The influence of the energy of trauma, the timing of decompression, and the impact of grade of SCI on outcome.

STUDY
DESIGN: Retrospective cohort study.
OBJECTIVES: To find out: (1) if the energy of trauma (high and low) influence the outcome after cervical spinal cord injury; (2) if time to decompression and degree of injury (complete and incomplete) influence the outcome after high- and low-energy cervical spinal cord injury.
METHODS: Twenty-one consecutive patients with low-energy cervical spinal cord injury were identified from the spinal injuries unit database (eg, ball sports, diving, surfing, and falls). Twenty-one aged-matched patients with high-energy cervical spinal cord injury (eg, motor vehicle trauma) were then randomly selected and the groups were compared. All patients had formal American Spinal Injuries Association assessment on admission and at 6 months.
RESULTS: At the 6-month follow-up, the energy of the initial trauma was not found to influence the neurological outcome (P = .76). Early definitive intervention (<8 hours) for patients with incomplete cord lesions was shown to significantly affect outcome (P = .049). As expected, patients with an incomplete spinal cord injury at presentation showed significantly greater neurological improvement at follow-up compared with those with complete injuries (P = .006).
CONCLUSIONS: We were unable to find a correlation between the energy of the initial trauma causing a spinal cord injury and the neurological outcome. Early definitive decompression improved outcomes for patients with spinal cord injury, especially those with incomplete spinal cord injury. [Table: see text] The definiton of the different classes of evidence is available on page 55.

Study Rationale and Context

Animal studies have shown that the rate, depth, and duration of spinal cord compression influence neurological prognosis.1,2,3,4 The role of surgery in improving neurological recovery remains controversial. There is emerging clinical evidence that early decompression (<24 hours) improves neurological outcome.5,6,7,8,9 Experimental evidence advocates decompression within 8 hours.10

Objectives

To find out: (1) if the energy of trauma influence the outcome after cervical spinal cord injury (SCI); (2) if timing to definite decompression influence the outcome after cervical SCI.

Methods

Retrospective cohort of patients treated for acute traumatic cervical SCI.

Low energy: acute traumatic cervical SCI from rugby, diving, surfing, and low-height falls.

High energy: acute traumatic cervical SCI from motor vehicle trauma.

Central cord syndrome; no evidence of fracture or dislocation; coexisting significant head injury resulting in neurological impairment of the limbs. Nontraumatic causes of SCI/compression.

The Princess Alexandra Hospital has an acute spinal cord trauma service and houses the Australian State of Queensland's SCI center on one campus.

Over a 5-year period, 21 consecutive patients with low-energy cervical SCI admitted to the Spinal Injuries Unit were identified using the Spinal Injuries Unit Database.

Patients for the low-energy cohort were age matched to within 3 years from the 139 cases of high-energy acute cervical traumatic SCI patients admitted during the same period. In cases of more than one appropriate match the high-energy cohort patient was selected using the “names from a hat” technique.

All the patients underwent intervention to reduce, stabilize, and decompress the spinal cord either surgically or through traction and halo-vest immobilization.

The American Spinal Injuries Association (ASIA) grade at presentation and at 6 months was measured on all patients. Complete SCI was defined as ASIA grade A (no motor or sensory function at S4/5) and incomplete as ASIA grades B to D (some motor or sensory function below the injury level).

Neurological outcome was assessed by comparing the proportions that improved 1 or more ASIA grade between initial presentation and 6-month follow-up.

Effect of time to definitive surgical intervention on ASIA grade: Early surgery was defined as within 8 hours of injury. Paramedic, hospital emergency department admission, and operating room patient-tracking databases were used to accurately evaluate the time to surgery.

The effect of low- versus high-energy injury on ASIA grade: Energy of injury was defined by mechanism. Low-energy injury was defined as those resulting from ball sports (eg, rugby, surfing, diving into shallow water, and falls from a standing height). High-energy injury was defined as those resulting from motor vehicle trauma in which the kinetic energy was deemed to be far greater.

The proportion that improved 1 or more ASIA grade between initial presentation and 6-month follow up was compared between cohorts using a Fisher's exact test.

The cohorts comprised ASIA grade on presentation (complete or incomplete), time to surgery (early or late), and energy of injury (high or low).

Fig. 1 shows the number of patients in each group.

Fig. 1

Patient numbers in each group used for analysis.

Table 1 shows patient demographics.

Table 1

Patient demographics.

Patient characteristics	Low energy	High energy
N	21	21
Age	Age matched
Female, %	4.7	47.0
Injury level
C3	1	1
C4	6	3
C5	11	9
C6	1	6
C7	1	2
Biomechanically stable injury	4	6
Fracture	3	18
Dislocation	18	3

Twenty-three patients had incomplete SCI and 19 had a complete SCI.

Seventeen patients had early (<8 hours) and 25 had late intervention.

Twenty-eight patients had anterior stabilization; 11 had nonsurgical decompression and stabilization; 2 had a combined anterior/posterior fixation; and 1 had posterior stabilization.

The energy of injury did not influence neurological outcome (P = .76; Fig. 2).

Fig. 2

Functional recovery of 1 or more American Spinal Injuries Association grades in the study cohort as a function of the energy of the injury.

The initial severity of injury (complete vs incomplete) was found to predict neurological outcome (P = .006; Fig. 3).

Fig. 3

Functional recovery of 1 or more American Spinal Injuries Association grades in the study cohort as a function of the severity of the injury.

Table 2 displays results of the statistical analysis of the main groups.

Table 2

Main analysis: proportion improving 1 or more ASIA grade.*

High energy n/N (%)	Low energy n/N (%)	RR (95% CI)	P
10/21 (47.6)	12/21 (57.1)	1.2 (0.67–2.15)	.76
Incomplete n/N (%)	Complete n/N (%)	RR (95% CI)	P
17/23 (73.9)	5/19 (26.3)	2.8 (1.27–6.20)	.0046
Early n/N (%)	Late n/N (%)	RR (95% CI)	P
9/17 (52.9)	10/25 (40.0)	1.32 (0.69–2.55)	.54

ASIA indicates American Spinal Injuries Association; RR, relative risk; and CI, confidence interval.

The energy of the injury in patients with an incomplete SCI did not influence neurological outcome (P = .73; Fig. 4).

Fig. 4

Functional recovery of 1 or more American Spinal Injuries Association grades in the incomplete group as a function of the energy of the injury.

Time to definitive decompression (<8 hours) in patients with incomplete SCI significantly influenced neurological outcome (P = .049; Fig. 5).

Fig. 5

Functional recovery of 1 or more American Spinal Injuries Association grades in the incomplete group as a function of the time to definitive treatment of the injury.

Tables 3 and Table 4 present results of the statistical analysis of the various subgroup analyses.

Table 3

Subgroup analysis based on injury severity showing proportion improving 1 or more ASIA grades.*

Incomplete				Complete
High energy, n/N	Low energy, n/N	RR (95% CI)	P	High energy, n/N	Low energy, n/N	RR (95% CI)	P
9/11 (81.8%)	8/12 (66.6%)	1.22 (0.75–1.99)	.60	4/9 (44.4%)	1/10 (10.0%)	2.24 (0.97–5.12)	.14
Early, n/N	Late, n/N			Early, n/N	Late, n/N
8/8 (100%)	8/15 (53.3%)	1.88 (1.17–3.01)	.05	2/9 (22.2%)	3/10 (30.0%)	0.80 (0.24–2.64)	1.00

ASIA indicates American Spinal Injuries Association; RR, relative risk; and CI, confidence interval.

Table 4

Subgroup analysis based on injury severity showing proportion improving 1 or more ASIA grades.*

High energy				Low energy
Early, n/N	Late, n/N	RR (95% CI)	P	Early, n/N	Late, n/N	RR (95% CI)	P
3/5 (50.0%)	7/15 (46.6%)	1.40 (0.48–4.08)	.68	8/11 (72.7%)	3/10 (30.0%)	1.48 (0.50–4.36)	.086

ASIA indicates American Spinal Injuries Association; RR, relative risk; and CI, confidence interval.

Discussion

McDonald and Sadowsky8 suggested that subacute intervention (24–72 hours) has yielded unsatisfactory results because most tissue damage is irreversible by that time and suggested that trials were needed to assess the effects of early surgical intervention (<8 hours).

Early results of the Surgical Treatment of Acute Spinal Cord Injury Study on the timing of surgery for spinal cord trauma indicate improved neurological outcome at 6- and 12-month follow-up in both patient groups ASIA A/B and ASIA C/D/E when treated by reduction and/or stabilization within 24 hours of injury compared with those treated later. This multicenter prospective nonrandomized study demonstrated that the early treatment group had a significantly larger percentage of patients improving 1 or more ASIA grades (67%) compared with the late group (40%) (P < .05).5,7

The results of our study confirm that the depth of neurological injury is the most consistent prognostic indicator in SCI. Findings would also suggest that early surgical management of incomplete SCI has a positive influence on functional outcome at 6 months (Table 3).

Logically, it could be postulated that prognosis following early reduction of lower-energy injuries may be more favorable than after higher-energy trauma. In the latter group, primary cord trauma is believed to cause a greater level of intrinsic cord disruption; whereas in the lower-energy group, ongoing compression might be said to be the main contributor to neurological deficit, as there is a greater case for early reduction in the latter group. These results did not support this hypothesis, since there is no significant difference between the high- and low-energy groups in terms of timing of definitive management. Although neurological outcome was more favorable following early reduction of bifacetal dislocation, as has been previously established by other authors, the data would not suggest that energy or mechanism of injury has a positive influence on ASIA score at 6 months after injury (Table 4).

An incomplete SCI would appear to reflect a more modest primary injury to the cord despite the apparent level of energy associated with the injury. Our findings therefore do not support the concept of rate of injury, as outlined in animal studies, as a significant influence.1,2,3,4

This study has a number of strengths and weaknesses. The data came from a single-site study database with reliable prospective data collection relating to the timing of surgery and ASIA score. To our knowledge, this is the first clinical study to consider energy of injury with a unique population base due to recreational and social demographics. It is however a small cohort and the follow-up time was limited. It is known that patients with SCI continue to show improvement up to and beyond 2 years following injury but most recovery occurs within the first 6 months.

While there was no significant difference in neurological outcome in the subset of patients sustaining SCI by low-velocity mechanism (P = .76), this study showed that more favorable prognosis in injuries associated with incomplete neurological deficit (P = .006). Also patients with incomplete SCI treated definitively within 8 hours had a greater improvement in ASIA score compared with those treated after 8 hours (P = .049). We would recommend early realignment for patients presenting with incomplete neurological deficit resulting from SCI.

Clinical Relevance and Impact:

Supports the role of early intervention in improving neurological recovery.

Future Research:

The Surgical Treatment of Acute Spinal Cord Injury Study (STASCIS Trial) is currently underway and will hopefully provide some definitive answers to the controversy surrounding the role of surgery in acute SCI.

We were unable to find a correlation between the energy of the initial trauma causing SCI and the neurological outcome.

The initial severity of injury (complete vs incomplete) predicts neurological outcome.

Early intervention (<8 hours) appears to improve the neurological outcome for patients with incomplete SCI.

Final class of evidence (CoE)-treatment	Yes
Study design:
Prospective cohort
Retrospective cohort	•
Case control
Case series
Methods
Patients at similar point in course of treatment	•
Follow-up ≥85%
Similarity of treatment protocols for patient groups	•
Patients followed-up long enough for outcomes to occur
Control for extraneous risk factors
Overall class of evidence	III