Classification and Anatomy

Orthopaedic surgeons must determine the anatomy and mechanism of the pelvic injury in order to classify it. The inherent bony stability of the pelvis is very limited. Fig. 22.1 demonstrates the key role that ligaments have in maintaining pelvic stability. One can easily see that disruption of the ligaments causes the pelvis to become completely unstable due to the lack of intrinsic bony stability. When pelvic instability is present, anatomic operative reduction and fixation generally increases the stability of the pelvis. Appropriate fracture reduction is especially important in the posterior pelvic ring because a malreduced fracture may make safe iliosacral screw fixation impossible.3 In classifying pelvic injuries, the most significant information for the orthopaedic surgeon to determine is (1) where the pelvis is broken, (2) the stability of the fracture, and (3) the deformity that is occurring in the pelvis. The specific location of the injury is easily determined by an imaging evaluation, including anteroposterior (AP), inlet, and outlet radographs and computed tomography (CT) scan of the pelvis. Determining the stability of the pelvis is more complex. Stability is defined as the ability of the pelvic ring to withstand physiological forces without abnormal deformation. The stability of the pelvis is determined by both physical and radiographic examination. The physical exam uses palpation to ensure that the anterior superior iliac spine (ASIS), iliac wing, and symphysis are located in their proper positions. Furthermore, an ASIS compression test and iliac wing compression test should be performed. The ASIS compression test is performed by placing the palms of one′s hand on the right and left ASIS and rocking the pelvis. In a hemodynamically unstable patient, this test should be performed only once. It determines whether the pelvis rocks as a unit or there is complete separation of the two halves of the pelvis. The ASIS compression test evaluates the external rotational stability of the hemipelvis. The iliac wing compression test is performed by placing the palms of the hands on the outside of the iliac wings and pushing the two wings together. This test evaluates internal rotational stability.

Vertical instability is much more difficult to determine by physical examination. Traction or impaction of the leg using fluoroscopy (the “push-pull” test) can show caudal and cephalad migration of the hemipelvis. Any degree of dissociation between the two sides of the pelvis is often associated with vertical instability. The ASIS and iliac wing compression tests are performed often at the bedside, whereas the vertical migration tests are easier to perform under anesthesia in the operating room. Tests for vertical instability should not be done when sacral fractures are present because of the risk of injury to the sacral nerve roots. Radiographic signs of instability include sacroiliac displacement of greater than 5 mm in any plane or a posterior (ilium or sacral) fracture gap rather than impaction. Some radiographs clearly show instability, whereas other findings are much more subtle (Figs. 22.2 and 22.3). Using the combination of radiographs and physical exam, the surgeon can determine whether the pelvis is stable and can be treated nonoperatively, or is unstable and requires reduction and stabilization.

Several classifications of pelvic ring injuries have been proposed. A simple classification that is used at the author′s center is the Bucholz classification.4 Type I injuries are stable and do not require fixation. These injuries include isolated pubic rami fractures or minor (< 2 cm) disruptions of the pubic symphysis. Such injuries may be accompanied by nondisplaced or impacted sacral fractures. Bucholz type II injuries have rotational instability, with either internal or external rotation deformity, and may require reduction and stabilization. Bucholz type III injuries have complete dissociation of the hemipelvis from the rest of the body and are characterized as being both vertically and rotationally unstable (Fig. 22.4).

The most critical analysis of the injury prior to fixation is the actual deformity of the pelvic injury. Only by defining the deformity can the surgeon plan the appropriate reduction maneuvers to anatomically reduce the pelvis. Unfortunately, the complexity of the pelvis makes analysis of the deformity quite difficult. It is helpful to think of the deformity on an x-, y-, and z-axis (Fig. 22.5 and Table 22.1).5–7 Each axis has a translational deformity as well as a rotational deformity. The rotational deformities include flexion or extension around the x-axis, internal or external rotation around the y-axis, and abduction or adduction around the z-axis. The translational deformities of the pelvis include diastasis or impaction along the x-axis, cephalad or caudad translation along the y-axis, and anterior or posterior translation along the z-axis.

In a pelvic injury, the deformity is always a combination of rotational and translational deformities. The hemipelvis does not deform along a single point, but its deformity can be represented as a vector of deformity from an anatomically positioned hemipelvis. Understanding the radiographic landmarks and how they change with various deformities enables the surgeon to define the deformity and thus the preoperative plan for reduction. Furthermore, these radiographic landmarks are essential in assessing reduction. Cranial translation of greater than 1 cm can be difficult to appreciate without leveling the pelvis and performing measurements on the pelvis (by drawing a transverse line parallel to the cephalad border of the sacrum and a perpendicular line measuring the dome height for leg length discrepancy and ischial height for sitting imbalance determination). Assessing rotational deformities is equally challenging if the surgeon does not center the pelvis by positioning the radiographic beam to get a pure AP of the sacrum. An apparent deformity of the hemipelvis can be the result of a true traumatic deformity, tilting of the patient while the radiograph is taken, or both.

Understanding the mechanism of injury allows the surgeon to predict the type of deformity. Burgess et al8 proposed a classification of pelvic ring injuries that is based on the underlying mechanism of injury. Pelvic ring injuries are divided into anteroposterior compression, lateral compression, vertical shear, and combined patterns (Table 22.2). The anteroposterior and lateral compression injuries are each divided into three subtypes with increasing degrees of instability. This scheme has proven valuable because it helps predict instability and determine which reduction and fixation strategies are appropriate for a particular case. For example, a patient who is hit from the side in a motor vehicle accident often has a lateral compression type of injury causing an internal rotation, flexion, and adduction deformity of the hemipelvis (Figs. 22.6 and 22.7).6,7 Likewise, patients who fall on their back or are crushed from the front often have an open-book pelvic injury with an external rotation and abduction deformity (Figs. 22.8, 22.9, 22.10).

Source: From Burgess A, Eastridge BJ, Young JWR, et al. Pelvic ring disruptions: effective classification system and treatment protocols. J Trauma 1990;30:848–856. Reprinted with permission.

Nonoperative Treatment

A pelvic fracture that is classified as a Bucholz type I pelvic injury is stable and should be treated using nonoperative techniques. Another type of pelvic ring injury that can be managed nonoperatively is the lateral compression injury with impaction of the sacrum and minimal displacement of the anterior ring (Figs. 22.6 and 22.11). Additionally, fractures that involve the pubic rami without a clear injury posteriorly also do not require surgical treatment. Rarely, avulsion of the ischium, ASIS, or anterior inferior iliac spine (AIIS) occurs. In these cases the pelvic ring is stable; however, there can be significant displacement of the avulsed fragment. There are no definitive recommendations in the literature on operative versus nonoperative treatment of displaced avulsion fractures, and decision making should occur on an individual case-by-case basis. The author uses greater than 1 cm of displacement as an indication to operate on these avulsions. Minimally displaced or impacted injuries of the pelvis are both radiographically and mechanically stable. These injuries can be treated by touch-down weight bearing for 6 to 8 weeks. Initially, X-rays should be taken weekly to ensure that no additional deformity occurs; 20% of lateral compression injuries were found to have displaced in follow-up X-rays, as were 68% of complete sacral injuries and bilateral superior and inferior rami fractures.9 Close radiographic follow-up is mandatory. After 6 to 8 weeks, more aggressive exercise and range-of-motion ambulation training with physical therapy is recommended.

Surgical Treatment

Indications

The indications for surgical treatment of pelvic ring injuries include failing nonoperative treatment, as well as pelvic injuries that are unstable or that have unacceptable deformity. As mentioned in the nonoperative section, avulsion fractures should be reviewed on a case-by-case basis. In general, avulsion with displacement greater than 1 cm leads to significant pain and weakness of the involved muscle that is attached, and therefore I recommend operative fixation of these injuries. An additional indication for surgery is pelvic injuries that may be stable but have significant deformity, such as an internal rotation deformity as a result of a lateral compression type of injury in which there is greater than 20 degrees of internal rotation of the hemi-pelvis, or greater than 1 cm leg length discrepancy (Fig. 22.12).6,7 Additionally, these internal rotational deformities can cause a ramus fracture that pierces the bladder or vagina. In these cases it is necessary to externally rotate the hemipelvis to remove the bone from the bladder or vagina. Because these are stable injuries, a simple external fixator can be used to externally rotate the pelvis and restore the normal pelvic anatomy. Unfortunately, if the deformity persists, an osteotomy is required prior to performing the external rotation (Figs. 22.12 and 22.13).7 However, in most cases ramus fractures do not require fixation whether there is an isolated anterior injury or a combined anterior and posterior injury. In cases where there is greater than 15 mm of displacement of the rami fracture associated with a posterior injury, the very strong pectineal fascia may be disrupted, and therefore ORIF of the fracture is indicated.10 In external rotation deformities or open-book pelvic injuries, the indication for surgery is diastasis of the pubic symphysis of 2.5 cm or more. Widening of less than 2.5 cm may require surgical fixation if there is an associated posterior injury. Disruptions of the posterior sacroiliac ligaments of the pelvis begin to occur with more than 2.5 cm of displacement. There are pelvic injuries that appear as simple symphysis diastasis that actually include a complete disruption of the posterior part of the pelvis. In these injuries, reduction of the diastasis with an anterior external fixation frame will widen the posterior complex and demonstrate posterior instability (Fig. 22.14).

The majority of pelvic injuries that require operative treatment are those that have complete instability of the hemipelvis. This may occur through the sacroiliac joint, or with a combination fracture-dislocation involving either the sacrum or the iliac wing (crescent fracture). Alternatively, injuries can involve just the sacrum or just the iliac wing posteriorly. Instability is determined by a combination of physical examination and radiographic analysis. The radiographic signs of instability were defined in the classification section above and include greater than 5 mm of displacement of the sacroiliac joint and/or a fracture gap rather than a fracture impaction. Additionally, a mobile hemipelvis during physical examination is an indication for surgical treatment. The surgical treatment of a pelvis fracture involves three steps: the approach, the reduction, and the fixation. In high-energy pelvic injuries, patients can have significant associated morbidity. While performing acute stabilization of the pelvis, orthopaedic surgeons have the ability to control the reduction and prevent complications. A thorough understanding of the anatomy of the pelvis, as well as the deformity of the fracture, will optimize these two areas of control.

Surviving the Night

A complete description of the acute management of pelvic injuries is beyond the scope of this chapter, but a few helpful hints can be suggested. Management of acute pelvic trauma requires a team approach. Fortunately, more than 90% of the pelvic injuries are hemodynamically stable. The patient with a mechanically unstable pelvis with a systolic blood pressure < 90 mmHg requires emergent resuscitation. Those patients with stable vital signs and a mechanically unstable pelvis need to be monitored closely to detect possible decompensation. The orthopaedic surgeon′s role in the initial management of a patient with a mechanically unstable pelvis is to stabilize the pelvis. Using a sheet with a towel clamp or a pelvic binder around the greater trochanter in the emergency room stabilizes the pelvis injury. The sheet or binder can be raised or lowered slightly depending on whether the general surgeon needs access to the belly or the angiographer needs access to the groin. Often gentle traction with internal rotation of the foot reduces the pelvis prior to sheeting or binding of the pelvis. However, the goal of stabilization of the pelvis is splinting and controlling the clot (> 20 L of fluid can leak into the retroperitoneal space in a pelvic injury),11 not reducing the pelvic volume.6 The sheet or binder can remain in place during the transfer of the patient to a level-1 center. Skin pressure ulcers can occur so checking the skin 8 hours after the application of the device is indicated, and if the patient′s blood pressure tolerates it, releasing the tension every 2 hours for a few minutes enables reperfusion of the skin. If the patient goes to surgery for another reason, an external fixation device is indicated with reduction of the posterior ring emphasized (see Posterior Ring Injuries, below).6

In general, most community hospitals do not have angiographers for embolization of arterial injuries if hemodynamic stability is not obtained after the sheet or binder; therefore, immediate transfer to a level-1 center is indicated after a sheet or binder is placed. Keeping the patient warm, well resuscitated, oxygenated, and transfusing whole blood or 1:1 ratio of packed red blood cells (PRBCs), platelets (PLTs), fresh frozen plasma (FFP), and cryoprecipitate can prevent the nearly 30% incidence of coagulopathy from becoming fatal.

Unstable pelvic injuries can entail neurologic injuries involving L2 to S4 nerve roots, with the most common injury occurring at L5 or S1. A deteriorating neurologic exam requires emergent decompression of the nerves or transfer to a higher level of care.

Urethral injuries and intra- and extraperitoneal bladder ruptures are common associated urologic injuries. Blood at the meatus and a high-riding prostate can be physical signs of a urologic injury. A retrograde urethrogram is indicated for all anterior pelvic injuries but can wait until hemodynamic stability is achieved. Otherwise, a bladder rupture can send dye throughout the pelvis, making embolization of arterial bleeders much more difficult. Although a Foley catheter is preferred, if a suprapubic catheter is placed, have the urologist tunnel from above to protect the skin around the symphysis for possible ORIF.

Open fractures of the pelvis have a high mortality rate and must be diagnosed with a vaginal and rectal exam to start early antibiotics. Open pelvic fractures require thorough debridement just like any other open fracture, meaning debridement of the entire hematoma. A transverse colon colostomy as opposed to a descending colon colostomy is indicated whenever the fecal stream contacts the open wound and allows the colostomy to exit away from the site of possible incisions to be used later for fixation of the pelvis.

Anterior Ring Injuries

Video 22.1 ORIF Pubic Symphysis Iliosacral Screw Placement

Pubic Symphysis Diastasis

As already mentioned, symphysis pubis displacement of greater than 2.5 cm is an indication for surgical treatment. The method of fixation can be either an external fixator or an internal fixation with a plate. External fixation can be successful but is associated with the risk that a missed posterior disruption will lead to a posterior pelvic deformity (Fig. 22.14). Another problem with external fixation is pin tract infections and skin necrosis in obese patients. Finally, patient acceptance of external fixation is not good. The use of an internal (subcutaneous) anterior fixator may alleviate some of the pin-tract complications and be better tolerated by the patient.12 External fixation can be implemented with either an anterior or a posterior frame. As mentioned earlier, placement of most external fixators occurs in the acute setting to stabilize the hemipelvis in a hemodynamically unstable patient (systolic blood pressure less than 90 mmHg) who has a mechanically unstable fracture. The technique for placing an anterior and a posterior frame will be described. Placement of the anterior frame is safer, and most orthopaedic surgeons are more comfortable with the anterior technique. However, an anterior external fixator may not provide adequate support in a completely unstable pelvic fracture. In general, a four-pin external fixator is used. Understanding the deformity can enable the surgeon to better place the incisions for the pin placement. For example, if there is an external rotation deformity, the surgeon should place the incision medial to the iliac crest to reduce tenting of the skin with the pins following reduction. The gluteus medius tubercle is the ideal placement for the anterior pins.

Techniques

Iliac Crest Fixator

A stab incision is made 2.0 to 2.5 cm posterior to the ASIS. This incision is taken down to the crest of the iliac wing. Laterally, the iliac wing often has a shelf. However, medially or internally the iliac wing is confluent with the crest. Therefore, placing a Kirschner wire (K-wire) along the inner cortex helps define the angle of the gluteus medius tubercle and helps the surgeon place a longer fixator pin within the bone. The author′s preference for pin placement is two pins separated ~ 4 cm. Initially, a pilot drill hole is placed through the cortex on the top of the iliac crest. A Schanz pin is then placed into the drill hole and driven between the two tables of cortical bone in the iliac wing. If the pin exits the pelvis, it still has a good bicortical bite. The other pin is placed using the same technique. A common mistake is to place the pin perpendicular to the patient′s torso instead of in the direction of the gluteus medius tubercle (~ 60 degrees from the perpendicular distally and ~ 30 degrees medially). After two pins are placed on each side, they are attached to each other with a bar. The two bars attached to the iliac wing are manipulated to obtain a reduction. These two bars are then attached to a third bar once reduction is obtained. In the acute setting in a hemodynamically unstable patient, the surgeon must understand the vectors required to obtain a reduced pelvis.6 Frequently, in completely unstable pelvis injuries, reduction of the posterior pelvis is important in controlling bleeding and obtaining hemodynamic stability. A combination of traction either in full extension or with hip flexion to approximately 45 degrees along with compression in the posterior part of the pelvis usually accomplishes a very acceptable reduction of the hemipelvis. A frequent mistake occurs when surgeons try to compress the diastasis anteriorly, causing a flexion internal rotation deformity of the hemipelvis, often opening up the posterior part of the pelvis (Fig. 22.14).

In the acute setting, stabilization and reduction of the posterior part of the pelvis are more important than decreasing the volume of the pelvis.11 Once the reduction is performed, tightening of the external fixator clamps enables the surgeon to obtain relative stability of the hemipelvis. The skin is released around the pins, preventing later maceration and infection, and a second level of bars is added for stability.

Supra-Acetabular Fixator

Alternatively, a two-pin fixation can be used with the pins placed in the supra-acetabular region of the pelvis.12 The incision is made over the AIIS and an outlet-obturator oblique fluoroscopy view can identify the column of bone above the acetabulum, between the inner and outer iliac cortices, where the pin tract will be placed. An iliac oblique can help identify the length of pins required. These pins yield excellent purchase in the supra-acetabular bone and can be incorporated into an anterior frame or used bilaterally to compress the posterior injury. The crossbar can be tunneled under the skin (InFix technique12 [Spinal Concepts Inc., Reading PA]) with the pins cut below the skin so the whole fixator is subcutaneous to prevent pin-tract infections. One disadvantage of the two-pin technique is that an adduction-abduction rotational deformity is harder to correct with a single pin on each side of the pelvis.

Posterior Fixator

The posterior external fixation frame (C-clamp) is used for the same indications as the anterior fixator, with the additional advantage of posterior stabilization. The contraindication for placement of the posterior clamp is an iliac wing fracture anterior to the sacroiliac joint because compression of the joint will not help the reduction of the iliac wing fracture. Comminution of the sacrum requires special consideration because overcompression can be harmful to the patient. The technique for placement of the posterior clamp is as follows. With the patient in the supine position, an imaginary line is drawn from the ASIS to the posterior superior iliac spine (PSIS) along the side of the patient. This line is divided into thirds, and a longitudinal stab incision is made at the interval between the posterior third and the middle third (Fig. 22.15). This site should be roughly in line with the greater trochanter of the femur. A long clamp is then introduced through the stab wound down to the bone. The bone is palpated with the clamp, and the flare of the iliac wing is located. This flare is at the level of the anterior end of the sacroiliac joint; thus, pin insertion anterior to this risks penetration of the peritoneal cavity if the pin traverses the ilium. Immediately posterior to the flare is the area where the pin should be placed. This corresponds to the area of the iliac wing that is just lateral to the sacroiliac joint. Once this area is determined, a pin is placed on both sides and hammered into the iliac wing. A clamp is then placed over the pins, and the surgeon manually compresses the clamp to fit snugly against the pins. The clamp has a cannulated, threaded bolt that slides over the pins and is tightened with a wrench, providing additional compression of the posterior pelvic injury. Traction is helpful in reducing the completely unstable pelvic injury prior to initiating compression (Fig. 22.16).

As mentioned, overcompression is a potential complication, and therefore radiographic evaluation is required following application of the frame. One concern is that the posterior pins of the C-clamp may lead to a subsequent infection when iliosacral screws are placed for the definitive treatment of the posterior pelvic injury. In my series of more than 20 staged cases using the above protocol, there have been no secondary infections of the iliosacral screws. However, the concern remains.

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