The Epidemiology of Total Hip Arthroplasty Bearing Surface Use in the United States

Introduction: Metal on conventional ultra-high molecular weight polyethylene (UHMWPE) bearings have produced excellent long-term results in total hip arthroplasty (THA), with 20 year survivorship of almost 80%. However, the consequences of bearing surface wear, including osteolysis and aseptic loosening, have been a leading cause of late revision THA, especially in younger, more active patients. Hard-on-hard “premium” bearing surfaces (ceramic-on-ceramic and metal-on-metal) offer the potential to decrease the incidence of THA revisions caused by bearing surface-related failures. Numerous laboratory studies have demonstrated substantial reductions in wear rates associated with both ceramic-on-ceramic (CoC) and metal-on-metal (MoM) bearings relative to metal-on-conventional UHMWPE bearings, and many clinical studies have demonstrated excellent shortand mid-term outcomes in patients with CoC and MoM bearings. However, the specific indications for using these advanced technologies remain controversial. Beginning in October, 2005, three new modifier codes were added to the International Classification of Diseases, 9 Clinical Modification (ICD-9-CM) procedure codes. These coding changes allow identification of the specific bearing surface used in THA procedures in large administrative databases, and therefore have enabled a large scale evaluation of bearing surface usage throughout the United States. The purpose of this study was to assess current bearing surface utilization in the United States by patient, hospital, and geographic characteristics.