OBJECTIVES: To determine the extent to which knowledge from clinical trial protocols is transferred to nonparticipating patients. DESIGN: Retrospective review of prospectively collected data from a large clinical trial. SETTING: Six level-1 international trauma centers. METHODS: We compared rates and timing of reoperation in a subset of patients enrolled in the study to prospectively evaluate Reamed Intramedullary Nails in Patients with Tibial Fractures (SPRINT) to concurrent patients who were eligible but not enrolled. This was a retrospective review of prospectively collected trial data. The records of 6 of the original SPRINT centers were searched for non-SPRINT patients who underwent intramedullary nailing of a closed tibial fracture. The rate and timing of reoperation were compared. A P < 0.05 was considered significant. RESULTS: One hundred fourteen non-SPRINT patients were compared with 328 patients enrolled in SPRINT from those same sites. There were 7 reoperations (6.1%) in non-SPRINT patients versus 18 (5.2%) in SPRINT patients [odds ratio (OR) 1.19, 95% confidence interval (CI) 0.41 to 3.13; P = 0.811]. There was no difference in the time to reoperation between the SPRINT and non-SPRINT patients (6.2 vs. 6.8 months, 95% CI of the difference -3.8 to 2.6; P = 0.685) or in the proportion of patients who underwent reoperation before 6 months (29% vs. 43%; OR 1.75; 95% CI 0.18 to 15.41; P = 0.647). CONCLUSIONS: Patients not enrolled in SPRINT had similarly low rates of reoperation for nonunion, and the average time to reoperation for both groups was longer than 6 months. A 6-month waiting period may have allowed slow-to-heal fractures adequate time to heal, thereby reducing the rate of diagnosis of nonunion. As such, this waiting period could contribute to lower-than-expected reoperation rates for nonunion. It is possible that clinical trials may beneficially influence the care of nonenrolled patients.