Aims: This prospective study investigated the possibilities of substitute osteointegration in an unfavourable environment. Methods: 26 patients aged 57 to 92 years (average 80) have been followed up from 6 to 24 months with serial AP and lateral X-rays. The acetabular damages were: 2 SOFCOT grade I, 9 grade II, and 15 grade III.Granules ofTriosite¨ þlled the cavitary defects mixed with and covered by cancellous bone. One pack was used 13 times; two,6 times; three, 6 times; and four, once. An HA coated hemispherical cementless cup was pressþtted, stable without screws 8 times. Results: In other cases the acetabular cup remained stable without any lucency. Disappearance of the granules was observed only 4 times. In 14 cases osteo-integration seemed in progress, but the granular shape was still discernable. In 8 cases, even at 2 years follow-up, the granules were well visible (those were cases of grade III defects). Conclusion: In acetabular revision of a total hip replacement, the size of the defect may need a large amount of cancellous autograft. Bone substitutes seem an elegant means of sparing the patientñs bone. The rstþpapers on this topic seemed rather enthusiastic, but our experience is more contrasted. It seems that the speed of resorption of this bone substitute be volume-dependant: the bigger the defect, the slower the osteo-integration. May be growth factors should be added to speed up the process.