Surgical approaches for cervical spine facet dislocations
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
The objective of this review is to compare the relative effectiveness and safety of different surgical approaches used for treating people with cervical spine facet dislocation. The main comparison will be anterior versus posterior approaches.
Background
Description of the condition
Fractures and dislocations of the spine are among the most challenging in trauma clinic practice. Although vertebral column injuries occur in approximately 6% of trauma patients, half sustain spinal cord or nerve root neurologic deficit (Burney 1993). The causes for traumatic spinal cord injury are motor vehicle‐related accidents (39.5% to 55%), violence‐related (14.2% to 29.5%), falls (18.8% to 23%) and sports injuries (7.3% to 11.1%) (Burke 2001; DeVivo 1997; Nobunaga 1999). For definitions of some of the terms, see the Glossary in Table 1.
| Term | Definition |
| Discectomy | Excision (cutting out), in part or whole, of an intervertebral disc. The most common indication is disc displacement or herniation (see 'Hernia'). In addition to standard surgical removal, it can be performed by percutaneous discectomy or by laparoscopic discectomy, the former being the more common. |
| Fracture | A break in a bone |
| Fracture fixation | The use of usually metallic devices inserted into or through bone to hold a fracture in a set position and alignment while it heals. |
| Facet dislocation | Complete displacement that occurs between facets of the interior (located below) and superior (located above) articular processes of adjacent vertebra |
| Hernia | Protrusion (pushing out) of tissue, structure, or part of an organ through the muscular tissue or the membrane by which it is normally contained |
| Reduction | The restoration, by surgical or manipulative procedures, of a part to its normal anatomic relation |
| Surgical decompression | A surgical operation for the relief of pressure in a body compartment or on a body part |
The incidence of spinal cord injuries (SCI) has remained stable over the past 30 years in North America, and ranges between 27 and 47 cases per million population (Fisher 2006). Besides that, it has been estimated that the annual incidence of spinal cord injury requiring hospitalisation in developed countries is approximately 11.5 to 53.4 per million population (Kraus 1975; Surkin 2000). The most common site of SCI is the cervical region, accounting for 50% to 64% of traumatic spinal cord injuries (Tator 1995). Approximately 40% of these injuries are associated with a neurologic deficit (Lasfargues 1995). Moreover, the incidence of traumatic disc herniations at the site of injury in this population may be about 54% (Robertson 1992).
The cervical or neck region of the spine consists of seven vertebrae. The first and second cervical vertebrae (C1 and C2), respectively the atlas and axis, form the upper cervical spine. The lower cervical spine comprises the third to the seventh vertebrae (C3 to C7). Below this is the thoracic region of the spine, starting with the T1 vertebra. Relative movement of the vertebrae is primarily via the facet joints. Starting from below C2, intervertebral discs lie between the cylindrical parts (centrum) of adjacent vertebrae. These discs act as shock absorbers, as well as allowing movement.
A traditionally used classification system for subaxial cervical spine injuries is that described by Allen et al (Allen 1982), which is based on the mechanism of injury, and is divided into six categories: compression‐flexion, vertical compression, distraction‐flexion, compression‐extension, distraction‐extension and lateral flexion. Facet dislocations are classified as distraction‐flexion injuries and account for approximately 10% of all subaxial cervical spine fractures. They may be unilateral or bilateral. Although pure ligamentous facet injuries are represented by facet dislocations by definition, it is important to note that facet fractures are part of the same spectrum of injury. Both types are probably the result of subtle differences in injury mechanism, in which pure ligamentous injuries occur when distractive forces across the posterior elements outweigh shear forces, whereas facet fractures take place when the facet is subjected to a relatively greater shear force. In both there are similar associated instability patterns and the same diagnostic, therapeutic, and prognostic factors (Bellabarba 2006).
Description of the intervention
Several aspects in the management of facet dislocations are controversial. Intervention may be considered in two stages: a) reduction, that can be performed closed with skull traction or surgically (by anterior or posterior approach), and b) internal fixation (by anterior or posterior approach).
It should be clearly established whether it is safe to undertake closed manipulation of the neck either awake or under anaesthesia. The timing of such closed reduction is important. Some authors believing that an early successful closed reduction protects the neurologic elements during a patient’s mobilisation and may potentially improve neurorecovery in compromised patients as compared with a delayed reduction (Kahn 1998; Lee 1994). Occasionally, gentle manipulation by an experienced surgeon would be necessary to reduce a perched facet during the traction procedure (Star 1990). Any treatment will be complicated by the presence of an intervertebral disc prolapse. Whether MR imaging is required before intervention is uncertain with some authors arguing that due to the high incidence of herniated discs at the time of cervical dislocations, an MRI should be obtained prior to reduction (Eismont 1991; Robertson 1992) while others consider that imaging is unnecessary during immediate awake closed traction in an alert and cooperative patient (Hart 2002).
Generally, facet dislocations are stabilised posteriorly, but recently there has been a trend towards anterior surgery, due to concern regarding the potential for any disc herniation to lead to spinal cord compression (De Lure 2003; Doran 1993; Eismont 1991; Harrington 1991; Harrop 2001; Maiman 1986).
Open posterior reduction and stabilization is accomplished by a distraction manoeuvre and the placing of a small instrument between the dislocated facets or, if necessary, by removal of the superior part of the caudal facet, allowing the dislocated facet to fall back to its original position. The subsequent fixation may be performed with sublaminar and/or spinous process wires, lateral mass or pedicle screws.
The anterior approach is initiated with decompression and discectomy of the level (of the spine) compromised by the injury, followed by a reduction manoeuvre (if necessary) that can be performed in many ways, including distraction with sequential application of weight, direct manipulation or reduction through Caspar vertebral pins. Thereafter, fixation may be achieved with iliac crest graft or cage placement at the intervertebral space associated with anterior cervical plating.
Some studies justify anterior procedures on the grounds of safety (Ordonez 2000; Reindl 2006), whereas others promote posterior cervical reduction and fusion even in the presence of a herniated disc (Abumi 2000) or anterior cervical discectomy and grafting followed by a posterior reduction and fusion (Allred 2001).
How the intervention might work
All surgical approaches (including anterior and posterior only approaches) for cervical facet dislocation may be used for reduction and fixation in an attempt to acquire anatomic realignment and bony fusion, and maximise neurologic recovery, long‐term relief of pain, functional recuperation and early return to activities of daily living.
Why it is important to do this review
The seriousness of cervical spine facet dislocations, including the risk of major complications such as paralysis, points to the need for evidence‐based practice. Although there appears to be a trend towards the use of the anterior approach for some types of these injuries, a recent survey found poor overall agreement between surgeons on the choice of surgical approach (Nassr 2008). This underlying variation in treatment indicates the uncertainty on the best approach and the need to conduct a systematic review of the best evidence to inform practice.
Objectives
The objective of this review is to compare the relative effectiveness and safety of different surgical approaches used for treating people with cervical spine facet dislocation. The main comparison will be anterior versus posterior approaches.
Methods
Criteria for considering studies for this review
Types of studies
We will include randomised and quasi‐randomised (method of allocating participants to a treatment which is not strictly random e.g. by date of birth, hospital record number, alternation) controlled trials.
Types of participants
We will include all studies relating to adults with an acute (less than three weeks) and radiologically confirmed distraction‐flexion dislocation, or fracture‐dislocation of the lower cervical spine with or without neurological deficit. Trials including participants with unilateral or bilateral facet dislocation injuries will be included. Trials including adolescents and/or people with other cervical spine injuries will be included, provided separate data can be obtained or the proportion is small.
Types of interventions
Included will be trials comparing different surgical approaches for these injuries. The main comparison will be the anterior versus the posterior approach for either open reduction and fixation or fixation after initial closed reduction.
1. Anterior surgical approaches, including:
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anterior cervical surgical reduction and fixation
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closed reduction followed by anterior cervical surgical fixation
2. Posterior surgical approaches, including:
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posterior cervical surgical reduction and fixation
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closed reduction followed by posterior cervical surgical fixation.
3. Combined approaches following closed reduction:
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anterior‐posterior
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anterior‐posterior‐anterior
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posterior‐anterior
4. Combined approaches (with open reduction):
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anterior‐posterior
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anterior‐posterior‐anterior
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posterior‐anterior
Types of outcome measures
Primary outcomes
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Immediate post surgical neurologic status (recovery or deterioration)
Secondary outcomes
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Dislocation reduction and/or realignment
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Bone fusion
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Pain
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Functional aspects (e.g. number of patients who returned to former occupation) and health related quality of life (e.g. SF‐36))
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Surgical complications with need for another major operation: pseudarthrosis, infection and implant failure or loss of fixation
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Blood loss
Only validated measure instruments will be considered for analysis. We will accept outcomes measured at any time of follow‐up.
Search methods for identification of studies
Electronic searches
We will search the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register, The Cochrane Central Register of Controlled Trials (The Cochrane Library, current issue), MEDLINE (via PubMed), EMBASE (via Ovid) and LILACS ‐ Latin American and Caribbean Health Science Literature database (via Bireme). We will also search Current Controlled Trials and the WHO International Clinical Trials Registry. No language restrictions will be applied.
Search strategies composed of descriptors for the clinical condition, intervention of interest, as well as an RCT filter, for each database are presented in Appendix 1. The MEDLINE search will be combined with the Cochrane Highly Sensitive Search Strategy for identifying randomised trials: sensitivity‐maximizing version (Lefebvre 2008) and the LILACS search will be combined with the optimal search strategy for clinical trials in LILACS (Castro 1999).
Searching other resources
We will also search reference list of relevant articles, including narrative reviews if located, conference proceedings and book chapters. We will also contact other researchers/experts in the field.
Data collection and analysis
Selection of studies
Two review authors (DDC and DEM) will independently assess the titles and abstracts of the identified articles to determine potential relevance. Any disagreement will be resolved by discussion or by a third opinion (EP).
Data extraction and management
Two review authors (DDC and DEM) will independently extract data from each study using a pre‐piloted data extraction form. Any unresolved disagreement will be resolved by discussion with another author (EBP).
Assessment of risk of bias in included studies
Two review authors (DDC and DEM) will independently assess the risk of bias of the included studies using The Cochrane Collaboration's 'Risk of Bias' tool (Higgins 2008). This tool incorporates assessment of randomisation (sequence generation and allocation concealment), blinding (participants, personnel and outcome assessors), completeness of outcome data, selection of outcomes reported and other sources of bias. Other sources of bias will include selection bias resulting from major imbalances in baseline characteristics (e.g. spinal cord injury) and performance bias, where we will assess the risk of bias from systematic differences in the experience of the operating surgeon(s), and subsequent rehabilitation. We will assess the risk of bias associated with a) blinding and b) completeness of outcomes for patient‐reported outcomes and objective outcomes separately. Any unresolved disagreement will be resolved by discussion with a third author (RBA). Titles of journals, names of authors or supporting institutions will not be masked at any stage.
Measures of treatment effect
For dichotomous and continuous variables, risk ratios (relative risks; RR) and mean differences (MD) with 95% confidence intervals (CI) will be calculated, respectively. When data from primary studies are not parametric (e.g. effects reported as medians, quartiles, etc) or are not adequately reported (e.g. without standard deviations, number of patients), they will be presented in separate tables.
Unit of analysis issues
Unit of analysis issues are unlikely for this topic: both the unit of randomisation and analysis are likely to be the individual patient.
Dealing with missing data
For dichotomous data, we will perform intention‐to‐treat analyses to include all people randomised to the intervention groups. For continuous data, authors of included studies will be contacted to supply missing information in order that the last available data before the withdrawal or drop‐out can be included in the analysis. We will consider performing available case analysis if our efforts to acquire missing data from authors are unsuccessful. If studies did not report dropouts we will assume there were none.
Assessment of heterogeneity
Heterogeneity will be assessed by visual inspection of the forest plot (analysis) along with consideration of the chi² test for heterogeneity and the I² statistic (Higgins 2003).
Assessment of reporting biases
We will attempt to assess publication bias by preparing a funnel plot if a sufficient number of studies are available (10 studies). However, we are aware that asymmetry in the funnel plot can be associated with other reasons than publication bias (e.g. chance, real heterogeneity, clinical particularities inherent to each one of the included studies, such as patients at high risk for the outcome).
Data synthesis
If considered appropriate, results of comparable groups of trials will be pooled. For dichotomous variables, risk ratios (RR) will be calculated. For continuous variables, mean differences (MD) will be calculated, unless data are derived from disparate outcome measures, in which case standardised mean differences (SMD) will be calculated. The random‐effects model will be used since we are expecting substantial clinical and methodological heterogeneity, which by themselves could generate substantial statistical heterogeneity.
Subgroup analysis and investigation of heterogeneity
We plan subgroup analyses by age and gender, fracture type (unilateral versus bilateral facet dislocation) and neurological status (neurologically intact, incomplete and complete spinal cord injury), and MRI before reduction procedure. The heterogeneity in both direction and length of estimate effect among studies subgrouped according to the different characteristics already mentioned will be assumed as a probable causal relationship between them.
Sensitivity analysis
Where possible, we plan sensitivity analyses examining various aspects of trial and review methodology, including the effects of intention‐to‐treat and available data analysis, and inclusion of trials without concealment of allocation or those only reported in abstracts.
| Term | Definition |
| Discectomy | Excision (cutting out), in part or whole, of an intervertebral disc. The most common indication is disc displacement or herniation (see 'Hernia'). In addition to standard surgical removal, it can be performed by percutaneous discectomy or by laparoscopic discectomy, the former being the more common. |
| Fracture | A break in a bone |
| Fracture fixation | The use of usually metallic devices inserted into or through bone to hold a fracture in a set position and alignment while it heals. |
| Facet dislocation | Complete displacement that occurs between facets of the interior (located below) and superior (located above) articular processes of adjacent vertebra |
| Hernia | Protrusion (pushing out) of tissue, structure, or part of an organ through the muscular tissue or the membrane by which it is normally contained |
| Reduction | The restoration, by surgical or manipulative procedures, of a part to its normal anatomic relation |
| Surgical decompression | A surgical operation for the relief of pressure in a body compartment or on a body part |
