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 .
Randomised controlled trial comparing early migration of two collarless polished cemented stems using radiostereometric analysis.
This was a safety study where the hypothesis was that the newer- design CPCS femoral stem would demonstrate similar early clinical results and micromovement to the well-established Exeter stem . Both are collarless , tapered , polished cemented stems , the only difference being a slight lateral to medial taper with the CPCS stem . A total of 34 patients were enrolled in a single-blinded r and omised controlled trial in which 17 patients received a dedicated radiostereometric CPCS stem and 17 a radiostereometric Exeter stem .  No difference was found in any of the outcome measures pre-operatively or post-operatively between groups . At two years , the mean subsidence for the CPCS stem was nearly half that seen for the Exeter stem ( 0.77 mm ( -0.943 to 1.77 ) and 1.25 mm ( 0.719 to 1.625 ) , respectively ; p = 0.032 ) . In contrast , the mean internal rotation of the CPCS stem was approximately twice that of the Exeter ( 1.61 degrees ( -1.07 degrees to 4.33 degrees ) and 0.59 degrees ( 0.97 degrees to 1.64 degrees ) , respectively ; p = 0.048 ) . Other migration patterns were not significantly different between the stems . The subtle differences in design s may explain the different patterns of migration . Comparable migration with the Exeter stem suggests that the CPCS design will perform well in the long term
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 .