Open reduction of irreducible atlantoaxial dislocation by transoral anterior atlantoaxial release and posterior internal fixation

Craniocervical instability in the setting of os odontoideum: assessment of cause, presentation, and surgical outcomes in a series of 279 cases

BACKGROUND

Our clinical understanding of os odontoideum (OO) remains incomplete. Congenital and traumatic causes have been proposed and advocated. Clinical presentations range from asymptomatic to axial pain to myelopathy or vertebral-basilar ischemia. A consensus for surgical management exists for those found to have an unstable atlantoaxial complex or symptomatic cranial-vertebral junction compression.

OBJECTIVE

To evaluate the clinical presentation and surgical outcomes of patients with OO and an unstable atlantoaxial complex or symptomatic cranial-vertebral junction compression.

METHODS

Patients with a diagnosis of OO who underwent surgical management were included. Patients were excluded on the basis of previous C2 fracture, Fielding diagnostic criteria, and inadequate follow-up. History of trauma and presenting symptoms were assessed. Clinical and neurological improvements were measured with the use of patient satisfaction scores and the Japanese Orthopaedic Association scores. Fusion status was documented with the use of radiographs and computed tomographic imaging.

RESULTS

Of 279 patients, 112 reported a history of cranial-vertebral junction trauma, whereas 28 were diagnosed with congenital malformations. Clinically, 84.9% of patients presented with myelopathy, with pain presented in 42.6%. Atlantoaxial fixation was performed in 240 patients, occiput-to-C2 fixation in 35 patients, and extended occipito-cervical fixation in 4 patients. Mean follow-up was 40.3 months. Complications were reported in 2.4% of patients. Japanese Orthopaedic Association scores improved from a preoperative mean of 12.4 to 14.8. Two hundred thirty-five patients (77.7%) improved, with 30 patients experiencing no change in symptoms and 14 patients deteriorating. Fusion was achieved in 96.8% of patients.

CONCLUSION

Our data reveal that surgical treatment for OO using the indications and techniques delineated is associated with high satisfaction rates, improved functional scores, and high fusion rates with low complication rates.

Posterior Reduction of Fixed Atlantoaxial Dislocation and Basilar Invagination by Atlantoaxial Facet Joint Release and Fixation: A Modified Technique With 174 Cases

BACKGROUND:

Treatment of fixed atlantoaxial dislocation (AAD) with basilar invagination (BI) is challenging.

OBJECTIVE:

To introduce a modified technique to reduce fixed AAD and BI through a posterior approach.

METHODS:

From 2007 to 2013, 174 patients with fixed AAD and BI underwent surgical reduction by posterior atlantoaxial facet joint release and fixation technique.

RESULTS:

There was 1 death in the series, and 3 patients were lost to follow-up. The follow-up period ranged from 12 to 52 months (mean: 35.2 months) for the remaining 170 patients. Neurological improvement was observed in 168 of 170 patients (98.8%), and was stable in 1 (0.06%) and exacerbated in 1 (0.06%), with the Japanese Orthopedic Association scores increasing from 11.4 preoperatively to 15.8 postoperatively (P < .01). Radiologically, complete or >90% reduction was attained in 107 patients (62.9%), 60% to 90% reduction was attained in 51 patients (30%), and <50% reduction was attained in 12 patients (7.1%), who underwent additional transoral decompression. Complete decompression was demonstrated in all 170 patients. Solid bony fusion was demonstrated in 167 patients at follow-up (98.2%).

CONCLUSION:

This series showed the safety and efficacy of the posterior C1-2 facet joint release and reduction technique for the treatment of AAD and BI. Most fixed AAD and BI cases are reducible via this method. In most cases, this method avoids transoral odontoidectomy and cervical traction. Compared with the occiput-C2 screw method, this short-segment C1-2 technique exerts less antireduction shearing force, guarantees longer bone purchase, and provides more immediate stabilization.

Biomechanical comparison of a novel transoral atlantoaxial anchored cage with established fixation technique - a finite element analysis

BACKGROUND

The transoral atlantoaxial reduction plate (TARP) fixation has been introduced to achieve reduction, decompression, fixation and fusion of C1-C2 through a transoral-only approach. However, it may also be associated with potential disadvantages, including dysphagia and load shielding of the bone graft. To prevent potential disadvantages related to TARP fixation, a novel transoral atlantoaxial fusion cage with integrated plate (Cage + Plate) device for stabilization of the C1-C2 segment is designed. The aims of the present study were to compare the biomechanical differences between Cage + Plate device and Cage + TARP device for the treatment of basilar invagination (BI) with irreducible atlantoaxial dislocation (IAAD).

METHODS

A detailed, nonlinear finite element model (FEM) of the intact upper cervical spine had been developed and validated. Then a FEM of an unstable BI model treated with Cage + Plate fixation, was compared to that with Cage + TARP fixation. All models were subjected to vertical load with pure moments in flexion, extension, lateral bending and axial rotation. Range of motion (ROM) of C1-C2 segment and maximum von Mises Stress of the C2 endplate and bone graft were quantified for the two devices.

RESULTS

Both devices significantly reduced ROM compared with the intact state. In comparison with the Cage + Plate model, the Cage + TARP model reduced the ROM by 82.5 %, 46.2 %, 10.0 % and 74.3 % in flexion, extension, lateral bending, and axial rotation. The Cage + Plate model showed a higher increase stresses on C2 endplate and bone graft than the Cage + TARP model in all motions.

CONCLUSIONS

Our results indicate that the novel Cage + Plate device may provide lower biomechanical stability than the Cage + TARP device in flexion, extension, and axial rotation, however, it may reduce stress shielding of the bone graft for successful fusion and minimize the risk of postoperative dysphagia. Clinical trials are now required to validate the reproducibility and advantages of our findings using this anchored cage for the treatment of BI with IAAD.

Post-Traumatic Torticollis Due to Odontoid Fracture in a Patient With Diffuse Idiopathic Skeletal Hyperostosis: A Case Report

Descriptive case report.To report a rare case of post-traumatic torticollis by odontoid fracture in a patient with diffuse idiopathic skeletal hyperostosis (DISH).Cervical fractures in DISH can result from minor trauma, and a delay in presentation often prevents their timely diagnosis. Cervical fractures in patients with spinal DISH usually occur in extension injuries, and almost always occur in the lower cervical spine. Reports of odontoid fractures with torticollis in patients with spinal DISH are rare.A 73-year-old man with DISH presented with severe neck pain and a cervical deformity presenting as torticollis without neurological deficits. He gave a history of a fall while riding a bicycle at a low speed 3 months ago. X-ray showed torticollis in the right side, and computed tomography (CT) showed a type-II odontoid fracture and subluxation at the C1-2 level.We performed a staged treatment because this patient had severe neck pain associated with a chronic course. Initially, the fracture dislocation was reduced under general anesthesia and was stabilized with a halo vest. We then performed posterior occipitocervical in situ fusion after confirming the correction of the cervical deformity by CT. The patient showed significant amelioration of neck symptoms postoperatively, and bony fusion was achieved 1 year after surgery.For post-traumatic torticollis due to an odontoid fracture, plain CT is useful for diagnosis and posterior occipitocervical in situ fusion following correction and immobilization with a halo vest is a safe and an effective treatment.

Spontaneous Ankylosis of Occiput to C2 following Closed Traction and Halo Treatment of Atlantoaxial Rotary Fixation

Study Design Case report. Objective We report a case of spontaneous atlantoaxial rotatory fixation (AARF) presenting 9 months after onset in an 11-year-old boy. Methods This is a retrospective case report of spontaneous ankylosis of occiput to C2 following traction, manipulative reduction, and halo immobilization for refractory atlantoaxial rotatory fixation. Results The patient underwent traction followed by close manual reduction and placement of halo immobilization after 6 months of severe spontaneous-onset AARF that had been refractory to chiropractic manipulation and physical therapy. Imaging demonstrated dislocation of the left C1-C2 facet joint and remodeling changes of the C2 superior facet prior to reduction, followed by near complete reduction of the dislocation after manipulation and halo placement. Symptoms and clinical appearance were satisfactorily improved and the halo vest was removed after 3 months. At late follow-up, computed tomography demonstrated complete bony ankylosis of the occiput to C2. The patient was found to be HLA B27-positive, but he had no family history of ankylosing spondyloarthropathy or other joint symptoms. The underlying reasons for spontaneous fusion of the occiput to C2 could include the traction, HLA-B27-related spondyloarthropathy, or arthropathic changes caused by traction, reduction, the inciting insult, or immobilization. Conclusion When discussing treatment of childhood refractory AARF by traction, closed manipulation, and halo immobilization, the possibility of developing "spontaneous" ankylosis needs to be considered.

Anterior transoral atlantoaxial release and posterior instrumented fusion for irreducible congenital basilar invagination

PURPOSE

Recently, it has been demonstrated that anterior release of tight structures via a transoral approach can assist posterior distraction-reduction technique in restoring the cranio-cervical anatomy in irreducible atlantoaxial dislocations. Our aim was to evaluate the radiological and clinical outcome of anterior release and posterior instrumentation for irreducible congenital basilar invagination.

METHODS

A consecutive series of 15 patients (2007-2009) with irreducible congenital basilar invagination were treated with anterior release using transoral approach. A retrospective chart review was performed. All patients presented with myelopathy. Dislocation was treated as irreducible if acceptable reduction was not achieved with traction under general anesthesia and neuromuscular paralysis. The anterior release comprised of transverse sectioning the longus colli and capitis, C1-C2 joint capsular release and intra-articular adhesiolysis with or without anterior C1 arch excision. Cantilever mechanism using posterior instrumentation was used to correct any residual malalignment.

RESULTS

Mean age was 21.4 (10-50) years. Average duration of follow-up was 28 (24-40) months. The average preoperative JOA score was 11.4 (8-16), which improved to 15.4 (10-18) after surgery. Anatomical reduction was achieved in thirteen patients. Fusion was documented in all patients. Complications included persistent nasal phonation in one, and superficial wound dehiscence in one.

CONCLUSION

We believe that a significant number of irreducible dislocations can be anatomically reduced with this procedure thus avoiding odontoid excision. Encouraging results from this short series have given us a new perspective in dealing with these challenging problems.

Spinal involvement in mucopolysaccharidoses: a review

BACKGROUND

Mucopolysaccharidoses (MPS) represent a group of inheritable lysosomal storage diseases caused by mutations in the genes coding for enzymes involved in catabolism of different glycosaminoglycans (GAGs). They are clinically heterogeneous multisystemic diseases, often involving the spine. Bony abnormalities of the spine included in the so-called dysostosis multiplex and GAG deposits in the dura mater and supporting ligaments can result in spinal cord compression, which can lead to compressive myelopathy. Spinal involvement is a major cause of morbidity and mortality in some MPS (e.g., MPS IVA, VI, and I), and early radiological diagnosis is critical in preventing or arresting neurological deterioration and loss of function.

DISCUSSION

Management of MPS, however, requires a multidisciplinary approach because of the multiorgan nature of the disease. Indeed in order to appreciate the relevance and nuances of each other's specialty, radiologists and clinicians need to have a background of common knowledge, rather than a merely compartmentalized point of view. In the interest of the management of spinal involvement in MPS, this review article aims on one hand to provide radiologists with important clinical knowledge and on the other hand to equip clinicians with relevant radiological semiotics.

C1 lateral mass screw placement in occipitalization with atlantoaxial dislocation and basilar invagination: a report of 146 cases

STUDY DESIGN

Retrospective study of 146 patients with the diagnosis of occipitalization, atlantoaxial dislocation (AAD) and basilar invagination, using a novel surgical treatment strategy.

OBJECTIVE

To introduce a novel fixation and reduction technique.

SUMMARY OF BACKGROUND DATA

Atlas occipitalization associated with basilar invagination often result in fixed AAD that need reduction and occipitocervical fixation. The widely used occipitocervical fixation with suboccipital screws has several limitations such as the poor screw purchase in maldevelopment of the occipital bone, limited area available for implants in previous suboccipital craniectomy. The placement of occipitalized C1 lateral mass screw is an alternative option.

METHODS

From June 2007 to June 2013, 146 patients of occipitalized atlas with fixed AAD and basilar invagination, underwent fixation and reduction via C1 lateral mass and C2 pars/pedicle screw.

RESULTS

A total of 143 patients achieved the follow-up in the range from 6 months to 4 years (average, 30 mo). Neurological improvement was seen in all the 143 patients, with the averaged Japanese Orthopedic Association scores increasing from 11.6 to 15.5. Radiographical evaluation showed that solid bony fusion was achieved in all patients, and complete reduction was attained in 95 patients, and partial reduction (>60%) in 40 patients, and no effective reduction in 8 patients who had additional transoral decompression. Magnetic resonance imaging demonstrated that the ventral cervicomedullary compression was relieved in all patients.

CONCLUSION

Although technically demanding, the C1 lateral mass placement in occipitalization is very useful in the rescue situation where more conventional stabilization alternatives are not technically possible, or as routine occipitocervical stabilization. It provides firm stabilization offering an optimum situation for bony fusion, and meanwhile the effective reduction of fixed AAD and basilar invagination. An extremely high fusion rate can be expected with minimal complications and minimal postoperative immobilization with this technique.

The development and evaluation of individualized templates to assist transoral C2 articular mass or transpedicular screw placement in TARP-IV procedures: adult cadaver specimen study

OBJECTIVES

The transoral atlantoaxial reduction plate system treats irreducible atlantoaxial dislocation from transoral atlantoaxial reduction plate-I to transoral atlantoaxial reduction plate-III. However, this system has demonstrated problems associated with screw loosening, atlantoaxial fixation and concealed or manifest neurovascular injuries. This study sought to design a set of individualized templates to improve the accuracy of anterior C2 screw placement in the transoral atlantoaxial reduction plate-IV procedure.

METHODS

A set of individualized templates was designed according to thin-slice computed tomography data obtained from 10 human cadavers. The templates contained cubic modules and drill guides to facilitate transoral atlantoaxial reduction plate positioning and anterior C2 screw placement. We performed 2 stages of cadaveric experiments with 2 cadavers in stage one and 8 in stage two. Finally, guided C2 screw placement was evaluated by reading postoperative computed tomography images and comparing the planned and inserted screw trajectories.

RESULTS

There were two cortical breaching screws in stage one and three in stage two, but only the cortical breaching screws in stage one were ranked critical. In stage two, the planned entry points and the transverse angles of the anterior C2 screws could be simulated, whereas the declination angles could not be simulated due to intraoperative blockage of the drill bit and screwdriver by the upper teeth.

CONCLUSIONS

It was feasible to use individualized templates to guide transoral C2 screw placement. Thus, these drill templates combined with transoral atlantoaxial reduction plate-IV, may improve the accuracy of transoral C2 screw placement and reduce related neurovascular complications.

A review of the diagnosis and treatment of atlantoaxial dislocations

Study Design Literature review. Objective Atlantoaxial dislocation (AAD) is a rare and potentially fatal disturbance to the normal occipital-cervical anatomy that affects some populations disproportionately, which may cause permanent neurologic deficits or sagittal deformity if not treated in a timely and appropriate manner. Currently, there is a lack of consensus among surgeons on the best approach to diagnose, characterize, and treat this condition. The objective of this review is to provide a comprehensive review of the literature to identify timely and effective diagnostic techniques and treatment modalities of AAD. Methods This review examined all articles published concerning "atlantoaxial dislocation" or "atlantoaxial subluxation" on the PubMed database. We included 112 articles published between 1966 and 2014. Results Results of these studies are summarized primarily as defining AAD, the normal anatomy, etiology of dislocation, clinical presentation, diagnostic techniques, classification, and recommendations for timely treatment modalities. Conclusions The Wang Classification System provides a practical means to diagnose and treat AAD. However, future research is required to identify the most salient intervention component or combination of components that lead to the best outcomes.

Treatment of craniocervical instability using a posterior-only approach

The object of this study was to demonstrate that a posterior-only approach for craniocervical junction pathology is feasible with intraoperative reduction. The authors reviewed 3 cases of craniocervical instability. All patients had craniocervical instability according to radiological imaging and various methods of measurement, with results outside the normal range. Posterior instrumentation aided the intraoperative reduction techniques while maintaining structural integrity and the desired fusion construct. No anterior approach was necessary in any of the patients. Neurological symptoms resolved in two patients and significantly improved in another. Follow-up imaging demonstrated stable constructs.

There are many approaches to anterior cervical pathology at the craniocervical junction. Posterior instrumented reduction and stabilization of the occipitocervical spine can be safely achieved, obviating the need for a transoral approach in the setting of craniocervical junction settling.

Indirect decompression for a prior severe C1–2 dislocation causing progressive quadriparesis

Combined anterior and posterior surgery is frequently chosen for the treatment of prior, severe C1–2 dislocations that occurred during early childhood because of the difficulty in achieving reduction and satisfactory decompression. The authors treated a prior, severe C1–2 dislocation that was causing progressive quadriparesis. The patient was a 14-year-old boy who had suffered a C1–2 fracture-dislocation at 3 years of age and had been treated with a Minerva body jacket cast. The treatment involved posterior C1–2 segmental screw fixation, without direct bone decompression or additional surgery. Satisfactory neural decompression was achieved with the techniques used, and complete bone union was confirmed. The patient showed satisfactory neurological recovery at the 5-year follow-up assessment.

Endoscopic transcervical anterior release and posterior fixation in the treatment of irreducible vertical atlantoaxial dislocation

Vertical atlantoaxial dislocation is a type of atlantoaxial instability with upper cervical spinal cord compression. The transoral ondontoid resection with posterior fixation is the gold standard for ventral decompression. Results are satisfying though surgery can be challenging due to its invasiveness. The endoscopic transcervical anterior release could provide sufficient ventral decompression with less collateral damage. In the illustrative case, anatomic reduction was achieved with significant improvement in neurological function and radiographic parameters. Endoscopic transcervical anterior release and posterior fixation appears to be a viable and interesting alternative for the treatment of vertical atlantoaxial dislocation in properly selected individuals, and its implementation could significantly reduce the post-surgical complications.

Radiographic and clinical assessment on the accuracy and complications of C1 anterior lateral mass and C2 anterior pedicle screw placement in the TARP-III procedure: a study of 106 patients

PURPOSE

To investigate the (1) radiographic and clinical accuracy of C1 anterior lateral mass screw (C1ALMS) and C2 anterior pedicle screw (C2APS) placement in the transoral atlantoaxial reduction plate (TARP)-III procedure, (2) screw insertion-associated clinical complications and (3) fusion status between C1 and C2.

METHODS

Radiographic and clinical data were obtained from the electronic medical record system. Studies were carried out to assess the accuracy of C1ALMS and C2APS placement, the screw insertion-associated clinical complications and the fusion status between C1 and C2. Placement of the screws was assessed using the modified All India Institute of Medical Sciences outcome-based classification.

RESULTS

Two-hundred and twelve C1ALMS and 207 C2APS in 106 patients were assessed. The ideal accurate rates were 92.0% (195) and 53.1% (110), and the acceptable accurate rates were 97.6% (207) and 87.0% (180), respectively. One patient died postoperatively due to C2 screw misplacement. There were no symptoms of neurologic and vertebral artery injuries in the rest of the patients. 102 patients (97.1%) achieved solid fusion between C1 and C2. No instrumentation failure due to delayed union or nonunion was observed.

CONCLUSION

C1ALMS placement in TARP-III procedures appears to be safe. The cortical breach rate of C2APS is high though clinically the neurovascular complication rate is similar to that of posterior atlantoaxial procedures. Advanced navigation strategies may help improve the accuracy of C2APS placement and decrease potential complications.

Corrective surgery for deformity of the upper cervical spine due to ankylosing spondylitis

Rotational and flexion deformity of C1-C2 due to ankylosing spondylitis is rare. We did surgical correction in one such case by lateral release, resection of the posterior arch of C1 and mobilization of the vertebral arteries, wedge osteotomy of the lateral masses of C1 and internal fixation under general anesthesia. There were no vascular and neurological complications during the surgery. After operation the atlantoaxial rotational deformity was corrected and the normal cervical lordosis was restored. At 1 year followup his visual field and feeding became normal and internal fixation was stable.

Posterior realignment of irreducible atlantoaxial dislocation with C1-C2 screw and rod system: a technique of direct reduction and fixation

BACKGROUND CONTEXT

Treatment of chronic and irreducible atlantoaxial dislocation (AAD) with ventral compression is challenging for surgeons. The main procedures are occipitocervical/C1-C2 fusion after transoral odontoidectomy or release of the periodontoid tissues. These surgical procedures, which are performed simultaneously or intermittently, have many disadvantages that may discount their effectiveness. Therefore, a more effective way to achieve surgical reduction and to keep solid stability with only a single procedure is needed.

PURPOSE

We describe a technique to reduce chronic and irreducible AAD with C1 lateral mass and C2 pedicle screw and rod system.

STUDY DESIGN

This was a retrospective case series.

PATIENT SAMPLE

Our sample comprised 26 patients (9 men and 17 women) with irreducible AAD who ranged in age from 15 to 54 years (mean, 35 years).

OUTCOME MEASURES

Patients' neurologic status was evaluated with the Japanese Orthopedic Association (JOA) scale.

METHODS

Twenty-six symptomatic patients underwent posterior realignment and reduction through the C1 lateral mass and C2 pedicle screw and rod system. The proposed mechanism of reduction is that the implanted screws and rods between C1 and C2 acting as a lever system drew C1 backward and pushed C2 downward and forward after removing circumambient obstruction and scars and thoroughly releasing the facet joints. The preoperative and postoperative JOA score, the extent of reduction, and the conditions of C1-C2 bony fusion were examined.

RESULTS

No neurovascular injury occurred during surgery. Follow-up ranged from 6 to 40 months (mean 20.7 months). Radiographic evaluation showed that solid bony fusion was achieved in all patients, and that complete reduction was attained in 18 patients and partial reduction (>60% reduction) in 8 patients. The mean postoperative JOA score at last follow-up was 15.7, compared with the preoperative score of 12.1 (p<.01).

CONCLUSIONS

This C1-C2 screw and rod system provides reliable stability and sufficient reduction of the anatomic malalignment at the craniovertebral junction and meanwhile retains the mobility of atlanto-occipital joints in the treatment of chronic and irreducible AAD. Sophisticated skills, thorough release of the facet joints, and intraoperative protection of the vertebral artery are key points to accomplish this technique.

Novel surgical classification and treatment strategy for atlantoaxial dislocations

STUDY DESIGN

Retrospective study of 904 patients with a diagnosis of atlantoaxial dislocation (AAD), using a novel surgical classification and treatment strategy.

OBJECTIVE

To describe a novel surgical classification and treatment strategy for AADs.

SUMMARY OF BACKGROUND DATA

AADs can result from a variety of etiologies, yet no comprehensive classification has been accepted that guides treatment. Because of the rarity of the cases, however, the treatment strategy has also been debated.

METHODS

During a period of 12 years, a total of 904 patients with a diagnosis of AAD were recruited from a single academic institution. According to the treatment algorithm that included preoperative evaluation using dynamic radiograph, reconstructive computed tomography, and skeletal traction test, the cases were classified into 4 types: I to IV. Types I and II were fused in the reduced position from a posterior approach. Type III, which were irreducible dislocations, were converted to reducible dislocations using a transoral atlantoaxial release, followed by a posterior fusion. Type IV presented with bony dislocations and required transoral osseous decompressions prior to posterior fusion.

RESULTS

Four hundred seventy-two cases were classified as type I, 160 as type II, 268 as type III, and 4 cases as type IV. Follow-up was in the range of 2 to 12 years (average: 60.5 mo). Eight hundred and ninety-nine cases (99.4%) achieved a solid atlantoaxial fusion. Anatomic atlantoaxial reduction was achieved in 892 cases (98.7%), whereas 12 cases had a partial reduction. Neurological improvement was seen in 84.1% (512/609) of the patients with myelopathy. The overall complication rate was 9.1% (82/949).

CONCLUSION

Our surgical classification and treatment strategy for AADs was applied in those 904 cases and associated with excellent clinical results with a minimal risk of complications.

LEVEL OF EVIDENCE

4.

Endoscopic transnasal odontoidectomy combined with posterior reduction to treat basilar invagination: technical note

OBJECT

Transoral microscopic odontoidectomy has been accepted as a standard procedure to treat basilar invagination over the past several decades. In recent years the emergence of new technologies, including endoscopic odontoidectomy and posterior reduction, has presented a challenge to the traditional treatment algorithm. In this article, the authors describe 1 patient with basilar invagination who was successfully treated with endoscopic transnasal odontoidectomy combined with posterior reduction. The purpose of this report is to validate the effectiveness of this treatment algorithm in selected cases and describe several operative nuances and pearls based on the authors' experience.

METHODS

One patient with basilar invagination caused by a congenital osseous malformation underwent endoscopic transnasal odontoidectomy combined with posterior reduction in a single operative setting. The purely endoscopic transnasal odontoidectomy was first conducted with the patient supine. The favorable anatomical reduction was then achieved through a posterior approach after the patient was moved prone.

RESULTS

The patient was extubated after recovery from anesthesia and allowed oral food intake the next day. No complications were noted, and the patient was discharged 4 days after the operation. Postoperative imaging demonstrated excellent decompression of the anterior cervicomedullary junction pathology. The patient was followed up for 12 months and remarkable neurological recovery was observed.

CONCLUSIONS

The endoscopic transnasal odontoidectomy is a better minimally invasive approach for anterior decompression and can make the posterior reduction easier because the anterior resistant force is eliminated. The subsequent posterior reduction can make decompression of the ventral side of the cervicomedullary junction more effective because the C-2 vertebral body is pushed forward. A combination of these 2 approaches has the advantages of minimally invasive access and a faster patient recovery, and thus is a valid alternative in selected cases.

Distraction, Compression, and Extension Reduction of Basilar Invagination and Atlantoaxial Dislocation

BACKGROUND:

The management of basilar invagination (BI) and atlantoaxial dislocation (AAD) is a challenge.

OBJECTIVE:

To describe a new innovative method to reduce BI and AAD through a single-stage posterior approach.

METHODS:

Thirty-five patients had irreducible BI and AAD (May 2010 to April 2012). In all patients, reduction of AAD and BI was achieved by using an innovative method of distraction and spacer placement, followed by compression and extension. A C1 lateral mass/C2 translaminar screw was performed in cases where the C1 arch was not assimilated, and occipito-C2 translaminar screw fixation was performed in cases where the C1 arch was assimilated.

RESULTS:

Thirty-two of 35 (94%) patients improved clinically and 2 patients had stable symptoms (mean Nurick postoperative score = 1.4; preoperative score = 3.7). AAD reduced completely in 33/35 patients and &gt;50% in 2. BI improved significantly in all patients. Solid bone fusion was demonstrated in 24 patients with at least 1-year follow-up (range, 12-39 months; mean, 19.75 + 7.09 months). The duration of surgery was 80 to 190 minutes, and blood loss was 90 to 500 mL (mean, 170 ± 35 mL). There was 1 death because of cardiac etiology and 1 morbidity (wound infection).

CONCLUSION:

Distractive compressive extension and reduction of BI and AAD seems to be an effective and safe method of treatment. It is different from the earlier described techniques, because it is the first procedure that uses a spacer not, only for distraction, but also as a pivot to perform extension to reduce the AAD.

Morphology of the atlas pedicle revisited: a morphometric CT-based study on 120 patients

PURPOSE

To quantify the dimensions of the atlas pedicles and to analyze the relationship between extra medullary height (EMH) with intra medullary height (IMH) of the atlas pedicle.

METHODS

The images of the patients who had CT scanning and three-dimensional (3D) reconstruction involving atlantoaxial complex between June 2011 and April 2012 and meet our inclusion criteria were studied retrospectively. After reformatting the original images, the EMH and IMH of the atlas pedicles were measured.

RESULTS

Extra medullary height and IMH were, respectively, 4.83 ± 1.13 and 1.29 ± 1.10 mm for males and 3.75 ± 0.93 and 0.60 ± 0.83 mm for females, with statistical difference (P < 0.05). EMH and IMH had some correlation (correlation coefficient r = 0.804) but showed a large variability. Of 240 pedicles of 120 cases, 47.92% (115 pedicles) were ≥1 mm; 12.08% (29 pedicles) were between 0 and 1 mm; and 40% (96 pedicles) were 0.

CONCLUSION

The EMH and the IMH of the atlas pedicles were measured by using CT images of the atlas, providing anatomic parameters for surgery. They showed a certain correlation but with a high variability. C1 pedicle screw fixation was well performed when the medullary canal was ≥1 mm, but the surgical procedure should be careful when it was between 0 and 1 mm, and avoided when there was no medullary canal in the atlas pedicle! So 3D CT reconstruction should be conducted to obtain data and establish individualized fixation strategy preoperatively.

New clinical classification system for atlantoaxial dislocation

The purpose of this study was to define a new clinical classification of atlantoaxial dislocation based on its clinical manifestations, namely reducible atlantoaxial dislocation (RAAD), irreducible atlantoaxial dislocation (IAAD), and fixed atlantoaxial dislocation (FAAD). A total of 107 patients with atlantoaxial dislocation were respectively treated based on this clinical classification, including 66 patients with RAAD, 39 patients with IAAD, and 2 patients with FAAD. Six of the 66 patients with RAAD with rotatory atlantoaxial dislocation were treated with traction and a cervical collar, 9 with fresh type II dens fracture were treated with cannulated screw fixation, and 51 were treated with posterior atlantoaxial or occipitocervical arthrodesis. Thirty-eight patients with IAAD received a transoral atlantoaxial reduction plate system, and 1 with a giant cell tumor was treated with lesion resection and vertebral reconstruction by a shaped titanium mesh system followed by posterior occipitocervical screw-rod fixation. The 2 patients with FAAD underwent anterior decompression and received a transoral atlantoaxial reduction plate system. Follow-up data were obtained for a minimum of 6 months. All patients' neurological symptoms improved postoperatively. Bony union was accomplished by 3-month follow-up. Donor-site infection was found in 1 patient, with no occurrence of other complications. This article proposes a new classification of atlantoaxial dislocation indicating the severity and difficulty in reduction of the atlantoaxial joint. The classification system assists with decision making regarding therapeutic options. Transoral atlantoaxial reduction plate fixation and posterior atlantoaxial screw-rod fixation are commonly performed for atlantoaxial dislocation.

Cable-Strengthened C2 Pedicle Screw Fixation in the Treatment of Congenital C2-3 Fusion, Atlas Occipitalization, and Atlantoaxial Dislocation

BACKGROUND:

Atlas occipitalization and congenital C2-3 fusion often result in atlantoaxial dislocation (AAD) and superior odontoid migration that requires occipitocervical fixation. The widely used technique is posterior occiput-C2 fixation with pedicle screws. However, congenital C2-3 fusion cases tend to have thinner C2 pedicles that are inadequate for normal-sized pedicle screw fixation. With the presence of AAD, the strength of the fixation is further compromised as the C2 pedicle screws (C2PS) sustain considerable cephalic shearing force during the reduction procedure. Therefore, a novel technique has been developed to augment the C2 pedicle screw fixation with a strengthening cable.

OBJECTIVE:

To introduce and assess this new technique.

METHODS:

Seventy-six patients who underwent this procedure were reviewed. The position of the instrument and resultant fusion were examined retrospectively. In the biomechanical test, 6 fresh specimens were subjected to 2 types of fixation in the order of Oc-C2 screw-plate fixation followed by additional use of strengthening cable. Under 3 loading modes (extension-flexion, lateral bending, and axial rotation), the relative movement between the occiput and C2 was measured and compared in the form of range of motion.

RESULTS:

The average follow-up time was 26 months. Solid fusion was achieved in 75 patients (98.7%) as assessed radiologically. The only patient who experienced hardware failure eventually obtained solid fusion between the occiput and C2 after revision. Biomechanically, there was significant difference between the occiput and C2 fixation and cable-strengthened fixation in range of motion for all modes.

CONCLUSION:

This technique is a promising option for the treatment of AAD with congenital C2-3 fusion and occipitalization. Biomechanically, this technique can reduce the occipital-axial motion significantly compared with occiput-C2 fixation.

A retrospective study of congenital osseous anomalies at the craniocervical junction treated by occipitocervical plate-rod systems

PURPOSE

To evaluate the effectiveness of posterior occipitocervical reconstruction using the anchors of cervical pedicle screws and plate-rod systems for patients with congenital osseous anomalies at the craniocervical junction.

METHODS

Twenty patients with congenital osseous lesions who underwent posterior occipitocervical fusion using the anchors of cervical pedicle screws and plate-rod systems for reduction and fixation from 1996 to 2009 were reviewed. The lesions included os odontoideum, occipitalization of the atlas, congenital C2-3 fusion, congenital atlantoaxial subluxation, congenital basilar invagination and combined anomalies. The clinical assessment and the measurements of the images were performed preoperatively, postoperatively and at most recent follow-up.

RESULTS

The combined deformity of flexion of the occipitoatlantoaxial complex and invagination of the odontoid process associated with congenital osseous lesions at the craniocervical junction was corrected by application of combined forces of extension and distraction between the occiput and the cervical pedicle screws. Preoperative myelopathy improved in 94.7% patients. The mean Ranawat value, Redlund-Johnnell value, atlantodental distance, occiput (O)-C2 angle, and C2-C7 lordosis angle improved postoperatively and was sustained at most recent follow-up. The mean cervicomedullary angle improved from 129.3° preoperatively to 153.3° postoperatively. The mean range of motion at the lower adjacent motion segment remained unchanged at most recent follow-up. The fusion rate was 95%.

CONCLUSIONS

The results of the present study indicate that posterior occipitocervical reconstruction using the anchors of cervical pedicle screws and plate-rod systems is an effective technique for treatment of deformities and/or instability caused by congenital osseous anomalies at the craniocervical junction.

Three-dimensional configuration and morphometric analysis of the lateral atlantoaxial articulation in congenital anomaly with occipitalization of the atlas

STUDY DESIGN

Observational and quantitative study with 3-dimensional (3D) computerized tomographic (CT) analysis.

OBJECTIVE

To establish the 3D configuration and morphometric data of obliquity of the lateral atlantoaxial articulations (LAA) in congenital anomaly with occipitalization.

SUMMARY OF BACKGROUND DATA

Plane radiographs and normal CT scans cannot clearly demonstrate the configuration of LAA as the hindrance of circumambient bony structures. The morphology of anomalous LAA with occipitalization is underreported.

METHODS

A series of 63 cases with occipitalization and 20 control subjects underwent thin-slice CT scanning. The 3D configuration of LAA were analyzed and categorized based on the degree of olisthy and inclination orientation of the atlantoaxial articular facets (AAF). The obliquity of the AAF was measured in reconstructed sagittal and coronal planes, respectively.

RESULTS

Four types of configuration of LAA with occipitalization were found: type I, characterized by slight anteversion of LAA without olisthy of the inferior and superior facets (16% of 126 sides); type II, characterized by partial olisthy of the 2 facets and evident anteversion of LAA (48%); type III, defined by the separation or complete olisthy of the 2 facets (13%); and type IV, wherein the articular facets sloped dorsally (23%). Forty-eight of 49 cases in the former 3 types wherein AAF sloped ventrally had atlantoaxial dislocation (AAD). All type IV cases wherein AAF sloped dorsally had no AAD. In control subjects, LAA had no evident obliquity of anteversion or retroversion.

CONCLUSION

Instability at the C1-C2 junction in congenital anomaly with occipitalization is likely a direct result of the anteversion of LAA and bony malformation of this region, and it aggratates with the increasing obliquity of anteversion of the AAF. Demonstrating 3D morphological changes of LAA may provide a new means to diagnosis instability in congenital anomaly at craniovertebral junction and a basis for rational surgical treatment.

Posterior occipitocervical fixation under skull-femoral traction for the treatment of basilar impression in a child with Klippel-Feil syndrome

We present the case of a 15-year-old boy with symptoms due to Klippel-Feil syndrome. Radiographs and CT scans demonstrated basilar impression, occipitalisation of C1 and fusion of C2/C3. MRI showed ventral compression of the medullocervical junction. Skull traction was undertaken pre-operatively to determine whether the basilar impression could be safely reduced. During traction, the C3/C4 junction migrated 12 mm caudally and spasticity resolved. Peri-operative skull-femoral traction enabled posterior occipitocervical fixation without decompression. Following surgery, cervical alignment was restored and spasticity remained absent. One year after surgery he was not limited in his activities. The surgical strategy for patients with basilar impression and congenital anomalies remains controversial. The anterior approach with decompression is often recommended for patients with ventral compression of the medullocervical region, but such procedures are technically demanding and carry a significant risk of complications. Our surgical strategy was an alternative solution. Prior to a posterior cervical fixation, without decompression, skull traction was used to confirm that the deformity was reducible and effective in resolving associated myelopathy.

Vertical reduction using atlantoaxial facet spacer in basilar invagination with atlantoaxial instability

Although posterior segmental fixation technique is becoming increasingly popular, surgical treatment of craniovertebral junctional disorders is still challenging because of its complex anatomy and surrounding critical neurovascular structures. Basilar invagination is major pathology of craniovertebral junction that has been a subject of clinical interest because of its various clinical presentations and difficulty of treatment. Most authors recommend a posterior occipitocervical fixation following transoral decompression or posterior decompression and occipitocervical fixation. However, both surgical modalities inadvertently sacrifice C0-1 and C1-2 joint motion. We report two cases of basilar invagination reduced by the vertical distraction between C1-2 facet joint. We reduced the C1-2 joint in an anatomical position and fused the joint with iliac bone graft and C1-2 segmental fixation using the polyaxial screws and rods C-1 lateral mass and the C-2 pedicle.

Combined occipitoatlantoaxial rotatory fixation

Occipitoatlantoaxial rotatory fixation (OAARF) is a rare condition involving fixed rotational subluxation of the atlas in relation to both the occiput and axis. Atlantoaxial rotatory fixation (AARF) appears to precede OAARF in most cases, as untreated AARF may cause compensatory counter-rotation and occipitoaxial fixation at an apparently neutral head position. We report a case of OAARF in an 8-year-old girl with juvenile idiopathic arthritis. Cervical imaging demonstrated slight rightward rotation of the occiput at 7.63° in relation to C-2 and significant rightward rotation of C-1 at 65.90° in relation to the occiput and at 73.53° in relation to C-2. An attempt at closed reduction with halo traction was unsuccessful. Definitive treatment included open reduction, C-1 laminectomy, and occipitocervical internal fixation and fusion.

The options of C2 fixation for os odontoideum: a radiographic study for the C2 pedicle and lamina anatomy

INTRODUCTION

Patients with os odontoideum always present instability in atlantoaxial joint and need atlantoaxial fixation. C2 pedicle or laminar screws fixation has proven to be efficient and reliable for atlantoaxial instability. However, os odontoideum is a congenital or developmental disease, featured with anomalous bony anatomies. The anatomic measurements and guidelines for C2 pedicle screw placement in general population tends to differ with those of os odontoideum patients, for whom C2 pedicle screws are often needed. The option and techniques of C2 fixation are still challenging and yet to be fully explored.

MATERIAL AND METHODS

We recruited 29 adult patients with os odontoideum and measured the dimension of C2 pedicle and lamina for each patient to examine how well do they match with the screws anatomically. In order to access the intra-observer reliability and inter-observer repeatability of the measurements, the intraclass correlation coefficient (ICC) was also calculated.

RESULTS

The results for reliability of the CT measurements showed excellent intraobserver (ICC = 0.95 and 0.96) and interobserver correlation coefficient (ICC = 0.93). The diameter and length of C2 pedicle were found to be 6.06 ± 1.37 and 24.05 ± 2.54 mm, while the corresponding figures of C2 laminar were 6.95 ± 0.82 and 25.60 ± 2.18 mm, respectively. In the measurements, all 29 cases had suitable diameter (larger than 5.5 mm) for C2 laminar screw (the laminar diameters ranged from 5.52 to 8.82 mm). In C2 pedicle measurements, the diameters of the 29 cases were from 3.50 to 9.86 mm, while 20 pedicles (34.5%) in 14 cases were less than 5.5 mm in diameter. Six had bilateral small pedicles where the diameter was less than 5.5 mm.

CONCLUSION

Anatomically, we found laminar screw is a better match in comparison with pedicle screw for C2 fixation in os odontoideum. The options for C2 fixation should be made based on careful preoperative imaging and thorough consideration. Preoperative reconstructive CT scan can offer great assistance for the choice of fixation in os odontoideum by revealing the anatomy of the C2 pedicles in detail.

Treatment of irreducible old atlantoaxial subluxation with cable-dragged reduction and cantilever beam internal fixation

STUDY DESIGN

Retrospective case series study of surgical outcome for 21 atlantoaxial subluxation patients treated with a new technique, called cable-dragged reduction/cantilever beam internal fixation. Surgery was performed by a single surgeon.

OBJECTIVE

To describe and evaluate the cable-dragged reduction/cantilever beam internal fixation technique for the treatment for old atlantoaxial subluxation irreducible by traction.

SUMMARY OF BACKGROUND DATA

Management of old atlantoaxial subluxation has always been a difficult task. A more effective way to achieve surgical reduction is needed.

MATERIALS AND METHODS

Twenty one patients, aged 31.6 ± 13.3 years (range, 11-67 years), 17 men and four women, with atlantoaxial subluxation that failed to be reduced after 10 to 111 days in traction, underwent posterior cable-dragged reduction/cantilever beam internal fixation surgery. Frankel classification of neural function before surgery was the following: Frankel B, four patients; Frankel C, five patients; Frankel D, four patients; and Frankel E, eight patients. Plain radiographs, computed tomographic three-dimensional reconstructive images and magnetic resonance images of the cervical spine were obtained at 3, 6, and 12 months after surgery, and each year thereafter. No patient was lost to follow-up, and the follow-up time ranged from 6 months to 4 years. Rate of reduction and C1∼3 fusion, as well as improvement of neural function, were recorded and analyzed.

RESULTS

The average follow-up period was 13.2 months. Radiographic evaluation of the group at follow-up showed 16 complete and five partial reductions, and satisfactory decompression and C1∼3 fusion in all cases. Neural function at the end of the follow-up was Frankel B still in one patient, Frankel C in seven patients, and Frankel E in 13 patients.

CONCLUSION

Cable-dragged reduction/cantilever beam internal fixation is almost as effective for reduction as anterior release but is less invasive and risky. It has similar operative time and blood loss to occipitocervical fusion but avoids arthrodesis of occipitoatlantal joint. It is also suitable for patients with severe myelopathy before surgery. Its major disadvantage is that C3, which is left free in the traditional atlantoaxial fusion surgery, has to be involved in fusion. And it is suitable only for patients with intact posterior arches in C1.

Revision surgery of irreducible atlantoaxial dislocation: a retrospective study of 16 cases

There is lack data concerning anterior cervical spine revision surgeries; even more data are missing concerning posterior cervical revision surgeries, to determine the feasibility, safety, and clinical efficacy of revision surgery for irreducible atlantoaxial dislocation (RS-IAAD). Patients with IAAD-FS underwent one-stage transoral release and posterior reduction. Their medical history was documented in detail. The JOA score system was used to evaluate each patient's neurological status pre and postoperatively, and serial MRI and radiographs were used to determine the status of the reduction and the autografts. 16 patients (average age, 36 years old) underwent successful surgery. There was no intraoperative or postoperative neurological deficit except in two cases that suffered transient neurological deficit that alleviated after conservative treatment. Solid bony union was seen at the end of 3 months after surgery in all patients. The mean follow-up period was 28.8 months (range 18-66 months). No pseudarthrosis was noted. Anterior transoral release and posterior instrumented fusion remain significant surgeries with the potential for serious complications, but in the current series there were no major complications.

Radiographic evaluation of the technique for C1 lateral mass and C2 pedicle screw fixation in three hundred nineteen cases

STUDY DESIGN

Retrospective radiographic study of the technique for C1 lateral mass screw (C1LMS) and C2 pedicle screw (C2PS) fixation.

OBJECTIVE

To evaluate (1) the accuracy of the C1LMS and C2PS placement; (2) the fusion rate between C1 and C2; (3) the risk for vertebral artery (VA) injury.

SUMMARY OF BACKGROUND DATA

C1LMS and C2PS fixation is widely used when treating atlantoaxial instability. Several authors have reported their experience focusing on the technical outcomes, with many reporting fusion rates near 100%. However, most of them are relatively small series, and many have applied only plain postoperative radiographs instead of computed tomography (CT). Thus, we feel that the accuracy of C1LMS and C2PS placement has not been fully analyzed, as well as the anatomic relationship between the VA and the screws.

METHODS

Between December 2000 and September 2008, the fusion status and accuracy of the screws were evaluated on the postoperative reconstructive CT of 319 patients with atlantoaxial instability. Cases with malpositioned screws underwent CT angiography or magnetic resonance angiography after surgery, to evaluate potential VA injury.

RESULTS

C1LMS of 95.5% and C2PS of 92.8% were found to be in a "good" position. After 2007, six cases had malpositioned screws, which were all in the "out" or "down" area of the C2 pedicle. Five cases underwent CT angiography and 1 had magnetic resonance angiography to evaluate potential VA injury. No occlusion, associated aneurysm or fistula of the VA was found. All cases (100%) achieved solid fusion between C1 and C2.

CONCLUSION

C1LMS of 95.5% and C2PS of 92.8% were confirmed to be in good position. None of the screws including the malpositioned caused VA injury, clinically or radiographically. The technique for C1LMS and C2PS fixation appears to be safe and effective.

Novel technique of reduction of a chronic atlantoaxial rotatory fixation using a temporary transverse transatlantal rod

BACKGROUND CONTEXT

Chronic atlantoaxial rotatory fixation (AARF) is uncommon as acute AARF is easily reduced either spontaneously or by conservative methods. Various anterior and posterior surgical approaches for a chronic AARF have been reported because of the difficulty encountered in obtaining reduction.

PURPOSE

To describe a novel technique of reduction of a chronic AARF using a temporary transverse transatlantal rod.

STUDY DESIGN

Technical report.

METHODS

A 13-year-old girl presented with an 8-month-old chronic AARF with typical torticollis and "cock-robin" posture of the head with a normal neurology. As closed reduction with skull traction for 2 weeks failed to reduce the deformity, the patient underwent C1-C2 fusion. C1 lateral mass and C2 pedicle screws were inserted under computer navigation. A temporary transverse rod across the atlas and axis was placed to secure a three-column fixation to derotate the subluxed atlas into anatomical alignment. Rods were then connected between the C1 lateral masses and the C2 pedicle screws and fusion obtained with autologous iliac crest grafts.

RESULT

Anatomic reduction of the atlantoaxial region was obtained without neural compromise, and satisfactory fusion was observed at 6-months follow-up.

CONCLUSION

A temporary transatlantal rod provides a secure anchor point for easy maneuverability for reduction of a chronic AARF and has the advantage of being used even in the absence of the posterior arch of the atlas.

Video-assisted anterior transcervical approach for the reduction of irreducible atlantoaxial dislocation

STUDY DESIGN

Technique note.

OBJECTIVE

To describe a modified minimally invasive approach for the treatment of irreducible atlantoaxial dislocation (IAAD).

SUMMARY OF THE BACKGROUND DATA

Currently, the most frequently used route for the treatment of symptomatic IAAD is transoral-transpharyngeal approach. Although it provides the most direct route to the atlantoaxial joint, potential problems may arise because of traverse oral cavity, such as the potential risks of infection, postoperative disturbances of breathing, and swallowing. The aim of this study was to describe a less-invasive approach for IAAD.

METHODS

Four consecutive patients with IAAD underwent the combined video-assisted atlantoaxial transcervical release (VAAT) procedure and posterior occipital-cervical fusion or C1-C2 screw fixation at Tongji Hospital. Clinical characteristics, images data, operative variables, and follow-up data were recorded.

RESULTS

Four cases presented with signs and symptoms of spinal cord dysfunction caused by IAAD underwent 1-stage anterior release, reduction, and posterior fixation. Three cases received C1-C2 screw fixation, and 1 case with occipitocervical fixation. Postoperative imaging studies showed that complete decompression was achieved in all the cases. No systemic infections, cerebrospinal fluid leaks, or adverse neurologic sequelae were found. None of the patients required prolonged intubation, tracheostomy, or enteral tube feeding. All patients started to oral intake after anesthesia. Neurologic status in 1 case remained at baseline whereas it improved in the others. The mean follow-up period was 9 months (6 approximately 12 months). All cases achieved solid fusion, without implants failure.

CONCLUSION

Our initial experience showed that the VAAT procedure for IAAD is a safe supplement and alternative to conventional and transcervical procedures.

Direct posterior reduction and fixation for the treatment of basilar invagination with atlantoaxial dislocation

OBJECTIVE

To report the surgical technique and clinical results for the treatment of basilar invagination (BI) with atlantoaxial dislocation (AAD) by direct posterior reduction and fixation using intraoperative distraction between the occiput and C2 pedicle screws.

METHODS

From May 2004 to June 2008, 29 patients who had BI with AAD were surgically treated in our department. Pre- and postoperative dynamic cervical x-rays, computed tomographic scans, and 3-dimensional reconstruction views were performed to assess the degree of dislocation. Ventral compression of the cervicomedullary junction was evaluated by magnetic resonance imaging. For all patients, reduction of the AAD was conducted by intraoperative distraction between the occiput and C2 pedicle screws using a direct posterior approach.

RESULTS

Follow-up ranged from 6 to 50 months in 28 patients. Clinical symptoms improved in 26 patients (92.9%) and were stable in 2 patients (7.1%) without postoperative deterioration. Radiologically, complete or more than 50% reduction was achieved in 27 of 28 patients (96.4%). In 1 patient, the reduction was less than 50% because the direction of the facets on 1 side of the C1-C2 joint was vertically oriented, instead of horizontal. Overall, good decompression and bone fusion were shown on postoperative magnetic resonance imaging, computed tomography, or x-ray scans for all patients. There was 1 death in the series because of basilar artery thrombosis 1 week after the operation.

CONCLUSION

The direct posterior distraction technique between occiput and C2 pedicle screws is an effective, simple, fast, and safe method for the treatment of BI with AAD. Transoral odontoidectomy and cervical traction for the treatment of BI with AAD should be reconsidered.

Endoscopically assisted anterior release and reduction through anterolateral retropharyngeal approach for fixed atlantoaxial dislocation

STUDY DESIGN

A prospective study.

OBJECTIVE

To evaluate a novel technique involving an endoscopically assisted anterior release and reduction through an anterolateral retropharyngeal approach with minimum follow-up interval of 31 months.

SUMMARY OF BACKGROUND DATA

Irreducible atlantoaxial dislocation is typically a chronic process that requires surgical treatment. However, the current literature does not agree on the single best method of treatment. Previously, the best outcomes have been reported with transoral reduction followed by anterior or posterior fixation. Despite recent innovations, numerous complications remain associated with this approach.

METHODS

About 21 consecutive irreducible atlantoaxial dislocation patients with mean age of 32 years underwent endoscopically assisted anterior release and reduction through the anterolateral retropharyngeal approach followed by posterior fixation. The primary pathologies included 8 late odontoid fractures, 7 cases of os odontoideum, 5 with laxity of the transverse ligament, and 1 with atlanto-occipital assimilation with a hypoplastic odontoid. Neurologic status was evaluated using the Japanese Orthopedic Association scoring system. Radiographic parameters including the atlantodental interval (ADI) and cervicomedullary angle were also measured. Follow-up data were obtained for a minimum of 31 months.

RESULTS

Anatomic reduction was achieved in 20 cases and near-anatomic reduction in 1 case. All patients had an uneventful recovery with significant improvement in neurologic function and radiographic parameters. No complications were seen. The atlantodental interval was corrected from an average 6.3 mm before surgery to 2.7 mm after surgery (P < 0.01). The cervicomedullary angle was also corrected from an average 109 degrees before surgery to 152 degrees after surgery (P < 0.01). Preoperative muscle strength was on average 3.5 (on scale from 1 to 5) and improved after surgery to 4.5 (P < 0.01). The average preoperative and postoperative Japanese Orthopedic Association scores were 9.6 and 15.5, respectively, indicating 82.8% improvement.

CONCLUSION

Endoscopically assisted anterior retropharyngeal release combined with posterior fixation is a safe and effective alternative for the treatment of irreducible atlantoaxial dislocation.

Interobserver and intraobserver reliability of the cervicomedullary angle in a normal adult population

CMA values have been effectively used to evaluate the amount of BI, the brainstem and medulla compression, and the amount of postoperative decompression. However, the reliability and reproducibility of this measurement have yet to be determined. In addition, the information that is available concerning CMA values in normal individuals has been limited to small series of patients. We recruited 200 patients that underwent MR imaging of the craniovertebral junction (CVJ) for unrelated reasons. None of the patients had evidence of abnormalities at the CVJ. Two senior spine surgeons then measured the CMAs of these patients in a blind manner on three separate occasions. The CMA values ranged from 139.0 degrees to 175.5 degrees , with an average value of 158.46 degrees , and a 95% confidence interval from 144.8 degrees to 172.1 degrees . Overall, the CMA had excellent intraobserver repeatability and interobserver reliability. The CMA also had excellent intraobserver repeatability based on both the age and gender of the patients (P = 0.87 and 0.93, respectively). At the same time, the CMA also demonstrated excellent interobserver reliability based on gender (P = 0.97), while good interobserver reliability based on patients age (P = 0.23). No significant correlation between the actual CMA values and the patients' gender (P = 0.17), age (P = 0.058), or spin-echo series used (P = 0.342). This study demonstrated that CMA values obtained from midsagittal T1 MR images were a highly reliable and repeatable measurement. The data reported in this study can be used as baseline parameters for normal individuals.

C2-fractures: part II. A morphometrical analysis of computerized atlantoaxial motion, anatomical alignment and related clinical outcomes

Knowledge on the outcome of C2-fractures is founded on heterogenous samples with cross-sectional outcome assessment focusing on union rates, complications and technical concerns related to surgical treatment. Reproducible clinical and functional outcome assessments are scant. Validated generic and disease specific outcome measures were rarely applied. Therefore, the aim of the current study is to investigate the radiographic, functional and clinical outcome of a patient sample with C2-fractures. Out of a consecutive series of 121 patients with C2 fractures, 44 met strict inclusion criteria and 35 patients with C2-fractures treated either nonsurgically or surgically with motion-preserving techniques were surveyed. Outcome analysis included validated measures (SF-36, NPDI, CSOQ), and a functional CT-scanning protocol for the evaluation of C1-2 rotation and alignment. Mean follow-up was 64 months and mean age of patients was 52 years. Classification of C2-fractures at injury was performed using a detailed morphological description: 24 patients had odontoid fractures type II or III, 18 patients had fracture patterns involving the vertebral body and 11 included a dislocated or a burst lateral mass fracture. Thirty-one percent of patients were treated with a halo, 34% with a Philadelphia collar and 34% had anterior odontoid screw fixation. At follow-up mean atlantoaxial rotation in left and right head position was 20.2 degrees and 20.6 degrees, respectively. According to the classification system of posttreatment C2-alignment established by our group in part I of the C2-fracture study project, mean malunion score was 2.8 points. In 49% of patients the fractures healed in anatomical shape or with mild malalignment. In 51% fractures healed with moderate or severe malalignment. Self-rated outcome was excellent or good in 65% of patients and moderate or poor in 35%. The raw data of varying nuances allow for comparison in future benchmark studies and metaanalysis. Detailed investigation of C2-fracture morphology, posttreatment C2-alignment and atlantoaxial rotation allowed a unique outcome analysis that focused on the identification of risk factors for poor outcome and the interdependencies of outcome variables that should be addressed in studies on C2-fractures. We recognized that reduced rotation of C1-2 per se was not a concern for the patients. However, patients with worse clinical outcomes had reduced total neck rotation and rotation C1-2. In turn, C2-fractures, especially fractures affecting the lateral mass that healed with atlantoaxial deformity and malunion, had higher incidence of atlantoaxial degeneration and osteoarthritis. Patients with increased severity of C2-malunion and new onset atlantoaxial arthritis had worse clinical outcomes and significantly reduced rotation C1-2. The current study offers detailed insight into the radiographical, functional and clinical outcome of C2-fractures. It significantly adds to the understanding of C2-fractures.

The single transoral approach for Os odontoideum with irreducible atlantoaxial dislocation

We report a 52-year-old female patient with a 2-year history of local neck pain, decreased cervical spine rotation, progressive numbness and weakness of both arms. Preoperative, dynamic X-rays, computed tomography, three-dimensional computed tomography demonstrated a displaced Os odontoideum with irreducible Subluxation of C1/2. We used a single transoral approach release, reduction using an assistance of skull traction, bone fusion and stabilization in the treatment of Os odontoideum with irreducible alantoaxial dislocation. Postoperative, the patient was free of all symptoms and X-rays taken showed a stable fusion of C1/2 at 6th postoperative month. This technique in the treatment of Os odontoideum with irreducible alantoaxial dislocation is atraumatic and effective. And preoperative dynamic X-rays, computed tomography, three-dimensional computed tomography and MRI scans provided an invaluable aid to select this operative procedure.

C2-fractures: part I. Quantitative morphology of the C2 vertebra is a prerequisite for the radiographic assessment of posttraumatic C2-alignment and the investigation of clinical outcomes

Pertinent literature exists concerning indications, techniques, complications of treatment, and risk factors for nonunion in axis and odontoid fractures; however, there are scarce data regarding the incidence and definition of malunion in these fractures. As a prerequisite for the study of anatomical alignment following surgical and nonsurgical treatment of C2-fractures, an understanding of normal C2 anatomy is essential. Therefore, the authors intended to evaluate morphometrical dimensions of the C2 vertebra. The purpose was to provide normalized quantitative data to enable assessment of malalignment following the treatment of C2-fractures within a classification system. Using digitized cervical spine lateral and transoral odontoid radiographs of 100 consecutive patients without any evidence of traumatic or neoplastic disorders, the authors performed measurements on distinct anatomical structures and investigated morphometrical dimensions of the normal axis vertebra. The incidence of atlantoaxial arthritis was also evaluated. In addition, with the assessment of twenty arbitrarily chosen sets of radiographs by three different observers we calculated the interobserver reliability in terms of intraclass correlation coefficients for each parameter. With calculation of SD and 95% confidence limits, pathological cut-offs were reconstructed from measurements performed resembling non-physiological and pathological limits. Distinct parameters were selected to form a new classification system for radiographical follow-up that focuses on the quantitative C1-2 vertebral alignment. The measurement process resulted in 2,400 data points. Distinct morphometrical parameters, such as a quantitative characterization of the sagittal atlantoaxial congruency, the lateral mass inclination and the type of degenerative changes at the atlantoaxial joint could be demonstrated to be valuable and reliably used within a proposed classification for C2-malunions following C2-fractures. The current study offers a template including recommended radiological measurements for further research on the study of clinical outcome and posttraumatic alignment following C2-fractures.

Pre-operative irreducible C1-C2 dislocations: intra-operative reduction and posterior fixation. The "always posterior strategy"

BACKGROUND

According to Menezes' algorithm, pre-operative dynamic neuroradiological investigation in C1-C2 dislocations (C1C2D) instability is strongly advocated in order to exclude those patients not eligible for posterior fixation and fusion without previous anterior trans-oral decompression. Anterior irreducible compression due to C1C2D instability, it is said, needs trans-oral anterior decompression. We reviewed our experience in order to refute such a paradigm.

METHODS

The study involves 23 patients who were operated on for cranio-vertebral junction (CVJ) instability; all of them had C1C2D of varying degree on x-ray, computerised tomography (CT) and magnetic resonance (MR) imaging of the CVJ. Pre-operatively, irreducible C1C2D was demonstrated only in 3 patients, (2 with Down's Syndrome, one of them was harbouring os odontoideum, 1 Rheumatoid Arthritis), i.e. 13.04%; the remaining 19 (86.9%) had reducible C1-C2 dislocation. After an unsuccessful traction test conducted in the pre-operative phase under sedation, it was possible to completely reduce the C1C2D (with a combination of axial traction with light extension of the neck on the chest and a light flexion of the head on the neck by using a Mayfield head holder) and proceed to posterior fixation in all the patients under general anaesthesia using a precise "timing sequences fixation technique". Wiring (C0 and C3 were fixed first being stretched up to approximately 10 lbs, then C2 in order to pull up this vertebra last by forcing approximately 8 lbs) or screw fixation methods were used to achieve fusion along with post-operative external orthosis and neuroradiological assessment of the C1C2D. The instrumentation produced a lever and pulley effect which assisted reduction of the dislocation.

FINDINGS

At follow up (range 34-55 months-mean 45.33 months) the clinical picture was improved or stable in all patients.

CONCLUSIONS

Pre-operative irreducibility of the C1C2D should not be an absolute indication for trans-oral decompression. An attempt to reduce the dislocation under general anaesthesia and during posterior fixation should be attempted in Down's syndrome, os odontoideum and rheumatoid arthritis.