Emil Letournel revolutionized the surgical treatment of acetabular fractures with his development of the anterior ilioinguinal approach in 1965.1,2 This approach was the mainstay for the treatment of anterior-based fracture patterns of the acetabulum for decades. In 1994, Cole and Bolhofner described a modified version of an intrapelvic approach used by general surgeons.3–5 The anterior intrapelvic approach (AIP) provides exposure to the internal aspect of the pelvis with a different vantage point than the traditional ilioinguinal approach. A variety of modifications have further expanded the visualization and utility of this approach.6–8 Combined with a lateral window, the AIP affords direct access to, and visualization of, the entire anterior column of the acetabulum, as well as the quadrilateral surface and some elements of the posterior column. The modern AIP has supplanted the traditional ilioinguinal approach in many centers, whereas in many others, it is a useful adjunct to the traditional exposure. We believe that if an anterior approach is indicated, the AIP affords similar exposure, clamp options, and screw trajectories to a traditional ilioinguinal approach. However, certain fracture patterns deserve a second thought when considering use of either the AIP or ilioinguinal approach. These challenges relate to certain posterior column fracture characteristics or the ability to obtain a reduction of the posterior component of a transverse pattern from an anterior approach. The goal of this article is to define these problem fracture patterns and provide guidance to the surgeon regarding which fracture patterns warrant consideration of different or additional approaches. These different approaches include either a more extensile approach or the addition of a second posterior approach.
Posterior Column Fracture Patterns With the Anterior Intrapelvic Approach
Techniques for the reduction of posterior column fractures through the AIP approach are well described.9–11 A wide variety of posterior column fracture patterns may be addressed from the anterior exposures. One of the perceived benefits of the intrapelvic approach is the vantage point, which allows for visualization of the quadrilateral surface en face and to affect a direct medial to lateral reduction vector with implants or reduction instruments. The key to a successful surgical result rests with the surgeon understanding the fracture orientation, obliquity, and displacement of the posterior column. Often times, the displacement consists of a combination of medialization, sagittal plane extension, and external rotation. The AIP approach affords the surgeon the ability to provide a lateralizing force to resist medial displacement. An extension deformity of the posterior column or inferior displacement may be addressed with reduction forceps placed on the posterior column with the opposing tine above the pelvic brim. A variety of clamps may facilitate this reduction and are well described.10 A stable anterior column will effectively create an axilla to aid in a stable reduction of the posterior column and allow the surgeon to verify correction of the rotational component.
However, as our experience with the AIP approach has increased, we have identified several distinct patterns that involve the posterior column that are often difficult to reduce and instrument through an isolated anterior approach. These patterns are as follows:
- High cranial extension of the posterior column fracture line
- Segmental comminution of the posterior column
- Unfavorable obliquity of posterior column fracture
- Internal comminution at sciatic buttress
High Cranial Extension of Posterior Column Fracture Line
A common posterior column fracture morphology includes a high exit point in the upper sciatic notch, frequently with a long, oblique fracture line (Fig. 1). Fractures with wide displacement in the mid to upper notch area often allow the superior gluteal neurovascular bundle to displace into the fracture site. Similarly, the sciatic nerve may displace into the fracture site in certain situations. Visualization of these neurovascular structures is more limited from the internal aspect of the pelvis. The apex of the displaced fracture is also more difficult to directly visualize. This can lead to a problematic situation where the surgeon is unaware of incarcerated structures within the fracture site while attempting reduction. This may result in neurologic injury or vascular disruption. If the potential for this is unrecognized or unanticipated preoperatively, the surgeon's first indication of a problem may be inability to obtain an adequate posterior column reduction due to the presence of these incarcerated structures. Worse, the first sign may be sudden arterial bleeding upon attainment of the posterior column reduction or neurologic injury that may be of unclear etiology. Fractures exiting at the most proximal portion of the notch seem to be less problematic. The contour of the notch remains on the posterior column fragment and effectively captures the NV structures preventing them from dropping into the fracture site.
The experience with this pattern comes largely from addressing this fracture from the external aspect of the pelvis through a Kocher–Langenbeck approach. This exposure allows for clear visualization of the sciatic nerve, superior gluteal bundle, and the apex of the fracture. The surgeon is able to distract the fracture, remove interposed debris, clear incarcerated neurovascular structures, and reduce the fracture apex under direct visualization. This level of visualization and control of critical structures is not as readily available from anterior internal approaches. For these reasons, the authors give strong consideration to a posterior approach when there is a displaced high cranial extension of the posterior column fracture, and high likelihood of neurovascular incarceration is present.
Segmental Comminution of the Posterior Column
The surgeon must recognize the challenge of obtaining an anatomical reduction of the posterior column when this portion of the fracture is comminuted (Fig. 2). As stated, the displacements often include some level of extension, medialization, and rotation. Although large areas of the posterior column can be visualized from the internal aspect of the pelvis, the surgeon is limited to the reduction maneuvers possible. Rotation of the posterior column is arguably the most difficult to control. Much of the ability to reduce a displaced posterior column component from the front relies on creating a stable cranial axilla to which the entire posterior column can be drawn. If the posterior column is multifragmentary, comminuted, or segmental, the ability of the surgeon to achieve anatomical reduction is limited. The fragments may be visualized, but controlling and stabilizing them can be extremely difficult. Conversely, exposure, reduction, and fixation of the entire posterior column from a Kocher–Langenbeck approach are often technically easier. This may entail the use of mini fragment fixation to sequentially restore anatomical reduction of the posterior column. It is our opinion that failure to recognize segmental comminution or significant comminution of the posterior column will result in higher likelihood of malreduction from an anterior exposure alone and therefore often mandates a supplemental posterior exposure.
Unfavorable Obliquity of Posterior Column Fracture
As stated previously, one of the main advantages of the intrapelvic approach is the ability of the surgeon to direct a medial to lateral force and apply implants in this trajectory (Figs. 3A–C). Similar to the aforementioned description of the comminution of the posterior column, the obliquity of the fracture plane may affect the surgeon's ability to reduce and stabilize the posterior column. The preferred obliquity of posterior column fracture lines addressed from the AIP consists of a cranial internal component and a more caudal lateral component. This allows a large surface area to be reduced with a medial to lateral force vector. In addition, fixation is easily placed from this approach to support this reduction. As the fracture plane becomes more horizontal in the medial lateral plane or is in the reverse plane (caudal medial to cranial lateral), the difficulty in obtaining a stable anatomical reduction increases. The surgeon loses one of the strengths of the approach, namely the medial to lateral vector of reduction. With a more horizontal fracture plane or reverse oriented plane, the medial to lateral vector may displace the ischial segment laterally. It is prudent to scrutinize preoperative imaging to fully assess the level and obliquity of the posterior column fracture line if a reduction from an anterior approach is being considered. Three-dimensional CT image reconstruction may be particularly helpful in making this determination.
Internal Comminution at Sciatic Buttress
The ability to achieve anatomical reduction of the posterior column component from an anterior approach relies on anatomical bony keys to affect and judge the reduction (Fig. 4). We have described the difficulties associated with obtaining and judging a reduction when segmental comminution is present in the posterior column. The surgeon will have similar difficulty in the setting of comminution involving the internal aspect of the sciatic buttress. It is not uncommon for there to be some level of cortical comminution in the region of the sciatic buttress particularly in associated both column patterns. One of the keys to reduction from an anterior approach is to maintain these fragments to judge the reduction of the anterior column. The comminution in this area may extend to the true pelvis in the region of the sciatic buttress. Larger isolated fragments may be replaced to serve as keystones to the reduction. As the level of comminution increases, it may become difficult or even impossible to achieve anatomical reduction of these fragments. Failure to achieve anatomical reduction in this area increases the likelihood of malreduction of the posterior column. Interestingly, in the situations where the internal pelvic comminution is present, the external surface is often simpler in nature and may therefore warrant consideration of an extensile or posterior approach.
Common Malreductions of the Posterior Column From an Anterior Approach
The specific posterior column components that lead to difficulty were described in previous sections, but a malreduction can still occur even if the posterior column portion is amenable to reduction from the anterior approach (Fig. 5). A common problem fracture that many fail to recognize is the transverse family of fractures. This consists of the transverse fracture pattern and the T-type. There are a variety of factors that may drive the choice of surgical approach for these injury patterns. If an anterior approach is selected, it is critical that the surgeon have an understanding of the common malreductions that may occur and how to avoid them.
The underlying problem is addressing all the displacements of the ischiopubic segment from an anterior exposure. As stated previously, the reduction maneuvers of the posterior column are somewhat more limited from the anterior as compared to the posterior approach.
In addition to addressing the extension, medialization, and rotatory component, the surgeon must understand how reduction aids applied to the internal aspect of the pelvis may affect reduction at the joint level. The most common malreduction is an adduction displacement of the ischial segment. This occurs due to the vector of clamp placement on the internal aspect of the pelvis compressing and adducting the fragment. From the intrapelvic view, the reduction looks fine. The surgeon cannot see the gapping of the external aspect of the posterior column. One must be critical of intraoperative fluoroscopy and plain films to avoid this malreduction. Provisional fixation may be placed to resist the adduction or fixation placed in such a way as to neutralize the displacement. A similar problem may occur when compressing the anterior portion of a transverse fracture. The resultant problem is distraction of the posterior column. This is analogous to the anterior gapping one can see when addressing a transverse fracture from a posterior approach. In both situations, the distracting force must be neutralized either with plate contour or opposite column stabilization before compression. This potentially becomes less of an issue when using dual approaches because the initial anterior fixation should function to create a hinge, followed by a staged posterior approach, to affect the definitive reduction with the advantage of now working against this previously created hinge (Fig. 5C).
There is continued debate among acetabular fracture surgeons as to whether the AIP or the ilioinguinal approach gives better exposure or improved ability for instrumentation. Despite strong feelings, there are many studies showing equivalence in clinical outcomes.11–14 The decision has much to do with surgeons' training and level of comfort and familiarity with the respective surgical approaches.
A variety of modifications to the AIP approach have been well described.6–8,11,15 These include proximal split of the rectus, distal rectus release from the pubic body, and lateral dissection to the pectineal eminence and anterior rim. Furthermore, the addition of an anterior superior iliac crest osteotomy or release of the lateral aspect of the inguinal ligament greatly improves the extent of visualization from the lateral window. It also greatly improves access for plate placement and screw trajectory. The added exposure to the interspinous region affords the ability to place clamps on the external aspect of the ilium.6 The AIP can also be added to the classic ilioinguinal approach making the medial window more of a working portal to allow for greater access to the pelvic brim and quadrilateral surface.8 There is definitely room for both approaches, and using them ad libitum allows the surgeon to tailor the surgical approach to the specific fracture pattern. Certainly, the original impetus to avoid the middle window and the potential complications that come with manipulating the contents of the lacuna vasorum still exist.
We have put forward a number of different fracture patterns that are difficult to manage through an isolated anterior approach and should give a surgeon reason to consider a different isolated or more extensile approach or combined approaches. There are most certainly other rare fracture patterns that belong on this list; however, the examples described here include the clinical entities most commonly encountered in our experience. As surgeons become more facile with addressing complex fracture patterns through anterior approaches to the acetabulum, this will bring new challenges and new techniques. Thoughtful implementation and ongoing evaluation of the clinical outcomes of these techniques are necessary.
The authors acknowledge 3D4 Medical (Essential Anatomy 5) for the use of images that were modified for the figures in this paper.
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