National Trends in Primary Total Hip Arthroplasty in Extremely Young Patients A Focus on Bearing Surface Usage Sean S. Rajaee, MS, David Trofa, BA, Elizabeth Matzkin, MD, and Eric Smith, MD Abstract: The purpose of this study was to present national trends in primary total hip arthroplasty (THA) and bearing surface usage for patients 30 years and younger. Using the Healthcare-Cost-and- Utilization-Project Nationwide Inpatient Sample for the years 2006 to 2009, 8919 primary THA discharges (4454 coded by bearing surface) were identified in patients 30 years and younger. The most commonly used bearing surface was metal-on-metal (MoM), representing 37.6% of cases, followed by ceramic-on-ceramic (CoC) (24.6%), metal-on-polyethylene (MoP) (22.1%) and ceramic-on-polyethylene (15.7%). From 2006 to 2009, the percentage of THAs that used hard-on- hard bearing surfaces decreased (MoM: 42.9%-29.4%; CoC: 34.0%-19.7%).This decrease in hard- on-hard bearing surface usage presents a challenge for surgeons treating young patients to find other acceptable durable bearings that do not have the potential problems associated with MoM or CoC. Keywords: bearing surface, total hip arthroplasty, hip replacement, young patients, metal on metal, ceramic on ceramic, metal on polyethylene, ceramic on polyethylene. © 2012 Elsevier Inc. All rights reserved. Since the advent of modern hip arthroplasty by Sir John Charnley in the mid 1960s, total hip arthroplasty (THA) has proven to be an effective treatment for patients with hip pain due to a variety of conditions [1-4]. In the last decade, the total number of hip replacements performed annually in the United States has increased by 49% [5]. For years, the standard bearing surface used in THA has been a metallic femoral head with a smooth, high- density polyethylene acetabular liner. However, metal- on-polyethylene (MoP) articulation can wear over time, resulting in particle debris. This debris can result in an inflammatory response that can cause osteolysis and aseptic loosening. This is the primary mode of MoP failure and limits the longevity of total hip replacements [6-12]. Highly cross-linked polyethylene, which is a modification of traditional polyethylene, has proven to be superior to its former counterpart in multiple studies [13,14]. In young patients for whom implant longevity is paramount, the limitations of traditional MoP articula- tion are a considerable drawback. This is particularly true as young age and increased activity levels have been shown to be independent risk factors for aseptic loosening leading to revision THA [15]. For this reason, alternate bearing surfaces such as second generation metal-on-metal (MoM), ceramic-on-ceramic (CoC) and ceramic-on-polyethylene (CoP) are frequently used in the young patient population. The goal in developing alternate bearing surfaces has been to create a joint with decreased friction and wear rates but increased strength. However, despite all efforts to create an ideal bearing surface, every alternative has its own set of advantage and disadvantages that must be weighed in determining the optimal articulation. Hard-on-hard bearing surfaces, MoM and CoC, have been associated with improved functional outcome and reduced wear rates relative to traditional MoP [16-24]. Recent publications have even predicted that hard-on- hard bearing use is likely to increase in young and active patients [25]. Although the benefit of reducing the rate of revision surgery has yet to be conclusively demon- strated on a consistent basis, individual studies show promising outcomes. For instance, some studies have shown that at 10 or more years of follow-up, certain From the Department of Orthopedics, Tufts Medical Center/Tufts University School of Medicine, Boston, Massachusetts. Submitted December 27, 2011; accepted April 4, 2012. The Conflict of Interest statement associated with this article can be found at http://dx.doi.org/10.1016/j.arth.2012.04.006. Reprint requests: Eric Smith, MD, Department of Orthopedics, Tufts Medical Center/Tufts University School of Medicine, 800 Washington Street, Box 306, Boston, MA 02111. © 2012 Elsevier Inc. All rights reserved. 0883-5403/2710-0022$36.00/0 http://dx.doi.org/10.1016/j.arth.2012.04.006 1870 The Journal of Arthroplasty Vol. 27 No. 10 2012