ORIGINAL ARTICLE Assessing skeletal maturity by using blood spot insulin-like growth factor I (IGF-I) testing Mohamed Masoud, a Ibrahim Masoud, b Ralph L. Kent, Jr, c Nour Gowharji, d and Laurie E. Cohen e Boston, Mass, and Jeddah, Saudi Arabia Introduction: Accurate determination of skeletal maturity and remaining growth is crucial to many orthodontic, orthognathic, and dental-implant timing decisions. Cervical vertebral stages and hand-wrist radiographs are currently used to identify peak mandibular bone growth. These are highly subjective techniques that not only involve radiographic exposure but also lack the ability to determine the intensity of the growth spurt and the end of growth. Insulin-like growth factor I (IGF-I) is a circulating growth hormone-dependent factor whose level correlates with sexual maturity; it is used to diagnose growth hormone deficiency and excess. We hypothesized that IGF-I levels would also correlate with cervical skeletal maturity and would be highest at the cervical stages that correspond to the greatest amount of facial growth. Methods: We measured mean blood spot IGF-I levels in a cross-sectional study of 83 patients (44 female, 39 male) on recall to begin orthodontic treatment, in active treatment, or in posttreatment follow-up. Results: Mean blood spot IGF-I levels were significantly higher in the late pubertal stages than in the prepubertal, early pubertal, and postpubertal stages. Linear correlation showed that IGF-I levels had a significant positive correlation with cervical skeletal maturity from the prepubertal to the late pubertal stages, and a significant negative correlation from the late pubertal to the postpubertal stages. In the postpubertal stage, IGF-I levels had a negative linear correlation with increasing time since the onset of puberty and with chronological age. Conclusions: Blood spot IGF-I could be used as a skeletal maturity indicator and might be useful in detecting residual mandibular growth in young adults. (Am J Orthod Dentofacial Orthop 2008;134:209-16) M easurement of skeletal maturity is important in many fields of medical and dental prac- tice, and is critical to the modality and timing of treatment of various skeletal abnormalities. The chronologic timing of puberty and the adolescent growth spurt demonstrate much variation and are af- fected by both genetic and environmental factors. Timing also differs between boys and girls, occurring on average nearly 2 years earlier in girls. 1-3 Studies have shown that chronologic age and dental age are both poor predictors of the pubertal growth spurt. 4,5 Standard growth charts that are regularly updated for extended times and information about secondary sexual characteristics can be useful and have been shown to be good predictors of adult height and whether the growth spurt has occurred. However, these data are often unavailable. Many studies have shown the usefulness of hand-wrist radiographs in predicting the pubertal growth spurt. 6-12 Since lateral cephalometric radiographs are rou- tinely taken for orthodontic patients, using the cervical vertebrae from these radiographs to assess skeletal maturity has been especially appealing to orthodontists. This technique was described by Lamparski 13 in 1972 and has been confirmed by several studies since then. 14-17 Baccetti et al 17 used longitudinal data from the Michigan growth study and related the timing of peak mandibular growth to the 6 cervical vertebral stages described by previous investigators (Fig 1). In this technique, the second, third, and fourth cervical vertebrae are examined. The vertebrae start out wedge shaped with flat inferior borders. They gradually de- velop curvatures and change from wedge shaped to horizontally rectangular, to square, and to vertically rectangular. Cervical stage (CS) 3 is particularly im- portant because peak mandibular growth occurs in the a DMSc candidate, Department of Orthodontics, Harvard School of Dental Medicine, Boston, Mass; demonstrator, Preventive Dental Sciences, Division of Orthodontics, King Abdulaziz University, Jeddah, Saudi Arabia. b Private practice, Jeddah, Saudi Arabia. c Associate professor, Department of Biostatistics, Forsyth Institute, Boston, Mass; Resident member of the staff and head, Department of Oral Epidemiol- ogy and Health Policy, Harvard School of Dental Medicine, Boston, Mass. d Resident, Tufts School of Dental Medicine, Boston, Mass. e Director, Division of Endocrinology, Children’s Hospital, Boston, Mass. Reprint requests to: Mohamed Masoud, Harvard School of Dental Medicine, 188 Longwood Ave, REB 402, Boston, MA 02115; e-mail, masoudortho@ gmail.com. Submitted, May 2006; revised and accepted, September 2006. 0889-5406/$34.00 Copyright © 2008 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2006.09.063 209