1.1   This guide covers materials and design recommendations and general test methods for the chemical, mechanical, and preclinical assessment of implantable devices with hard-on-hard articulations intended to replace a hip joint. The provided guidance is intended to encompass both Total Hip Replacement (THR) devices with stems that extend or fix within the intramedullary canal as well as Hip Resurfacing Arthroplasty (HRA) wherein only the hip articulating surfaces are replaced. There has been long term clinical experience with metal-on-metal articulating components manufactured from cobalt-28 % chromium-6 % molybdenum (Co28Cr6Mo) alloy (Specifications F75, F799, or F1537) or high purity alumina (ISO 6474‑1) and ceramic-on-ceramic articulating components manufactured from high purity alumina (ISO 6474‑1) or alumina matrix composite ceramics (ISO 6474‑2). There has also been some limited clinical experience with metal (Co28Cr6Mo) on alumina matrix composite ceramic articulating components. This guide has been created based on the current understanding derived from those clinical histories. Device articulating components manufactured from other metallic alloys, ceramics or with coated or elementally modified articulating surfaces could also be evaluated with this guide. However, such materials that do not have a history of clinical use may present different risks.