ORIGINAL ARTICLE Reconstruction of the rotation center of the hip after oblong cups in revision total hip arthroplasty

Background The preoperative bone defect and the reconstruction of the center of rotation of the hip are crit-ical in acetabular revision surgery. Uncemented oblong cups are employed in order to manage these issues. We analyzed the clinical results and rates of revision of two different uncemented oblong cups, the reconstruction of the center of rotation of the hip, as well as the rate of radio-logical loosening and possible risk factors. Materials and methods Forty-five patients (46 hips) underwent acetabular revision surgery using two different uncemented oblong cups. We assessed the clinical results and the survival rate for revision and aseptic loosening. Intraop-erative bone loss was classified according to Paprosky, and acetabular reconstruction was assessed according to Rana-wat. The mean follow-up was 7.2 years (range 4–11 years). Results There were four re-revisions (three due to aseptic loosening); the survival rate for re-revision due to aseptic loosening was 60.1 % at seven years. The mean distance between the center of the femoral head prosthesis and the approximate center of the femoral head improved from 21.5 to 10.2 mm. Thirteen cups showed radiological loos-ening; the survival rate for radiological loosening at seven years was 40.54 %. A smaller postoperative hori-zontal distance was correlated with cup loosening. Conclusions Although optimal acetabular reconstruction can be achieved by using oblong uncemented cups in revision hip surgery, the clinical and radiological results are not encouraging. Excessive medialization of the cup may increase the rate of loosening