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Aims: The acetabular morphology varies greatly among individuals, and hypoplasia is more common in Asia than in Europe. Dislocation after bipolar hip arthroplasty (BHA) for femoral neck fracture occurs at a constant rate, and is affected by the acetabular morphology. This study aimed to clarify individual differences in the acetabula of Asian patients with displaced femoral neck fractures.Patients and Methods: Fifty patients with displaced femoral neck fractures were assessed (50 fractured hips, 50 non-fractured hips). On CT corrected by the anterior pelvic plane, the 100 hips were assessed regarding acetabular coverage (six parameters), acetabular depth (two parameters), and acetabular opening angle (four parameters). Additional parameters related to the fracture and sex were examined. The percentile of each parameter was shown for all hips.Results: There was no patient with hip dysplasia defined as superior acetabular sector angle (SASA) less than 110° Compared with men, women had a significantly smaller anterior acetabular sector angle (AASA) (p = 0.016), and significantly larger acetabular inclination angle (p = 0.006) and acetabular index angle (p = 0.034). In the group with a normal SASA, seven hips (7.3%) had an anterior wall defect (AASA<50°) and five hips (5.2%) had a posterior wall defect (posterior acetabular sector angle<90°).Conclusion: Older adults with femoral neck fractures can have anterior wall and posterior wall defects, even if their SASA is normal. Hidden acetabular dysplasia may be related to post-BHA dislocation. So, our results suggest that is important to accurately evaluate the acetabulum of patients with femoral neck fracture before surgery. [ABSTRACT FROM AUTHOR]