Revision and complex primary total hip arthroplasty with impaction bone grafting for acetabular defects: medium-term results

Background. Impaction bone grafting remains an alternative method for managing bone deficiency. Cyclic loads on the allograft may cause its further compaction and deformation, leading to migration of the acetabular component. The aim of this study — to evaluate the effectiveness and refine the indications for the use of impaction bone grafting for acetabular defects in revision and complex primary total hip arthroplasty by assessing the mid-term survival of implanted cemented acetabular components. Methods. We performed a retrospective analysis of the results of impaction bone grafting in 48 patients whose data were available for the assessment of acetabular component survival. Radiographic data were analyzed in 42 cases, clinical outcomes were assessed in 44 cases. Structure of operations was represented by 37 revisions and 5 cases of complex primary hip arthroplasty. The average follow-up period was 60 months. We assessed radiographic signs of cup migration, loosening and bone allograft remodeling. Kaplan-Meier survival analysis with 95% confidence intervals was performed. Results. The general survival of acetabular components was 97.9% (95% CI: 97.86-97.94) for 60 months and 84.3% (95% CI: 84.15-84.43) for 90 months. In 4 (7.4%) cases, we recorded an unsatisfactory result. In 7 cases, radiolucent lines without clinical signs of loosening were detected. In 22 (52.3%) cases a simultaneous change in inclination and cranial displacement of the rotation center were noted. In isolated assessment of inclination, changes were noted in 24 (57.1%) cases. We found a direct correlation between the acetabular component migration, defect severity and the use of a containment device (p = 0.006), as well as between the displacement of the rotation center by more than 5 mm and the inclination by more than 10° in 91.7% of cases (p 0.0001). The median functional assessment according to the Hip Harris Score showed 85.50 [70.5; 95.0] points and 6.5 [2.0; 21.0] points according to the WOMAC questionnaire. Conclusions. Impaction bone grafting is a method of choice for limited bone defects replacement. Migration of the cup, displacement of the rotation center by more than 5 mm and an increase in its inclination by more than 10° can be regarded as a conditional norm due to natural biomechanical processes, which is confirmed by high medium-term survival rates of the implant according to clinical data.