Value of measuring bone density serial changes on a picture archiving and communication systems (PACS) monitor in distraction osteogenesis

Serial changes of bone density in 26 femora and 22 tibiae that underwent leg lengthening by distraction osteogenesis were investigated by measuring the pixel value shown on a picture archiving and communication systems (PACS) monitor. The pixel value of the original cortex did not change significantly until the external fixator was removed. The pixel value of the distraction sites did not change significantly for the first 5-6 weeks/cm, but rapidly increased after 7 weeks/cm in the femur and tibia, then slowly increased after 8 weeks/cm. The serial changes of the pixel value of the distracted bone showed a sigmoid curve, rather than a straight increasing line. The relative pixel values of the lengthening sites were >95% in three of the four cortices at external fixator removal. Thus, the pixel value of PACS is a rapid and easy method for the detention of bone density changes in distraction osteogenesis.