Implantation of C2 prosthesis with dorsal fusion C0-C4 due to pathologic C2 fracture. Case report and literature review.

INTRODUCTION: Pathological destruction of the axis vertebra leads to a highly unstable condition in an upper cervical spine. As surgical resection and anatomical reconstruction of the second cervical vertebrae represents a life threatening procedure, less radical approaches are preferred and only few cases of C2 prosthesis are described in literature. CASE DESCRIPTION: The focus of this case report is a 21-year-old man with a pathological fracture of C2 managed primarily surgically with the C1-C3 dorsal fusion. Due to the progression of giant cell tumor and destruction of the axis vertebra, C2 prosthesis through anterior approach and dorsal occipito-cervical fusion C0-C4 were performed. Postoperative infection was managed surgically with a 2-staged dorsal debridement, ostheosynthesis material change and autologous bone graft. After a 4 week-intravenous therapy with the ceftriaxone in combination with the amoxicillin/clavulanate, followed by 12 week per oral therapy with amoxicillin/clavulanate in combination with ciprofloxacin, the complete recovery of the infection was achieved. Radiotherapy was initiated 2 months after the last revision surgery and the patient showed a good clinical outcome with stable construct at a 1 year follow-up. A review of literature of all reported C2 prosthesis cases was performed CONCLUSION: C2 prosthesis allows a more radical resection in pathological processes involving the axis vertebra. Combined with the posterior fusion, immediate stability is achieved. Anterior surgical approach is through a highly unsterile oral environment which presents a high-risk of postoperative infection.

Anatomy of the craniocervical junction - A review.

An in-depth understanding of the anatomy of the craniocervical junction (CCJ) is indispensable in skull base neurosurgery. In this paper, we discuss the osteology of the occipital bone, the atlas (C1) and axis (C2), the ligaments and the muscle anatomy of the CCJ region and their relationships with the vertebral artery. We will also discuss the trajectory of the vertebral artery and review the anatomy of the jugular foramen and lower cranial nerves (IX to XII). The most important surgical approaches to the CCJ, including the far lateral approach, the anterolateral approach of Bernard George and the endoscopic endonasal approach, will be discussed to review the surgical anatomy.

Two-Surgeon Multidisciplinary Approach to Pediatric Cervical Spinal Fusion: A Single-Institution Series and Review of the Literature.

BACKGROUND: A collaborative 2-surgeon approach is becoming increasingly popular in surgery but is not widely used for pediatric cervical spine fusions. The goal of this study is to present a large single-institution experience with pediatric cervical spinal fusion using a multidisciplinary 2-surgeon team, including a neurosurgeon and an orthopedic surgeon. This team-based approach has not been previously reported in the pediatric cervical spine literature. METHODS: A single-institution review of pediatric cervical spine instrumentation and fusion performed by a surgical team composed of neurosurgery and orthopedics during 2002-2020 was performed. Demographics, presenting symptoms and indications, surgical characteristics, and outcomes were recorded. Particular focus was given to describe the primary surgical responsibility of the orthopedic surgeon and the neurosurgeon. RESULTS: A total of 112 patients (54% male) with an average age of 12.1 (range 2-26) years met the inclusion criteria. The most common indications for surgery were os odontoideum with instability (n=21) and trauma (n=18). Syndromes were present in 44 (39%) cases. Fifty-five (49%) patients presented with preoperative neurological deficits (26 motor, 12 sensory, and 17 combined deficits). At the time of the last clinical follow-up, 44 (80%) of these patients had stabilization or resolution of their neurological deficit. There was 1 new postoperative neural deficit (1%). The average time between surgery and successful radiologic arthrodesis was 13.2±10.6 mo. A total of 15 (13%) patients experienced complications within 90 days of surgery (2 intraoperative, 6 during admission, and 7 after discharge). CONCLUSIONS: A multidisciplinary 2-surgeon approach to pediatric cervical spine instrumentation and fusion provides a safe treatment option for complex pediatric cervical cases. It is hoped that this study could provide a model for other pediatric spine groups interested in implementing a multi-specialty 2-surgeon team to perform complex pediatric cervical spine fusions. LEVEL OF EVIDENCE: Level IV-case series.

Analysis of surgical strategies and efficacy in the treatment of Os odontoideum with atlantoaxial dislocation.

BACKGROUND: There are many classification systems for atlantoaxial dislocation (AAD). Among these systems, the definitions of irreducible AAD remain vague, and its treatments are not unified. OBJECTIVE: To explore the surgical strategies and efficacy for the treatment of os odontoideum (OO) with AAD. METHODS: The clinical data of 56 OO patients with AAD who underwent surgery from January 2017 to June 2021 were retrospectively analyzed. AAD was classified into four types, Type I and type II were treated with posterior fixation and fusion. Type III received posterior fixation and fusion after irreducible dislocations were converted to reducible dislocations by translateral mass release or transoral release. Type IV required transoral release for conversion into reducible dislocations before posterior fixation and fusion. The operation time, blood loss, and complications were recorded. The preoperative and postoperative neurological function changes were assessed using the Japanese Orthopedic Association (JOA) score. Postoperative fusion status was assessed by X-ray. RESULTS: There were 40 cases of type I-II, 14 cases of type III, and two cases of type IV AAD. The operation times of single posterior fixation and fusion, combined translateral mass release and combined transoral release were 130.52 ± 37.12 min, 151.11 ± 16.91 min and 188.57 ± 44.13 min, the blood loss were 162.63 ± 58.27 mL, 235.56 ± 59.94 mL, 414.29 ± 33.91 mL, respectively. One patient with type III died, one with type III underwent revision surgery due to infection, and three patients with type I had further neurological deterioration after operation. fifty-five patients were followed up for 12-24 months. The follow-up results showed that enough decompression was achieved and that fixation and fusion were effective. The JOA score increased from 9.58 ± 1.84 points preoperative to 13.09 ± 2.68 points at 3 months after operation, 14.07 ± 2.83 points at 6 months and 14.25 ± 2.34 at 12 months after operation, all significant differences compared with preoperative results (P < 0.05). CONCLUSION: OO patients with irreducible AAD can be treated by translateral mass release or transoral release combined with posterior fixation and fusion, while some of those with bony fusion can be treated by transoral release combined with posterior fixation and fusion.

Surgical Management Of Irreducible Atlanto-Axial Dislocation With OS Odontoideum And Klippel-Feil Syndrome.

Klippel-Feil syndrome (KFS) is the congenital fusion of two or more cervical vertebrae which is often associated with various other abnormalities in the cervical spine. Involvement the upper cervical segments leads to atlanto-axial instability which manifests as progressive neurological symptoms due to compression on the spinal cord. These cases pose a surgical challenge due the abnormal and unique anatomy of each patient. A 37-year-old patient presented with neck pain and cervical myelopathy due to a posterior subluxation of C2-3 fused segment over C4-6 fused segment. The patient had an os odontoideum, incomplete posterior arch of C1, anomalous course of vertebral artery and C3 hemi-vertebra. The patient was successfully managed with transoral odontoidectomy and occipeto-cervical fusion. Irreducible atlanto-axial dislocation in a patient with an abnormal upper cervical spine anatomy may require transoral decompression followed by posterior fusion.

Asymmetry of the C2 pars interarticularis: a clinical anatomical study with relevance to screw placement.

PURPOSE: Potential asymmetries of the C2 posterior elements pose a problem for the spine surgeon seeking to make the best choice for spinal stabilization while reducing morbidity. METHODS: A digital caliper was used to measure the pars interarticularis height and length on left and right sides of 25 adult C2 vertebrae. The pars interarticularis was defined as the bone between the posterior most aspect of the superior articular process and the anterior most aspect of the inferior articular process of C2. Also, the C2 vertebrae from 49 patients were scanned by CT. Parasagittal images were reviewed and using the same definitions as were used for the skeletal specimens, the length and the height of the C2 pars interarticularis from both the left and right sides were measured using CT. The image slices were acquired at 3 mm intervals. The pars interarticularis height was determined on sagittal CT reconstruction, while the pars interarticularis length was calculated on the basis of the axial images. RESULTS: The lengths and the heights of the left and right pars interarticularis were compared using CTs of patients and skeletal specimens. No significant differences were found in the length and height measurements of the CT images on both sides. However, in the skeletal specimens, the left and right pars interarticularis did not differ significantly in length but differed significantly in height (p = 0.003). The mean height of the left pars interarticularis was approximately two times larger than the right in the skeletal specimens. Absolute differences were calculated between the side with the greater length and height and the side with the lesser length and height irrespective of their left-right orientations. For CT measurements, most differences in length and height between the greater pars interarticularis and lesser pars interarticularis occurred between 0 and 1 mm with each successive disparity interval yielding lower numbers. Skeletal measurements revealed a similar length disparity distribution to the CT measurements. However, height measurements in the skeletal specimens varied widely. Eight pars interarticularis specimens demonstrated a height difference between 0 and 1 mm. No dry bone pars interarticularis specimens demonstrated a height difference between 1 and 2 mm. The pars interarticularis of nine specimens demonstrated a height difference between 2 and 3 mm. Two demonstrated a height difference between 3 and 4 mm. Four demonstrated a height difference between 4 and 5 mm and two demonstrated a height difference greater than 5 mm. The greater pars interarticularis lengths and heights were combined and compared to their lesser counterparts on CT and skeletal measurements. In all measurements of this type, significant differences were found in the pars interarticularis length and height, whether measured through CT or via digital calipers. CONCLUSION: Asymmetry between the left and right C2 pars interarticularis as shown in the present study can alter surgical planning. Therefore, knowledge of this anatomical finding might be useful to spine surgeons.

Surgical Outcomes for C2 Tear Drop Fractures: Clinical Relevance to Hangman's Fracture and C2-3 Discoligamentous Injury.

OBJECTIVE: To analyze characteristics of surgically managed tear drop (TD) fractures of the C2 axis associated with other injuries such as hangman's fracture and C2-3 discoligamentous injury as well as treatment outcomes. METHODS: A total of 14 patients (eight men and six women) with TD fractures of the C2 , who were surgically treated at four national trauma centers of tertiary university hospitals from January 2000 to December 2017, were included in this retrospective study. The mean age of the patients was 45.5 years (ranging from 19 to 74 years). The characteristics, surgical treatment methods (anterior fusion vs posterior fusion), and results of 14 TD fractures of the C2 were analyzed retrospectively. And the clinical relevance between C2 TD fracture and hangman's fracture and C2-3 discoligamentous injury was investigated through the co-occurrence between injuries. The mean follow-up time after surgery was 22.6 months (ranging from 12 to 60 months). RESULTS: Among 14 patients with TD fracture of the C2 , four patients (28.6%) had anterior TD fracture and 10 patients (71.4%) had posterior TD fracture. All 10 posterior TD fracture patients had anterior C2-3 displacement. While two of four anterior TD fracture patients had posterior C2-3 displacement, the remaining two did not. All 14 patients of TD fracture had at least two or more other associated C2 injuries as well as C2-3 discoligamentous injuries. About 92.9% (13/14) of the patients had typical or atypical hangman's fracture; 100% (10/10) of the posterior TD fracture patients had hangman's fracture, but 75% (3/4) of the anterior TD fracture had hangman's fracture. At admission, 13 patients were neurologically intact. However, the remaining patient had spinal cord injury with American Spinal Injury Association (ASIA) impairment scale B with C2-3 bilateral facet dislocation. All four anterior TD fracture patients underwent posterior C2-3 fusion. While four of 10 posterior TD fracture patients underwent C2-3 anterior fusion, the remaining six underwent posterior fusion. At last follow-up, 100% (14/14) of the patients achieved solid fusion, and visual analog scale for neck pain was significantly improved (5.9 vs 2.2, P < 0.001). One patient with ASIA impairment scale B had significantly improved to scale D. No major complications occurred. CONCLUSION: Our study showed that surgically managed TD fractures of the C2 showed a high incidence of other associated spine injuries including hangman's fracture and C2-3 discoligamentous injury. Therefore, special attention and careful radiologic evaluation are needed to investigate the presence of other associated spine injuries including hangman's fracture and C2-3 discoligamentous injury, which are likely to require surgery.

Evolution to Pedicle Reformation Technique in Surgical Management of Hangman's Fracture.

BACKGROUND: Opinions vary regarding optimal treatment of unstable hangman's fractures. Recent technological advances have allowed short segment, motion preserving fixation, even in complex cases. The aim of the study was to demonstrate C1-C2 motion-preserving short-segment fusion in hangman's fracture and the evolution of technique from pedicle realignment to pedicle reformation in complex fractures with resorbed/destroyed C2 pedicles. METHODS: This was a retrospective study. Patients operated by a single surgeon at a tertiary level center from 2012 to 2018 were included. The type of fracture, operating time, and blood loss was recorded. Neurologic deficits were recorded using the American Spinal Injury Association scale with regular clinicoradiologic follow-up. RESULTS: Nine patients (8 male), with a mean age of 36 ± 16.9 years were included. In the initial 7 patients, C2 pedicle screw, C3-C4 lateral mass screw, and rod fixation was done. The last 2 patients were complex neglected injuries, with 1 having severe angulation and displacement and the other having spondyloptosis with C2 body placed anterior to C4 body. In both these patients, direct C2 body screw were placed and pedicle reconstruction was done. Mean follow up was 41.4 ± 29.8 months. All 5 patients with preoperative neurologic deficits had improvement in power. C1-C2 joint motion was preserved in all. All patients had bony fusion. CONCLUSIONS: Preservation of motion at the C1-C2 joint should be the goal in all surgically managed hangman's fracture patients. The technique of C2 pedicle reconstruction can be utilized for the same in old neglected hangman's fractures.

Coexisting Retrocerebellar Arachnoid Cyst and Chiari Type 1 Malformation: 3 Pediatric Cases of Surgical Management Tailored to the Pathogenic Mechanism and Systematic Review of the Literature.

INTRODUCTION: Arachnoid cysts are benign cerebrospinal fluid collection within a duplication of arachnoid membrane and, when found in the retrocerebellar site, they may be associated with tonsils herniation. This rare situation of coexisting retrocerebellar arachnoid cyst (AC) and Chiari malformation type 1 (CM-1) have been previously reported in few cases (10 patients) with syringomyelia and hydrocephalus described to be the most relevant issues. The aim of this paper is to describe 3 pediatric cases of this condition with a systematic review of the literature, underlining the importance of surgical management tailored to the pathogenic mechanism. METHODS: A restrospective analysis of patients treated for coexisting CM-1 and ACs at the authors' institution has been carried out. RESULTS: A case of a 10-month-old baby with coexisting AC and CM-1 with tri-ventricular hydrocephalus treated with endoscopic third ventriculostomy, a case of a 1-year-old child with a huge retrocerebellar AC and CM-1 treated with a cysto-peritoneal shunt, and a case of a 15-year-old child with retrocerebellar AC causing symptomatic CM-1 treated with C0-C2 decompression, AC fenestration and duraplasty are described. A long-term follow-up is reported. CONCLUSIONS: Surgical management of coexisting ACs and CM-1 should not aim at the complete resolution of the cyst or of tonsil herniation, especially when pediatric patients are treated. Rather, the purpose of the neurosurgeon should be to understand the underlying pathogenic mechanism, and then restoring both the cerebrospinal fluid flow in the posterior fossa and the dynamic equilibrium between ventricles, cyst, and subarachnoid space.

Rate and Characteristics of Vertebral Artery Injury Following C1-C2 Posterior Cervical Fusion: A Systematic Review and Meta-Analysis.

BACKGROUND: Intraoperative vascular injuries in the cervical spine are rare, but carry significant morbidity and mortality when they do occur. There is a need to better characterize the risk of vertebral artery injury (VAI) after posterior C1-C2 fusion. The aim of this study was to investigate the rate of VAI in patients undergoing posterior C1-C2 cervical fusion. METHODS: An electronic database search was performed to identify studies that reported rates of VAI following posterior cervical fusion at C1-C2 level. Patient-specific risk factors, surgical indication, surgical technique, and other data were collected for each study. Forest plots were created to outline the pooled ratios of VAI in the literature. RESULTS: Eleven studies with 773 patients were identified. Mean age of patients was 48.47 years (range, 6-78 years), and most patients were female (61.7%, n = 399). Trauma was the most frequent indication for surgery (18.8%, n = 146), followed by inflammatory processes affecting the vertebrae (13.2%, n = 102). The rate of VAI per patient was 2% (95% confidence interval = 1%-4%) among 773 patients, while injury rate per screw was 1% (95% confidence interval = 0%-2%) among 2238 screws placed. CONCLUSIONS: The rate of VAI after C1-C2 posterior cervical fusion was found to be 2% for each operated patient and 1% for each screw placed.

Chondrosarcoma in the body of the C2 vertebral axis.

Chondrosarcoma, a malignant bone tumor, is rarely encountered in the cervical spine. This article describes a patient whose neck pain and dysphagia were caused by an expansive, destructive lesion with calcification that was located in the body of the axis (C2 vertebra), the first time a chondrosarcoma has been reported in this location.

Minimally invasive posterior percutaneous transarticular C1-C2 screws: how I do it.

BACKGROUND: Transarticular C1-C2 screw fixation, first described by Magerl, is a widely accepted used technique for C1-C2 instability with a good biomechanical stability and fusion rate. METHOD: We present a 69-year-old woman, who was diagnosed with a C2 Odontoid fracture type III and primarily treated with conservative treatment and collar. During first 2 weeks of follow-up, the patient developed cervical pain associated with C1-C2 instability. A minimally invasive posterior C1-C2 transarticular screw instrumentation with a percutaneus approach was performed. RESULTS AND CONCLUSION: Minimally invasive approach with tubular transmuscular approach for C1-C2 transarticular screws instrumentation is safe and effective for C1-C2 instability.

Management of C2 Body Giant Cell Tumor by Innovatively Fashioned Iliac Crest Graft and Modified Cervical Mesh Cage Used as Plate.

BACKGROUND: Locally aggressive vertebral body tumors of the axis must be treated with wide local excision for best outcome. Reconstruction of the load-bearing vertebra needs to be done after tumor resection in such a manner so as to give stable, long-term fusion in this young population. METHODS: We describe the management strategy of a 25-year-old acutely quadriplegic patient, with respiratory distress, with a C2 giant cell tumor. The use of a novel iliac crest graft modification used for C2 reconstruction along with a modified mesh cage used as an anterior plate has been reported. RESULTS: The patient had a good outcome at 18 months' follow-up, with neurologic improvement and a solid fusion. CONCLUSIONS: Iliac crest autograft is inexpensive and easy to harvest and can be considered as a C2 prosthesis, especially in a resource-constrained setting. Modified iliac crest graft can be used for load transmission from C1 lateral mass to C3 body, and the mesh cage can be modified according to need as a plate with good results in an emergency.

Occipital Plate Fixation in the Pediatric Population.

BACKGROUND: Occipital plate fixation has been shown to improve outcomes in cervical spine fusion. There is a paucity of literature describing occipital plate fixation, especially in the pediatric population. The authors reviewed a case series of 34 patients at a pediatric hospital who underwent cervical spine fusion with occipital plate fixation between 2003 and 2016. This study describes how occipital plates aid the cervical spine union in a case series of diverse, complex pediatric patients. METHODS: Our orthopaedic database at our institution was queried for patients undergoing an instrumented cervical spine procedure between 2003 and 2016. Medical records were used to collect diagnoses, fusion levels, surgical technique, and length of hospitalization, neurophysiological monitoring, complications, and revision procedures. RESULTS: Thirty-four patients met the inclusion criteria. The mean age was 10.9 years (range, 3-21 y). Indications for surgery included cervical instability, basilar invagination, and os odontoideum. These indications were often secondary to a variety of diagnoses, including trisomy 21, Klippel-Feil syndrome, and rheumatoid arthritis. The mean length of hospitalization was 10 days (range, 2 to 80 d). There were no cases of intraoperative dural leak, venous sinus bleeding from occipital screw placement, or implant-related complications. Postoperative complications included 2 cases of nonunion. Eight patients (24%) had follow-up surgery, only 3 (9%) of which were instrumentation revisions. Both patients with nonunion had repeat occipitocervical fixation procedures and achieved union with revision. CONCLUSIONS: Occipital plate fixation was successful for pediatric cervical spine fusion in this diverse cohort. The only procedure-related complication demonstrated was delayed union or nonunion and implant loosening (4/34, 12%) and there were no plate-related complications. This novel case series shows that occipital plate fixation is safe and effective for pediatric patients with complex diagnoses. LEVEL OF EVIDENCE: Level IV-case series.

C1-C2 Pedicle Screw Fixation for Pediatric Atlantoaxial Dislocation: Initial Results and Long-term Follow-up.

BACKGROUND: There are few studies reporting the use of atlantoaxial pedicle screws and the long-term effects of C1-C2 posterior fusion in children. Our study is to investigate the initial results of C1-C2 pedicle screw fixation for pediatric atlantoaxial dislocation (AAD) and assessed spontaneous change of postoperative radiography after a long-term follow-up period. METHODS: Posterior pedicle screw fixations were performed in 21 pediatric patients with AAD. All the patients underwent implant removal 1 year after their initial surgery and had regular follow-up with an average duration of 76.4 months (range, 52 to 117 mo). Clinical and radiographic data were then collected and compared. RESULTS: Frankel Grade was significantly improved at 3 months follow-up compared with pretreatment values. All patients had good bony fusion at a mean of 4.2±0.9 months (range, 3 to 6 mo) after treatment. None of the patients experienced worsening neurological symptoms or injury to the vertebral artery. However, 2 cases experienced minor complications. Following removal of the implants, no spinal deformities or subaxial instabilities were found. The mean angle of sagittal curvature increased from 12.1±2.4 degrees (range, 0 to 22 degrees) immediately postoperatively to 19.1±2.7 degrees (range, 6 to 31 degrees) at the final follow-up (P>0.05). CONCLUSIONS: The results demonstrated that C1-C2 pedicle screw fixation could achieve satisfactory initial results for the management of the pediatric AAD. Moreover, removal of the metal implant after bony fusion did not increase the risk of spinal deformity or subaxial instability at long-term follow-up.

Tailored Posterior-Only Approach for C2 Vertebral Body Lesions: Our Surgical Experience in 10 Patients.

BACKGROUND: C2 vertebral body (axis) lesions are often approached anteriorly and combined with posterior stabilization of the craniovertebral junction (CVJ). The anterior approach has its limitations. A posterolateral corridor is an alternative access to the C2 body lesions, and this alone may suffice in selected cases. We describe our experience with C2 body lesions, dealt primarily through a posterior approach, and propose an algorithm in the management of such cases. METHODS: Ten patients with axis lesions were operated through a midline posterior approach followed by posterior stabilization of the CVJ in the same sitting. Their preoperative and follow-up clinico-radiologic details were reviewed. RESULTS: The lesions included aneurysmal bone cysts (n = 2), fibrous dysplasia (n = 2), chordoma (n = 2), Ewing sarcoma (n = 1), metastases (n = 1), post-traumatic malunion (n = 1), and post-inflammatory deformity (n = 1). All patients presented with worsening neck pain. Five also had spastic quadriparesis. There were no perioperative complications. All showed clinical improvement at follow-up. Only 2 patients (chordoma: n = 1; aneurysmal bone cyst: n = 1) required an additional anterior procedure. CONCLUSIONS: Adequate debulking or total excision of lesion, neural decompression, and stabilization of the CVJ for axis body lesions can be achieved through a single midline posterior approach in most cases. If required, an anterior approach may be later added depending on the final histopathology.

IgG4-Related Disease of the Craniovertebral Junction.

BACKGROUND: The majority of the abnormalities and diseases that affect the craniovertebral junction (CVJ) have already been reported, and therefore it is exceedingly rare to identify new pathology that affects the CVJ. Immunoglobulin G4-related disease (IgG4-RD) is an immune mediated process treated with immunosuppressive medications. To our knowledge, this is the first reported case of IgG4-RD affecting the CVJ. CASE DESCRIPTION: The authors report the case of a woman aged 71 years with IgG4-RD of the CVJ. She presented with intractable left occipital pain and limited flexion, extension, and rotation of the neck. Computed tomography and magnetic resonance imaging revealed a lytic enhancing lesion of the left occipital condyle, left C1 lateral mass, and left C1 anterior arch resulting in cranial settling, basilar invagination, and CVJ instability. An open biopsy, subtotal resection, and occiput to C2 fusion was performed. Pathology revealed IgG4-RD. The patient was subsequently placed on rituximab immunotherapy with complete resolution of enhancement on magnetic resonance imaging and bone growth at the previous site of the lytic IgG4-RD lesion. CONCLUSIONS: To our knowledge, this case describes the first case of IgG4-RD affecting the CVJ, which mimicked a tumor-like process. When IgG4-RD affects the CVJ, stability must be accounted for, especially in the cases of osteolytic destruction. The combination of medical therapy to target the underlying inflammatory process and surgery to provide structural stability was successful.

Os Odontoideum: Analysis of 190 Surgically Treated Cases.

OBJECTIVE: The aim of this study was to report an experience with 190 cases of os odontoideum over 20 years. The management outcome following atlantoaxial fixation was analyzed. METHODS: From January 2000 to September 2018, 190 patients with os odontoideum were surgically treated. There were 113 male patients and 77 female patients; average age was 24 years (range, 2-68 years).The patients were divided into 3 groups depending on the nature of atlantoaxial dislocation (group 1, mobile and partially or completely reducible atlantoaxial dislocation; group 2, fixed or irreducible atlantoaxial dislocation; group 3, presence of basilar invagination). There were 65 pediatric patients (<18 years old). All patients underwent atlantoaxial joint manipulation and lateral mass plate and screw fixation. The goal of surgery was segmental atlantoaxial arthrodesis. No transoral or posterior foramen magnum bone decompression was done. Occipital bone was not included in the fixation construct. RESULTS: On direct bone handling and observation, atlantoaxial joint pathologic hyperactivity related instability was identified in all patients. Atlantoaxial segmental stabilization resulted in clinical symptomatic and neurologic improvement in 100% of patients. CONCLUSIONS: Os odontoideum signifies chronic or long-standing atlantoaxial instability. Segmental atlantoaxial fixation is a reliable form of surgical treatment. Bone decompression is not necessary. Inclusion of occipital bone and subaxial vertebrae in the fixation construct is not necessary.

The C2 "Parsicle" Screw: Introduction of a Novel Posterior Surgical Technique For Upper Cervical Fixation.

The instrumentation of C2 is technically challenging given the anatomic complexity of the upper cervical spine. Although the placement of C2 pedicle screws may be safer than transarticular screw placement, the inconsistent location of the transverse foramen and vertebral artery precludes placement of such screws in up to 26% of patients. In cases where vertebral artery anatomy prevents the safe placement of a pedicle screw, a pars screw is an excellent alternative. However, pars screws must stop short of the vertebral foramen, limiting the typical length of these screws to only 14-18 mm. The associated purchase and rigidity are compromised compared with the pedicle screw. A modified C2 fixation technique was developed by our group which we have named the C2 "parsicle" screw reflecting the hybrid nature of the screw incorporating aspects of pars and pedicle screw fixation.

Os Odontoideum in Children: Treatment Outcomes and Neurological Risk Factors.

BACKGROUND: Treatment outcomes and risk factors for neurological deficits in pediatric patients with an os odontoideum are unclear. METHODS: We reviewed the data for 102 children with os odontoideum who were managed at 11 centers between 2000 and 2016 and had a minimum duration of follow-up of 2 years. Thirty-one children had nonoperative treatment, and 71 underwent instrumented posterior cervical spinal arthrodesis for the treatment of C1-C2 instability. Nonoperative treatment consisted of observation (n = 29) or immobilization with a cervical collar (n = 1) or halo body jacket (n = 1). Surgical treatment consisted of atlantoaxial (n = 50) or occipitocervical (n = 21) arthrodesis. One patient also underwent transoral odontoidectomy. RESULTS: Thirty children (29%) presented with neurological deficits, 28 of whom had radiographic atlantoaxial instability (atlantoaxial distance >5 mm) or limited space (≤13 mm) available for the spinal cord (risk ratio, 7.8 [95% confidence interval, 2.0 to 31] compared with children with no radiographic risk factors). The 27 children without neurological deficits or atlantoaxial instability at presentation underwent nonoperative treatment and remained asymptomatic. Of the initial nonoperative cohort, one child developed atlantoaxial instability, and another had a persistent neurological deficit; both children underwent spinal arthrodesis during the study period. One child with cervical instability declined surgery and remained asymptomatic. Spinal fusion occurred in 68 patients in the surgical group by the end of the study period (mean, 3.7 years; range, 2.0 to 11.8 years). Surgical complications occurred in 21 children, including nonunion in 12, new neurological deficits in 4, cerebrospinal fluid leak in 2, symptomatic instrumentation requiring removal 2, and vertebral artery injury in 1. Nine children underwent revision surgery. In the surgical group, Japanese Orthopaedic Association neurological function scores improved significantly from preoperatively to the latest follow-up for the upper extremities (p = 0.026) and lower extremities (p = 0.007). CONCLUSIONS: The risk of developing a neurological deficit was strongly associated with atlantoaxial instability and limited space available for the spinal cord in children with os odontoideum. Nonoperative treatment was safe for asymptomatic patients without atlantoaxial instability. Spinal arthrodesis resolved the neurological deficits of children with symptomatic os odontoideum. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.