Introduction
Spinal cord injury (SCI) is a devastating event for the affected individual who may, as a result, develop significant motor, sensory, and autonomic deficits. These losses often translate into significant functional impairments and substantially affect both the quality of life and life expectancy of patients. In addition, SCI patients may have a profound effect on, and place a significant burden on, their families and society. Indeed, according to the Centers for Disease Control and Prevention (CDC), in the United States, the average medical cost of SCI ranges between $15,000 and $30,000 per year with an estimated lifetime cost of $500,000 to more than $3 million, depending on the severity of injury ( http://www.cdc.gov/traumaticbraininjury/scifacts.html ).
Injury to the spinal cord may occur anywhere along its course and the site of injury will largely determine the level of postinjury function as well as influencing the risk of developing postinjury complications. Ultimately, the level of function attained after SCI is fundamentally dictated by the age of the patient, preexisting comorbidities, the etiology and extent of the SCI, as well as the timing of spinal cord decompression. Commonly, however, the management of SCIs is further complicated by accompanying associated injuries to the appendicular skeleton related to the mechanism of injury (e.g., motor vehicle accidents [MVAs], falls, and blunt trauma). Such injuries can influence the timing of surgical decompression of the spinal cord and thereby significantly affect the overall level of functional recovery.
This chapter will review the issue of timing of decompression and surgical fixation of the injured spinal column in patients with a SCI. In the discussion, we will consider the initial management of the patient from the time of injury and how management in this early period presents an opportunity to profoundly influence the ultimate neurological recovery and functional outcome. At the center of this discussion will be the recently published Surgical Timing in Acute Spinal Cord Injury Study (STASCIS) trial results. Although the period from initial injury to definitive hospital management is often considered separate, it is important to emphasize that there are many opportunities, even at this stage, to influence the ultimate outcome in both positive and negative ways.
Later in the chapter, we will also discuss focused considerations of surgical timing in patients with SCI in the setting of multitrauma and thoracic SCI, as well as controversies surrounding the timing of management of patients with a traumatic central cord injury. In addition, the evidence for the current recommendations will be explored.
Finally, we will discuss evolving and exciting new treatment strategies that have the potential to be translated into clinical practice. As will be seen throughout the chapter, however, substantial research remains to be done in all of these areas and much of the current medical practice remains at the discretion of clinical experience.
Epidemiology
Incidence
Incidence rates of SCI provide an opportunity to assess the efficacy of prevention strategies as well as technologies such as seatbelts, airbags, and impact-reduction technologies aimed at decreasing the occurrence of such injuries. Wyndaele and Wyndaele attempted to investigate the incidence around the world via a literature survey looking at data from 1995 onward; however, the analysis of their findings was limited by the lack of uniformity in methodologies used by various authors. Nevertheless, their estimated incidence of SCI globally was between 10.4 and 83 per million inhabitants per year. Tetraplegia constituted one-third of these injuries and half the SCI injuries were complete lesions. The mean age was 33 years old and males outnumbered females by 3.8 : 1. It is worthy of note that the age distribution of traumatic SCI appears to be bimodal, with peaks in young adulthood attributable most notably to MVAs, and in elderly patients aged 65 years and older attributable chiefly to falls.
Although a lack of concrete incidence rates does not affect the management of medical intervention, its scarcity hinders the evaluation of preventive measures aimed at reducing traumatic SCI rates. Furthermore, data that are available are likely to underrepresent the actual incidence rates of SCI due to the nature of the traumatic events resulting in these injuries, which carry a high prehospital fatality rate. Indeed, Wilson and colleagues state that, in the Canadian population, an additional 20% of traumatic SCI patients die before arrival to the hospital.
Prevalence
Prevalence rates are difficult to determine from the available literature. It is believed that there are currently 2.5 million individuals living with SCI (International Campaign for Cures of Spinal Cord Injury Paralysis website: http://campaignforcure.org ). Wyndaele and coworkers reported the results of four studies from Australia, Sweden, Finland, and the United States indicating a prevalence rate in these countries between 223 and 755 per million, with higher rates seen in the United States and Australia. It is important to note that these data do not necessarily reflect the prevalence in developing countries, and the populations of Europe, United States, and Australia only constitute approximately 20% of the world’s population. Therefore the true global prevalence of SCI remains unknown. The prevalence of SCI is an important statistic as it gives an indication of the burden of SCI on health care and social security resources. Calculations by O’Connor forecast an increase in incidence and prevalence of SCI with more cases seen in the elderly and a profound increase in the number of patients with incomplete tetraplegia. Again the data available for these calculations are scarce and the true global prevalence is unknown.
There are significant and increasing costs associated with SCI, and there are indications that these costs are rising. This was recently highlighted by Baaj and colleagues in a cost analysis demonstrating a significant increase in the cost from $500 million in 1997 to $1.3 billion in 2006, an increase of 160%.
Spinal Cord Injury Pathomechanics: Current Opinion
During a traumatic event involving the spine, numerous anatomical changes may occur including fracture of bony structures, as well as dislocation of facet joints that compress and/or damage the cord or are involved in disrupting sufficient arterial perfusion. The severity of these changes and the time to medical intervention dictate the extent of neurological and functional loss.
There is a widely held belief by most surgeons treating spinal injuries that ongoing compression of the spinal cord should be addressed as a matter of high priority and urgency. Central to this widely held opinion is a relatively recent appreciation that the initial traumatic event is only partially responsible for the total impact of an SCI that determines long-term functional recovery.
Traumatic SCI can be broken down into two stages of injury: primary injury resulting from the insult of the traumatic event, and secondary injury that represents the cascade of inflammatory and biochemical events subsequent to the primary injury resulting in tissue damage (see Fig. 32-3, A ). If left unchecked and uncorrected, secondary injury will progress and cause significantly more tissue damage and neuronal loss than initially incurred from the primary mechanical insult. Secondary injury involves a perpetuating process of ischemia, edema, increased excitatory amino acids, and lipid peroxidation ( Fig. 32-1 ).
In a recent systematic review, it was concluded, based on assimilating the available preclinical and clinical literature combined with a modified Delphi process, that decompression via surgery should be performed within 24 hours when medically feasible. This is also reflected in the results of the STASCIS trial, two studies of international spinal surgeon opinions, and a study currently underway in which the timing of early decompression is defined as less than 12 hours. The latter study is attempting to address the potential biases of a prospective observational multicenter comparative cohort study by applying a rigorous and well-defined protocol. These authors have published their study protocol and intended analysis methods. The planning and organization along with accurate power calculations is likely to yield a highly significant contribution to the growing body of knowledge regarding timing of decompression and stabilization in SCI.
Preclinical and Clinical Evidence
A considerable body of preclinical data has now been accrued regarding the timing of decompression of acute SCIs. In these preclinical studies, a variety of animal models and compression models have been employed. A recent high-quality study employed a dog model comparing (1) intravenous (IV) methylprednisolone and decompression at 6 hours, (2) IV saline and decompressive surgery at 6 hours, or (3) IV methylprednisolone alone. The surgically treated animals experienced significantly better neurological recovery at 2 weeks postinjury than the nonsurgically treated animals, independent of steroid administration.
In a recent systematic review of the evidence available for preclinical data, Furlan and colleagues state there is a biological rationale to support early decompression of the spinal cord. In addition, the evidence suggests that early decompression is safe and feasible. These authors identified 19 preclinical studies of sufficient quality to be included in the review. Eleven of these studies indicated a time-dependent effect of spinal cord compression on the behavioral recovery, spinal cord blood flow disturbances, electrophysiological recovery, and histopathological characteristics of the lesion.
Treatment Strategies and Timing
Treatment of the patient with an acute SCI begins at the scene of the injury. Early emergency treatment of the patient is a vital step in limiting further primary and secondary SCI. The medical management of the patient, with particular attention to cardiopulmonary resuscitation, is central to this aim. The maintenance of adequate blood pressure and oxygenation gives the delicate spinal cord tissue the greatest chance of avoiding or minimizing secondary injury.
Accepted and well-practiced protocols to avoid further SCI in the process of retrieval and transportation should be employed and regularly scrutinized. The American Association of Neurological Surgeons and Congress of Neurological Surgeons (AANS/CNS) Joint Guidelines Committee introduced the updated Guidelines for the Management of Acute Cervical Spine and Spinal Cord Injury in 2013. This publication gives an extensive and up-to-date review of the accepted guidelines for the management of patients with acute SCI ( Table 32-1 ).
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In addition to the acute emergent care of the patient with SCI, there has been a focused attempt to find treatment strategies that not only limit the degree of primary injury, but also potentiate the chances of recovery through repair and regenerativion. This has not been a simple process and the task of unraveling this complicated problem has been made more difficult by the variability in the quality of research on this topic. Long-held beliefs based on anecdotes and opinions have been difficult obstacles to approach and overcome.
Efforts by investigators to demarcate early and late surgical treatment into time frames have been hindered by the incongruence of findings between them with regard to outcome. However, considering practicality as well as current evidence, including that of the STASCIS trial, it seems most reasonable to define early and late surgical decompression as less than 24 hours and more than 24 hours, respectively. Henceforth, the timing of management of SCI has been broken down into the following: within the first hour, within 24 hours, and longer than 24 hours after injury.
Early Management (Less Than 1 Hour): Maintaining and Optimizing Physiological Homeostasis
It is clear that first aid is the primary medical intervention that needs to be employed at the site of any traumatic injury. If significant blunt trauma is suspected, or localized trauma involving the spine has occurred, immobilization of the spine must be performed to stabilize the patient and prevent further injury. Depending on the tools at disposal on the scene, this may either be achieved through manual spinal protection, or utilization of a cervical immobilization device along with placing the patient on a rigid backboard.
The assessment of vital signs, including hemodynamic and respiratory status, as with any first aid response must be performed expeditiously. However, traumatic SCIs demand even more vigilance in this regard as high-level spinal injuries frequently present with significant neurogenic shock and accompanying hypotension and bradycardia. Furthermore, if SCIs are suspected, maintaining high oxygenation may be crucial in minimizing secondary injury at sites of spinal cord compression ( Table 32-2 ).
| Immobilization of the Spine |
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| Hemodynamic Support |
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| Respiratory Support |
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Surgical and Nonsurgical Management (Less Than 24 Hours): Spinal Cord Decompression
Regardless of whether or not the patient is a surgical candidate for correction of SCI, nonsurgical management must still be employed immediately after the patient has been immobilized and transferred to an acute medical care facility. This management entails preventive care such as bedsore and Cushing ulcer prophylaxis as well as assessment for possible closed reduction of the spine ( Table 32-3 ).
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The emphasis of treatment beyond stabilizing the patient is on spinal cord decompression. Imaging via magnetic resonance imaging (MRI) or computed tomography (CT) to evaluate the extent of injury generally precedes any intervention and allows for the assessment of potential candidacy for closed reduction and/or surgical decompression and instrumented fixation.
Spinal cord decompression, reconstitution of the spinal canal, and rigid stabilization of the injured as well as unstable spinal segments is the aim of initial surgical management. Ongoing spinal cord compression from a disrupted and unstable spinal segment is a potent stimulus for the initiation of secondary injury. More often than not, the injured segment is also highly unstable and, with the need to transfer and transport the patient, there is a real risk of ongoing additional primary injury insults to the spinal cord through motion at the disrupted level in the setting of significant canal volume reduction.
As mentioned, decompression of the spinal cord can be achieved by closed or open means. If a unilateral or bilateral facet dislocation is present, then attempts may be made to reduce this by closed means. The need for a prereduction MRI is a highly debated topic and there are currently no clear guidelines to address this issue. This is a considerable gap in the knowledge, as unnecessary acquisition of imaging would critically delay the timing of treatment. There are currently no prospective cohort studies of patients with cervical SCI resulting from facet fracture-dislocation treated with or without prereduction MRI. A study of this type would ultimately offer clearer guidance, evidence in support of treatment recommendations, and possibly shorten the time to decompression. There may be significant delays before an MRI can be obtained, and the MRI scan is also time consuming. In addition, there are significant risks of further injury to the spinal cord in the process of transferring the patient to and from the MRI scanner. A number of adequately trained personnel are required for this maneuver and the team must be reassembled once the procedure is completed. There are significant delays inherent in this process and currently there is no evidence to suggest there is any significant benefit even if a disc lesion is identified.
There is also currently no prospective comparative study of closed reduction versus anterior decompression and stabilization for patients with MRI-documented herniated discs in association with unreduced cervical fracture-dislocation injuries. A study of this type would provide class II medical evidence in support of a treatment recommendation.
If closed reduction fails, there is a complex fracture pattern, disc or bone material in the canal, or other circumstances that preclude closed reduction, then proceeding to open reduction is indicated.
The role of early reduction of facet joint dislocation is difficult to investigate and is not amenable to investigation with a randomized clinical trial. There are case reports in the literature that do give some insight into the potential benefit of undertaking early closed reduction. Collision sports are associated with traumatic cervical injuries and, in particular, facet dislocations resulting in SCI. In 2011, Newton and colleagues reported on a series of patients who sustained cervical spine dislocations playing rugby. Thirty-two patients presented with complete paralysis. Eight patients had reductions performed within 4 hours and, of these, five patients made a full recovery. In the patients who underwent reduction after 4 hours, only one made recovery that was considered useful. The subgroup of patients with SCI secondary to facet dislocation has been recognized as a possible cohort with significant recovery potential.
A recently published multicenter cohort study demonstrated that patients with facet dislocation in association with SCI presented with a greater severity of neurological deficit and the injuries were associated with a higher energy mechanism. Bilateral facet dislocation was associated with a more profound neurological deficit than unilateral facet dislocation as reflected in the American Spinal Injury Association (ASIA) impairment scale grade and ASIA motor score ( Table 32-4 ). At 1 year, with baseline neurological differences taken into account, patients with facet dislocation and SCI experienced a smaller amount of motor recovery compared with patients without facet dislocation. Moreover, patients with SCI associated with facet dislocation also had a longer duration of hospital stay and these outcomes occurred despite having decompression performed significantly sooner than patients without facet dislocation (25.1 hours vs. 41.3 hours, respectively). Ongoing investigation by these authors is also taking place to determine the relationship between time to reduction in patients with facet dislocation and SCI and neurological recovery.
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