Fig. 2From: Using Z-score to optimize population-specific DDH screening: a retrospective study in Hangzhou, ChinaZ-score models of the α and β angles. The smoothed solid line is the modeled mean value (The polylines under it are the real mean value in this age group). The smoothed dotted and dashed lines represent the − 1 SD (standard deviation) of the angle α and + 1 SD of the angle βBack to article page