Patients experienced significant post-THR improvements in Harris Hip scores , but this did not differ between impact types .
Recipients of cross-linked vs. conventional polyethylene cup liners experienced reduced femoral head penetration and revision .
There was no impact of femoral stem fixation and cup shell design on implant survival rates .
Evidence on mortality and complications ( aseptic loosening , femoral fracture ) was inconclusive .
BACKGROUND Evolvements in the design , fixation methods , size , and bearing surface of implants for  total hip replacement ( THR ) have led to a variety of options for healthcare professionals to consider .
The need to determine the most optimal combinations of THR implant is warranted .
This systematic review evaluated the clinical effectiveness of different types of THR used for the treatment of end stage arthritis of the hip .
Pitfalls in randomized surgical trials.
Special problems may arise when the principles of the r and omized trial are used to compare operative methods . In the trial design that is used at present , each surgeon performs the operatons to be compared in a r and om order . A prerequisite for a trial so design ed to result in a fair comparison is that the participating surgeons are equally conversant with both techniques . If they are not , the design may imply systematic bias in favor of operations that are in wide use and bias in favor of technically simple procedures . An alternative to this design is given . Reports on trials should contain information about pretrial routine and level of training of participants
Patients experienced significant post-THR improvements in Harris Hip scores , but this did not differ between impact types .
Recipients of cross-linked vs. conventional polyethylene cup liners experienced reduced femoral head penetration and revision .
There was no impact of femoral stem fixation and cup shell design on implant survival rates .
Evidence on mortality and complications ( aseptic loosening , femoral fracture ) was inconclusive .
BACKGROUND Evolvements in the design , fixation methods , size , and bearing surface of implants for  total hip replacement ( THR ) have led to a variety of options for healthcare professionals to consider .
The need to determine the most optimal combinations of THR implant is warranted .
This systematic review evaluated the clinical effectiveness of different types of THR used for the treatment of end stage arthritis of the hip .