Exchange nailing for aseptic nonunion of femoral shaft: a retrospective cohort study for effect of reaming size.

Background: Exchange nailing has been the favored method to treat aseptic nonunions of the femoral shaft. The recommended amount of over-reaming is at least 2 mm. The purpose of this study was to determine whether the effectiveness of nonunion treatment is greatly reduced with less than 2 mm of over-reaming.

Methods: Aseptic nonunions of the femoral shaft were treated by exchange nailing with 1 mm (n = 37) or at least 2 mm (n = 44) of over-reaming. Union rates, union periods, and complications were compared. Indications for exchange nailing were aseptic nonunions of the femoral shaft with an inserted intramedullary nail, shortening of less than 1.5 cm, and a fracture gap of less than 5 mm.

Results: After a mean follow-up of 3.6 years (range, 1.1-7.1 years), union rates were 31 (91.2%) of 34 nonunions with over-reaming of 1 mm and 37 (92.5%) of 40 nonunions with over-reaming of 2 mm or more (p = 0.32). The mean union periods were 4.4 months (range, 2.5-8 months) and 4.4 months (range, 3-8 months), respectively (p = 0.83). Except for persistent nonunions, no significant complications occurred.

Conclusions: Exchange nailing can be considered the first choice to treat aseptic nonunions of the femoral shaft. The diameter of the new intramedullary nail should be as large as possible to reinforce the mechanical strength of the repair. The osteogenic potential stimulated by the reaming of cancellous bone graft was similar with over-reaming of 1 mm and with over-reaming of 2 mm or more.