Mid-term results of hydroxyapatite-coated threaded cup implanted without supplementary supporting screws

We retrospectively reviewed the clinical, radiographic, and survivorship outcomes in a series of 180 patients that underwent 204 primary Total Hip Arthroplasties with the use of a second generation threaded hydroxyapatite-coated acetabular cup that was implanted without any supplementary supporting screws. At an average follow-up period of 10.2 (range: 8-14) years, one hundred and seventy-four patients (198 cups) were available for assessment. All patients underwent detailed physical and radiographic examination; their functional status was evaluated according to the Harris Hip Score (HHS). Following their digitization, all radiographs were further reviewed in order to determine the existence of any migration of the acetabular cup. Osteolytic lesions, radiolucent lines or zones of increased bone density were also recorded and classified according to the system of DeLee & Charnley. The modified Engh's criteria were used in order to evaluate the stability of the prosthesis. The patients' mean HHS at their latest follow-up visit (97.24 points) was statistically significantly better than the preoperative mean score of 40.31 points (p<0.001). Radiographic analysis showed "stable with bone ingrowth" fixation (modified Engh's criteria) of all implants with no significant migration of the cup (mean cranial migration: 0.597 mm, mean horizontal migration: 0.607 mm, mean observed difference of the cup's inclination angle: 0.26 degrees). No areas of significant osteolysis were found. The cumulative survival rate of the implants was 97.05%. Our results suggest that second generation hydroxyapatite-coated threaded acetabular cups can be successfully implanted (and achieve excellent results) without the use of any supplementary supporting screws.