Posterior Wall

The most common fracture pattern occurs in the posterior wall area. These injuries tend to occur when the flexed hip loads the posterior wall and a portion of the posterior wall is displaced away from its intact base. These injuries are often seen after automobile accidents when the seated motorist rapidly decelerates and the flexed knee contacts the dashboard, causing the flexed hip to load the posterior acetabular wall to failure. Because of this mechanism, knee-related injuries such as patellar fractures, traumatic arthrotomy, and posterior cruciate ligament injuries are associated with posterior wall acetabular fractures. In drivers contacting the steering mechanism with or without airbag protection, thoracic aortic injuries were previously identified and therefore must be ruled out.

Similar to all acetabular fractures, posterior wall patterns have a variety of appearances, depending on the limb’s position at load, the local bone quality, and the normal anatomy of the acetabulum. Most surgeons would like to believe that “a posterior wall is a posterior wall, and they are simple,” but nothing is further from the truth. Posterior wall acetabular injuries range from superior dome area wall displacements, to more common posterior wall displacements, to more caudal wall displacements, to “barn door” comminuted wall injuries, among other configurations and locations. In some patients, the posterior wall fragment fracture yields incompletely, and the femoral head crushes several chondrocancellous articular fragments into the intact posterior column cancellous bone, thereby producing an “intraarticular” posterior wall variant fracture-dislocation. Experienced clinicians recognize the variety of posterior wall injuries caused by impact loading as well as those seen with the more complex associated acetabular fracture patterns in which the posterior wall fracture fragment is caused by capsular avulsion ( Fig. 41-11 ). Posterior wall fractures can be comminuted or associated with osteochondral impaction injuries along the fracture margin of the stable posterior column fragment, or they can involve both. Marginal impaction is not the only local chondro-osseous problem related to these fractures. Displaced posterior wall fractures imply that the patient experienced an associated dislocation. For this reason, the femoral head should be evaluated for resultant impaction or cleavage injuries and the hip joint inspected for related bone or chondral debris. Common sites for debris include the fossa acetabuli, between the femoral head and acetabular dome, in the cranial and caudal capsular recesses, and between the anterior femoral head and capsule. Debris can be fragments of cartilage, cancellous bone, cortical bone, or any combination of the three. Capsular and labral tissues may also be mislocated within the hip joint and cause joint incongruity. During surgery, these same tissues can obstruct accurate reduction of the bone fragments.

A variety of posterior wall acetabular injuries are represented by these images. There are commonly three different types of posterior wall acetabular fractures. The most common are elementary patterns associated with posterior hip fracture-dislocations. In these situations, the posterior wall fragment is “pushed off” by the femoral head as it dislocates. The next most common type occurs as a component of an associated both-column fracture pattern. In these situations, the posterior wall fragment is avulsed or “pulled off” as the femoral head displaces medially. The least common type occurs when the femoral head intrudes into the ischium, causing an impaction injury of the posterior wall area. The cortical posterior wall remains largely intact while the articular fragments are “pushed into” the underlying cancellous bone of the ischium.

A, The elementary pattern common posterior wall is seen in this three-dimensional (3-D) model. The posterior wall primary fracture fragment is large and displaced. A small, comminuted fragment is noted caudally. During surgery, the hip capsule and labrum were both intact. For most displaced posterior wall fractures, the caudal labrum and adjacent hip capsule are torn, but the cranial labrum usually remains intact.

B1 and B2, This patient has a comminuted posterior wall acetabular fracture that extends into the greater sciatic notch. B3, On the axial computed tomography (CT) image, a large posterior wall articular fragment is located anteriorly relative to the femoral head.

C1, This patient was crushed by a large metallic object, but states that his hip did not dislocate. C2 , The 3-D model identifies a very small and caudally located posterior wall fracture. The axial image reveals that the posterior wall articular surface has been crushed into the cancellous bone of the ischium.

D1 and D2, This patient has a comminuted and displaced posterior wall acetabular fracture, but the wall fragments are frail. D3 and D4, The CT axial images identify two large regions of chondrocancellous “marginal” impaction.

E1 to E4, This patient has an associated both-column acetabular fracture pattern but with a large posterior wall fracture fragment as a part of it. The posterior wall fracture fragment has approximately one-third of the dome articular surface on it. In associated both-column acetabular fracture patterns, the posterior wall fragment is commonly large, not comminuted, and avulsed by the medial displacement of the overall fracture. When directly visualized via a posterior exposure at surgery, the capsule and labrum are usually completely intact posteriorly.

Routine posterior wall fractures are best identified on the OO image, especially when displaced. Usually, the displaced wall fragment yields in tension caudally along with tearing of the local capsule and labral tissues while the superoanterior labrum and capsule remain intact. The superior cortical aspect of the fracture is often comminuted because it yields in compression as the wall displaces. The displaced posterior wall fracture fragment damages the superior gemellus muscle and the portion of the gluteus minimus muscle caudal to the SGNVB as well. With more extensively displaced and dramatic injuries, the piriformis muscle belly can be injured and even transected by the displaced wall fragment’s sharp cortical edge. In some instances, inspection of the buttock skin will reveal a circular ecchymotic area representative of the femoral head contusion ( Fig. 41-12 ). Not surprisingly, the sciatic nerve may be damaged by direct injury from the displaced wall fragment, the extruded femoral head at the time of dislocation, or other direct or indirect factors. The piriformis anatomy is variable, and its relationship with the sciatic nerve bundles may also be responsible for nerve injury ( Fig. 41-13 ). The sciatic nerve can also escape injury by the fracture-dislocation only to be injured by the reduction maneuver. In these unusual instances, the displaced wall fracture fragment follows the hip reduction, and the sciatic nerve becomes compressed between the posterior wall fragment and its base.

The circular bruise noted on this patient’s left buttock was caused by the femoral head displacement at the time of fracture-dislocation. During the operation, a circular pathway was noted from the hip joint through the buttock muscles to the dermis.

A, The obturator oblique plain pelvic image demonstrates a displaced posterior wall fracture-dislocation. This radiograph was obtained after a screening anterior-posterior radiograph had diagnosed the fracture-dislocation but before orthopaedic consultation. Manipulative reduction of the fracture-dislocation is recommended after diagnosis and before complete radiographic evaluation. B, The corresponding acetabular computed tomography image reveals marginal impaction of chondrocancellous fragments into the intact posterior column area. As the femoral head dislocates, these chondrocancellous impaction fractures occur along the fracture edge. Less frequently, the articular surface of the displaced posterior wall may have impaction or comminution. C, This patient has a left-sided displaced posterior wall acetabular fracture with a common displacement pattern.

Posterior Column

Posterior column fractures occur infrequently but are relatively predictable in their appearance. As an elementary pattern, the fracture plane is singular, descending from the greater sciatic notch, with the lateral cortical disruption splitting the posterior column and posterior wall anatomic areas while the medial cortical line divides the quadrilateral surface. The fracture plane progresses through the dome area, exits the caudal posterior wall and fossa acetabuli, and terminates through the ischium–inferior ramus junction. It is not unusual for dome chondrocancellous pyramidal-shaped fragments to be displaced and associated with this pattern. Similarly, portions of the torn posterior labrum may be mislocated between the femoral head and weight-bearing dome with this fracture pattern. The displaced posterior column fracture fragment may injure the SGNVB, especially when the fracture line is located high in the greater sciatic notch. This is important to remember both before and during surgery because arterial injury may cause ongoing bleeding and require embolization. Buttock compartmental syndrome is rare but can also occur because of superior gluteal system bleeding. During surgery, the SGNVB should be visually identified to ensure that it is not displaced between the fracture fragments. If it is displaced, it should be either carefully retracted as the fracture is reduced and clamped, or the cortical spike of the greater sciatic notch should be removed to prevent crushing the neurovascular bundle. Commonly, displaced posterior column fractures obstruct venous flow of the superior gluteal vein, causing its tributaries locally to engorge and dilate throughout the gluteal muscle bellies. These enlarged veins are fragile and often require ligation individually to control bleeding if they tear. It is important to spare the superior gluteal nerve during these ligations. The surgeon must resist the urge to simply apply a large vascular clip that could inadvertently damage the artery, vein, and nerve. Retraction of the proximal vascular bundle into the true pelvis caused by either a traumatic or iatrogenic injury usually obviates ligation, so packing is then recommended to attempt to control such bleeding. Venous bleeding and often arterial bleeding respond to packing. The packing material should be applied so that the superior gluteal and sciatic nerves are not inadvertently injured by overly aggressive packing. If the packing fails to control superior gluteal arterial bleeding, then prompt wound closure is performed, and urgent angiographic evaluation and embolization if possible are advised.

Similar to the superior gluteal neurovascular structures, the sciatic nerve can also be injured by displaced posterior column acetabular fractures. These are usually traction or contusion injuries noted at patient presentation. Some may be related to direct contusion or stretch, and some may be related to piriformis muscle anatomic abnormalities that divide and tether the nerve, making it vulnerable with fracture fragment displacement. Sciatic nerve injury can also result from the closed reduction. This occurs because the sciatic nerve course parallels certain displaced posterior column fracture planes and can become trapped within the fracture line as the displaced fracture-dislocation is reduced. This happens rarely but must be remembered and not missed or justified as an injury-related occurrence. For this reason, the pre- and postreduction nerve assessments are carefully detailed and documented. If the sciatic nerve examination findings change after closed reduction of any acetabular fracture, then urgent exploration, neuroplasty, and fracture fixation are recommended.

Posterior column acetabular fractures are best seen on the iliac oblique and AP plain pelvic radiographs. The pelvic CT scan reveals detailed displacement information; identifies comminution, dome fragmentation, and loose bodies within the joint; and shows impaction injuries that may occur along the fracture line.

Anterior Wall

Anterior wall acetabular fractures are the least common of all types. The unnatural lower limb and body positionings needed to load the anterior wall coupled with the tiny surface area of the anterior wall make this pattern the most unlikely. Simply because of their anatomy, these fractures are quite small and associated with anterior dislocations. The iliac vasculature, femoral nerve, and lateral femoral cutaneous nerve (LFCN) can be injured in association with anterior wall fracture-dislocations. In Letournel’s original description, focal fractures of the anterior column involving the pelvic brim were included as anterior wall fractures. This continues to confuse surgeons. To remain consistent with the classification scheme, if the anterior acetabular fracture lines do not violate the iliopectineal line, then it is an anterior wall fracture pattern. If the anterior fracture disrupts the iliopectineal line and therefore involves the pelvic brim, then it is an anterior column fracture pattern.

The anatomic area of the anterior wall is often involved in pelvic ring fractures when the fracture lines of the peripheral superior pubic ramus extend into the anterior wall area. This pelvic ring injury, however, should not be misclassified as an anterior acetabular wall fracture.

Anterior wall acetabular fractures may involve a small portion of the iliopectineal line on the AP radiograph. Whereas the OO image may show subluxation of the femoral head, the iliac oblique demonstrates the anterior wall fragment displacement.

Anterior Column

Anterior column acetabular fractures disrupt the iliopectineal line on the AP radiograph and have a variety of appearances depending on their peripheral exit points and displacement extents. As an elementary pattern, the fracture plane is singular but may also have three distinct surface orientations. These fractures were subclassified according to their iliac exit site. “High” anterior column fractures include those in which the iliac crest is the peripheral exit point. “Intermediate” patterns have their exit points in the region of the anterior superior iliac crest, and “low” patterns exit adjacent to the AIIS. “Very low” patterns only involve the region medial to the IPE. The fracture displacement depends on the subclassification type. The high types have the tensor, abdominal obliques, gluteus medius, and sartorius muscle forces to cause displacement. Because of this displacement, the LFCN may be injured in association with this particular fracture type. On its other end, the fracture exits through the superior ramus. Displacement at the ramus region can injure or deform the iliac vessels and femoral nerve, as well as the obturator neurovascular bundle. It is not difficult to understand why femoral deep venous thrombosis (DVT) occurs for these fractures. The other patterns have variable deformities depending on the fracture specifics and related deforming forces. Displaced intermediate and low types risk associated femoral and obturator neurovascular injuries. In some patients, the anterior column fracture’s exit at the iliac crest is incomplete and demonstrates plastic deformation. The incomplete fracture at the iliac exit site allows deformity but usually lends some degree of fracture stability. This incomplete fracture may need to be osteotomized at surgery to reduce the fracture accurately.

The iliac oblique image usually best demonstrates displaced anterior column acetabular fractures. These fractures are often missed on the screening AP radiograph because the fracture line along the pelvic brim’s displacement is perpendicular to the radiographic beam, so the iliopectineal line’s density appears nearly symmetrical. The iliac oblique radiograph reveals the peripheral exit points well, especially for the high patterns. The radiolucent fracture gap along the pelvic brim is also apparent. The femoral head typically remains congruent with the displaced anterior column fracture fragment, which usually indicates a disrupted ligamentum teres ( Fig. 41-14 ). High anterior column acetabular fractures usually have three different fracture surface orientations: the portion that splits the anterior wall area, the portion paralleling the pelvic brim, and the iliac crest exit site. These three planar surfaces allow for strategic reduction clamp and implant applications.

These images demonstrate a very high anterior column acetabular fracture pattern. The iliac exit point is posteriorly located. A and B, It is easy to see on the anterior-posterior pelvic image and three-dimensional (3-D) model how the fracture can be confusing because the iliopectineal line appears mostly intact. The fracture involves the anterior portion of the pelvic brim area, but the posterior portion remains intact and gives the appearance of an intact iliopectineal line in that area. However, the density is asymmetrical, indicating the fracture displacement. The different fracture surface angles are notable on these images. C and D, The iliac oblique image and 3-D model best demonstrate the iliac exit site, iliac involvement, and anterior wall area exit site. In this patient, the femoral head is displaced and remains congruent with the displaced anterior column fracture fragment. E, The posterior oblique 3-D model shows the lateral surface fracture line. F, The axial image at the dome level identifies the complex fracture orientation there.

Transverse

Transverse acetabular fractures often confuse clinicians because of their inclusion in the elementary fracture group despite involving the two supporting columns and two wall areas. Transverse fracture patterns occur in a variety of orientations and obliquities but remain a singular yet often complex fracture surface. Because of their singular fracture plane “purity,” transverse fractures were included in the elementary group.

A common transverse fracture pattern begins at the anterior wall anatomic area, extends through the iliopsoas gutter and anterior wall articular surface, progresses across the pelvic brim and anterior column, through the quadrilateral surface dividing the upper and lower halves of the fossa acetabuli, and exits the posterior column and posterior wall’s edge. The labrum is also usually injured at both the anterior and posterior exit sites, especially in displaced transverse patterns. The torn labrum or portions of it can intrude into the joint, causing further incongruity between the femoral head and intact dome region.

Transverse fractures are the only elementary pattern to extend through the two wall areas and the two acetabular supporting column zones. The terminology can be confusing because the fracture involves “both of the acetabular columns” but is not an “associated both-column” fracture pattern. As previously stated, fracture patterns and anatomic areas share terminology but should not be confused with each other nor the terms used synonymously.

Just like the other elementary patterns, the transverse pattern splits the acetabulum into two fragments. Whereas the upper or cephalad fragment is almost always the stable portion of the fracture, the caudal segment is usually the mobile and displaced fragment. The caudal fragment mobility is due to the fracture plane and the fact that the symphysis pubis ligaments function as a hinge for it ( Fig. 41-15 ).

In transverse acetabular fracture patterns, the ilioischial and iliopectineal lines are disrupted on the anterior-posterior pelvic radiograph. The remaining amount of dome determines stability after closed reduction. The caudal fragment of most transverse acetabular fractures is the unstable portion hinging on the symphyseal ligaments. In this example, the femoral head is no longer congruent with the intact dome fragment and is displaced medially along with the displaced caudal segment. The related symphyseal injury for this patient is also noted. Impaction injuries of the superolateral femoral head as well as along the transverse acetabular fracture surface are noted with such fracture lines and displacement patterns.

The acetabular dome is involved to some extent by the transverse fracture plane. Letournel subclassified transverse fractures depending on their dome involvement. Whereas transtectal transverse fractures involve the weight-bearing dome, juxtatectal transverse fractures preserve the dome and exit at the junction of the dome and fossa acetabuli. Infratectal transverse patterns divide the fossa acetabuli. Typically, more intact dome before fracture involvement correlates with improved hip stability, congruity, and outcome. In cadaveric mechanical evaluations, step malreductions of transverse acetabular fractures in the superior articular surface resulted in abnormally high contact forces that in clinical practice should predispose to the development of posttraumatic arthritis.

Certain transverse acetabular fractures are associated with medial displacement of the femoral head along with the caudal fracture fragment. As the fracture displacement occurs, the femoral head can sustain a superolateral impaction fracture or the intact upper portion of the acetabular fracture line can be crushed.

In these fractures, the femoral head may remain beneath the weight-bearing dome or follow the caudal segment’s displacement depending on several factors. For transtectal patterns, there may be insufficient intact dome laterally for the femoral head to remain stable. Muscular spasm, especially from the iliopsoas muscle, causes further displacement of the femoral head medially and superiorly through the fracture. As the intact dome coverage expands medially with juxtatectal and infratectal transverse patterns, femoral head stability improves.

Transverse acetabular fracture patterns or other associated fracture patterns with a transverse fracture component should alert the treating physician to potential associated pelvic ring injuries, especially ipsilateral SI joint injuries. Careful study of all preoperative imaging is imperative. If the commonly stable cranial fracture fragment is rendered unstable or is displaced because of an ipsilateral SI joint injury or sacral fracture, then both the upper and lower portions of the transverse fracture are unstable. The upper fracture fragment of such a transverse acetabular fracture pattern is displaced and unstable because the ipsilateral SI joint is disrupted or an unstable ipsilateral sacral fracture is present. In this unusual scenario, the transverse acetabular fracture functions as an associated both-column acetabular pattern because there is no articular component in continuity with the intact hemipelvis.

Similar to certain posterior column acetabular fractures and their relationship with the sciatic nerve, transverse fractures can also be associated with sciatic nerve injury if the posterior column portion of the transverse fracture plane parallels the nerve pathway ( Fig. 41-16 ).

Depending on the fracture orientation through the area of the posterior column, transverse acetabular fractures can be associated with sciatic nerve injury. A, This woman was injured in an automobile accident, resulting in a displaced transverse acetabular fracture. She had sciatic nerve palsy on initial presentation. The anterior-posterior plain pelvic radiograph demonstrates that the posterior column component of the fracture parallels the sciatic nerve’s course. B, The surface rendered posterior three-dimensional image also shows the fracture orientation in the area of the sciatic nerve. C, The sciatic nerve is seen on the axial computed tomography image to be located between the posterior fracture surfaces. A posterior surgical exposure was selected so the sciatic nerve could be explored. It was trapped between the fracture fragments and was in continuity but contused. A sciatic neuroplasty was performed, and then the fracture was cleansed, manipulated, reduced, clamped, and stabilized.

Transverse Fractures with Associated Posterior Wall Involvement

Transverse with associated posterior wall acetabular fractures are common patterns combining the elementary transverse fracture plane with an additional displaced posterior wall component. The AP radiograph demonstrates both iliopectineal and ilioischial line disruptions along with the loss of the posterior wall convex edge because of its displacement. Often the displaced wall is noted superimposed on the dome area on this radiograph. If the radiograph is examined carefully, the transverse fracture plane’s displacement through the anterior wall area is seen as a lucent gap. On the AP radiograph, the femoral head has several location options with these injuries. The simplest occurs when the femoral head is noted to be congruent with the dome. Another displacement pattern occurs when the femoral head follows the posterior wall displacement. Another pattern occurs when the femoral head follows the transverse caudal segment and is displaced medially. The oblique images are obtained after closed reduction of the femoral head beneath the dome. The iliac oblique image shows the exit points of the transverse fracture line in the areas of the posterior column and anterior wall. The OO image demonstrates the anterior column exit point of the transverse fracture as well as the displaced posterior wall fracture fragment and the defect left because of its displacement. It is not unusual in unstable patterns for the femoral head to redislocate as the patient is turned for each image and the body weight or limb weight is applied onto the injury. After closed reduction, an AP radiograph in traction may reveal a previously missed superolateral femoral head impaction fracture. Just as for any fracture that includes a transverse fracture component, the ipsilateral SI joint and sacral areas should be carefully assessed on the radiographs for injuries and displacements.

The pelvic CT scan reveals the transverse fracture orientation, dome area involvement, and specific exit sites as well as any loose bodies within the joint or marginal impaction associated injuries. Posterior wall comminution is not always obvious on the plain images and is best seen on the CT scan. The CT scan may also confirm femoral head impaction lesions ( Fig. 41-17 ).

A and B, This patient has a transverse with associated posterior wall acetabular fracture. The iliopectineal and ilioischial lines are disrupted and the posterior wall fragment is displaced and also comminuted. The caudal portion of the transverse fracture is unstable and displaced on its symphyseal hinge. The dome has been split by the transverse fracture, so it is subclassified as a transtectal pattern.

Posterior Column Fracture with Associated Posterior Wall Involvement

In these uncommon injuries, the ilioischial line is disrupted, and the posterior wall defect and displacement are seen on the AP radiograph. The iliac oblique image shows the posterior column component’s exit through the greater sciatic notch, but the OO view identifies the displaced posterior column fracture exit at the ischium and the displacement of the posterior wall fracture fragment. The pelvic CT scan should be examined not only for the specific fracture-related details but also for the local soft tissues. An injury to the superior gluteal artery or vein may cause deep buttock asymmetry or accumulated vascular contrast agent on the scan because of local bleeding. The details cited earlier regarding both posterior column and posterior wall fracture elementary patterns are also relevant here.

Anterior Column Fracture with Associated Posterior Hemitransverse Injury

Acetabular fracture patterns that involve the anterior column as well as associated posterior hemitransverse injuries combine any variety of anterior column fracture with an additional fracture line that splits the posterior column, usually through the greater sciatic notch. Both the iliopectineal and ilioischial lines are disrupted on the plain AP radiograph. The iliac oblique pelvic radiograph reveals the anterior column fracture component’s exits both along the iliac crest and through the anterior wall area, as well as the posterior hemitransverse fracture component’s exit point, usually through the greater sciatic notch. These injuries can be unstable although each fracture component and the oblique radiographs demonstrate the instability and displacement sites. Just like for anterior column elementary patterns, the anterior column component of the fracture is variable. The posterior hemitransverse component predictably divides the greater sciatic notch. These fractures are common in elderly patients ( Fig. 41-18 )

In this example of an anterior column with associated posterior hemitransverse acetabular fracture, the iliopectineal and ilioischial lines are disrupted. The acetabular dome remains a part of the intact ilium, and there is no obvious fracture of the inferior ramus or posterior wall on this anterior-posterior pelvic radiograph. The femoral head and acetabular fracture fragments are displaced medially, and the superolateral femoral head and medial acetabular dome region are both severely impacted.

T-Type

The T-type acetabular fracture is simply a transverse acetabular fracture but with the unstable caudal segment split into two individual unstable segments. When viewed laterally, this acetabular fracture patterns is shaped like the letter T. For example, the anterior column portion of the fracture line begins at the anterior wall area and extends along the iliopsoas gutter across the pelvic brim and descends the quadrilateral surface. The posterior column portion of the fracture line begins at the greater sciatic notch and descends to split the posterior wall area and meets the anterior column fracture line at the quadrilateral surface. The fracture line that divides the quadrilateral surface is a common fracture line. It is the vertical fracture line that descends from the transverse component to make this a T-type fracture pattern.

The anterior column component is unstable because of the symphyseal hinge. The posterior column component is tethered by the sacrospinous and sacrotuberous ligaments. These injuries often have central displacement of the femoral head between the fracture fragments, or the femoral head can remain attached to the posterior column fragment if the ligamentum teres is intact.

On the AP radiograph, both iliopectineal and ilioischial lines are disrupted, and the femoral head may be dislocated away from the intact dome. The ischial fracture may be minimally displaced and not always obvious. The iliac oblique image reveals that the posterior column exits at the greater sciatic notch and ischial ramus. The OO identifies the anterior column exit site and displacements. CT details each component’s location ( Fig. 41-19 ).

T-type acetabular fracture. The anterior column fracture is much less displaced than the posterior column fracture component. The femoral head remained congruent with the displaced posterior column component. Despite the severity and direction of the fragment displacement, the sciatic nerve and superior neurovascular bundle remained intact before and after closed reduction. A, On the anterior-posterior pelvic radiograph, the displaced posterior column fracture fragment and dislocated femoral head are easily seen. The ilioischial line is disrupted. The anterior column fracture is minimally displaced and therefore the iliopectineal line disruption is more difficult to identify, B, The iliac oblique three-dimensional model demonstrates the fracture surfaces and displacements, C, The dislocated femoral head remains congruent with the displaced posterior column fracture fragment. The local hematoma is notable as well on this axial image at the level of the intact acetabular dome, D, Identifying the T-type fracture lines is improved after closed reduction of the femoral head beneath the intact weight-bearing dome.

Associated Both-Column Fracture

The associated both-column acetabular fracture pattern is thought by many surgeons to be the most difficult of all 10 acetabular fracture types. In these injuries, the articular dome and all other articular fracture fragments are without connection to the intact hemipelvis. In all nine other patterns, at least some portion of the articular acetabulum remains attached to the intact hemipelvis. Because of this traumatic fracture-separation of the articular fragments from the stable ilium, some use the term “floating acetabulum” for these patterns. Because this term is misleading and not descriptive, most surgeons do not use it.

Associated both-column acetabular fractures have several consistent fracture fragments. The intact iliac piece is the stable component. Its caudal extent represents the “spur sign,” so named because it resembles a cockspur on the OO image, as the unstable articular fragments displace from it medially. Such medial articular fragment displacements cause the intact ileum’s caudal extent (the “spur”) to appear prominent as it remains in its normal site. When seen on the OO radiograph, this spur sign is indicative of an associated both-column acetabular fracture. Inexperienced surgeons may confuse a displaced posterior wall acetabular fracture with the spur sign of an associated both-column fracture because both are seen on the OO image ( Fig. 41-20 ).

The “spur sign” represents the caudal portion of the intact ilium and is indicative of an associated both-column acetabular fracture pattern. A, Named for its similar appearance to a rooster’s cockspur, the “spur sign” is seen best on the obturator oblique (OO) injury radiograph because the articular portions of the fracture displace medially leaving the intact ilium in profile. B, In this patient with severe fracture fragment displacement, the caudal aspect of the intact ilium (spur) is also notable on the anterior-posterior radiograph. C, This patient has a displaced posterior wall acetabular fracture. Similar to the “spur sign,” in associated both-column fracture patterns, the displaced posterior wall fracture is also best seen on the OO image, but the two should not be confused.

When articular fragment displacement is minimal yet there is still no articular connection to the intact iliac segment, no spur sign is obvious, but an associated both-column acetabular fracture pattern is the correct diagnosis. In some patients, the intact iliac caudal extent is obvious even on the AP and iliac oblique radiographs, so it is possible to see the spur on these other images. It is easy for the clinician to see that which he or she knows to look for ( Fig. 41-21 ).

This patient has an associated both-column fracture that initially may seem to be an anterior column with associated posterior hemitransverse. The dome fragment is not in continuity with the intact iliac fragment, but this fact may not be entirely obvious on initial inspection. Further study of the anterior-posterior plain radiograph ( A ) shows the asymmetry and displacement of that fragment. B and C, The three-dimensional model when viewed posteriorly reveals the spur sign. D, The axial computed tomography image also shows the displacements.

Besides the intact iliac component, associated both-column fractures have several other consistent components. The upper anterior column fracture fragment usually contains the majority of the dome and may be incomplete at its iliac crest exit point, as previously described for anterior column fracture patterns. If so, the anterior column fragment may be displaced and relatively stable because of the deformed yet incomplete fracture along the crest. The lower anterior column fracture fragment typically includes the articular anterior wall and pubic ramus limbs. The posterior column component typically exits the greater sciatic notch and ischial areas. It is not unusual for the pelvic brim to have some degree of cortical comminution. In some patterns as detailed in the earlier section on posterior wall fracture, the posterior wall fracture component is an avulsion injury caused by medial displacement of the proximal femur.

Variant Patterns

Certain acetabular fractures do not fit Letournel’s classification system ( Fig. 41-22 ). These variant patterns exist and must be recognized after routine patterns have been ruled out. For example, a T-type fracture pattern may have an associated displaced posterior wall fracture. The “T-type with associated posterior wall” fracture pattern is not an option in the Letournel classification scheme, but this and other variant patterns do occur, and the treating physician needs to be aware of and able to plan treatment for such variant and hybrid fracture patterns. Remember that the Letournel acetabular classification system was initially developed simply to guide the surgical exposure decision. Just as for the other fractures, the variant patterns’ radiographic details will guide the operative planning. Unusual position of the lower extremity at injury, poor bone quality, or extreme loading conditions are responsible causes for these injuries. Variant patterns are assessed and managed routinely. Their fracture specifics may necessitate more detailed planning, more extensile exposure, or special fixation tools. Dramatic impaction injuries, for example, may demand allograft bone or other suitable material to fill the defects. Acetabular fractures in association with unstable pelvic ring injuries are included as variant patterns as well ( Fig. 41-23 ).

Not every acetabular fracture can be classified using Letournel’s scheme of elementary and associated patterns. Some fractures, such as this one involving the quadrilateral surface, are best classified as variant patterns. A, The obturator oblique three-dimensional image demonstrates the quadrilateral surface fracture and medial displacement. B, The axial computed tomography image further demonstrates the fracture sites and displacement pattern.

Acetabular fractures and pelvic ring disruptions can occur together, usually after high-energy traumatic events. Those acetabular fracture patterns that involve the two structural columns and thereby disrupt the pelvic ring through the acetabular region are the transverse, transverse with associated posterior wall, T-type, anterior column with associated posterior hemitransverse, and associated both-column fractures. A, In this patient, the right-sided juxtatectal transverse acetabular fracture is a component of the overall pelvic ring disruption along with the symphysis pubis, left pubic ramus, and left sacroiliac joint injuries. Subluxation of the right femoral head medially from beneath the weight-bearing dome is noted. The reduction sequence should prioritize the acetabular fracture whenever the patient’s overall condition allows. Early pelvic ring reduction and stabilization procedures must respect the eventual need for acetabular fracture reduction and fixation. Initial malreductions of the other ring components will obviate eventual accurate acetabular reduction.

B, Because of her overall clinical status upon presentation, the acetabular fracture and pelvic ring injuries were treated as a part of her overall resuscitation effort. The acetabular facture and the other pelvic ring injuries were treated with closed reduction, percutaneous screw fixations, and an anterior external fixation frame. The femur fracture was then stabilized with an antegrade, locked, and reamed nailing after the pelvic–acetabular procedure. In patients like this, the initial percutaneous fixation does not have to be definitive treatment, especially when the acetabular manipulative reduction is inaccurate. In this patient, the right transverse acetabular fracture closed reduction should have been revised to an open reduction with internal fixation after her overall condition was stable. Her right hip developed symptomatic arthrosis 3 years after injury, perhaps caused by the malreduction from percutaneous management.

Decision Making

The management goal for acetabular fractures is a painless and functional hip joint without complications. Selecting the best treatment option is a complex clinical decision based on numerous factors related to the patient, the physician, the facility, and others.

The following questions arise when determining treatment:

• 1.
  

  Is the patient medically stable? If not, how can he or she be made stable? Would urgent operative management of the acetabular fracture actually help to stabilize the patient overall? Are there open wounds in communication with the fracture?

  
  
• 2.
  

  Could the patient withstand any planned operation, much less an extensive one?

  
  
• 3.
  

  Could the patient withstand traction management or prolonged bed rest?

  
  
• 4.
  

  Are there patient-related medical, physical, psychosocial, or other issues that adversely affect either operative or nonoperative management? For example, is noncompliant behavior anticipated despite the treatment choice?

  
  
• 5.
  

  Are the fracture fragments and hip joint stable or unstable?

  
  
• 6.
  

  Is the fracture displaced or not? If displaced, where specifically are the displacement sites and to what extent? Is the hip congruent? Does the femoral head remain beneath the intact weight-bearing dome during oblique imaging?

  
  
• 7.
  

  If displaced, is there sufficient relative (secondary) congruity of the fracture fragments with the femoral head?

  
  
• 8.
  

  Is there ample bone to allow routine reduction and stable fixation techniques, or are special considerations indicated?

  
  
• 9.
  

  Will the fracture pattern specifics allow for accurate reduction, or will fracture-related issues, such as extensive dome comminution or crush injury, prevent reduction or stable fixation?

  
  
• 10.
  

  Will associated femoral head traumatic issues such as superolateral or other zone impaction fractures adversely affect the result apart from the acetabular repair?

  
  
• 11.
  

  Are there prior hip issues such as arthritis, previous hip injury, aseptic necrosis, or others that would impact the treatment plan?

  
  
• 12.
  

  Does the surgeon, a colleague, or regional referral center have sufficient experience and expertise in treating similar acetabular fractures?

  
  
• 13.
  

  Does the medical facility have sufficient ancillary support (e.g., intraoperative imaging technicians) and the necessary equipment?

Even though clinicians would rather have some absolute radiographic measurement to guide their acetabular management decision, the individual patient’s overall medical condition is the primary determinant. First and foremost, the patient must be able to endure the chosen treatment. Although many clinicians begin with the specific fracture pattern when choosing a treatment plan, the overall patient condition guides treatment considerations. In some situations, the acetabular fracture is related to the patient’s overall instability and urgent acetabular reduction and fixation are indicated as a part of the overall patient resuscitation. When the initial resuscitation of the patient is successful, the surgeon should focus on the fracture pattern and associated local soft tissue injuries. Fracture stability is related to several factors; the primary one is how much weight-bearing dome or intact acetabulum remains for the femoral head to articulate with. Biomechanical studies have shown that acetabular fracture stability decreases with higher applied loads across fracture surfaces and with a less intact dome. Because of this dome coverage issue, roof arc measurements can be used to quantify in three radiographic views and on CT scanning the amount of intact dome.

Roof arc angles are measured on the AP and two oblique radiographs. A line is first drawn on the radiograph to set the horizontal standard and correct for patient positioning error on the x-ray cassette. For elementary patterns, the ischial tuberosities on each side are reliable as long as the injured side remains uninvolved by the fracture-displacement. For example, in some elementary transverse and posterior column fracture patterns, the ischial area may be involved by the fracture to a degree that the tuberosities could not be used for the horizontal standard measurement. In these and the associated patterns, some other intact osseous landmark is used to set the horizontal standard. Next, a perpendicular vertical line is drawn from the horizontal standard line through the center of the hip joint, which, depending on its displacement, may or may not be the center of the femoral head. The next line is drawn from the center of the hip joint/femoral head to the acetabular fracture’s articular edge on that particular view. The roof arc angle is measured between the vertical line and the articular edge line. As the roof arc angle expands, so does the acetabular dome coverage and in turn so does the hip joint congruity and perhaps stability. Mechanical and clinical studies have offered a variety of roof arc angle limits for improved results ( Fig. 41-24 ).

The measurements of acetabular fracture roof arc angles are shown on these three pelvic radiographs. A, On the anterior-posterior (AP) pelvic radiograph, the right ischial tuberosity is involved by the fracture, so the horizontal standard line must be estimated. The femoral head is slightly subluxated on the AP view, so the center hip joint determination accounts for this. A vertical perpendicular line is drawn from the horizontal standard line through the hip joint center. Next and from the hip center, a line is drawn to the acetabular fracture edge. The angle between the perpendicular vertical and fracture edge lines is the roof arc angle. B and C, The process is repeated for the iliac and obturator oblique images.

The physician measuring the roof arc angles must remember that the center of the hip joint is not always the femoral head itself because the head may be displaced from the anatomic hip joint center. If this occurs, then the hip is incongruent, and the fracture is displaced sufficiently that roof arc measurements are in fact unwarranted because surgery is indicated.

Closed treatment of acetabular fractures should be based on hip congruity and fracture instability. Stability is determined from the history reflecting the energy of the traumatic event and from the radiographs. Commonly, unstable acetabular fractures will be easily identified on the oblique plain pelvic images. Even minimally displaced fractures seen on the AP image can be unstable and will show displacement and subluxation when body weight is applied to the fracture during oblique imaging. Final determination may require an examination of the fracture under anesthesia and real-time fluoroscopy. The fluoroscopic examination under anesthesia should be performed using the AP as well as both oblique views. The C-arm must be positioned correctly to view possible instability sites without obstructing the necessary limb positions and movements needed to challenge the fracture stability. For posterior wall acetabular assessment, the C-arm is positioned on the ipsilateral side to injury so the OO image is obtained and the unit does not obstruct hip flexion, adduction, and internal rotation. For fractures involving the posterior column, the C-arm unit is positioned on the opposite side to allow the iliac oblique view without obstructing limb movements. The AP view has limited use other than for medial instability assessment because the fluoroscope obstructs most limb movements other than central loading.

If the fracture is congruent and stable, protected weight bearing is chosen, and then serial pelvic radiographs are used in follow-up examinations to ensure no further displacement. If the hip is congruent yet unstable without traction, then skeletal traction is used to maintain the reduction while the fracture heals ( e-Fig. 41-1 ) or percutaneous fixation is used. The traction pin is best inserted during this same anesthetic examination using the C-arm to perfectly position the pin. A threaded pin of sufficient diameter is recommended when several weeks of traction is anticipated. The distal femoral traction pin is inserted to avoid the knee joint and local vascular structures.

Closed reduction and percutaneous fixation has limited indications but was selected for this patient’s acetabular fracture, while the ipsilateral iliac crescent fracture–sacroiliac joint dislocation had open reduction and internal fixation (ORIF). A to C, The patient was injured in a motorcycle accident and had a 12-cm-diameter, circular-shaped, and highly contaminated traumatic open wound on the lateral proximal thigh region. The open wound underwent several aggressive débridements, but contamination was identified at each operation. D and E, ORIF of the posterior pelvic injury was accomplished using a dorsal exposure remote from the open wound. Percutaneous acetabular fixation was then performed to avoid the risk of deep infection caused by the lateral thigh wound contamination. Patients like this one with excellent dome coverage of the femoral head and a congruent hip are good candidates for percutaneous acetabular columnar fixation.

If traction is selected, the patient is committed to a prolonged 6- to 8-week period of bed confinement. If traction is chosen, it is also important to know if the fracture reduction is maintained while the patient is upright in bed. A portable AP pelvic radiograph with the patient awake and in traction confirms this fact and ensures that the hip is not overdistracted by excessive weight ( Fig. 41-25 ). An upright chest allows the patient to avoid problems associated with recumbency. Every patient in traction is at risk for aspiration, such that the traction is adjusted to allow head of the bed elevation while maintaining the fracture reduction.

Traction was helpful in this elderly patient. A, The injury radiograph shows significant instability and displacement. B, Distal femoral skeletal traction was applied, and this anterior-posterior pelvic radiograph was then obtained with the patient in traction. It demonstrates improved reduction of the fragments. In many patients, skeletal traction improves realignment of the displaced fragments, combats muscle spasm, provides patient comfort, protects the femoral head and articular fragments from further damage, and reminds the nursing staff of the acetabular fracture.

Operative repair of acetabular fractures is difficult; can be extensive; and is associated with numerous problems, including operative bleeding. Because of this fact, the patient’s cardiopulmonary and medical condition should be capable of withstanding surgery.

Some patients may refuse to receive blood or blood products based on their religious beliefs and therefore may not be candidates for open fracture reconstructive techniques. Blood salvage systems during surgery diminish this potential problem if the patient will allow such system to be used.

If there are no patient-related issues, then the fracture pattern is evaluated for displacement and instability. Treating physicians must remember that displacement and stability are not necessarily linked. Certain displaced fractures may demonstrate relative stability, especially when the peripheral portions of the fractures are incomplete. Conversely, nondisplaced or minimally displaced fractures are not necessarily stable. For example, certain transverse acetabular fractures may have essentially no displacement on the AP radiograph, but the oblique radiographs reveal their displacements and instability. In these situations, the patient’s body weight along with gravity cause fracture displacement. Examination of the hip under anesthesia and fluoroscopy can also identify dramatic fracture instability in minimally displaced injuries ( Fig. 41-26 ).

A and B, This acetabular fracture’s instability is revealed by the oblique images. C and D, This patient had a small, peripheral posterior wall acetabular fracture and an unstable pelvic ring injury. During the same anesthetic session as the pelvic ring stabilization, the acetabular fracture was examined under fluoroscopy and noted to be unstable, with 30 degrees of passive hip flexion. The extraarticular medullary ramus screw is located posterior to the hip joint on this view.

For stable fractures, some clinicians measure roof arc angles on the pelvic plain radiographs and the subchondral arcs on the pelvic CT to determine congruity between the femoral head and acetabular dome region. As the intact dome area expands, thereby improving femoral head coverage, the roof arc angle increases, and better results are anticipated.

Bone quality issues are important factors to consider before surgery. Usually this problem is seen most in elderly patients and those with other bone diseases such as osteogenesis imperfecta. The cortical surfaces may not be sufficient to hold a reduction clamp and support fixation plates. Children and adolescent patients with acetabular fractures warrant special considerations also. The triradiate cartilage is usually injured in younger patients, and standard sized implants may not fit younger pediatric patients. Depending on the status of the triradiate injury and the patient’s age, the fixation implants may require removal after healing, and physeal bar formation is likewise evaluated radiographically in follow-up clinic visits ( Fig. 41-27 ).

A, Acetabular fractures occur rarely in children but may involve the triradiate cartilage, as in this patient. B, Operative management is indicated for displaced and unstable fractures as in adult patients. The implant size must be adjusted to fit the patient. Physeal bar formation can result depending on the patient’s age, fracture pattern, and hip development status at the time of injury. Early implant removal should be considered and serial radiographs are indicated to evaluate for physeal bar formation in younger patients.

Special equipment has value when treating such “bone-deficient” fractures operatively. Bone graft substitutes, improved fixation constructs, and newer implant technology may all be needed to manage these injuries. Comminution of the quadrilateral surface; medial dome impaction injuries; significant crush or impaction, especially to the femoral head cranially; frail peripheral posterior wall fractures; and chondral damage are but a few of the nuisance clinical issues that complicate and frustrate successful acetabular fracture management. Specially designed or complex contouring of routine surface implants may be needed to stabilize some of these complex fracture patterns.

Articular chondrocancellous crush injuries along the primary fracture lines are difficult to reduce accurately. Small focal impaction fractures are elevated, reduced to the femoral head after the primary fracture lines are reduced and stabilized, and the defects are supported with bone graft. Extensive impaction fractures including more zones of injury and more comminution are more difficult to accurately reduce and support and therefore correlate directly with posttraumatic arthritic changes ( Fig. 41-28 ).

Marginal impaction is commonly associated with posterior wall acetabular fracture-dislocations. A, This axial image from the injury computed tomography scan demonstrates the chondrocancellous fragments on the fracture’s edge that are crushed into the normal cancellous bone of the posterior column. B and C, After surgery, the posterior wall fracture reduction is shown as is the bone graft material used to support the reduced, previously impacted fragments.

Operative management restores articular congruity and provides stable fixation. These factors should improve the clinical result by decreasing the incidence of posttraumatic arthritis and allowing early patient and joint mobility. Operative management is advocated for patients with displaced and unstable acetabular fractures who are appropriate surgical candidates.

Operative Timing

Operative treatment of an acetabular fracture occurs when the patient is medically stable, when the surgeon understands the fracture and its treatment details, and when the appropriate operative team is available. Usually this interval is between 1 and 5 days after injury. Some surgeons believe that earlier operative intervention allows the fracture surfaces and local tissues to bleed more than if surgery occurs several days after injury. Delay for posterior approach is not associated with decreased blood loss or complications. Recent evidence indicates immediate anterior approach in the appropriately resuscitated patient may be beneficial to the patient’s overall physiology. The surgeon must also remember that fracture surface cancellous bone bleeding halts when the fracture surfaces are reduced and stabilized. Knowing this, the surgeon performs the surgical exposure, prepares the fracture fragments for clamp and implant applications, and does so without disturbing the fracture surface clots. Removing the fracture surface clots immediately before reducing the fracture decreases operative blood loss. A blood salvage suction system is also advocated to recycle surgically related blood loss. Recent investigations suggest that blood salvage systems may not be worth the additional expense.

Urgent operative management is recommended for unusual patients with open fractures, irreducible fracture-dislocations, nerve changes after closed reduction, and buttock or iliac compartmental syndrome ( e-Fig. 41-2 ). Rarely, acetabular fracture reduction and fixation will be needed to diminish fracture-related bleeding as a part of the patient’s ongoing resuscitation. Open acetabular fractures can be staged as an initial irrigation and débridement procedure followed by open reduction and fixation. The open wounds are commonly located in the iliac crest region or the inguinal area. The initial wound débridement is performed in consideration of the definitive surgical exposure. If the patient’s condition and the overall situation are optimal, the reduction and fixation can be performed during the initial anesthetic or at a later date as a separate procedure, allowing the surgeon more time to plan the operative strategy. Certain fracture patterns are at risk for sciatic nerve changes after manipulative reduction. These include any pattern involving displacement through the posterior column or wall areas, especially when the fracture plane parallels the sciatic nerve’s course. Compartmental syndrome is also unusual but can occur in the buttock and iliac areas. Buttock compartmental syndrome has been linked to superior gluteal vascular injury caused by displaced acetabular fractures involving the greater sciatic notch. The physical examination demonstrates buttock asymmetry and dramatic swelling. These findings are more difficult in obese patients, but the pelvic CT scan demonstrates the buttock asymmetrical swelling and soft tissue density. Before operative compartment release, angiographic evaluation, and embolization of the potentially injured artery should be considered. Patients with internal iliac compartmental syndrome caused by acetabular fracture usually have minimal fracture displacement but significant bleeding into the iliopsoas muscle or internal iliac fossa. They present with femoral and LFCN dysfunction, but otherwise their physical examination findings may be unremarkable. Pelvic CT demonstrates the asymmetrical swelling and soft tissue density. Before surgical release, a routine screening coagulation panel is obtained and any abnormalities corrected.

A and B, Irreducible acetabular fracture-dislocations are unusual but still demand a precise preoperative surgical plan. This patient sustained bilateral lower extremity injuries, including a left-sided acetabular fracture-dislocation, after he was involved in a motorcycle crash. Attempted closed reduction of the acetabular injury in the emergency department failed. C, In the operating room under general anesthesia, a proximal femoral pin was inserted to manipulate the hip, but it also failed to move the proximal femur. D to E, A Kocher-Langenbeck exposure was performed acutely; the obturator internus muscle tendon was obstructing the acetabular reduction. It was displaced anteriorly relative to the femoral neck and prevented all attempts at closed reduction. The tendon was incised, and the femoral head was then relocated. The acetabular fracture was then reduced and stabilized.

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