X-ray diagnosis of healing fractures in rabbits

Do X-rays adequately reflect the strength of callus post fracture? Eleven rabbit tibiae were manually fractured and allowed to heal in plaster. At varying times post fracture, the rabbits were sacrificed and the tibiae were removed. AP and lateral X-rays of each tibia were obtained and shown to 27 orthopedists and radiologists who were asked to rank the bones in order of strength. The valid ranking was done using data obtained by loading the bones axially to failure in an Instron machine. Each physician's ranking was compared with that obtained from the Instron with a median correlation level p=0.0668. This implies that a physician, whether an orthopedist or radiologist, is not very reliable at determining early osseous union.