Estimating the bone age of a living child is typically performed by comparing images of their bones to images of models of the average skeleton for a given age and sex acquired from healthy children and compiled in an atlas. Features of bone development assessed in determining bone age include the presence of bones (have certain bones
ossified yet), the size and shape of bones, the amount of mineralization (also called
ossification), and the degree of fusion between the
epiphyses and
metaphyses. The first atlas published in 1898 by John Poland consisted of x-ray images of the left hand and wrist. knee, and elbow. An alternative approach to the atlas method just described is the so-called "single-bone method" where maturity scales are assigned to individual bones.
Evaluation of the bones of the hand and wrist The two most common techniques for estimating bone age are based on a posterior-anterior x-ray of a patient's left hand, fingers, and
wrist. The reason for imaging only the left hand and wrist are that a hand is easily x-rayed with minimal radiation and shows many bones in a single view. Further, most people are right-hand dominant and the left hand is therefore less likely to be deformed due to trauma. Finally, only the wrist and hand are imaged out of a desire to minimize the amount of potentially harmful ionizing radiation delivered to a child. The Greulich and Pyle atlas contains x-ray images of the left hands and wrists of different children deemed to be good models of the average appearance of the bones of the hand at a given age. The atlas has a set of images arranged in chronological order by age for males ranging from 3 months to 19 years and for females ranging from 3 months to 18 years in varying intervals of 3 months to 1 year. Images in the Greulich and Pyle atlas came from healthy white boys and girls enrolled in the Brush Foundation Study for Human Growth and Development between the years 1931 and 1942. The TW methods consist of evaluating individual bones and assigning a letter grade to each bone based on its degree of maturation. Next, the scores for all evaluated bones are compiled into a sum, and that sum is correlated to bone age through a lookup table for males or females depending on the sex of the patient.
Hemiskeleton method The bones in the hand a wrist in a newborn do not change much in the first year of life. Alternative techniques for estimating bone age in infancy include tallying the number of ossification centers present in the left half of the infant's body requiring a hemiskeleton x-ray. This technique was created to avoid errors in estimating bone age thought to arise from focusing on only one area of the body. used the
cervical vertebrae and found them to be as reliable and valid as the hand-wrist area for assessing skeletal age. He developed a series of standards for the assessment of skeletal age for both males and females. This method has the advantage of eliminating the need for additional radiographic exposure in cases where the vertebrae have already been recorded on a lateral cephalometric radiographic. This method is called the
Cervical vertebral maturation method. Hassel & Farman (1995) developed an index based on the second, third, and fourth cervical vertebrae (C2, C3, C4) and proved that atlas maturation was highly correlated with skeletal maturation of the hand-wrist. Several smartphone applications have been developed to facilitate the use of vertebral methods such as
Easy Age. == Clinical significance ==