Dual-mobility Cups Compared to Unipolar Cups on Dislocation and Cost-effectiveness After Primary Total Hip Arthroplasty.

Inclusion Criteria: * Patients who are eligible for elective primary THA with a cemented cup, with a 32mm or 36 mm liner, for any indication. * THA using posterolateral surgical approach. * Patients ≥ 70 years old * Adequate comprehension of written and spoken Dutch Exclusion Criteria * Patients unable to complete PROMs * Patients with dementia, epilepsy\*, spasticity\*, mental retardation or alcoholism. (If dementia or mental retardation is not already mentioned in the medical chart, this can be determined by doctors opinion.) * Patients not eligible for either a unipolar or a DM cup * These patients will be asked to participate in the non-randomized dual mobility observational cohort.