Revision, without cement, of aseptically loose, cemented total hip prostheses. Quantitative comparison of the effects of four types of medullary treatment on bone ingrowth in a canine model.

Publisher Website
Google Scholar
Abstract
A model that replicated the radiographic and histological features of aseptic loosening of the femoral component of a total hip replacement that had been done with cement was created in thirty-seven dogs. A deep wound infection developed in one dog, and that dog was excluded from the study. Revision was performed without cement in twenty-nine dogs, which were then followed for six months. The remaining seven dogs were used for histological study only. The components that were used for revision were made from Ti-6-Al-4-V, and a titanium fiber-metal porous surface had been applied to the anterior, posterior, and medial surfaces of the proximal part of the stem. The femora were revised either with no graft material applied to the osseous defect; with hydroxyapatite/beta-tricalcium phosphate placed in the defect; with application of an autologous cancellous bone graft as part of a one-stage revision; or with application of an autologous cancellous bone graft as the first part of a two-stage revision, with implantation of the component four months later. The use of an autologous bone graft led to greater and more consistent ingrowth of bone.The greatest amount of bone ingrowth was found in the group in which the procedure had been done in two stages (18 +-\4.1 per cent), followed by the group in which the prosthesis and the graft had been inserted in a single stage (15 +-\5.0 per cent), the group that had been treated with hydroxyapatite/beta-tricalcium phosphate (10 +-\9.1 per cent), and the control group, in which no graft had been used (7 +-\7.0 per cent). Notably, all of the components in the animals in which an autologous graft had been used were well fixed by bone ingrowth, while the component in two of the animals in the group in which no graft had been used and in one animal in the hydroxyapatite/beta-tricalcium phosphate group had only fibrous-tissue ingrowth. In contrast to the findings with respect to bone ingrowth, there was more medullary bone adjacent to the lateral aspect of the implant in the groups in which hydroxyapatite/beta-tricalcium phosphate or no graft had been inserted than in the groups that had had an autologous graft. This may have been due to the development of sclerotic reactive bone in the groups that had had hydroxyapatite/beta-tricalcium phosphate or no graft, as a consequence of less bone ingrowth and--by inference--decreased stability of the implant, rather than it having been a reflection of the inherent effects of these types of treatment on medullary defects. Aseptic failure of a cemented femoral stem leads to replacement of normal cortical and medullary bone and marrow by inflammatory and granulation tissue, thereby reducing the osteogenic potential of the medullary canal and decreasing the likelihood of fixation by bone ingrowth. The fact that the use of autologous bone graft in a one or two-stage procedure led to more bone ingrowth than the use of hydroxyapatite/beta-tricalcium phosphate underscores the importance of an environment with suitable osteogenic potential if fixation by bone ingrowth is to be obtained.