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 .
Hydroxyapatite-Coated Total Hip Femoral Components in Patients Less Than Fifty Years Old. Clinical and Radiographic Results after Five to Eight Years of Follow-up*
One hundred and thirty-three patients ( 152 hips ) who were an average of thirty-nine years old ( range , sixteen to forty-nine years old ) received a proximally hydroxyapatite-coated femoral prosthesis as part of a total hip arthroplasty and were followed for a minimum of five years ( average , 6.4 years ; range , five to 8.3 years ) or until revision . The average Harris hip score was 47 points ( range , 22 to 77 points ) preoperatively and 93 points ( range , 49 to 100 points ) at the time of the latest clinical evaluation . Two patients who had a well fixed femoral implant had activity-limiting pain in the thigh at the time of the most recent examination . Radiographic changes consistent with bone-remodeling ( cortical hypertrophy and bone condensation ) typically were seen around the mid-part of the shaft of the prosthesis . Forty-eight ( 32 per cent ) of the 148 hips that were included in the radiographic analysis demonstrated a small amount of erosive scalloping in either zone 1 or zone 7 of Gruen et al. , and intramedullary osteolysis was suspected in only one hip . All stems were radiographically osseointegrated according to a modification of the criteria described by Engh et al. Four stems were revised , but none of the revisions were performed because of mechanical failure ( two stems were revised in conjunction with a revision of the cup because of pain ; one , because of an infection ; and one , after a traumatic femoral fracture that occurred six years postoperatively ) . Thus , the rates of aseptic and mechanical failure were both 0 per cent . The combined rate of failure , which included the two stems that were revised because of pain and the two stems that were associated with pain that limited activity , was 2.6 per cent ( four of 152 stems ) . The over-all clinical results associated with hydroxyapatite-coated femoral components were excellent in this group of young patients after intermediate-term follow-up . A review of serial radiographs showed mechanically stable implants with osseous ingrowth , evidence of stress transmission at the middle part of the stem , and minimum endosteal osteolysis
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 .