Clinical characteristics of children with atypical and idiopathic slipped capital femoral epiphysis: Description of the age-weight test and implications for further diagnostic investigation

Slipped capital femoral epiphyses (SCFEs) can be idiopathic or atypical (as sociated with renal failure, radiation therapy, and endocrine disorders). T he demographics of 433 children (285 idiopathic, 148 atypical) with 612 SCF Es were studied to define predictors of atypical SCFEs. Multiple logistic r egression analysis showed that aye and weight were predictors. For two pati ents of equal weight, those younger than 10 or older than 16 yeats of age w ere 4.2 times more likely to have an atypical SCFE; fur two patients of equ al age, those < 50th percentile weight were 8.4 times more likely. The age- weight test was defined as negative when age younger than 16 years and weig ht greater than or equal to 50th percentile and positive when beyond these boundaries. The probability of a child with a negative rest result having a n idiopathic SCFE was 93%, and the probability of a child with a positive t est result having an atypical SCFE was 52%. An evaluation of the child's ag e and weight is useful when considering the cause of an SCFE.