Mid-Term Results of Ceramic Monoblock Acetabular Cups in Primary Total Hip Arthroplasty: A Minimum 5-Year Follow-Up

Introduction: Ceramic-on-ceramic (CoC) articulation in total hip arthroplasty (THA) offers excellent wear characteristics but carries risks such as liner malseating and ceramic fracture. To solve these problems, monoblock acetabular cups with preassembled ceramic liners were developed to minimize technical errors and allow the use of larger femoral heads. This study aimed to evaluate the mid-term clinical and radiological outcomes of a ceramic monoblock acetabular cup system. Methods: A retrospective analysis was performed on 106 primary THAs in South Korean patients using the Maxera monoblock cup (Zimmer Biomet) between 2015 and 2018, with a minimum follow-up of 5 years. Clinical outcomes were assessed using the Harris Hip Score (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Visual Analog Scale (VAS). Radiologic evaluation included osteolysis and radiolucent lines. Normality of clinical variables was confirmed, and pre-to-postoperative comparisons were performed using paired t-tests. Results: The mean follow-up was 6.8 ± 1.4 years. The most common preoperative diagnosis was avascular necrosis (66.0%). Cups sized ≤52 mm were used in 80.2% of hips, allowing the frequent use of large femoral heads (32-40 mm). Clinical scores improved significantly: HHS from 37.0 ± 13.4 to 90.8 ± 6.2, WOMAC from 66.6 ± 11.5 to 7.6 ± 6.7, and VAS from 6.45 ± 1.1 to 1.1 ± 0.8 (p < 0.001). No osteolysis was observed. Radiolucent lines was appeared in four hips (3.7%) without evidence of migration or loosening. One cup fixation failure (0.9%) required revision. No cases of ceramic fracture, squeaking, or dislocation occurred. Conclusions: The ceramic monoblock acetabular cup demonstrated excellent mid-term clinical and radiological outcomes with a very low complication rate. The ability to reliably use large femoral heads likely contributed to enhanced joint stability. However, the absence of screw fixation and inability to directly visualize cup insertion require careful attention during cup impaction. Long-term studies with comparative cohorts are warranted.