity 90.5%, specificity 44.8%, P=0.041). Conclusions: The bc/ab value can be used as an effective indicator to predict the unreasonable C1-C2 angle in posterior atlantoaxial fusion surgery with high diagnostic accuracy. The cutoff value for males is<0.449, and for females is<0.488.

The use of a novel reduction plate in transoral anterior C1-ring osteosynthesis for unstable atlas fractures.

Transoral anterior C1-ring osteosynthesis has been reported as an effective treatment for unstable atlas fracture, which aims to preserve important C1-C2 motion. However, previous studies have shown that the anterior fixation plates used in this technique were not suitable for the anterior anatomy of the atlas and lacked an intraoperative reduction mechanism. This study aims to evaluate the clinical effects of a novel reduction plate used in transoral anterior C1-ring osteosynthesis for unstable atlas fractures. 30 patients with unstable atlas fractures treated by this technique from June 2011 to June 2016 were included in this study. The patients' clinical data and radiographs were reviewed, and the reduction of the fracture, internal fixation placement, and bone fusion were assessed using pre- and postoperative images. The patients' neurological function, rotatory range of motion, and pain levels were evaluated clinically during follow-up. All 30 surgeries were successfully performed, and the average follow-up duration was 23.5 ± 9.5 months (range 9-48 months). One patient suffered atlantoaxial instability during the follow-up and was treated with posterior atlantoaxial fusion. The remaining 29 patients had satisfactory clinical outcomes, with ideal fracture reduction, good screw and plate placement, well-preserved range of motion, neck pain alleviation and solid bone fusion. There were no vascular or neurological complications during the operation or follow-up. The use of this novel reduction plate in transoral anterior C1-ring osteosynthesis is a safe and effective surgical option in the treatment of unstable atlas fractures. This technique offers an immediate intraoperative reduction mechanism, which provides satisfactory fracture reduction, bone fusion, and preservation of C1-C2 motion.

C1-2 Fusion in Atlantoaxial Dislocation and Basilar Invagination with and without Chiari Malformation: Clinical/Radiological and Craniometric Results

Patients with Chiari malformation (CM) associated with atlantoaxial dislocation (AAD) and basilar invagination (BI) may present with a small posterior cranial fossa, but data on the volumetric analysis are lacking. Additionally, whether additional foramen magnum decompression (FMD) is needed together with atlantoaxial fusion remains controversial. This study evaluated the volumetric alterations of the posterior cranial fossa in these patients and analyzed the radiological and clinical outcomes after posterior C1-C2 reduction and fixation plus C1 posterior arch resection. Thirty-two adult Chiari malformation patients with AAD and basilar invagination BI (CM-AAD/BI group) and 21 AAD and BI patients without Chiari malformation (AAD/BI-only group) who received posterior atlantoaxial fusion plus C1 posterior arch resection were retrospectively studied. The clinical, radiological outcomes and volumetric measurements of the posterior cranial fossa were evaluated. The majority of CM-AAD/BI patients (94%) improved clinically and radiologically at 12 mo postoperatively, and none required additional FMD. Morphological analysis revealed a significant reduction in the bony posterior cranial fossa volumes of the CM-AAD/BI group (P < 0.01) and the AAD/BI-only group (P < 0.01) relative to those of the CM group. No significant differences were observed between the CM-AAD/BI and AAD/BI groups. Compared with patients with simple Chiari malformation, patients with AAD/BI with or without CM demonstrated a considerably and equally reduced bony posterior cranial fossa volume. No additional FMD is needed in the treatment of CM-AAD/BI patients after posterior reduction and fusion plus C1 posterior arch resection.

Posterior Atlantoaxial Fusion With C1-2 Pedicle Screw Fixation for Atlantoaxial Dislocation in Pediatric Patients With Mucopolysaccharidosis IVA (Morquio a Syndrome): A Case Series

To investigate the efficacy and safety of posterior atlantoaxial fusion (AAF) with C1-2 pedicle screw fixation for atlantoaxial dislocation (AAD) in pediatric patients with mucopolysaccharidosis (MPS) IVA. This study included 21 pediatric patients with MPS IVA who underwent posterior AAF with C1-2 pedicle screw fixation. Anatomical parameters of the C1 and C2 pedicle were measured on preoperative computed tomography (CT). The American Spinal Injury Association (ASIA) scale were used to evaluate the neurological status. The fusion and accuracy of pedicle screw was assessed on postoperative CT. Demographic, radiation dose, bone density, surgical, and clinical data were recorded. Patients reviewed included 21 patients younger than 16 years with an average age of 7.4 ± 4.2 years and an average of 20.9 ± 7.7 months follow-up. Fixation of 83 C1 and C2 pedicle screws was performed successfully and 96.3% of them were identified as being safe. One patient developed postoperative transient disturbance of consciousness and one developed fetal airway obstruction and died about 1 month after the surgery. In the left 20 patients, fusion was achieved, symptoms were improved, and no other serious surgical complications were observed at the latest follow-up. Posterior AAF with C1-2 pedicle screw fixation is effective and safe for AAD in pediatric patients with MPS IVA. However, the procedure is technically demanding and should be performed by experienced surgeons with strict multidisciplinary consultations.

Accuracy and Safety of Robot-Assisted versus Fluoroscopy-Guided Posterior C1 Lateral Mass and C2 Pedicle Screw Internal Fixation for Atlantoaxial Dislocation: A Preliminary Study.

Objective To compare the accuracy, efficiency, and safety of robotic assistance (RA) and conventional fluoroscopy guidance for the placement of C1 lateral mass and C2 pedicle screws in posterior atlantoaxial fusion. Methods The data of patients who underwent posterior C1–C2 screw fixation (Goel-Harm's technique) in our hospital from August 2014 to March 2021 were retrospectively evaluated, including 14 cases under fluoroscopic guidance and 11 cases under RA. The hospital records, radiographic results, surgical data, and follow-up records were reviewed. Accuracy of screw placement was assessed using the Gertzbein and Robbins scale, and clinical outcomes were evaluated by Japanese Orthopedic Association (JOA) score, visual analogue scale (VAS), modified MacNab criteria, and postoperative complications. Results Baseline characteristics of both groups were similar. The mean estimated blood loss in the fluoroscopic guidance and RA groups was 205.7 ± 80.3 mL and 120.9 ± 31.9 mL, respectively (p = 0.03). The mean surgical duration was 34 min longer with RA compared to that performed with free-hand (FH) method (p = 0.15). In addition, lower intraoperative radiation exposure was detected in the RA group (12.4 ± 1.4 mGy/screw) versus the FH (19.9 ± 2.1 mGy/screw) group (p = 0.01). The proportion of “clinically acceptable” screws (graded 0 and I) was higher in the RA group (93.2%) than that in the FH group (87.5%, p = 0.04). There was no significant difference in the increase of JOA score and decrease of VAS score between the two surgical procedures. Furthermore, there were no significant differences in overall clinical outcome between the two groups and no neurovascular complications associated with screw insertion. Conclusions RA is a safe and potentially more accurate alternative to the conventional fluoroscopic-guided FH technique for posterior atlantoaxial internal fixation.

Long-term observation of the effect of atlantoaxial fusion on the growth and development of children's cervical spine

Objective: To explore the effect of atlantoaxial fusion on the growth and development of children's cervical spine. Methods: The clinical data of 12 children with atlantoaxial dislocation who underwent posterior atlantoaxial fusion at Department of Orthopaedics,the 909th Hospital of Joint Logistics Support Force of Chinese People's Liberation Army from June 2002 to September 2013 were retrospective analyzed. There were 7 males and 5 females,with age of (8.1±3.1)years (range:3 to 13 years).Nine cases were traumatic and 3 cases were congenital malformations,1 of the children had Down syndrome. All children underwent posterior atlantoaxial fusion. Furthermore,the information of the height and anteroposterior width of the cervical vertebral bodies and vertical growth rate of the fusion mass were collected from all patients immediately postoperatively and during the follow-up.The range of motion in cervical spine were collected preoperatively and during follow-up period. Data were compared using independent sample t test, paired sample t test and repeated-measurement. Results: All 12 children had regular follow-up within (122.4±25.3)months(range:65 to 163 months). The height and anteroposterior width of the cervical vertebral bodies were similar to these results with those in published reports of growth in normal children of the same age(all P<0.01). At the last follow-up,atlantoaxial fusion of 11 cases had substantial growth (vertical growth rate of the fusion mass:11 cases ≥10%, 1 case <10%);the range of motion in cervical spine was close to the normal level (flexion(55.2±5.0)°,extension (65.3±4.9)°,left bending (41.7±4.5)°,right bending (42.4±4.4)°,left rotation (66.4±5.6)°,right rotation (68.5±5.8)°). Conclusions: Atlantoaxial fusion surgery is satisfactory in the treatment of pediatric atlantoaxial dislocation.During the follow-up,the growth and development of the cervical spine is close to that of normal children of the same age.In long-term observation,it has been found that the operation has no negative effect on the growth and development of the children's cervical spine.

Subaxial lordosis loss and influence factors after posterior atlantoaxial fusion

Summary of background dataCervical sagittal balance is an important evaluation index of cervical physiological function and surgical efficacy. Subaxial kyphosis after atlantoaxial fusion is negatively associated with worse clinical outcomes and higher incidence of lower cervical disk degeneration.ObjectivesThis study aimed to confirm the factors that influence subaxial lordosis loss after posterior atlantoaxial fusion.MethodsWe performed a retrospective review of all patients following posterior C1–C2 fusion for atlantoaxial dislocation between January 2015 and December 2017. All charts, records, and imaging studies were reviewed for each case, and preoperative, immediate postoperative, and final follow-up plain films were evaluated. Comparing final follow-up and preoperative C2–C7 angle, patients were divided into two groups for further comparison: subaxial lordosis loss group and subaxial lordosis increase group.ResultsA total of 18 patients were included in the review, with an average radiographic follow-up of 8.4 ± 3.7 months (range 6–17 months). Subaxial lordosis loss was observed in 5 cases (27.8%) at the final follow-up, whereas 13 cases had an increase in subaxial lordosis. The cervical sagittal parameters of preoperative and final follow-up between two groups were compared, the preoperative C2–C7 angle of the subaxial lordosis loss group was bigger than the subaxial lordosis increase group (27.6° ± 10.5° vs 10.5° ± 10.5°, P < 0.05), but there was no statistical difference in other parameters. Univariate chi-square analysis showed that reduction in subaxial lordosis after posterior atlantoaxial fusion was associated with preoperative C2–C7 angle ≥ 20° (χ2 = 4.923, P = 0.026). However, Logistic regression analysis showed that the preoperative C2–C7 angle ≥ 20° was not an independent risk factor (OR = 0.147, P = 0.225).ConclusionOur study demonstrates that subaxial lordosis loss may occur after posterior atlantoaxial fusion, and preoperative C2–C7 angle ≥ 20° was a risk factor of postoperative loss of subaxial lordosis.

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

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

C1 laminoplasty and posterior atlantoaxial fusion for large retro-odontoid pseudotumor with Instability: A technical note

BackgroundRetro-odontoid pseudotumor (ROPT) is a non-neoplastic pathology of the craniovertebral junction that is usually associated with atlantoaxial instability. The mass compresses the spinal cord, causing cervical myelopathy and potentially resulting in severe disability. Posterior atlantoaxial fixation without laminectomy is a suitable surgical option when the symptoms are mild and the static compression is moderate. In the setting of patients with severe symptoms and large ROPTs, posterior decompression becomes necessary. However, achieving solid posterior atlantoaxial fusion is difficult without a bony surface, namely the C1 posterior arch. Here, we describe a novel technique of C1 laminoplasty to achieve C1 decompression, and posterior atlantoaxial fusion with a modified Goel technique. MethodsAn 83-year-old man was referred to our orthopedic department with quadriplegia due to atlantoaxial instability. His daily life had been affected by severe neck pain, clumsiness of bilateral hands, and gait disturbance for more than 2 years. Preoperative cervical radiograms revealed atlantoaxial instability, and magnetic resonance imaging showed a large pseudotumor compressing to the spinal cord. ResultsThe patient underwent C1 laminoplasty to decompress the spinal cord and retain the posterior arch as a bony surface for grafting and posterior atlantoaxial fusion. The procedure was well tolerated. The patient’s quadriparesis was improved and his Japanese Orthopedic Association score improved from 9/17 to 15/17 and his visual analog scale score for neck pain improved from 75 mm to 28 mm at the 1-year follow-up. ConclusionC1 laminoplasty and posterior atlantoaxial fusion appears useful when C1 decompression and atlantoaxial fusion become necessary.

Improvements in Neck Pain and Disability Following C1-C2 Posterior Cervical Instrumentation and Fusion for Atlanto-Axial Osteoarthritis

Symptomatic Atlanto-axial (C1-2) osteoarthritis (AAOA) is a common phenomenon in elderly patients; however, there is a paucity of data on the effectiveness of posterior atlanto-axial fusion (PAAF) for this condition. To this end, here we assess changes in patient-reported outcomes and neck-related disability in adult patients undergoing PAAF for symptomatic C1-2 AAOA. In this retrospective study, the clinical records of consecutive patients with symptomatic AAOA who underwent PAAF between 2004 and 2017 were reviewed. Patient demographics, comorbidities, intraoperative and postoperative variables, and complication rates were collected. Neck Disability Index (NDI) scores were recorded at baseline and 6 weeks, 6 months, 1 year, and 2 years postoperatively. Forty-two patients (average age, 72.04 ± 8.56 years; 26.19% males) met the study's inclusion criteria. In this cohort, 19.04% had previous subaxial cervical spine surgery, 35.71% had a history of smoking (all had stopped smoking before surgery), and 11.90% had type II diabetes. At baseline, the majority of patients had a normal neurologic exam. The average preoperative NDI score was 26.88 ± 24.85, which improved to 10.59 ± 14.88 at the 1-year follow-up and 13.20 ± 14.96 at the 2-year follow-up (P=0.004). At baseline, 18% of the patients reported severe disability based on NDI score; this percentage decreased to 2% at 1 year and 0 at 2 years (P= 0.01). Importantly, a high percentage (11.90%) of patients had undergone previous subaxial cervical fusion for their pain due to a mistaken diagnosis for this condition, without symptom relief. In appropriately selected patients, PAAF may decrease neck pain and improve functional disability in patients with AAOA. Future prospective longitudinal studies are needed to corroborate these findings.

Miniplate-Augmented Interlaminar Fusion in C1–C2 Screwing

The interlaminar fusion combination involving C1-C2 screwing fixation is one of the most effective techniques for atlantoaxial dislocation or subluxation, and the bone graft is usually stabilized by wiring constructs. However, some adverse events were reported during the insertion of sublaminar wiring, such as accidentally damaging the spinal cord or dura. Thus we used the miniplate to stabilize the harvest bone graft on the C1-C2 laminar, which led to a shorter operation time and prevented spinal canal violation. This study investigated the safety and efficacy of the novel surgical technique, namely miniplate-augmented interlaminar fusion. We retrospectively reviewed 43 patients who underwent posterior atlantoaxial fusion with the miniplate-augmented iliac crest autograft at our institute. Complications related to surgery were recorded and calculated. After operation, patients were followed up through routine radiography to examine whether the fusion of the atlantoaxial segment was achieved. Success of fusion was defined as follows: 1) the presence of bone bridging between the bone graft and both the atlas and axis; and 2) the absence of movement of the atlantoaxial spinous process on flexion-extension radiography, which meant that the variation of length measured in 2 views, respectively, was <1 mm. The first time when radiography showed successful fusion after surgery was termed as fusion time and was recorded individually. In addition, overall fusion rates and mean fusion times were analyzed. Of 43 patients, long-term follow-up data were available for 31 patients, whereas the remaining 12 patients had dropped out (mean follow-up duration, 24.91 months; range, 6-72 months). Among 31 patients, 22 (70.96%) were women and 9 (29.03%) were men. The mean age was 63.33 years. Regarding the etiology, atlantoaxial dislocations or subluxations were caused due to degeneration, rheumatoid arthritis, odontoid fracture, trauma, and os odontoideum in 14 (45%), 3 (10%), 5 (16%), 8 (26%), and 1 (3%) patient(s), respectively. Successful fusion was achieved in 30 (96.77%) patients, with a mean fusion time of 6.23 months, whereas only 1 (3.23%) patient did not meet the fusion criteria. No complications related to the miniplate occurred. We noted vertebral artery rupture not requiring blood transfusion in 1 patient, aspiration pneumonia in 1 patient, urinary tract infection in 1 patient, anemia requiring transfusion in 1 patient, and leg dysesthesia in 1 patient. No neurologic deficit was found. Miniplate-augmented interlaminar fusion with C1-C2 screwing resulted in excellent fusion rates with a considerably low probability of complications. Hence this novel technique for bone graft fixation with atlantoaxial screwing has a good efficacy and safety and can serve as an alternative for bone graft fixation during C1-C2 fusion.

Posterior atlantoaxial fusion: a comprehensive review of surgical techniques and relevant vascular anomalies.

Posterior atlantoaxial fusion is an important surgical technique frequently used to treat various pathologies involving the cervical 1-2 joint. Since the beginning of the 20th century, various fusion techniques have been developed with improved safety profile, higher fusion rates, and superior clinical outcome. Despite the advancement of technology and surgical techniques, posterior C1-2 fusion is still a technically challenging procedure given the complex bony and neurovascular anatomy in the craniovertebral junction (CVJ). In addition, vascular anomalies in this region are not uncommon and can lead to devastating neurovascular complications if unrecognized. Thus, it is important for spine surgeons to be familiar with various posterior atlantoaxial fusion techniques along with a thorough knowledge of various vascular anomalies in the CVJ. Intimate knowledge of the various surgical techniques in combination with an appreciation for anatomical variances, allows the surgeon develop a customized surgical plan tailored to each patient's particular pathology and individual anatomy. In this article, we aim to provide a comprehensive review of existing posterior C1-2 fusion techniques along with a review of common vascular anomalies in the CVJ.

Is Initial Posterior Atlantoaxial Fixation and Fusion Applying Bilateral C1-2 Transarticular Screws and C1 Laminar Hooks Reliable for Acute Pediatric Atlantoaxial Instability?: A Minimal 10-Year Analysis of Outcome and Radiological Evaluation.

A retrospective case series study with at least 10 years of follow-up data. To validate the reliability of bilateral C1-2 transarticular screws and C1 laminar hooks and a bone autograft for acute pediatric atlantoaxial instability. The reliability of initial posterior atlantoaxial fusion in pediatric patients is still controversial. To date, however, only a few published articles with short-term follow-up data are available to help spinal surgeons understand the effects of posterior atlantoaxial fusion in the skeletally immature spine. Five pediatric patients with acute atlantoaxial instability underwent atlantoaxial fusion using the above technique over a 3-year period. During a minimum 10-year follow-up period, not only outcomes and complications were investigated, but the vertical growth of the constructed spine in relation to the growth of the entire cervical spine, overall cervical spinal alignment, and adjacent-segment instability were evaluated. The clinical follow-up indicated solid fusion and complete clinical relief from symptoms. No neural or vascular impairment was observed. The radiological evaluation showed that all patients had growth within the fusion construct reaching a mean 35.4% of the entire cervical spine. There were no radiological indicators of subaxial instability, even when cervical sagittal alignments became straight with a mean C2-7 angle of 6.4°. The results showed that initial posterior atlantoaxial fusion accomplished with bilateral C1-2 transarticular screws, C1 laminar hooks fixation, and bony autograft is a reliable surgical technique for treating acute pediatric atlantoaxial instability without negative effects on vertical growth at the fused level or the stability of the subaxial spine. 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.

Clinical Analysis of Radiologic Measurements in Patients with Basilar Invagination

To investigate correlations between radiologic measurements and clinical outcomes in patients with basilar invagination (BI). The medical records and radiologic data of 46 patients (27 women) who had undergone posterior atlantoaxial fusion or occipitocervical fusion for BI from January 2010 to June 2018 were retrospectively analyzed. Patients under 15 years old or with a polytraumatic, tumorous, or infectious pathology were excluded. The modified Ranawat method (MRM) and the Redlund-Johnell method (RJM) were used to obtain radiographic measurements of basilar invagination preoperatively, subacute postoperatively, and at 3-month and last follow-up. Visual analogue scale, Neck Disability Index, and Japanese Orthopedic Association (JOA) scores were also assessed. Correlations between MRM and RJM measurements and clinical outcomes were evaluated. Mean age of patients was 59.9 ± 16.5 years, mean body mass index was 23.5 ± 4.6 kg/m2, and mean follow-up was 37.9 ± 23.8 months. Postoperative radiologic measurements increased about 36% of preoperative radiologic measurements. Subsidence at the C1-2 joint occurred in most patients at 3 months postoperatively, but clinical outcomes did not deteriorate. JOA scores were linearly correlated with percentage increases in both radiologic measurements subacute postoperatively (P<0.05), but this significance was not maintained until the last follow-up. Occipital numbness and neuralgia were most common postoperative complications. One case of neurovascular injury and 3 cases of postoperative dysphagia occurred postoperatively. The subacute postoperative neurological outcomes of BI patients are significantly related to the amount of vertical reduction.

Surgical treatment of type II odontoid fractures in elderly patients: a comparison of anterior odontoid screw fixation and posterior atlantoaxial fusion using the Magerl-Gallie technique.

This single-centre retrospective study compared anterior odontoid screw fixation and posterior atlantoaxial fusion in the surgical treatment of type II B odontoid fractures according to Grauer in elderly patients. Between 1994 and 2014, 133 consecutive patients above 60years presenting with type II B odontoid fracture were treated surgically in our department. They were divided retrospectively into two groups. Group A included 47 patients in whom anterior odontoid screw fixation was performed. Group B with 86 patients underwent posterior atlantoaxial fusion. The clinical and radiological data were analysed. Any reoperation during the follow-up was recorded and evaluated. The mean age in group A (74.19years) was significantly less than in group B (78.16years). The mean operative time in group A (64.5min) was significantly shorter than in group B (116min). Again, the mean amount of blood loss in group A (79ml) was significantly less than in group B (379ml). The mean postoperative hospital stay was significantly shorter in group A (17.4days) than in group B (30days). The mean follow-up was 29.3months in group A and 32months in group B. The rate of pseudoarthrosis was significantly higher in group A (25.5%) than in group B (3.5%). Furthermore, the need for revision surgery was significantly increased in group A (23.4%) than in group B (10.47%). Odontoid screw fixation is a less invasive surgery for type II B odontoid fractures in elderly patients. However, posterior atlantoaxial fusion provides a superior surgical outcome regarding fracture healing and the need for surgical revisions. These slides can be retrieved under Electronic Supplementary Material.

Use of Recombinant Human Bone Morphogenetic Protein-2 at the C1-C2 Lateral Articulation without Posterior Structural Bone Graft in Posterior Atlantoaxial Fusion in Adult Patients

Posterior atlantoaxial fusion is an important armamentarium for neurosurgeons to treat several pathologies involving the craniovertebral junction. Although the potential advantages of recombinant human bone morphogenetic protein-2 (rhBMP-2) are well documented in the lumbar spine, its indication for C1-C2 fusion has not been well characterized. In our institution, we apply rhBMP-2 to the C1-C2 joint either alone or with hydroxyapatite, locally harvested autograft chips, and/or morselized allogenic bone graft for selected cases-without conventional posterior structural bone graft. We report the clinical outcomes of the surgical technique to elucidate its feasibility. We performed a single-center, retrospective review of data from 2008 to 2016 and identified 69 patients who had undergone posterior atlantoaxial fusion with rhBMP-2. The clinical records of these patients were reviewed, and the baseline characteristics, operative data, and postoperative complications were collected and statistically analyzed. The average age of the 69 patients was 60.8± 4.5 years, and 55.1% were women. With an average follow-up period of 21.1 ± 4.2 months, the C1-C2 fusion rate was 94.3% (65 of 69), and the average time to fusion was 11.4 ± 2.6 months (range, 5-23). The overall reoperation rate was 10.1% (7 of 69), with instrumentation failure in 7 patients (10.1%), adjacent segment disease in 2 (2.9%), and postoperative dysphagia and dyspnea in 2 patients (2.9%). No ectopic bone formation or soft tissue edema developed. Although retrospective and from a single center, our study has shown that rhBMP-2 usage at the C1-C2 joint without posterior structural bone grafting is a safe and reasonable surgical option.

Identifying Factors Predictive of Atlantoaxial Fusion Failure in Pediatric Patients: Lessons Learned From a Retrospective Pediatric Craniocervical Society Study.

Multicenter retrospective cohort study with multivariate analysis. To determine factors predictive of posterior atlantoaxial fusion failure in pediatric patients. Fusion rates for pediatric posterior atlantoaxial arthrodesis have been reported to be high in single-center studies; however, factors predictive of surgical non-union have not been identified by a multicenter study. Clinical and surgical details for all patients who underwent posterior atlantoaxial fusion at seven pediatric spine centers from 1995 to 2014 were retrospectively recorded. The primary outcome was surgical failure, defined as either instrumentation failure or fusion failure seen on either plain x-ray or computed tomography scan. Multiple logistic regression analysis was undertaken to identify clinical and technical factors predictive of surgical failure. One hundred thirty-one patients met the inclusion criteria and were included in the analysis. Successful fusion was seen in 117 (89%) of the patients. Of the 14 (11%) patients with failed fusion, the cause was instrumentation failure in 3 patients (2%) and graft failure in 11 (8%). Multivariate analysis identified Down syndrome as the single factor predictive of fusion failure (odds ratio 14.6, 95% confidence interval [3.7-64.0]). This retrospective analysis of a multicenter cohort demonstrates that although posterior pediatric atlantoaxial fusion success rates are generally high, Down syndrome is a risk factor that significantly predicts the possibility of surgical failure. 3.

Posterior atlantoaxial fusion with a screw-rod system: Allograft versus iliac crest autograft

ObjectiveTo compare the effectiveness of allograft and iliac crest autograft in atlantoaxial fusion. Patients and MethodsBetween January 2012 and December 2012, 41 consecutive patients underwent posterior atlantoaxial fusion with a screw-rod fixation system in our spine center. The choice to use allograft or iliac crest autograft was made by the patient himself or herself after being informed about the advantages and disadvantages of both methods. In the allograft group, we used mixed material of morcellized demineralized freeze-dried bone allograft and local autograft for posterior atlantoaxial fusion. In the autograft group, we used the morcellized iliac crest autograft for fusion. Patients underwent regular follow up including CT scans and dynamic radiographs 6 months postoperatively and every 6 months thereafter until study completion or confirmation of fusion. ResultsTwenty-four patients underwent posterior atlantoaxial fusion with allograft, and 17 underwent fusion with autograft. All patients were followed up for at least 24 months. At the final follow-up visit, only two (8.3%) patients in the allograft group had confirmed posterior bony fusion on CT imaging while 15 (88.2%) patients in the autograft group had confirmed posterior bony fusion. None of the 41 patients had movement on the dynamic radiographs. ConclusionsAllograft is not reliable for posterior atlantoaxial fusion even with the rigid internal fixation of modern constructs. Autograft remains the first choice for atlantoaxial fusion despite the donor-site morbidity. The assessment of fusion based on a lack of movement on dynamic radiographs is not reliable. The confirmation of fusion should be based on the presence of bridging bone on CT imaging.

C1-C2 Pedicle Screw Fixation for Atlantoaxial Dislocation in Pediatric Patients Younger than 5 Years: A Case Series of 15 Patients.

C1-C2 pedicle screw fixation has become popular for providing excellent bony purchase and avoiding neurovascular complications. However, it may be technically challenging in children. The objective of this study is to investigate the safety and efficacy of C1-C2 pedicle screw fixation for atlantoaxial dislocation (AAD) in pediatric patients younger than 5 years and to evaluate the preliminary clinical and radiographic results. During a 7-year period, 15 patients with a mean age of 3.4 years (range, 2-5 years) underwent C1-C2 pedicle screw fixation for AAD; at least 1 C1 pedicle screw was incorporated as part of the posterior atlantoaxial fusion construct. The cause, surgical technique, instrumentation, and clinical and radiographic results were analyzed. Five patients had preoperative neurologic deficits and no neurovascular injury occurred during surgery. Anterior release using a retropharyngeal approach was performed in 4 cases. Fixation of 55 C1 and C2 pedicle screws was performed successfully without neurovascular complications. Anatomic and partial reductions occurred in 12 and 3 cases, respectively. Solid fusion was achieved in 14 patients (96.9%) during a mean follow-up of 37.6 months (range, 12-111 months). Two patients (13%) experienced complications: one had prolonged immobilization for a loose C1 pedicle screw, and one had unintended fusion caused by allograft absorption. All patients showed radiographic stability and symptom resolution. C1-C2 pedicle screw fixation for AAD is safe and effective even in children younger than 5 years.