There is a need for standardization of radiostereometric (RSA) investigations to facilitate comparison of outcome reported from different research groups. In this document, 6 research centers have agreed upon standards for terminology, description and use of RSA arrangement including radiographic set-up and techniques. Consensus regarding minimum requirements for marker stability and scatter, choice of coordinate systems, and preferred way of describing prosthetic micromotion is of special interest. Some notes on data interpretation are also presented. Validation of RSA should be standardized by preparation of protocols for assessment of accuracy and precision. Practical issues related to loading of the joint by weight bearing or other conditions, follow-up intervals, length of follow-up, radiation dose, and the exclusion of patients due to technical errors are considered. Finally, we present a checklist of standardized output that should be included in any clinical RSA paper.This document will form the basis of a detailed standardization protocol under supervision of ISO and the European Standards Working Group on Joint Replacement Implants (CEN/TC 285/WG4). This protocol will facilitate inclusion of RSA in a standard protocol for implant testing before it is released for general use. Such a protocol-also including other recognized clinical outcome parameters-will reduce the risk of implanting potentially inferior prostheses on a large scale.

The tibial components in 143 patients with total knee replacements performed before 1988 were assessed for micromotion using roentgen stereophotogrammetric analysis (RSA) over a period of 13 years. The fixation of the prostheses remained clinically sound in all cases, although revision had been required for other reasons in seven.

We measured levels of cartilage proteoglycan (PG) fragments in knee joint synovial fluid obtained from patients with previous trauma of the knee, early gonarthrosis, or pyrophosphate synovitis, and in agematched control subjects. During the initial 3-4 weeks after rupture of the anterior cruciate ligament or the meniscus (confirmed by arthroscopy), markedly increased PG fragment levels were found. At later times after trauma (up to 4 years), many of these patients still had significantly elevated levels of cartilage PG fragments in the joint fluid. In a group of older patients with gonarthrosis, these levels were only moderately elevated, while in patients with acute pseudogout, greatly increased levels were observed. Although longitudinal studies are needed to validate the significance, PG fragments in joint fluid may be a marker for early posttraumatic arthrosis.Arthrosis (osteoarthritis) is a slowly progressive disease of apparently multifactorial etiology. The

Objective-To assess the effects of intraarticular injections of hyaluronan on symptoms ofknee osteoardtritis (OA).