Cervical vertebrae morphology used for skeletal maturation determination: The reliability of staging
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Numerous methods have been proposed to predict adolescent growth. It has been demonstrated that chronological age is an unreliable method, as is dental age, due to the normal variation among individuals (Fishman, 1981). Sexual characteristics are a reliable indicator of a growth spurt but appear on the downward slope of the spurt and are therefore not helpful. Skeletal maturation proves to be the most effective way to predict the individual's stage of growth (Baccetti, 2005). Skeletal maturation refers to the degree of development of ossification in bone. The standard method of evaluating skeletal maturation has been to take a left hand wrist radiograph to compare the hand bones of the individual to that of published atlases. Bjork and Helm (1967) found that the peak in adolescence increments in facial size generally occurs at the same time as the growth peak in body height, with height increases preceding facial growth spurts by 6-12 months. The spurt in the maxilla is less pronounced than that in the mandible and occurs 1 1/2 to 2 years earlier in girls than boys. Determining if the adolescent growth spurt has occurred and estimating how much growth remains, becomes an important part in orthodontic treatment planning. In order to take advantage of the pubertal growth spurt in orthodontic treatment timing, Fishman developed a system that uses four stages of bone maturation found at six sites located on the thumb, third finger, fifth finger, and radius (Fishman, 1981). Eleven skeletal maturation indicators (SMI) are found at these six sites and coincide with the entire period of adolescent development. The ossification sequence is epiphyseal widening, ossification of the sesmoid of the thumb, capping of selective epiphyses over their diaphyses and ending with fusion of selected epiphyses and diaphyses (Figure 1). This sequence has been found to be both stable and reliable. By comparing the individuals hand wrist film, an SMI of 1-11 can be determined depending on the amount of skeletal maturation (Figure 2). A brief description of the stages of SMI is as follows: Width of epiphysis as wide as diaphysis. Stage 1: Third finger-proximal phalanx; Stage 2: Third finger-middle phalanx; Stage 3: Fifth finger-middle phalanx. Ossification. Stage 4: Adductor sesamoid of thumb Capping of epiphysis. Stage 5: Third finger-distal phalanx; Stage 6: Third finger-middle phalanx; Stage 7: Fifth finger-middle phalanx. Fusion of epiphysis and diaphysis. Stage 8: Third finger-distal phalanx; Stage 9: Third finger-proximal phalanx; Stage 10: Third finger-middle phalanx; Stage 11: Radius.