The Charnley prosthesis had by far the best and most comprehensive evidence base with better than 90 % implant survival after about 10 years .
Some uncemented stems have shown promising medium-term outcome , but no combination of uncemented cup and stem fulfilled the benchmark criterion of > or = 90 % implant survival at 10 years , which we propose as a minimum requirement for unrestricted clinical use for prostheses used in primary THR .
We have conducted a systematic review of the scientific literature concerning outcome and clinical effectiveness of  prostheses used for primary total hip replacement ( THR ) in Norway .
Comparison of collared and collarless femoral components in primary uncemented total hip arthroplasty.
Two hundred three consecutive primary uncemented total hip arthroplasties were prospect ively r and omized using collared and collarless versions of an identical titanium stem . Identical 28-mm titanium heads were implanted in all cases .  One hundred three collared hips  were compared with 100 collarless hips .  Follow-up periods averaged 45.7 months in both groups . Intraoperative , early , and late complications were similar . Hip scores , including thigh pain , at final follow-up visit were also similar . No significant differences were noted in acetabular or femoral radiolucencies , subsidence , osteolysis , or proximal femoral remodeling . At 5 years , more collarless stems revealed pedestal formation ( 57.1 % vs 33.9 % ) . The presence of a collar had no effect on the adequacy of fixation , proximal femoral osteopenia , or clinical scores at 5 years
The Charnley prosthesis had by far the best and most comprehensive evidence base with better than 90 % implant survival after about 10 years .
Some uncemented stems have shown promising medium-term outcome , but no combination of uncemented cup and stem fulfilled the benchmark criterion of > or = 90 % implant survival at 10 years , which we propose as a minimum requirement for unrestricted clinical use for prostheses used in primary THR .
We have conducted a systematic review of the scientific literature concerning outcome and clinical effectiveness of  prostheses used for primary total hip replacement ( THR ) in Norway .