Reliability of radiographs in defining union of internally fixed fractures

We assessed whether radiographs can predict union of internally fixed fractures, and therefore be used as end-points in studies of fracture healing. Forty-seven radiographic series of forearm, femoral and tibial fractures treated by internal fixation over a 3-year period were reviewed. All forearm fractures were treated with dynamic compression plates (DCP), and all tibial and femoral fractures with intra-medullary nails. Callus formation and fracture line filling with time were measured on each radiograph. The ability of five orthopaedic surgeons to chronologically rank the blinded radiographs and to agree on the point of union was assessed. Correlation between callus formation, fracture line filling and union was noted. The ability of surgeons to correctly rank the radiographs and to agree on the point of union was in the order of 70%. Callus formation and union progression was significant in femoral fractures (P<0.05). Fracture line filling and union progression showed significance in the forearm (P<0.01) and femoral groups (P<0.05). Taking serial radiographs to assess healing would have led to only one early intervention. Radiographs do not define union in internally fixed fractures with sufficient accuracy to enable their use as end-points of fracture healing. Studies quoting radiographic end-points should be interpreted with care.