Subperiosteal new bone and callus formations in neonates with femoral shaft fracture at birth.

To compare the timing of subperiosteal new bone formation (SPNBF) and callus formation in femoral shaft fractures that occurred at birth between neonates with and without an underlying disease, we retrospectively evaluated the radiographs of 12 neonates with femoral fractures on birth day. Seven had no underlying disease, 3 had osteogenesis imperfecta, 1 had myotonic dystrophy, and 1 had arthrogryposis. We evaluated the timing of initial SPNBF/soft callus/hard callus formation. In neonates without an underlying disease, SPNBF and callus formation were not detected by day 6 on radiographs; SPNBF/soft callus/hard callus formation was first observed at day 14.29 ± 5.35/15.85 ± 4.49/21.43 ± 5.41, respectively (range 9-23/10-23/16-32). The three neonates with osteogenesis imperfecta had SPNBF/soft callus/hard callus formation on day 0/0/0, which was significantly earlier than in neonates without an underlying disease (all P = 0.017). In the neonate with myotonic dystrophy, SPNBF/soft callus/hard callus formation was first seen by day 14/14/14 and was first seen by day 20/43/68 in the neonate with arthrogryposis. In our restricted cohort, all neonates with femoral shaft fractures from birth trauma without an underlying disease showed SPNBF and soft callus formation by day 23. If SPNBF or callus formation is detected within 6 days, an underlying disease (e.g., osteogenesis imperfecta) may be considered. If these are not detected by day 23, injury after birth or other underlying diseases may be considered.