Complex Chiari malformation: using craniovertebral junction metrics to guide treatment.

The complex Chiari, characterized by abnormal craniocervical bony anatomy in addition to Chiari tonsillar herniation, is a relatively recent addition to the concepts surrounding the Chiari literature. The primary findings of complex Chiari include craniocervical kyphosis and retroflexed odontoid, both of which can be described with radiographic measurements. This manuscript will outline the background literature regarding Chiari craniocervical morphometrics and supply an algorithm for the general management of complex Chiari patients.

Retro-odontoid Degenerative Pseudotumour Causing Spinal Cord Compression and Myelopathy: Current Evidence on the Role of Posterior C1-C2 Fixation in Treatment.

BACKGROUND: A retro-odontoid pseudotumour compressing the spinal cord and causing myelopathy is often associated with an inflammatory condition such as rheumatoid arthritis. A degenerative non-inflammatory retro-odontoid pseudotumour responsible for clinically relevant spinal cord compression is a rare condition described in small clinical series and is likely associated with craniovertebral junction hypermobility or instability-like conditions. For several years, direct removal of the lesion through an anterior or lateral approach has been advocated as the best surgical option. However, in the last decade the posterior approach to the craniovertebral junction, to perform C1-C2 fixation and C1 laminectomy without removal of the retro-odontoid tissue, has demonstrated its efficacy in reducing retro-odontoid pannus as well as in obtaining improvement of myelopathy. METHODS: In this paper we analyse the clinical and radiological outcomes of seven patients (five males and two females) treated with posterior C1-C2 fixation and C1 laminectomy for a degenerative non-inflammatory retro-odontoid pseudotumour responsible for spinal cord compression. C1 laminectomy provided immediate spinal cord decompression. We also review the relevant literature focusing on associated cervical degenerative conditions that may contribute to triggering or acceleration of atlantoaxial hypermobility or 'instability', causing formation of the retro-odontoid tissue. RESULTS: The mean follow-up period (of six followed-up patients) was 55.8 months (range 10-96 months). In all cases the Nurick score at the latest follow-up visit demonstrated clinical improvement; magnetic resonance imaging during follow-up demonstrated progressive reduction of the retro-odontoid pseudotumour in all but one patient, who died of surgery-unrelated disease in the early postoperative period. No vascular or neural damage secondary to C1-C2 fixation was observed. CONCLUSION: C1-C2 fixation associated with C1 laminectomy is an effective surgical option to treat myelopathy secondary to a degenerative retro-odontoid pseudotumour. In these cases, direct removal of intracanalar tissue compressing the spinal cord is not required, as C1-C2 fixation is sufficient to cause its disappearance.

Stability-Sparing Endoscopic Endonasal Odontoidectomy in a Malformative Craniovertebral Junction: Case Report and Biomechanical Considerations.

BACKGROUND: The craniovertebral junction (CVJ) is often involved in a wide range of congenital, developmental and acquired pathologies that can create bony and ligamentous instability or cause direct compression on the medulla and cervical spine cord, resulting in significant impairment. Atlas assimilation is the most common malformation in the CVJ and can be frequently associated with basilar invagination (BI) and Chiari malformation (CM) type I. Posterior atlas assimilation more frequently leads to BI type II with a mass effect on neural structures but usually no signs of biomechanical instability. Operative approaches to the CVJ have undergone a remarkable evolution and can be divided into ventral, lateral and dorsal ones. In this kind of surgery, it is vital to detect and eventually treat any CVJ instability. CASE DESCRIPTION: We present a case of CVJ malformation comprising assimilation of the posterior arch of the atlas, BI type II and CM, treated by endoscopic endonasal odontoidectomy and partial clivus removal to spare CVJ stability. CONCLUSION: Neurological and biomechanical analysis of all CVJ malformations permits stratification and selection of those cases that can be managed by simple, direct, minimally invasive decompression with no need for surgical fusion.

[Endoscopic endonasal removal of the invaginated odontoid process of the C2 vertebra].

UNLABELLED: Pathological processes in the craniovertebral region (clivus, C1 anterior arch, odontoid process and body of the C2 vertebra, i.e. C0-C1-C2 segments) are very difficult to diagnose and treat. The craniovertebral junction instability may develop in the case of a significant lesion of C1-C2 segments. Among diseases causing destruction of the clivus structures and C1-C2 vertebrae and compression of the spinal cord, the following ones are most common: chordoma, giant cell tumor, osteoblastoma, rheumatoid lesion, metastases, platybasia, and basilar impression. These diseases can cause the initial instability of the craniovertebral junction and be accompanied by gross neurological disorders, which complicates the diagnosis and surgical treatment of these patients. MATERIAL AND METHODS: We operated on two patients diagnosed with invagination of the odontoid process of the C2 vertebra. In both cases, one-stage operation was performed that included occipitospondylodesis and endoscopic endonasal removal of the C2 odontoid process. RESULTS: In the postoperative period, partial regression of the neurological symptoms was observed that included an increase in the strength and range of motions in the arms and distal legs, regressed spasticity in the arms and significantly reduced spasticity in the legs, and a significant improvement in all kinds of sensitivity in the arms, legs, and torso. Postoperative liquorrhea was observed in 1 case (patient 2); re-operation to close a CSF fistula was conducted. Later, no signs of liquorrhea were noted. In both cases, control MRI and spiral CT revealed a postoperative bone defect of the C2 odontoid process and clivus, complete decompression of the medulla oblongata and upper cervical spine segments, and no evidence of spinal canal stenosis; the stabilizing system was competent and properly placed. CONCLUSION: The endoscopic endonasal approach, compared to the standard transoral approach, has significant advantages in that the soft palate remains intact, the oropharynx area is less damaged, and the hospitalization and rehabilitation duration is reduced. Also, there are no problems and complications such as possible failure of sutures in the oral cavity and a large wound surface in the oropharynx area. The patient can eat on his own immediately after the operation without the use of a stomach tube (it does not cause any inflammatory complications of the oral cavity). However, the surgical technique of the endoscopic endonasal approach to the C1-C2 segment is more complex than that of transoral surgery and requires the surgeon to be skilled and experienced.

Transoral approach to extradural non-neoplastic lesions of the craniovertebral junction.

BACKGROUND: The transoral approach allows for an unobstructed anterior view of the craniovertebral junction from the lower clivus to C1 and C2. It can be applied to a heterogeneous spectrum of pathological lesions involving this area including craniovertebral junction malformations, atlanto-axial synovial cysts, pseudoarthrosis following odontoid fractures, selected cases of retro-odontoid pannus, and vertical translocation in rheumatoid patients. METHODS: Microsurgical strategy is dictated by the nature and site of the target lesion. Atlas preservation during transoral approach (atlas-sparing technique) minimizes postoperative instability and is suitable for the majority of extradural non-neoplastic lesions of the craniovertebral junction. The transoral trans-atlas approach allows for a wider exposure of the anterior craniovertebral junction, but at the price of a higher incidence of postoperative instability; it is usually required in patients with severe basilar invagination or irreducible vertical translocation in rheumatoid arthritis. CONCLUSIONS: The transoral corridor is an effective route to approach a variety of anterior extradural lesions of the craniovertebral junction. Tailoring the approach to each specific lesion provides the needed exposure whilst limiting postoperative instability.

The selective odontoidectomy: endoscopic endonasal approach to the craniocervical junction.

OBJECTIVE: The resection of the odontoid process via an extended endoscopic endonasal approach has been recently proposed as an alternative to the microscopic transoral method. We aimed to delineate a minimally invasive endoscopic transnasal odontoidectomy and to describe the endoscopic anatomy of the anterior craniovertebral junction (CVJ). MATERIALS AND METHODS: The anterior CVJ of 14 fresh adult cadavers were selectively accessed via a binostril endoscopic endonasal approach using 0- and 30-degree endoscopes. RESULTS: The nasopharynx was widely exposed without removing any of the turbinates and without performing a sphenoidotomy. Occipital condyles and lateral masses of the C1 vertebra have been exposed inferiorly at lateral margins of the exposure, in addition to the foramen lacerum, which came into view at the superolateral corner of the operative field. The anterior arch of C1 and the upper 1.5 cm of the odontoid process of C2 have been removed via a minimally invasive endoscopic transnasal approach in all dissections. CONCLUSIONS: We propose the selective odontoidectomy as a minimally invasive method for the endoscopic endonasal removal of the odontoid process. By using this approach, turbinates and the sphenoid sinus remain unharmed. In addition, this approach may be used in exposing pathologies situated laterally at the anterior CVJ, such as the lateral masses of atlas and occipital condyles.

[Retro-odontoid pseudotumor in diffuse idiopathic skeletal hyperostosis]. / Pseudotumor retroodontoideo en un paciente con hiperostosis esquelética idiopática difusa.

Retro-odontoid pseudotumors are lesions caused by inflammatory granulation or reactive soft tissue hypertrophy from chronic atlantoaxial subluxation. However, one-third of the cases reported in the medical literature did not show atlantoaxial instability clearly. The authors present the case of a 76-year-old man previously diagnosed with diffuse idiopathic skeletal hyperostosis who presented with severe progressive myelopathy. A magnetic resonance imaging of his cervical spine revealed a retro-odontoid predural mass, which caused a severe compression of the cervical spinal cord. The patient underwent a posterior laminectomy of the atlas and an occipitocervical fusion. After surgery, the pseudotumor was considerably smaller and the neurological symptoms improved.

Management of upper cervical spine injuries: a review.

Upper cervical spine injuries are commonly associated with trauma and require significant forces to produce. When these injuries occur they can have devastating functional consequences. The distinctive anatomy of the upper cervical spine leads injuries to occur in predictable patterns. Injuries can occur to the unique osseus structures or ligamentous connections. Common injuries include occipital condylar fractures, atlanto-occipital dislocation, fractures of the ring of C1, ligamentous injuries involving the ring of C1, and the three types of fractures of C2, pars fractures, odontoid fractures and C2 body fractures. We present these common injuries found in the occipital-atlantoaxial complex and their management based on the current and historical literature.

Unilateral atlantal lateral mass hypertrophy associated with atlanto-occipital fusion.

PURPOSE: Unilateral hypertrophy of the lateral mass of the atlas is an extremely rare condition. The authors present a rare type of unilateral atlantal mass hypertrophy with atlanto-occipital fusion which is associated with an invaginated lateral mass of the atlas and the odontoid process into the foramen magnum. METHODS: A 45-year-old woman presented with a 2-year history of progressive bilateral weakness in the upper and lower extremities and gait disturbance. The left lateral mass of the atlas was hypertrophied and had invaginated into the foramen magnum with the odontoid. The spinal cord was severely compressed at the level of the foramen magnum, surrounded by the lateral mass of the atlas, the odontoid process and the occipital bone. RESULTS: First, ventral decompression was performed using a transmandibular approach. The anterior arch of the atlas, the medial side of the hypertrophied lateral mass and the odontoid process were resected. Two weeks after primary surgery, posterior occipitocervical fusion was performed. The postoperative course of the patient was uneventful. Three years after the operation, she could walk without assistance and her paresthesia improved. CONCLUSIONS: To our knowledge, such a case of unilateral atlantal mass hypertrophy associated with atlanto-occipital fusion has not been described previously. The authors discuss the pathology of this case and review the literature on unilateral atlantal mass hypertrophy and associated anomalies of the upper cervical spine.

C1 laminectomy for retro-odontoid pseudotumor without atlantoaxial subluxation: review of seven consecutive cases.

PURPOSE: A retro-odontoid pseudotumor is usually a reactive fibrocartilaginous mass associated with atlantoaxial subluxation (AAS). However, a retro-odontoid pseudotumor not associated with AAS, which undergoes spontaneous regression following C1 laminoplasty, has been reported. The purpose of this study was to report surgical outcomes of C1 laminectomy for retro-odontoid pseudotumor without AAS. MATERIALS AND METHODS: The cases of seven patients (mean age 75.6 ± 7.6 years-old) with retro-odontoid pseudotumor without AAS were reviewed. The mean follow up time was 52.3 ± 25.5 months. Each patient underwent a C1 laminectomy with an additional C3-6 expansion laminoplasty in three patients. The Japanese Orthopaedic Association score (JOA score) was used for neurological assessment. Pseudotumor size and additional AAS were analyzed using MRI and radiography. RESULTS: All patients exhibited neurological improvement following surgery, the JOA score improved from 7.2 ± 3.2 to 14.1 ± 2.6. The mean O-C2 and C2-7 angle decreased from -3.2 ± 2.1° to -3.9 ± 1.7°, showing a slight kyphotic change. Postoperative AAS was not observed. All pseudotumors spontaneously resolved, and recurrence and regrowth were not observed. Five patients had MRIs after gadolinium administration; four patients who showed enhancement of the pseudotumor had almost complete reduction within 1 year following surgery. DISCUSSION: Our study, assessing the outcome of C1 laminectomy for retro-odontoid pseudotumor, found neurological improvement in all cases. Since all pseudotumors were reduced and additional AAS was not observed, C1 laminectomy for retro-odontoid pseudotumor, in the absence of AAS, is recommended as a therapeutic strategy.

Development of dysphagia and trismus developed after c1-2 posterior fusion in extended position.

Cervical misalignment after upper cervical fusion including the occipital bone may cause trismus or dysphagia, because the occipito-atlanto joint is associated with most of the flex and extended motion of the cervical spine. There are no reports of dysphagia and trismus after C1-2 fusion. The purpose of this paper is to demonstrate the potential risk of dysphagia and trismus even after upper cervical short fusion without the occipital bone. The patient was a 69-year-old man with myelopathy caused by os odontoideum and Klippel-Feil syndrome, who developed dysphagia and trismus immediately after C1-2 fusion and C3-6 laminoplasty. Radiographs and CT revealed that his neck posture was extended, but his symptoms still existed a week after surgery. The fixation angle was hyperextended 12 days after the first surgery. His symptoms disappeared immediately after revision surgery. The fixation in the neck-flexed position is thought to be the main cause of the patient's post-operative dysphagia and trismus. Dysphagia and trismus may occur even after short upper cervical fusion without the occipital bone or cervical fusion in the neck-extended position. The pre-operative cervical alignment and range of motion of each segment should be thoroughly evaluated.

Individualized treatment of craniovertebral junction malformation guided by intraoperative computed tomography.

STUDY DESIGN: This study was designed to report our preliminary experience of intraoperative computed tomography (iCT) using a mobile scanner with integrated neuronavigation system (NNS). OBJECTIVE: The objective of this study was to assess the feasibility and potential utility of iCT with integrated NNS in individualized treatment of craniovertebral junction malformation (CVJM). SUMMARY OF BACKGROUND DATA: The surgical management of congenital craniovertebral anomalies is complex due to the relative difficulty in accessing the region, critical relationships of neurovascular structures, and the intricate biomechanical issues involved. METHODS: We reported our first 19 complex CVJM cases including 11 male and 8 female patients from January, 2009 to June, 2009 (mean age, 33.9 y; age range, 13 to 58 y). A sliding gantry 40-slice CT scanner was installed in a preexisting operating room. Image data was transferred directly from the scanner into the NNS using an automated registration system. We applied this technology to transoral odontoidectomy in 17 patients. Moreover, with the extra help of iCT integrated with NNS, odontoidectomy through posterior midline approach, and transoral atlantal lateral mass resection were, for the first time, performed for treatment of complex CVJM. RESULTS: NNS was found to correlate well with the intraoperative findings, and the recalibration was uneven in all cases with an accuracy of 1.6 mm (1.6: 1.2 to 2.0). All patients were clinically evaluated by Nurick grade criteria, and neurological deficits were monitored after 3 months of surgery. Fifteen patients (79%) were improved by at least 1 Nurick grade, whereas the grade did not change in 4 patients (21%). CONCLUSIONS: iCT scanning with integrated NNS was both feasible and beneficial for the surgical management of complex CVJM. In this unusual patient population, the technique seemed to be valuable in negotiating complex anatomy and achieving a safe and predictable decompression.

Video-assisted microsurgical transoral approach to the craniovertebral junction: personal experience in childhood.

PURPOSE: This paper outlines the perspectives of transoral craniosurgery for anterior craniovertebral junction (CVJ) compressive abnormalities in the specific subset of paediatric patients. In particular we analyzed the opportunity for endoscopic video-assisted approach to the CVJ along with neuronavigation for anterior decompression by the transoral approach in paediatric patients. METHODS: Among 30 patients ranging 6-78 years undergoing CVJ decompressive procedures, we operated transorally 3 paediatric patients (ranging 11-15 years) by using open access, microsurgical technique, neuronavigation, and endoscopy. RESULTS: The microscope was the main stone of the transoral procedure; a complete CVJ decompression was accomplished in all the cases by using the 30-degree endoscope that allowed to identify residual compression not clearly visible by using the microscope alone. The use of an angled-lens endoscope can significantly improve the exposure of the clivus without splitting the soft palate. CONCLUSIONS: Endoscopically assisted transoral surgery represents an emerging alternative to the standard microsurgical approach to the anterior CVJ. Used in conjunction with traditional microsurgery and intraoperative fluoroscopy, endoscopy provides information for a better decompression with a reduced need for extensive soft-palate splitting, no need for hard-palate resection, or extended maxillotomy. Transoral video-assisted microsurgical approach should be considered the gold standard especially in the paediatric patient.

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

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

Bilateral C1 laminar hooks combined with C2 pedicle screws fixation for treatment of C1-C2 instability not suitable for placement of transarticular screws.

The study design described here is a posterior C1-C2 fusion technique composed of bilateral C1 hooks and C2 pedicle screws. In addition, the clinical results of using this method on 13 patients with C1-C2 instability are reported. The objectives are to introduce a new technique for posterior C1-C2 fusion and to evaluate the clinical outcome of using it to treat C1-C2 instability. From October 2006 to August 2008, 13 patients (9 men and 4 women) with C1-C2 instability were included in this study: 3 had acute odontoid fractures, 4 had obsolete odontoid fractures, 4 had os odontoideum and 2 had traumatic rupture of the transverse ligament. All patients underwent posterior atlantoaxial fixation with bilateral C1 hooks and C2 pedicle screws. The mean follow-up duration was 25 months (range 13-30 months). Each patient underwent a complete cervical radiograph series, including anterior-posterior, lateral, and flexion-extension views, and a computed tomographic scan. The clinical course was evaluated according to the Frankel grading system. No clinically manifested injury of the nerve structures or the vertebral artery was observed in any of these cases. Five patients with neurological symptoms showed significant improvement in neurological function postoperatively. Bony fusion and construction stability were observed in all 13 patients (100%) on their follow-up radiographs, and no instrument failure was observed. Bilateral C1 hooks combined with C2 pedicle screws can be used as an alternative treatment method for C1-C2 dislocation, especially in cases not suitable for the use of transarticular screws. The clinical follow-up shows that this technique is a safe and effective method of treatment.

Unusual bone formation in the anterior rim of foramen magnum: cause, effect and treatment.

A rare case of proatlas segmental abnormality resulting in a bony mass in the anterior rim of the foramen magnum is studied. Case report of a 19-year-old female showed a progressive weakness of all four limbs for about 3 years. When admitted she could not perform any useful activities by herself. Investigations revealed an unusual bone growth in the region of the anterior rim of foramen magnum that resulted in severe cord compression. The abnormal bone formation involved the lower end of clivus, the tip of the odontoid process and the posterior arch of the atlas. Dynamic imaging did not reveal any clear evidence of instability. Following transoral decompression and posterior fixation, the patient showed dramatic and lasting clinical recovery. Conclusions were drawn as follows. Anomalies of the most caudal part of the occipital sclerotomes due to the failure of proatlas segmentation can be the cause of an abnormal bone mass in the anterior rim of foramen magnum. Transoral decompression, followed by posterior atlantoaxial fixation, results in neurological recovery and provides lasting cure from the problem.

Microendoscopic anterior approach for irreducible atlantoaxial dislocation: surgical techniques and preliminary results.

STUDY DESIGN: Surgical techniques and preliminary results. OBJECTIVE: To describe and evaluate the safety and efficacy of a new minimal invasive technique for the irreducible atlantoaxial dislocation (IADD). SUMMARY OF BACKGROUND DATA: Endoscope has been widely used in minimal invasive spinal surgery. However, there are no clinical reports regarding anterior approach for IADD in the literature. METHODS: Ten consecutive patients with IADD were treated by anterior release with microendoscopic aide and subsequently reduction, anterior transarticular screw fixation and morselized autologous bone grafts. There were 3 cases of odontoid dysplasia, 4, chronic odontoid fracture, 1, odontoid absence, 1 fasilar impression, and 1 malunion of odontoid fracture. According to Symon and Lavender's classification of disability, 6 cases were moderate disability, 3 severe nonbedbound, and 1 severe bedridden. The procedure was performed by the same surgeon (Yong-Long Chi). RESULTS: The new technique was performed successfully in all cases. All the patients underwent transarticular screw fixation and anterior morselized autograft fusion. The average operation time was 120 min (range, 90 to 150 min) and the mean estimated blood loss was 150 mL (range, 100 to 250 mL). Postoperative radiographs demonstrated that 9 cases restored anatomic position and 1 had partial reduction. According to the postoperative computed tomography all the screws were appropriately placed. Follow-up after surgery, longest is 16 months and minimal 8 months with a mean of 12 months, neurologic status was improved in all patients. There was no loss of fixation and solid fusion was achieved in all cases. CONCLUSIONS: Surgical technique of microendoscopic anterior release, reduction, fixation, and fusion is safe and reliable minimally invasive for treating IADD.

[Injuries to the upper cervical spine. Part 2: osseous injuries]. / Verletzungen der oberen halswirbelsäule. Teil 2: knöcherne verletzungen.

This article for continuing education describes osseous injuries of the upper cervical spine and their treatment. Fractures of the occipital condyles are very rare and mostly result from high-speed traumas. These are usually managed conservatively. Atlas fractures can also usually be treated with immobilization of the cervical spine; in cases of unstable or dislocated injuries, various surgical procedures are employed. Three types of axis fractures can be distinguished: odontoid fractures, traumatic spondylolistheses, which also affect the isthmic region, and atypical fractures in the corpus region. The incidence, classification, diagnostic workup, standard treatment, and characteristics of the fractures mentioned are presented in detail.

Posterior Arch Screw for Type II Odontoid Fracture: An Alternative Procedure.

BACKGROUND/OBJECTIVE: Atlantoaxial fusion procedures may be difficult in situations such as high-riding vertebral artery, a narrow C2 pedicle, and the presence of ponticulus posticus-arcuate foramen. With respect to vertebral artery (VA) anomalies, persistent first intersegmental artery, extracranial origin of the posterior inferior cerebellar artery at the C1-C2 level, and fenestration of the VA are all major risk factors for VA injury in C1-C2 fusion surgeries. METHODS: To safeguard the VA, we designed the unilateral fusion procedure (all screws lie in the ipsilateral side, either the right side or left side): a unilateral transarticular screw combined with an ipsilateral-side C1 posterior arch screw and a C2 laminar screw (LS), with both C1-C2 screws inserted from opposite side, although the trajectory will be on the same side. In addition to atlantoaxial stabilization with screws and rod, autograft bony fusion was performed on the same side as modified Brook's procedure and augmented with sublaminar tapping. RESULTS: We present a series of 3 cases operated for odontoid fracture with associated high risk for fusion on one side alone. The fact that the chance of VA injury is high in transarticular screw, in lateral mass screw, less in pars screw, and pedicle screw is well known. Alternate screw placement to avoid VA injury would be a posterior arch screw for C1 and laminar screw for C2, which was adopted in our technique. CONCLUSIONS: We combined a unilateral transarticular screw and modified Brook's procedure with sublaminar tapping for additional augmentation of fusion. We would like to highlight this C1 posterior arch screw as an alternative procedure for atlantoaxial fusion.

Traumatic rotary posterior dislocation of the atlas on the axis without fracture. Report of a case and review of literature.

BACKGROUND: Traumatic rotary posterior dislocation of C1 on C2 without fracture (TRPDAAWF) is a very rare complication in severe accidents, and its pathophysiology is still under debate. CASE DESCRIPTION: Although 6 similar cases have been reported previously, we report the lessons learned during handling of the patient. A young man who is a victim of severe car crash injury, with neglected displacement of the intact odontoid process to the front of the anterior arch of C1, is reported. Some problematic and life-threatening events in the management of the case are presented. CONCLUSIONS: We report a new and rare case of TRPDAAWF. It is hypothesized that a similar situation could only be possible if rotary subluxation of C1 on C2 follows a severe hyperextension injury; otherwise, traumatic fracture of the odontoid process might have been inevitable.