CLINICAL AND ROENTGENOGRAPHIC EVALUATION OF HYDROXYAPATITE-AUGMENTED AND NONAUGMENTED POROUS TOTAL HIP-ARTHROPLASTY

Sixty osteoarthritic patients undergoing primary, uncemented total hip arthroplasty were matched for age and weight and randomized into one of four groups with respect to implant coating and postoperative, prot ected weight-bearing status: group 1, hydroxyapatite-augmented, 12 wee ks; group 2, nonaugmented, 12 weeks; group 3, hydroxyapatite-augmented , 6 weeks; and group 4, nonaugmented, 6 weeks. Tantalum spheres were i mplanted periprosthetically into the femur at the time of the arthropl asty, thus providing constant references for stereoscopic radiographs. Patients were then evaluated over a 2-year period with clinical exami nation, plain radiography, and roentgen stereophotogrammetric analysis . Clinical evaluation using the Charnley scoring system showed no sign ificant preoperative or postoperative intergroup differences, whereas visual analog testing noted less thigh pain with hydroxyapatite-augmen ted stems at the Ii-week and 6-month follow-up evaluations. Plain radi ographic analysis produced no significant differences, with no instabi lity detected, and bony ingrowth was uniform in all groups. Stereograp hic evaluation showed migration in all groups, but there were no signi ficant differences between the augmented and nonaugmented stems or the 6-week and 12-week partial weight-bearing protocols. Charnley, plain radiographic, and stereogrammetric evaluations all suggest that migrat ion is unaltered by enhanced surfaces and early, unprotected weight be aring does not jeopardize implant fixation regardless of coating desig n. The lower incidence of visual analog thigh pain with the hydroxyapa tite-augmented stems, however, may be a reflection of bony ingrowth an d, as such, add some validity to the theoretic advantages of enhanced surface prostheses.