Bone age
Encyclopedia
Bone age is a way of describing the degree of maturation of child's bone
s. As a person grows from fetal
life through childhood, puberty
, and finishes growth as a young adult, the bones of the skeleton
change in size and shape. These changes can be seen by x-ray
. The "bone age" of a child is the average age at which children reach this stage of bone maturation. A child's current height and bone age can be used to predict adult height.
At birth, only the metaphyses of the "long bone
s" are present. The long bones are those that grow primarily by elongation at an epiphysis
at one end of the growing bone. The long bones include the femur
s, tibia
s, and fibulas of the lower limb, the humeri
, radii
, and ulna
s of the upper limb (arm + forearm), and the phalanges of the finger
s and toe
s. The long bones of the leg comprise nearly half of adult height. The other primary skeletal component of height is the spine
and skull
.
As a child grows the epiphyses become calcified and appear on the x-rays, as do the carpal and tarsal bones of the hand
s and feet, separated on the x-rays by a layer of invisible cartilage
where most of the growth is occurring. As sex steroid
levels rise during puberty, bone maturation accelerates. As growth nears conclusion and attainment of adult height, bones begin to approach the size and shape of adult bones. The remaining cartilaginous portions of the epiphyses become thinner. As these cartilaginous zones become obliterated, the epiphyses are said to be "closed" and no further lengthening of the bones will occur. A small amount of spinal growth concludes an adolescent's growth.
Pediatric endocrinologists
are the physicians who most commonly order and interpret bone age x-rays and evaluate children for advanced or delayed growth and physical development.
. A hand is easily x-rayed with minimal radiation and shows many bones in a single view. The bones in the x-ray are compared to the bones of a standard atlas, usually "Greulich and Pyle".
A more complex method also based on hand x-rays is the "TW2" method. An atlas based on knee maturation has also been compiled.
The hands of infants do not change much in the first year of life and if precise bone age assessment is desired, an x-ray of approximately half of the skeleton (a "hemiskeleton" view) may be obtained to assess some of the areas such as shoulders and pelvis which change more in infancy.
In a number of conditions involving atypical growth, bone age height predictions are less accurate. For example, in children born small for gestational age who remain short after birth, the bone age is a poor predictor of adult height.
, the bone age of a healthy child may be a year or two advanced or delayed.
An advanced bone age is common when a child has had prolonged elevation of sex steroid
levels, as in precocious puberty
or congenital adrenal hyperplasia
. The bone age is often marginally advanced with premature adrenarche
, when a child is overweight from a young age or when a child has lipodystrophy. Bone age may be significantly advanced in genetic overgrowth syndromes, such as Sotos syndrome
, Beckwith-Wiedemann syndrome
and Marshall-Smith syndrome
.
Bone maturation is delayed with the variation of normal development termed Constitutional growth delay
, but delay also accompanies growth failure due to growth hormone deficiency
and hypothyroidism
.
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
s. As a person grows from fetal
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
life through childhood, puberty
Puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...
, and finishes growth as a young adult, the bones of the skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
change in size and shape. These changes can be seen by x-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
. The "bone age" of a child is the average age at which children reach this stage of bone maturation. A child's current height and bone age can be used to predict adult height.
At birth, only the metaphyses of the "long bone
Long bone
The long bones are those that are longer than they are wide. They are one of five types of bones: long, short, flat, irregular and sesamoid. Long bones, especially the femur and tibia, are subjected to most of the load during daily activities and they are crucial for skeletal mobility. They grow...
s" are present. The long bones are those that grow primarily by elongation at an epiphysis
Epiphysis
The epiphysis is the rounded end of a long bone, at its joint with adjacent bone. Between the epiphysis and diaphysis lies the metaphysis, including the epiphyseal plate...
at one end of the growing bone. The long bones include the femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
s, tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
s, and fibulas of the lower limb, the humeri
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
, radii
Radius (bone)
The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...
, and ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
s of the upper limb (arm + forearm), and the phalanges of the finger
Finger
A finger is a limb of the human body and a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates....
s and toe
Toe
Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being digitigrade. Humans, and other animals that walk on the soles of their feet, are described as being plantigrade; unguligrade animals are those that walk on hooves at the tips of...
s. The long bones of the leg comprise nearly half of adult height. The other primary skeletal component of height is the spine
Vertebral column
In human anatomy, the vertebral column is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs...
and skull
Human skull
The human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...
.
As a child grows the epiphyses become calcified and appear on the x-rays, as do the carpal and tarsal bones of the hand
Hand
A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...
s and feet, separated on the x-rays by a layer of invisible cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
where most of the growth is occurring. As sex steroid
Sex steroid
Sex steroids, also known as gonadal steroids, are steroid hormones that interact with vertebrate androgen or estrogen receptors. Their effects are mediated by slow genomic mechanisms through nuclear receptors as well as by fast nongenomic mechanisms through membrane-associated receptors and...
levels rise during puberty, bone maturation accelerates. As growth nears conclusion and attainment of adult height, bones begin to approach the size and shape of adult bones. The remaining cartilaginous portions of the epiphyses become thinner. As these cartilaginous zones become obliterated, the epiphyses are said to be "closed" and no further lengthening of the bones will occur. A small amount of spinal growth concludes an adolescent's growth.
Pediatric endocrinologists
Pediatric endocrinology
Pediatric endocrinology is a medical subspecialty dealing with variations of physical growth and sexual development in childhood, as well as diabetes and other disorders of the endocrine glands....
are the physicians who most commonly order and interpret bone age x-rays and evaluate children for advanced or delayed growth and physical development.
Methods
The most commonly used method is based on a single x-ray of the fingers, hand, and wristWrist
In human anatomy, the wrist is variously defined as 1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand;...
. A hand is easily x-rayed with minimal radiation and shows many bones in a single view. The bones in the x-ray are compared to the bones of a standard atlas, usually "Greulich and Pyle".
A more complex method also based on hand x-rays is the "TW2" method. An atlas based on knee maturation has also been compiled.
The hands of infants do not change much in the first year of life and if precise bone age assessment is desired, an x-ray of approximately half of the skeleton (a "hemiskeleton" view) may be obtained to assess some of the areas such as shoulders and pelvis which change more in infancy.
Height prediction
Statistics have been compiled to indicate the percentage of height growth remaining at a given bone age. By simple arithmetic, a predicted adult height can be computed from a child's height and bone age. Separate tables are used for boys and girls because of the sex difference in timing of puberty, and slightly different percentages are used for children with unusually advanced or delayed bone maturation. These tables, the Bayley-Pinneau tables, are included as an appendix in the Greulich and Pyle atlas.In a number of conditions involving atypical growth, bone age height predictions are less accurate. For example, in children born small for gestational age who remain short after birth, the bone age is a poor predictor of adult height.
Clinical application of bone age readings
An advanced or delayed bone age does not always indicate disease or "pathologic" growth. Conversely, the bone age may be normal in some conditions of abnormal growth. Children do not mature at exactly the same time. Just as there is wide variation among the normal population in age of losing teeth or experiencing the first menstrual periodMenarche
Menarche is the first menstrual cycle, or first menstrual bleeding, in female human beings. From both social and medical perspectives it is often considered the central event of female puberty, as it signals the possibility of fertility....
, the bone age of a healthy child may be a year or two advanced or delayed.
An advanced bone age is common when a child has had prolonged elevation of sex steroid
Sex steroid
Sex steroids, also known as gonadal steroids, are steroid hormones that interact with vertebrate androgen or estrogen receptors. Their effects are mediated by slow genomic mechanisms through nuclear receptors as well as by fast nongenomic mechanisms through membrane-associated receptors and...
levels, as in precocious puberty
Precocious puberty
As a medical term, precocious puberty describes puberty occurring at an unusually early age. In most of these children, the process is normal in every respect except the unusually early age, and simply represents a variation of normal development. In a minority of children, the early development is...
or congenital adrenal hyperplasia
Congenital adrenal hyperplasia
Congenital adrenal hyperplasia refers to any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the biochemical steps of production of cortisol from cholesterol by the adrenal glands ....
. The bone age is often marginally advanced with premature adrenarche
Adrenarche
Adrenarche is an early sexual maturation stage in some higher primates that in humans typically occurs at around 6 to 8 years of age. During adrenarche the adrenal cortex secretes increased levels of androgens such as DHEA and DHEAS, but without increased cortisol levels. Adrenarche is the result...
, when a child is overweight from a young age or when a child has lipodystrophy. Bone age may be significantly advanced in genetic overgrowth syndromes, such as Sotos syndrome
Sotos syndrome
Sotos syndrome is a rare genetic disorder characterized by excessive physical growth during the first 2 to 3 years of life. The disorder may be accompanied by autism mild mental retardation, delayed motor, cognitive, and social development, hypotonia , and speech impairments...
, Beckwith-Wiedemann syndrome
Beckwith-Wiedemann syndrome
Beckwith–Wiedemann syndrome is an overgrowth disorder usually present at birth characterized by an increased risk of childhood cancer and certain congenital features. Originally, Dr...
and Marshall-Smith syndrome
Marshall-Smith syndrome
Marshall-Smith Syndrome, discovered in 1971 , is characterized by unusual accelerated skeletal maturation and symptoms like conspicuous physical characteristics, respiratory difficulties, and mental retardation. Cases described in the literature show a clinical variabililty regarding related...
.
Bone maturation is delayed with the variation of normal development termed Constitutional growth delay
Constitutional growth delay
Constitutional growth delay is a term describing a temporary delay in the skeletal growth and thus height of a child with no other physical abnormalities causing the delay. Short stature may be the result of a growth pattern inherited from a parent or occur for no apparent reason...
, but delay also accompanies growth failure due to growth hormone deficiency
Growth hormone deficiency
Growth hormone deficiency is a medical condition in which the body does not produce enough growth hormone . Growth hormone, also called somatotropin, is a polypeptide hormone which stimulates growth and cell reproduction...
and hypothyroidism
Hypothyroidism
Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.Iodine deficiency is the most common cause of hypothyroidism worldwide but it can be caused by other causes such as several conditions of the thyroid gland or, less commonly, the pituitary gland or...
.