Standard Guide for Gravimetric Wear Assessment of Prosthetic Hip-Designs in Simulator Devices

1.1 This guide describes a laboratory method using a weight-loss technique for evaluating the wear properties of materials or devices, or both, which are being considered for use as bearing surfaces of human-hip-joint replacement prostheses. The hip prostheses are evaluated in a device intended to simulate the tribological conditions encountered in the human hip joint, for example, use of a fluid such as bovine serum, or equivalent pseudosynovial fluid shown to simulate wear mechanisms and debris generation as found in vivo, and test frequencies of 1 Hz or less.

1.2 Since the hip simulator method permits the use of actual implant designs, materials, and physiological load/motion combinations, it can represent a more physiological simulation than basic wear-screening tests, such as pinion-disk (see Practice F 732) or ring-on-disk (see ISO-6474).

1.3 It is the intent of this guide to rank the combination of implant designs and materials with regard to material wear-rates under simulated physiological conditions. It must be recognized, however, that there are many possible variations in the in vivo conditions, a single laboratory simulation with a fixed set of parameters may not be universally representative.

1.4 The reference materials for the comparative evaluation of candidate materials, new devices, or components, or a combination thereof, shall be the wear rate of extruded or Compression-molded, ultra-high molecular weight (UHMW) polyethylene (see Specification F 648) bearing against standard counter faces Stainless Steel (see Specification F 138); cobalt-chromium-molybdenum alloy (see Specification F 75); thermomechanically processed cobalt chrome (see Specification F 799); alumina ceramic (see Specification F 603), having typical prosthetic quality, surface finish, and geometry similar to those with established clinical history. These reference materials will be tested under the same wear conditions as the candidate materials.