A meta-analysis of paraplegia complicating aortic surgery on patients having neither intercostal nor spinal collaterals, epitomized by patients with acute traumatic aortic rupture, was done. Index Medicus and Medline were searched for all suitable English publications between 1972 and 1992. New paraplegia occurred in 9.9% of 1492 patients who underwent surgery. However, 19.2% of patients undergoing surgery with only simple aortic cross-clamping developed paraplegia, in contrast to 6.1% if distal aortic perfusion was augmented by either "passive" or "active" methods (p < 0.00001). The risk of paraplegia increased progressively as cross-clamp times lengthened if simple aortic cross-clamping was used (p < 0.00001), but only once did the cross-clamp time exceed 30 minutes (p < 0.05). Paraplegia occurred in 8.2% of patients with "passive" shunts from the ascending aorta (p < 0.001 vs simple cross-clamping). Shunts from the left ventricular apex, however, had an incidence of paraplegia of 26.1% and, therefore, did not decrease the risk of paraplegia. "Active" augmentation of distal perfusion had the lowest risk of paraplegia: 2.3% (p < 0.00001 vs simple cross-clamping or "passive" shunts). Mortality, however, was higher in these potentially polytraumatized patients when they were perfused distally using methods requiring full systemic heparinization (18.2%), compared to mortality with methods not requiring heparin (11.9%; p < 0.01). In conclusion, simple aortic cross-clamping has a high risk of paraplegia if the cross-clamp time extends beyond 30 minutes. "Active" modalities of augmenting distal perfusion provide optimal spinal protection.