Determining congruence of the standard hemispherical acetabular component and post-traumatic acetabulum in primary total hip arthroplasty (experimental study)

Introduction An original ASPID classification was developed for primary total hip arthroplasty in the presence of post-traumatic acetabular deformity at the Vreden National Medical Research Centre for Traumatology and Orthopaedics. We aimed to explore how the extent of displacement and localization of acetabular deformity as classified by the original ASPID grading system can affect the coverage area of the acetabular component. The purpose of the study was to determine the congruence of the standard hemispherical acetabular component and the post-traumatic acetabular deformity in the experiment. Material and methods Computer 3D models of 92 post-traumatic acetabulums were formed, followed by simulated implantation of a standard hemisphere of the appropriate size in compliance with permissible values of the spatial orientation of the acetabular cup in total hip replacement. The congruence of the deformed acetabulum and the standard hemisphere of the corresponding size was determined with simulated implantation. Formula for the acetabular deformity was determined for each case using the original classification. With formula identified for each acetabular deformity and the magnitude of congruence, the data were compared to determine the relationship between congruence, bone displacement and the extent of bone displacement. Results The mean congruence value in the group was 59.5 ± 16.83 %. The sum of the scores A+S+P+I+D was compared with the percentage of congruence. The statistical analysis showed that the congruence of the hemispherical acetabular component and the post-traumatic acetabulum was less than 70% with a sum of parameters greater than four. The continuation of the study will allow for a more global analysis and identification of more patterns to improve surgical approaches to primary total hip arthroplasty in specific cases. Conclusion Screws can be recommended for reliable primary mechanical fixation of the pelvic component in target patients, and cavitary bone defects can be repaired with autobone chips to allow greater congruence at the bone-implant interface.