Anatomy and Biomechanics of the Pelvis in Exstrophy

Abstract

The Exstrophy Complex includes anomalies ranging from epispadias to classic to cloacal exstrophy. Exstrophy of the bladder occurs due to abnormal anterior rupture of the cloacal membrane early in the embryonic period. Mesenchymal ingrowth into the abdominal wall is inhibited. Since the pelvis is derived from sclerotomal components of the mesenchyme, one may hypothesize that the development of the entire pelvis may be affected by this altered migration of mesenchyme. It is important to understand the patho-anatomy of the pelvis in exstrophy, for planning of appropriate soft-tissue and bony correction in this disorder. However, there are very few specimen dissections reported, and no comprehensive analysis of pelvic shape in either classic or cloacal exstrophy. Therefore, analysis of computed tomograms of patients with classic and cloacal exstrophy was carried out to better define the differences in the shape of the pelvis between these patients and those without congenital anomaly. We attempted to answer the question of where the pelvis in exstrophy was rotated, to quantify the malrotation, and to determine whether there was an actual deficiency of growth. An analysis of the rotation and the spacing of the hips was also made. In addition, we wished to correlate these findings with the clinical picture of patients’ gait, which is commonly described as “out-toeing” or “waddling.”