Bone metabolism in children with severe fractures was examined, risk factors for fractures were characterized, and effects of LED (light-emitting diode) irradiation on the risk factors for fractures were investigated. Since insufficiency fracture in children with severe cerebral palsy can be caused without obvious external force in daily care, it is sometimes handled as a medical accident and can lead to a lawsuit. It is very important to explain the possibility of an insufficiency fracture to guardians before a fracture is caused. However, risk factors for fractures in bone metabolism has not been well investigated and preventive treatment of fractures have also not been established. Risk factors in bone metabolism were investigated in 14 cases of insufficiency fracture in children with severe cerebral palsy accompanied by akathisia in this study. Fractures were likely caused around 8 years old when children grew rapidly, and either IGF-1 or BAP showed low values in all cases. A group with LED irradiation consisting of 25 cases indicated a normal value of IGF-1 related to bone growth, BAP related to bone density and NTX/Cr. A case irradiated to LED for more than one month clearly showed normal bone metabolism compared with the change within a non irradiated group after one year. LED irradiation increased bone density and femur cortical bone thickness, and improved bone age. Adequate effects were not seen in two children at 14 years of age. The commercially available LED light bulbs that we used have a peak at 446-477 nm in the blue wave length, but also have second peaks at 574 nm in green, at 590 nm in yellow, and even 612 nm in orange and 660 nm in red are included. Although it is thought that such a variety of wave lengths might have a good influence on bone metabolism; exposure time and distance, number of regions, and time period irradiated to LED are important factors, since the LED power density is low (0.9 mW/m(2) with a 30 cm distance). Our results suggest that LED irradiation can be a phototherapy to activate human homeostasis.