Congenital Atlantoaxial Dislocation Research Articles

A Method to Evaluate the Reduction Difficulty of Atlantoaxial Dislocation Based on Computed Tomography Quantitative Analysis

To evaluate the difficulty of reduction of congenital atlantoaxial dislocation (AAD) with/without os odontoideum or basilar invagination (BI) based on CT quantitative analysis. From March 2018 to December 2022，the CT features of 108 patients with AAD with/without os odontoideum or BI were analyzed. Quantitative scores were defined according to imaging features, including: sloping of the lateral mass, osteophyte between the lateral mass joint, ball-and-socket deformity of the lateral mass joint, vertical interlocking of the lateral mass joint, callus between the lateral mass joint, atlanto-odontoid joint hyperplasia, blocking or fusion. Grades were as follows according to the sum of points of the atlanto-odontoid joint and lateral mass joints: Grade I, 0-1 points; Grade Ⅱ, 2-3 points; Grade Ⅲ, 4-6 points; and Grade IV, 7-10 points. After one week of bidirectional cervical traction, CT scans were performed and atlantodens interval (ADI) and vertical distance from dens to Chamberlain line (VDDC) were measured. The vertical reduction rate, horizontal reduction rate and overall reduction rate of atlantoaxial dislocation were calculated. The after-traction VDDC values were significantly reduced than that of pre-traction, including grade I, II, III and IV. The overall reduction rates were respectively 85.1±11.8%, 65.8±8.3%, 45.0±8.5% and 38.4±13.0% after one-week of bi-directional cervical traction. The CT quantitative score system is an effective non-invasive evaluation of judging the reduction difficulty of AAD with/without os odontoideum or BI.

Surgical, Clinical, and Radiological Outcomes Analysis of Craniovertebral Junction Anomalies Cases: An Institutional Experience.

Objective The aim of this study was to evaluate the clinical and radiological outcomes analysis of craniovertebral junction (CVJ) anomalies cases. Materials and Methods Retrospective analysis of 43 CVJ anomalies cases, which were surgically managed at Uttar Pradesh University of Medical Sciences, Saifai, Etawah, Uttar Pradesh, India, from period between June 2015 and June 2019. They were analyzed for age, sex, clinical characteristics, radiological diagnosis, and treatment given. Patient's clinical and radiological status was assessed pre- and postoperatively during time of discharge and at 6 months of follow-up. For clinical assessment we used visual analogue scale (VAS) and Nurick grading system. Radiological assessment was done by atlantodental interval (ADI), craniobasal angle, and craniometric lines. Overall outcomes were depicted as favorable, stabilized, and mortality at 6 to 18 months (mean 12.69 ± 3.77) of follow-up. Results The age range of our cases was 7 to 71 years (mean 29.93 ± 17.39). Male-to-female ratio was 2.91:1. Majority of the cases were presented with neck pain ( n = 38; 88.37%), motor weakness ( n = 35; 81.40%), and sensory deficits ( n = 25; 58.14%). Congenital atlantoaxial dislocation ( n = 31; 72.09) was the most common CVJ anomaly. Clinically, there were significant improvements in VAS ( p = 0.001) and Nurick grade ( p = 0.007) postoperatively. Radiologically, ADI ( p = 0.003) had decreased, clivus canal angle ( p = 0.005) become less acute, and odontoid process ( p = 0.003 for McRae's line) goes downwards in postoperative period. Bony fusion was achieved in 41 (95.35%) cases. Out of 43, 73% cases had favorable outcomes, 21% were stabilized, and mortality was seen in 2.33% cases at 6 months (mean ± standard deviation = 12.69 ± 3.77) of follow-up. Conclusion Proper preoperative evaluation and selection of individualized surgical technique was the key for excellent clinical and radiological outcomes with minimal complications.

Prediction of the functional and radiological outcome on the basis of independent factors with special emphasis on the use of 3D printed models in craniovertebral junction surgery.

Background: The aim of the study was to evaluate the advantage of performing planned surgery using customized three-dimensional (3D) printed models versus performing surgery without using 3D printed models in patients with craniovertebral junction (CVJ) anomalies and traumatic CVJ fractures and dislocations.Methods: Forty-two patients with CVJ anomalies, who were planned for operative intervention in the Department of Neurosurgery at SMS Hospital from March 2019 to February 2021, were randomly divided into two groups and analyzed. First group was operated after rehearsal on a customized 3D printed model whereas the second group underwent operative intervention without the rehearsal of surgery on the 3D printed model.Results: Forty-two patients were enrolled for the study. Twenty-five of these patients had developmental CVJ anomalies, 16 had post traumatic Atlantoaxial dislocation (AAD), and one had congenital AAD. Twenty-three patients underwent surgical intervention using 3D printed models and 19 without using 3D printed models. The outcome in the two groups was compared using modified Japanese orthopedic association score (mJOA), recovery rate, incidence of complications such as screw malposition, postoperative neurological deterioration, vertebral artery (VA) injury, and radiological improvement based on Atlanto-Dental interval, the distance of the tip of dens from Wackhenheims clivus canal line, and the distance of tip of dens from the Chamberlain’s line. The improvement in mJOA score postoperatively was found to be statistically significant in study group (P < 0.001) as compared to control group (P = 0.06). Recovery rate was better in study group than in control group (P = 0.023). In study group, the incidence of screw malposition and VA injury was lower than control group. Three patients deteriorated neurologically postoperatively in the control group and none in the study group. The average improvements in the radiological parameters were found to be better in study group as compared to control group postoperatively.Conclusion: The authors conclude that 3D printed models are extremely helpful in analyzing joints and VA anatomy preoperatively and are helpful in unmasking any abnormal bony and vascular anatomy effectively, making the surgeon confident about the placement of the screws intraoperatively. These 3D models help in intraoperative error minimization with better neurological outcomes in postoperative period. In our opinion, these models should be included as a basic investigation tool in patients of CVJ abnormalities. The models also offer other advantages such as preoperative simulation, teaching modules, and patient education.

105. Clinical outcomes of C2 nerve root sacrifice and the feasibility of its preservation in patients with congenital atlantoaxial instability

<h3>BACKGROUND CONTEXT</h3> Posterior C1-C2 fusion is a widely used fixation technique for atlantoaxial dislocation (AAD). The C2 ganglion is a restricting factor to easy access of C1-C2 joints, and placement of C1 lateral mass screws. Both intentional C2 nerve root sectioning as well as its preservation have been described and are still debatable. The associated complications and outcomes have been less studied, particularly in congenital AAD. <h3>PURPOSE</h3> To study clinical outcome after C2 nerve root sectioning as well as the feasibility of its preservation in AAD patients. <h3>STUDY DESIGN/SETTING</h3> Retrospective study/ tertiary care center. <h3>PATIENT SAMPLE</h3> This study included 190 patients who underwent posterior C1-C2 fusion for congenital AAD. <h3>OUTCOME MEASURES</h3> C2 nerve-related dysfunction; feasibilty of nerve root preservation. <h3>METHODS</h3> This is a retrospective study of 190 patients who underwent posterior C1-C2 fusion for congenital AAD using C1 lateral mass screws. The decision to cut or preserve C2 nerve root was dependent on preoperative radiology and intraoperative suitability of its preservation. Patients were followed-up at periodic intervals and questioned about C2 nerve-related dysfunction. <h3>RESULTS</h3> Complex C1-C2 morphology with highly deformed joints was seen in 139 patients. In 178 patients, the C2 nerve root was sectioned. Postoperative numbness, paresthesia and dysesthesia were present in 30.3%, 21.9% and 19.1% patients respectively. However, the symptoms were bothersome in none. They neither required medications nor disturbed the daily activities of patients. Noticeably, 9 patients (5.1%) developed non-healing occipital ulcers; most needed surgical intervention in the form of a flap cover/skin graft. C2 nerve root preservation is feasible with robust inferior C1 lateral mass and normal sized ganglion. In patients with C1-occipital condyle hypoplasia, highly oblique joints, incurved occiput, pseudofacets and anomalous vertebral artery, its preservation is technically difficult. <h3>CONCLUSIONS</h3> Though C2 nerve root sectioning did not disable the quality of life in many, a subset of patients was prone for neuropathic ulcers. Hence, its preservation should be attempted whenever feasible. It may be possible to preserve it in less complex anomalies/favorable anatomy. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Biomechanical investigation of intra-articular cage and cantilever technique in the treatment of congenital basilar invagination combined with atlantoaxial dislocation: a finite element analysis.

Biomechanical effect of posterior intra-articular cages and cantilever technique on the congenital basilar invagination (BI) combined with atlantoaxial dislocation (AAD) was investigated and evaluated using finite element (FE) analysis. A 3D nonlinear occipitocervical segment C0-C3 FE models of congenital BI and AAD was established. Then, the FE model treated with C2 pedicle screw and occipital plate fixation coupled with intra-articular cages (Cage + C2PS + OP) was compared to that without intra-articular cages (C2PS + OP). The range of motion (ROM) of C0C1-C2 and the maximum von Mises stresses (MVMS) on the intra-articular cages, screw-plate system, and C2 endplate were calculated and compared to furtheranalyze the stability of atlantoaxial joint and assess the collapse and fracture risks of intra-articular cages and screw-plate system. ROM of C0C1-C2 segment was reduced by 57.58%, 63.33%, 78.18%, and 75.90%, and the peak stresses of C2 pedicle screw and occipital plate were decreased by 84.86%, 72.90%, 73.24%, and 84.90% and 78.35%, 76.64%, 81.82%, and 89.49% for Cage + C2PS + OP model in flexion, extension, lateral bending, and axial rotation when compared with the C2PS + OP model under the same condition. The MVMS of intra-articular cages were 13.80MPa, 40.26MPa, 26.93MPa, and 17.50MPa and those of C2 endplate were 14.56MPa, 34.80MPa, 36.29MPa, and 37.56MPa in Cage + C2PS + OP model under same conditions. Posterior intra-articular cages and cantilever technique to treat BI-AAD can improve the stability of the atlantoaxial joint and reduce the risk of screw-plate breakage. The intra-articular cages can not only complement the height loss on account of atlantooccipital fusion but also provide stable support for posterior fixation fusion.

Address the cause, not the effect: C1-2 joint manipulation and not odontoidectomy in congenital atlantoaxial dislocation and basilar invagination

The C1-2 joints in cases of congenital atlantoaxial dislocation are often oblique in both sagittal and coronal planes giving rise to anteroposterior and vertical slip of C1 over C2. Asymmetry on either side gives rise to coronal/lateral angular tilt along with rotational component. The dislocation is a dynamic process though it may appear to be fixed. The compressing dens is effect of dislocation and not the cause. The treatment should be directed towards C1-2 joint manipulation that would realign the joints as well as the dens. The facetal osteotomies coupled with manipulation for realignment in all planes provides a composite solution for even the complex lateral dislocation or complete spondyloptosis with severely deformed C1–2 joints, obviating the need for transoral decompression.

C2 Nerve Root Preservation During Posterior Fixation for Instability Secondary to Congenital Craniovertebral Junction Anomalies: Feasibility Factors and Related Outcomes

Patients with instability because of congenital craniovertebral anomalies often have complex C1-C2 osseovascular anomalies. C2 nerve root sacrifice has been described to address such difficult anatomy during posterior C1-C2 fixation and has its own downsides. Its preservation as a recent alternative poses greater surgical challenge, and the considerations differ from other causes of craniovertebral junctional instability; the pertaining outcomes have been scarcely studied. The objective of this study was to prospectively determine the feasibility and outcomes related to C2 nerve root preservation in patients with congenital atlantoaxial dislocation (CAAD) after posterior C1-C2 fixation. In this observational study, 63 patients (126 nerve roots) with CAAD after posterior fixation were prospectively assessed. Underlying osseovascular anomalies affecting the feasibility of C2 nerve root preservation, and C2 nerve-related dysfunction at 12 months follow-up were analyzed. The overall C2 nerve root preservation rate was 89.7%. Even in the presence of extreme joint obliquity/spondyloptosis and anomalous vertebral artery, it was feasible in about three fourths. After preservation, 28.3% patients developed new-onset C2 nerve root dysfunction: neuralgia in 2, dysesthesia in 6, and hypoesthesia/paresthesia in 9. The symptoms were not disabling in most patients. In most patients with CAAD, C2 nerve root preservation is feasible despite an aberrant bony and vascular anatomy. A few patients after nerve root preservation develop related symptoms that are conservatively manageable, with no significant adverse consequences. Given the controversy in the literature on C2 nerve sacrifice-related outcomes, we favor an attempt at C2 nerve root preservation.

Anesthetic management for cesarean delivery in a woman with congenital atlantoaxial dislocation and Chiari type I anomaly: a case report and literature review

BackgroundThe preferable choice of anesthesia for the patients with congenital atlantoaxial dislocation (CAAD) and type I Arnold Chiari malformations (ACM-I) has been a very confusing issue in clinical practice. We describe the successful administration of combined spinal-epidural anesthesia for a woman with CAAD and ACM-1 accompanied by syringomyelia.Case presentationOur case report presents the successful management of a challenging obstetric patient with CAAD and ACM-1 accompanied by syringomyelia. She had high risks of difficult airway and aspiration. The injection of bolus drugs through the spinal or epidural needle may worsen the previous neurological complications. The patient was well evaluated with a multidisciplinary technique before surgery and the anesthesia was provided by a skilled anesthesiologist with slow spinal injection.ConclusionsAn interdisciplinary team approach is needed to weigh risks and benefits for patients with CAAD and ACM-1 undergoing cesarean delivery. Therefore, an individual anesthetic plan should be made basing on the available anesthetic equipments and physicians’ clinical experience on anesthetic techniques.

A Safe and Effective Posterior Intra-Articular Distraction Technique to Treat Congenital Atlantoaxial Dislocation Associated With Basilar Invagination: Case Series and Technical Nuances.

The management of atlantoaxial dislocation (AAD) associated with basilar invagination (BI) is challenging, and traditional posterior-only approaches lack the ability to release the anterior soft tissue resulting in unsatisfactory reduction. Furthermore, vertebral artery anomalies and deformed anatomy increase surgical risks. To introduce a safe and efficient technique to reduce congenital AAD and BI through a single-stage posterior-only approach. A total of 65 patients with AAD and concomitant BI who had congenital osseous abnormalities were retrospectively analyzed. All patients had anterior soft tissue released through a posterior-only approach, followed by intra-facet cages implantation, cantilever correction, and instrumentation. Clinical results were measured using the Japanese Orthopedic Association (JOA) scale, and radiographic measurements included the atlanto-dental interval, the distance of odontoid tip above Chamberlain's line, clivus-canal angle (CCA), and syrinx length. Paired t-tests were used to compare preoperative and postoperative measurements. The mean JOA score increased from 10.98 to 14.40 at 1-yr follow-up. Complete reduction of AAD and BI was achieved in 48 patients (73.8%). The mean CCA improved from 115° preoperatively to 129° postoperatively. Reduction of syrinx size was observed in 14 patients at 1 wk and in 35 patients 1 yr after surgery. All patients achieved bony fusion. Posterior intra-articular distraction followed by cage implantation and cantilever correction can achieve complete reduction in most cases of congenitally anomalous AAD associated with BI.

Weak Ligaments and Sloping Joints: A New Hypothesis for Development of Congenital Atlantoaxial Dislocation and Basilar Invagination.

ObjectiveDevelopmental bony craniovertebral junction (CVJ) anomalies seem to have a genetic basis and also abnormal joint morphology causing atlantoaxial dislocation (AAD) and basilar invagination (BI). MethodsDNA extracted polymerase chain reaction single-stranded conformation polymorphism (SSCP) performed for mutation screening of FBN1 gene (n = 50 cases+ 50 age/sex-matched normal; total: 100). Samples with a deviated pattern of bands in SSCP were sequenced to detect the type of variation. Computed tomography (CT) scans of 100 patients (15–45 years old) compared with an equal number of age/sex-matched controls (21.9 ±8.2 years). Joint parameters studied: sagittal joint inclination (SI), craniocervical tilt (CCT), coronal joint inclination (CI). ResultsThirty-nine samples (78%) showed sequence variants. Exon 25, 26, 27, and 28 showed variable patterns of DNA bands in SSCP, which on sequencing gives various types of DNA sequence variations in intronic region of the FBN1 gene in 14%, 14%, 6%, and 44% respectively. CT radiology:SI and CCT correlated with both BI and AAD (p < 0.01). The mean SI value in controls: 83.35° ± 8.65°, and in patients with BI and AAD:129° ± 24.05°. Mean CCT in controls: 60.2° ± 9.2°, and in patients with BI and AAD: 86.0° ± 18.1°. Mean CI in controls:110.3° ± 4.23°, and in cases: 125.15° ± 16.4°. ConclusionThe study showed mutations in FBN1 gene (reported in Marfan syndrome). There is also an alteration of joint morphology, correlating with AAD and BI severity. Hence, we propose a double-hit hypothesis: the presence of weak ligaments (due to FB1 gene alterations) and abnormal joint morphology may contribute to AAD and BI.

Commentary on “Weak Ligaments and Sloping Joints: A New Hypothesis for Development of Congenital Atlantoaxial Dislocation and Basilar Invagination”

Commentary on “Weak Ligaments and Sloping Joints: A New Hypothesis for Development of Congenital Atlantoaxial Dislocation and Basilar Invagination”

Classification of the facets of lateral atlantoaxial joints in patients with congenital atlantoaxial dislocation.

To investigate the morphological characteristics and para-positions of the facets of lateral atlantoaxial joints (FLAJs) in patients with congenital atlantoaxial dislocation (CAAD) and to propose a classification system for the FLAJs. A total of 93 cases of CAAD were included in this retrospective study. The obliquity and slippage of the FLAJs in the sagittal and coronal planes were measured and observed in the CT images of all of the cases. The obliquity and slippage of the FLAJs represented the morphological characteristics and the para-positions, respectively, and were used as classification parameters. Accordingly, a classification system for the FLAJs was established. We additionally investigated the correlation between the classifications of the FLAJs and various types of CAAD. The classifications of the FLAJs in 34 patients with irreducible AAD (IAAD) were also investigated. One hundred eighty-six FLAJs in 93 patients were classified into 6 types (namely, A, B1, B2, C, D1, and D2) for obliquity and 3 types (namely, S0, S1, and S2) for slippage. Among the 186 FLAJs, type B1 and type S0 were the most common obliquity and slippage types, respectively. There were 11 combination types for obliquity and 5 combination types for slippage of bilateral FLAJ in 93 patients. Most of the patients (69.7%, 47/70) with anteroposterior AAD had accompanying slippage and anteversion of the FLAJ in the sagittal plane. Rotational AAD was found in 10 patients with asymmetrical slippage in both FLAJs in the sagittal plane. Lateral translational AAD was found in 6 patients with an S1-type FLAJ in the coronal plane. In 5 patients with lateral angular AAD, FLAJs of types D1 and S2 were observed on one side. Among the 34 patients with IAAD, 31 patients had both obliquity and slippage in the FLAJs on one or both sides. The morphological characteristics and para-positions of the FLAJs on both sides largely determine the types of AAD in patients with CAAD. The types of obliquity and slippage of the FLAJ are related to the reducibility of AAD.

Posterior intra-articular distraction with cage placement to treat congenital atlantoaxial dislocation associated with basilar invagination.

Congenital atlantoaxial dislocation (AAD) associated with basilar invagination (BI) is a complex congenital malalignment at the craniovertebral junction. The olisthesis, atlantoaxial facet joint arthropathy, and the contraction of the anterior soft tissue make the treatment challenging. Our video demonstrates the surgical technique for posterior intra-articular distraction with cage placement to treat congenital atlantoaxial dislocation associated with basilar invagination.The video can be found here: https://youtu.be/7EQqW96HhN8

Can Posterior Reduction Replace Odontoidectomy as Treatment for Patients With Congenital Posterior Atlantoaxial Dislocation and Basilar Invagination?

For patients with odontoid process protrusion and basilar invagination, posterior screw-rod fixation can usually achieve satisfactory horizontal reduction, but in some cases satisfactory reduction in the vertical direction cannot be achieved at the same time. To propose a method for calculation of the theoretical maximum vertical reduction possible in individual patients. The computed tomography imaging data of patients with occipitalization and basilar invagination who were treated at our institute between January 2013 and June 2016 were retrospectively analyzed. The direction of odontoid reduction was decided by the inclination of the lateral joint. The atlanto-dental distance was assumed to be the maximum possible reduction in the horizontal direction. The maximum vertical reduction possible was calculated based on these values. A total of 82 patients (34 males and 48 females) were included. The theoretical vertical reduction value was 4.2±3.0 mm, which was significantly smaller than that of the dental protrusion (14.5±3.8 mm, P=.000). Analysis of follow-up data (29 cases) showed that, the difference between the theoretical vertical reduction value H (4.7±3.5 mm) and the actual vertical reduction value Ha (5.6±3.5 mm) was not significant (P=.139). The theoretical calculation method we proposed can well predict the actual degree of vertical reduction. The theoretical vertical reduction value is significantly lower than the odontoid protrusion value, indicating that satisfactory reduction in the vertical direction is difficult with a posterior approach alone.

Occipito -cervical fusion in Cranio-Vertebral anomalies with basilar invagination

Basilar invagination are uncommon syndrome that occurs when the superior part of the odontoid (part of the C2 vertebrae) migrates upward through foramen magnum and that causes bulbomedullary compression. Basilar invagination are divided on bases of that causation in trau matic and other one is developmental. Mostly seen basilar invagination are developmental. Here with describe a case of 13yr old female with developmental craniovertebral junction abnormality in form of congenital atlanto axial dislocation with Platiebasia with basilar invagination which is treated with decompression and occipital plate and screw based posterior fixation with its clinical as well as radiological outcome. Keywords: Basilar invagination, AtlantoAxial dislocation, Platybasia, OC Fusion, Craniovertebral junction anomaly, Brainstem compression.

Unilateral short-segment screw fixation and bone graft fusion for special upper cervical spine injury

Objective To investigate the clinical effect of posterior unilateral short segment screw fixation and bone graft fusion in the treatment of special upper cervical spine injuries. Methods A retrospective case series study was conducted to analyze the clinical data of 15 patients with upper cervical spine injury admitted to Shanxi Bethune Hospital from July 2012 to May 2017. There were nine males and six females, aged 10-69 years [(41.9±20.9)years]. There were eight patients with traumatic atlantoaxial dislocation, one with congenital atlantoaxial dislocation, two with atlantoaxial dislocation with nonunion of odontoid process, three with Anderson type II odontoid process fracture, and one with old odontoid process fracture. All patients had cervico-occipital pain to different degrees, slender unilateral pedicle and distinct stenosis of vertebral artery. All patients were treated with posterior unilateral screw fixation and bone graft fusion. The injury of spinal cord and vertebral artery, operation time and intraoperative blood loss were recorded. Visual analogue scale (VAS) was used to evaluate pain before and after operation, and Japanese Orthopaedic Association (JOA) score was used to evaluate spinal cord function and postoperative improvement rate before and at the last follow-up. The position of internal fixation and fusion of bone graft were observed by X-ray after operation. Results All 15 patients were followed up for 6-36 months [(20.4±8.6)months]. All the screws were implanted successfully at the first time, without spinal cord or vertebral artery injury. The operation time was 100-210 minutes [(131.3±32.0)minutes], and the intraoperative blood loss was 100-450 ml [(203.1±104.0)ml]. Preoperative VAS score was (7.9±0.9)points, and postoperative VAS score was (3.7±0.8)points (P<0.01). Preoperative JOA score was (12.1±4.4)points, and the JOA score at postoperative follow-up was (16.1±1.4)points, with the improvement rate of 68%. Postoperative X-ray showed good recovery of cervical spine sequence. One patient developed loosened internal fixation after the neck brace protection was removed one month after surgery, and the patient recovered after timely second surgical fixation and fusion. The remaining 14 patients did not have loosened internal fixation, fracture or loss of reduction, with bone fusion 6-12 months after surgery. Conclusion Posterior cervical unilateral short-segment screw fixation and bone graft fusion can restore cervical stability, relieve pain, and improve function recovery, which can be used as a complementary procedure to treat upper cervical spine injury with anatomic structure variation. Key words: Cervical vertebrae; Spinal fusion; Surgical procedures, operative

Commentary: Comprehensive Drilling of C1-2 Facets in Congenital Atlanto-Axial Dislocation and Basilar Invagination: Critical Review.

Commentary: Comprehensive Drilling of C1-2 Facets in Congenital Atlanto-Axial Dislocation and Basilar Invagination: Critical Review.

Comprehensive Drilling of C1-2 Facets and Multiplanar Realignment for Atlanto-Axial Dislocation and Basilar Invagination: 2-Dimensional Operative Video.

The management for congenital atlantoaxial dislocation (AAD) and basilar invagination (BI) has significantly changed in the last 2 decades. Authors operate these cases through a direct posterior approach by opening and manipulating the C1-2 joints (irrespective of C1 assimilation), modifying Goel's technique. The joints in these cases are often oblique in both sagittal and coronal planes giving rise to anteroposterior and vertical slip of C1 on C2. Asymmetry on either side gives rise to coronal/lateral angular tilt along with rotational component. The authors have described comprehensive drilling of the facets (osteotomies) in sagittal and coronal planes to release the joints. Metallic spacers with graft window packed with bone chips are inserted to compensate for the drilled bone. Screws are inserted in C1 lateral mass and C2 pedicle. A rod is fastened between the screw heads and further multiplanar realignment can be achieved by manipulating the rod. The technique obviates the need for transoral decompression and the C1-2 joints are closely fused. The facetal osteotomies coupled with manipulation for realignment in all planes provides a composite solution for even the extremely complex lateral dislocation or complete spondyloptosis with severely deformed C1-2 joints that may be difficult with techniques described earlier. There is no need to include occipital squama and multiple cervical vertebrae in the construct, irrespective of the C1 assimilation. The authors have operated over 200 cases of irreducible CAAD/BI with good outcome and have illustrated their technique in this video. Proper informed consent was obtained from the patient.

Safeguarding the Anomalous Vertebral Artery While Dissecting, Drilling, and Instrumentation of C1-2 Joint for Congenital Atlantoaxial Dislocation: 2-Dimensional Operative Video.

The pathology in congenital atlantoaxial instability is usually in C1-2 joints. Addressing the joints appears to be the most rationale approach. The joints are usually approached posteriorly, manipulated, and fused. Understanding the normal and abnormal anatomy is important. Normally, the third segment of the vertebral artery courses lateral to the C1-2 joint. However, in about 20% of the cases with complex congenital craniovertberal junction anomalies the artery crosses the joint posteriorly. The artery in such cases may be injured while joint manipulation and instrumentation with disastrous consequences. Alternatively, occipital squama can be fused to the cervical spine. However, this requires fusion of multiple segments affecting the neck movements significantly. An anomalous vertebral artery can be dissected, mobilized, and safeguarded while dissecting, manipulating, and fusing the C1-2 joint. In this operative video, authors have highlighted the technique to safeguard the anomalous vertebral artery during joint manipulation. Proper informed consent was obtained from the patient.

Pros and Cons of C2 Nerve Sectioning/Preservation in Posterior Fusion for Congenital Atlantoaxial Dislocation

Deliberate C2 nerve root sectioning and its preservation have been described during posterior fusion for atlantoaxial dislocation (AAD). However, the associated outcomes have been less studied, especially in congenital AAD. Our objective was to study the clinical outcomes after C2 nerve root sectioning and the feasibility of C2 preservation in these patients. The data from 190 patients were retrospectively studied. The decision to cut or preserve the C2 nerve root was determined by the preoperative radiologic findings and intraoperative suitability of its preservation. During follow-up, the patients were questioned about C2 nerve-related dysfunction. The pros and cons of sectioning or preservation of the C2 nerve root and the related feasibility factors are also described. Complex C1-C2 anatomy that required extensive dissection and drilling was seen in 139 patients. After C2 nerve root sectioning in 178 patients, none reported bothersome hypoesthesia, paresthesia, or dysesthesia that required medication. However, 9 patients (5.1%) developed nonhealing occipital ulcers and most required flap coverage or a skin graft. C2 nerve root preservation is feasible with an adequate inferior C1 lateral mass and normal-size ganglion. In patients with C1-occipital condyle hypoplasia, extremely oblique joints, spondyloptosis, incurved occiput, pseudofacets, and anomalous vertebral artery, preservation of the C2 nerve root is difficult. The advantages of sectioning the C2 nerve root are many. However, a subset of patients is prone to morbid occipital neuropathic ulcers. After C2 nerve sectioning, one should be cautious of such complications. C2 nerve root preservation should be strongly considered for patients with favorable anatomy.