A MADREPORIC-SURFACED FEMORAL COMPONENT IN A CANINE TOTAL HIP-ARTHROPLASTY MODEL - BONE REMODELING RESPONSE AT 6 AND 24 MONTHS

OBJECTIVE: To evaluate the bone-remodelling response at 6 and 24 month s after total hip arthroplasty around a two-thirds Madreporic-surfaced femoral component in a canine model. DESIGN: A research study in dogs . Statistical analysis was by multivariate analysis of variance. SETTI NG: A musculoskeletal research laboratory in a university teaching hos pital. MATERIAL: Ten mature mixed-breed dogs. INTERVENTION: Unilateral implantation of total hip arthroplasty in the right femur with a Madr eporic-surfaced prosthesis. Studies were conducted at 6 months in five dogs and at 24 months in five dogs. In each case, the nonoperated fem ur was the study control. MAIN OUTCOME MEASURES: Fluorescence microsco py analysis on comparable sections at four levels of the femora, perce nt porosity computed by image analysis, cortical atrophy. RESULTS: Can cellous hypertrophy was most prominent at the junction of the beaded a nd smooth portions of the femoral stem. At 6 months the cortex demonst rated atrophy predominant in the anteromedial quadrant. Active bone tu rnover was present within the interstices of the prosthesis at 6 and 2 4 months. No significant cortical bone loss occurred between 6 and 24 months. Stress transfer to the bone-prosthesis inter face and endostea l cortical ''cancellization'' appear to be linked phenomena.