To assess the value of a radiographic score for the detection of delayed union in nailed fractures.
The modified radiographic union score (mRUS) values were determined by three separate radiologists on 259 radiographic sets of 58 nailed tibial or femoral fractures obtained at different timepoints after fracture (mean of 4.5 radiographic sets per fracture). A surgeon determined fracture outcome (normal or delayed union) at a mean of 192days after injury. Mean radiographic scores obtained at different timepoints after fracture were compared between fractures with normal or abnormal healing at follow-up.
The mean score values increased significantly over time for fractures with normal healing for all readers (p<0.001). The mean score values determined 11-14 weeks after injury were higher in fractures with normal healing than in fractures with delayed union at follow-up (p<0.05). Scoring of radiographs obtained at about 3 months after injury or later enabled detection of fractures with delayed union with a sensitivity of 0.63-0.77 and a specificity of 1.0 (area under curve: 0.77- 0.88).
The mRUS score can contribute to the detection of delayed union at a delay of about 3 months after injury in nailed shaft fractures.