A pelvic fracture involves damage to the hip bones, sacrum, or coccyx - the bony structures forming the pelvic ring. Due to the inherent structural and mechanical integrity of this ring, the pelvis is a highly stable structure. Therefore, fractures of the pelvis occur most commonly in the setting of a high-impact trauma and are often associated with additional fractures or injuries elsewhere in the body. 
Though high-impact injuries are more commonly associated with pelvic fractures, they can occur in the setting of a low-impact injury as well. Low impact injuries are seen more frequently in adolescents and the elderly - in adolescents, typically as a result of athletic injuries (e.g. avulsion fractures of superior or inferior iliac spines or apophyseal avulsion fracture of the iliac wing or ischial tuberosity), and in the elderly as a result of falls while ambulating (e.g. stable fractures of the pelvic ring or insufficiency fractures of sacrum and anterior pelvic ring). 
High impact injuries occur most commonly in the setting of motor vehicle accidents (e.g., vehicle collision or pedestrians struck) or fall from a significant height.
In the United States, it is estimated that pelvic fractures occur in 37 out of 100,000 individuals per year, the incidence being highest in those between the ages of 15 and 28 years. Under the age of 35, men are more commonly affected, while over 35, women are more commonly affected.
The bony pelvis, comprised of the ilium (iliac wings), ischium, and pubis, forms an anatomic ring with the sacrum. Due to the amount of force that is required to fracture this ring, a fracture in one part of the pelvis is frequently accompanied by a fracture or damage to ligaments or structures within or outside of the pelvis.
There are two main classification systems used to describe pelvic fractures - Tile (based on the integrity of the posterior sacroiliac complex) and Young (based on the mechanism of injury).
The Tile classification system: developed by Pennal and Tile, divides injuries into lateral compression (LC), anteroposterior compression (APC) or vertical shear (VS) injuries. This classification system also takes into consideration radiographic signs of pelvic stability or instability.
Type A - The sacroiliac complex remains intact, and the pelvic ring contains a stable fracture (often managed inoperatively).A1 - avulsion fracturesA2 - stable iliac wing fracture or minimally displaced pelvic ring fractureA3 - transverse sacral or coccyx fracture
Type B - Partial disruption of the posterior sacroiliac complex - caused by external or internal rotational forces (rotationally unstable and vertically stable).B1 - open-book injuryB2 - LC injuryB3 - bilateral type-B injury
Type C - Complete disruption of the posterior sacroiliac complex (both rotationally and vertically unstable) often as a result of intense force (e.g. motor vehicle accident, fall from a height or severe compression injury). C1 - unilateral injuryC2 - bilateral injury (one side is a type B, and the other is a type C)C3 - bilateral injury (both sides type C)
The Young classification system: developed by Young and Burgess, expanded on Tile’s classification by including combined fractures (as many pelvic fractures occur as a combination of forces in multiple directions).
The most common combination fracture is LC/VS. LC fractures involve transverse fractures of the pubic rami (either ipsilaterally or contralaterally to the posterior injury). VS fractures involve symphyseal diastasis or vertical displacement (either anteriorly or posteriorly - usually through the SI joint, or less commonly through the iliac wing or sacrum).
Grade III (open book)
Both stable and unstable pelvis fractures can additionally be divided into open or closed fractures - depending on whether or not there is breakage of the skin by fragments of bone respectively. Open fractures, when the skin is broken, poses an additional risk of infection - both in the wound and in the bone itself.
Due to the considerable blood supply of the pelvis, fractures in this region are also often associated with significant hemorrhage.
A pelvic fracture should be considered in all patients that have experienced any significant amount of blunt trauma or fall - especially if palpation of the bony pelvis elicits tenderness, laxity, or instability. A fracture to the pelvis is almost always painful - aggravated by movement of the hip or attempting to walk. Patients will usually try to keep their hips or knees flexed to avoid such aggravation. There may also be swelling or bruising noted in the injured area. Manual palpation may reveal crepitus while compression along the iliac crest can help determine the level of pelvic stability - instability defined as the inability to resist deformation caused by a physiological load. It is important to note that in pregnant females, what may appear as pelvic instability, may be the natural stretching of pelvic ligaments associated with pregnancy.
As most pelvic fractures occur in the setting of trauma, all patients should undergo routine assessment as described by the American College of Surgeons (e.g., as per the Advanced Trauma Life Support protocol) which includes evaluation for any potentially life-threatening injuries (whether related to the hip or not).
Assessment of soft-tissue injuries may provide further insight to the degree of impact sustained by the patient. It is particularly important to assess for any lacerations of the perineum (e.g., rectum or vagina) as this would indicate a severe injury and fractures potentially contaminated by urine, stool, or other environmental contaminants.
Pelvic ring fractures are also commonly associated with injuries to the axial or appendicular spine. Therefore, the spine and extremities should also be examined (e.g., limb length discrepancies, internal/external rotational deformities).
Neurovascular structures crossing the pelvis may also be involved with injuries to the pelvis - generally as a result of a laceration to venous structures (and less commonly arterial structures). This is important to consider as hemorrhage, in either case, is considered a medical emergency.
Neurologic injuries associated with pelvic fractures typically involve the L5 or S1 nerve roots. If there is a sacral fracture involved, this may also include an S2-S5 sacral nerve root injury which could result in bowel or bladder incontinence and sexual dysfunction (e.g., may present with peripheral numbness or decreased rectal tone in the acute setting).
Computed tomography (CT) scans of the abdomen/pelvis will provide the best visualization of pelvic anatomy and allow for evaluation of any pelvic, retroperitoneal or intraperitoneal bleeding. A CT scan will also allow for confirmation of hip dislocation and help determine whether or not there is an associated acetabular fracture. 
The best screening test for a pelvic fracture, however, is an anteroposterior (AP) pelvic radiograph - this will reveal 90% of pelvic injuries. Although most trauma patients undergo routine CT scans to the abdomen and pelvis, AP pelvic radiograph should be considered (as a rapid diagnostic tool) for hemodynamically unstable patients, to allow for earlier intervention.
The pelvis should also be examined as part of the Focus Assessment with Sonography for Trauma (FAST) examination - this may help identify intraperitoneal bleeding (potentially pinpointing a source of shock) if it is present.
Retrograde urethrography should also be performed in patients suspected of having a urethral tear (e.g., males presenting with blood at the urethral meatus or females whom, after careful attempts, are unable to have a Foley catheter inserted, or have a vaginal tear or palpable fragments adjacent to the urethra).
Individuals presenting with hematuria in the setting of an intact urethra (e.g., suspected of having a urinary bladder injury) should undergo a cystography.
Pelvic Angiography may be performed if a patient is experiencing persistent hemorrhage despite adequate intravenous fluid resuscitation and pelvic stabilization - this may detect occult or obvious injuries and allow for embolization of any damaged arteries in addition to helping visualize before manipulative reduction.
In the acute setting, any additional life-threatening injuries should be addressed - the amount of force needed to result in a pelvic fracture will likely have caused other significant injuries. Mechanical stabilization (e.g., with an external compression device) will help to control hemorrhage from the fractured site(s). The primary goal in the acute setting is to provide early stable fixation as it has been associated with decreased blood transfusion, systemic complications, hospital stay, and overall improved survival. Excessive movement of the pelvis should also be avoided. Large-bore intravenous access for administration of analgesics and fluids should be obtained as soon as possible, and vital signs should be monitored closely. 
Modern improvements in pelvic implants, anesthetic techniques, intraoperative imaging, coordinated care in polytrauma along with a more advanced understanding of injury patterns have resulted in a shift towards the more operative management of pelvic fractures that were once previously treated nonoperatively. This has shown improved clinical outcomes as a result of prevention and repair of any significant pelvic defects and earlier mobilization of patients.
Nonsurgical treatments of pelvic fractures (for stable fractures in which the bones are nondisplaced or minimally displaced) may include a walking aid (e.g., to avoid weight bearing on the affected side) or medications (e.g., analgesics, anticoagulants).
The exact surgical approach depends on the type of (unstable) fracture that is involved. This may include external fixation (e.g., to stabilize the pelvis with metal pins or screws inserted through small incision in the skin and muscle), skeletal traction (e.g. metal pins implanted in the thighbone or shinbone for positioning, with attached weights to pull on the leg and maintain broken bone fragments in a normal position) or open reduction and internal fixation (e.g. repositioning (reduction) of displaced bone fragments followed by fixation with screws or metal plates attached to the outer surface of the bone).
Even though the initial treatment of a pelvic fracture is led by a trauma team of surgeons, the postoperative care of these patients is in the hands of the nurses. A pharmacist should be involved to regulate and assist with pain relief. Pelvic fractures can result in a number of complications including hernias and muscle ruptures. About 10-20% of patients have neurological injuries, a high risk for deep vein thrombosis, postoperative wound infections, erectile dysfunction, and dyspareunia. The nurse is in a prime position to monitor and educate the patient and the family about these complications, time to recovery and long-term sequelae. Once the patient has stabilized, all these patients need a physical therapy consult to regain muscle strength and endurance. Follow up in outpatient clinics at 3-month intervals is necessary to determine the presence of any deficits in function. Some of these patients may be bedridden and may benefit from an outpatient nurse visit to check on progress. (Level III)
Outcomes after pelvic fracture have improved over the past 3 decades. The key is early stabilization which can result in decreased blood loss and shorter hospital stays. In addition, with early stabilization, there are fewer complications and better survival. However, with pelvic injuries associated with iliac wing or sacral fractures, posterior pelvic displacement, the outcomes are poor. Further, if there is a limb discrepancy of more than 2.5 cm, this also results in a poor outcome. A permanent neurological injury may be present in 20% of survivors. The mortality rate for pelvic fractures in patients who present with hypotension varies from 4-30%. Many of these patients also have other organ injuries which also increases morbidity and mortality. (Level V)