Acetabular Bone Defect Classifications in Revision Total Hip Arthroplasty: A Systematic Review of the Literature

Acetabular bone defects pose significant challenges during revision total hip arthroplasty (rTHA) due to varying bone quality and quantity. Accurate preoperative evaluation and classification systems are essential to guide surgical planning and ensure stable acetabular fixation. Over the years, several classification systems have been proposed, each emphasizing different variables. The aim of this systematic review was to provide a comprehensive overview of existing classification systems for acetabular bone defects in rTHA. A systematic review of the literature was performed to identify all original acetabular bone defect classifications. Studies focusing solely on femoral defects and not-surgery oriented were excluded. The details of each classification system have been reviewed, and a comparison of their inter-observer and intra-observer reliability has been performed. A total of fifteen classification systems were recognized, published between 1986 and 2024. Variables taken into consideration differ considerably from classification to classification. These include defect location and pattern; the quality of remaining bone stock; the presence of ischial lysis; columns and walls integrity, the presence of pelvic discontinuity; cup loosening and/or migration; and the presence or absence of pain. All but one classification system requires intraoperative evaluation for accurate classification. While numerous classification systems for acetabular bone defects exist, none is universally accepted. Variability in the parameters assessed and the frequent need for intraoperative evaluation hinder replicability and consistency. A universally accepted, reliable classification framework remains a significant unmet need in the management of acetabular bone defects.