Comparison of iCT-based navigation and fluoroscopic-guidance for atlantoaxial screw placement in 78 patients with traumatic cervical spine injuries

BACKGROUND CONTEXT

Studies have shown biomechanical superiority of cervical pedicle screw placement over other techniques. However, accurate placement is challenging due to the inherent risk of neurovascular complications. Navigation technology based on intraoperative 3D imaging allows highly accurate screw placement, yet studies specifically investigating screw placement in patients with traumatic atlantoaxial injuries are scarce. The aim of this study was to compare atlantoaxial screw placement as treatment of traumatic instabilities using iCT-based navigation or fluoroscopic-guidance with intraoperative 3D control scans.

METHODS

This was a retrospective review of patients with traumatic atlantoaxial injuries treated operatively with dorsal stabilization of C1 and C2. Patients were either assigned to the intraoperative navigation or fluoroscopic-guidance group. Screw accuracy, procedure time, and revisions were compared.

RESULTS

Seventy-eight patients were included in this study with 51 patients in the navigation group and 27 patients in the fluoroscopic-guidance group. In total, 312 screws were placed in C1 and C2. Screw accuracy was high in both groups; however, pedicle perforations > 1 mm occurred significantly more often in the fluoroscopic-guidance group (P = 0.02). Procedure time was on average 23 min shorter in the navigation group (P = 0.02).

CONCLUSIONS

This study contributes to the available data showing that navigated atlantoaxial screw placement proves to be feasible as well as highly accurate compared to the fluoroscopic-guidance technique without prolonging the time needed for surgery. When comparing these data with other studies, the application of different classification systems for assessment of screw accuracy should be considered.

Rare Indication of Atlantoaxial Fusion-failed Conservative Management of Primary Atlantoaxial Osteoarthritis

Introduction

Osteoarthritis of the atlantoaxial joint is a significant cause of occipitocervical pain, which is often missed and has an increasing prevalence with age. The patients typically present with occipitocervical pain and restricted and painful neck rotations. Despite the primary reliance on conservative management for this pathology, surgical intervention becomes crucial for those not responding to standard conservative treatment. The presented case series highlights the rarity of the requirement of surgical intervention in the management of Atlantoaxial osteoarthritis (AAOA) and the clinical outcomes of surgical management in AAOA.

Case Report

This paper presents a case series of four patients who were managed surgically with atlantoaxial fusion, from a database of 108 patients with AAOA. The case series includes three males and one female with a mean age of presentation being 67.5 years. All four patients presented with occipitocervical pain, and painful neck movements and were diagnosed with AAOA on the anteroposterior open mouth view radiographs showing changes of osteoarthritis such as bone erosions, sclerosis, osteophytes. The patients were managed conservatively with non-steroidal anti-inflammatory drugs, intra-articular steroid injections, and cervical collar immobilization. Those not responding to conservative management and with incapacitating pain were managed surgically with atlantoaxial fusion procedures.

Conclusion

In a group of patients with a painful and debilitating degenerative AAOA only a small proportion of cases require surgical intervention. In this cohort, only 3.70 % of patients required surgery, highlighting the rarity of surgical intervention required in the management of AAOA. Nevertheless, when conducted, atlantoaxial fusion has proved to be efficacious with a low rate of serious complications and the patient self-rated outcome in terms of post-operative visual analog scale score and neck disability index scores indicating a high degree of satisfaction with the procedures.

Craniocervical fusion in the paediatric population - case series of 21 patients

PURPOSE

Craniocervical junction instability in a paediatric population presents a formidable challenge to the neurosurgeon. With a variety of anatomical variations, diminutive bony and ligamentous structures, possible superimposed syndromic abnormalities, the craniocervical junction is a technically challenging region to operate within. We aimed to review our series of patients to identify the common pathologies necessitating craniocervical fusion along with the use of intraoperative image guidance.

METHODS

We performed a retrospective review of twenty-one patients, with a mean age of 8.1 years, undergoing craniocervical fixations, involving either occipitocervical fusion or atlantoaxial fixation, from a single institution over a twelve-year period. The presentation, preoperative investigations, indication for surgery, surgical procedure, use of intraoperative navigation and clinical and radiological results were examined.

RESULTS

Twelve patients underwent primary C1-2 fixation, with the remaining 9 undergoing occipitocervical fusion. Five patients underwent surgery for traumatic instability, seven for os odontoideum, six for congenital anomalies and three for post-infectious instability. Follow up for 20 patients averaged 34 months (range 2-93 months). Five patients had Trisomy 21 and all underwent C1-2 fixation. Frameless stereotactic image guidance was utilised in five patients. No patients suffered immediate complications resulting from craniocervical junction fusion. Patients were observed to either neurologically improve (n = 6), or arrest their neurological deterioration following surgical intervention (n = 14), with concomitant radiological evidence of osseous fusion at follow up in 18 of 20 patients (90%). Two patients (10%) had radiological evidence of screw lucency, but neither required intervention because of being asymptomatic.

CONCLUSIONS

Craniocervical fixation in a paediatric population is a viable and safe treatment modality for the management of disorders requiring stabilisation at the craniocervical junction. Our experience of utilising frameless stereotaxy in the setting of grossly distorted anatomical landmarks is also reported.

Posterior realignment of basilar invagination with facet joint distraction technique

PURPOSE

We describe our experience with management of basilar invagination (BI) with the atlantoaxial dislocation (C1/C2) joint reduction technique, including posterior atlantoaxial internal fixation.

MATERIALS AND METHODS

From 2008 to 2018, eleven patients with atlantoaxial dislocation (AAD) and BI underwent surgical reduction using C1/C2 the joint reduction technique with a fibular graft/peek cage placement followed by C1 lateral mass/C2 pedicle screw fixation. In two cases that we originally planned to perform C1/C2 joint reduction, occiput-C2 pedicle screw fixation was performed instead due to intraoperative challenges. Post-operative course and surgical complications will be discussed.

RESULTS

A total of 13 patients, with an average age of 30.46 ± 13.23 years (range 12-57), were operated. In one patient, iatrogenic vertebral artery injury occurred without any neurological complication. JOA score improved from 10.45 ± 1.128 to 15.0 ± 1.949 (p < 0.0001, paired t-test). All radiological indices were improved (p at least < 0.001). No construct failure was seen in any of the patients with C1-2 facet joint distraction technique during follow-up, and no additional anterior decompression surgery was required.

CONCLUSIONS

C1/C2 joint reduction technique with fibular graft/cervical PEEK cage of BI patients together with AAD seems to be an effective and safe surgical method of treatment.

Acute abducens nerve palsy from a complex retro-odontoid pseudotumor with a protrusion: A case report

Retro-ondontoid pseudotumors represent soft tissue proliferation surrounding the transverse ligament of the atlas, which most commonly results in cervical neck pain or myelopathy due to impingement upon the cervicomedullary junction. The causes of retro-odontoid pseudotumor formation are varied and include metabolic, inflammatory, degenerative, and post-traumatic etiologies. To the best of our knowledge, an abducens nerve palsy as a result of a complex retro-odontoid pseudotumor has never been reported. We discuss a case of a 90-year-old woman who presents with acute lateral gaze palsy with multimodality imaging demonstrating a retro-odontoid pseudotumor with an unusual protrusion which courses superolaterally to the level of the pons and compresses the abducens nerve root entry zone.

The demographic, clinical, and management differences between traumatic dens fracture patients with and without simultaneous atlas fractures

Introduction

Atlas fractures often accompany traumatic dens fractures, but existing literature on the management of simultaneous atlantoaxial fractures is limited.

Methods

We examined all patients with traumatic dens fractures at our institution between 2008 and 2018. We used multivariable logistic regression and ordinal logistic regression to identify factors independently associated with presentation with a simultaneous atlas fracture, as well myelopathy severity, fracture nonunion, and selection for surgery.

Results

Two hundred and eighty-two patients with traumatic dens fractures without subaxial fractures were identified, including 65 (22.8%) with simultaneous atlas fractures. The distribution of injury mechanisms differed between groups (χ2 P = 0.0360). On multivariable logistic regression, dens nonunion was positively associated with type II fractures (odds ratio [OR] = 2.00, P = 0.038) and negatively associated with having surgery (OR = 0.52, P = 0.049), but not with having a C1 fracture (P = 0.3673). Worse myelopathy severity on presentation was associated with having a severe injury severity score (OR = 102.3, P < 0.001) and older age (OR = 1.28, P = 0.002), but not with having an atlas fracture (P = 0.2446). Having a simultaneous atlas fracture was associated with older age (OR = 1.29, P = 0.024) and dens fracture angulation (OR = 2.62, P = 0.004). Among patients who underwent surgery, C1/C2 posterior fusion was the most common procedure, and having a simultaneous atlas fracture was associated with selection for occipitocervical fusion (OCF) (OR = 14.35, P = 0.010).

Conclusions

Among patients with traumatic dens, patients who have simultaneous atlas fractures are a distinct subpopulation with respect to age, mechanism of injury, fracture morphology, and management. Traumatic dens fractures with simultaneous atlas fractures are independently associated with selection for OCF rather than posterior cervical fusion alone.

Comparison of the clinical efficacy of unilateral and bilateral pedicle screw short-segment fixation and fusion in the treatment of atlantoaxial fracture-dislocation

BACKGROUND

Few studies have compared the clinical efficacy of unilateral and bilateral pedicle screw fixation and fusion in treating atlantoaxial fracture-dislocation.

OBJECTIVE

To compare the efficacy of unilateral and bilateral fixation and fusion for atlantoaxial fracture-dislocation and to explore the feasibility of the unilateral surgical procedure.

METHODS

Twenty-eight consecutive patients with atlantoaxial fracture-dislocation were included in the study from June 2013 to May 2018. They were divided into a unilateral fixation group and a bilateral fixation group (14 patients in each group with an average age of 43.6 ± 16.3 years and 51.8 ± 15.4 years, respectively). The unilateral group had a unilateral anatomical variation of the pedicle or vertebral artery, or traumatic pedicle destruction. All patients underwent atlantoaxial unilateral or bilateral pedicle screw fixation and fusion. Intraoperative blood loss and operation time were recorded. The visual analog scale (VAS) and Japanese Orthopedic Association (JOA) scoring systems were used to evaluate pre- and postoperative occipital-neck pain and neurological function. X-ray and computerized tomography (CT) were used to assess atlantoaxial stability, the implants' position, and bone graft fusion.

RESULTS

All patients were followed up for 39-71 months postoperatively. Intraoperatively, no spinal cord or vertebral artery injury was observed. At the last follow-up, occipital-neck pain and neurological function in the two groups were significantly improved (P< 0.05). The X-ray films and CT showed satisfactory atlantoaxial stability, implant position, and osseous fusion in all the patients at 6 months postoperatively.

CONCLUSION

Unilateral and bilateral pedicle screw fixation and fusion can restore atlantoaxial stability and improve occipital-neck pain and neurological function in patients with atlantoaxial fracture-dislocation. The unilateral surgical procedure can be a supplementary option for patients with unilateral abnormal atlantoaxial lesions.

Nontraumatic atlantoaxial rotatory subluxation in adults: Report of two cases

Background

Nontraumatic infectious atlantoaxial rotatory subluxation (AARS) is rare and less frequently encountered in adults versus children. We utilized a stepwise approach to treat two adults with nontraumatic infectious AARS and summarized the relevant literature.

Case Description

Two patients, ages 35 and 66, presented with classic clinical and imaging findings for infectious nontraumatic AARS. Here, we summarized the management for these two patients along with the literature.

Conclusion

Nontraumatic infectious AARS in adults requires prompt X-ray diagnosis and timely application of traction to minimize neurological deficits. MR/CT imaging next offers critical information regarding whether operative stabilization is warranted.

Referencing for anterior atlantoaxial trans-articular osteosynthesis: a radiological study and proposal of a decisional algorithm

PURPOSE

Anterior trans-articular C1-C2 screw placement can be considered as a surgical alternative in different conditions affecting the atlantoaxial region. While its rigidity is similar to posterior Magerl and Harms techniques, it also provides some surgical advantages. However, the literature lacks papers exhaustively describing indication criteria, surgical steps, and pitfalls.

METHODS

This is a radiological study on 100 healthy subjects. Thin-layer CT scans of the craniovertebral junction were retrieved from the institutional database. The coronal inclination of the C1-C2 joint rim and the depth of the entry point of the screw with respect to the anterior profile of C2 were measured. The antero-posterior and the medio-lateral surgical corridors for the screw placement, and the wideness of the target area on the upper surface of C1 were also measured.

RESULTS

The multivariate analysis showed that the coronal inclination of the C1-C2 articular joint rim strongly influences the surface extension of the C1 target area; the depth of the entry point and the C1-C2 articular rim inclination seem to be independent factors in influencing both the medio-lateral and the antero-posterior surgical corridors wideness. A decisional algorithm on whether to perform an anterior or posterior approach to the atlantoaxial region was also proposed.

CONCLUSIONS

We can conclude that, as much as the C1-C2 articular rim is tending to the horizontal line, and as deeper is the entry point of the screw on the anterior profile of C2, as easier the anterior C1-C2 trans-articular screw placement will result.

Atlantoaxial stenosis after muscle-preserving selective laminectomy

There are few reports of degenerative atlantoaxial stenosis and new stenosis after cervical decompression. We experienced four cases of atlantoaxial stenosis after muscle-preserving selective laminectomy. We compared these four cases with no stenosis cases after long-term follow-up of selective laminectomy, as well as healthy subjects. A total of 1205 patients who underwent muscle-preserving selective laminectomy due to cervical disorders were included in this study. Postoperative atlantoaxial stenosis, which needed decompression, appeared in 4 cases, and 30 patients did not have radiological stenosis for more than 10 years after surgery. Twenty healthy volunteers were also used as controls. The radiographic parameters measured were C2-C7 angle, C2-C7 sagittal vertical axis (SVA), C2 slope, C7 slope, C2-C5 angle, C5-C7 angle, C1-C2 angle, and atlantodental interval (ADI). We measured the anterior-posterior (AP) diameters of the spinal cord (SC) and dural tube (Dura) at C1/C2 with sagittal MRI. In the cases of atlantoaxial stenosis, the AP of SC and Dura at C1/C2 were smaller preoperatively, and the residual space for SC (SAC) was also smaller. The preoperative ADI was significantly higher in patients with atlantoaxial stenosis, suggesting preoperative instability at C1/C2. Analysis of the ROC curve showed that patients with a preoperative SAC of less than 3.6 mm and an ADI of more than 1.35 mm were more likely to develop postoperative atlantoaxial stenosis. When we perform a muscle-preserving selective laminectomy, decompression of C1/C2 is suggested when the SAC at C1/C2 is less than 3.6 mm and the ADI is more than 1.35 mm.

Consensus practice guidelines on interventions for cervical spine (facet) joint pain from a multispecialty international working group

BACKGROUND

The past two decades have witnessed a surge in the use of cervical spine joint procedures including joint injections, nerve blocks and radiofrequency ablation to treat chronic neck pain, yet many aspects of the procedures remain controversial.

METHODS

In August 2020, the American Society of Regional Anesthesia and Pain Medicine and the American Academy of Pain Medicine approved and charged the Cervical Joint Working Group to develop neck pain guidelines. Eighteen stakeholder societies were identified, and formal request-for-participation and member nomination letters were sent to those organizations. Participating entities selected panel members and an ad hoc steering committee selected preliminary questions, which were then revised by the full committee. Each question was assigned to a module composed of 4-5 members, who worked with the Subcommittee Lead and the Committee Chairs on preliminary versions, which were sent to the full committee after revisions. We used a modified Delphi method whereby the questions were sent to the committee en bloc and comments were returned in a non-blinded fashion to the Chairs, who incorporated the comments and sent out revised versions until consensus was reached. Before commencing, it was agreed that a recommendation would be noted with >50% agreement among committee members, but a consensus recommendation would require ≥75% agreement.

RESULTS

Twenty questions were selected, with 100% consensus achieved in committee on 17 topics. Among participating organizations, 14 of 15 that voted approved or supported the guidelines en bloc, with 14 questions being approved with no dissensions or abstentions. Specific questions addressed included the value of clinical presentation and imaging in selecting patients for procedures, whether conservative treatment should be used before injections, whether imaging is necessary for blocks, diagnostic and prognostic value of medial branch blocks and intra-articular joint injections, the effects of sedation and injectate volume on validity, whether facet blocks have therapeutic value, what the ideal cut-off value is for designating a block as positive, how many blocks should be performed before radiofrequency ablation, the orientation of electrodes, whether larger lesions translate into higher success rates, whether stimulation should be used before radiofrequency ablation, how best to mitigate complication risks, if different standards should be applied to clinical practice and trials, and the indications for repeating radiofrequency ablation.

CONCLUSIONS

Cervical medial branch radiofrequency ablation may provide benefit to well-selected individuals, with medial branch blocks being more predictive than intra-articular injections. More stringent selection criteria are likely to improve denervation outcomes, but at the expense of false-negatives (ie, lower overall success rate). Clinical trials should be tailored based on objectives, and selection criteria for some may be more stringent than what is ideal in clinical practice.

Transoral release to realign postoperative loss of reduction following occipitocervical fixation for congenital basilar invagination

PURPOSE

Revision surgery in an irreducible atlantoaxial dislocation (IAAD) previously operated with a posterior approach is challenging. Multiple modalities using anterior, posterior, and dual approaches have been described. We report a so far unreported technique of revision surgery by posterior implant removal and decompression with anterior transoral release followed by posterior instrumentation.

METHODS

14-year male with basilar invagination (BI) with IAAD, previously operated with posterior decompression and instrumented occipitocervical fusion presented three months later with post-traumatic recurrence of myelopathy with quadriparesis with Di Lorenzo grade 4 and loss of reduction. He was operated with a posterior implant and early fusion mass removal with extended foramen magnum decompression (FMD), followed by anterior transoral release with a satisfactory reduction on traction, and finally, a posterior revision instrumented occipitocervical fusion.

RESULTS

At 2-year follow-up, the patient was symptom-free with Di Lorenzo grade 1 and cervicomedullary angle improvement from 97.4° to 141.2°; achieving bony fusion.

CONCLUSION

Single-stage posterior-anterior transoral-posterior approach can be used to achieve satisfactory reduction for a revision BI with IAAD with prior posterior instrumentation.

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.

Usefulness of ipsilateral translaminar C2 screws insertion for cervical fixation in children with a low laminar profile: a technical note

PURPOSE

The fusion of the upper cervical spine in children is demanding due to its reduced size, its anatomical complexity, or a severe pathology of the cranio-cervical junction. In some pediatric patients with today's more popular C1-C2 or, occipito-C2 techniques, it is impossible, or very risky to perform a short upper cervical fixation.

METHODS

We present the utility and good results of ipsilateral laminar C2 screws insertion technique in two pediatric cases with low C2 laminar profile. Case 1: a 5-year-old child with a C1-C2 unstable subluxation, and a condylar assimilation of C1, where we performed an occipito-C2 fixation using an occipital plate and this modified translaminar C2 screw technique. Case 2: a 8-year-old Down syndrome boy who suffered an unstable subluxation of C1-C2 upon whom we performed a C1-C2 screw fixation using the same technique.

RESULTS

Both cases have been followed up over a period of 7 and 2 years respectively, with good clinical results.

CONCLUSIONS

We describe the technique and the feasibility of the ipsilateral insertion of translaminar C2 screws in children with low laminar profiles, as a good alternative to other techniques when the anatomy of the C2 does not permit its use or make them very risky.

Muscle Sparing C1-C2 Laminoplasty: Cadaveric Feasibility Study

BACKGROUND

Posterior cervical approaches for atlantoaxial and craniovertebral junction pathologies with or without instrumentation are often associated with excessive soft tissue dissection and bleeding consequent with disruption of the venous plexus. A few minimally invasive approaches to this region have been reported from clinical and cadaveric studies in an effort to minimize blood loss, reduce soft tissue dissection, and decrease postoperative pain; however, unilateral minimally invasive approaches have not been described. Here, we describe a minimally invasive atlantoaxial and craniovertebral approach.

METHODS

Using fresh cadavers, we performed a novel, right-sided, muscle-sparing minimally invasive C1-C2 laminotomy with laminoplasty for access to the atlantoaxial level and craniovertebral junction and used the traditional approach on left sides.

RESULTS

Using this approach, the atlantoaxial space and craniovertebral junction with wide and generous exposure via unilateral soft tissue dissection and muscle splitting was achieved. After exposure, the musculoosseous unit was easily repositioned, thus allowing for C1-C2 laminoplasty. Grossly, no damage to the vertebral artery or regional nerves was noted.

CONCLUSIONS

We present a novel, unilateral minimally invasive approach to reach the atlantoaxial and craniovertebral junction. This could allow for faster postoperative recovery, less pain and opioid requirement, and increased maintenance of atlantoaxial stability. Such a technique, after being confirmed in patients, could optimize this surgical technique.

Traumatic atlantoaxial rotatory subluxation in adults - A case report and literature review

Background:

Traumatic atlantoaxial rotatory subluxation (AARS) is extremely rare in adult versus pediatric populations. Patients usually present with post-traumatic neck pain and torticollis. Surgical management aims at reducing the deformity and stabilizing the spine utilizing external orthotics, and/or internal reduction/fixation.

Methods:

A 65-year-old female fell downstairs at home. She complained of neck pain with right-sided tenderness and torticollis. The radiographic studies and CT scan demonstrated AARS. This led to an emergent open reduction with internal fixation at the C1-C2 level.

Results:

We identified 25 similar cases of AARS in the English literature. Patients averaged 28.7 years of age and mostly sustained motor vehicle accidents largely treated with traction/orthotics; only six patients required surgical open reduction/internal fixation.

Conclusion:

In this case, the patient’s C1-C2 deformity required open reduction/internal fixation rather than bracing alone.

Biomechanics of the effect of subaxial cervical spine degeneration on atlantoaxial complex in idiopathic retro-odontoid pseudotumor development

OBJECTIVES

Retro-odontoid pseudotumor (ROP), with no rheumatoid arthritis, atlantoaxial instability, or other primary diseases, is defined as idiopathic retro-odontoid pseudotumor (IROP). Cervical spine degeneration is associated with IROP development. This study aims to evaluate the effect of cervical spine degeneration on the atlantoaxial complex and find the possible biomechanical mechanism of IROP development.

METHODS

This study was performed using a three-dimensional (3D) finite element (FE) analysis. A degenerated FE model (FEM) and five operation FEMs (C1-C2 fusion, C0-C2 fusion, C0-C3 fusion, C0-C4 fusion, and C1 posterior arch resection) were established based on a normal 3D FEM of the cervical spine including C0-T1 with the main ligaments and muscles. The parameters, including the C1-C2 range of motions (ROMs) and odontoid-related ligaments' stresses in degenerated and operation FEMs, were obtained and compared with those in normal FEM.

RESULTS

Compared to normal FEM, degenerated FEM had reduced C3-C7 ROMs and increased C1-C2 ROMs and odontoid-related ligaments' stresses. After internal fixation, C1-C2 ROMs and most odontoid-related ligaments' stresses were greatly decreased, but with no significant differences among C0-C2, C0-C3, C0-C4, and C1-C2 fusion models. For the C1 posterior arch resection model, C1-C2 ROMs and most odontoid-related ligaments' stresses increased, compared with normal FEM.

CONCLUSIONS

Cervical spine degeneration plays an important part in IROP development in biomechanics. Atlantoaxial complex compensates for cervical spine degeneration, with increased C1-C2 ROMs and odontoid-related ligaments' stresses. Atlantoaxial fusion or short segmental occipitocervical fusion can effectively reduce the stress and should be considered in IROP treatment.

Analysis of Risk Factors for Posterior C1 Screw-Related Complication: A Retrospective Study of 358 Posterior C1 Screws

BACKGROUND

Although C1 screw fixation is becoming popular, only a few studies have discussed about the risk factors and the patterns of C1 screw complications.

OBJECTIVE

To investigate the incidence of C1 screw complications and analyze the risk factors of the C1 screw complications.

METHODS

A total of 358 C1 screws in 180 consecutive patients were analyzed for C1 screw complications. Screw malposition, occipital neuralgia, major complications, and total C1 screw complications were analyzed.

RESULTS

The distribution of C1 screw entry point is as follows: inferior lateral mass, 317 screws (88.5 %); posterior arch (PA), 38 screws (10.7 %); and superior lateral mass, 3 screws (0.8 %). We sacrificed the C2 root for 127 screws (35.5 %). C1 instrumentation induced 3.1 % screw malposition, 6.4 % occipital neuralgia, 0.6 % vascular injury, and 3.4 % major complications. In multivariate analysis, deformity (odds ratio [OR]: 2.10, P = .003), traumatic pathology (OR: 4.97, P = .001), and PA entry point (OR: 3.38, P = .001) are independent factors of C1 screw malposition. C2 root resection can decrease the incidence of C1 screw malposition (OR: 0.38, P = .012), but it is a risk factor of occipital neuralgia (OR: 2.62, P = .034). Advanced surgical experience (OR: 0.09, P = .020) correlated with less major complication.

CONCLUSION

The incidence of C1 screw complications might not be uncommon, and deformity or traumatic pathology and PA entry point could be the risk factors to total C1 screw complications. The PA screw induces more malposition, but less occipital neuralgia. C2 root resection can reduce screw malposition, but increases occipital neuralgia.

Pyogenic Atlantoaxial Rotational Dislocation Representing Adult Torticollis with Vertebral Artery Occlusion: A Case Report and Review

BACKGROUND

Pyogenic atlantoaxial rotational dislocation is a rare but life-threatening condition. Disease progression damages the soft tissue and bony structure, resulting in spinal cord or brain stem compression. Rapid and correct diagnosis could enable successful treatment. However, few studies have been reported, and the characteristics of a successful treatment course are not well known. In addition, our case presented with vertebral artery (VA) occlusion. Here we present a report of successful treatment of pyogenic atlantoaxial rotational dislocation representing adult torticollis with VA occlusion.

CASE DESCRIPTION

A 67-year-old woman with neck pain and high fever was treated for suspected meningitis. Although her fever improved, pain persisted for several weeks. Examinations mostly showed characteristics of an infection with destructive atlantoaxial rotational dislocation; however, positive uptake with positron emission tomography, no anomalies with diffusion-weighted magnetic resonance imaging, and VA occlusion indicated the presence of a tumor lesion. After VA embolization and Halo reduction/stabilization, biopsy and blood culture revealed pyogenic infection. Antibiotics with rigid stabilization improved the inflammation and allowed definitive occipitocervical fixation, resulting in an uneventful postoperative course and painless bony fusion 2 years postoperatively.

CONCLUSIONS

VA involvement should be examined for safe treatment. Stabilization is warranted to improve chronic inflammation. Knowledge regarding the characteristic treatment course could enable successful treatment planning and may prove to be lifesaving.

Clinicoradiological outcomes of Goel and Harms fixation for atlantoaxial instability: An institutional experience

Background

Few studies have reported on the long-term outcomes of Goel and Harms C1-C2 fusions in the Asian population.

Methods

This was a retrospective analysis of 53 patients undergoing Goel and Harms fixation (2010 -2018). Clinical outcomes were assessed utilizing the neck disability index (NDI), Japanese Orthopedic Association (JOA) score, and visual analog scale (VAS). Outcomes were then correlated with fusion rates (using dynamic X-rays), atlanto-dens interval (ADI), and space available for cord (SAC) data.

Results

The study's 53 patients averaged 49.98 years of age and included 42 males and 11 females. The mean preoperative versus postoperative scores on multiple outcome measures showed NDI 31.62 ± 11.05 versus decreased to 8.68 ± 3.76 post, mean JOA score (e.g., in 41 patients with myelopathy) improved from 13.20 ± 3.96 to 15.2 ± 2.17, and the mean VAS decreased from 4.85 ± 1.03 to 1.02 ± 0.87 and showed restoration of the ADI (1.96 ± 0.35 mm) and SAC (20.42 ± 0.35 mm). A 98.13% rate of C1-C2 fusion was achieved at 12 postoperative months.

Conclusion

Goel and Harms technique for C1-C2 fusion resulted in both good clinical and radiological outcomes.

Technical outcome of atlantoaxial transarticular screw fixation without supplementary posterior construct for rheumatoid arthritis

Background

transarticular screw (TAS) fixation without a supplementary posterior construct, even in rheumatoid arthritis (RA) patients, provides sufficient stability with acceptable clinical results. Here, we present our experience with 15 RA patients who underwent atlantoaxial (AA) TAS fixation without utilizing a supplementary posterior fusion.

Methods

To treat AA instability, all 15 RA patients underwent C1-C2 TAS fixation without a supplementary posterior construct. Patients were followed for at least 24 months. Pre- and postoperative sagittal measures of C1- C2, C2-C7, and C1-C7 angles, atlanto-dens interval (ADI), posterior atlanto-dens interval (PADI), and adjacent segment (i.e., C2-C3) anterior disc height (ADH) were retrospectively recorded from lateral X-ray imaging. The presence or absence of superior migration of the odontoid (SMO), cervical subaxial subluxation, C1-C2 bony fusion, screw pull-out, and screw breakage were also noted.

Results

There was little difference between the pre- and postoperative studies regarding angles measured. Following TAS fixation, the mean ADI shortened, and mean PADI lengthened. There was no difference in the mean measures of C2-C3 ADH. There was no evidence of SMO pre- or postoperatively. Two patients developed anterior subluxation at C5-C6; one of the two also developed anterior subluxation at C2-C3. All patients subsequently showed C1-C2 bony fusion without screw pull-out or breakage.

Conclusion

In RA patients who have undergone C1-C2 TAS fixation, eliminating a supplementary posterior fusion resulted in adequate stability.

Bibliometric and Visualized Analysis of Scientific Publications on Atlantoaxial Spine Surgery Based on Web of Science and VOSviewer

BACKGROUND

Atlantoaxial spine surgery is a challenge to spinal surgeons because of its proximity to neurovascular structures. This study aimed to identify and analyze the scientific publications in atlantoaxial spine surgery from different countries and institutions.

METHODS

Clarivate Analytics Web of Science was used to search all articles for information on atlantoaxial spine surgery. The annual research, countries, journals, authors, institutions, citation frequency, and journal metrics were extracted. These results from countries and hotspots (keywords in publications) were subjected to co-occurrence analysis using VOSviewer, after which the top 100 most-cited articles were analyzed further.

RESULTS

A total of 3161 articles were included. A trend toward an increasing number of publications on atlantoaxial spine surgery in recent years was evident. Among all countries, the United States contributed the most publications. Seth Gordhandas Sundarda Medical College had the highest number of publications among institutions. Among all research categories, fixation and fusion were the most common areas discussed. The screw-rod system described in the most-cited article (cited 823 times) appeared to be the most popular fixation method. With the development of C1 and C2 screw technology, the screw-rod system is becoming increasingly popular.

CONCLUSIONS

The atlantoaxial spine surgery literature has grown continuously in recent years. The United States is the largest contributor in this field. Fixation and fusion are the most common areas, and fixation-related studies should be closely followed. The screw-rod fixation system is becoming increasingly popular.

Thinking beyond pannus: a review of retro-odontoid pseudotumor due to rheumatoid and non-rheumatoid etiologies

Retro-odontoid pseudotumor, or mass-like retro-odontoid soft tissue thickening, is an uncommon but important imaging finding that may be associated with rheumatoid arthritis, crystal deposition diseases, as well as non-inflammatory conditions such as cervical degenerative changes and mechanical alterations. Retro-odontoid pseudotumor is commonly associated with atlantoaxial microinstability or subluxation. MRI and CT have an important role in the detection and diagnosis of retro-odontoid pseudotumor. However, due to a wide range of imaging characteristics and ambiguous etiology, it is a frequently misunderstood entity. The purpose of this article is to review relevant anatomy of the craniocervical junction; describe various imaging appearances, pathophysiology and histology in both rheumatoid and non-rheumatoid etiologies; and discuss differential diagnosis of retro-odontoid pseudotumor in order to help guide clinical management.

Transnasal and Transoral Approaches to Atlantoaxial Synovial Cysts: Report of 3 Cases and Review of the Literature

BACKGROUND

Synovial cysts are cystic masses lined with pseudostratified columnar cells and containing clear or xanthochromic fluid. Although they are commonly encountered in the lumbar spine, synovial cysts infrequently occur in the cervical spine and rarely involve the odontoid process. The causes of synovial cysts of the odontoid process are unknown, but growth of synovial rests, proliferation of multipotent mesenchymal cells, atlantoaxial instability, and trauma are thought to play a role.

CASE DESCRIPTION

We present 3 cases of atlantoaxial cysts with the associated radiographic features, surgical management, and clinical outcomes. No patient had rheumatoid arthritis. In all cases, preoperative differential diagnosis included neoplastic pathologic changes. Two patients underwent odontoidectomy through either an endonasal or a transoral approach, followed by posterior occipitocervical fusion. The third patient underwent an endoscopic transsphenoidal approach for cyst decompression.

CONCLUSIONS

Tissue diagnosis is important in confirming pathologic analysis because synovial cysts have radiographic characteristics similar to those of a wide variety of neoplasms of the craniovertebral junction.

Brucella Case That Led to Atlantoaxial Spinal Instability in Childhood

BACKGROUND

Atlantoaxial subluxation caused by Brucella infection is rarely seen in children.

CASE DESCRIPTION

C1-C2 dislocation, erosion in the odontoid bone, and compression to the brainstem were detected on cervical computed tomography and magnetic resonance imaging in a 6-year-old patient who suffered neck pain, deviation to the right in the neck, fever, and pain in his extremities. He was hospitalized in the Clinic of Pediatric Infectious Diseases. Positive Brucella agglutination tests were obtained, so C1-C2 stabilization and fusion were performed. Antibrucellosis antibiotic treatment was administered for 6 months. It was suggested that the dislocation was related to odontoid erosion and laxity of the atlantoaxial ligamentous structures during Brucella infection.

CONCLUSIONS

Atlantoaxial dislocation and instability develops secondarily to paravertebral abscesses, only rarely. Like brucellosis of childhood, granulomatous infectious diseases rarely cause atlantoaxial subluxation or dislocation. Torticollis and neck pains should be taken seriously for the purpose of early diagnosis of patients at risk in endemic regions. Stabilization and fusion should be performed when instability is detected, and these patients should be assessed with both pediatric infectious diseases and neurosurgery clinics. Our case is the first one in the literature in which atlantoaxial instability developed due to Brucella infection and stabilization was performed.

Endoscopic transnasal anterior release and posterior reduction without odontoidectomy for irreducible atlantoaxial dislocation

Background

To investigate the efficacy and safety of endoscopic transnasal anterior release and posterior reduction without odontoidectomy to treat irreducible atlantoaxial dislocation (IAAD).

Methods

A series of 9 patients with IAAD underwent endoscopic transnasal anterior release and posterior reduction without odontoidectomy. Etiology, instrumentation, fusion rate, and complications were documented. All patients were assessed clinically and radiologically for neurological recovery using the Japanese Orthopedic Association (JOA) score, atlantodontoid interval (ADI), and cervicomedullary angle (CMA).

Results

The mean age of the patients was 41.6 years, ranging from 14 to 60 years. Pathology showed os odontoideum in 3 patients, old traumatic dens fracture in 3 patients, occipitalization of C1 in 2 patients, and rheumatoid arthritis in 1 patient. Seven patients underwent C1–C2 pedicle screw fixations, and 2 patients required occipitocervical fixation. Eight cases resulted in complete reduction and 1 in partial reduction. Complications included one superficial infection related to the posterior approach. All patients were followed up for an average of 17 (range 13–32) months. Bony fusion was confirmed in all cases under radiologic assessment at 1 year postoperatively, and the bony fusion rate reached 100%. Moreover, no instrumental failure occurred during the entire follow-up period. The JOA score improved from 7.21 ± 1.62 to 12.28 ± 0.81 at the last follow-up. The ADI of 9 cases was 7.06 ± 0.85 mm preoperatively, which decreased to 2.26 ± 0.56 mm at the final follow-up. CMA improved from 103.80° ± 4.16° to 143.23° ± 7.47° postoperatively.

Conclusion

With transnasal approach and lack of odontoidectomy, this method could not only treat IAAD safely and effectively, but also reduce the possibility of many complications associated with the traditional transoral approach and odontoidectomy.

Cervical vertebral malformations in 9 dogs: radiological findings, treatment options and outcomes

Background

Disregarding atlantoaxial instability in toy breed dogs associated with dens malformation and cervical spondylomyelopathy; cervical vertebral malformations are rare and poorly characterised in veterinary medicine and consequently treatment strategies and clinical outcome are sparsely documented.

Results

Electronic clinical records at our veterinary referral hospital between April 2009 and November 2018 were searched for patients presented with cervical myelopathy secondary to an underlying suspected vertebral malformation/instability. Nine dogs met the inclusion criteria. Two dogs were diagnosed with atlantoaxial pseudoarthrosis, two dogs with a syndrome similar to Klippel-Feil in humans, two dogs with congenital cervical fusion, two dogs with congenital C2-C3 canal stenosis and deficiencies of the dorsal arch of the atlas and laminae of the axis and one with axial rotatory displacement. Tetraparesis, proprioceptive deficits, cervical hyperesthesia and cervical scoliosis were the most common clinical signs. The axis was the most commonly affected vertebrae (8/9 patients). Patients diagnosed with Klippel-Feil-like Syndrome were the younger (average of 262.5 days) and patients diagnosed with fused vertebrae the oldest (average of 2896 days) in our studied population (average of 1580.8 days).

Conclusion

Cervical vertebral malformations are rare, or alternatively, being underdiagnosed in veterinary medicine. Patients diagnosed with Klippel-Feil-like Syndrome had a successful medium and long-term outcome with conservative management. Surgical treatment was often indicated for the other conditions presented in this study due to spinal instability and/or myelopathy. Stabilisations via ventral approaches were revealed to be safe. Multicentre and prospective studies are necessary in veterinary medicine to better characterise clinical outcomes in cervical vertebral malformations.

Evaluation of clinical outcomes of one-stage anterior and posterior surgical treatment for atlantoaxial tuberculosis complicated with neurological damage

Background

Surgical treatment is mainly used for atlantoaxial tuberculosis with neurological damage. However, the anatomic structure around the atlantoaxial joint is complex, and the position of vertebral body is deep, which increases the difficulty of the operation and it is challenging for the surgeon to develop surgical strategy. The purpose of this study was to evaluate the clinical outcomes of one-stage combined anterior and posterior surgical treatment approach for atlantoaxial tuberculosis with neurological impairment.

Methods

From January 2005 to January 2015, 12 patients suffering from atlantoaxial tuberculosis with neurological impairment were surgically treated by one-stage combined anterior and posterior approach. Preoperative CT scanning and MRI imaging showed unilateral or bilateral lateral mass destruction of the atlas, and varying destruction degrees of odontoid process, loss of atlantoaxial stability, and tuberculosis focus into the spinal canal resulting in the corresponding spinal cord compression in all patients. The preoperative neurological classifications were Class C for 4 cases, D for 8 cases according to the American Spinal Injury Association (ASIA) system. Quadruple sensitive anti-TB drug treatment was used in all 12 patients preoperative and postoperative. Patients’ clinical symptoms and neurological function recovery were evaluated by comparing the Visual Analogue Scale (VAS) score, Neck Disability Index (NDI), Japanese Orthopedic Association (JOA) score and ASIA grading before operation and at the final follow-up.

Results

Mean surgical duration was 263.3 ± 43.6 min. Intraoperative blood loss was averagely 529.2 ± 169.8 ml. The average fusion period was 7.3 ± 1.5 months. No instrumentation loosening, migration or breakage was observed during the follow-up of 6.5 ± 2.9 years. The VAS, NDI and JOA scores were significantly changed to 1.00 ± 0.95, 9.50 ± 3.34 and 15.42 ± 1.44 at last follow-up (P < 0.05). The neurological function of all 12 patients was recovered to Class E according to the ASIA grading system.

Conclusion

In the treatment of atlantoaxial tuberculosis with neurological impairment, one-stage combined anterior and posterior surgical approach have the ability to complete debridement and decompression, and reconstruction of the stability of the upper cervical spine.

Clinical and radiological outcomes of image guided posterior C1-C2 fixation for atlantoaxial osteoarthritis (AAOA)

Background

Atlantoaxial (C1-C2) osteoarthritis (AAOA) causes severe suboccipital pain exacerbated by lateral rotation. The pain is usually progressive and resistant to conservative therapy. Posterior fusion surgery is performed to stabilise the C1-C2 segment. This is the first Australian study reporting the outcome of posterior atlantoaxial fixation including hybrid fixations performed for AAOA.

Methods

All patients who underwent posterior atlantoaxial fixation surgery for AAOA from 2005 to 2015 at our institutions were enrolled (N=23). Patient demographics and surgical technique were recorded. These techniques included transarticular screw (TAS) fixation using image guidance with iliac crest bone graft and supplemental posterior Sonntag wiring, or C1-C2 lateral mass fixation (Harms technique). Some patients required a combination of fixation due to anatomical variation. Primary outcome measures including patient satisfaction, pain, disability scores and range of motion were recorded for all patients pre- and post-operatively. Post-operative assessment was supplemented with CT and X-ray imaging.

Results

Twenty-three patients (19 women, 4 males, mean age 71.8±6.3 years) underwent surgical fixation. Eight underwent TAS fixation, 8 had Harms fixation, and 7 had a hybrid fixation. All patients reported statistically significant improvement in pain scores [Visual Analogue Scale (VAS) 9.4 pre-op compared to 2.9 post-op, P<0.005]. Disability scores [Neck Disability Index (NDI)] were statistically significantly reduced from 72.2±12.9 pre-operatively to 18.9±11.9 post-operatively, P<0.005. Mean follow-up was 55.3±36.1 months. Results did not vary according to the construct type. Ninety-five point five percent of patients showed radiographic evidence of fusion. Ninety-one percent of patients said they would undergo the surgery again.

Conclusions

Posterior atlantoaxial fixation with TAS and Harms constructs are highly effective for the surgical treatment of intractable neck pain secondary to atlantoaxial lateral mass osteoarthritis (AAOA). Surgery offers a high rate of symptom relief. If anatomical variability exists, both transarticular and pedicle screw fixation could be safely used in the same patient.

A 30-year-old Male with Delayed Diagnosis and Management of Chronic Post-traumatic Atlantoaxial Rotatory Subluxation

Introduction:

Atlantoaxial rotatory subluxation (AARS) is an uncommonly encountered diagnosis within the adult population. The rare nature of this dislocation within the adult population often results in delayed diagnosis and treatment.

Case Report:

A 30-year-old male presented following a low-speed motor vehicle accident. The patient had been involved in a work-related accident 1-year prior and had experienced fixed leftward gaze and tenderness of the cervical spine following this incident, but exhibited no focal neurologic deficits. Imaging demonstrated a Fielding Type 1 AARS of approximately 45°. The subluxation was reduced; and posterior C1–C2 instrumentation and fusion were performed, with no complications. Post-operative imaging revealed maintained reduction and alignment. The patient regained acceptable alignment and relief from his pre-operative symptoms.

Conclusions:

Our case is an illustration of a chronic post-traumatic AARS in an adult patient with delayed diagnosis and definitive management. This diagnosis is rare within the adult population and is frequently overlooked. A high index of suspicion must exist when evaluating adult patients with clinical presentations of chronic neck pain, torticollis, or “cock robin” head positioning as delayed diagnosis.

Insights into the Past and Future of Atlantoaxial Stabilization Techniques

Over the past century, atlantoaxial stabilization techniques have improved considerably. To our knowledge there has been a scarcity of articles published that focus specifically on the history of atlantoaxial stabilization. Examining the history of instrumentation allows us to evaluate the impact of early influences on current modern stabilization techniques. It also provides inspiration to further develop the techniques and prevents repetition of mistakes. This paper reviews the evolution of C1-C2 instrumentation techniques over time and provides insights into the future of these practices.We did an extensive literature search in PubMed, Embase and Google Scholar, using the following search terms: 'medical history', 'atlantoaxial', 'C1/C2', 'stabilization', 'instrumentation', 'fusion', 'arthrodesis', 'grafting', 'neuroimaging', 'biomechanical testing', 'anatomical considerations' and 'future'.Many different entry zones have been tested, as well as different constructs, from initial attempts with use of silk threads to use of hooks and rod-wire techniques, and handling of bone grafts, which eventually led to the development of the advanced screw-rod constructs that are currently in use. Much of this evolution is attributable to advancements in neuroimaging, a wide range of new materials available and an improvement in biomechanical understanding in relation to anatomical structures.

Incidence and risk factors for adjacent segment degeneration following occipitoaxial fusion for atlantoaxial instability in non-rheumatoid arthritis

PURPOSE

To investigate the incidence and risk factors for adjacent segment degeneration (ASD) following occipitoaxial fusion (OAF) for atlantoaxial instability (AAI) in non-rheumatoid arthritis (RA).

METHODS

The study group comprised 41 patients without RA who underwent OAF due to AAI. Fifteen patients with postoperative ASD after OAF were classified as the ASD group, and the other 26 patients without postoperative ASD were included in the non-ASD group. There were 12 men and 3 women with a mean age of 43.52 years in the ASD group, and 19 men and 7 women with a mean age of 45.31 years in the non-ASD group. The mean follow-up period was 6.1 and 5.9 years in the ASD group and non-ASD group, respectively. Clinical outcomes and plain radiographs were retrospectively reviewed and compared between the two groups.

RESULTS

The difference between pre- and postoperative O-C2 angles in the non-ASD group was significantly greater than that in the ASD group. The C2-7 angles changed significantly between the pre- and postoperative periods. It was suggested that the small O-C2 angle and large C2-7 angle observed in the early postoperative period were risk factors for the development of ASD. We also demonstrated a high incidence of subaxial subluxation (SAS) and swan neck deformity in the ASD group (27 versus 3.8% and 20 versus 0%, respectively).

CONCLUSION

Under-correction of the O-C2 angle is likely to cause malalignment of the cervical spine, resulting in the development of postoperative ASD, SAS, and swan neck deformity.

Biomechanical comparison of a novel C1 posterior U-construct with four other techniques in a C1-C2 fixation model

Background

Compare the biomechanical stability of a novel "U" posterior cervical fixation construct to four other posterior cervical atlantoaxial fixation constructs.

Methods

Eight fresh frozen human cadaver spines were tested after a simulated odontoid fracture, and following stabilization with each construct.

Results

All constructs significantly decreased flexion-extension and axial rotation compared to the destabilized spine. The U construct provided significantly more axial stability than the Brooks wire technique.

Conclusion

The novel U construct demonstrated comparable biomechanical stability to the existing constructs in all three planes of motion with the exception of axial rotation, in which it was inferior to TAS.

[Analysis of a three-dimensional finite element model of atlas and axis complex fracture]

Objective: To explored the clinical application of the three-dimensional finite element model of atlantoaxial complex fracture. Methods: A three-dimensional finite element model of cervical spine (FEM/intact) was established by software of Abaqus6.12.On the basis of this model, a three-dimensional finite element model of four types of atlantoaxial complex fracture was established: C(1) fracture (Jefferson)+ C(2) fracture (type Ⅱfracture), Jefferson+ C(2) fracture(type Ⅲfracture), Jefferson+ C(2) fracture(Hangman), Jefferson+ stable C(2) fracture (FEM/fracture). The range of motion under flexion, extension, lateral bending and axial rotation were measured and compared with the model of cervical spine. Results: The three-dimensional finite element model of four types of atlantoaxial complex fracture had the same similarity and profile.The range of motion (ROM) of different segments had different changes.Compared with those in the normal model, the ROM of C(0/1) and C(1/2) in C(1) combined Ⅱ odontoid fracture model in flexion/extension, lateral bending and rotation increased by 57.45%, 29.34%, 48.09% and 95.49%, 88.52%, 36.71%, respectively.The ROM of C(0/1) and C(1/2) in C(1) combined Ⅲodontoid fracture model in flexion/extension, lateral bending and rotation increased by 47.01%, 27.30%, 45.31% and 90.38%, 27.30%, 30.0%.The ROM of C(0/1) and C(1/2) in C(1) combined Hangman fracture model in flexion/extension, lateral bending and rotation increased by 32.68%, 79.34%, 77.62% and 60.53%, 81.20%, 21.48%, respectively.The ROM of C(0/1) and C(1/2) in C(1) combined axis fracture model in flexion/extension, lateral bending and rotation increased by 15.00%, 29.30%, 8.47% and 37.87%, 75.57%, 8.30%, respectively. Conclusions: The three-dimensional finite element model can be used to simulate the biomechanics of atlantoaxial complex fracture.The ROM of atlantoaxial complex fracture is larger than nomal model, which indicates that surgical treatment should be performed.

Long-Term Clinical and Radiologic Postoperative Outcomes After C1-C2 Pedicle Screw Techniques for Pediatric Atlantoaxial Rotatory Dislocation

BACKGROUND

Although C1-C2 pedicle screw techniques have been extensively reported in pediatric series, reports on their use have examined only small series with short follow-up periods. The aim of this study was to report pediatric patients with atlantoaxial rotatory dislocation treated with these techniques with a minimum 5-year follow-up.

METHODS

Retrospective review was performed of 27 pediatric patients with atlantoaxial rotatory dislocation who underwent C1-C2 pedicle screw fixation between 2004 and 2012. Clinical and radiographic outcomes were collected and compared with a control group.

RESULTS

Follow-up period was 60-142 months (mean 84 months). Torticollis was completely corrected postoperatively in all but 1 patient. All patients experienced significant pain relief and improvement in range of motion, and 6 patients with neurologic deficits experienced significant improvement postoperatively. Both atlantodental interval and space available for the cord were significantly improved compared with preoperative values. At final follow-up, curvature was lordotic in 20 cases and straight in 7 cases. Compared with the control group, range of motion of the patient group was not significantly different in any direction except in flexion and rotation. Mean anteroposterior diameters of the spinal canal at C1 and C2 levels were not significantly different from the control group.

CONCLUSIONS

C1-C2 pedicle screw techniques are safe and effective for treatment of atlantoaxial rotatory dislocation and result in no obvious limitation on growth in older children.

Traumatic Posterolateral C1-C2 Dislocation Complicated with Locked Lateral Mass and Type II Odontoid Fracture-5-Year Follow-up

OBJECTIVE

We sought to document our experience in managing a rare complex of traumatic posterolateral atlantoaxial dislocation combined with locked lateral mass and type II odontoid fracture.

METHOD

A 30-year-old male patient was referred to the author's department. He complained of a decrease in neck range of motion following a traffic accident. Neurologic examination was normal. Computed tomography and open-mouth radiographs showed a type II odontoid fracture and a posterolateral dislocation with a laterally locked left lateral mass at the C1-C2 level. Considering the difficulty and risk in reduction, due to this rare instability and dislocation, a 2-staged treatment was performed. With up to 11 kg skull traction for 7 days before surgery, the locked lateral mass and the lateral dislocation was finally reduced without any neurologic deficit. And once closed reduction was confirmed by open-mouth and lateral X-ray views in the cervical spine, a second staged C1-C2 surgical fixation and fusion with iliac bone graft was performed to achieve a normal anatomic alignment with a better stability.

RESULT

The patient showed significant amelioration of neck symptoms postoperatively, and a successful reduction and fixation of the C1-C2 articulation was achieved. At the 5-year follow-up, solid bone fusion was evident on the computed tomography scan.

CONCLUSION

For traumatic posterolateral atlantoaxial dislocation complicated with type II odontoid fracture, a closed reduction of the lateral dislocation before operation is both useful and safe because surgeons do not need to reduce the extremely rare lateral dislocation during the operation. Posterior atlantoaxial stabilization and fusion, rather than the occipitocervical fusion as reported previously, is biomechanically stable enough to achieve solid fusion in this rare trauma while not sacrificing the occipitoatlantal joint.

Biomechanical evaluation of C1 lateral mass and C2 translaminar bicortical screws in atlantoaxial fixation: an in vitro human cadaveric study

BACKGROUND CONTEXT

Atlantoaxial fixation with C1 lateral mass-C2 translaminar bicortical (C1LM-C2TB) screws has been reported to afford good stability with the least risk of injury to vertebral artery. However, no comparative in vitro studies have been conducted to evaluate the biomechanical stability of this method.

PURPOSE

This study aimed to compare in vitro biomechanics of fixation with C1LM-C2TB with fixation with C1 lateral mass-C2 translaminar unicortical screws (C1LM-C2TU) and with C1 lateral mass-C2 pedicle screws (C1LM-C2PS).

STUDY DESIGN

This is an in vitro biomechanical study.

METHODS

Fifteen fresh-frozen human cadaveric cervical spines (C1-C3) were tested after destabilization by transverse-alar-apical ligament disruption. Instrumentation was performed with three fixation constructs: C1LM-C2PS, C1LM-C2TU, and C1LM-C2TB. Flexion, extension, lateral bending, and axial rotation were tested. Range of motion and neutral zone pre-fatigue and post-fatigue values were measured.

RESULTS

No significant differences were observed in flexion-extension among the three groups. However, C1LM-C2TB fixation was superior to C1LM-C2TU fixation in lateral bending and axial rotation.

CONCLUSION

C2 translaminar bicortical screws are biomechanically superior to C2TU screws for fixation of the atlantoaxial complex, and it is equivalent to C2PS fixation. C2 translaminar bicortical screws or C2PS should be preferred over C2TU screws.

An infantile alantoaxial dislocation with patent foramen ovale managed with titanium cabling and allogenic bone grafts

Atlantoaxial dislocation is a disorder that is characterized with loss of stability of the atlas and axis (C1-C2) with consequential loss of usual articulation. Although this condition is very common, no one has reported a case as young as our patients. We present a 7-month infant with bilateral paralysis of the lower limbs for four (4) months with no history of trauma. Computer tomographic (CT-scan) imaging revealed alantoaxial dislocation with severe cervical spinal cord compression. The odontoid process is displaced outwardly with no bone destruction. Doppler echocardiogram done revealed patent foramen ovale. Thorough physical examination as well as radiological evaluation revealed no feather malformations. Electrophysio - logical studies reveal normal compound muscle action potentials (CMAP) and sensory nerve action potentials (SNAPs) in all the limbs. Electromyography (EMG) also revealed normal nerves in the limbs and the trunk. We attained a stable fusion and anatomical reduction using a posterior titanium wire and an iliac bone graft harvested from his mother. This is the youngest patient reported in literature. Infantile alantoaxial dislocation should be managed at early stage to prevent long-term neurologic disorders.

Management of acute combined fractures of the atlas and axis: A retrospective study of two trauma centers

Background:

Management of combination fractures of the atlas and axis varies from nonoperative immobilization to selective early surgical intervention. In this study, we present our experience in managing these injuries.

Materials and Methods:

Electronic databases from two level 1 trauma centers were queried to identify all patients diagnosed with C1-C2 combination fractures from 2009 to present. Patient demographics, fracture characteristics, treatment modality, complications, Frankel scores, and fusion status were collected. Patients were separated into operative and nonoperative cohorts, and comparisons were made between the two groups.

Results:

Forty-eight patients were included, of which 19 received operative management and 29 were treated nonoperatively. The mean age was 76.1 and 75.3 years, respectively (P = 0.877). Frankel grade distribution was similar on presentation in both groups, with most being neurologically intact. C1 fractures of both the anterior and posterior arch were present in 41.2% patients undergoing fusions compared to 27.6% of patients treated nonoperatively. No significant differences in comorbidities, neurologic deficits, or radiographic measurements were observed across the two groups.

Conclusions:

This study demonstrates the variety of treatment strategies used for the management of combined C1-C2 fractures. Patients managed operatively tend to have both anterior and posterior C1 arch fractures, while patients managed nonoperatively tend to have either anterior or posterior arch fractures. In general, treatments should be tailored to patients’ needs depending on the stability of the fractures, neurological state, and medical comorbidities.

External fixation and surgical fusion for pediatric cervical spine injuries: Short-term outcomes

OBJECTIVE

To compare in-hospital complication rates in pediatric patients with atlantoaxial and subaxial injuries undergoing either external fixation or surgical fusion.

PATIENTS AND METHODS

Baseline and outcome data were obtained from the 2002-2011 Nationwide Inpatient Sample (NIS) for patients under the age of 18 with a diagnosis of cervical spine fracture without spinal cord injury or cervical spine subluxation. Patients who underwent external immobilization or internal fixation were included for analysis. Variables analyzed included length of stay, in-hospital mortality, discharge disposition, total hospital charges, and development of at least one in-hospital complication.

RESULTS

A total of 2878 pediatric patients with cervical spine injury were identified; 1462 patients (50.8%) with atlantoaxial (C1-2) injury and 1416 (49.2%) with subaxial (C3-7) injury. Among atlantoaxial injury patients, external fixation was associated with lower total charges ($73,786 vs. $98,158, p = .040) and a lower likelihood of developing at least one complication (1.9% vs. 6.8%, p = .029) compared to surgical fusion, and was a more common treatment for subluxation alone (16.4% vs. 2.6%, p < .001). Among subaxial injury patients, there were no significant differences in age (p = .262), length of stay (p = .196), occurrence of at least one complication (p = .334), or total charges (p = .142). Subaxial subluxation injuries alone were treated more often with surgical fusion (2.2% vs. 1.2%, p < .001).

CONCLUSION

Optimal treatment of patients with cervical injury may vary by location of injury. Our findings warrant further investigation into the difference in clinical outcomes between surgical and non-surgical management of atlantoaxial and subaxial injury.

Posterior atlantoaxial fusion using a C2 transverse foramen-penetrating screw: A technical note

Background:

Although recent development of screw instrumentation techniques for rigid fixation of the atlantoaxial joint has increased surgical options, patients in whom screws of any type cannot be safely placed are sometimes encountered. We present a unique surgical technique for C1-2 transarticular screw placement utilizing a novel trajectory.

Methods:

A 35-year-old male with a history of Down's syndrome and cognitive dysfunction with hyperkinesis spontaneously developed rapid onset of tetraparesis and gait disturbance. Radiographs of the cervical spine revealed atlantoaxial subluxation (AAS) that could not be reduced. Computed tomography (CT) of the head showed multiple subacute cerebral infarctions in the territory of the right vertebral artery (VA). Three-dimensional CT angiography of the craniovertebral junction additionally confirmed right VA occlusion at the C2/3 level, a left C2 origin of the posterior inferior cerebellar artery, and hypoplasia of the bilateral C2 pedicles/C2 lamina. Because traditional screw-placement was not feasible, we performed a unique atlantoaxial fusion utilizing a C2 transverse foramen-penetrating screw with iliac bone grafting performed under neuronavigation.

Results:

The postoperative course was uneventful, and the patient regained the ability to ambulate, returning to his previous level of function. The CT of the cervical spine 12 months postoperatively showed rigid bony C1-C2 fusion, without recurrence of stroke.

Conclusion:

We introduced a novel C1-C2 transarticular screw-placement technique in which the trajectory went through the ipsilateral VA foramen due to already extent VA occlusion.

Atlantoaxial Langerhans cell histiocytosis radiographic characteristics and corresponding prognosis analysis

BACKGROUND

Langerhans cell histiocytosis (LCH) may affect atlas and axis, and there were very few published cases describing a characteristic of LCH of atlantoaxial.

OBJECTIVE

The objective of the study is to investigate the image manifestations of atlantoaxial LCH to improve the in-depth comprehension on it.

MATERIALS AND METHODS

A retrospective study was done of computed tomography (CT) and magnetic resonance imaging in atlas and axis and prognosis was analyzed.

RESULTS

The study included 41 patients (average age 12.9 years and median age 8 years) diagnosed with LCH, with 75.6% under 15 years old. Eighty-four lesions of LCH were identified including 47 in the atlas and 37 in the axis. The osteolytic bone destructions in the atlas and axis were characterized, 22% accompanied by sclerotic margins. Thirteen patients had a compression fracture, 11 in the lateral mass of the atlas and 2 in the C2 vertebral body. Sixteen and three patients had atlantoaxial malalignment and dislocation, respectively. On T2-weighted images, 68.9% showed iso- or low-signal intensity, 27.6% showed hyperintensity signal, and 3.4% showed heterogeneous signal. On postcontrast images, 81.9% showed significant enhancement, 12.5% showed moderate enhancement, and 6.3% showed mild enhancement. CT reexamination of 14 patients indicated atlantoaxial bone destruction relatively repaired in 12 patients. Thirty-three patients were a follow-up, 81.8% had no significant symptoms and 18.2% with remaining symptoms.

CONCLUSIONS

The atlas and axis were affected by LCH, mainly in children. The lateral mass was easily affected and compressed, destruction of the atlas and axis could lead to atlantoaxial joint instability. The prognosis was good in most of the patients.

Percutaneous anterior C1/2 transarticular screw fixation: salvage of failed percutaneous odontoid screw fixation for odontoid fracture

BACKGROUND

The objective of this study is to investigate the outcomes and safety of using percutaneous anterior C1/2 transarticular screw fixation as a salvage technique for odontoid fracture if percutaneous odontoid screw fixation fails.

METHODS

Fifteen in 108 odontoid fracture patients (planned to be treated by percutaneous anterior odontoid screw fixation) were failed to introduce satisfactory odontoid screw trajectory. To salvage this problem, we chose the percutaneous anterior C1/2 transarticular screw fixation technique in treatment of these patients. The visual analogue score (VAS) of neck pain and Neck Disability Index (NDI) of all patients were scored at pre-operation, 3 months after operation, and final follow-up. Additional, technique-related complications were recorded and collected.

RESULTS

Percutaneous C1/2 transarticular screw fixation was performed successfully in all 15 patients whose odontoid screw fixation failed. No technique-related complications (such as nerve injury, spinal cord injury, and esophageal injury) occurred. The VAS of neck pain and NDI score improved significantly (P = 0.000) after operation, and no significant differences were found when compared to 93 non-salvage patients who successfully performed the percutaneous anterior odontoid screw fixation. No screw loose or breakage occurred, all of the odontoid fractures achieve radiographic fusion, bony fusion bridge could be observed at the C1/2 lateral articular facet on 9/15 patients.

CONCLUSIONS

We suggest that percutaneous anterior C1/2 transarticular screw fixation is a good alternative salvage technique if percutaneous odontoid screw fixation failed, and it is a minimally invasive, feasible, and safe technique.

Gallie technique versus atlantoaxial screw-rod constructs in the treatment of atlantoaxial sagittal instability: a retrospective study of 49 patients

Background

The objectives of this study are to investigate the clinical curative effect of Gallie technique and atlantoaxial screw-rod constructs (SRC) on atlantoaxial sagittal instability and determine the indication of Gallie technique.

Methods

Data of 49 patients with atlantoaxial sagittal instability from February 2008 to May 2015 were analyzed retrospectively. The visual analog scale (VAS) score and the neck disability index (NDI) were used to evaluate the curative effect. Postoperative radiological outcomes were used to evaluate the stability of atlantoaxial joint and bone fusion. Perioperative parameters such as blood loss, operation time, radiographic exposure times, and hospital expense were also recorded and analyzed.

Results

Forty-nine patients (36 men and 13 women) were included in this study. The mean age was 41.4 ± 8.9 (range from 19 to 64). All patients were followed up for 24–67 months. Among these patients, 25 of these patients underwent Gallie surgery and 24 underwent SRC surgery. The pain in the occipitocervical area of all the patients has been relieved. NDI scores and VAS scores were lower in Gallie group than in SRC group in early postoperative period. The proportion of the patients who achieved good bone fusion within 3 months after operation was 88.0% (22/25) in the Gallie group and 100% (24/24) in the SRC group. The Gallie group is lower than the SRC group in blood loss, operation time, radiographic exposure times, and hospital expense. Statistical difference was observed between the two groups.

Conclusions

For patients with atlantoaxial instability who has (1) the atlantodental interval (ADI) which is bigger than 5 mm on lateral flexion-extension X-ray, or Anderson-D’Alonzo type II odontoid fracture, (2) no asymmetry between odontoid process and lateral mass on open-mouth anterior-posterior X-ray, and (3) no dislocation of lateral mass joint on the CT 3D reconstruction, Gallie technique can be chosen as a safe and effective method if atlantoaxial reduction can be achieved preoperatively. Compared with SRC, Gallie technique can relieve the pain in the occipitocervical area earlier and it can shorten operation time and reduce intraoperative bleeding, radiographic exposure times, and hospital expense effectively. However, for patients with irreducible atlantoaxial dislocation, the Gallie technique should be used with caution.

The provocative radiographic traction test for diagnosing craniocervical dissociation: a cadaveric biomechanical study and reappraisal of the pathogenesis of instability

BACKGROUND CONTEXT

Craniocervical dissociation is a rare but serious condition, and missed injuries have been associated with poor neurologic outcomes and deterioration. A fluoroscopic traction test is employed to interrogate the craniocervical ligaments when clinical and imaging findings are equivocal. However, no specific protocol or known parameters with respect to traction or force applied have been established.

PURPOSE

This study sought to define the parameters of the radiographic traction test with sequential sectioning of the primary ligamentous restraints under controlled distraction of the craniocervical junction in a biomechanical model.

STUDY DESIGN

This is a cadaveric biomechanical study.

METHODS

A custom loading apparatus applied traction forces in six specimens (O-C3) and the following ligaments were sectioned: alar, tectorial membrane, and occiput-C1 capsules to simulate varying degrees of craniocervical dissociation. Traction was applied 0 to 20 lb with fluoroscopy. Digital image analysis quantified the relative displacements of C0-C1, average craniocervical excursion, and under what load could a 2-mm craniocervical displacement be reproducibly recorded.

RESULTS

A weight-distance table was produced and showed a marked loss of stability with sectioning of the ligaments and across all specimens in a similar pattern. Minimal translation was noted with sectioning of two of three ligaments in any order (<1-2 mm). All specimens exhibited a firm restraint to dissociation until the last of the three stabilizers was sectioned. Thus an "all-or-none" restraint to instability is present. All specimens failed at a weight of 5-10 lb (>2 mm).

CONCLUSIONS

The current knowledge base of craniocervical injuries is very limited. This study shows that the key restraints to craniocervical instability are the alar ligaments, tectorial membrane, and the atlantooccipital joint capsules. Dissociation requires the complete incompetence of all three. The craniocervical traction test reliably demonstrates instability and requires no more than 5-10 lb of traction to perform.

A case of fourth atlanto-axial facet joint: anatomical description

PURPOSE

To report a rare fourth atlanto-axial joint.

METHODS

A cadaveric specimen of a young male adult from occiput to C4 was dissected for anatomical study of craniocervical region. A true fourth atlanto-axial joint was confirmed. Its morphological characteristics were described.

RESULTS

The fourth atlantoaxial joint is rarely seen. The possible embryogenesis is discussed. This case raises an anatomical possibility of a new variant in this region.

CONCLUSIONS

A unique case with an anatomically proven fourth atlantoaxial joint is reported. This anomaly can lead to misdiagnosis. CT scan coupled with MRI can facilitate accurate diagnosis.

Recurrent dislocations of the atlantooccipital and atlantoaxial joints in a halo vest fixator are resolved by backrest elevation in an elevation angle-dependent manner

BACKGROUND CONTEXT

Halo fixation is now universally performed in the initial reduction and fixation of unstable upper cervical spine injuries; however, persistent high instability and recurrent dislocations of the atlantooccipital and atlantoaxial joints after fixation are not well recognized.

PURPOSE

The aim was to describe persistent instability of traumatic dislocations of the atlantooccipital and atlantoaxial joints after halo fixation and a useful method for preventing instability.

STUDY DESIGN

This was a case report of a patient who survived traumatic dislocations of the atlantooccipital and atlantoaxial joints.

PATIENT SAMPLE

A 73-year-old woman diagnosed with dislocations of the atlantooccipital and atlantoaxial joints along with multiple other injuries sustained in a traffic accident was included.

METHODS

After initial closed reduction and halo fixation, congruity of the atlantooccipital and atlantoaxial joints was evaluated using, condylar gap, atlantodental interval, and flexion angulation of C1-C2 after the initial examination and before surgery.

RESULTS

Changes in parameters 12 hours after halo fixation revealed re-dislocations and instability of the joints. Backrest elevation with halo fixation tended to reduce re-dislocations. Therefore, we carefully increased the backrest angle and measured the parameters at several angles of elevation within a range that did not affect vital signs to observe the effectiveness of elevation against re-dislocations. Elevation changed the parameters in an elevation angle-dependent manner, and these changes suggested that elevation was effective for reducing re-dislocation of both the atlantooccipital and atlantoaxial joints during halo fixation. With no major complications, this method enabled us to maintain good congruity of the joints for approximately 2 weeks until posterior spinal fusion with internal fixation.

CONCLUSIONS

Backrest elevation with halo fixation appears safe to be performed without any other devices and is beneficial for blocking re-dislocation of both the atlantooccipital and atlantoaxial joints as well as possible secondary damage to the upper cervical spinal cord during the external fixation period.

Unilateral C1 Lateral Mass and C2 Pedicle Screw Fixation for Atlantoaxial Instability in Rheumatoid Arthritis Patients: Comparison with the Bilateral Method

OBJECTIVE

Bilateral C1 lateral mass and C2 pedicle screw fixation (C1LM-C2P) is an ideal technique for correcting atlantoaxial instability (AAI). However, the inevitable situation of vertebral artery injury or unfavorable bone structure may necessitate the use of unilateral C1LM-C2P. This study compares the fusion rates of the C1 lateral mass and C2 pedicle screw in the unilateral and bilateral methods.

METHODS

Over five years, C1LM-C2P was performed in 25 patients with AAI in our institute. Preoperative studies including cervical X-ray, three-dimensional computed tomography (CT), CT angiogram, and magnetic resonance imaging were performed. To evaluate bony fusion, measurements of the atlanto-dental interval (ADI) and CT scans were performed in the preoperative period, immediate postoperative period, and postoperatively at 1, 3, 6, and 12 months.

RESULTS

Unilateral C1LM-C2P was performed in 11 patients (44%). The need to perform unilateral C1LM-C2P was due to anomalous course of the vertebral artery in eight patients (73%) and severe degenerative arthritis in three patients (27%). The mean ADI in the bilateral group was 2.09 mm in the immediate postoperative period and 1.75 mm in 12-months postoperatively. The mean ADI in the unilateral group was 1.82 mm in the immediate postoperative period and 1.91 mm in 12-months postoperatively. Comparison of ADI measurements showed no significant differences in either group (p=0.893), and the fusion rate was 100% in both groups.

CONCLUSION

Although bilateral C1LM-C2P is effective for AAI from a biomechanical perspective, unilateral screw fixation is a useful alternative in patients with anatomical variations.

Regression of an atlantoaxial rheumatoid pannus following posterior instrumented fusion

OBJECTIVE

Rheumatoid patients may develop a retrodental lesion (atlantoaxial rheumatoid pannus) that may cause cervical instability and/or neurological compromise. The objective is to characterize clinical and radiographic outcomes after posterior instrumented fusion for atlantoaxial rheumatoid pannus.

METHODS

We retrospectively reviewed all patients who underwent posterior fusions for an atlantoaxial rheumatoid pannus at a single institution. Both preoperative and postoperative imaging was available for all patients. Anterior or circumferential operations, non-atlantoaxial panni, or prior C1-C2 operations were excluded. Primary outcome measures included Nurick score, Ranawat score (neurologic status in patients with rheumatoid arthritis), pannus regression, and reoperation. Pannus volume was determined with axial and sagittal views on both preoperative and postoperative radiological images.

RESULTS

Thirty patients surgically managed for an atlantoaxial rheumatoid pannus were followed for a mean of 24.43 months. Nine patients underwent posterior instrumented fusion alone, while 21 patients underwent posterior decompression and instrumented fusion. Following a posterior instrumented fusion in all 30 patients, the pannus statistically significantly regressed by 44.44%, from a mean volume of 1.26cm(3) to 0.70cm(3) (p<0.001), over 8.02 months. The Nurick score significantly improved from 2.40 to 0.60 (p<0.001), but the marginal improvement of 0.20 in the Ranawat score did not reach significance (p=0.312). Six patients (20%) required reoperations over a mean of 13.18 months. Reoperations were indicated for C1 instrumentation failure in four patients and pseudoarthrosis in two patients.

CONCLUSION

Following posterior instrumented fusion, the pannus radiographically regressed by 44.44% over a mean of 8.02 months, and patients clinically improved per the Nurick score. The Ranawat score did not improve, and 20% of patients required reoperation over a mean of 13.18 months. The annualized reoperation rate was approximately 13.62%.