Spatial changes of the peri-acetabular pelvic in developmental dysplasia of the hip---a combined 3-dimentional computed tomography (3D-CT) study in patients and experimental study in rats.

Few previous studies noticed the three bony structures that formed the acetabulum in developmental dysplasia of the hip (DDH). This study aimed at investigating the spatial changes of the peri-acetabular pelvis in developmental dysplasia of the hip through radiological evaluation of the patients and experimental observations in rat models. 115 unilateral DDH patients were studied through 3D-CT. In reconstruction workstation, the iliopubic inner plate angle, ilioischial inner plate angle and ischialpubic inner plate angle were measured and compared. 58 neonatal Wistar rats were divided into two groups and the rats in experiment group were swaddled to establish DDH models. The hips were sectioned, stained. The same three angles were measured and compared. The ilioischial inner plate angle of the affected hip decreased while the ischialpubic inner plate angle increased compared to those of the contralateral side. The iliopubic inner plate angle showed no difference between the affected and unaffected hips. In animal models we observed the same pathological pattern. The three angles measured on the sections showed similar tendency as those in the patients with DDH. The ischium rotates up and forwardly around the posterior and vertical limbs of the triradiate cartilage complex in DDH, just as a lifted piece of Pizza.