Intramedullary nailing of the femur without reaming of the medullary canal has been advocated as a method to reduce marrow embolization to the lungs and the rate of infection after open fractures. The use of nailing without reaming, however, has been associated with lower rates of fracture-healing. The purpose of this prospective study was to compare the rate of union of femoral shaft fractures following intramedullary nailing with and without reaming.

Two hundred and twenty-four patients were enrolled in a multicenter, prospective, randomized clinical trial to compare nailing without reaming and nailing with reaming. One hundred and six patients with 107 femoral shaft fractures were treated with a smaller diameter nail without reaming of the canal, and 118 patients with 121 fractures had reaming of the canal and insertion of a relatively larger diameter nail. Patients were followed at six-week intervals until union occurred or a nonunion was diagnosed.

The two groups were comparable with regard to the measured patient and injury characteristics. Eight (7.5%) of the 107 fractures in the group without reaming had a nonunion compared with two (1.7%) of 121 fractures in the group with reaming (p = 0.049). The relative risk of nonunion was 4.5 times greater (95% confidence interval = 1 to 20) without reaming and with use of a relatively small-diameter nail.

Intramedullary nailing of femoral shaft fractures without reaming results in a significantly higher rate of nonunion compared with intramedullary nailing with reaming.