Tag: atlantoaxial dislocation

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C2 medial pedicle screw: a novel “in-out-in” technique as an alternative option for posterior C2 fixation in cases with a narrow C2 isthmus

J Neurosurg Spine 33:281–287, 2020

The authors describe a novel “in-out-in” technique as an alternative option for posterior C2 screw fixation in cases that involve narrow C2 isthmus. Here, they report the preliminary radiological and clinical outcomes in 12 patients who had a minimum 12-month follow-up period.

METHODS Twelve patients with basilar invagination and atlantoaxial dislocation underwent atlantoaxial reduction and fixation. All patients had unilateral hypoplasia of the C2 isthmus that prohibited insertion of pedicle screws. A new method, the C2 medial pedicle screw (C2MPS) fixation, was used as an alternative. In this technique, the inner cortex of the narrow C2 isthmus was drilled to obtain space for screw insertion, such that the lateral cortex could be well preserved and the risk of vertebral artery injury could be largely reduced. The C2MPS traveled along the drilled inner cortex into the anterior vertebral body, achieving a 3-column fixation of the axis with multicortical purchase.

RESULTS Satisfactory C2MPS placement and reduction were achieved in all 12 patients. No instance of C2MPS related vertebral artery injury or dural laceration was observed. There were no cases of implant failure, and solid fusion was demonstrated in all patients.

CONCLUSIONS This novel in-out-in technique can provide 3-column rigid fixation of the axis with multicortical purchase. Excellent clinical outcomes with low complication rates were achieved with this technique. When placement of a C2 pedicle screw is not possible due to anatomical constraints, the C2MPS can be considered as an efficient alternative.

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Reduced Field-of-View Diffusion Tensor Imaging of the Spinal Cord Shows Motor Dysfunction of the Lower Extremities in Patients With Cervical Compression Myelopathy

Spine 2018;43:89–96

Study Design. A cross-sectional study.

Objective. The aim of this study was to quantify spinal cord dysfunction at the tract level in patients with cervical compressive myelopathy (CCM) using reduced field-of-view (rFOV) diffusion tensor imaging (DTI).

Summary of Background Data. Although magnetic resonance imaging (MRI) is the standard used for radiological evaluation of CCM, information acquired by MRI does not necessarily reflect the severity of spinal cord disorder. There is a growing interest in developing imaging methods to quantify spinal cord dysfunction. To acquire high-resolution DTI, a new scheme using rFOV has been proposed.

Methods. We enrolled 10 healthy volunteers and 20 patients with CCM in this study. The participants were studied using a 3.0-T MRI system. For DTI acquisitions, diffusion-weighted spinecho rFOV single-shot echo-planar imaging was used. Regions of interest (ROI) for the lateral column (LC) and posterior column (PC) tracts were determined on the basis of a map of fractional anisotropy (FA) of the spinal cord and FA values were measured. The FA of patients with CCM was compared with that of healthy controls and correlated with Japanese Orthopaedic Association (JOA) score.

Results. In LC and PC tracts, FA values in patients with CCM were significantly lower than in healthy volunteers. Total JOA scores correlated moderately with FA in LC and PC tracts. JOA subscores for motor dysfunction of the lower extremities correlated strongly with FA in LC and PC tracts.

Conclusion. It is feasible to evaluate the cervical spinal cord at the tract level using rFOV DTI. Although FA values at the maximum compression level were not well correlated with total JOA scores, they were strongly correlated with JOA subscores for motor dysfunction of the lower extremities. Our findings suggest that FA reflects white matter dysfunction below the maximum compression level and FA can be used as an imaging biomarker of spinal cord dysfunction.

Key words: . Level of Evidence: 4

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Posterior Reduction of Fixed Atlantoaxial Dislocation and Basilar Invagination by Atlantoaxial Facet Joint Release and Fixation

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

Neurosurgery 78:391–400, 2016

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.

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Distraction, Compression, Extension, and Reduction Combined With Joint Remodeling and Extra-articular Distraction: Description of 2 New Modifications for Its Application in Basilar Invagination and Atlantoaxial Dislocation: Prospective Study in 79 Cases

Distraction,_Compression,_Extension,_and_Reduction

Neurosurgery 77:67–80, 2015

Recent strategies for treatment of basilar invagination (BI) and atlantoaxial dislocation (AAD) are based on simultaneous posterior reduction and fixation.

OBJECTIVE: To describe new modifications of the procedure distraction, compression, extension, and reduction (DCER), ie, joint remodeling (JRM) and extra-articular distraction (EAD) in patients with “vertical” joints, and to quantify the improvement in joint indices, ie, sagittal inclination (SI), craniocervical tilt (CCT), and coronal inclination.

METHODS: Prospective study (May 2010 to September 2014). Joint indices measured included (normal values): SI (87.15 ± 5.65º), CCT (60.2 ± 9.2), and coronal inclination (110.3 ± 4.23). Surgical procedures included DCER alone (performed in SI ,100, group I) or JRM with DCER (in SI: 100-160, group II), or EAD with DCER in severe BI with almost vertical joints (SI >160º, group III).

RESULTS: Seventy-nine patients were selected (mean, 22.5 years of age). All conventional indices improved significantly (P < .001). CCT improved in all groups (P < .01); group I (n = 32): 54 ± 8.7 (preoperative 80.71 ± 12.72); group II (n = 40): 58 ± 7.0 (preoperative 86.5 6 14); group III (n = 7): 62 ± 10.0 (preoperative 104 6 11.2). SI improved in both group I and II, P < .01 (cannot be measured in group III). At long-term follow-up (n = 64, 29 ± 8 months, range 12-39 months), the Nurick grade improved to 1.5 ±0.52 (preoperative: 3.4 6 0.65; P < .001).

CONCLUSION: DCER seems to be an effective technique in reducing both BI and AAD. JRM and EAD with DCER are useful in moderate to severe BI and AAD (with SI .100). Joint indices provide useful information for surgical strategy and planning.

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Is atlantoaxial instability the cause of Chiari malformation? Outcome analysis of 65 patients treated by atlantoaxial fixation

Is atlantoaxial instability the cause of Chiari malformation?

J Neurosurg Spine 22:116–127, 2015

Understanding that atlantoaxial instability is the cause of Chiari malformation (CM), the author treated 65 patients using atlantoaxial stabilization. The results are analyzed.

Methods Cases of CM treated using atlantoaxial fixation during the period from January 2010 to November 2013 were reviewed and analyzed. Surgery was aimed at segmental arthrodesis.

Results The author treated 65 patients with CM in the defined study period. Fifty-five patients had associated syringomyelia. Forty-six patients had associated basilar invagination. Thirty-seven patients had both basilar invagination and syringomyelia. Three patients had been treated earlier using foramen magnum decompression and duraplasty. According to the extent of their functional capabilities, patients were divided into 5 clinical grades. On the basis of the type of facetal alignment and atlantoaxial instability, the patients were divided into 3 groups. Type I dislocation (17 patients) was anterior atlantoaxial instability wherein the facet of the atlas was dislocated anterior to the facet of the axis. Type II dislocation (31 patients) was posterior atlantoaxial instability wherein the facet of the atlas was dislocated posterior to the facet of the axis. Type III dislocation (17 patients) was the absence of demonstrable facetal malalignment and was labeled as “central” atlantoaxial dislocation. In 18 patients, dynamic images showed vertical, mobile and at-least partially reducible atlantoaxial dislocation. All patients were treated with atlantoaxial plate and screw fixation using techniques described in 1994 and 2004. Foramen magnum decompression or syrinx manipulation was not performed in any patient. Occipital bone and subaxial spinal elements were not included in the fixation construct. One patient died, and death occurred in the immediate postoperative phase and was related to a vertebral artery injury incurred during the operation. One patient had persistent symptoms. In the rest of the patients there was gratifying clinical improvement. More remarkably, in 7 patients, the symptoms of lower cranial nerve paresis improved. No patient worsened in their neurological function after surgery. Reductions in the size of the syrinx and regression of the CM were observed in 6 of 11 cases in which postoperative MRI was possible. During the follow-up period, there was no delayed worsening of neurological function or symptoms in any patient. Sixty-three patients improved after surgery, and the improvement was sustained during the average follow-up period of 18 months.

Conclusions On the basis of outcomes in this study, it appears that the pathogenesis of CM with or without associated basilar invagination and/or syringomyelia is primarily related to atlantoaxial instability. The data suggest that the surgical treatment in these cases should be directed toward atlantoaxial stabilization and segmental arthrodesis. Except in cases in which there is assimilation of the atlas, inclusion of the occipital bone is neither indicated nor provides optimum stability. Foramen magnum decompression is not necessary and may be counter-effective in the long run.

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Complications of occipitocervical fusion: a 316 cases retrospective analysis

Occipito-cervical fusion

Eur Spine J (2014) 23:1720–1724

Disorders in occipitocervical region are difficult to treat. Complications often occur after fusion surgery and may be life-threatening in severe cases. This study is to investigate the causes and treatment strategies for the postoperative complications of occipitocervical fusion.

Methods Between May 1985 and May 2011, 316 patients with various occipitocervical diseases underwent occipitocervical surgery, with or without internal fixation. Two physicians were assigned for patients follow-up. Their medical records and radiographs were reviewed and the postoperative complications, including those at the occipitocervical region and donor site, were analyzed.

Results Three hundred cases were followed up from 24 months to 26 years with an average of 9 years and 8 months, and the follow-up rate was 94.9 %. There were 16 cases with complications after surgery in the uninstrumented fusion group; the incidence was 33.3 %. These included 11 patients (22.9 %) with complications in occipitocervical region and five patients (11.9 %) with donor-site complications. 45 complications presented in the instrumented fusion group, the incidence was 17.9 %. These included 30 patients (11.9 %) with complications in occipitocervical region and 15 patients (5.9 %) with donorsite complications. Perioperative complications included vertebral artery injury, spinal cord injury, nerve root injury, suffocation, cerebrospinal fluid leakage, and infection. Mid- to long-term complications included bone-graft displacement or absorption, aggravated vertebral dislocation, improper screw placement, spinous process fracture, and internal fixation breakage. Donor-site complications were hematoma, pain and infection.

Conclusion The surgery of occipitocervical fusion carries a relative high risk for complications, especially if no instrumentation is used. The key points in reducing complications are the surgeon’s familiarity with the anatomy of occipitocervical region and the appropriate internal fixation.

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Posterior C1–C2 screw and rod instrument for reduction and fixation of basilar invagination with atlantoaxial dislocation

Basilar invagination with C1-C2 dislocation surgery

Eur Spine J (2014) 23:1666–1672

To report the surgical technique and preliminary clinical results for the treatment of basilar invagination (BI) with atlantoaxial dislocation (AAD) by posterior C1–C2 pedicle screw and rod instrument.

Methods Between July 2012 and August 2013, 33 patients who had BI with AAD underwent surgery at our institution. Pre and postoperative three-dimensional computed tomographic (CT) scans were performed to assess the degree of dislocation. Magnetic resonance (MR) imaging was used to evaluate the compression of the medulla oblongata. For all patients, reduction of the AAD was conducted by two steps: fastening nuts and rods was performed to achieve the horizontal reduction. Distraction between C1 and C2 screws was performed to obtain the vertical reduction.

Results No neurovascular injury occurred during surgery. Follow-up ranged from 6 to 15 months (mean 10.38 months) in 32 patients. Post-operative three-dimensional CT showed that complete horizontal reduction was obtained in 30/33 (90.9 %), and complete vertical reduction was obtained in 31/33 (93.9 %). The repeated threedimensional CT and MR image demonstrated that bony fusion and the decompression of the medulla oblongata were obtained in all patients. Clinical symptoms improved significantly 3 months after surgery.

Conclusions This C1–C2 pedicle screw and rod instrument is a promising technique for the treatment of BI with AAD.

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Surgical Management of Symptomatic Os Odontoideum With Posterior Screw Fixation Performed Using the Magerl and Harms Techniques With Intraoperative 3-Dimensional Fluoroscopy-Based Navigation

Spine 2012 ; 37 : 1839 – 1846

To evaluate the accuracy of screw fixation using intraoperative three-dimensional fluoroscopy-based navigation (ITFN) and to assess the clinical outcomes of this treatment regimen.

Summary of Background Data. The surgical management of symptomatic os odontoideum poses considerable difficulties due to the highly variable anatomy of the upper cervical spine and surrounding neurovascular structures. Various methods have been described for the treatment of symptomatic os odontoideum, all of which have limitations.

Methods. Nineteen patients with symptomatic os odontoideum were investigated. Pain scores were assessed using the visual analogue scale. Myelopathy was assessed using the Nurick scale and Odom’s criteria. Radiological imaging was carried out in all patients for diagnosis and to assess the atlantodens interval, space available for cord, and presence of intramedullary hyperintensity signals on T2-weighted images at the C1–C2 level. Posterior stabilization was performed for all patients by using ITFN.

Results. The mean Nurick score improved from 2.3 before surgery to 0.7 at the time of follow-up. The mean follow-up period was 34.7 months (range, 12–65 mo). According to Odom’s criteria, outcomes were as follows: excellent, 47%; good, 37%; fair, 11%; and poor, 5%. All patients with preoperative neck pain had symptom relief or improvement, with all of these patients having more than 83.7% improvement in visual analogue scale scores. The mean preoperative space available for cord value of 9.3 mm improved to 17.7 mm. Solid fusion and reduction of atlantoaxial dislocation were achieved in every patient without screw failure. Sixty screws were placed in 19 patients. Two C2 polyaxial screws in 2 patients and 1 transarticular screw in 1 patient slightly penetrated the transverse foramen with no vascular injury and clinical sequelae.

Conclusion. ITFN is a safe, accurate, and effective tool for screw placement in patients with symptomatic os odontoideum.

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