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 .
Remodeling of Bone around Hydroxyapatite-Coated Femoral Stems*
Two hundred and twenty-four total hip arthroplasties were performed in 201 patients with use of a femoral component with hydroxyapatite coating of the proximal portion of the stem . The mean duration of follow-up was seventy-one months ( range , fifty-eight to eighty-seven months ) . Of the 224 arthroplasties , 208 ( 93 per cent ; 190 patients ) yielded a good or excellent clinical result . Four patients ( 2 per cent ) reported mild-to-moderate activity-related pain in the thigh , and two ( 1 per cent ) had aseptic loosening . The radiographic findings of progressive new-bone formation ( cancellous condensation and cortical hypertrophy ) throughout the zones adjacent to the middle and distal portions of the stem were evidence of early , extensive proximal fixation of the implant , with distal stress transfer through the implant , which is stiffer than the surrounding bone . Remodeling of the femur began early , was predictable , and progressed throughout the follow-up period . Cortical hypertrophy about the middle and distal portions of the stem occurred predominantly in the mediolateral plane ( in 105 hips [ 47 per cent ] , compared with thirteen hips [ 6 per cent ] in the anteroposterior plane ) , and it was more common in patients who had had poorer bone quality preoperatively . Intramedullary osteolysis was present in one femur ( 0.4 per cent ) at five years ; the osteolytic area was less than five millimeters in its greatest dimension and had not progressed at the time of the six-year follow-up evaluation . This low rate of osteolysis suggests that a circumferential coating of hydroxyapatite may effectively minimize migration of wear debris along the femoral stem . The progressive remodeling of the femur about the middle and distal portions of the stem , as evidence d by cancellous condensation and cortical hypertrophy , has not , to our knowledge , been described previously to this magnitude in association with proximally coated ( porous or hydroxyapatite-coated ) femoral implants
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 .