抄録
Objective: Curved periacetabular osteotomy (CPO) has been widely used to treat acetabular dysplasia. Computed tomography osteoabsorptiometry (CTOAM) is a useful method of predicting the long-standing stress distribution by measuring the pattern of subchondral bone density. The method is based on the theory that the distribution of subchondral bone density is directly related to the distribution of mechanical stress action on the joint. The purpose of this study was to evaluate the change in the stress distribution of the acetabular roof in a dysplastic hip before and after CPO.
Methods: We have been using CPO for patients with arthritis secondary to acetabular dysplasia since 2004. Seven hips that had undergone CT preoperatively and 24 or more months postoperatively were analyzed. The average patient age was 30.1 years (range, 17-54 years) and the average center-edge angle (CEA) was 4.8° (range, -5.6° to 17.4°) preoperatively and 33.9 (range, 15.7°-45.7°) postoperatively. CT values of the acetabular roof were uploaded to a computer and analyzed by software specifically designed for this study. The values were measured at each coordinate point and mapping data were depicted using a grayscale. For qualitative analysis, we transferred the grayscale mapping image to a color-scale map and compared mineralization patterns. The area ratio of the high-density area was analyzed.
Results: The stress concentration patterns seen before surgery were classified into two types: anterolateral, which was seen in four hips, and central, which was seen in the remaining three hips. When a comparison was made between CT scans at 1 year after surgery and scans at more than 2 years after surgery, the high-density area in four hips decreased, while three hips showed an increased high-density area. Three of the four hips with decreased bone density had a preoperative CEA of more than 10, and the other hip, that of a 55-year-old woman, had a preoperative CEA of -5.6°. All three hips with increased bone density had CEAs in the range from -5° to 3°.
Conclusion: A relationship between preoperative CEA and postoperative changes in stress concentration was found. Our results showed that CPO changed the stress concentration of the acetabulum, and the change may vary with the extent of preoperative dysplasia.
