Patient Reported Outcome Measures ( PROMs ) at six months have been investigated but have not been vali date d against long-term outcomes .
EBRA can be used to investigate acetabular wear but not femoral migration .
OBJECTIVES High failure rates of metal-on-metal hip arthroplasty implants  have highlighted the need for more careful introduction and monitoring of new implants and for the evaluation of the safety of medical devices .
The National Joint Registry and other regulatory services are unable to detect failing implants at an early enough stage .
We aim ed to identify vali date d surrogate markers of long-term outcome in patients undergoing primary total hip arthroplasty ( THA ) .
Early migration and late aseptic failure of proximal femoral prostheses.
The  vertical migration of four configurations of a proximal femoral prosthesis , followed for up to nine years , was measured on st and ard radiographs . The same implant was used without cement ( group 1 ) and with cement ( group 2 ) . The migration of both groups was linear from six months onwards . The mean migration rate and the incidence of late aseptic loosening were both greater in group 1 . Survival analysis of the two groups , however , showed no statistically significant difference . In both groups , hips later destined for revision migrated more rapidly from the initial postoperative period onwards , than did the remainder . A threshold migration of 1.2 mm/year during the first two years after implantation detected hips likely to fail with a specificity of 86 % and a sensitivity of 78 % . This ' migration test ' was applied to the results in two further groups of patients in which a modified femoral prosthesis had been implanted without hydroxyapatite coating ( group 3 ) and with hydroxyapatite coating  ( group 4 ) . The test distinguished between the four groups and suggested that at least two fixation procedures should be ab and oned . We conclude that vertical migration measured on st and ard radiographs in the first two years after implantation can be used to predict late aseptic loosening . New prosthetic configurations should be evaluated by migration measurements before their general release . Our observations support the view that one cause of late aseptic loosening is imperfect initial fixation
Patient Reported Outcome Measures ( PROMs ) at six months have been investigated but have not been vali date d against long-term outcomes .
EBRA can be used to investigate acetabular wear but not femoral migration .
OBJECTIVES High failure rates of metal-on-metal hip arthroplasty implants  have highlighted the need for more careful introduction and monitoring of new implants and for the evaluation of the safety of medical devices .
The National Joint Registry and other regulatory services are unable to detect failing implants at an early enough stage .
We aim ed to identify vali date d surrogate markers of long-term outcome in patients undergoing primary total hip arthroplasty ( THA ) .