Editing Bone age (section)

== Measurement techniques ==
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.<ref name=":9" /><ref name=":11">{{Cite book |last=Hackman |first=S. Lucina M. R. |title=Age estimation in the living: a test of 6 radiographic methods |year=2012}}</ref> Features of bone development assessed in determining bone age include the presence of bones (have certain bones [[Ossification center|ossified]] yet), the size and shape of bones, the amount of mineralization (also called [[ossification]]), and the degree of fusion between the [[epiphysis|epiphyses]] and [[metaphysis|metaphyses]].<ref name=":4" /><ref>{{Cite book |last=Oestreich |first=A. E. |url=https://www.worldcat.org/oclc/233973147 |title=Encyclopedia of diagnostic imaging |publisher=Springer |others=A. L. Baert |year=2008 |isbn=978-3-540-35280-8 |location=Berlin |pages=148–150 |oclc=233973147}}</ref> The first atlas published in 1898 by John Poland consisted of x-ray images of the left hand and wrist.<ref>{{Cite book |last=Poland |first=John |title=Skiagraphic atlas showing the development of the bones of the wrist and hand: for the use of students and others |publisher=Smith, Elder, & Company |year=1898}}</ref><ref name=":8" /> Since then, updated atlases of the left hand and wrist have appeared,<ref name=":12" /><ref name=":4" /> along with atlases of the foot and ankle,<ref>{{Cite book |last1=Hoerr |first1=Normand L. |title=Radiographic Atlas of Skeletal Development of the Foot and Ankle |last2=Pyle |first2=Sarah Idell |last3=Francis |first3=Carl C. |publisher=Charles C. Thomas |year=1962 |location=Springfield, IL}}</ref> knee,<ref name=":14">{{Cite book |last1=Pyle |first1=Sarah Idell |title=A Radiographic Atlas of Skeletal Development of the Knee |last2=Hoerr |first2=Normand L. |publisher=Charles C. Thomas |year=1969 |location=Springfield, IL}}</ref> and elbow.<ref>{{Cite book |last1=Brodeur |first1=A.E. |title=Radiology of the Pediatric Elbow |last2=Silberstein |first2=M.J. |last3=Gravis |first3=E.R. |publisher=G.K. Hall Medical Publishers |year=1981 |location=Boston}}</ref> An alternative approach to the atlas method just described is the so-called "single-bone method" where maturity scales are assigned to individual bones.<ref name=":9" /><ref name=":11" /> Here, a selection of bones are given a score based on their perceived development, a sum is totaled based on the individual bone scores, and the sum is correlated to a final bone age.<ref name=":9" /><ref name=":11" /><ref name=":13">{{Cite book |url=https://www.worldcat.org/oclc/46393147 |title=Assessment of skeletal maturity and prediction of adult height (TW3 method) |date=2001 |publisher=W.B. Saunders |first=J. M. |last=Tanner |isbn=978-0-7020-2511-2 |edition=3rd |location=London |oclc=46393147}}</ref>

=== 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]].<ref name=":4" /><ref name=":5">{{Cite journal |last=Satoh |first=Mari |date=October 24, 2015 |title=Bone age: assessment methods and clinical applications |journal=Clinical Pediatric Endocrinology |volume=24 |issue=4 |pages=143–152 |doi=10.1297/cpe.24.143 |issn=0918-5739 |pmc=4628949 |pmid=26568655}}</ref> The reason for imaging only the left hand and wrist are that a hand is easily x-rayed with minimal radiation<ref name="patcas">{{Cite journal |last1=Patcas |first1=R. |last2=Signorelli |first2=L. |last3=Peltomaki |first3=T. |last4=Schatzle |first4=M. |year=2012 |title=Is the use of the cervical vertebrae maturation method justified to determine skeletal age? A comparison of radiation dose of two strategies for skeletal age estimation |journal=The European Journal of Orthodontics |volume=35 |issue=5 |pages=604–9 |doi=10.1093/ejo/cjs043 |pmid=22828078 |doi-access=free}}</ref> and shows many bones in a single view.<ref name="xhand">{{Cite journal |last1=Gertych |first1=A. |last2=Zhang |first2=A. |last3=Sayre |first3=J. |last4=Pospiechkurkowska |first4=S. |last5=Huang |first5=H. |date=Jun–Jul 2007 |title=Bone age assessment of children using a digital hand atlas |journal=Computerized Medical Imaging and Graphics |volume=31 |issue=4–5 |pages=322–331 |doi=10.1016/j.compmedimag.2007.02.012 |pmc=1978493 |pmid=17387000}}</ref> Further, most people are right-hand dominant and the left hand is therefore less likely to be deformed due to trauma.<ref name=":5" /><ref>{{Cite journal |last1=Subramanian |first1=Surabhi |last2=Viswanathan |first2=Vibhu Krishnan |date=May 1, 2022 |title=Bone Age |url=https://pubmed.ncbi.nlm.nih.gov/30725736/ |access-date=November 8, 2022 |website=PubMed |language=en |pmid=30725736}}</ref> 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.<ref name=":1" />

==== Greulich and Pyle atlas ====
In the United States, bone age is usually determined by comparing an x-ray of the patient's left hand and wrist to a set of reference images contained in the Greulich and Pyle atlas.<ref name=":4" /><ref name=":1" /><ref name=":6" /><ref name=":0" /> Drs. William Walter Greulich and Sarah Idell Pyle published the first edition of their standard reference atlas of x-ray images of the left hands and wrists of boys and girls in 1950.<ref name=":12">Greulich WW, Pyle SI: ''Radiographic Atlas of Skeletal Development of the Hand and Wrist'', 2nd edition. Stanford, CA: Stanford University Press, 1959.</ref> 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.<ref name=":6" /><ref name=":7">{{Cite journal |last1=Prokop-Piotrkowska |first1=Monika |last2=Marszałek-Dziuba |first2=Kamila |last3=Moszczyńska |first3=Elżbieta |last4=Szalecki |first4=Mieczysław |last5=Jurkiewicz |first5=Elżbieta |date=2021-08-23 |title=Traditional and New Methods of Bone Age Assessment-An Overview |journal=Journal of Clinical Research in Pediatric Endocrinology |volume=13 |issue=3 |pages=251–262 |doi=10.4274/jcrpe.galenos.2020.2020.0091 |issn=1308-5735 |pmc=8388057 |pmid=33099993}}</ref>

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.<ref name=":1" /><ref name=":4" />

To assign a bone age to the patient under review, a radiologist compares the patient's hand and wrist x-ray to images in the Greulich and Pyle atlas. Assessment of the carpals, metacarpals, and phalanges are used to find the closest match in the atlas; the chronological age of the patient in the atlas becomes the bone age assigned to the patient under review.<ref name=":6" /> If a patient's x-ray is found to be very close in appearance to two contiguous images in the atlas, then an average of the chronological ages in the atlas may be used as the patient's bone age, although some evaluators choose to interpolate the closest age while others report a range of possible bone ages.<ref name=":8" />

A drawback associated with the Greulich and Pyle method of assessing bone age is that it relies on x-ray imaging and therefore requires exposing the patient to ionizing radiation. Further, there can be moderate levels of variability in the bone ages assigned to the same patient by different assessors.<ref name=":7" /> Other downsides are that the atlas has not been updated since 1959 and the images in the atlas were acquired from healthy white children living in Cleveland, Ohio in the 1930s and 1940s and therefore may not yield accurate bone age assignments when applied to non-white patients or unhealthy children.<ref name=":0" /><ref name=":1" /><ref name=":7" />[[File:Bones_of_the_hand_and_wrist_used_for_bone_age_estimation_in_the_Tanner-Whitehouse_method.svg|thumb|267x267px|Bones of the hand and wrist used for bone age estimation in the Tanner-Whitehouse method.]]

==== Tanner-Whitehouse method ====
The Tanner-Whitehouse (TW) technique of estimating bone is a "single-bone method" based on an x-ray image of a patient's left hand and wrist. There have been two updates since the first publication of the TW method in 1962: the TW2 method in 1975 and the TW3 method in 2001.<ref name=":13" /><ref>[[James Mourilyan Tanner|Tanner JM]], Whitehouse RH, Marshall WA, et al.: ''Assessment of Skeletal Maturity and Prediction of Adult Height (TW2 Method)''. New York: Academic Press, 1975.</ref> 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.<ref name=":13" />

The bones considered in the TW3 method include the distal radius and ulna, the metacarpals and phalanges of the 1st, 3rd, and 5th fingers, and all of the carpal bones except the pisiform.<ref name=":11" /><ref name=":13" />

=== Knee maturation ===
An atlas based on knee maturation has also been compiled.<ref name=":0" /><ref name=":14" /><ref>{{cite journal |last1=Poznanski |first1=Andrew |title=Book Review: Skeletal Maturity. The Knee Joint as a Biological Indicator |journal=Radiology |date=January 1978 |volume=126 |issue=1 |doi=10.1148/126.1.88 |url=https://pubs.rsna.org/doi/10.1148/126.1.88 |access-date=15 January 2021|url-access=subscription }}</ref>

=== Hemiskeleton method ===
The bones in the hand a wrist in a newborn do not change much in the first year of life.<ref name=":6" /> However, most pediatric radiologists still use the Greulich and Pyle technique for estimating bone age in infancy.<ref name=":8">{{Cite journal |last1=Breen |first1=Micheál A. |last2=Tsai |first2=Andy |last3=Stamm |first3=Aymeric |last4=Kleinman |first4=Paul K. |date=August 2016 |title=Bone age assessment practices in infants and older children among Society for Pediatric Radiology members |url=https://pubmed.ncbi.nlm.nih.gov/27173981 |journal=Pediatric Radiology |volume=46 |issue=9 |pages=1269–1274 |doi=10.1007/s00247-016-3618-7 |issn=1432-1998 |pmid=27173981|s2cid=22582409 }}</ref><ref name=":9">{{Cite journal |last1=Tsai |first1=Andy |last2=Stamoulis |first2=Catherine |last3=Bixby |first3=Sarah D. |last4=Breen |first4=Micheál A. |last5=Connolly |first5=Susan A. |last6=Kleinman |first6=Paul K. |date=March 2016 |title=Infant bone age estimation based on fibular shaft length: model development and clinical validation |url=https://pubmed.ncbi.nlm.nih.gov/26637315 |journal=Pediatric Radiology |volume=46 |issue=3 |pages=342–356 |doi=10.1007/s00247-015-3480-z |issn=1432-1998 |pmid=26637315|s2cid=8285692 }}</ref> 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.<ref name=":8" /><ref name=":9" /> One common method based on x-rays of the hemiskeleton is the Sontag method.<ref name=":10">{{Cite journal |last=Sontag |first=L. W. |title=Rate of Appearance of Ossification Centers from Birth to the Age of Five Years |date=1939-11-01 |url=http://archpedi.jamanetwork.com/article.aspx?doi=10.1001/archpedi.1939.01990100031004 |journal=Archives of Pediatrics & Adolescent Medicine |language=en |volume=58 |issue=5 |pages=949 |doi=10.1001/archpedi.1939.01990100031004 |issn=1072-4710|url-access=subscription }}</ref> This technique was created to avoid errors in estimating bone age thought to arise from focusing on only one area of the body.<ref name=":10" /> The Sontag method uses x-rays of all the bones and joints of the upper and lower limbs on the left side of the body.<ref name=":10" /> Then, a radiologist counts the number of ossification centers present and uses a chart to convert the sum of ossification centers to a bone age. There is a chart for males and another for females with possible bone ages ranging from 1 month to 5 years.<ref name=":10" /> Since most of the ossification centers counted using this technique appear early in life, this method is only valid for measuring bone age up to around 5 years of age.<ref name=":10" />

=== Evaluation of cervical vertebrae ===
Lamparski (1972)<ref>{{Cite journal|last=Lamparski|first=DG|date=1972|title=Skeletal Age Assessment Utilizing Cervical Vertebrae.|journal=Master Science Thesis}}</ref> used the cervical vertebrae and found them to be as reliable and valid as the hand-wrist area for assessing skeletal age.&nbsp;He developed a series of standards for the assessment of skeletal age for both males and females.&nbsp;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.<ref>{{Cite journal |last1=Caldas |first1=Maria de Paula |last2=Ambrosano |first2=Gláucia Maria Bovi |last3=Haiter |first3=Francisco |title=Use of cervical vertebral dimensions for assessment of children growth |date=April 2007 |journal=Journal of Applied Oral Science |volume=15 |issue=2 |pages=144–147 |doi=10.1590/S1678-77572007000200014 |issn=1678-7757 |pmc=4327247 |pmid=19089119}}</ref> This method is called the [[Cervical vertebral maturation method]].

Hassel &&nbsp;Farman (1995)<ref>{{Cite journal|last1=Hassel|first1=B.|last2=Farman|first2=A. G.|date=January 1995|title=Skeletal maturation evaluation using cervical vertebrae|journal=American Journal of Orthodontics and Dentofacial Orthopedics|volume=107|issue=1|pages=58–66|issn=0889-5406|pmid=7817962|doi=10.1016/S0889-5406(95)70157-5}}</ref> 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''.