Page 56 - Slipped Capital Femoral Epiphysis Pathogenetic and Clinical aspects

Chapter 3
Incidence
It is difficult to compare the incidence we found in the Netherlands with the incidences reported in the literature because data on different age groups are presented. In addition, different estimation methods have been used. A few studies use ICD codes, as we did [1-3], but most studies used the hospital information system because this provided a defined framework [4-11]. The incidence we found is comparable to data from Sweden and the USA.
In general, it would appear that Asian countries like Japan, Singapore and Korea [9-11] have a lower incidence of SCFE than Western countries. Speculations on the reasons for these differences have focused on ethnic or nutritional differences [9,11] (see Table 1).
Gender ratio
All published studies report a male: female ratio with preponderance for boys, ranging from 1.4 to 4.1 (Singapore) [9].
Our study is unique in determining that the 95 % CIs over each of the past years in the Netherlands imply that there was no significant difference in the risk of being exposed to NT and T SCFE between boys and girls. Despite these figures, however, there has been an increase in the incidence of SCFE in girls over the past 13 years: the annual incidence increased significantly for girls aged 5 to 19 years. The incidence for boys did not increase significantly nor did that for the combined group.
Figure 1 show that the difference is small between girls and boys on an annual basis but that over the years of the study period there was an increase in the incidence of SCFE in girls compared to boys. To date, our study is the first to report such a difference at the national level while concomitantly describing an increase in the incidence of SCFE in girls over the last decade.
A decrease of male predominance has also been found in Japan and Sweden. Despite the low incidence in Japan, a fivefold increase in boys and tenfold increase in girls were found between 1974 and 1999 [10]. In Sweden, the pre-dominance of boys has decreased from 85–90 to 60–65 % during the first decade of this century [4, 12].
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