Abstract
Pelvic tilt is a characteristic feature of the individual patients’ posture. Large differences in pelvic tilt are well known among individuals, over time or related to activity. To our knowledge, it is unknown how patients with developmental dysplasia of the hip (DDH) behave in terms of pelvic tilt. One can assume that patients with a dysplastic acetabulum might compensate for their acetabular under coverage by functionally increasing pelvic tilt. Theoretically, this effect should be reversible when an acetabular redirection osteotomy is performed. We therefore hypothesized that pelvic tilt decreases after periacetabular osteotomy.
Sixty-three consecutive patients (67 hips) with documented PAO at our institution were analyzed. 39 patients (40 hips) were excluded because of indications than other DDH (e.g. acetabular retroversion), incomplete radiographic documentation or insufficient follow-up leaving us 24 patients (27 hips) for evaluation. Preoperative, intraoperative (under general anesthesia), and at least 1 year postoperative anteroposterior radiographs were analysed. All x-rays were done in a standardized manner. Two distances were measured: the vertical/horizontal distance between the mid point of the sacrococcygeal joint and the symphysis. The change of these distances allows exact determination of the pelvic tilt.
A significant decrease for pelvic tilt was found between the preoperative x-ray and the one after at least one year. Pelvic tilt did not change significantly between the pre- and the intraoperative x-ray, and between the intra- and follow-up x-ray.
Our findings support the hypothesis that patients with DDH try to compensate for their insufficient acetabular coverage by increasing the tilt of their pelvis. After PAO, i.e. after iatrogenically increasing acetabular coverage, the patients’ pelvis significantly turns back in to less lordosis.
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