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Pelvic Ring Fracture - Ishcium and pubis

Author: Charbel Saade

Institute: Section Chief CT Radiographer - Royal Prince Alfred Hospital Sydney Australia

Patient Presentation

 

A 37 year old male patient presents to ER post MVA. The impact was at 120 km/hour. Car Vs Pole and the patient was the driver. On examination the patient presented with white clammy skin and extreme pain to the left grion region.

 

Anatomy

 

Pathophysiology:

 

Pelvis consists of the ilium (ie, iliac wings), ischium, and pubis, which form an anatomic ring with the sacrum. Disruption of this ring requires significant energy. Because of the forces involved, pelvic fractures frequently involve injury to organs contained within the bony pelvis. In addition, as the pelvis is supplied with a rich venous plexus as well as major arteries, fractures may produce significant bleeding.

The Young classification system incorporates anatomic mechanism of injury and identifies 4 types of ring disruption. Acetabular fractures, with or without ring disruption, also may occur. Falls in elderly persons may involve fracture (usually of the pubic rami) without disruption of the ring.

Lateral compression (LC) fractures involve transverse fractures of the pubic rami, either ipsilateral or contralateral to a posterior injury.

  1. Grade I - Associated sacral compression on side of impact
  2. Grade II - Associated crescent (iliac wing) fracture on side of impact
  3. Grade III - Associated contralateral "open book" injury

 

Anterior-posterior compression (APC) fractures involve symphyseal diastasis or longitudinal rami fractures.

  1. Grade I - Associated widening (slight) of pubic symphysis or of the anterior sacroiliac (SI) joint, while sacrotuberous, sacrospinous, and posterior SI ligaments remain intact
  2. Grade II - Associated widening of the anterior SI joint caused by disruption of the anterior SI, sacrotuberous, and sacrospinous ligaments, while posterior SI ligaments remain intact
  3. Grade III (open book) - Complete SI joint disruption with lateral displacement and disrupted anterior SI, sacrotuberous, sacrospinous, and posterior SI ligaments

 

Vertical shear (VS) involves symphyseal diastasis or vertical displacement anteriorly and posteriorly, which is usually through the SI joint, though occasionally through the iliac wing or sacrum.

 

Combined mechanical (CM) fractures involve a combination of these injury patterns, with LC/VS the most common.

 

Acetabular fractures most commonly involve disruption of the acetabular socket when the hip is driven backward in a motor vehicle accident. Occasionally, they will occur in a pedestrian struck by a vehicle moving at a significant rate of speed.

 

Mortality/Morbidity


With improvement in emergency management techniques, the morbidity and mortality rates of pelvic fracture have decreased in recent decades.

  1. The overall mortality rate in pelvic ring fractures is approximately 6%. Uncontrolled pelvic hemorrhage accounts for 39% of related deaths; head injury, 31%; and multiple organ failure, 30%. AP compression and vertical shear injuries have a higher incidence of pelvic vascular injury and hemorrhage.
  2. Associated injuries are commonly found as a result of the powerful forces necessary to fracture the pelvic ring. Injuries to the peripheral nerve, urethra, and bladder are directly attributable to pelvic ring fractures. The frequencies of associated injuries are as follows:
    1. Closed head injury - 51%
    2. Long bone fracture - 48%
    3. Peripheral nerve injury - 26%
    4. Thoracic injury - 20%
    5. Urethra (male) - 15%
    6. Bladder - 10%
    7. Spleen - 10%
    8. Liver - 7%
    9. GI tract - 7%
    10. Kidney - 7%
    11. Urethra (female) - 6%
    12. Mesentery - 4%
    13. Diaphragm - 2%
  3. Immediate complications may be observed.
    1. Pelvic hemorrhage is the most serious immediate complication of a pelvic ring fracture. Disruption of the osseous pelvic ring leads to disruption of pelvic veins and/or arteries in as many as 75% of patients.
      1. Venous bleeding can arise from the posterior pelvic veins (usually in the setting of sacral injury) or from the marrow space of broken pelvic bones.
      2. Arterial bleeding occurs as the result of direct injury to a vessel close to an osseous injury. The injured vessels are typically branches of the internal iliac artery.
      3. Posterior fractures, especially those through the greater sciatic notch, may injure the superior gluteal artery.
      4. Anterior fractures or disruptions may injure the internal pudendal artery.
      5. Pelvic hemorrhage is immediately treated by means of pelvic stabilization, either with sheets wrapped around the pelvis or with external fixator devices. In either case, the goal is to restore the normal anatomic relationships in the pelvis; this restoration serves to reduce the pelvic volume. The larger the pelvic volume, the greater the amount of bleeding that can occur. Uncontrollable hemorrhage requires angiographic evaluation and embolization of the bleeding vessels.
    2. Bladder injury occurs as either an associated injury or a complication of a pelvic ring fracture.
      1. Extraperitoneal bladder rupture occurs more commonly (in approximately 80% of patients) than intraperitoneal rupture (20%). Extraperitoneal rupture results either from direct bladder injury due to pelvic fracture fragments or from shearing forces near the base of the bladder.
      2. Intraperitoneal rupture is usually the result of blunt trauma to a distended bladder.
      3. Pelvic fractures need not be present in either type of bladder rupture, but they are more often associated with extraperitoneal injuries. Traditionally, the diagnosis of bladder injury was made by using conventional cystography; however, with the increased use of computed tomography (CT) scanning, CT cystography is now more routinely performed.
    3. Urethral injury results from the same shearing forces that lead to extraperitoneal bladder rupture. Distraction of the anterior pelvic osseous support structures leads to stretching of the urogenital diaphragm, the most common location for urethral injury. The male urethra is longer and more mobile than that in females; therefore, it is more prone to injury.
      1. In a type I urethral injury, the membranous urethra (above the urogenital diaphragm) is stretched and narrowed.
      2. In a type II injury, disruption of the membranous urethra occurs near the base of the bladder.
      3. In a type III injury, the disruption of the membranous urethra extends below the level of the urogenital diaphragm to involve the bulbous urethra.
    4. Nerve injury occurs as both an immediate and a late complication of pelvic ring fracture. Fractures of the sacrum or sacroiliac (SI) joints can injure the adjacent sacral plexus or sacral nerve roots. Fractures extending into the region of the greater sciatic notch may injure the sciatic nerve. Posterior acetabular fractures also are associated with sciatic nerve injury. Nerve dysfunction may persist even after reduction and fixation of the pelvic fracture.
  4. Early complications may occur.
    1. Blood loss in the preoperative and immediate postoperative period results in morbidity in several ways. Uncontrolled hemorrhage may result in exsanguination. Continued blood loss or inadequate volume repletion may result in shock and its clinical ramifications, such as coagulopathy and renal failure.
    2. Infection can occur in a number of settings. The pelvic hematoma that accompanies most significant pelvic fractures may transform into an abscess. Open drainage or, if possible, percutaneous drainage is required. Patients undergoing open surgical fixation of a pelvic fracture are at risk for wound infection. Of course, all postsurgical patients are susceptible to a variety of infections, most notably those of the pulmonary system and urinary tract. Fixation devices, either external or internal, may become infected and require removal.
    3. Thromboembolic disease is frequently encountered in the setting of pelvic fracture. The potential for coagulopathy coupled with a guaranteed temporary immobility of the patient serves to increase the risk. Deep venous thrombosis (DVT) in the lower extremities is readily visualized by using Doppler ultrasonography (US). However, most clinically significant and potentially deadly thrombi occur in the veins of the pelvis, an area not easily accessible with US. Magnetic resonance venography (MRV) is potentially useful in assessing the pelvic venous system.
  5. Late complications are possible.
    1. Pain is the most common long-term complaint of patients with pelvic fractures. Pain most often is associated with abnormalities of the SI joint. Osteoarthrosis, malunion, and nonunion are potential etiologies of the pain.
    2. Malunion of the fracture most often occurs in the setting of unreduced pelvic fractures. Leg-length discrepancies can result, resulting in gait abnormalities and pain.
    3. Nonunion of the fracture develops in the setting of vertically unstable pelvic fractures. Treatment for this uncommon complication requires stable fixation of the pelvic disruption and correction of any malpositioning.

 

The Young-Burgess and the Tile systems are 2 major classification schemes that have been developed for describing pelvic ring fractures. Both systems are based on the direction of the injuring force. The Young-Burgess classification system focuses on the degree of injury. The Tile classification system focuses on pelvic stability.

The Young-Burgess system is as follows:

  1. AP compression injury
    1. The hallmark of the AP compression injury is pubic diastasis with or without disruption of the SI joints. The location and degree of diastasis is correlated with the magnitude of force imparted to the pelvis and with the amount of resulting instability. The AP compression causes the pelvis to open: one or both hemipelves undergo external rotation. According to the Young-Burgess classification system, 3 degrees of AP compression injury are identified.
      1. Type I injuries: Less than 2.5 cm of the pubic diastasis is noted, either at the symphysis or through vertically oriented rami fractures. The SI joints and posterior ligaments remain intact, and stability is maintained.
      2. Type II injuries: The amount of anterior diastasis exceeds 2.5 cm. In addition, diastasis occurs in 1 or both of the SI joints. This incomplete posterior arch disruption results in rotational instability. The posterior ligaments are not injured; therefore, vertical stability is preserved.
      3. Type III injuries: These injuries extend to the posterior SI ligaments, which are disrupted. Consequently, the pelvis is vertically and rotationally unstable.
    1. External rotation of the hemipelvis results in an increase in the volume of the pelvic cavity. This increased pelvic volume allows more pelvic hemorrhage to occur before the osseous and soft-tissue structures cause tamponade. Exsanguination from a pelvic hemorrhage is a primary potential complication. Reduction of the increased pelvic volume is a primary goal in resuscitating a patient with an AP compression injury. Immediate reduction can be achieved by tightly wrapping the pelvis in sheets or a pneumatic antishock garment. The application of an external pelvic fixation device results in more definitive reduction. AP compression injuries are also strongly associated with brain and intra-abdominal injuries.
  1. Lateral compression injury
    1. Lateral compression injury results in internal rotation of the affected hemipelvis. This internal rotation decreases rather than increases the pelvic volume. Consequently, pelvic vascular injuries and resulting hemorrhage are less common with this injury than with other injuries. Lateral compression injuries are associated with brain and intra-abdominal injuries.
    2. The hallmarks of a lateral compression injury include sacral buckle fractures and horizontal pubic rami fractures. The Young-Burgess classification system describes 3 types of injuries.
      1. Type I injuries: These involve a force directed posteriorly to the lateral aspect of the hemipelvis, which results in an ipsilateral sacral buckle fractures; ipsilateral horizontal pubic rami fractures; or, less commonly, disruption of the pubic symphysis with overlap of the pubic bones. The posterior ligaments remain intact; therefore, the pelvis is stable. Lateral forces directed anteriorly to the hemipelvis produce type II and type III injuries.
      2. Type II injuries: These involve more internal rotation of the hemipelvis. As in type I injuries, ipsilateral sacral buckle fractures and horizontal pubic rami fractures are associated with fracture of the ipsilateral iliac wing or disruption of the ipsilateral posterior SI joint. The pelvis is rotationally unstable, but its vertical stability is maintained.
      3. Type III injuries: The force continues from the ipsilateral side across the midline to affect the contralateral hemipelvis. The ipsilateral hemipelvis sustains either a type I or type II injury with associated internal rotation. The contralateral pelvis undergoes external rotation. This pattern has been described as a windswept pelvis. Contralateral vertical pubic rami fractures or disruption of the sacrotuberous and/or sacrospinous ligaments may occur. As in type II injuries, the pelvis is rotationally unstable but vertically stable.
  2. Vertical shear injury
    1. A vertically oriented force applied to a hemipelvis, usually by the femur, results in a vertical shear injury. At the anterior aspect, vertically oriented fractures of the pubic rami occur. Posteriorly, the ipsilateral SI joint (or occasionally the contralateral SI joint) and its associated ligaments are disrupted.
    2. The affected hemipelvis is displaced in a cranial direction. Complete disruption of the posterior ligaments yields a rotationally and vertically unstable pelvis.
    3. Associated injuries seen in the vertical shear pattern are similar to those encountered in type III AP compression injuries.
  3. Complex injury
    1. The forces applied to the pelvis may not conform to the primary vectors described for other types of injuries.
    2. Complex injuries involve more than 1 pattern of injury. The specific findings of each pattern still are present.
    3. Pelvic stability can be determined by using the criteria outlined above.
  4. Ring-sparing injury
    1. The Tile classification system includes fractures of the pelvis that do not significantly disrupt the pelvic ring (Tile type A). These injuries include avulsion fractures of the anterior iliac spine, iliac crests, and ischial tuberosities.
    2. Also included are iliac wing fractures and sacrococcygeal fractures that do not involve the SI joints. Minimally or nondisplaced pubic rami fractures resulting from a direct blow or straddle injury do not affect pelvic ring stability.

Scanning Technique

 

 

Scanner

Content

Protocol

 Pelvic - Non Contrast

Scanning Range

2 cm above the Iliac Crest 2 cm below hte symphisis pubis

Scan direction

 Cranio-caudal

Detetector Collimation

 64 x 0.6 mm

kVp

 120

mA

 330

Rotation Time (ms)

 500

Pitch

 1.0 mm

DLP (mSv)

Reconstruction Thickness

 1.0 x 0.7 mm

Reconstruction Kernel

 B31f - Smooth; H70f - Sharp

 

Contrast

 n/a

Site of Cannulation

 n/a

Contrast Volume

 n/a

Saline Volume

 n/a

Contrast Flow rate

 n/a

Level of Dynamic Scan

 n/a

Type of Triggering

 n/a

ROI

 n/a

 

 

Images

 

 

Preferred Examination

  1. Radiography
    1. AP radiography of the pelvis
      1. AP radiographs of the pelvis and chest and lateral radiographs of the cervical spine are included in the initial radiographic assessment in a patient with major traumatic injuries.
      2. Radiographs are obtained with the patient in the supine position, with the x-ray beam passing in an AP direction.
      3. Abnormalities depicted on the AP pelvis radiograph direct the need for the next set of radiographs, which include oblique (Judet) views of the pelvis in acetabular fractures (See also the eMedicine article Acetabulum, Fractures, as well as the article Evaluation of Blunt Abdominal Trauma Using PACS-Based 2D and 3D MDCT Reformations of the Lumbar Spine and Pelvis, on Medscape), and inlet and outlet radiographs of the pelvis in patients with pelvic ring fractures.
    1. Inlet and outlet radiography of the pelvis
      1. Inlet radiographs of the pelvis are obtained with the patient in the supine position, with the x-ray tube positioned at the patient's head and angled 45° toward the feet . The x-ray beam is perpendicular to the pelvic brim (or inlet). This view allows the evaluation of pelvic brim integrity, AP displacement of the hemipelvis, internal/external rotation of the hemipelvis, and sacral impaction.
      2. Outlet radiographs of the pelvis are obtained with the patient in the supine position, with the x-ray tube positioned at the patient's feet and angled 45° toward the head. The x-ray beam is perpendicular to the sacrum. This view allows confirmation of vertical (cranial) displacement of the hemipelvis and evaluation of the sacral neural foramina.
  1. Pelvic CT
    1. CT images may be obtained in isolation or in a combination of abdominal and pelvic CT scans during the initial trauma evaluation.
    2. Axial CT scans may be obtained, but helical CT scans (especially with multi-detector CT) yield better 2-dimensional (2D) and 3-dimensional (3D) images.
    3. CT scans allow the detection of subtle fractures and displacements not appreciated on radiographs.

Limitations of Techniques

Radiographs of the pelvis may not demonstrate subtle fractures that do not affect classification of the injury. Spatial orientation of fracture fragments and joints is visualized better on pelvic CT scans.

Pelvic CT scans require transport of the patient to the CT scanner, although most patients need to undergo abdominal and pelvic CT for an assessment of visceral injury.

Diagnosis

 

A transaxial multidetector CT scan of the Pelvis post MVA was performed. There is an obvious vertical fracture through the body of the ischium and ramus of the left side of the pelvis. There is minor disruption of the interior pelvic ring. There is no evidence of Pubic diastasis. There is an obvious verticle fracture through the middle third of the sacrum extending through the scaral foramina. This fracture is classifiedas a vertical shear type 2 with minimal displacement. There is an obvious underlying ligamentous injury associated with this vertical shear fracture.
The information contained in this monthly case presentation is for educational purposes only and is not intended to be relied upon for desirable practice of medical Imaging in any department. Any health care practitioner and technician reading this information is reminded that they must use their own learning, training and expertise in dealing with their individual patients as per their specific departmental protocol. This material does not replace that duty and is not intended by Charbel Saade to be used for any purpose in that regard.

The drugs and doses described are consistent with the scanning protocol, however, before administration, dose selection and contrast type, careful patient analysis should be adhered to according to departmental policy and procedure. Charbel Saade releases himself from any medico-legal issues relating to poor scanning and interpretation of information from this case study. As a guide to all please use your specific departmental protocols and consult with referring physicians regarding each individual patient..

 
 
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