The anterior intrapelvic (AIP) approach (also known as the modified Stoppa approach) was pioneered by Cole and Bolhofner as an alternative technique for ORIF of the anterior acetabulum. The AIP allows less invasive access to the acetabulum from within the pelvis; thus, the goal of this article is to outline the indications for the AIP approach and to stimulate discussion regarding potentially more controversial concepts in light of the increasing popularity of this approach.
The traditional ilioinguinal approach creates three working windows to access the acetabulum with the surgeon standing on the side of fracture and working “down and into” the pelvis. In contrast, the AIP approach employs a vertical split in the rectus linea alba entering into the retropubic space similar to the approach for symphyseal fixation. With the surgeon standing on the opposite side of the fracture, dissection is performed along the retro-ramus and quadrilateral surfaces essentially working “up and under” the rectus muscles and neurovascular structures. This technique provides less direct surgical exposure of the femoral vascular structures while maintaining excellent visualization of the acetabulum, particularly the posterior column, sciatic notch and quadrilateral surface.
Thus, the question: “When is the AIP preferred instead of the traditional or modified ilioinguinal approach?” The reality is that neither surgical approach is better or more useful, but rather both are tools to accomplish the same goal – anatomic reduction of the acetabulum fracture. Certainly, based on training and experience, most surgeons will have a preferred approach for anterior acetabulum fractures. However, a thorough understanding and appreciation for both techniques will better enable the surgeon achieve the goal of anatomic reduction. The full ilioinguinal approach provides tremendous access to the innominate bone, and for less experienced surgeons or very difficult fractures, this may be preferred. In contrast, the AIP may serve as a less invasive alternative working mainly through the intra-pelvic window, yet many more complex fractures such as the associated both column and high anterior column fractures may be challenging to reduce via the limited window of the AIP.
As experience grows with the AIP, more and more can be achieved through this single window. Keys to enhancing the exposure include fully releasing the rectus insertion from the superior aspect of the pubis including release down onto the anterior surface of the pubis. This allows the rectus to “fold” over and away, dramatically improving the exposure. Additionally, flexion of the hip and elevation of the iliopsoas as far proximally as the sacroiliac joint greatly enhances both visualization as well as reduction capabilities. Finally, meticulous dissection and mobilization of the obturator nerve is essential for not only access, but also for protecting the nerve from traction palsy. The nerve should be freed proximally, almost to its origin and then distally, into the obturator foramen. This mobility then allows the nerve to remain loose within the operative field under direct vision rather than retracting it out of the field; thus, further protecting the nerve.
This brings us to the subject of alternative tactics for reduction and fixation. As comfort with the exposure is gained, so does comfort with reduction of more complex fractures. Traditionally, the posterior column is reduced via a lateral window with either the AIP or a standard ilioinguinal approach. However, reduction of the posterior column may be achieved by placing an angled jaw pelvic clamps into the greater or lesser sciatic notch or along the quadrilateral surface with the second tine along the pelvic brim or anterior column. An alternative technique employs a screw reduction clamp such as a Farabouf or Jungbluth applied with screws in the pelvic brim and in the sciatic buttress creating the reduction vector directly for the posterior column.
This leads to the question as to whether the posterior column can be stabilized via the AIP without the traditional anterior to posterior lag screws that are frequently placed from a lateral window. A plate placed along the sciatic buttress can stabilize the reduced posterior column; however, is a lag screw needed to maintain the reduction? Finally, one must ask if the reduction can be achieved via the AIP window alone, is stabilization of the iliac components of an associated both column fracture absolutely necessary? In the classical approach, the iliac components are reduced and stabilized in order to ensure the reduction of the joint surface is anatomic. Yet, if the fracture is reduced and stabilized at or near the joint itself, are the additional plates and screws for the iliac components needed?
At present, little data exists to answer many of these questions. However, as more widespread experience is gained, and continued development of the dissection, instruments, reduction tools and implants occurs, these and many more questions will be asked and hopefully answered.
Michael T. Archdeacon, M.D., M.S.E.
Peter J. Stern Professor & Chairman
Department of Orthopaedic Surgery
University of Cincinnati Academic Health Center