Bilateral Anterior Innominate Osteotomy for Bladder Exstrophy
Authors: Nhan Derek T. , Sponseller Paul D. 
Published: January 2019

Background:
Bladder exstrophy is a congenital condition that affects the genitourinary and musculoskeletal systems, and less commonly affects the intestinal system, with cloacal exstrophy. This condition results from abnormal migration of the mesenchyme, between the endoderm and ectoderm, leading to anterior rupture of the cloacal membrane. Numerous osseous morphologic changes are observed in bladder exstrophy. Rotational anomalies include external rotation of the posterior part of the pelvis and iliac wings, on average 12°, and acetabular retroversion
1–3
. Although various osteotomy types have been described for initial bladder exstrophy closure, the anterior approach has demonstrated positive outcomes in improving daytime continence, gait, and correction of the diastasis
4
. Thus, the anterior iliac osteotomy provides an effective method to help close the pelvic ring and decrease stress on the anterior abdominal wall during exstrophy closure. In addition, this technique promotes continence by reconfiguring, and thereby restoring, the fibrous symphyseal bar and pelvic floor musculature
5
.

Description:
The steps of the procedure include (1) preoperative planning, (2) patient positioning, (3) incision, (4) identification of the lateral femoral cutaneous nerve, (5) subperiosteal dissection of the iliac wing, (6) guide pin placement and anterior osteotomy, (7) posterior hinge osteotomy (for cloacal exstrophy and for patients ≥2 years old), (8) external fixator pin placement, (9) anterior internal fixation of the pubic symphysis (for cloacal exstrophy and for patients ≥2 years old), and (10) resumption of the urologic procedure followed by wound closure and application of external fixator.

Alternatives:
Numerous previous techniques for osteotomies in bladder exstrophy have been developed, starting with Shultz in 1958, who recognized the importance of bringing the pubic bones together for gait correction in exstrophy repair
6
. O’Phelan was the first, to our knowledge, to document outcomes of this bilateral posterior osteotomy technique to reduce tension from the externally rotated iliac bones and widened pubic symphysis in a 2-stage bladder exstrophy closure
7
. Other approaches have included an oblique iliac wing osteotomy and pubic ramotomy, described by Frey and Cohen in 1989
8
. However, the latter approach inadequately restores the pelvic osseous relations except in female newborns who would have a small diastasis after manual rotation of the pelvis.

Rationale:
This procedure has several advantages over the prior conventional posterior approach. These include better approximation and improved mobility of the pubic rami at the time of closure, prevention of vertical migration of the hemipelvis, direct visual placement of an external fixator and adjustment postoperatively, and no requirement for turning the patient during the operation. In addition, this procedure allows for adjunctive posterior osteotomy from the anterior approach to provide adequate closure in those with cloacal exstrophy, prior failed closure, or extreme diastasis of >6 cm
9
.