Acetabular component loosening is often associated with periacetabular bone loss. Different approaches are described to address the bone defects in acetabular revision surgery. Several authors have reported inferior results when uncemented Titanium alloys and older porous coated designs are used in acetabular revisions with significant bone loss. Cemented fixation of the revision cup with impaction bone grafting (BIG), introduced more than three decades ago has today a thorough documentation. The Tantalum designs, with inherent properties such as high volumetric porosity, low modulus of elasticity and high friction against the bone, have been suggested to improve the fixation of the acetabular component. Several authors have been reporting promising short- and medium-term results using the TM designs in acetabular revisions with large periacetabular bone defects. Proximal migration measured with radiostereometry (RSA) has been suggested to predict risk for late aseptic loosening in hip prosthesis surgery. This study was primarily to compare the proximal migration of the tantalum design with a cemented cup used in conjunction with bone allografting in cases with major bone loss. A group of patients with good periacetabular bone stock are included to analyse the differences between the tantalum and titanium design. RSA is used to accurately measure migration and rotation of the revision cups.