ObjectiveTo investigate the anatomical morphology of the proximal femur in adult patients with Crowe type IV developmental dysplasia of the hip (DDH) so as to provided a reference for the selection of femoral components or personalized artificial prosthesis for DDH. MethodsBetween June 2004 and December 2014, 49 patients (58 hips) with Crowe type IV DDH were included in this study. There were 7 males (8 hips) with an average age of 47.3 years and 42 females (50 hips) with an average age of 30.0 years. X-ray films were taken in all cases and CT scanning in 17 cases (17 hips). The anatomical parameters were measured through Osirix V 5.8.5 software. ResultsThe distance of femoral head dislocation was (6.09±1.04) cm;the femoral head and neck disappeared completely in 8 hips (13.8%);femoral head atrophy and deformation and femoral neck disappearance were observed in 11 hips (19.0%). The midpoint width of the small trochanteric canal was (1.53±0.29) cm;the isthmus diameter was (0.69±0.09) cm;the canal flare index (CFI) value was (3.50±0.42) cm;the femoral neck anteversion angle was (37.0±18.2)°;and all indexes showed significant difference when compared with ones of normal population and Crowe type I, II, and III patients. But there was no significant difference in femoral neck-shaft angle (132.3±9.1°), isthmus height (11.66±2.67) cm (P<0.05). The chimney type cavity (CFI<3) accounted for 51.7%, which was significantly higher than the value of normal population. There was a positive correlation between metaphyseal CFI and CFI (r=0.63, P=0.00), but there was no correlation between metaphyseal CFI and distal CFI (r=-0.17, P=0.21). ConclusionThe proximal femur has the morphological characteristics of narrow medullary cavity, increased anteversion angle, and high ratio of chimney type cavity, so it is necessary to design specialized femoral components or personalized artificial prosthesis for the DDH.