Application and limitation of different methods to assess skeletal age in orthodontic practice.

Skeletal age indicates the level of maturation of a child’s bones and helps pediatricians evaluate normal growth or developmental disorders. Orthodontists determine skeletal maturation to exploit growth potential in the correction of skeletal discrepancies, and to gauge any residual growth that may contribute to post-treatment relapse. To date, staging skeletal development has more predictive growth value than chronologic age or other physiological parameters such as the amount and velocity of body height, dental formation and emergence and pubertal markers. Hand and wrist radiographs have been reliable for bone age assessment. Commonly used methods include: comparisons of individual radiographs to age norms in the Greulich-Pyle atlas; a “bone-by-bone” evaluation in the Tanner and Whitehouse score system; and less frequently the Fishman system that uses 4 stages of bone maturation at 6 hand and wrist sites. Not widely used or equally reliable, though more accessible to orthodontists, is the determination of skeletal maturity from cephalometric images of cervical vertebrae, based on shape and lower border of vertebrae and intervertebral space. Recently, bone age was assessed through ultrasound with objectivity, lack of ionizing radiation and easy accessibility. All these methods are described and illustrated in our paper, with emphasis on technological developments, including computerized bone age estimation, which is less time-consuming and more reproducible than human estimates.