Effect of Timing on Decompression and/or Stabilization Surgery Post SCI
Surgical timing has been one of the most eagerly studied clinical questions in acute SCI. Generally, the current treatment paradigm states that acute traumatic SCI can involve the acquisition of secondary injury due to ongoing compression, ischemia, inflammatory cascades, vascular phenomena or immune response. As such, it is thought that early correction of ongoing compression and/or instability would limit these processes and produce a favourable neurological outcome. For these reasons, there has been a presumption that earlier surgery is superior; there has therefore not been appropriate clinical equipoise for randomized studies of surgical timing.
The pertinent details relevant to surgical timing tend to relate to whether the individual has residual neurological function that is salvageable with surgery. Individuals with an incomplete SCI are therefore seen as a more emergent surgical problem, although Bourassa et al. (2013) demonstrate that individuals with motor complete SCI can also benefit from early surgery. In addition, the presence of ongoing mechanical compression of the spinal cord is seen as another inherently emergent problem, and one that is generally not specified in the studies reviewed here.
Most of the notable studies on surgical timing use a dichotomized analysis, for example within 24 hours of injury or after. Some studies use a 72 hours cut-off and this distinction must be kept in mind when comparing different results.
Discussion
An earlier retrospective analysis performed by Mirza et al. (1999) compared neurological and functional outcomes of individuals treated at one hospital versus another, each with a different policy for surgical timing (within 72 hours versus after 72 hours). Of note, all individuals received immediate closed reduction/decompression, with the late surgery group then waiting a period of 10-14 days before surgery. In this group, early surgery was associated with better American Spinal Injury Impairment Scale (AIS) motor score improvement as well as Frankel grade improvement. This study was limited by the fact that the two institutions could have varied in a number of other ways. Furthermore, every individual received immediate closed reduction suggesting that a process in addition to mechanical decompression may be occurring that confers neurological benefit with surgery.
Two Canadian multicentre studies demonstrated an association of early surgery with neurological recovery. Wilson et al. (2012) demonstrated an improvement in AIS Grade conversion and AIS motor score improvement using a 24-hour time cut-off for surgery. Similarly, Fehlings et al. (2012) published the c trial (Surgical Timing in Acute Spinal Cord Injury Study) using the same time cut-off in a prospective population of cervical SCI. They also reported a higher grade of AIS conversion at 6 months, as well as fewer complications, in the early surgery group.
Despite the overwhelming, positive outcomes associated with early surgery, the literature does have some heterogeneity. For example, Liu et al. (2016) reported that in their retrospective review, early surgery individuals (<72 hours) had a higher rate of neurological deterioration and mortality, thus arguing for the relative safety of delayed decompression.
Other than neurological outcomes, early surgery is supported in several other dimensions. According to Furlan et al. (2016), early surgery is more cost effective when considered in terms of complications and length of stay. Mac-Thiong et al. (2012) reported comparable results, with early surgery favouring lower complications, shorter length of stay and less overall cost. Similarly, higher medical and postoperative complication rates were found in the late surgery group identified by Bourassa et al. (2013), even despite higher numbers of motor complete injuries in the early group, whom are prone to such complications.
Because one of the rationales for early surgery involves protecting salvageable neural tissue, the role of surgical timing in motor complete injuries is not entirely clear. In their prospective cohort study, Bourassa (2016) demonstrated a statistical difference in AIS grade improvement in a population of individuals with motor complete SCI when dichotomized into early (34%) versus late surgery (13%). Similarly, the same group showed that the above-mentioned advantage in terms of complications and length of stay may also apply to cohorts of motor complete individuals.
Three systematic reviews have been published on surgical timing in acute SCI. La Rosa et al. (2004) conducted a meta-analysis comparing early surgery (defined within 24 hours) versus late surgery versus no surgery. They concluded that early surgery was superior to both other options, in subsets of both motor complete and incomplete injuries. One challenge is that this meta-analysis uses the loosely defined outcome measure “neurological improvement rate,” which is heterogenous and difficult to interpret across studies. The systematic review of Liu et al. (2016) reached similar conclusions regarding motor outcome and found superiority of early surgery regarding length-of-stay and complication rate, but not reduction in mortality. The systematic review of van Middendorp et al. (2013) reached similar conclusions as the other reviews and relayed the continued methodological limitations of included studies. Interestingly, using a funnel plot analysis, the authors found evidence of publication bias in the surgical timing literature but note that equipoise for prospective randomized studies does not exist.
Conclusion
There is level 3 evidence (based on several case control studies) that surgery within 24 hours of injury leads to improved neurological outcomes, shorter length of stay, and fewer complications, but not a reduction in mortality after acute, traumatic SCI.
