COL2A1 and necrosis: LCPD is idiopathic ischemic necrosis of the femoral head in children, and other scholars have also reported the same COL2A1 gene locus mutations in familial LCPD patients (Kannu et al., 2011; Miyamoto et al., 2007; Woratanarat et al., 2014; Su et al., 2008).