Direct Posterior Reduction Research Articles

Correlation Among Syrinx Resolution, Cervical Sagittal Realignment, and Surgical Outcome After Posterior Reduction for Basilar Invagination, Atlantoaxial Dislocation, and Syringomyelia.

The correlation among syrinx resolution, occipitoaxial sagittal alignment, and surgical outcome in long-term follow-up seems to have not been clarified. To further explore the relationship between the syrinx resolution and occipitoaxial realignment after posterior reduction and fixation in basilar invagination (BI)-atlantoaxial dislocation (AAD) patients with syringomyelia. A continuous series of 32 patients with BI-AAD and syringomyelia who received direct posterior reduction met the inclusion criteria of this study. Their clinical and imaging data were analyzed retrospectively. Before surgery and at the last follow-up, we used the Japanese Orthopedic Association (JOA) score and the Neck Disability Index (NDI) to assess the neurological status, respectively. The Pearson correlation coefficient and multiple stepwise regression analysis were used to explore the relevant factors that may affect surgical outcomes. There were significant differences in atlantodental interval, clivus-axial angle, occiput-C2 angle (Oc-C2A), cervicomedullary angle (CMA), subarachnoid space (SAS) at the foramen magnum (FM), syrinx size, NDI, and JOA score after surgery compared with those before surgery. ΔCMA and the resolution rate of syrinx/cord as relevant factors were correlated with the recovery rate of JOA (R 2 = 0.578, P < .001) and NDI (R 2 = 0.369, P < .01). What's more, ΔSAS/FMD (SAS/FM diameter) and ΔOc-C2A were positively correlated with the resolution rate of syrinx/cord (R 2 = 0.643, P < .001). With medulla decompression and occipital-cervical sagittal realignment after posterior reduction and fusion for BI-AAD patients with syringomyelia, the structural remodeling of the craniovertebral junction and occipitoaxial realignment could contribute to syringomyelia resolution.

Usefulness of 3D Printed Models in the Management of Complex Craniovertebral Junction Anomalies: Choice of Treatment Strategy, Design of Screw Trajectory, and Protection of Vertebral Artery

To evaluate the usefulness of 3-dimensional (3D) printed models as an aid for the treatment of complex CVJ anomalies. 3D printed models were fabricated for 21 patients with complex CVJ anomalies, including vertebral artery anomaly, thin C2 pedicle, vertical atlantoaxial facet joint, or rotational dislocation combined with atlantoaxial dislocation and basilar invagination. Preoperative planning, surgical simulation, and intraoperative reference were achieved using the 3D model during the surgical treatment. The usefulness of 3D printed models, and postoperative clinical and radiological outcomes were assessed. Direct posterior reduction and atlantoaxial fixation were achieved in 19 patients. Transoral odontoidectomy followed by posterior fixation was implemented for 2 patients with vertical facet joint and rotational dislocation. All screws were safely inserted with no complication, and 90% patients achieved a >60% reduction of both horizontal and vertical dislocation. Clinical symptoms improved in all patients, with the averaged Japanese Orthopedic Association scores increasing from 11.14 to 14.43 (P < 0.01). The patient-specific 3D printed model would be an effective tool for evaluation of the reducibility of the atlantoaxial dislocation and basilar invagination, decision making in choosing the optimal surgical approach and way of fixation, and precise placement of the screw while protecting the vertebral artery and spinal cord. The risk of neurovascular injury was minimized, and encouraging outcomes were achieved with the aid of this technique.

The Value and Limitation of Cervical Traction in the Evaluation of the Reducibility of Atlantoaxial Dislocation and Basilar Invagination Using the Intraoperative O-Arm

To assess the value and limitation of cervical traction in the evaluation of the reducibility of atlantoaxial dislocation (AAD) and basilar invagination (BI) using the intraoperative O-arm. A total of 22 patients with hyperextensive, irreducible AAD were included. The cervical traction test under general anesthesia was performed, and the degree of reduction was evaluated using the O-arm before the operation started. The traction effects both vertically and horizontally were evaluated. All cases then underwent modified direct posterior reduction and fixation. Clinical outcomes were evaluated using the Japanese Orthopaedic Association (JOA) scale. Radiologic measurements included the anterior atlantodental interval, the distance of odontoid tip above Chamberlain line, and the clivus-canal angle. Magnetic resonance imaging signal changes, size of syringomyelia, and the space ventral to medulla also were used to evaluate the postoperative reduction result. After the cervical traction test, 7 patients achieved incomplete reduction, 5 achieved only vertical reduction, 6 achieved only horizontal reduction, and 4 achieved complete reduction in both horizontal and vertical orientations as assessed by the O-arm. All patients underwent a direct reduction technique. The mean JOA score increased from 11.1 to 14.5. Complete reduction of AAD and BI were achieved in 19 patients (86.4%), with partial reduction achieved in 3 (13.6%). Sufficient cerebrospinal fluid space anterior to the medulla with improved JOA score was achieved in the 3 partially reduced patients. With the innovations of direct posterior reduction techniques, cervical traction under anesthesia may not sufficiently predict the reducibility of BI and AAD. Cervical traction still plays an important role during the direct posterior reduction procedure.

Effectiveness of posterior reduction and fixation in atlantoaxial dislocation: a retrospective cohort study of 135 patients with a treatment algorithm proposal.

Surgical procedures on atlantoaxial dislocation remain controversial. The aim of this observational retrospective study was to investigate the treatment algorithm of surgical procedures. According to CT and intraoperative evaluation during direct posterior reduction, 135 AAD cases were categorized into three groups: Group I: reducible dislocation; Group II: irreducible dislocation (Group IIa: effective decompression achieved after posterior reduction; Group IIb: no effective decompression after posterior reduction); and Group III: fixed dislocation. Group III presented with extensive bony fusions. Group I and Group IIa were treated with direct posterior reduction and fixation. Group IIb underwent posterior fixation and transoral odontoidectomy. Group III underwent transoral odontoidectomy alone. Japanese Orthopedic Association scores (JOA) were assessed to evaluate clinical status before and 6, 12months after surgery. Our study included 118 Group I cases, 16 Group II cases (Group IIa: 11 cases; Group IIb: 5 cases), and one Group III case. Follow-up ranged from 12 to 36months. Anatomic atlantoaxial reduction was achieved in 118 of 135 patients (87.4%). Clinical improvements were seen in 96.3% (130/135) all the patients. Solid atlantoaxial fusion was shown in 134 patients. Secondary outcome: The overall complication rate was 3.7% (5/135). For Group I, the mean postoperative 6-month JOA was 14.5 versus 12.2 in preoperative patients (paired Student's t test, P < 0.01). This article proposes a clinical procedure that assists with therapeutic decision making and indicates the severity and difficulty of reduction of the atlantoaxial joint. These slides can be retrieved under Electronic Supplementary Material.

Vertico-horizontal atlantoaxial index (VHAI): A new craniovertebral radiographic index

ObjectiveThe purpose of this study was to develop a new index that can reliably quantify the reduction of basilar invagination with atlantoaxial dislocation. Patients and methodsBetween May 2012 and September 2017, 40 patients with congenital basilar invagination and atlantoaxial dislocation as well as 100 sex-and age-matched control subjects were recruited for this study. All patients underwent direct posterior reduction and fixation. Mid-sagittal computerized tomography scan films were obtained before and after surgery as well as the vertico-horizontal atlantoaxial index (VHAI) was measured in all patients -before and after surgery- and controls. Additionally, the pre-and postoperative Japanese Orthopedic Association (JOA) scores, Nurick grading, European Myelopathy Score (EMS) and Prolo Scale score were used to evaluate the cervical myelopathy. ResultsThe mean follow-up was 24.75 months with a range of 6–60 months. The mean value of VHAI in the control group was 87.86 ± 24.98 mm2, while the mean values of VHAI before and after surgery were 209.45 ± 96.80 mm2 and 95.08 ± 66.95 mm2, respectively. Additionally, in the patient group, a negative correlation was observed between JOA, EMS, Prolo Scale scores and VHAI. On the other hand, a positive correlation was found between the Nurick grading and VHAI. ConclusionThe VHAI can be an excellent measurement tool to evaluate the reduction of basilar invagination with atlantoaxial dislocation. There was a negative correlation between VHAI and JOA, EMS and Prolo Scale scores, and a positive correlation with Nurick grading; which indicates the effectiveness of this index.

Is anterior release and cervical traction necessary for the treatment of irreducible atlantoaxial dislocation? A systematic review and meta-analysis.

To compare the clinical and radiographic outcomes of irreducible atlantoaxial dislocation (IAAD) treated with posterior fusion after anterior release and direct posterior reduction of the dislocation. Online databases were searched for articles describing IAAD published from 1999 to 2015. Five studies (105 patients) described treatment with posterior fusion after periodontoid tissue release, and five studies (113 patients) described treatment with direct posterior reduction of the dislocation. The primary outcomes in this study were the complete reduction rate, Japanese Orthopedic Association score, perioperative morbidity, perioperative mortality, complications, vascular injury, and infection. Standard meta-analysis techniques were used to compare the outcomes. Of 319 citations examined, 10 articles involving 218 participants were eligible. Overall, there were no significant differences between the anterior release and posterior fixation (ARPF) group and direct posterior reduction and fixation (DPRF) group in the complete reduction rate, neurologic recovery rate, perioperative morbidity, perioperative mortality, vascular injury, or infection. However, the complication rate in the DPRF group was much lower than that in the ARPF group. Compared with posterior fusion after anterior release, direct posterior reduction of the dislocation showed no significant differences in terms of the complete reduction rate, neurologic recovery rate, or fusion rate; however, it was a simpler process associated with less surgical trauma and a shorter operation time. Because of the limitations of the small sample in this study, whether direct posterior reduction of the dislocation is more effective and safer than posterior fusion after anterior release remains unclear. III. These slides can be retrieved under Electronic Supplementary Material.

Focusing on the delayed complications of fusing occipital squama to cervical spine for stabilization of congenital atlantoaxial dislocation and basilar invagination

ObjectivesOccipito-cervical(OC) fusion is often practiced for congenital atlanto-axial dislocation (CAAD) and basilar invagination (BI) with claims of good long term outcome. Little has been discussed about the delayed complications following fusing occipital squama to cervical spine (OC fusion). We have described and analyzed delayed complications with OC fusion in our patients that helps us understand the underlying dynamics and biomechanics. Patients and methodsTwenty seven patients of CAAD and BI underwent OC fusion (between 2008 and 11) after transoral odontoidectomy or direct posterior reduction with OC distraction. OC fusion was achieved using either sublaminar wiring or with precurved rods and screws or contoured loop. One patient was referred after OC fusion with contoured loop and wires with additional C1 laminectomy. The outcome (>12months) and delayed complications in these patients were analyzed. ResultsFive types of delayed complications were noticed in 6 of the 28 patients who underwent OC fusion. Five of 6 patients were adults. Vertical redislocation with posterior midline fusion (n=2), adjacent level angular listhesis (n=1) and swan neck deformity (n=1) was seen in cases of OC fusion with sublaminar wires alone. Progressive C1 dislocation was seen in the lone patient who was referred after OC fusion with loop and wires. Vertical and angular dislocation was seen in 1 patient of OC fusion with precurved rod and screws. ConclusionProgressive redislocation and adjacent level dislocation are delayed complications seen after OC2 fusion. These complications are more often seen in adults, especially with sublaminar wiring/semi rigid OC fixation.

Comprehensive drilling of the C1-2 facets to achieve direct posterior reduction in irreducible atlantoaxial dislocation.

The cause of irreducibility in irreducible atlantoaxial dislocation (AAD) appears to be the orientation of the C1-2 facets. The current management strategies for irreducible AAD are directed at removing the cause of irreducibility followed by fusion, rather than transoral decompression and posterior fusion. The technique described in this paper addresses C1-2 facet mobilization by facetectomies to aid intraoperative manipulation. Using this technique, reduction was achieved in 19 patients with congenital irreducible AAD treated between January 2011 and December 2013. The C1-2 joints were studied preoperatively, and particular attention was paid to the facet orientation. Intraoperatively, oblique C1-2 joints were opened widely, and extensive drilling of the facets was performed to make them close to flat and parallel to each other, converting an irreducible AAD to a reducible one. Anomalous vertebral arteries (VAs) were addressed appropriately. Further reduction was then achieved after vertical distraction and joint manipulation. Adequate facet drilling was achieved in all but 2 patients, due to VA injury in 1 patient and an acute sagittal angle operated on 2 years previously in the other patient. Complete reduction could be achieved in 17 patients and partial in the remaining 2. All patients showed clinical improvement. Two patients showed partial redislocation due to graft subsidence. The fusion rates were excellent. Comprehensive drilling of the C1-2 facets appears to be a logical and effective technique for achieving direct posterior reduction in irreducible AAD. The extensive drilling makes large surfaces raw, increasing fusion rates.

Factors influencing feasibility of direct posterior reduction in irreducible traumatic atlantoaxial dislocation secondary to isolated odontoid fracture

Introduction. Direct posterior reduction by intraoperative manipulation of joints for irreducible traumatic atlantoaxial dislocation (IrTAAD) has gained acceptance in the recent past. However, factors determining its feasibility have not been elucidated. Our study aims to examine the clinico-radiological factors predicting feasibility of direct posterior reduction in IrTAAD secondary to isolated odontoid fracture, in an attempt to differentiate the “truly irreducible” from those “deemed irreducible.” Materials and methods. The onset and progression of neck pain and myelopathy was studied in 6 patients of IrTAAD with fracture odontoid, which failed to reduce despite traction. The dynamic X-rays and computed tomography (CT) scans of craniovertebral junction, along with the vertebral artery angiogram were studied to look for the slightest mobility, interface of fractured fragments, malunion, callous, and relationship of the C1–2 facets and vertebral artery. Results. All 6 patients had progressive worsening of neck pain. Three patients had progressive myelopathy. Three patients presented 6 months after trauma. Radiology showed type-II fracture with IrTAAD (anterolisthesis in 5 and retrolisthesis with lateral dislocation in 1) and locked facets in all. X-rays showed doubtful callous formation in 3 patients and CT confirmed non-union. Three patients showed angular movement on dynamic X-rays despite irreducibility and locked facets. Angiogram showed thrombosis of vertebral artery in one patient. Intraoperative reduction could be achieved in all 6 patients with good clinico-radiological outcome. Conclusion. Worsening pain, progression of myelopathy, some movement on dynamic X-rays, a malunion ruled out on CT scan, and the presence of locked facets make direct posterior reduction feasible in patients with IrTAAD. The difficulty increases in remote fractures due to fibrosis around the dislocated joints. The role of the CT angiogram, in defining the relationship of Vertebral artery (VA) to the dislocated facets, and in determining the extent of VA injury, is vital. Preoperative detection of VA injury reduces the chance of intraoperative reduction, especially if only unilateral joint approach is planned.

Missing the 'window' might shut the light forever: Central retinal artery occlusion following spine surgery.

Missing the 'window' might shut the light forever: Central retinal artery occlusion following spine surgery.

Individualized 3D printing model-assisted posterior screw fixation for the treatment of craniovertebral junction abnormality

Objective To study the method and effect of individualized 3 D printing model-assisted posterior screw fixation for the treatment of craniovertebral junction abnormality.Methods 31 patients with craniovertebral junction abnormalities diagnosed by CT and MRI were retrospectively analyzed in neurosurgical department of Guizhou Provincial People's Hospital.First,made a 3D printing model of craniovertebral junction by 31 printing technology,then simulated screw insertion and fixation operation on the model to obtain the individual screw insertion data to assist the real operation,at last implemented one-stage posterior decompression operation combined with internal fixation.Results 25 of 31 patients with craniovertebral junction abnormalities successfully underwent the posterior screw fixation operation assisted by individual 3D printing models.Preoperative CT evaluation suggested that the operations of axial pedicle screw placement were planned for 2 cases,but 3D printing models revealed the operations could not be implemented; and 3 cases were unsuitable for axial pedicle screw placement,but 3D printing models revealed the operation could be accomplished by an isthmus part screw insertion of axial pedicle.Postoperative follow-up time was 3-28 months,with an average of 13.9 months.Postoperative JOA scores of the patients underwent posterior screw fixation treatment were significantly increased,with significant differences (P =0.000).Postoperative MRI and CT scanning of 24 cases with craniovertebral junction abnormalities combined with atlantoaxial dislocation revealed that the dislocations were completely reduced in 19 cases and incompletely reduced in 5 cases.Postoperative ADI was significantly reduced,CMA was significantly increased,medullary ventral compression obviously alleviated or disappeared and there was a significant statistical difference (P =0.000).There were no deaths during operation,but dyspnea occurred in 2 cases.Conclusion Posterior screw fixation operation assisted by individualized 3D printing model can improve the success rate and safety of screw insertion,and effectively protect the vertebral artery avoiding damage,which suggests this technique is very useful for the new comer and worth popularizing; there is a good short-term efficacy for direct posterior distraction reduction treatment of atlantoaxial dislocation. Key words: 3D printing models; Craniovertebral junction abnormality; Atlantoaxial dislocation; Internal fixation

Direct Posterior Reduction and Fixation

Direct Posterior Reduction and Fixation

Direct Posterior Reduction and Fixation for the Treatment of Basilar Invagination With Atlantoaxial Dislocation

To report the surgical technique and clinical results for the treatment of basilar invagination (BI) with atlantoaxial dislocation (AAD) by direct posterior reduction and fixation using intraoperative distraction between the occiput and C2 pedicle screws. From May 2004 to June 2008, 29 patients who had BI with AAD were surgically treated in our department. Pre- and postoperative dynamic cervical x-rays, computed tomographic scans, and 3-dimensional reconstruction views were performed to assess the degree of dislocation. Ventral compression of the cervicomedullary junction was evaluated by magnetic resonance imaging. For all patients, reduction of the AAD was conducted by intraoperative distraction between the occiput and C2 pedicle screws using a direct posterior approach. Follow-up ranged from 6 to 50 months in 28 patients. Clinical symptoms improved in 26 patients (92.9%) and were stable in 2 patients (7.1%) without postoperative deterioration. Radiologically, complete or more than 50% reduction was achieved in 27 of 28 patients (96.4%). In 1 patient, the reduction was less than 50% because the direction of the facets on 1 side of the C1-C2 joint was vertically oriented, instead of horizontal. Overall, good decompression and bone fusion were shown on postoperative magnetic resonance imaging, computed tomography, or x-ray scans for all patients. There was 1 death in the series because of basilar artery thrombosis 1 week after the operation. The direct posterior distraction technique between occiput and C2 pedicle screws is an effective, simple, fast, and safe method for the treatment of BI with AAD. Transoral odontoidectomy and cervical traction for the treatment of BI with AAD should be reconsidered.

Direct posterior reduction and fixation for the treatment of idiopathic atlantoaxial dislocation

Objective To report our surgical technique and results in the treatment of idiopathic atlantoaxial dislocation (IAAD) by using direct posterior reduction and fixation, without odontoidectomy and cervical traction. Methods Twenty patients of IAAD were operated on during May 2004 to December 2007. Before and after the operation, CT and MRI were used to measure and evaluate the degree of dislocation and neural compression. Two different screw fixation techniques were used depending on whether there was C1 assimilation; C1 lateral mass - C2 pedicle screws fixation was used for patients without C1 assimilation, otherwise, C2 pedicle -Occiput scews fixation was used. Intraoperative reduction was achieved by compressing the C2 spinous process anteriorly, or by distraction between C2 pedicle and occiput screws. Results All 20 patients were followed up from 6 to 48 months, among them, there was one death due to basilar artery thrombosis one week after the operation; in all the other 19 patients, symptoms were relieved markedly. All the postoperative radiological measurements were improved significantly (paired t test, in all groups, P < 0. 01 ). MRI showed good decompression of spinal cord and oblongata medulla in all 19 cases (CMA, P < 0.01 ); in 5 patients associated with Chiari's malformation and syringomyelia, syrinx was significantly shrinked in all patients. Conclusion Using posterior approach and intraoperative reduction and fixation technique, rather than anterior decompression through transoral odontoidectomy, for the treatment of IAAD is an effective, simple and relatively safe method. Key words: Atlantoaxial dislocation; Basilar invagination; Reduction; Fixation

P-4-466 - Multi-level anterior cervical arthrodesis and instrumentation: Outcome analysis

Occipito-cervical(OC) fusion is often practiced for congenital atlanto-axial dislocation (CAAD) and basilar invagination (BI) with claims of good long term outcome. Little has been discussed about the delayed complications following fusing occipital squama to cervical spine (OC fusion). We have described and analyzed delayed complications with OC fusion in our patients that helps us understand the underlying dynamics and biomechanics.Twenty seven patients of CAAD and BI underwent OC fusion (between 2008 and 11) after transoral odontoidectomy or direct posterior reduction with OC distraction. OC fusion was achieved using either sublaminar wiring or with precurved rods and screws or contoured loop. One patient was referred after OC fusion with contoured loop and wires with additional C1 laminectomy. The outcome (> 12 months) and delayed complications in these patients were analyzed.Five types of delayed complications were noticed in 6 of the 28 patients who underwent OC fusion. Five of 6 patients were adults. Vertical redislocation with posterior midline fusion (n = 2), adjacent level angular listhesis (n = 1) and swan neck deformity (n = 1) was seen in cases of OC fusion with sublaminar wires alone. Progressive C1 dislocation was seen in the lone patient who was referred after OC fusion with loop and wires. Vertical and angular dislocation was seen in 1 patient of OC fusion with precurved rod and screws.Progressive redislocation and adjacent level dislocation are delayed complications seen after OC2 fusion. These complications are more often seen in adults, especially with sublaminar wiring/semi rigid OC fixation.