[Radiologic evaluation of acetabular defects on acetabular loosening of hip alloarthroplasty].

In 18 human pelvis specimens we produced different acetabular defects according to Paprosky. Standardized X-rays of these specimens were taken, and these X-rays were evaluated by six orthopaedic surgeons with different levels of surgical experience. A total of 350 evaluation sheets were analyzed. The X-rays of the acetabular rim were correctly interpreted in only 66% of cases. The interpretation of plates showing bone loss was even worse. A medial wall defect was correctly assessed in just 49% of cases, giving a correlation (r) or 0.60 between the real defect and the radiological estimation. While massive defects were recognized in most cases, moderate defects were correctly estimated in about 50%. Moderate defects included migration of the cup, which was overlooked in between 46% and 69% of cases. Similar results were achieved in the judgement of bone loss. Only in 25% was direct classification according to Paprosky successful; it was better in small defects and worse in massive defects, with 16%. The interobserver correlation was only 0.54. In general, in most cases the defects were underestimated. This study raises the question of whether classification systems can provide the information needed for clinical useful therapeutic algorithms. The fact that the real bone loss is generally underestimated must receive due considerations when operations are being planned.