Excellent primary stability of uncemented acetabular shells is essential to obtain successful clinical outcomes. However, in the case of developmental dysplasia of the hip (DDH), aseptic loosening may be induced by instability due to a decrease of the contact area between the acetabular shell and host bone. The aim of this study was to assess the primary stability of two commercially-available acetabular shells, hemispherical and hemielliptical, in normal and DDH models. Synthetic bone was reamed using appropriate surgical reamers for each reaming condition (normal acetabular model). The normal acetabular model was also cut diagonally at 40° to create a dysplasia model. Stability of the acetabular components was evaluated by the lever-out test. In the normal acetabular model conditions, the maximum primary stabilities of hemispherical and hemielliptical shells were observed in the 1-mm under- and 1-mm over-reamed conditions, respectively, and the resulting stabilities were comparable. The lateral defect in the dysplasia model had an adverse effect on the primary stabilities of the two designs. The lever-out moment of the hemielliptical acetabular shell was 1.4 times greater than that of the hemispherical acetabular shell in the dysplasia model. The hemispherical shell is useful for the normal acetabular condition, and the hemielliptical shell for the severe dysplasia condition, in the context of primary stability.

非骨水泥髋臼壳出色的初始稳定性对于获得成功的临床结果至关重要。然而，在发育性髋关节发育不良（DDH）的情况下，由于髋臼壳和宿主骨之间的接触面积减少，不稳定性可能会引起无菌性松动。本研究的目的是评估两种市售髋臼壳（半球形和半椭圆形）在正常和 DDH 模型中的主要稳定性。对于每种铰孔条件（正常髋臼模型），使用合适的外科铰刀铰孔合成骨。正常髋臼模型也以 40° 对角切割以创建发育不良模型。髋臼假体的稳定性通过杠杆拉出试验进行评估。在正常髋臼模型条件下，半球壳和半椭圆壳的最大初级稳定性分别在 1 毫米下扩孔和 1 毫米扩孔条件下观察到，所得稳定性相当。发育不良模型中的横向缺陷对两种设计的主要稳定性产生不利影响。在发育不良模型中，半椭圆形髋臼壳的拉出力矩是半球形髋臼壳的 1.4 倍。在初级稳定性的情况下，半球形外壳适用于正常髋臼状况，而半椭圆形外壳适用于严重发育不良状况。发育不良模型中的横向缺陷对两种设计的主要稳定性产生不利影响。在发育不良模型中，半椭圆形髋臼壳的拉出力矩是半球形髋臼壳的 1.4 倍。在初级稳定性的情况下，半球形外壳适用于正常髋臼状况，而半椭圆形外壳适用于严重发育不良状况。发育不良模型中的横向缺陷对两种设计的主要稳定性产生不利影响。在发育不良模型中，半椭圆形髋臼壳的拉出力矩是半球形髋臼壳的 1.4 倍。在初级稳定性的情况下，半球形外壳适用于正常髋臼状况，而半椭圆形外壳适用于严重发育不良状况。