Indirect posterior reduction and fusion of the traumatic herniated disc by using a cervical pedicle screw system

Epidemiological characteristics of 1,806 patients with traumatic spinal cord injury: A retrospective study

Background

Traumatic spinal cord injury (TSCI) is a type of highly disabling central nervous system trauma. In this study, we investigated the epidemiological characteristics of 1,806 TSCI patients and compared the characteristics of patients with traumatic cervical spinal cord injury (TCSCI) caused by cervical fracture/dislocation and disc herniation/bulging.

Methods

We retrospectively reviewed the hospital records of 1,806 TSCI patients. The detailed information included gender, marital status, occupation, age, neurological level of injury, etiology, American Spinal Injury Association (ASIA) grade, combined injuries, complications, treatment, the interval between admission and surgery, intubation/tracheostomy requirement, and the length of hospital stay.

Results

Cervical spinal cord injury (CSCI) was the most common injury. Compared to non-CSCI cases, patients with TCSCI were older, and more likely to suffer from tetraplegia and require intubation/tracheostomy, but had fewer other injuries or complications and a shorter length of hospital stay. Compared to patients with cervical fracture/dislocation, those with TCSCI caused by disc herniation/bulging were older and more likely to suffer from paraplegia, but required intubation/tracheostomy less frequently, exhibited fewer other injuries and complications, and required shorter hospitalization.

Conclusions

Men, married individuals, manual laborers, and individuals aged 31-75 years had the highest risk of TSCI. Patients with TCSCI tended to have a shorter length of hospital stay than patients with non-CSCI. More attention should be paid to the other injuries and complications of non-CSCI patients, which may increase the length of hospital stay and delay rehabilitation. Compared to patients with cervical disc herniation, the patients with fracture/dislocation tended to be younger, but prognosis was severely compromised by tetraplegia, a greater need for intubation/tracheostomy, additional injuries, and complications.

Intraoperative image guidance for cervical spine surgery

Intraoperative image-guidance in spinal surgery has been influenced by various technological developments in imaging science since the early 1990s. The technology has evolved from simple fluoroscopic-based guidance to state-of-art intraoperative computed tomography (iCT)-based navigation systems. Although the intraoperative navigation is more commonly used in thoracolumbar spine surgery, this newer imaging platform has rapidly gained popularity in cervical approaches. The purpose of this manuscript is to address the applications of advanced image-guidance in cervical spine surgery and to describe the use of intraoperative neuro-navigation in surgical planning and execution. In this review, we aim to cover the following surgical techniques: anterior cervical approaches, atlanto-axial fixation, subaxial instrumentation, percutaneous interfacet cage implantation as well as minimally invasive posterior cervical foraminotomy (PCF) and unilateral laminotomy for bilateral decompression. The currently available data suggested that the use of 3D navigation significantly reduces the screw malposition, operative time, mean blood loss, radiation exposure, and complication rates in comparison to the conventional fluoroscopic-guidance. With the advancements in technology and surgical techniques, 3D navigation has potential to replace conventional fluoroscopy completely.

Can Posterior Ligament Structure Be Functionally Healed After Anterior Reduction and Fusion Surgery in Patients with Traumatic Subaxial Cervical Fracture-Dislocations?

BACKGROUND

Selection of approach for subaxial cervical fracture-dislocation (SCFD) is controversial. The questions of whether a posterior ligamentous structure (PLS) can be functionally healed in patients with SCFD and how long this healing process takes are critical in these patients.

METHODS

This study retrospectively enrolled 394 patients with SCFD who underwent anterior decompression, reduction, and fusion between January 2002 and December 2017. The definition of functional healing of PLS was based on evaluations of clinical function and radiographic stability of PLS.

RESULTS

Follow-up was available for 354 patients (89.8%). The PLS of 339 cases was functionally healed at the first follow-up interval without any posterior surgical intervention. No hardware failure or progressive cervical kyphosis was observed at further follow-up. At 12 months postoperatively, interbody fusion was satisfactory. However, the other 15 patients experienced nonhealing PLS at 8 weeks postoperatively and developed cervical deformity at further follow-up. Five patients refused revision surgery; the other 10 patients obtained solid fusion after revision surgeries.

CONCLUSIONS

Among 354 patients with SCFD and treated by single anterior reduction and fixation, simple PLS injury without any bony instability at the posterior column of the cervical spine can be functionally healed in 95.8% of patients by external fixation for 8 weeks. Whether this finding is applicable to various types of SCFD should be verified in further prospective studies with larger samples.

Clinical Efficacy of Anterior Partial Corpectomy and Titanium Mesh Fusion and Internal Fixation for Treatment of Old Fracture Dislocation of the Lower Cervical Spine

Background

The aim of this study was to analyze the clinical features and to evaluate the efficacy of anterior partial corpectomy and titanium mesh fusion and internal fixation of old fracture dislocation of the lower cervical spine.

Material/Methods

We retrospectively analyzed the clinical data of 52 patients with old lower cervical fracture and dislocation treated with anterior partial corpectomy and titanium mesh fusion fixation between January 2008 and December 2013, with a mean follow-up period of 4.1 years. There were 35 males and 17 females. Patient radiological data and clinical parameters were recorded and compared before and after the operations.

Results

The average follow-up was 4.1 years. Intervertebral height and physiological curvature were well-reconstructed for all cases. No loosening or rupturing of titanium plate or screw occurred. The neurological function of the patients with incomplete spinal cord injury was significantly improved, and the function of the nerve roots at the injury level was also improved in patients with complete spinal cord injury. Bone fusion was completed within 6 months to 1 year after surgery.

Conclusions

Completed decompression, sequence and physiological curvature of the cervical vertebra, immediate and long-term anterior cervical column support, and nerve function restoration can be achieved by using anterior partial corpectomy and titanium mesh fusion and internal fixation to treat old fracture dislocation of the lower cervical spine. For cases with locked facet joints or posterior structures invading the vertebral canal, the combined anterior and posterior approaches should be performed, when necessary, to achieve better results.

Anatomic study of individualized and improved pedicle screw implantation in the lower cervical spine

The objective of this study was to explore a safe, reliable, and effective method for pedicle screw implantation in the lower cervical spine. Recently, a number of studies have shown that cervical pedicle screw fixation is better than roadside steel plate after cervical screw internal fixation within the scope of its indications. However, the difficulty of the former surgery technology is relatively higher and it is much easier to cause many complications. Therefore, domestic and foreign scholars have been positively exploring safer, easier operations and cheaper methods of pedicle screw implantation in the lower cervical spine. The lower cervical spine areas (C3-C7) of 7 adult cadavers were carried out with computed tomography (CT) scans of 1-mm slices. The entry point, angle, and length of the screws were determined by the measurement of CT images in a picture archiving and communication system. The pedicle screws were implanted with the technique of improved Abumi pedicle screw placement in the lab. The accuracy of the screws was evaluated by the Andrew CT classification criteria of pedicle screw position and gross observation after the experiment. A total of 66 screws were implanted in the lower cervical spine, and 90.9% of the screws inserted were found to be in an optimal position. The method of individualized and improved pedicle screw implantation in the lower cervical spine is relatively safe and reliable, which can be considered to be used in the clinic.

Surgical approaches for cervical spine facet dislocations in adults

BACKGROUND

The choice of surgical approach for the management of subaxial cervical spine facet dislocations is a controversial subject amongst spine surgeons. Reasons for this include differences in the technical familiarity and experience of surgeons with the different surgical approaches, and variable interpretation of image studies regarding the existence of a traumatic intervertebral disc herniation and of the neurological status of the patient. Moreover, since the approaches are dissimilar, important variations are likely in neurological, radiographical and clinical outcomes.

OBJECTIVES

To compare the effects (benefits and harms) of the different surgical approaches used for treating adults with acute cervical spine facet dislocation.

SEARCH METHODS

We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (9 May 2014), The Cochrane Central Register of Controlled Trials (The Cochrane Library, 2014 Issue 4), MEDLINE (1946 to April Week 5 2014), MEDLINE In-Process & Other Non-Indexed Citations (8 May 2013), EMBASE (1980 to 2014 Week 18), Latin American and Caribbean Health Sciences (9 May 2014), trial registries, conference proceedings and reference lists of articles to May 2014.

SELECTION CRITERIA

We included randomised and quasi-randomised controlled trials that compared surgical approaches for the management of adults with acute cervical spine facet dislocations with and without spinal cord injury.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies, assessed risk of bias and extracted data.

MAIN RESULTS

We included one randomised and one quasi-randomised controlled trial involving a total of 94 participants and reporting results for a maximum of 84 participants. One trial included patients with spinal cord injuries and the other included patients without spinal cord injuries. Both trials compared anterior versus posterior surgical approaches. Both trials were at high risk of bias, including selection bias (one trial), performance bias (both trials) and attrition bias (one trial). Data were pooled for one outcome only: non-union. Reflecting also the imprecision of the results, the evidence was deemed to be of very low quality for all outcomes; which means that our level of uncertainty about the estimates is high.Neither trial found differences between the two approaches in neurological recovery or status, as shown in one study by small clinically insignificant differences in NASS (Northern American Spine Society) neurological scores (0 to 100: optimal score) at one year of follow-up: anterior mean score: 85.23 versus posterior mean score: 83.86; mean difference (MD) 1.37 favouring anterior approach, 95% confidence interval (CI) -9.76 to 12.50; 33 participants; 1 study). The same trial found no relevant between-approach differences at one year in patient-reported quality of life measured using the 36-item Short Form Survey physical (MD -0.08, 95% CI -7.26 to 7.10) and mental component scores (MD 2.88, 95% CI -3.32 to 9.08). Neither trial found evidence of significant differences in long-term pain, or non-union (2/38 versus 2/46; risk ratio (RR) 1.18, 95% CI 0.04 to 34.91). One trial found better sagittal and more 'normal' alignment after the anterior approach (MD -10.31 degrees favouring anterior approach, 95% CI -14.95 degrees to -5.67 degrees), while the other trial reported no significant differences in cervical alignment. There was insufficient evidence to indicate between-group differences in medical adverse events, rates of instrumentation failure and infection. One trial found that the several participants had voice and swallowing disorders after anterior approach surgery (11/20) versus none (0/22) in the posterior approach group: RR 25.19, 95% CI 1.58 to 401.58); all had recovered by three months.

AUTHORS' CONCLUSIONS

Very low quality evidence from two trials indicated little difference in long-term neurological status, pain or patient-reported quality of life between anterior and posterior surgical approaches to the management of individuals with subaxial cervical spine facet dislocations. Sagittal alignment may be better achieved with the anterior approach. There was insufficient evidence available to indicate between-group differences in medical adverse events, rates of instrumentation failure and infection. The disorders of the voice and swallowing that occurred exclusively in the anterior approach group all resolved by three months. We are very uncertain about this evidence and thus we cannot say whether one approach is better than the other. There was no evidence available for other approaches. Further higher quality multicentre randomised trials are warranted.

Morphometry of typical cervical vertebrae on dry bones and CT scan and its implications in transpedicular screw placement surgery

BACKGROUND

Transpedicular stabilization of subaxial cervical spine is a very delicate procedure that requires thorough understanding of the pedicle anatomy to minimize the rate of neurovascular complications. The current study was conducted to investigate the morphometric details including dimensions and axis of typical cervical vertebrae (C3-C6) for transpedicular screw insertion surgery.

METHODS

The current study was conducted on 100 sides of 50 dry and 160 sides of 80 vertebrae on computerized tomography scans of typical cervical vertebrae. Parameters that were studied bilaterally included distance between medial aspect of the pedicle and dural sac, pedicle height, pedicle width, interpedicular distance, lateral and medial cortical thickness, transverse pedicle angle and chord length.

RESULTS

Distance between medial aspect of the pedicle and dural sac was found to be 2.2 ± 0.99 mm. Mean pedicle height (6.5 ± 1.1 mm) was found to be greater than pedicle width (4.9 ± 0.9 mm) in all the vertebrae. Mean transverse pedicle angle and chord length was observed to be 39.4° and 32.1 mm, respectively. Mean interpedicular distance, medial and lateral cortical thickness was observed to be 21.8 ± 1.6, 1.43 ± 0.4 and 0.79 ± 0.2 mm, respectively.

CONCLUSIONS

The present study highlights a three-dimensional orientation of subaxial cervical pedicle anatomy, while emphasizing the risks involved in the view of comparatively smaller values of pedicle dimensions of subaxial cervical vertebrae. This knowledge about typical cervical vertebrae, its pedicle and their adjacent neurovascular structures may enhance the safety of transpedicular screw insertion.

Posterior approach for cervical fracture-dislocations with traumatic disc herniation

In the treatment algorithm for cervical spine fracture-dislocations, the recommended approach for treatment if there is a disc fragment in the canal is the anterior approach. The posterior approach is not common because of the disadvantage of potential neurological deterioration during reduction in traumatic cervical herniation patients. However, reports about the frequency of this deterioration and the behavior of disc fragments after reduction are scarce. Forty patients with traumatic disc herniation were observed. They represented 29.2% of 137 consecutive patients with subaxial cervical spine fracture-dislocations. Surgical planning was performed according to our two-stage algorithm. In the first stage, they were treated with posterior open reduction and posterior spine arthrodesis. In the second stage, anterior surgery was added for cases where neurological deterioration attributed to non-reduced disc fragments on postoperative magnetic resonance imaging (MRI). Neurological deterioration after posterior open reduction was not observed. Furthermore, 25% of total cases and 75% of incomplete paralysis cases improved postoperatively by ≥ 1 grade in the American Spinal Injury Association impairment scale. Reduction or reversal of disc herniation was observed in all cases undergoing postoperative MRI. For local sagittal alignment, preoperative 9.4° kyphosis was corrected to 6.9° lordosis postoperatively. The disc height ratio was 72.4% preoperatively and 106.3% postoperatively. The second stage of our plan was not required after the posterior approach in this series. The incidence of neurological deterioration after posterior open reduction was zero, even in cases with traumatic cervical disc herniation. Favorable clinical and radiological outcomes could be obtained by the first stage alone. Although preparations for prompt anterior surgery should always be made to cover any contingency, the need for them is minimal.

Computer navigation assisted fixation in neglected C2-C3 dislocation in an adult

A 49-year-old male presented with neck pain and deformity following an industrial accident sustained two months back. His neurology was normal except for a minimal weakness in left biceps (grade 4/5). Radiographs, magnetic resonance imaging and computed tomographic scan revealed fracture dislocation of C2-C3 with significant lateral translation of C2 over C3 without disc herniation. In view of unsuccessful closed reduction and absent disc herniation at the level of dislocation, a posterior only reduction, stabilisation and fusion with Iso-C 3D computer navigation-assisted cervical pedicle screw fixation with transverse rod-screw construct was performed. At 6 months followup the patient was completely relieved of his symptoms and was able to return to his previous occupation. The rare case is reported for the management by Iso-C 3D computer navigation assisted cervical pedicle screw fixation and reduction with transverse rod-screw construct at each involved level.

Clinical accuracy of cervical pedicle screw insertion using lateral fluoroscopy: a radiographic analysis of the learning curve

Cervical pedicle screw is thought to be the most stable instrumentation for reconstructive surgery of the cervical spine. However, because of the unresolved and inherent risk of neurovascular injuries due to screw perforation, it remains not widespread nowadays despite the excellent biomechanical property. Fifty-two consecutive cases having undergone spinal reconstruction using cervical pedicle screw were investigated. There were 24 females and 28 males. The mean follow-up period was 53 months. Those patients were stratified into three groups according to the period of screw insertion. A total of 280 screws were inserted. Ninety-two screws in 19 cases, 100 screws in 18 cases and 88 screws in 15 cases were inserted in the earlier, the middle and the later periods, respectively. Clinical results including complications were recorded in all cases. Screw perforations were evaluated in both plain X-ray and CT. Screw perforations occurred in 11 (12.0%), 7 (7.0%) and 1 (1.1%) screws in each period. There were no complications, such as infection, neurological deterioration and neurovascular injury directly related to screw insertion. The learning curve showed a significant improvement especially in the later period. However, the perforation rates in both the earlier and middle periods must not be underestimated. Surgeons with less experience must insert cervical pedicle screws with the assistance of a senior surgeon to avoid lethal complications.

Image-based drill templates for cervical pedicle screw placement

OBJECT

Pedicle screws (PSs) in the cervical spine can provide fixation superior to current fixation methods; however, their implementation is challenging due to the small size of the cervical vertebrae. In this study, the authors explored and evaluated the use of patient-specific, rapid prototype drill templates for PS placement in the cervical spine. The goal of the study was to assess the accuracy of a drill template in the placement of cervical PSs at a single vertebral level.

METHODS

Volumetric CT scanning was performed in 4 cadaveric cervical spines. Using computer software, the authors constructed drill templates with a predefined trajectory designed to match the posterior surface of vertebrae C3-7. Twenty physical templates were created from the computer models using a rapid prototyping machine. The drill templates were used to guide pilot-hole drilling, and CT scanning was performed to assess the accuracy of the pilot holes. Pedicle screws (3.5-mm diameter) were placed in the pilot holes. The spines were then dissected to separate the vertebrae, and the trajectory of the screws was visually inspected.

RESULTS

The feasibility of this patient-specific, rapid prototyping technique was demonstrated. Imaging and visual inspection of pilot holes and cervical PSs revealed that the majority of trajectories did not violate the pedicle cortex (19 [95%] of 20). The single cortical violation was judged as noncritical and would probably not have resulted in injury to a patient.

CONCLUSIONS

The potential of drill templates to aid in the placement of cervical PSs is promising. The authors' methods appear to provide an accurate technique and trajectory for PS placement in the cervical spine.

[Reduction of traumatic dislocations and facet fracture-dislocations in the lower cervical spine]

BACKGROUND

Traumatic facet dislocations and facet-fracture dislocations in the lower cervical spine (C2/C3 to C7/T1) are frequently associated with devastating neurological symptoms. A good outcome can only be achieved if the operator has wide and sound knowledge of reduction techniques and the best possible strategy is devised for the subsequent treatment of these severe lesions.

PATIENTS AND METHODS

Between 1973 and 1997 a total of 117 of our patients met at least one of the following inclusion criteria: unilateral locked facet dislocation (48%), bilateral locked facet dislocations (23%), unilateral "perched" facet subluxation (14%), bilateral perched facet subluxation (12%), uni- or bilateral dislocation/perched subluxation with facet fractures (3%).

RESULTS

Most of the lesions were located at the levels of C5/C6 and C6/7 (n=46 for each). Associated neurological deficits were present initially in 65% of patients: 35% had complete or incomplete spinal cord injuries (tetraplegia), 2% were paraplegic, and 28% had cervical radiculopathies.

CONCLUSIONS

Closed reduction (e.g. with the aid of a halo ring) should be carried out as soon as possible after lower cervical spine dislocation or facet-fracture dislocation, as both the success rate of reduction and the potential for recovery from neurological deficits are clearly higher when reduction is achieved within the first 4 h after the initial injury.

Cervical pedicle screws vs. lateral mass screws: uniplanar fatigue analysis and residual pullout strengths

BACKGROUND CONTEXT

Although successful clinical use of cervical pedicle screws has been reported, anatomical studies have shown the possibility for serious iatrogenic injury. However, there are only a limited number of reports on the biomechanical properties of these screws which evaluate the potential benefits of their application.

PURPOSE

To investigate if the pull-out strengths after cyclic uniplanar loading of cervical pedicle screws are superior to lateral mass screws.

STUDY DESIGN

An in vitro biomechanical study.

METHODS

Twenty fresh-frozen disarticulated human vertebrae (C3-C7) were randomized to receive both a 3.5 mm cervical pedicle screw and lateral mass screw. The screws were cyclically loaded 200 times in the sagittal plane. The amount of displacement was recorded every 50 cycles. After cyclical loading, the screws were pulled and tensile load to failure was recorded. Bone density was measured in each specimen and maximum screw insertion torque was recorded for each screw.

RESULTS

During loading the two screw types showed similar stability initially, however the lateral mass screws rapidly loosened compared to the pedicle screws. The rate of loosening in the lateral mass screws was widely variable, while the performance of the pedicle screws was very consistent. The pullout strengths were significantly higher for the cervical pedicle screws (1214 N vs. 332 N) and 40% failed by fracture of the pedicle rather than screw pullout. Pedicle screw pullout strengths correlated with both screw insertion torque and specimen bone density.

CONCLUSIONS

Cervical pedicle screws demonstrated a significantly lower rate of loosening at the bone-screw interface, as well as higher strength after fatigue testing. These biomechanical strengths may justify their use in certain limited clinical applications.

Complications of transpedicular screw fixation in the cervical spine

Today, posterior stabilization of the cervical spine is most frequently performed by lateral mass screws or spinous process wiring. These techniques do not always provide sufficient stability, and anterior fusion procedures are added secondarily. Recently, transpedicular screw fixation of the cervical spine has been introduced to provide a one-stage stable posterior fixation. The aim of the present prospective study is to examine if cervical pedicle screw fixation can be done by low risk and to identify potential risk factors associated with this technique. All patients stabilized by cervical transpedicular screw fixation between 1999 and 2002 were included. Cervical disorders included multisegmental degenerative instability with cervical myelopathy in 16 patients, segmental instability caused by rheumatoid arthritis in three, trauma in five and instability caused by infection in two patients. In most cases additional decompression of the spinal cord and bone graft placement were performed. Pre-operative and post-operative CT-scans (2-mm cuts) and plain X-rays served to determine changes in alignment and the position of the screws. Clinical outcome was assessed in all cases. Ninety-four cervical pedicle screws were implanted in 26 patients, most frequently at the C3 (26 screws) and C4 levels (19 screws). Radiologically 66 screws (70%) were placed correctly (maximal breach 1 mm) whereas 20 screws (21%) were misplaced with reduction of mechanical strength, slight narrowing of the vertebral artery canal (<25%) or the lateral recess without compression of neural structures. However, these misplacements were asymptomatic in all cases. Another eight screws (9%) had a critical breach. Four of them showed a narrowing of the vertebral artery canal of more then 25%, in all cases without vascular problems. Three screws passed through the intervertebral foramen, causing temporary paresis in one case and a new sensory loss in another. In the latter patient revision surgery was performed. The screw was loosened and had to be corrected. The only statistically significant risk factor was the level of surgery: all critical breaches were seen from C3 to C5. Percutaneous application of the screws reduced the risk for misplacement, although this finding was not statistically significant. There was also a remarkable learning curve. Instrumentation with cervical transpedicular screws results in very stable fixation. However, with the use of new techniques like percutaneous screw application or computerized image guidance there remains a risk for damaging nerve roots or the vertebral artery. This technique should be reserved for highly selected patients with clear indications and to highly experienced spine surgeons.

Spinal reconstruction using a cervical pedicle screw system

Although the cervical pedicle screw system is considered the most effective instrumentation for posterior cervical spine surgery, reports on clinical application are limited because of the unresolved and inherent risk of neurovascular complications. The purpose of this study is to retrospectively evaluate the accuracy of placement and clinical effectiveness of the cervical pedicle screw. The cases of 26 patients were investigated. The average followup was 20 months. All but one patient had simultaneous decompression and fusion of various extent. In these cases, screw placement, alignment of the fused segment, fusion rate, neurologic improvement, and complications were assessed. Using an image intensifier, 134 screws were inserted. Five screws (3.7%) completely perforated and 10 (7.4%) partially perforated. The complete perforations occurred in the first 10 patients. Except for two patients with metastasis, bony union was obtained in all patients without loss of correction. Neurologic impairment also was improved in all patients, and no complications associated with the cervical pedicle screw were seen. Clinical results of the cervical pedicle screw system were excellent with few complications. However, there is the possibility of screw perforation, which could cause neurovascular complications. Increased accuracy of screw insertion is needed to make this instrumentation safer.

Computer-assisted posterior instrumentation of the cervical and cervico-thoracic spine

Posterior instrumentation of the cervical spine has become increasingly popular in recent years. Dissatisfaction with lateral mass fixation, especially at the cervico-thoracic junction, has led spine surgeons to use pedicle screws. The improved biomechanical stability of pedicle screws and transarticular C1/2 screws allows for shorter instrumentations and improves the repositioning possibilities. Nevertheless, there are potential risks of iatrogenic damage to the spinal cord, nerve roots or the vertebral artery with both techniques. Therefore, the aim of this study was to evaluate whether C1/2 transarticular screws and transpedicular screws can be applied safely and with high accuracy in the cervical spine and the cervico-thoracic junction using a computer-assisted surgery system (CAS system). Posterior instrumentation was performed using the Brainlab VectorVision System (BrainLAB, Heimstetten, Germany) in 19 patients. Surface matching was used for registration. We placed 22 transarticular screws C1/2, 31 cervical pedicle screws, 10 high thoracic pedicle screws and one lateral mass screw C1. The screw position was evaluated postoperatively using CT with multiplanar reconstruction in the screw axis of each screw. None of the transarticular screws or pedicle screws was significantly (>2 mm) misplaced and no screw-related injury to vascular, neurogenic or bony structures was observed. No screw revision was necessary. The mean operation time was 144 min (90-240 min) and the mean blood loss was 234 ml (50-800 ml). C1/2 transarticular screws, as well as transpedicular screws in the cervical spine and the cervico-thoracic junction, can be applied safely and with high accuracy using a CAS system. Computer-assisted instrumentation is recommended especially for pedicle screws at C3-C6.

Delayed management of traumatic bilateral cervical facet dislocation: surgical strategy. Report of three cases

Postinjury cervical spine instability typically requires surgical treatment in the acute or semiacute stage. The authors, however, report on three patients with older (> 8 weeks) untreated bilateral cervical facet dislocation. In two patients they attempted a classic anterior-posterior-anterior approach but failed. The misalignment in the second stage of the procedure could not be corrected, and they had to add a fourth, posterior, stage. To avoid the fourth stage, thereby reducing operating time and risk of neurological damage while turning the patient, they propose the following sequence: 1) a posterior approach to perform a complete facetectomy bilaterally with no attempt to reduce the dislocation; 2) an anterior microscopic discectomy with reduction of the dislocation and anterior fixation; and 3) posterior fixation. This sequence of procedures was successfully performed in the third patient. Based on this experience, they suggest that in cases of nonacute bilateral cervical facet dislocations the operating sequence should be posterior-anterior-posterior.