A case-control study of risk factors that predict femoral arterial injury in penetrating thigh trauma.

Study Hypothesis: Femoral artery injuries can be predicted by the mechanism of injury, wound location and tract, and physical findings following penetrating thigh trauma.
Design: Retrospective case-control study.
Participants: All 808 consecutive patients undergoing femoral arteriography for penetrating thigh trauma from September 1986 through December 1990 were eligible for inclusion in the study. All 50 patients in the eligible population with proven femoral artery injuries diagnosed by angiogram were the study subjects. Fifty patients with penetrating thigh trauma who had angiograms negative for injury and were systematically chosen from the eligible population served as controls.
Interventions: Data included mechanism of injury; location of wound entrance, tract, exit, and retained missile; physical findings (including ankle-brachial index); and the presence of femur fractures. Physical findings were divided into hard findings (pulse abnormality, expanding hematoma, or pulsatile bleeding) or soft findings (neurologic deficit, hypotension without another source, or bruit/thrill).
Results: Of the 808 eligible patients, 50 (6.2%) had a femoral arterial injury on angiography, 20 (40%) of which were clinically occult injuries. A medial thigh tract made an arterial injury 58 times more likely (odds ratio [OR], 57.5; P < .001) and was present in 100% of cases and 64% of controls. An anteromedial thigh tract made an arterial injury 12 times more likely (OR, 11.5; P < .001) and was present in 92% of cases and 50% of controls. A wound with hard physical findings was 118 times more likely to have an arterial injury (OR, 118; P < .00001) and was found in 54% of cases and none of the controls. The presence of any physical finding made an arterial injury 36 times more likely (OR, 36; P < .00001) and was found in 60% of cases and 4% of controls. The presence of a femur fracture or a gunshot mechanism was not predictive of injury.
Conclusion: Only patients with medial thigh wounds need to undergo angiography for the detection of femoral artery injuries. This approach would have reduced the angiography rate by 36% in this series. Had angiography been performed only on patients with any physical findings, a 70% reduction in the rate of angiography would have been achieved, although five occult arterial injuries per year would have been missed. Angiography should not be performed solely because of a gunshot mechanism or the presence of a femur fracture.