A recent retrospective analysis of femur fractures concluded that early surgical fixation in patients who have sustained blunt thoracic trauma (AIS score for Thorax > or = 2) was a risk factor for postoperative pulmonary failure. We conducted a review of all femur fractures admitted to a level I trauma center from November, 1988 to May, 1993. Inclusion criteria were ISS > or = 18, mid-shaft femur fractures treated with reamed intramedullary fixation, and no mortalities secondary to head trauma or hemorrhagic shock. One hundred thirty-eight patients met these criteria. Four patient groups were created: N1--no thoracic trauma (AIS score for thorax < 2), and early surgical fixation (< 24 hours after injury, n = 49); N2--no thoracic trauma and delayed fixation (> or = 24 hours, n = 8); T1--thoracic trauma (AIS score for Thorax > or = 2) and early fixation (n = 56); T2--thoracic trauma and delayed fixation (n = 25). There were no significant differences in age, Injury Severity Score, or Glasgow Coma Scale score between the four groups. Mortality rate, length of stay (LOS), LOS in the TICU, and duration of mechanical ventilation tended to be greater in patients with delayed fracture fixation, however, this was not statistically significant. The N2 patients had a pneumonia rate of 38% compared with 10% in group N1 (p = 0.07). The T2 patients had a pneumonia rate of 48% compared with 14% in group T1 (p = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)