Pelvis and Sacrum


Anatomy and Function

  • The anatomy of the pelvis consists of the right and left innominate bones, the sacrum, and the coccyx.
  • The innominate bone consists of the schism, pubis, and ilium.
  • The sacrum lies between the two innominate bones forming the SI joints posteriorly. The innominate bones join together anteriorly at the symphysis pubis.
  • The acetabulum is a deep, cup-shaped indentation in the lateral aspect of the innominate bone. It is made up of the ilium superiorly, the ischium inferolaterally and the pubis anterosuperiorly.
  • Vascular supply consists of branches of the internal iliac artery, median sacral artery, and the superior rectal artery.
  • The neurologic anatomy consists of the sacral nerve roots within the sacrum and the lumbosacral plexus surrounded by the pelvic ring.
  • The function of the pelvis is to distribute weight of the trunk to the lower extremities while standing, and to the ischial tuberosity while seated.
  • The pelvis aids in protection of the sigmoid colon and the genitourinary organs including the bladder, the distal ureters, the urethra, and the male and female reproductive organs.
  • Figure Anatomy of the pelvis

    Anatomy of the Pelvis

    Table Tile classification system
    Type A: Stable pelvic ring Injury
    A1: Avulsion fracture of the innominate bone
    A2: Stable iliac wing fractures or stable minimally displaced ring fractures
    A3: Transverse fracture of coccyx and sacrum
    Type B: Partially stable pelvic ring injury (rotationally unstable, vertically stable)
    B1: Open book injury (unilateral)
    B2: Lateral compression injury
    B3: Bilateral type B injuries
    Type C: Unstable pelvic ring injury (vertical sheer, rotationally and vertically unstable)
    C1: Unilateral
    C2: Bilateral, one side type B, one side type C
    C3: Bilateral type C lesions

Trauma

  • Pelvic trauma accounts for 3% of all orthopedic trauma.
  • Mechanism of injury is either low or high energy in nature.
  • Low energy fractures include domestic falls, straddle injuries, avulsion fractures, and low velocity vehicular injuries. These mechanisms usually result in isolated fractures of individual bones and do not disrupt the pelvic ring.
  • High energy fractures result in pelvic ring disruptions. Mechanisms include motor vehicle accidents (57%), pedestrian vs. auto (18%), motorcycle (9%), falls from heights (9%) and crush injury (4%) (J Trauma 29:981-1002, 1989).

Classification System

  • The ideal classification system would allow the clinician to identify associated injuries and their complications, help formulate a treatment plan and predict morbidity and mortality.
  • Several classification systems exist for pelvic fractures, however the Emergencies of orthopedic, Orthopedic Trauma Association and the OA group uses the Tile classification.
  • The Tile system is based on the direction of force applied to the pelvis ring including lateral compression (LC), anteroposterior compression (APC), vertical sheer (VS), and combined mechanical injury (CM). It is further divided into radiographic evidence of stability or instability. Young expanded this classification by subdividing the LC and APC fractures based on the amount of ring disruption as viewed by three pelvic radiographic views.

Management

Prehospital Care

  • If the patient is unstable or there are prolongued transport times, pneumatic antishock garments (PASG) should be applied if available. Spinal immobilization with c-collar and backboard are essential.

ABCs

  • As with all patients, the patient’s airway, breathing and circulation are first to be evaluated.
  • Specific attention to hemodynamic stability is important since certain pelvic fractures can lead to hemorrhagic shock.
  • IV sites in the lower extremity should be avoided if a pelvic fracture is suspected. In the event that the patient is unstable, crystalloid fluids (either normal saline or lactated Ringers) should be used.
  • Use of blood products should be initiated early in the resuscitation phase if the patient is hypotensive and a severe pelvic fracture is suspected.

History

  • When time permits, a detailed history from witnesses, the patient, or ambulance personnel must be obtained.
  • Details of the mechanism of injury, direction of force, amount of force, and associated injuries are pertinent.
  • Ask the patient if they have pain with movement, ambulation, sitting, standing, or defecating.
  • Attention to associated injuries is crucial (is patient able to void, are they pregnant, do they have any motor or sensory deficits etc.).
Physical Exam

  • As part of the secondary survey, inspect for swelling, ecchymosis, and tenderness over the hip, groin, and lower back.
  • Note deformity or asymmetry in the lower extremities.
  • Examine the anterior-superior iliac spine by pressing medially and then laterally to check for internal and external rotation of the pelvis respectively. Checking for vertical and rotational deformity should be performed only once and by the most experienced physician as this examination may dislodge blood clots and result in hemorrhage and rapid decompensation.
  • Examine the skin to verify open versus closed fractures. It is essential to perform digital and perinealexaminations. Assess for continuity of the anus and rectum, condition of the prostate and for fresh blood.
  • Check for blood at the opening of the urethra and in the female for continuity and lacerations of the vagina.
  • If the pelvis is unstable, detailed exams with an anoscope and speculum should be postponed until stabilization is possible.
  • A detailed vascular and neurologic exam should be performed.

    Radiography

    • Plain films of the pelvis should be ordered when the patient is symptomatic or if the patient is not assessable. An AP view should be ordered early. Additional plain film views or CT scan of the pelvis, if the patient is stable, should be ordered to determine the type of fracture.
    • Plain films
    • AP pelvis view should be the initial film ordered for any pelvic trauma. Most significant fractures will be seen on this view; however it does not demonstrate the degree of bony displacement well. The pubic symphysis should be no more than 5 mm wide with < 2 mm offset of left and right pubic rami. The SI joint should be no >2-4 mm wide.
    • Inlet view (30° caudal view) provides visualization of the posterior arch, widening of the SI joint, and displacement of the anterior arch.
    • Outlet view (30° cephalic view) allows visualization of cephalad or vertical displacement of the hemipelvis, nondisplaced sacral fractures and SI joint widening.
    • Computed tomography
    • CT is useful for delineating pelvic fractures that may be missed on plain radiographs and for elucidating associated complications including retroperitoneal hematomas. Studies have shown that CT scanning is superior for demonstrating acetabular fractures and posterior arch disruptions. It is important to remember that only the hemodynamically stable patient is a candidate for CT scanning.
    • MRI
    • MRI may be useful for neurologic and vascular injury and to delineate genitourinary complications. Its role in initial evaluation of an acute fracture is limited due to prolonged time for evaluation and availability.

      Labs

      • Type and crossmatch, serial hemoglobin and hematocrit, platelets, and PT/PTT should be ordered on all patients with severe pelvic fractures.

        Other Studies

        • High energy fractures have a high association with nonorthopedic injuries. In one study of patients with high energy pelvic fractures, 47% had associated abdominal injury (J Trauma 23:535, 1983.).
        • A diagnostic peritoneal lavage (DPL) or an ultrasound FAST exam should be performed.
        • If the DPL aspirate or the FAST exam is postive, a laparotomy is warranted.
        • If the DPL cell count is positive, an external fixator should be applied and the patient taken for laparotomy.
        • If the cell count is negative and the patient is a candidate for external fixation, then one should be applied.
        • If the patient remains hemodynamically unstable in any case, then angiography and selective embolization is necessary.

        Complications

        Hemorrhage

        • Hemorrhage is the leading cause of death in patients with pelvic fractures.
        • 20% of hemorrhages are due to disruption of the iliac and femoral vessels and the remaining occur from venous, marrow or small vessel disruption.
        • The fractures that are most likely to place patients at risk for hemorrhage are Tile’s
          Type B1 fractures (open book injury/sprung pelvis), any open fracture, or those that meet Cryer’s criterion. Cryer et al noted that a gap or displacement of 0.5 cm or more at any fracture site in the pelvic ring or acetabulum as seen on the AP pelvis plain film view had a high correlation with significant hemorrhage.
        • It is essential that the ED physician recognize and evaluate those fractures that place the patient at high risk for retroperitoneal hematomas and associated abdominal visceral injury.
        • Resuscitation and stabilization is paramount until definitive therapy can be assured.

        Genitourinary Complications

        • Rupture of the bladder and posterior urethra occurs in approximately 5% of patients with pelvic injury.
        • Blood at the meatus, a high riding prostate, laceration of the vagina, or inability to void are all correlated with GU injury.
        • Fractures associated with GU injuries include Tile’s Type B2 (subluxation of the pubic symphysis and bucket-handle fractures), Type B1 (open book injury), Type C (Malgaigne fracture), and straddle fractures.
        • Microscopic hematuria alone does not mandate cystography or urethrography.
        • Clinical suspicion of urethral injury or gross hematuria requires further evaluation including a combination of urethrogram, intravenous pyelography, cystography, and CT scan.

        Neurologic Injury

        • A complete neurologic exam, including motor, sensation and deep tendon reflexes, is critical when pelvic injury is suspected.
        • Fractures associated with neurologic injury include sacral and acetabular fractures.
        • Neurologic injury is found in 22% of vertical sacral fractures and horizontal sacral fractures at or above the S3 level.
        • Acetabular fractures are associated with sciatic nerve injury.
        • Stabilization of the fracture is essential.
        • Neurosurgical or orthopedic consultation is required.

        Orthopedic Injury
        Orthopedic consultation for surgical fixation is required in all patients that have a double break in the pelvic ring, who do not meet Cyer’s Criterion, and who are hemodynamically stable. Gynecologic Injury Vaginal bleeding or uterine bleeding may result from lacerations secondary to open fractures or, in the gravid uterus, abruptio placentae or uterine perforation. Fallopian tube or ovarian damage is less likely, but can occur. If any gynecological injury is suspected, gynecological consultation is required. Uncomplicated Fractures These fractures are simple, involve only a single break in the pelvic ring, are not associated with secondary injuries, and do not require orthopedic repair. Fractures that are considered uncomplicated include Tile’s Type A1, A2 and A3 fractures (ASIS avulsion, AIIS avulsion, ischial tuberosity avulsion, ischial body fractures, iliac wing fractures, and coccyx fractures). Uncomplicated fractures require bed rest and analgesia and can be managed as an outpatient.

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