Perioperative Radiographic Predictors of Non-Union in Infra-Isthmal Femoral Shaft Fractures after Antegrade Intramedullary Nailing: A Case–Control Study

Antegrade intramedullary (IM) nailing is the gold standard treatment for femoral shaft fractures; however, the non-union rate of infra-isthmal femoral shaft fractures is still high after antegrade IM nailing. This retrospective case–control study aimed to determine the association between perioperative radiographic factors and the non-union of infra-isthmal femoral shaft fractures after antegrade IM nailing. Univariate and multivariate analyses were used to evaluate the radiographic risk factors of non-union. Ninety-three patients were included, with thirty-one non-unions and sixty-two matched controls between 2007 and 2017. All were regularly followed up for 2 years. Receiver operating characteristic analysis revealed that a ratio of the unfixed distal segment > 32.5% was strongly predictive of postoperative non-union. The risk factors for non-union were AO/OTA type B and C (odds ratio [OR]: 2.20), a smaller ratio of the distal fragment (OR: 4.05), a greater ratio of the unfixed distal segment (OR: 7.16), a higher ratio of IM canal diameter to nail size at the level of fracture (OR: 6.23), and fewer distal locking screws (OR: 2.31). The radiographic risk factors for non-union after antegrade IM nailing for infra-isthmal femoral shaft fractures were unstable fractures, shorter distal fragments, longer unfixed distal fragments, wider IM canal, and fewer distal locking screws. Surgeons must strive to avoid non-union with longer and larger nails and apply more distal locking screws, especially for unstable, wider IM canal, and shorter distal fragment fractures.