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Arch Dis Child. 2007 April; 92(4): 371–372.
PMCID: PMC2083676

TW2 and TW3 bone ages: time to change?

In 1983, the Tanner−Whitehouse 2nd edition (TW2) system of bone ageing was published and has remained the most widely used system in the UK.1 Several studies have shown that children are maturing more rapidly and reaching a given skeletal maturity score (SMS) at an earlier chronological age.2 In view of this finding, Tanner and colleagues published a revised 3rd edition for bone ageing in 2001 (TW3).3 This updated the relationship of the SMS to bone age to deal with the secular trend that had occurred in skeletal maturation since the previous edition. However, this new version has received little publicity and does not seem to be widely used in the UK .

To explore the changes that have occurred between these two publications, we retrospectively compared TW2 RUS (radius, ulna and short bones) and TW3 RUS bone age assessments in 142 children in two diagnostic groups (idiopathic short stature or constitutional delay in growth and puberty and congenital adrenal hyperplasia) with a range of bone ages from delayed to advanced.

The descriptions and manual ratings remain the same for TW2 and TW3, and the calculation of the SMS is the same. However, the centile charts for RUS SMS against age have changed between versions 2 and 3.

TW3 estimates of bone age were younger than TW2, and both were delayed compared with the chronological age in children with idiopathic short stature and constitutional delay in growth and puberty (table 11).). For children with congenital adrenal hyperplasia, TW3 estimates of bone age were younger than TW2, and both were advanced compared with chronological age. TW2 and TW3 estimates of bone age are not interchangeable. Figure 11 shows how the differences between the two versions change with increasing maturity score for boys and girls.

figure ac90134.f1
Figure 1 Difference between Tanner‐Whitehouse 2nd edition (TW2) and TW3 against maturity score for girls and boys. Points represent individual patients.
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Table 1 Mean (standard error of mean) Tanner−Whitehouse 2nd edition (TW2) compared with TW3 bone age estimates for children with idiopathic short stature/constitutional delay in growth and puberty and congenital adrenal hyperplasia

The SMS on which the bone age is based is the fundamental unit of measurement for bone maturity assessment, and should be considered alike any other anthropometric measure, such as height or weight. As such, the SMS centile charts require periodic updating if they are to be used to assess development.4,5 Our results show that TW3 bone age differed from TW2 bone age in the two diagnostic groups studied, with the differences becoming more marked with increasing maturity. This suggests that the currently widely used TW2 bone age may not reflect an accurate skeletal maturity assessment of today's child (particularly around the pubertal age range), and we would advocate the use of the revised TW3 version. In fact, to continue using TW2 bone ages is akin to using the 1966 height and weight charts instead of the more recent 1995 versions.


Competing interests: None.


1. Tanner J M, Whitehouse R H, Cameron N. et alAssessment of skeletal maturity and prediction of adult height (TW2 Method). 2nd edn. London, UK: Academic Press, 1983
2. Vignolo M, Naselli A, Magliano P. et al Use of the new US90 standards for TW‐RUS skeletal maturity scores in youths from the Italian population. Horm Res 1999. 51168–172.172 [PubMed]
3. Tanner J M, Healy M, Goldstein H. et alAssessment of skeletal maturity and prediction of adult height (TW3 Method), 3rd edn. London: WB Saunders, Harcourt Publishers Ltd 2001
4. Cox L A. The biology of bone maturation and ageing. Acta Paediatr Suppl 1997. 423107–108.108 [PubMed]
5. Tanner J, Oshman D, Bahhage F. et al Tanner‐Whitehouse bone age reference values for North American children. J Pediatr 1997. 131(Pt 1)34–40.40 [PubMed]

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