Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Hip Reconstruction Uncemented hydroxyapatite-coated stems for primary total hip arthroplasty David C. Markel and Petra J. Gheraibeh INTRODUCTION A s a result of dissatisfaction with cemented arthroplasty components in the mid-1970s, and a desire to have more bone friendly prosthesis, a movement started to develop cementless components. Uncemented arthroplasty was desired to create a strong, responsive interface between implant and bone. The interface would hopefully have long- term stability and be capable of remodeling in response to physical and biologic demands. 1 Uncemented Femoral Stems Many different stem designs relative to metallurgy, shape, surface preparation and patterning, and mechanical proper- ties have been utilized effectively over the development phases leading to today’s designs. The stem’s surface prep- aration may be the most fundamental issue as it relates to bony ingrowth or ongrowth. While the use of extensively coated stems in the primary situation have, for the most part, been abandoned due to issues of proximal bone loss due to stress shielding, virtually all primary stems have evolved to include a proximal circumferential surface coating. This coat- ing can promote circumferential ingrowth and proximal load transfer and prevents migratory osteolysis. 1–11 Despite reliable performance of the early ingrowth and ongrowth stems, the vast majority of current primary stems now include the addition of a ceramic material such as hydro- xyapatite to promote osteoconduction. 12 The Movement to Ceramic Coatings The use of porous ceramic materials to promote bony ingrowth for implants may be attributed to Hulbert et al. 13 who noted decreased pain and radiolucent lines in associ- ation with metallic prostheses. Similarly, Soballe demon- strated that despite micromotion that would otherwise deter bony ingrowth and encourage fibrous tissue formation, porous implants with hydroxyapatite coatings had a more significant bone response and developed a stronger interface compared to implants without an hydroxyapatite coating. It was also noted that more complete and reproducible gap filling occurred in the presence of hydroxyapatite. 12,14– 26,27,28–39 Hydroxyapatite Hydroxyapatite is a naturally occurring calcium apatite [Ca 5 (PO 4 ) 3 (OH)]. Bulk hydroxyapatite is manufactured from a powder then converted into a usable ceramic by mixing with hydrogen peroxide. 16 The hydroxyapatite is SPECIAL FOCUS ABSTRACT Purpose of review The review is intended to describe the most recent evidence surrounding the use of hydroxyapatite-coated uncemented femoral stems. Recent findings Until recently, the research on hydroxyapatite-coated femoral stems has been limited to retrospective and prospective studies with short-term follow-up. Recently, several authors have pub- lished 10 – 15-year follow-up data that are very promising. Hydro- xyapatite is a good adjunct for fostering bony ingrowth and ongrowth of femoral components. This in turn results in less pain, faster onset of implant stability, and a lower incidence of aseptic loosening. Summary A proximally coated press-fit femoral component augmented with a hydroxyapatite coating provides predictable outcome and may be favored as a state of the art or gold standard for primary hip arthroplasty. Keywords hip arthroplasty, hip stem, hydroxyapatite, stem coatings, uncemented total hip arthroplasty Providence Hospital and Detroit Medical Center, Southfield, Michigan, USA Correspondence to David C. Markel, MD, Providence Hospital and Detroit Medical Center, 22250 Providence Drive, Southfield, MI 48075, USA Tel: +1 248 569 0306; fax: +1 248 569 0364; e-mail: dmarkel@providence-hospital.org Reprinted from Current Opinion in Orthopaedics 2008, 19:16–20 1940-7041 ß 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins Volume 19  Number 2  March/April 2008 Current Orthopaedic Practice 119