Revision Hip Arthroplasty : Impaction Bone Grafting and Low-Dose CT-Based Measurements of Bone Density and Migration

Abstract: Aseptic loosening of total hip replacements is always associated with bone defects, either due to removal of the existing implant or osteolysis. Bone defects can be handled during revision surgery with impaction bone grafting (IBG). Allograft bone is morcellized, washed, and impacted into the defects, after which the new implant is cemented upon the grafted bone. For succesful incorporation, mechanical stability and load are key factors. Femoral IBG was developed for the polished tapered collar-less Exeter stem.The hypothesis in paper I was that additional compression of the acetabular bone graft, with a titanium shell, would increase stability and render good clinical results. 170 patients were systematically reviewed at seven years in mean. Kaplan-Meier analysis showed a ten-year prosthetic survival (all causes) at 92%.The hypothesis in paper II was that femoral IBG works with the matte cemented Lubinus SPII stem. 69 patients were reviewed at a mean time of seven years. With re-operation for any reason as endpoint, the Kaplan-Meier analysis showed a prosthetic survival rate of 93%. The grafted bone was incorporated in most cases. The rate of periprosthetic fractures was 4% and these were all treated with osteosynthesis.In paper III we examined if it would be possible to measure bone mineral denisty and prosthetic migration simultaneously with CT-examinations. 17 patients were followed for two years. The CT-examinations were able to measure prosthetic migration and bone mineral density.In paper IV the precision of CT-based migration analysis was evaluated. Patients from three different clinical trials were analyzed. Analysis was made with and without tantalum markers in the bone. Precise prosthetic migration analysis based on CT-scans was possible, even without tantalum markers.In conclusion, CT-scans can measure prosthetic migration with high precision without tantalum markers in the bone. The scans can simultaenously measure bone mineral density. CT-scans have great diagnostic potential for hip arthroplasty patients. Acetabular IBG, combined with a compressive titanium shell, is safe to use and may enhance incorporation due to increased stability. Femoral IBG works well also with a matte collared and anatomical cemented stem.