BACKGROUND: In order to enhance the rate and degree of osseointegration of cementless implants, hydroxyapatile(HA) was applied on the different prosthesissurfaces. Themajoritiesofthesestudieshaveutilized non-weight-bearing in vivo dog models and have focused on the fixation of the femoral component. What is the osseointegration of macrotextured acetabular components in a weight-bearing model(dog) like?OBJECTIVE:To evaluate the various macrotextured surface coatings applied to acetabular components of the same design in aweight-bearing canine total hip replacement model.DESIGN: Randomized conparative study using theexperimentalanimals as subjectsSETTING: Department of Ortopaedics, Beijing Tongren Hospital;PathologyDepartment, Bone and Joint Laboratory,St. Michael' s Hospital, U of T,Toronto,CanadaMATERIALS: The experiment was completed in the Pathology Department,Bone and Joint laboratory, St. Michael' s Hospital, U of T, Toronto, Canada from October 2001 to December 2001. Acetabular components with the selected surface characteristics were implanted into forty dogs with the body mass of 29 - 44 kg of either gender and divided into seven groups, including group 1 (AD/HA), Group 2 (CoCr beads/PA), Group 3 (CPTi bead surface),Group 4(CPTi 30 PPI foam),Group 5(CPTi 30 PPI/PA foam),Group 6(CPTi 40 PPI foam), Group 7(CPTi 40 PPI/PA foam).METHODS: Exercise was restricted to leash walks for the first fourteen days post-operatively. After this, dogs were allowed unrestricted activity. The dogs were euthanized at either three or sixmonths after surgery as the project' s protocol. The whole acetabulum,divided into weight-bearing and non weightbearing areas, containing the component was harvested and submitted for histological and histomorphological assessment. MAIN OUTCOME MEASURES:The bone ongrowth and ingrowth with weight bearing and without weight bearing areas in each group.RESULTS:There was significantly greater bone apposition and bone ingrowth for implants withHAcoatingsascompared to uncoated implants. There was also significantly greater bone ingrowth in weight-bearing areas as compared tonon weight-bearing areas at both time periods. The bone growth into AD/HA was 17％ at 3 months and descended to 14％ at 6 months. The bone growth into CPTi beads surface was 21％ at 3 months,30％ at 6months in weight-bearing areas. All four foam-coating surfaces there were 15％ to 21％ ongrowth at 3 months,15％ to 32％ at 6 months and 21％to 32％ingrowth at 3 months,29％to 45％at 6 months in weight-bearing areas( P ＜ 0.05).CONCLUSION: Hydroxyapatite coating produces significantly greater boneingrowth andappositionin all thesurfacetreatmentstestedinthis study. Weightbearingproducesagreater boneingrowththannon weight-bearing areas and obviously increases with the time prolonging, especially the foam coating