List of abbreviations
AIS
ASIA Impairment Scale
ASIA score
American Spinal Injury Association score
CCS
Central Cord Syndrome
CES
Cauda Equina Syndrome
CMS
Conus Medullary Syndrome
CRHSCIR
Canadian Rick Hansen Spinal Cord Injury Registry
CSM
cervical spondylotic myelopathy
ESD
early surgical decompression
NACTN
North American Clinical Trials Network for SCI
SCI
spinal cord injury
SCIM
spinal cord independence measure
SD
surgical decompression
SDSF
surgical decompression and segment fixation
STACSIS study
Surgical Timing in Acute Spinal Cord Injury study
Introduction
Historically, closed reduction with external immobilization was the milestone of treatment for acute SCI and only few cases were reserved for surgical management. However, in the last 2 decades, spine surgeons emphasized early surgical management of SCI ( ; ; ).
Preclinical studies suggested that persistent compression of spinal cord after primary injury is responsible for an additional secondary damage which might be avoided reducing tissue damage as soon as possible and improving outcomes ( ; ).
SDSF allows stabilization of vertebral column and decompression of spinal cord. Moreover, stabilization prevents any further trauma on spinal cord and allows early rehabilitation ( ).
Since vascular mechanisms of secondary injury after SCI were already discovered in the past, the practice of ESD has now biological support ( ; ).
Removing spinal cord compression and restoring blood supply should reduce the biochemical process induced by ischemia due to local compression ( ; ; ).
Despite the increasing literature, there are still some unanswered questions about the optimal methods for ESD. We still don’t know if all patients are going to benefit from ESD or if there are subgroups which are more likely to benefit than others ( Table 1 ). We still don’t know the appropriate time for surgical intervention balancing key priorities of efficacy and clinical feasibility.
| Classification of spinal cord injury (SCI) severity | |||
|---|---|---|---|
| Normal neurological condition | Incomplete SCI | Complete SCI | Clinical syndromes |
| ASIA scale E | ASIA scale B, C or D | ASIA scale A |
|
In this narrative review, we will highlight the situation of last 20 years literature about ESD in patients with acute SCI focusing to which subgroups of SCI will benefit from ESD and the time of surgical intervention.
Natural history of patients with acute cervical SCI
Approximately, one third of patients with cervical SCI has a complete injury. However, the incidence is double in patients with associated polytrauma ( ).
At 1 year from injury, 70% of patients with an initial ASIA ( Table 2 ) score A injury will remain A, while about 30% of them will show some signs of improvement. Around 14% will improve to B, 9.5% to C, 6.5% to D, while none will improve to ASIA E ( ; ). On the other hand, patients with incomplete SCI have a much higher spontaneous recovery ( ).
| ASIA scale | Description |
|---|---|
| A | COMPLETE. No motor or sensory function is preserved in the sacral segments S4-S5 |
| B | INCOMPLETE. Sensory but not motor functions preserved under the level of lesion. It includes S4-S5 |
| C | INCOMPLETE. Motor function is preserved below the neurological level and more than 50% of key muscles below the neurological level have a muscle grade less than 3 |
| D | INCOMPLETE. Motor function is preserved below the neurological level and at least 50% of key muscles below the neurological level have a muscle grade greater than or equal to 3 |
| E | NORMAL. Motor and sensory function are normal |
Unfortunately, at 1 year after time of injury, patients with complete cervical SCI had a mean recovery ranging from 9.0 to 14 motor score points( ), calculating as motor score (ranging from 0 to 5 per muscle group), the strength for each muscle group below the lesion level ( ).
Neurological improvement will typically show within the first 3 months and then it will enter a steady state ( ); even if in a little percentage of patients (about 9%) some little improvement can be showed even 5 years after injury ( ).
Natural history of patients with thoracic or thoracolumbar SCI
A complete neurological injury is reported ranging from 16.2% to 73.0% of patients with acute thoracic SCI ( ) and it is more frequent in patients with polytrauma ( ) ( Fig. 1 ).
At 1 year from injury, about 85% of patients with initial ASIA A will not improve, while about 15% of them will show 1 or more ASIA grade improvement. In patients with initial ASIA B, more than 80% of them will show some improvement ( ; ).
Substantially, acute thoracic SCI will improve less than cervical or thoracolumbar SCI ( ). In only 3.6% of patients with ASIA A grade at 1 year after injury, some minor neurological recovery can be recorded up till 5 years ( ).
Thoracolumbar fractures can be associated with conus medullary injury (fractures from T8-L2) and cauda equina injury (fractures below L1-L2) ( ).
Both syndromes are difficult to be distinguished one by the other. CMS is often characterized by a symmetric sensory deficits, bladder and bowel disfunction, and mild lower extremity weakness. CES is often defined by asymmetric sensory and motor deficits. In 20% of patients a complete lack of sensory and motor function will be present below the level of injury ( ).
Thoracolumbar SCI will show the same rate of neurological recovery of complete cervical SCI ( ) After 1 year from trauma, patients will experience a mean recovery of 4.5 motor score points below injury level ( ).
Surgical procedures
SCI are a wide spectrum of injuries, ranging from less to more severe spinal cord damage. For this reason, a singular approach to the spine is not correct and surgical choice should be individualized to each patient ( ; ). The main goals of treatment are fixation of instability and decompression of the spinal cord ( Fig. 2 ) and the choice of the correct surgical procedure is based on severity, level and mechanism of injury; location and extension of compression and surgeon preference.
Surgical approaches to the spine are classified as anterior or posterior. With both approaches stabilization and decompression can be achieved, but in more severe cases where a circumferential arthrodesis is needed, both approaches are combined together (staged or in single setting) ( ).
In cervical SCI, anterior approach is the most widely used allowing easily a ventral decompression and corpectomy, while a posterior approach is more appropriate for the thoracolumbar spine, where chest and abdomen represent an anatomical barrier.
In most cases, due to complex injury with disruption of anterior and posterior elements, anterior and posterior approach where combined together to perform a 360° arthrodesis.
Most common instrumentation devices used are pedicle screws with or without cement augmentation for thoracolumbar spine and pedicle or lateral masses screws for cervical spine. Usually, in acute traumatic SCI only one or two vertebral segments are involved and short segment stabilization is always preferred if possible. In flexion type injuries, posterior approach is usually preferred in the most of thoracolumbar injuries. In most cases, laminectomy, assure quick spinal decompression and also reduction with ligamentotaxis for thoracolumbar fractures ( ; ) ( Fig. 3 ).
How to define early versus late surgery post SCI?
Several articles have examined a different post injury range of time thresholds to define early versus late surgery. However, how much time can be considered “early” in not already clearly established. To recommend one of these thresholds and to choose the most favorable moment, two main principles must be considered ( ; ):
- (1)
efficacy (the extent of time in which surgery results in better outcomes).
- (2)
feasibility (the extent of time in which it is possible to perform surgery before the said limit taking into account the practical realities of the prehospital and hospital environment).
Which is the most efficacious threshold?
The theoretical objective of surgery is to begin a neuroprotective therapy performing a post injury treatment as soon as possible, preventing a secondary injury and favoring better recovery.
According to literature ( ), three common time thresholds can be found:
- (1)
ultra-early threshold (8–12 h post SCI).
- (2)
early threshold (24 h post SCI).
- (3)
late threshold (48–72 h post SCI).
Ultra-early threshold (8–12 h post SCI)
Jug et al. evaluated the neurological outcomes of 48 patients who underwent surgery before 8 h and between 8 and 24 h post-injury. After 6 months from injury, patients treated < 8-h showed a greater median improvement in ASIA motor score and a higher likelihood of improve of at least 2 AIS grade ( ).
Grassner et al. evaluated the impact of surgery on functional outcomes in 70 patients who underwent SD prior to 8 h at 1 year follow up. The Authors analysis showed that patients receiving surgery prior to 8 h had superior scores and better motor outcomes at follow-up ( ).
In another study, 48 patients were retrospectively categorized into three groups depending on the timing of surgery: ultra-early (< 12 h), early (12–24 h), and late (> 24 h). Authors found a mean significant improvement of 1.3 AIS grade in ultra-early surgery group as compared with the mean improvement of 0.5 of patients who underwent early surgery ( ).
Early threshold (24 h post SCI)
STACSIS highlight the role of early surgery in cervical SCI, showing greater neurological recovery, with 2 AIS grade improvement at 6 months of follow up ( ). On another study focused on thoracolumbar SCI, Rahimi-Movaghar et al. didn’t reach the same conclusion. In fact, despite the study lack some power, the difference between early and late surgery were not statistically significant ( ).
In the comprehensive study of Dvorak et al., early surgery for all anatomical level reached significantly greater motor recovery. However, the same effect was not demonstrated in complete SCI ( ).
In the Ontario-based cohort study, early surgery showed a higher likelihood of a 2 AIS grade improvement with a trend of additional improvement in motor recovery ( ).
It must be acknowledged that the 24 h cut-off is biologically arbitrary and it has been proposed for practical purpose; nothing changes between 23 and 25 h. So, when interpreting literature, it is important to remind that surgery is more effective when performed earlier but 24 h is only a threshold.
Late threshold (48–72 h post SCI)
Vaccaro et al. evaluated 64 SCI patients who received SD before 72 h after SCI or later than 5 days. At 1 year of follow up, the two groups didn’t show any statistically difference in AIS grade conversion and motor score recovery ( ).
McKinley et al., reported the result of a study with a large sample of 779 patients from Model SCI Systems database and divided patients on the basis of SD prior or post 72 h. Authors found shorter hospital stay and reduced respiratory complications in patients who underwent SD before 72 h; however, no difference was found for neurological recovery ( ).
Clohisy et al. evaluated 20 patients with thoracolumbar junction SCI. They found that patients surgically treated before 48 h showed grater improvements in neurological recovery than patients treated later. However, in this study patients who receive later surgery were treated about 2 months after injury ( ).
What threshold is feasible?
Despite the common objective is to promote early treatment, the reality of daily life trauma care, from prehospital support to emergency department access, carry on several barriers.
For many reasons, including hospital transport, patient stability and diagnostic delays, only 50% of patients would be eligible to undergo SD before 24 h while other 50% of patients, in most cases underwent SD between 24 and 48 h ( ).
The analysis of the CRHSCIR reported that in only 39% of cervical SCI and 45% of thoracic SCI, spine surgeons were able to perform SD before 24 h from trauma. Some Authors suggested that to improve early surgery rate, it is necessary to reduce barriers to early surgery in order to optimize patient outcomes ( ).
Despite about 90% of patients arrived at the site of definitive treatment within 6 h of trauma, only 50% of them are able to undergo surgical treatment within 24 h. Older age and intermediate stop in peripheral health centers, prior to arrival in specialized center, were important factors for delay of surgery ( ) ( ).
To support this findings, Furlan et al. reported that those patients who receive an early treatment (< 24 h) spent less time in intermediate center before the arrival to definitive center ( ).
In common practice, when patients access emergency department, they should be screened for any life threatened pathology, which must be treated first, since SCI is commonly associated with high energy trauma. For that reason, it is difficult to believe that most surgeries could be performed before 24 h from injury.
Does ESD offers the same benefit for all acute SCI?
SCI offers a wide spectrum of neurological impairment, from minimally to significant disabling, with a wide variability due to injury severity and neurological level of injury.
We will evaluate the current evidences about the efficacy of ESD in acute SCI based on level and severity of injury and time of surgical intervention.
Complete versus incomplete SCI
In literature, only few studies have examined the role of ESD in complete and incomplete SCI. Dvorak et al. evaluated 888 patients recruited in the CRHSCIR. In this study, attention was focused on the significant role of early surgery (< 24 h post SCI) on motor recovery and the Authors concluded as ESD was not associated with significant improvements in motor function. However, considering only patients with incomplete SCI graded as ASIA B-D, ESD was associated with an improvement of 6.3 points in motor score recovery at 6 months follow-up. As expected, no significant effect for ESD was observed in grade A patients ( ).
Bourassa-Moreau et al. examined a cohort of SCI. He found a 34% of AIS improvement of ESD (< 24 h) and 13% of improvement in late surgery (> 24 h), with even a higher difference for cervical SCI (64% versus 36%). Moreover, they didn’t observe any conversion in AIS grade for complete SCI between early and late surgery ( ).
More recently, Ma et al. analysed in their meta-analysis the effects of ultra ESD (< 8 h) on patients with acute SCI. He found more significant improvement in AIS score than in patients treated with early (8–24 h) or late (> 24 h) surgery. Patients had more benefits in neurological recovery from ultra ESD with no difference in hospital stay and rate of complications ( ).
On the other hand, ESD (< 24 h after injury) reduced hospital stay, especially for patients with complete SCI ( ).
All studies were in accordance regarding the benefits of ESD also for what concern the length of hospital stay for patients with complete SCI, while no other study support the benefit of ESD for incomplete SCI ( ; ).
Unfortunately, there are no large prospective studies that confirmed the superior effects of ESD on neurological outcomes for incomplete versus complete SCI. These findings are supported by the hypothesis that for incomplete SCI, the primary energy of injury is not so powerful to cause a complete SCI, and there may be greater potential for neuroprotection ( ) ( ).
Effects of ESD on different neurological level of injury
One of the most important factors in patients with SCI is the neurological level of injury, which can influence patients’ potential recovery ( ).
However, there are no many studies focused on specific neurological level and the effect of early or late surgery on neurological recovery. Commonly, cervical and thoracolumbar SCI are reported together and data are difficult to be extracted for each neurological level.
Effect of SD in patients with cervical SCI
STASCIS is the largest study involving patients with only cervical SCI ( ). Authors of this study analysed several cervical SCI undergoing either early (< 24 h) or late (> 24 h) SD and compared AIS grade changes at 6 months follow up. Both groups underwent at least 1 grade; however, patients treated with early surgery are more likely to improve AIS of 2 grade or more (odds ratio 2.57; P = .01), than patients who underwent late surgery. No differences between groups were found in term of complications, despite the trend is in favor of ESD (24% versus 30% respectively) ( ).
More recently, Aarabi et al. evaluated 72 patients with traumatic cervical SCI with AIS grade A, B or C. Patients were stratified on the basis of ultra-early (< 12 h), early (< 24 h) and late (> 24 h) surgery. Improvement of one grade or more was present in 55.6% of grade A, 60.9% of grade B, and 86.4% of grade C patients, but not in a significant manner. Authors also found other crucial predictive factors that could be more likely associated with injury recovery such as admission motor score and intramedullary lesion length ( ).
Effect of SD in patients with thoracic and thoracolumbar SCI
Rahimi-Movaghar et al. evaluated 35 patients with thoracic and thoracolumbar (T1-L1) SCI. Some underwent early (< 24 h) while other late (> 24 h) surgery. There was no difference between motor score recovery at 12 months of follow up, considering both complete and incomplete SCI ( ).
In the NACTN for SCI, researchers evaluated 86 patients with SCI and neurological injury between T1 and L1. Early surgery (< 24 h) was associated with additional seven points of ASIA motor recovery and a reduction of 60% in pulmonary complications ( ).
Effect of SD on miscellaneous SCI
Some studies reported cervical, thoracic and thoracolumbar SCI as a unique entity; we report them in this section since it is not possible to revise the results and divide them in anatomical region.
In the study of Bourassa-Moreau et al., patients treated with early surgical decompression (< 24 h) showed improved rates of AIS conversion among cervical AIS grade A, while the same was not reported for thoracolumbar trauma ( ).
The Ontario-based cohort study involved 84 patients with all levels of SCI. Patients treated surgically prior to 24 h didn’t show a significant increasing trend in motor recovery at rehabilitation discharge. Authors found the level of injury to be a significant predicting factor for neurological recovery, but they didn’t investigate if the effects of ESD vary with level of injury ( ).
In the study of Dvorak et al., despite the impact of surgery was not analysed, it appears that patients with incomplete SCI from all anatomical level benefit from ESD ( ).
The special case of Central Cord Syndrome
Central Cord Syndrome (CCS), the most frequent type of incomplete SCI, was first described by Schneider in 1954; it is characterized by involvement of the four limbs but with greater motor and sensitive deficits in upper extremities. Commonly, it is often secondary to low energy trauma especially in elderly patients where a pre-existing spinal stenosis ( ; ) ( Fig. 4 ).
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