The pelvic bone is made up of two innominate bones, each made of three separate bones that ossify to become one - the ilium, ischium, and pubis. These bones form a ring and connect posteriorly at the sacrum to form the sacroiliac (SI) joint. Anteriorly is the pubic symphysis. It is important to understand this pelvis as a ring concept, because when fractures occur in the pelvis, the often occur in pairs, as it is impossible to break a solid ring in only one place. The classic comparison is to think about a pretzel. Next time your eating lunch, give it a try.
Pelvic fractures are difficult to diagnose because there is not always an obvious sign of an injury, and can be life threatening if not diagnosed quickly. It is important to have a high index of suspicion if the mechanism of injury is blunt trauma. This is the main reason that the AP pelvis is included in the trauma evaluation with the AP chest. For more on reading an AP pelvis, see one of my previous posts.
There are two common injury patters in high energy pelvic fractures: the anterior-posterior compression injury and the lateral compression type injuries. There can also be vertical sheer injuries and combination type injuries.
In this post, I will discuss the APC type injury (D-F in the image below), and will cover the lateral compression and vertical sheer injuries (A-C, G in the image below) in the next post. The image below is a depiction of the Young-Burgess classification system, the most common classification of pelvic ring injuries. Other classification systems (which I will not discuss) include the Tile and OTA classification systems.
On initial AP pelvis evaluation, APC injuries are suggested with widening or diastasis of the symphysis pubis or in the setting of vertical fractures through the rami. On an adequate AP pelvis, there should be no more than 4-5mm (may be up to 9mm in the setting of pregnancy) between the right and left innominate bones at the symphysis pubis. This injury should always be considered in the case of hemodynamic instability with no other obvious etiology. In order to completely understand the pathology of pelvic fractures, we need to first discuss pelvic ligaments.
In considering pelvic stability, there are five main stabilizing ligaments to consider: the symphysis, the sacrospinus ligament, the sacrotuberous ligament and the anterior and posterior sacroiliac ligaments. This ligament complex is quite strong, hence the high energy trauma required to disrupt them. Rotational stability is provided to the pelvis by the short posterior sacroiliac, the anterior sacroiliac, iliolumbar and sacrospinous ligaments. Vertical stability is provided to the pelvis by the long posterior sacroiliac, sacrotuberous and lateral lumbosacral ligaments.
APC I - In this injury pattern, the symphsis pubis is less than 2.5cm and vertical fractures of the rami may be noted on the APC pelvis. The posterior ligaments are intact.
APC II - In this injury pattern, there is greater than 2.5cm of diastasis of the pubic symphysis. This results from disruption of the ligaments that stabilize the symphysis. One may also note widening of the SI joint due to disruption of the sacrotuberous and sacrospinous ligaments. This is the classic open-book injury. While rotational instability is noted in this injury pattern, there is no vertical instability in this injury pattern.
APC III - In this injury pattern, there is complete disruption of the stabilizing ligaments, including the symphysis, sacrotuberous, sacrospinous and sacroiliac ligaments. This is a very unstable injury pattern and is the pattern most often associated with neurovascular injury.
As stated earlier, in the appropriate setting, it is important to have a high index of suspicion for this injury. Given that this is an injury that should never be missed with potential serious morbidity and even mortality, I have been taught by my seniors to make a habit of looking at the AP pelvis before entering the trauma bay. When these injuries are identified, they should be taken seriously and addressed promptly. Fluid resuscitation should be started, especially in the setting of hemodynamic instability, and blood products should be readily available. One of the easiest ways to stabilize APC type injuries (and often have a noticeable impact on vital signs) is to use a standard sheet folded and then wrapped around the pelvis at the level of the trochanters. The sheet can be fixed anteriorly with some Kocher clamps. There are commercially available products as well.
Treatment of these injuries depends on the pattern of injury and the hemodynamic status of the patient. In the setting of hemodynamic instability, a combination of external fixation and intravascular intervention can be used to correct vital signs emergently. Bleeding can be venous or arterial. Depending on the injury pattern, up to 15 units of blood may be needed to replace losses. There is a good recent article in the JAAOS detailing treatment of pelvic fractures in the setting of hemodynamic instability.
Once the patient has been stabilized and other life threatening injuries have been addressed, these injuries can be stabilized internally with plates and screws. Anterior injury patterns can be treated with external fixation alone but posterior injuries require internal fixation.
A note about coagulopathy. In the setting of pelvic fractures, venous thrombus formation is common. Because of this, anticoagulation is essential to prevent embolism and potentially life-threatening complications. At our center, we anticoagulate patients for 6 weeks after their fixation. When anticoagulation is not possible, prompt placement of an IVC filter is essential.
Sources for this article include Handbook of Fractures by Koval and the AAOS Comprehensive Orthopaedic Review. Images were taken from the AAOS Comprehensive Review.
Pelvic fractures are difficult to diagnose because there is not always an obvious sign of an injury, and can be life threatening if not diagnosed quickly. It is important to have a high index of suspicion if the mechanism of injury is blunt trauma. This is the main reason that the AP pelvis is included in the trauma evaluation with the AP chest. For more on reading an AP pelvis, see one of my previous posts.
There are two common injury patters in high energy pelvic fractures: the anterior-posterior compression injury and the lateral compression type injuries. There can also be vertical sheer injuries and combination type injuries.
In this post, I will discuss the APC type injury (D-F in the image below), and will cover the lateral compression and vertical sheer injuries (A-C, G in the image below) in the next post. The image below is a depiction of the Young-Burgess classification system, the most common classification of pelvic ring injuries. Other classification systems (which I will not discuss) include the Tile and OTA classification systems.
On initial AP pelvis evaluation, APC injuries are suggested with widening or diastasis of the symphysis pubis or in the setting of vertical fractures through the rami. On an adequate AP pelvis, there should be no more than 4-5mm (may be up to 9mm in the setting of pregnancy) between the right and left innominate bones at the symphysis pubis. This injury should always be considered in the case of hemodynamic instability with no other obvious etiology. In order to completely understand the pathology of pelvic fractures, we need to first discuss pelvic ligaments.
In considering pelvic stability, there are five main stabilizing ligaments to consider: the symphysis, the sacrospinus ligament, the sacrotuberous ligament and the anterior and posterior sacroiliac ligaments. This ligament complex is quite strong, hence the high energy trauma required to disrupt them. Rotational stability is provided to the pelvis by the short posterior sacroiliac, the anterior sacroiliac, iliolumbar and sacrospinous ligaments. Vertical stability is provided to the pelvis by the long posterior sacroiliac, sacrotuberous and lateral lumbosacral ligaments.APC I - In this injury pattern, the symphsis pubis is less than 2.5cm and vertical fractures of the rami may be noted on the APC pelvis. The posterior ligaments are intact.
APC II - In this injury pattern, there is greater than 2.5cm of diastasis of the pubic symphysis. This results from disruption of the ligaments that stabilize the symphysis. One may also note widening of the SI joint due to disruption of the sacrotuberous and sacrospinous ligaments. This is the classic open-book injury. While rotational instability is noted in this injury pattern, there is no vertical instability in this injury pattern.
APC III - In this injury pattern, there is complete disruption of the stabilizing ligaments, including the symphysis, sacrotuberous, sacrospinous and sacroiliac ligaments. This is a very unstable injury pattern and is the pattern most often associated with neurovascular injury.
As stated earlier, in the appropriate setting, it is important to have a high index of suspicion for this injury. Given that this is an injury that should never be missed with potential serious morbidity and even mortality, I have been taught by my seniors to make a habit of looking at the AP pelvis before entering the trauma bay. When these injuries are identified, they should be taken seriously and addressed promptly. Fluid resuscitation should be started, especially in the setting of hemodynamic instability, and blood products should be readily available. One of the easiest ways to stabilize APC type injuries (and often have a noticeable impact on vital signs) is to use a standard sheet folded and then wrapped around the pelvis at the level of the trochanters. The sheet can be fixed anteriorly with some Kocher clamps. There are commercially available products as well.
Treatment of these injuries depends on the pattern of injury and the hemodynamic status of the patient. In the setting of hemodynamic instability, a combination of external fixation and intravascular intervention can be used to correct vital signs emergently. Bleeding can be venous or arterial. Depending on the injury pattern, up to 15 units of blood may be needed to replace losses. There is a good recent article in the JAAOS detailing treatment of pelvic fractures in the setting of hemodynamic instability.
Once the patient has been stabilized and other life threatening injuries have been addressed, these injuries can be stabilized internally with plates and screws. Anterior injury patterns can be treated with external fixation alone but posterior injuries require internal fixation.
A note about coagulopathy. In the setting of pelvic fractures, venous thrombus formation is common. Because of this, anticoagulation is essential to prevent embolism and potentially life-threatening complications. At our center, we anticoagulate patients for 6 weeks after their fixation. When anticoagulation is not possible, prompt placement of an IVC filter is essential.
Sources for this article include Handbook of Fractures by Koval and the AAOS Comprehensive Orthopaedic Review. Images were taken from the AAOS Comprehensive Review.
Love your blog! I'm an MS4 applying in ortho and was so excited to find an ortho blog, especially one with such great educational content. Pelvic fractures have always been tough for me to conceptualize and this is really helpful.
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