INTERPRETATION The guidelines have improved method ological reporting in RSA studies , but adherence to these guidelines is still relatively low .
BACKGROUND AND PURPOSE Guidelines for st and ardization of  radiostereometry ( RSA )  of implants were published in 2005 to facilitate comparison of outcomes between various research groups .
In this systematic review , we determined how well studies have adhered to these guidelines .
Segment choice and cup stability influence wear measurements using radiostereometric analysis: a radiostereometric study comparing wear measured by markers in the polyethylene with markers in the periacetabular bone.
BACKGROUND Radiostereometry is a well documented method to measure the polyethylene wear after total hip replacements . Wear is measured according to the point motion of the head center in relation to the polyethylene as the reference segment . Increasing head sizes and new cup material s may diminish visibility of markers deteriorating the segment and leading to study drop outs . Alternatively markers in the periacetabular bone may be easier to detect rendering this segment more stable . Our aim was to compare wear measurements against the cup , the acetabuluar bone and a calculated wear estimation including cup migration . METHODS A prospect i ve r and omized controlled trial comparing reverse hybrid with cemented total hip replacement was conducted . 31 patients had tantalum markers in the polyethylene and in the periacetabular bone  making it possible to measure wear using both as reference segments . We used a uniplanar radiostereometric technique . FINDINGS Wear in the y-axis was overestimated by 53 % when markers in the periacetabular bone were used ( P<0.001 ) . Proximal wear was 0.34 mm ( 95 % CI of mean : 0.29 - 0.38 ) when using the polyethylene as the reference and 0.52 mm ( 95 % CI of mean : 0.38 - 0.65 ) using the acetabular bone . Migration of the cup seemed to influence the wear calculations , overestimating wear when markers in the periacetabular bone were used as the reference segment . INTERPRETATION Wear measured with periacatebular bone markers is influenced by cup migration , overestimating wear measurements . We therefore recommend not using the acetabular bone as the reference segment
INTERPRETATION The guidelines have improved method ological reporting in RSA studies , but adherence to these guidelines is still relatively low .
BACKGROUND AND PURPOSE Guidelines for st and ardization of  radiostereometry ( RSA )  of implants were published in 2005 to facilitate comparison of outcomes between various research groups .
In this systematic review , we determined how well studies have adhered to these guidelines .