Atlanto-axial fusion with transarticular screw fixation

The application of atlantoaxial screw and rod fixation in revision operations for postoperative re-dislocation in children

INTRODUCTION

We evaluate the feasibility, safety, and efficacy of atlantoaxial screw and rod fixation for revision operations in the treatment of re-dislocation after atlantoaxial operations in children.

METHODS

Eight consecutive children with atlantoaxial instability required a revision operation due to atlantoaxial re-dislocation caused by the failure of the initial posterior wire fixation. The children were 5-11 years of age with an average age of 8.5 years. The posterior atlantoaxial screw and rod fixation and fusion operation was then performed. Autograft bones harvested from rib (in 3 patients), local bone (2 patients), and the iliac crest bone (3 patients) were used.

RESULTS

There were no complications such as vertebral artery or spinal cord injury during the operations or loosening or fracture of the fixations after the operations. Stability and reduction of the atlantoaxial segments were achieved in all patients postoperatively. Follow-up time was 24-55 months, with an average of 35 months. All patients achieved solid osseous fusion demonstrated on plain radiographs or CT scanning. Atlantoaxial screw and rod fixation is feasible in children and may be considered for use during the initial operation in the treatment of atlantoaxial dislocation in children to minimize the need for a revision operation.

CONCLUSION

If a revision operation is required, atlantoaxial screw-rod fixation is a safe and effective method. Because the anatomical structure is complicated in revision operation patients, CAD-RP technology could guide the the procedures of exposure and screw placement.

Pooled analysis of non-union, re-operation, infection, and approach related complications after anterior odontoid screw fixation

Background

Anterior odontoid screw fixation (AOSF) has been one of the most popular treatments for odontoid fractures. However, the true efficacy of AOSF remains unclear. In this study, we aimed to provide the pooled rates of non-union, reoperation, infection, and approach related complications after AOSF for odontoid fractures.

Methods

We searched studies that discussed complications after AOSF for type II or type III odontoid fractures. A proportion meta-analysis was done and potential sources of heterogeneity were explored by meta-regression analysis.

Results

Of 972 references initially identified, 63 were eligible for inclusion. 54 studies provided data regarding non-union. The pooled non-union rate was 10% (95% CI: 7%–3%). 48 citations provided re-operation information with a pooled proportion of 5% (95% CI: 3%–7%). Infection was described in 20 studies with an overall rate of 0.2% (95% CI: 0%–1.2%). The main approach related complication is postoperative dysphagia with a pooled rate of 10% (95% CI: 4%–17%). Proportions for the other approach related complications such as postoperative hoarseness (1.2%, 95% CI: 0%–3.7%), esophageal/retropharyngeal injury (0%, 95% CI: 0%–1.1%), wound hematomas (0.2%, 95% CI: 0%–1.8%), and spinal cord injury (0%, 95% CI: 0%–0.2%) were very low. Significant heterogeneities were detected when we combined the rates of non-union, re-operation, and dysphagia. Multivariate meta-regression analysis showed that old age was significantly predictive of non-union. Subgroup comparisons showed significant higher non-union rates in age ≥70 than that in age ≤40 and in age 40 to <50. Meta-regression analysis did not reveal any examined variables influencing the re-operation rate. Meta-regression analysis showed age had a significant effect on the dysphagia rate.

Conclusions/Significances

This study summarized the rates of non-union, reoperation, infection, and approach related complications after AOSF for odontoid factures. Elderly patients were more likely to experience non-union and dysphagia.

Multimodality management of vertebral artery injury sustained during cervical or craniocervical surgery

BACKGROUND

Iatrogenic vertebral artery (VA) injury is a rare but potentially devastating complication associated with cervical and craniocervical surgery.

OBJECTIVE

To retrospectively evaluate treatment modalities and outcomes associated with iatrogenic VA injury.

METHODS

Our institutional surgical database was queried for patients who underwent cervical or craniocervical surgery from January 1997 to August 2012.

RESULTS

During this time period, 8213 patients underwent cervical or craniocervical surgery, and 17 (0.2%) cases of VA injury were identified. Eight (47%) of these injuries occurred during C1-2 instrumentation procedures. Primary microsurgical repair of the VA was performed in 5 patients. Other cases were managed by either surgical or endovascular VA occlusion. Of the 17 patients, 15 underwent immediate angiography, 9 of whom were ultimately treated by the use of endovascular techniques.

CONCLUSION

VA injury is an uncommon complication of cervical and/or skull base surgery. Standardized management recommendations may help reduce complications associated with these rare but potentially devastating injuries.

Tuberculous altantoaxial subluxation: a case report with review of literature

Involvement of upper cervical and craniovertebral junction is rare but might lead to lethal consequences if the diagnosis is delayed. We present a case of atlantoaxial joint tuberculosis, resulting in gross instability of the joint. The patient was treated with antitubercular medication combined with posterior decompression and transarticular screw fixation. Patient improved neurologically, and clinical and radiological improvements were maintained at the latest follow-up of 2 years.

The relationship between an intramedullary high signal intensity and the clinical outcome in atlanto-axial subluxation owing to rheumatoid arthritis

BACKGROUND CONTEXT

In patients affected by cervical spondylotic myelopathy (CSM), numerous authors have reported the existence of a relationship among the intramedullary high signal intensity in T2-weighted MRIs, preoperative neurologic severity, and neurologic recovery after surgery; however, to our knowledge, there have been no previous reports that have described its relationship in patients with atlanto-axial subluxation (AAS) owing to rheumatoid arthritis (RA).

PURPOSE

The purpose of this study was to clarify the characteristics of patients with AAS owing to RA showing intramedullary high signal intensity in T2-weighted MRIs, and to assess the relationship with the neurologic severity and neurologic recovery after surgery.

STUDY DESIGN

This was a retrospective cohort study.

PATIENTS SAMPLE

Fifty consecutive patients (37 females and 13 males) with AAS treated by surgery were reviewed.

OUTCOME MEASURES

The outcome was determined 1 year after surgery.

METHODS

According to preoperative T2-weighted MRIs, the patients were classified into two groups as follows: An NC group not showing any signal intensity change on sagittal images, and an SI group showing signal intensity changes with narrowing of the spinal cord. In all patients, we investigated the atlanto-dental distance (ADD) and the space available for the spinal cord (SAC) at the neutral position and the maximal flexion position in lateral cervical radiographs before surgery. We also observed MRIs 1 year after surgery in the SI group. We evaluated the severity of neurologic symptoms before and 1 year after surgery in all patients.

RESULTS

Preoperative T2-weighted MRIs demonstrated NC in 38 cases and SI in 12 cases. The preoperative average ADD at the neutral position in the NC and SI groups was 6.4 and 10.2 mm, respectively (p<.01). The preoperative ADD at the maximal flexion position in the two groups were 10.8 and 13.8 mm, respectively (p<.01). The preoperative average SAC at the neutral position in the NC and SI groups were 17.6 and 13.8 mm, respectively (p<.01). The SAC at the maximal flexion position in the two groups were 14.3 and 10.8 mm, respectively (p<.01). The SI group included significantly more Ranawat grade III cases showing severe neurologic deficits compared to the NC group (p<.01). However, there were no differences between the two groups regarding the number of patients with Ranawat grade III status after surgery (p>.65). On MRIs 1 year after surgery, the regression or disappearance of the signal intensity change in T2-weighted images was demonstrated in four and seven cases, respectively.

CONCLUSIONS

Preoperative ISHI in T2-weighted MRIs in RA-induced AAS patients was demonstrated in patients showing an enlargement of the ADD and a narrowing of the SAC. This affected the preoperative neurologic severity, but not the postoperative severity, which was in contrast to CSM patients. Furthermore, the regression or disappearance of ISHI was demonstrated in all of the cases after surgery. It is therefore speculated that RA AAS patients may have both dynamic instability and stenosis.

Treatment of Dens Fractures with Posterior Transarticular Fixation

Introduction

Treatment of unstable dens fractures with posterior transarticular C1-C2 arthrodesis provides a biomechanically stable construct, even when poor bone quality is present, and a low rate of complications even in elderly patients; however, when this method of fixation is performed, cervical spine rotation is substantially reduced as compared with that associated with alternative fixation techniques.

Step 1 Positioning

Exact positioning of the patient and use of image intensifiers are mandatory to obtain appropriate anteroposterior and lateral views of C1 and C2.

Step 2 Surgical Approach

Use the modified technique of Magerl and Seemann, as it allows a less extensive approach to C1 and C2, and the drill can enter through two incisions at the level of T1.

Step 3 Insertion of Screws

Use smooth 2.0-mm Kirschner wires to prepare the canal for the screws, and subsequently replace them with 3.0-mm self-tapping screws.

Step 4 Gallie Fusion

Perform a modified Gallie fusion, in addition to the transarticular screw fixation, to increase stability and osseous fusion between C1 and C2.

Step 5 Wound Closure

Perform meticulous closure of the wound to avoid wound-healing complications.

Results

In our original study, we treated twenty-five patients with posterior transarticular fixation.IndicationsContraindicationsPitfalls & Challenges.

Neuronavigation in minimally invasive spine surgery

OBJECT

Parallel advancements in image guidance technology and minimal access techniques continue to push the frontiers of minimally invasive spine surgery (MISS). While traditional intraoperative imaging remains widely used, newer platforms, such as 3D-fluoroscopy, cone-beam CT, and intraoperative CT/MRI, have enabled safer, more accurate instrumentation placement with less radiation exposure to the surgeon. The goal of this work is to provide a review of the current uses of advanced image guidance in MISS.

METHODS

The authors searched PubMed for relevant articles concerning MISS, with particular attention to the use of image-guidance platforms. Pertinent studies published in English were further compiled and characterized into relevant analyses of MISS of the cervical, thoracic, and lumbosacral regions.

RESULTS

Fifty-two studies were included for review. These describe the use of the iso-C system for 3D navigation during C1-2 transarticular screw placement, the use of endoscopic techniques in the cervical spine, and the role of navigation guidance at the occipital-cervical junction. The authors discuss the evolving literature concerning neuronavigation during pedicle screw placement in the thoracic and lumbar spine in the setting of infection, trauma, and deformity surgery and review the use of image guidance in transsacral approaches.

CONCLUSIONS

Refinements in image-guidance technologies and minimal access techniques have converged on spinal pathology, affording patients the ability to undergo safe, accurate operations without the associated morbidities of conventional approaches. While percutaneous transpedicular screw placement is among the most common procedures to benefit from navigation, other areas of spine surgery can benefit from advances in neuronavigation and further growth in the field of image-guided MISS is anticipated.

Computed tomography-based classification of axis vertebra: choice of screw placement

PURPOSE

The purpose of the study was to: (1) introduce a new CT-based parameter: free facet area and provide its normative data; (2) standardize the method of measuring isthmus width and height of the axis vertebra; (3) propose a new grading system to predict the difficulty in inserting transarticular and C2 pedicle screws.

METHODS

Spiral CT scans of 47 adult dry axis vertebrae were studied. The methods of measuring isthmus width, isthmus height and free facet area are described.

RESULTS

The mean isthmus width was 5.04 mm on the right side and 5.42 mm on the left side. The mean isthmus height was 5.21 mm on the right side and 5.45 mm on the left side. Mean free facet area was 61.23 % on the right side and 70.18 % on the left side. A novel grading system is proposed on the basis of these three parameters. As per this grading system, 40.4 % of the sides were found to be difficult for transarticular and 24.5 % sides for C2 pedicle screw insertion (total score 2, 3, 4). A Management protocol is suggested on the basis of the grading system.

CONCLUSION

Inserting a transarticular screw was more frequently difficult as compared to pedicle screw. A new CT-based parameter (free facet area) and an efficient grading have been proposed to help surgeons choose the appropriate screw options, appreciate the complex anatomy of this region and compare data across various studies.

Biomechanical comparison of pedicle screws versus spinous process screws in C2 vertebra: A cadaveric study

BACKGROUND

Biomechanical studies have shown C2 pedicle screw to be the most robust in insertional torque and pullout strength. However, C2 pedicle screw placement is still technically challenging. Smaller C2 pedicles or medial localization of the vertebral artery may preclude safe C2 pedicle screw placement in some patients. The purpose of this study was to compare the pullout strength of spinous process screws with pedicle screws in the C2.

MATERIALS AND METHODS

Eight fresh human cadaveric cervical spine specimens (C2) were harvested and subsequently frozen to -20°C. After being thawed to room temperature, each specimen was debrided of remaining soft tissue and labeled. A customs jig as used to clamp each specimen for screw insertion firmly. Screws were inserted into the vertebral body pairs on each side using one of two methods. The pedicle screws were inserted in usual manner as in previous biomechanical studies. The starting point for spinous process screw insertion was located at the junction of the lamina and the spinous process and the direction of the screw was about 0° caudally in the sagittal plane and about 0° medially in the axial plane. Each vertebrae was held in a customs jig, which was attached to material testing machine (Material Testing System Inc., Changchun, China). A coupling device that fit around the head of the screw was used to pull out each screw at a loading rate of 2 mm/min. The uniaxial load to failure was recorded in Newton'st dependent test (for paired samples) was used to test for significance.

RESULTS

The mean load to failure was 387 N for the special protection scheme and 465 N for the protection scheme without significant difference (t = -0.862, P = 0.403). In all but three instances (38%), the spinous process pullout values exceeded the values for the pedicle screws. The working distances for the spinous process screws was little shorter than pedicle screws in each C2 specimen.

CONCLUSION

Spinous process screws provide comparable pullout strength to pedicle screws of the C2. Spinous process screws may provide an alternative to pedicle screws fixation, especially with unusual anatomy or stripped screws.

Evaluation of biomechanical properties of anterior atlantoaxial transarticular locking plate system using three-dimensional finite element analysis

PURPOSE

To evaluate a new anterior atlantoaxial transarticular locking plate system using finite element analysis.

METHODS

Thin-section spiral computed tomography was performed from occiput to C2 region. A finite element model of an unstable atlantoaxial joint, treated with an anterior atlantoaxial transarticular locking plate system, was compared with the simple anterior atlantoaxial transarticular screw system. Flexion, extension, lateral bending, and axial rotation were imposed on the model. Displacement of the atlantoaxial transarticular screw and stress at the screw-bone interface were observed for the two internal fixation systems.

RESULTS

Screw displacement was less using the anterior atlantoaxial transarticular locking plate system compared to simple anterior atlantoaxial transarticular screw fixation under various conditions, and stability increased especially during flexion and extension.

CONCLUSIONS

The anterior atlantoaxial transarticular locking plate system not only provided stronger fixation, but also decreased screw-bearing stress and screw-bone interface stress compared to simple anterior atlantoaxial transarticular screw fixation.

Minimally invasive anterior transarticular screw fixation and microendoscopic bone graft for atlantoaxial instability

PURPOSE

Even though transarticular screw (TAS) fixation has been commonly used for posterior C1-C2 arthrodesis in both traumatic and non-traumatic lesions, anterior TAS fixation C1-2 is a less invasive technique as compared with posterior TAS which produces significant soft tissue injury, and there were few reports on percutaneous anterior TAS fixation and microendoscopic bone graft for atlantoaxial instability. The goals of our study were to describe and evaluate a new technique for anterior TAS fixation of the atlantoaxial joints for traumatic atlantoaxial instability by analyzing radiographic and clinical outcomes.

METHODS

This was a retrospective study of seven consecutive patients with C1-C2 instability due to upper cervical injury treated by a minimally invasive procedure from May 2007 to August 2009. Bilateral anterior TAS were inserted by the percutaneous approach under Iso-C3D fluoroscopic control. The atlantoaxial joint space was prepared for morselized autogenous bone graft under microendoscopy. The data for analysis included time after the injuries, operating time, intraoperative blood loss, X-ray exposure time, clinical results, and complications. Radiographic evaluation included the assessment of atlantoaxial fusion rate and placement of TAS. Bone fusion of the atlantoaxial joints was assessed by flexion extension lateral radiographs and 1-mm thin-slice computed tomography images as radiographic results. Clinical assessment was done by analyzing the recovery state of clinical presentation from the preoperative period to the last follow-up and by evaluating complications.

RESULTS

A total of 14 screws were placed correctly. The atlantoaxial solid fusion without screw failure was confirmed by CT scan in seven cases after a mean follow-up of 27.5 months (range 18-45 months). All patients with associated clinical presentation made a recovery without neurologic sequelae. Postoperative dysphagia occurred and disappeared in two cases within 5 days after surgery. There were no other complications during the follow-up period.

CONCLUSIONS

Percutaneous anterior TAS fixation and microendoscopic bone graft could be an option for achieving C1-C2 stabilization with several potential advantages such as less tissue trauma and better accuracy. Bilateral TAS fixation and morselized autograft affords effective fixation and solid fusion by a minimally invasive approach.

Effect of a reduction of the atlanto-axial angle on the cranio-cervical and subaxial angles following atlanto-axial arthrodesis in rheumatoid arthritis

PURPOSE

We retrospectively investigated the radiographic findings in patients with atlanto-axial subluxation (AAS) due to rheumatoid arthritis, and clarified the effect of reduction of the atlanto-axial angle (AAA) on the cranio-cervical and subaxial angles.

METHODS

Forty-one patients, consisting of 29 females and 12 males, with AAS treated by surgery were reviewed. The average patient age at surgery was 61.0 years, and the average follow-up period was 4.0 years. We investigated the AAA at the neutral position in lateral cervical radiographs before surgery and at the last follow-up. In addition, we also investigated the clivo-axial angle (CAA) and the subaxial angle (SAA) at the neutral position before and after surgery.

RESULTS

Due to pre-operative AAA, the patients were classified into three groups as follows: (1) the kyphotic group (K group), (2) the neutral group (N group), and (3) the lordotic group (L group). The average AAA values at the neutral position in the K group before and after surgery were 6.0° and 18.1°, respectively (P < 0.001). In the N group 19.7° and 21.7°, respectively (P < 0.05), and in the L group 31.6° and 27.0°, respectively (P < 0.01). However, no significant differences in the average CAA values were found before and after surgery in all groups. Furthermore, no significant differences in the SAA values were seen before and after surgery in all groups.

CONCLUSIONS

A proper reduction of the AAA did not affect the cranial angles or induce kyphotic malalignment of the subaxial region after atlanto-axial arthrodesis. However, if we can obtain a significant and large reduction of AAA in patients showing kyphosis before surgery, then this reduction will be offset in the atlanto-occipital joint and we should therefore pay special attention to its morphology after surgery.

C1-C2 fusion: postoperative C2 nerve impingement-is it a problem?

Objective: The purpose of this comparison case study is to show a potential complication associated with atlantoaxial fusion, and the preoperative evaluation that could help to avoid it.

Background data: The use of lateral mass screw fixation in atlantoaxial fusion has provided surgeons the ability to create rigid fixation, with a high success rate of fusion. While the use of screws for fixation is relatively easy to adopt, the risk of causing neurological damage to the patient is ever present. Many major structures, such as the vertebral artery, carotid artery, and spinal cord, must all be considered during surgery.

Methods: A comparison of two patients who underwent the same procedure was reviewed—the first had no complications from surgery and the second underwent revision surgery because of the C1 screw impinging on the C1 nerve exiting the foramen.

Results: After removal of the C1 screw and converting to a cable technique, the patient made a full recovery and neurological function was restored.

Conclusions: When considering C1-C2 lateral mass screw fixation for atlantoaxial fusion, the size of the foramen should be considered. If the foramen is significantly narrowed, alternate fixation should be selected.

Clinical application of combined fixation in the cervical spine using posterior transfacet screws and pedicle screws

The aim of the present study was to describe the clinical application of combined fixation in the cervical spine using posterior transfacet and pedicle screws. Ten patients with cervical disorders requiring stabilization were treated from May 2006 to December 2008. The operative details varied depending on indication, the need for decompression, and the number of levels to be included in the spinal construct. Radiographic analysis of the fusion was performed after surgery. A total of 23 transfacet screws were inserted at or caudal to the C4/5 facet. A total of 21 pedicle screws were placed. All patients underwent operative treatment without neurovascular complications. Fusion was achieved in all patients. When performed appropriately, the method of using posterior transfacet screws in the caudal cervical joints combined with pedicle screw fixation in the cephalic cervical spine is reliable and deserves more widespread use.

Is inclusion of the occiput necessary in fusion for C1-2 instability in rheumatoid arthritis?

OBJECT

The atlantoaxial joint is the location most and earliest affected in patients with rheumatoid arthritis (RA). In longstanding disease, ligamentous and osseous destruction can progress and involve all cervical segments. If surgical intervention is necessary, some prefer, to be safe, undertaking fusion to the occiput, whereas others advocate 1-level fusion of C1-2. Sparing the occiput (Oc)-C1 segment would allow retention of a considerable amount of physiological range of motion and seems beneficial against subaxial overload. Previous clinical studies on this topic have provided only nonspecific data after short-term follow-up, rendering a segment-sparing approach questionable. The purpose of the present investigation was to assess long-term progression of inflammatory or degenerative destruction in the Oc-C1 segment after isolated C1-2 fusion for RA.

METHODS

In a series of 113 consecutive patients with RA-related destruction restricted to the craniocervical junction, 14 individuals underwent Oc-C2 fusion and 99 underwent surgery exclusively at the C1-2 level. After a mean follow-up period of 9.4 years (range 4.9-14.7 years), 46 patients were available for clinical and radiographic examination, including CT imaging.

RESULTS

None of the 46 patients needed additional surgery to extend the fusion to the occiput. Despite marked deterioration in the subaxial cervical spine, in general there were little or no changes in the atlantooccipital region. All but one patient presented with bony fusion of the fixed C1-2 level at follow-up.

CONCLUSIONS

The results of this investigation suggest that if the Oc-C1 joint is free of osseous destructions on conventional radiographs and free of abnormalities on MRI scans at the time of surgery (for transarticular fixation and fusion of C1-2), there is a very low risk for relevant destruction in the following 5-14 years. Thus, no prophylactic oligosegmental approach, but rather a segment-sparing monosegmental approach, is preferred, even in patients with high inflammatory levels.

Outcomes of fusion for lateral atlantoaxial osteoarthritis: meta-analysis and review of literature

OBJECTIVE

Atlantoaxial osteoarthritis (AAOA) is an underrecognized source of neck pain, limitation of range of motion, and cervicogenic headaches. When conservative treatments such as facet injections fail, fusion may be indicated. We reviewed published series describing posterior fusions for atlantoaxial osteoarthritis of the facet joints.

METHODS

Online databases were searched for English-language articles describing the diagnosis and treatment of AAOA. Twenty-three studies reporting on 246 patients treated with posterior fusion for lateral AAOA fulfilled inclusion criteria. Standard statistical and formal meta-analytic techniques were used to assess outcomes.

RESULTS

All studies provided class III evidence. The 30-day perioperative mortality was 1.2% and neurologic injury did not occur. Patients were followed for a mean of nearly 5 years. Fusion was successful in 98% of patients with a single operation and with 99.5% of patients after revision surgery. Intractable preoperative neck pain either resolved completely or improved in 97.7% of patients. Using meta-analytic techniques, the point estimate for improvement or resolution of pain was 92.6% (confidence interval = 86.8%-96.0%) and the rate of arthrodesis for AAOA was 92.2% (confidence interval = 85.6%-95.9%) and there were no differences among the various techniques used for fusion. Operative complications were few.

CONCLUSIONS

Posterior C1-2 fusion is a safe and effective treatment option for patients with intractable neck pain secondary to lateral AAOA. Modern fusion options offer a high rate of arthrodesis and low risk of morbidity if conservative therapies fail to provide adequate pain relief.

Posterior cervical fixation with a nitinol shape memory loop for primary surgical stabilization of atlantoaxial instability: a preliminary report

Objective

To evaluate a new posterior atlantoaxial fixation technique using a nitinol shape memory loop as a simple method that avoids the risk of vertebral artery or nerve injury.

Methods

We retrospectively evaluated 14 patients with atlantoaxial instability who had undergone posterior C1-2 fusion using a nitinol shape memory loop. The success of fusion was determined clinically and radiologically. We reviewed patients' neurologic outcomes, neck disability index (NDI), solid bone fusion on cervical spine films, changes in posterior atlantodental interval (PADI), and surgical complications.

Results

Solid bone fusion was documented radiologically in all cases, and PADI increased after surgery (p<0.05). All patients remained neurologically intact and showed improvement in NDI score (p<0.05). There were no surgical complications such as neural tissue or vertebral artery injury or instrument failure in the follow-up period.

Conclusion

Posterior C1-2 fixation with a nitinol shape memory loop is a simple, less technically demanding method compared to the conventional technique and may avoid the instrument-related complications of posterior C1-2 screw and rod fixation. We introduce this technique as one of the treatment options for atlantoaxial instability.

Biomechanical analysis of a novel hook-screw technique for C1–2 stabilization

The Food and Drug Administration has not cleared the following medical devices for the use described in this study. The following medical devices are being discussed for an off-label use: cervical lateral mass screws.

Object

As an alternative for cases in which the anatomy and spatial relationship between C-2 and a vertebral artery precludes insertion of C-2 pedicle/pars or C1–2 transarticular screws, a technique that includes opposing laminar hooks (claw) at C-2 combined with C-1 lateral mass screws may be used. The biomechanical stability of this alternate technique was compared with that of a standard screw-rod technique in vitro.

Methods

Flexibility tests were performed in 7 specimens (occiput to C-3) in the following 6 different conditions: 1) intact; 2) after creating instability and attaching a posterior cable/graft at C1–2; 3) after removing the graft and attaching a construct comprising C-1 lateral mass screws and C-2 laminar claws; 4) after reattaching the posterior cable-graft at C1–2 (posterior hardware still in place); 5) after removing the posterior cable-graft and laminar hooks and placing C-2 pedicle screws interconnected to C-1 lateral mass screws via rod; and 6) after reattaching the posterior cable-graft at C1–2 (screw-rod construct still in place).

Results

All types of stabilization significantly reduced the range of motion, lax zone, and stiff zone compared with the intact condition. There was no significant biomechanical difference in terms of range of motion or lax zone between the screw-rod construct and the screw-claw-rod construct in any direction of loading.

Conclusions

The screw-claw-rod technique restricts motion much like the standard Harms technique, making it an acceptable alternative technique when aberrant arterial anatomy precludes the placement of C-2 pars/pedicle screws or C1–2 transarticular screws.

Posterior atalntoaxial fusion with c1 lateral mass screw and c2 pedicle screw supplemented with miniplate fixation for interlaminar fusion : a preliminary report

OBJECTIVE

To investigate the feasibility of C1 lateral mass screw and C2 pedicle screw with polyaxial screw and rod system supplemented with miniplate for interlaminar fusion to treat various atlantoaxial instabilities.

METHODS

After posterior atlantoaxial fixation with lateral mass screw in the atlas and pedicle screw in the axis, we used 2 miniplates to fixate interlaminar iliac bone graft instead of sublaminar wiring. We performed this procedure in thirteen patients who had atlantoaxial instabilities and retrospectively evaluated the bone fusion rate and complications.

RESULTS

By using this method, we have achieved excellent bone fusion comparing with the result of other methods without any complications related to this procedure.

CONCLUSION

C1 lateral mass screw and C2 pedicle screw with polyaxial screw and rod system supplemented with miniplate for interlaminar fusion may be an efficient alternative method to treat various atlantoaxial instabilities.

Posterior cervical spine arthrodesis incorporating C2 laminar screw fixation in the treatment of cervical spine injury

OBJECTIVE

To investigate the clinical application and efficacy of an internal fixation technique incorporating C(2) laminar screws for upper cervical spine injury.

METHODS

Using a posterior cervical approach, incorporating C(2) laminar screw fixation and bone grafting were performed on 20 patients with cervical spine injury. There were 12 male and 8 female patients, with a mean age of 45.6 years (range, 32-71 years). All patients were evaluated by X-ray, computed tomography (CT) and magnetic resonance imaging (MRI).

RESULTS

The patients were followed up for 11-35 months (mean, 15 months), and bony union was achieved in all patients. There were no spinal cord or vertebral artery injuries during surgery, and only two instances of vein clump injury, in both of which the bleeding was controlled successfully. Postoperative CT scans showed that all the C(2) laminar screws had been placed properly, and were not encroaching on the spinal canal. No spinal instability, evidence of hardware failure or screw loosening was found during the follow-up period in any patient.

CONCLUSION

Crossing C(2) laminar screw internal fixation technique is simple, and is not limited by the position of the vertebral artery in the body of C(2). The laminar screw method avoids arterial injuries and also can be used as a salvage method after previous misinsertion. As all relevant structures are directly visualized during C(2) laminar screw placement, this kind of technique may be applicable to a large number of patients.

Characteristics of idiopathic atlanto-axial subluxation: a comparative radiographic study in patients with an idiopathic etiology and those with rheumatoid arthritis

OBJECTIVE

Atlanto-axial subluxation (AAS) is caused by multiple conditions; however, idiopathic AAS patients without RA, upper-cervical spine anomalies or any other disorder are rarely encountered. This study retrospectively investigated the radiographic findings in idiopathic AAS patients, and clarified the differences between those AAS patients and those due to RA.

METHODS

Fifty-three patients with AAS treated by transarticular screw fixation were reviewed. The subjects included 8 idiopathic patients (ID group) and 45 RA patients (RA group). The study investigated the atlanto-dental interval (ADI) value and space available for spinal cord (SAC) at the neutral and maximal flexion position.

RESULTS

The average ADI value at the neutral position in the ID and RA groups before surgery was 7.8 and 7.2 mm, respectively (p > 0.74). The average ADI value at the flexion position in the two groups was 10.3 and 11.7 mm, respectively (p > 0.06). The average SAC value at the neutral position in the two groups was 12.0 and 17.1 mm, respectively (p < 0.01). Finally, the average SAC value at the flexion position in the two groups was 10.7 and 13.5 mm, respectively (p < 0.01).

CONCLUSIONS

The SAC value at both the neutral and flexion positions in idiopathic AAS patients was significantly smaller than those values in RA-AAS patients. This may be because the narrowing of the SAC in the idiopathic group easily induces cervical myelopathy. Furthermore, surgery was often recommended to RA patients, because of the neck pain induced by RA-related inflammation of the atlanto-axial joint, regardless of any underlying myelopathy.

Comparison of the anatomic risk for vertebral artery injury associated with percutaneous atlantoaxial anterior and posterior transarticular screws

BACKGROUND CONTEXT

As a minimally invasive spine surgery, percutaneous atlantoaxial fixation techniques using anterior transarticular screw (ATS) and posterior transarticular screw (PTS) have promising clinical results. However, transarticular screw fixation is technically demanding and carries a potential risk of iatrogenic vertebral artery (VA) injury. There were no available data comparing the anatomic risk of VA injury associated with these screws.

PURPOSE

To evaluate the trajectories of percutaneous atlantoaxial ATS and PTS through three-dimensional (3D) computerized tomography.

STUDY DESIGN

To compare the anatomic risk of VA injury between percutaneous ATS and PTS.

PATIENT SAMPLE

Sixty patients ranged in age from 19 to 75 years (mean, 45.08 years) and included 35 men and 25 women.

OUTCOME MEASURES

Image measurement of C2 isthmus height and C2 isthmus width and the distance between the medial-most superior articular facet to the medial-most edge of the VA groove of the C2 (D).

METHODS

Sixty consecutive patients (in total) with lower cervical lesions were evaluated through 3D images reconstructed by a rapid 3D system. The maximum possible diameters of the percutaneous atlantoaxial ATS and PTS trajectories were compared and examined. Mean, range, and standard deviations for each type of screw, for left and right trajectories, and for men and women were calculated from 120 percutaneous atlantoaxial ATS and PTS measurements through SPSS.

RESULTS

The maximum mean diameter differed significantly between the trajectories of 120 percutaneous atlantoaxial ATS and PTS. For screw trajectories ≤3.5 mm in diameter, 19.2% of the PTS trajectories were judged as risky, whereas all the anterior ones were judged as safe.

CONCLUSIONS

From an anatomic perspective, percutaneous ATS fixation poses less anatomic risk of VA injury than percutaneous PTS fixation. As an alternative surgical therapy for atlantoaxial subluxation, percutaneous ATS fixation may play a more important role in the future.

[Odontoid fracture: Long-term subarachnoid hemorrhage after anterior screw fixation. Case report and literature review]

Odontoid fractures have been classified by Anderson and D'Alonzo into three main categories. The most unstable injuries, type II fractures involve the base of the odontoid peg at the junction with the C2 body. Due to the proximity of vital neural structures, fracture of the odontoid process may result in instability and fatal neurological damage. Treatment aims to re-establish stability of the atlanto-axial complex by restoring the odontoid process. This may be achieved by conservative or surgical treatment. Anterior screw fixation of the odontoid peg is an interresting alternative surgical option but this technique has a significant complication rate. However, vascular injury is very rare with three case reported in the literature: one case of an intracranial vertebral artery (VA) injury, one case of a cervical internal carotid artery (ICA) injury and one case of anterior pseudoaneurysm of the spinal artery branch. We report a new case of long term vascular injury after screw fixation revealed by a subarachnoid hemorrhage. We discuss the incidence, the mechanisms of injury and the conditions necessary for the occurrence of this complication.

Is external cervical orthotic bracing necessary after posterior atlantoaxial fusion with modern instrumentation: meta-analysis and review of literature

BACKGROUND

No guidelines exist regarding external cervical orthoses (ECO) after atlantoaxial fusion. We reviewed published series describing C1-2 posterior instrumented fusions with screw-rod constructs (SRC) or transarticular screws (TAS) and compared rates of fusion with and without postoperative ECO.

METHODS

Online databases were searched for English-language articles between 1986 and April 2011 describing ECO use after posterior atlantoaxial instrumentation with SRC or TAS. Eighteen studies describing 947 patients who had SRC (± ECO: 254 of 693 patients), and 33 studies describing 1424 patients with TAS (± ECO: 525 of 899 patients) met inclusion criteria. Meta-analysis techniques were applied to estimate rates of fusion with and without ECO use.

RESULTS

All studies provided class III evidence, and no studies directly compared outcomes with or without ECO use. There was no significant difference in the proportion of patients who achieved successful fusion between patients treated with ECO and without ECO for SRC or TAS patients. Point estimates and 95% confidence intervals (CI) for rates of fusion ± ECO were 97.4% (CI: 95.2% to 98.6%) versus 97.9% (CI: 93.6% to 99.3%) for SRC and 93.6% (CI: 90.7% to 95.6%) versus 95.3% (CI: 90.8% to 97.7%) for TAS. There was no correlation between duration of ECO treatment and fusion (dose effect).

CONCLUSIONS

After C1-2 fusion with modern instrumentation, ECO may be unnecessary (class III). Some centers recommend ECO use with patients with softer bone quality (class IV). Prospective, randomized studies with validated radiographic and clinical outcome metrics are necessary to determine the utility of ECO after C1-2 fusion and its impact on patient comfort and cost.

Atlantoaxial fusion with transarticular screws: meta-analysis and review of the literature

OBJECTIVE

To review published series describing C1-2 posterior instrumented fusions and summarize clinical and radiographic outcomes of patients treated with transarticular screw (TAS) fixation.

METHODS

Online databases were searched for English-language articles published between 1986 and April 2011 describing posterior atlantoaxial instrumentation with C1-2 TAS fixation. There were 45 studies including 2073 patients treated with TAS that fulfilled inclusion criteria. Meta-analysis techniques were used to calculate outcomes.

RESULTS

All studies provided class III evidence. The 30-day perioperative mortality rate was 0.8%, and the incidence of neurologic injury was 0.2%. The incidence of clinically significant malpositioned screws was 7.1% (confidence interval [CI], 5.7%-8.8%), the incidence of vertebral artery injury was 3.1% (CI, 2.3%-4.3%), and the rate of fusion with the TAS technique was 94.6% (CI, 92.6%-96.1%).

CONCLUSIONS

TAS fixation is a safe and effective treatment option for C1-2 instability with high rates of fusion (approximately 95%). Screw malposition and vertebral artery injury occurred in approximately 5% of patients. The successful insertion of TAS requires a thorough knowledge of atlantoaxial anatomy.

Biomechanical investigation of a novel integrated device for intra-articular stabilization of the C1-C2 (atlantoaxial) joint

BACKGROUND CONTEXT

The anatomy of the atlantoaxial joint makes stabilization at this level challenging. Current techniques that use transarticular screw fixation (Magerl) or segmental screw fixation (Harms) give dramatically improved stability but risk damage to the vertebral artery. A novel integrated device was designed and developed to obtain intra-articular stabilization via primary interference fixation within the C1-C2 lateral mass articulation.

PURPOSE

To assess the atlantoaxial stability achieved with a novel integrated device when compared with the intact, destabilized, and stabilized state using the Harms technique.

STUDY DESIGN

A biomechanical study of implants in human cadaveric cervical spines.

METHODS

Six human cadaveric specimens were used. Biomechanical testing was performed with moment control in flexion-extension, lateral bending, and axial rotation. Range of motion (ROM) was measured in the intact state, after both destabilization by creation of a Type II odontoid peg fracture and sequential stabilization using the integrated device and the Harms technique.

RESULTS

Mean flexion-extension ROM of the intact specimens at C1-C2 was 14.1°±2.9°. Destabilization increased the ROM to 31.6°±4.6°. Instrumentation with the Harms technique reduced flexion-extension motion to 4.0°±1.4° (p<.01). The integrated device reduced flexion-extension motion to 3.6°±1.8° (p<.01). In lateral bending, the respective mean angular motions were 1.8°±1.1°, 14.1°±5.8°, 1.4°±0.7°, and 0.4°±0.3° for the intact destabilized Harms technique and integrated device. For axial rotation, the respective mean values were 67.3°±13.8°, 74.2°±16.1°, 1.4°±0.7° and 0.9°±0.7°. Both the Harms technique and integrated device significantly reduced motion compared with the destabilized spine in flexion-extension, lateral bending, and axial rotation (p<.05). Direct comparison of the Harms technique and the integrated device revealed no significant difference (p>.10).

CONCLUSIONS

The integrated device resulted in interference fixation at the C1-C2 lateral mass joints with comparable stability to the Harms technique. Perceived advantages with the integrated device include avoidance of fixation below the C2 lateral mass where the vertebral artery is susceptible to injury, and access to the C1 screw entry point through the blade of the integrated device avoiding extended dissection superior to the C2 nerve root and its surrounding venous plexus.

C1-C2 posterior fixation: indications, technique, and results

The atlantoaxial motion segment, which is responsible for half of the rotational motion in the cervical spine, is a complex junction of the first (C1) and second (C2) cervical vertebrae. Destabilization of this joint is multifactorial and can lead to pathologic motion with neurologic sequelae. Posterior spinal fixation of the C1-C2 articulation in the presence of instability has been well described in the literature. Early reports of interspinous/interlaminar wiring have evolved into modern-day pedicle screw/translaminar constructs, with excellent results. The success of a C1-C2 posterior fusion rests on appropriate indications and surgical techniques.

Occipitocervical fusion in elderly patients

BACKGROUND

Occipitocervical disease (OCD) in elderly patients will become increasingly common as the population ages. Our experience with occipitocervical fusions (OCF) in this population suggests mixed outcomes.

METHODS

Twenty consecutive patients over 65 years old underwent OCF between 1995 and 2005. A retrospective review of demographic, presentation, surgical and outcome data was performed.

RESULTS

Twenty patients averaging 75.3 years of age (range 65 to 91) were identified. All patients had evidence of myelopathy; however, the primary surgical indications were progressive spinal cord dysfunction (15), brainstem compression (3), and pain (2). Surgical approach was isolated posterior (9), or anterior transoral odontoidectomy followed by posterior stabilization (11). Overall, surgery improved function modestly; average modified Japanese Orthopedic Association functional score (improved 0.9 grades), average Ranawat Myelopathy Score (improved 0.4 grades), and average Nurick Myelopathy Grade (improved 0.6 grades). However, patients with poor preoperative functional assessment (Ranawat grade ≥ III) had greater neurologic improvement than those with good preoperative function, measured by Nurick grade improvement (1 vs. -0.28; P = .03) and Ranawat grade improvement (0.7 vs. -0.2; P = .03). Additionally, the posterior approach demonstrated significant improvement in Japanese Orthopedic Association functional assessment over patients with anterior/posterior approaches (2.2 vs. -0.3; P = .03), with fewer complications (posterior: 1 minor; anterior/posterior: 1 death, 2 major, 8 minor). Perioperative mortality occurred in 5%, and major morbidity in 10% of patients.

CONCLUSIONS

Preventing or stabilizing neurologic deficit in patients with OCD may require OCF, despite the patient's age. In the elderly population, our data favor using the posterior approach when possible, and demonstrate greater neurologic improvement in patients with poor preoperative function.

C-2 neurectomy during atlantoaxial instrumented fusion in the elderly: patient satisfaction and surgical outcome

Object

The originally described technique of atlantoaxial stabilization using C-1 lateral mass and C-2 pars screws includes a C-2 neurectomy to provide adequate hemostasis and visualization for screw placement, enable adequate joint decortication and arthrodesis, and prevent new-onset postoperative C-2 neuralgia. However, inclusion of a C-2 neurectomy for this procedure remains controversial, likely due in part to a lack of studies that have specifically addressed whether it affects patient outcome. The authors' objective was to assess the surgical and clinical impact of routine C-2 neurectomy performed with C1–2 segmental instrumented arthrodesis in a consecutive series of elderly patients with C1–2 instability.

Methods

Forty-four consecutive patients (mean age 71 years) underwent C1–2 instrumented fusion, including C-1 lateral mass screw insertion. Bilateral C-2 neurectomies were performed. Standardized clinical assessments were performed both pre- and postoperatively. Numbness or discomfort in a C-2 distribution was documented at follow-up. Fusion was assessed using the Lenke fusion grade.

Results

Among all 44 patients, mean blood loss was 200 ml (range 100–350 ml) and mean operative time was 129 minutes (range 87–240 minutes). There were no intraoperative complications, and no patients reported new postoperative onset or worsening of C-2 neuralgia postoperatively. Outcomes for the 30 patients with a minimum 13-month follow-up (range 13–72 months) were assessed. At a mean follow-up of 36 months, Nurick grade and pain numeric rating scale scores improved from 3.7 to 1.0 (p < 0.001) and 9.4 to 0.6 (p < 0.001), respectively. The mean postoperative Neck Disability Index score was 7.3%. The fusion rate was 97%, and the patient satisfaction rate was 93%. All 24 patients with preoperative occipital neuralgia reported relief. Seventeen patients noticed C-2 distribution numbness only during examination in the clinic, and 2 patients reported C-2 numbness, but it did not affect their daily function.

Conclusions

In this series of C1–2 instrumented arthrodesis in elderly patients, excellent fusion rates were achieved, and patient satisfaction was not negatively affected by C-2 neurectomy. In the authors' experience, C-2 neurectomy enhanced surgical exposure of the C1–2 joint, thereby facilitating hemostasis, placement of instrumentation, and decortication of the joint space for arthrodesis. Importantly, with C-2 neurectomy in the present series, no cases of new onset postoperative C-2 neuralgia occurred, in contrast to a growing number of reports in the literature documenting new-onset C-2 neuralgia without C-2 neurectomy. On the contrary, 80% of patients in the present series had preoperative occipital neuralgia and in all of these patients this neuralgia was relieved following C1–2 instrumented arthrodesis with C-2 neurectomy.

Is intraoperative CT of posterior cervical spine instrumentation cost-effective and does it reduce complications?

BACKGROUND

Symptomatic multilevel cervical myelopathy is often addressed using posterior decompression using two-dimensional fluoroscopy. Intraoperative three-dimensional fluoroscopy provides more accurate information on the position of instrumentation to prevent screw-related complications.

QUESTIONS/PURPOSES

We documented the incidence of hardware-related complications and evaluate cost-effectiveness when using intraoperative three-dimensional fluoroscopy (ISO-C CT) in posterior cervical spine surgery.

METHODS

Records from 87 patients who underwent posterior cervical decompression and instrumented fusion for multilevel cervical spondylosis with myelopathy were retrospectively reviewed. Patients in whom a lateral mass, pars, or pedicle screw was removed or revised based on intraoperative ISO-C CT was recorded. Cost analysis was performed using 2008 Medicare reimbursements and was compared against cost estimates for ISO-C CT.

RESULTS

Seven patients (8%) had screws changed based on the results of the three-dimensional fluoroscopy: 0.5% of lateral mass screws, 3.1% of thoracic pedicle screws, and 15% of C2 pars screws. No patients who had evaluation of hardware with the ISO-C CT required a return to surgery for complications secondary to hardware failure, malposition, or cutout.

CONCLUSIONS

Cost savings are achieved if use of intraoperative ISO-C CT prevents eight patients from requiring a return to the operating room. If every malpositioned screw has the potential to be symptomatic, then 240 patients must have screws placed to be cost-effective. ISO-C CT can safely replace postoperative CT as the standard of care in patients undergoing posterior cervical spinal fusion.

LEVEL OF EVIDENCE

Level III, economic and decision analyses. See Guidelines for Authors for a complete description of levels of evidence.

Artrodesis C1C2 con tornillos transarticulares en artritis reumatoidea: experiencia y revisión de la literatura

OBJETIVO: Describir los resultados clínicos e imagenológicos utilizando la técnica de fijación C1 C2 con tornillos transarticulares y asas de alambre en pacientes portadores de AR en un seguimiento a largo plazo y revisar la literatura actual. MÉTODO: Entre los años 2002 y 2006, 11 pacientes (9 mujeres y 2 hombres) con inestabilidad C1 C2 secundaria a AR fueron intervenidos quirúrgicamente. Se realizó fijación C1 C2 con tornillos transarticulares por vía posterior más asas de alambre y aplicación de injerto óseo autólogo de cresta ilíaca. Se registró Índice de Ranawat pre y posoperatorio, Distancia Anterior Atlas Odontoides (DAAO) pre y posoperatorio, tiempo operatorio, días de hospitalización, complicaciones intra y posoperatorias y tiempo de consolidación radiológica, con un seguimiento promedio de 34 meses. RESULTADOS: Todos los pacientes presentaron mejoría del Índice de Ranawat en el postoperatorio. La DAAO preoperatoria promedio fue de 11,9 mm (DS ± 2,57), rango 7 a 16, y la DAAO postoperatoria promedio fue de 3 mm (DS ± 1,20), rango 2 a 6. El tiempo quirúrgico fue de 94 minutos en promedio y el promedio de días de hospitalización fue de 7 días. No se presentaron complicaciones intraoperatorias. Un caso presentó seroma de herida operatoria que requirió tratamiento quirúrgico. El tiempo de consolidación fue en promedio 14 semanas. CONCLUSIÓN: La artrodesis atlantoaxial con tornillos y amarras es una buena alternativa para el manejo de la inestabilidad C1-C2 en pacientes portadores de AR, consiguiendo buenos resultados clínicos e imagenológicos en un seguimiento a largo plazo.

C2 translaminar screw as the optimal choice for atlantoaxial dislocation with C2-C3 congenital fusion

OBJECTIVE AND IMPORTANCE

The entry point and trajectory are very important for transarticular screw (TAS) and C2 pedicle screw (PDS) plantation. When the physical size is not large enough for the screw passing through, an accurate entry point is the most important point for successful screw insertion without vertebral artery (VA) injury and spinal cord injury. Once the laminas of C2 and C3 are fused, the normal anatomic mark might disappear and the insertion point would be hard to find. As a result, the complication of TAS or PDS implantation increases rapidly. We used C2 translaminar screws (TLSs) with C1 lateral mass screws as the optimal fixation for atlantoaxial dislocation in order to reduce the risk of VA injury and spinal cord injury.

CLINICAL PRESENTATION

A 37-year-old woman with atlantoaxial dislocation due to obsolete odontoid fracture complained of neck pain and myelopathy. Preoperative CT reconstruction showed C2-C3 fusion and small size of C2 isthmus.

TECHNIQUE

The patient underwent posterior atlantoaxial fusion using C1 lateral mass screws and C2 TLSs. The posterior arch of atlas was removed for decompression and fusion was done at C1-C2 joints by grafting bone fragments from the posterior iliac crest.

CONCLUSION

TLSs combined with C1 lateral mass screws might be a useful technique for patients with atlantoaxial dislocation and C2-C3 fusion, especially with small size of C2 isthmus. Also, the fusion of posterior elements between C2 and C3 might be a relative contraindication for TAS fixation.

Transarticular screw fixation for atlantoaxial instability - modified Magerl's technique in 38 patients

BACKGROUND

Symptomatic atlantoaxial instability needs stabilization of the atlantoaxial joint. Among the various techniques described in literature for the fixation of atlantoaxial joint, Magerl's technique of transarticular screw fixation remains the gold standard. Traditionally this technique combines placement of transarticular screws and posterior wiring construct. The aim of this study is to evaluate clinical and radiological outcomes in subjects of atlantoaxial instability who were operated using transarticular screws and iliac crest bone graft, without the use of sublaminar wiring (a modification of Magerl's technique).

METHODS

We evaluated retrospectively 38 subjects with atlantoaxial instability who were operated at our institute using transarticular screw fixation. The subjects were followed up for pain, fusion rates, neurological status and radiographic outcomes. Final outcome was graded both subjectively and objectively, using the scoring system given by Grob et al.

RESULTS

Instability in 34 subjects was secondary to trauma, in 3 due to rheumatoid arthritis and 1 had tuberculosis. Neurological deficit was present in 17 subjects. Most common presenting symptom was neck pain, present in 35 of the 38 subjects.Postoperatively residual neck and occipital pain was present in 8 subjects. Neurological deficit persisted in only 7 subjects. Vertebral artery injury was seen in 3 subjects. None of these subjects had any sign of neurological deficit or vertebral insufficiency. Three cases had nonunion. At the latest follow up, subjectively, 24 subjects had good result, 6 had fair and 8 had bad result. On objective grading, 24 had good result, 11 had fair and 3 had bad result. The mean follow up duration was 41 months.

CONCLUSIONS

Transarticular screw fixation is an excellent technique for fusion of the atlantoaxial complex. It provides highest fusion rates, and is particularly important in subjects at risk for nonunion. Omitting the posterior wiring construct that has been used along with the bone graft in the traditional Magerl' s technique achieves equally good fusion rates and is an important modification, thereby avoiding the complications of sublaminar wire passage.

Bilateral atlantoaxial transarticular screws and atlas laminar hooks fixation for pediatric atlantoaxial instability

STUDY DESIGN

An atlantoaxial fixation using bilateral C1-C2 transarticular screws and C1 laminar hooks was used in 5 pediatric patients, who were then followed up for 12 to 17 months to evaluate the technique.

OBJECTIVE

To describe a modified posterior C1-C2 fixation technique and preliminary clinical and radiographic results in 5 pediatric patients.

SUMMARY OF BACKGROUND DATA

Conventional posterior atlantoaxial fixations, such as Gallie and Brooks techniques, are frequently associated with high rates of pseudarthrosis and implant failure. The C1-C2 transarticular screw fixation has been shown to be effective in treatment of pediatric atlantoaxial instability, as well as adult atlantoaxial instability; however, this 2-point fixation merely stabilizes the atlantoaxial motion segment laterally. A 3-point fixation, composed with bilateral C1-C2 transarticular screws and C1 laminar hooks, has been developed.

METHODS

Five patients with atlantoaxial instability, including 4 males and 1 female, aged 6 to 17 (average 10) years, underwent atlantoaxial fixation using bilateral C1-C2 transarticular screws and C1 laminar hooks during a 2-year period. The surgical technique and treatment procedures were intensively reviewed, and clinical symptoms and imaging appearance were retrospectively evaluated.

RESULTS

Clinical follow-ups were obtained for an average of 14.4 (range: 12-17) months. The clinical and radiologic follow-up indicated a stable arthrodesis and offered clinical relief from symptoms for all patients. No neural or vascular impairment related to this technique was observed.

CONCLUSION

Fixation of the atlantoaxial articulation using bilateral C1-C2 transarticular screws and C1 laminar hooks appears to be a reliable technique for treatment of pediatric atlantoaxial instability.

C1 lateral mass screw insertion with protection of C1-C2 venous sinus: technical note and review of the literature

STUDY DESIGN

This is a technical note and review of the literature.

OBJECTIVE

We propose to describe a revised surgical technique of C1 lateral mass screw insertion with protection of C1-C2 venous sinus surrounding the C2 nerve root.

SUMMARY OF BACKGROUND DATA

During C1 lateral mass screw insertion and in posterior C1-C2 fixation, iatrogenic injury of C1-C2 venous sinus results in bleeding, which is troublesome. Appropriate management of the venous sinus in this region is critical to successful surgery in this complex anatomic region.

METHODS

We reviewed 48 patients who underwent posterior C1-C2 fixation at our institution between September 2001 and October 2008. Twenty-four atlas screws were inserted by the originally described C1 lateral mass screw technique (group A), and 28 through a revised posterior arch and lateral mass screw technique (C1 transpedicular screw) (group B). The final group of 44 atlas screws was placed with our newly revised technique (group C).

RESULTS

Bleeding of venous sinus was encountered in 3 group A, 2 group B, and 1 group C atlas screw insertions. The incidence rate was 12.50% (A), 7.14% (B), and 2.27% (C). Statistical comparison showed no significant difference between the groups. All the cases were followed for a mean period of 28.1 month. Four patients in group A complained of postoperative numbness in occipitocervical region. No patients in group B or group C voiced this complaint. A high fusion rate was found in all 3 groups with no signs of implant failure.

CONCLUSION

Bleeding of C1-C2 venous sinus is vigorous and frustrating. The revised technique we describe provides theoretical and practical protection of venous sinus. In addition, the firm bony purchase of screws afforded by this technique contributes to achieving stabilization of the upper cervical spine and a high fusion rate.

Surgical treatment of craniovertebral junction instability : clinical outcomes and effectiveness in personal experience

OBJECTIVE

Craniovertebral junction (CVJ) consists of the occipital bone that surrounds the foramen magnum, the atlas and the axis vertebrae. The mortality and morbidity is high for irreducible CVJ lesion with cervico-medullary compression. In a clinical retrospective study, the authors reviewed clinical and radiographic results of occipitocervical fusion using a various methods in 32 patients with CVJ instability.

METHODS

Thirty-two CVJ lesions (18 male and 14 female) were treated in our department for 12 years. Instability resulted from trauma (14 cases), rheumatoid arthritis (8 cases), assimilation of atlas (4 cases), tumor (2 cases), basilar invagination (2 cases) and miscellaneous (2 cases). Thirty-two patients were internally fixed with 7 anterior and posterior decompression with occipitocervical fusion, 15 posterior decompression and occipitocervical fusion with wire-rod, 5 C1-2 transarticular screw fixation, and 5 C1 lateral mass-C2 transpedicular screw. Outcome (mean follow-up period, 38 months) was based on clinical and radiographic review. The clinical outcome was assessed by Japanese Orthopedic Association (JOA) score.

RESULTS

Nine neurologically intact patients remained same after surgery. Among 23 patients with cervical myelopathy, clinical improvement was noted in 18 cases (78.3%). One patient died 2 months after the surgery because of pneumonia and sepsis. Fusion was achieved in 27 patients (93%) at last follow-up. No patient developed evidence of new, recurrent, or progressive instability.

CONCLUSION

The authors conclude that early occipitocervical fusion to be recommended in case of reducible CVJ lesion and the appropriate decompression and occipitocervical fusion are recommended in case of irreducible craniovertebral junction lesion.

Risk factors for development of subaxial subluxations following atlantoaxial arthrodesis for atlantoaxial subluxations in rheumatoid arthritis

STUDY DESIGN

Retrospective radiographic/imaging study.

OBJECTIVE

To evaluate preoperative and sequential postoperative radiographs following C1-C2 arthrodesis for atlantoaxial subluxation in patients with rheumatoid arthritis (RA) to determine risk factors for the development of subaxial subluxations (SAS).

SUMMARY OF BACKGROUND DATA

The development of SAS has often been observed after C1-C2 arthrodesis. However, there have been no previous reports on the correlation between radiographic parameters and the incidence of postoperative SAS.

METHODS

The study group comprised of 58 patients with RA who underwent C1-C2 arthrodesis due to atlantoaxial subluxation. There were 5 men and 53 women with a mean age of 55.8 years. The mean follow-up period was 137 months. Nineteen patients with a postoperative SAS after C1-C2 arthrodesis were classified as the SAS+ group. Other 39 patients without a postoperative SAS were included in the SAS- group. Clinical outcomes and plain radiographs were reviewed retrospectively and compared between the 2 groups.

RESULTS

The difference between pre- and postoperative atlantoaxial (AA) angles in the SAS+ group was significantly greater than those in the SAS- group (P = 0.039). The C2-C7 angles changed significantly between pre- and postoperative periods in the SAS+ group (P = 0.039), but not in the SAS- group (P = 0.897). It was suggested that a large AA angle and a small C2-C7 angle observed at the early postoperative period were the risk factors for the development of SAS. We also demonstrated that a high incidence of the C3-C4 SAS resulted from excessive bone fusion at the C2-C3.

CONCLUSION

Excessive correction of AA angle is likely to cause loss of cervical lordosis, resulting in the development of postoperative SAS. In addition, extensive bony union at C2-C3 following C1-C2 arthrodesis frequently leads to the development of extensive SAS at the C3-C4.

Axis fractures

BACKGROUND

Traumatic fractures of the second cervical vertebra are common, representing nearly 20% of all acute cervical spinal fracture-dislocation injuries. They are divided into 3 distinct injury patterns: odontoid fractures, hangman's fracture injuries, and fractures of the axis body, involving all other fracture injuries to the C2 vertebra.

OBJECTIVE

An evidence-based overview of the medical and surgical treatment strategies for each axis fracture injury sub-type.

RESULTS

Current medical and surgical management of traumatic fractures of the axis.

Study of the anatomical variations of vertebral artery in C2 vertebra with magnetic resonance imaging and its application in the C1-C2 transarticular screw fixation

STUDY DESIGN

Use of magnetic resonance imaging (MRI) with Constructive Interference in Steady State (CISS) sequence and isometric voxels to demonstrate the anatomic variations of vertebral artery in C2 vertebra.

OBJECTIVES

To determine the transarticular screw trajectory on CISS MRI and to identify patients with anatomic variations of vertebral artery in C2 vertebra.

SUMMARY OF BACKGROUND DATA

Atlantoaxial transarticular screw fixation has been reported to be biomechanically superior to other posterior techniques for atlantoaxial arthrodesis. Vertebral artery injury can be associated with catastrophic sequelae. Anatomic variation of vertebral artery is well recognized and computed tomography scan is the traditional preoperative assessment. However, no report has evaluated the use of MRI in preoperative assessment for the screw trajectories and the anatomic variation of vertebral artery.

METHODS

The 3-dimensional (3D) CISS MRI with isometric voxels was performed in 30 local Chinese patients. The 3D reconstruction images were created to determine the proposed screw trajectories and their relationship with the vertebral arteries.

RESULTS

In 12 patients (40%), the vertebral arteries were lying within the screw trajectories prohibiting transarticular screw fixation on at least one side. Bilateral variations with high risk of vertebral artery injuries were found in 6 patients. The remaining 6 patients had unilateral variations prohibiting the insertion of transarticular screws on one side.

CONCLUSION

The 3D CISS MRI with isometric voxels is a safe and simple imaging technique to outline the vertebral arteries in C2. Reconstruction images are easily created and undistorted. It is one of the useful imaging in preoperative planning of transarticular screw fixation and determination of anatomy of vertebral artery.

Percutaneous anterior transarticular screw fixation for atlantoaxial instability

We reviewed the outcome of a retrospective case series of eight patients with atlantoaxial instability who had been treated by percutaneous anterior transarticular screw fixation and grafting under image-intensifier guidance between December 2005 and June 2008.

The mean follow-up was 19 months (8 to 27). All eight patients had a solid C1–2 fusion. There were no breakages or displacement of screws. All the patients with pre-operative neck pain had immediate relief from their symptoms or considerable improvement. There were no major complications. Our preliminary clinical results suggest that percutaneous anterior transarticulation screw fixation is technically feasible, safe, useful and minimally invasive when using the appropriate instruments allied to intra-operative image intensification, and by selecting the correct puncture point, angle and depth of insertion.

C1 lateral mass anatomy: Proper placement of lateral mass screws

STUDY DESIGN

Cadaveric specimens were measured to determine appropriate placement for C1 lateral mass screws. Instrumentation guidelines were developed and used to instrument a series of cadaveric specimens. Clinical experience with C1 lateral mass fixation was reviewed to evaluate results. Postoperative computed tomographic (CT) scans were reviewed to evaluate screw placement.

OBJECTIVES

The cadaveric study measured the dimensions of the atlas and determined ideal trajectory for screw placement. This technique was applied clinically, and 50 cases were retrospectively reviewed for fixation difficulties, neurologic or vascular injuries, and perioperative complications. Postoperative CT scans were reviewed when available.

SUMMARY OF BACKGROUND DATA

Halo application, posterior wiring, and C1 to C2 transarticular screws have been used to stabilize the upper cervical spine. Each technique has disadvantages, and C1 lateral mass fixation recently has gained popularity as a potential alternative. Recent anatomic studies have documented the dimensions of the C1 lateral mass and its ability to accommodate screw fixation. Small clinical series have documented early success with this technique.

METHODS

Fifteen specimens were stripped of soft tissue and measured by using calipers and CT scans. Guidelines were formulated for C1 lateral mass screw fixation. Additional specimens with intact soft tissue were instrumented without difficulty. A clinical series was reviewed to evaluate for complications related to this technique. Postoperative CT scans were reviewed to evaluate screw placement.

RESULTS

The C1 lateral mass safely accommodated screw fixation. Trajectory of 10 degrees medial and 22 degrees cephalad was preferred. The technique was safely applied in a series of 50 patients. Postoperative CT scans showed the ability of the surgeon to achieve the intended goals for starting point and safe trajectory.

CONCLUSIONS

C1 lateral mass fixation is a safe alternative for upper cervical fixation with several potential advantages versus other techniques, but further clinical evaluation is warranted.

Biomechanical assessment of bilateral C1 laminar hook and C1-2 transarticular screws and bone graft for atlantoaxial instability

STUDYDESIGN: In vitro biomechanical test was conducted to compare the stability of 5 different atlantoaxial posterior fusion techniques.

OBJECTIVE

To evaluate the biomechanical stability of an atlas laminar hook combined with transarticular (TA) screws relative to 4 different conventional fusion techniques.

SUMMARY OF BACKGROUND DATA

The atlantoaxial instability caused by fractures, rheumatoid arthritis, congenital deformity, or traumatic lesions of the transverse ligament often result in acute or chronic spinal cord compression, a possible threat to a patient's life. Posterior atlantoaxial fixations are used to reconstruct the stability of atlantoaxial articulation. Conventional posterior atlantoaxial fixations are associated with high rates of pseudoarthrosis and carry the potential risk of neurologic complication. TA screw fixation can provide an excellent biomechanical stability. As a modified 3-point fixation technique, the bilateral C1-2 TA screws have been combined with C1 laminar hook and bone grafts. This modified technique had carried good clinical outcomes.

METHODS

Eight human specimens (C0-C4) were loaded nondestructively with pure moments and the range of motion at the level of C1-C2 was measured. Eight specimens were implanted with each of the following techniques, respectively: Gallie fixation, C1-2 TA screw fixation combined with Gallie fixation, C1-2 TA screw fixation, C1 laminar hook combined with C1-2 TA screw fixation plus bone grafts, and the C1 lateral mass screws in the atlas combined with C2 isthmic screws in axis.

RESULTS

Although the C1-2 TA screws best restricted lateral bending and axial rotation, the modified 3-point fixation technique additionally restricted flexion-extension and provided the excellent stability. Differences in axial rotation and lateral bending (with + or - 1.5 Nm load) were observed when the 3-point fixation techniques (TA + Gallie and TA + hook) were compared with atlas lateral mass screws in the atlas combined with isthmic screws in axis.

CONCLUSIONS

The modified C1 laminar hook combined with C1-2 TA screws and bone graft fixation provided the best biomechanical stability. The C1 lateral mass screws in the atlas combined with isthmic screws in axis fixation is a sound alternative when the C1-2 TA screw fixation is not feasible.