Use and Timing of Spinal Surgery

July 1999 Volume 91 Number 1

Clinical Articles

Charles H. Tator, M.D., Ph.D., Michael G. Fehlings, M.D., Ph.D., Kevin Thorpe, M.Math. and Wayne Taylor, M.A.

Division of Neurosurgery and Spinal Program, Toronto Western Hospital and University of Toronto, Toronto, Ontario, Canada; and Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada

OBJECT. A multicenter retrospective study was performed in 36 North American centers to examine the use and timing of surgery in patients who have sustained acute spinal cord injury (SCI). The study was performed to obtain information required for the planning of a randomized controlled trial in which early and late decompressive surgery are compared.

METHODS. The records of all patients aged 16 to 75 years with acute SCI admitted to 36 centers within 24 hours of injury over a 9–month period in 1994 and 1995 were examined to obtain data on admission variables, methods of diagnosis, use of traction, and surgical variables including type and timing of surgery.

A total of 585 patients with acute SCI or cauda equina injury were admitted to participating centers, although approximately half were ultimately excluded because they did not meet inclusion criteria. Common causes for exclusion were late admission, age, gunshot wound, and absence of signs of compression on imaging studies. Thus, only approximately 50% of patients with acute SCI would be eligible for inclusion in a study of acute decompressive surgery. Although all patients underwent computerized tomography (CT) scanning, only 54% underwent magnetic resonance imaging, and CT myelography was performed in only 6%. Complete neurological injuries (American Spinal Injury Association Grade A) were present in 57.8%. Traction was applied in only 47% of patients who sustained cervical injury, in whom decompressive traction was successful in only 42% of cases. Neurological deterioration occurred in 8.1% of cases after traction. Surgery was performed in 65.4% of patients. The timing of surgery varied widely: less than 24 hours postinjury in 23.5%, between 25 and 48 hours postinjury in 15.8%, between 48 and 96 hours in 19%, and more than 5 days postinjury in 41.7% of patients.

CONCLUSIONS. These data indicate that although surgery is commonly performed in patients with acute SCI, one third of cases are managed nonoperatively, and there is very little agreement on the optimum timing of surgical treatment. The results of this study confirm the need for a randomized controlled trial to assess the optimum timing of decompressive surgery in SCI.

KEY WORDS. acute spinal cord injury, timing of surgery, multicenter clinical study

THE Surgical Treatment for Acute Spinal Cord Injury Study (STASCIS) group was formed in 1992 by the Spinal Cord Injury Committee of the Joint Section on Neurotrauma and Critical Care of The American Association of Neurological Surgeons (AANS) and Congress of Neurological Surgeons (CNS), the two largest neurosurgical specialty organizations in North America. In 1996, STASCIS was joined by the Joint Section on Spinal Disorders and Peripheral Nerves of The AANS and CNS. The principal aim of the STASCIS group was to conduct a randomized prospective controlled trial to examine the role and timing of a decompressive intervention for the treatment of the spinal cord and cauda equina after acute spinal cord injury (SCI).

In the present paper we describe the methodology and results of the first STASCIS, the aim of which was to assess, retrospectively, the use and timing of spinal surgery for acute SCI in North America. This information was sought by the STASCIS group to design a protocol for a randomized, prospective trial of decompressive surgery after acute SCI. The study was conducted in 1994 and 1995 in 36 North American centers. Although numerous individual surgical series were available from the literature, 5, 35, 36, 39, 48, 54, there were very few studies in which an overall analysis of the use and timing of surgery in acute SCI in more than one center was provided, especially with respect to surgical decompressive procedures. Exceptions to this were the NASCIS–1 and NASCIS–2 10 – 12, reports that provided some information on the use of surgery, although important issues such as the exact type of surgery performed were omitted. 26,

Clinical Material and Methods

The clinical coordinating center for this study was the Division of Neurosurgery at the Toronto Hospital, University of Toronto, Toronto, and the statistical center was the Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, both located in Ontario, Canada. Specific reporting forms were developed for the recording of individual patient data.

Participating Investigators and Participating Centers

Through advertisements in The AANS and CNS newsletters and through membership on the Spinal Cord Injury Committee, 36 of the major SCI centers in North America were recruited into the study, as shown in Table 1, including 32 United States and four Canadian centers. There was a very wide, representative geographic distribution, as well as a mixture of teaching and nonteaching hospitals.

Study Format

The participating investigators were asked in the fall of 1995 to record information retrospectively for all patients with spinal cord or cauda equina injuries admitted to their centers within 24 hours of injury during the 9–month period from August 1, 1994 to April 30 1995. Specific questions were posed to determine whether the patients would have been eligible for a planned trial of decompressive surgery according to a specific protocol that had been developed by STASCIS. This protocol would theoretically include all patients with SCI or cauda equina injury at all vertebral levels that were neurologically complete (American Spinal Injury Association [ASIA] Grade A) and incomplete (ASIA Grades B–D) injuries. Investigators were asked to evaluate whether each patient would have conformed to specific inclusion criteria (Table 2) that were almost identical to those used in the previous NASCIS protocols with respect to age, medical risk factors, and other variables 10 – 12, and to "predict" retrospectively whether each patient would have been able to provide informed consent. In this way, we attempted to evaluate the features of the planned protocol for a randomized, prospective trial.

The number of cases reported by each center was controlled by each center's participating investigator. There was no independent observer in the centers to verify the completeness of the capture of cases. Each center bore the costs of its own data collection.

Results

Table 1 shows that 585 patients with acute SCI or cauda equina injury were admitted to the 36 centers during the 9–month study interval. The maximum number of patients admitted to a single center was 104 and the minimum was four. The variable number of cases submitted by the centers probably reflects the number of cases available and the ability of centers to submit data without the help of externally funded data collection personnel. The overall mean patient age was 40 years.

Vertebral Level of Injury

Overall 64.6% of the spinal injuries were cervical (C1–7), 18.7% thoracic (T1–11), 11% thoracolumbar (T11–L2), and 5.6% were lumbosacral (L2–S5) (Table 3). At some centers there was a much higher incidence of cervical injuries, most likely because of the greater involvement in those centers of orthopedic spinal surgeons, who had more responsibility for managing patients with noncervical injuries.

Severity of Neurological Injury: ASIA Grade

Based on the ASIA neurological grading system, 2, 42.2% of the injures were Grade A (complete SCI), 9.7% were Grade B, 22.4% were Grade C, and 25.5% were Grade 4 (Table 3). In general, the distribution of ASIA grades was similar among the various centers, although some centers appeared to receive an unusually large percentage of patients with complete injuries, whereas other centers treated a higher percentage of patients with incomplete injuries.

Inclusion and Exclusion Criteria

Based on the inclusion and exclusion criteria (Table 2), 62.1% of the 550 patients for whom this information was available met the inclusion criteria on admission and would have been eligible for consideration for the planned study, whereas 37.1% would have been excluded (Table 4). The most frequent reasons for exclusion were admission after 24 hours postinjury, age, and the presence of gunshot wounds (Table 4). The absence of cord compression, as judged by evaluating available imaging studies at admission, would have excluded 18 patients, and cases in which there was a concomitant head injury would have excluded another 18 patients. It should be noted that absence of cord compression as determined by imaging studies performed after admission resulted in the exclusion of many additional patients at a later stage.

Provision of Consent

It was the opinion of the staff at the participating centers that 510 (89.8%) of the 568 patients for whom this information was available would have been able to consent to participating in the study, whereas 58 (10.2%) would not have been able to provide consent. These latter patients included those who had sustained head injuries, those in whom excess alcohol was present, and those for whom other factors prevented the provision of informed consent.

Imaging Studies

Although all patients underwent computerized tomography (CT) scanning, only 54% underwent magnetic resonance (MR) imaging (Table 3). As expected, CT myelography was infrequently performed (6%). The use of MR imaging varied significantly among centers: some obtained MR images in 90% of cases or more, whereas others obtained them in only 10 to 20% of cases.

Overall Inclusion Rate Based on Imaging and Admission Eligibility

Of 459 patients for whom data were available regarding the presence of cord compression or deformation as determined by imaging studies performed prior to traction, in 303 cases (66%) cord compression or deformation was demonstrated, whereas in 156 patients (34%) none was revealed. Thus, if the planned prospective study included only those patients who met all the inclusion criteria outlined in Table 2 and who were not excluded for any of the reasons listed in Table 4 (omitting the 18 patients in whom cord compression was not demonstrated on admission and who would have been excluded based on their imaging studies), the eligibility rate would be 66%. By multiplying the rate of imaging study–confirmed spinal cord compression (66%) by the rate of potential eligibility (66%), one can deduce an approximate overall inclusion rate of 44%. It is likely that this figure reflects a slight underestimation of the true inclusion rate, because some patients may have been excluded based on more than one criterion. Accordingly, we estimate a true inclusion rate of approximately 50% based on the available data in this study.

Decompressive Traction

Of the 173 cases of cervical injury in which information was available about the use of traction, traction was used in 47%. In the opinion of the participating investigators, spinal cord deformation persisted after traction in 43% of cases in which it was applied. The participants were asked to indicate if neurological deterioration occurred during traction, and they reported neurological deterioration during traction in 14 patients (8.1%). Information was not available regarding the severity of neurological deterioration and whether the deficits were temporary or permanent.

Surgical Treatment: Incidence, Type, and Timing

Information was requested on the use of surgical treatment in these 585 cases, and information was available for 583 cases, 65.4% (381) of whom underwent surgery and 34.6% (202) did not. Decompressive surgery was performed in 68.2% of the operations, whereas fusion was performed in 85.7%. The majority of the patients underwent both surgical procedures. Data on the timing of surgery were available in 374 of the 381 surgical cases. Surgery was performed at 24 hours or less after injury in 23.5% (88 patients), between 25 and 48 hours after injury in 15.8% (59 patients), between 48 and 96 hours after injury in 19.0% (71 patients), and 5 days or more after injury in 41.7% (156 patients) (Table 5).

Discussion

The epidemiological features of these patients in terms of age, level and severity of injury, and other admission variables were similar to other reported populations of patients with SCI. 32, 33, 47 49, 51, For example, in this trial approximately two thirds of the patients had sustained cervical injuries and approximately 60% had sustained incomplete neurological injuries; these figures are in keeping with other large series of spinal cord–injured patients admitted to SCI units in North America where neurosurgeons play a significant role.

This retrospective study was undertaken in an attempt to define the feasibility of conducting a prospective randomized controlled trial of the timing and effectiveness of decompressive surgery after acute SCI. Although pharmacotherapy in which methylprednisolone is used has been proven to be effective in improving neurological deficits in patients with acute SCI, the results of the North American 12, 13, and Japanese 41, trials in large numbers of patients have shown only a minimum amount of improvement. Modest neurological improvement was also observed when treating patients with GM–1 ganglioside in a trial in a small series. 30, Thus, further studies of other drugs and other treatments must be undertaken to enhance the neurological recovery. There is evidence from experimental studies in laboratory models that early decompression improves neurological recovery.

We recently conducted an evidence–based review of the literature to evaluate critically the rationale as well as indications for and timing of decompressive surgery for the treatment of acute, nonpenetrating SCI. 29, Although there is biological evidence (as will be briefly summarized) from experimental studies in animals to indicate that early decompressive surgery may improve neurological recovery after SCI, the relevant interventional timing in humans remains unclear.

There is evidence from experimental studies in laboratory models that early decompressive surgery improves neurological recovery. 8, 15, 17, 19, 21, 23, 31, 34, 40, 45, 46, For example, in the laboratory of one of the authors (C.H.T.), the removal at 2 hours of an extradural clip that was compressing the cord produced better recovery than removal at 4 hours. 31, The findings of some clinical studies in patients have shown promising results after decompressive surgery, 6, 56, 57, although in other studies no benefit has been shown from early decompressive surgery when compared with that performed at later times. 5, 26, 35, 36, 39, 52 – 54, The results of several studies have failed to show that patients who underwent surgery made improved recovery compared with those undergoing nonoperative therapy. 24, 48, 55, For example, in a study by one of the authors (C.H.T.) the outcome in 116 patients who received operative (decompressive in 75 and fusion in 41) treatment was compared with 92 who did not, and there was no difference in neurological recovery. 48, However, it should be noted that, with one exception, none of these studies was a randomized controlled trial in which patients were allocated to surgical or nonsurgical or to early– or late–surgery groups. The exception to these studies was the study by Vaccaro, et al., 52, reported in 1997, in which patients were randomly allocated to an early– or late–surgery group. The authors studied only a small number of patients: the early–surgery group, defined as those in whom surgery was performed within 72 hours of injury, contained 34 patients (mean time to surgery 1.8 days); and the late–surgery group, defined as those undergoing surgery more than 5 days after injury, contained 28 patients (mean time to surgery 16.8 days). There was no difference in neurological outcome between the two groups. The other shortcoming in this study was the small number of patients who underwent follow–up review (approximately one third were lost to follow up).

In several other studies improved neurological outcome has been reported after late decompressive surgery days, weeks, or months postinjury, 3, 7, 9, 14, 22, 35, 37, but none of these studies was a randomized controlled trial. Traction has also been reported to improve neurological outcome, especially if applied early, 1, 16, 18, 44, but none of the studies in which this finding was reported was a randomized controlled trial. However, in several studies there was no neurological benefit associated with anatomical reduction procedures, 20, 33, 55, with the possible exception of patients with bilateral facet dislocation. 4, Furthermore, early anatomical reduction before the patient undergoes imaging studies has become controversial because neurological deterioration has been reported after traction, primarily in patients with large disc herniations. 25, 27, It should be noted that in the present study we found an 8% rate of neurological deterioration due to traction. Unfortunately, data are not available regarding the severity and permanence of these deficits.

One apparent factor in our study was the lack of a consistent imaging protocol to visualize the extent of spinal cord compression. Only 54% of patients with an acute SCI underwent MR imaging in this multicenter study. As recently reported by our group, 28, 42, CT study, when performed alone, can sigfnificantly underestimate the extent to which the spinal cord is compressed. It is essential to develop consistent and accurate imaging protocols to quantify the extent and severity of spinal cord compression. The STASCIS group has recently developed and validated a simple, quantitative technique used to assess spinal cord compression on midsagittal T2–weighted MR images. 28,

In the present study, we found that currently in North America approximately 66% of patients with acute SCI are being treated with surgery, and as previously noted, there is no definitive proof that the treatment leads to improved neurological recovery. It should be noted that many authors claim that surgery enhances early mobilization and reduces length of hospital stay, but there is no definite proof. Furthermore, the effect of surgery, especially early surgery, on the rate of complications such as pneumonia or deep venous thrombosis is controversial. 38, 58,

In the present study we found a lack of consensus among centers concerning the optimum timing of surgical treatment, and only a minority of patients underwent surgery within 24 hours of trauma. Even surgery performed within this interval may be too late to reverse some of the secondary injury mechanisms identified after SCI. 50, The only therapeutic window established in humans is the 8–hour trauma–to–treatment window reported in the NASCIS–2 in which methylprednisolone was used. 12,

According to our findings, only approximately 50% of patients currently admitted to spinal cord centers in North America would be eligible for inclusion in a randomized controlled trial of early compared with late decompressive intervention by traction or surgery. This was based on inclusion of only those cases admitted within 24 hours of trauma. Thus, a randomized trial in which an early decompressive procedure was performed at a shorter therapeutic window time, such as the 8 hours established in the NASCIS–2, would require a public education campaign and specific instructions to first–aid personnel and emergency physicians to encourage much earlier referral to spinal treatment centers.

Acknowledgments:

The authors are grateful to Sandi Amaral for her assistance in manuscript preparation.

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Manuscript received November 24, 1998.
Accepted in final form April 30, 1999.