Hip arthroplasty with a Moore prosthesis with porous coating. A five-year study.

The five-year clinical experience with Moore hip prostheses with a porous coating has been encouraging. The results have been equivalent to those of a simultaneous experience using cemented prostheses. The patient population chosen for hip arthroplasty using prostheses with a porous coating was a group at high risk for failure with cemented prostheses. The mean Harris hip ratings for the 26 patients have improved rather than deteriorated with time. Based on current knowledge, it is the author's opinion that the implants in these 26 patients were firmly fixed by a combination of fibrous and bony tissue ingrowth. The presence of radiopaque lines in one-third of the patients at a two-year follow-up examination indicates that micromotion often was present. Close inspection of the three- and four-year follow-up roentgenograms reveals that the tissue ingrowth seems to have provided implant fixation sufficiently uniform to prevent the roentgenographic signs of localized high-stress concentration so frequently seen with smooth-stem Moore prostheses of the same design. The tissue ingrowth also has produced stress transfers sufficiently uniform to provide roentgenographic signs of healthy bone modeling. With four-year follow-up roentgenograms now available in ten patients, there has been no roentgenographic evidence of bone resorption due to femoral stress shielding by the relatively high-modulus implant with a porous surface.