Introduction
The majority of pelvic fractures are the result of high energy blunt injures. As such, patients with these fractures require emergent and thorough evaluation. Treatment can be surgical or nonsurgical but emphasize the re-establishment of a stable ring structure that allows appropriate transfer of weight from the torso to the hips and legs. As compared to the extremities, the pelvis has greater soft tissue constraints as well as vital non-musculoskeletal structures. Therefore, treatment of pelvic fractures often requires techniques that differ from those used in the extremities.
Anatomy
Bony Anatomy - the pelvis is composed of 3 bones, 1 sacrum and 2 inominate bones which in turn form from the fusion of the immature ischium (inferoposterior), illium (superior) and pubis (inferoanterior). The acutabulm forms at the junction of these 3 bones (see Acetabular fractures for more detail) Important bony prominences and landmarks include the anterior superior illiac spine (ASIS), the anterior inferior illiac spine (AIIS), illiac crest and fossa, posterior superior illiac spine (PSIS), the ischial spine, ischial tuberosity, inferior and superior pubic rami, pectineal eminence and pubic tubercle. [Figure to show landmarks via lateral view of inominate bone and anterior view of the pelvis]
Ring stability - the bony pelvis is stabilized primary by the symphysis pubis anteriorly and the sacroilliac (SI) joints posteriorly. The pubic symphysis is composed of a complex of hyaline cartilage, fibrocartilage and fibrous tissues. The SI joints are are composed of both hyaline and fibrocartilage. However, it is not a true synovial joint as it does not originate from an anlage of condensed mesanchyme. The joints are stabilize via posterior, anterior and interosseous ligaments; the latter are the strongest ligaments in the body. The anterior and posterior elements of the pelvis are further stabilized relative to each other through sacrospinous (anteroposterior and rotational vectors) and long and short sacrotuberous (vertical vector) ligaments. From a superior view with the pubis facing down, the sacrum forms an upside down keystone (or suspension bridge) that does not have inherent stability; with loss of bony or ligamentous constraints, the sacrum tends to displace anteriorly (the bridge will fall). From an anterior view the sacrum forms the keystone of an arch that transfers weight from the spine to the acetabuli.
Non-musculoskeletal structures - the pelvis has an intimate and constrained relationship with a number of structures including branches of the lumbosacral plexus, main and terminal branches of the iliac vascular system, lower gastrointestinal tract, and genitourologic structures including the bladder and urethra. [Figures to show these relationships--one for nervous, one for vascular, one for GI and one for urologic] Knowledge of this anatomy is critical to complete evaluation of the patient as well as for uncomplicated surgical managment.
Classification
Anatomic - The Letournel system is based purely on the location of the fracture. [show Figure]
Mechanism - Penal first introduced a mechanistic classification system in 1961 composed of lateral compression (LC), anterior-posterior compression (APC), and the vertical shear (VS). Young and Burgess (1986) further subdivided LC into 3 types: I - pubic rami fractures with impaction of the SI joint; II - pubic rami fractures with internal rotation, posterior disruption (iliac wing fracture or varying degrees of anterior SI impaction and posterior SI disruption depending on location of impact on ilium); III - LC fracture on one with APC (external rotation) fracture on contralateral side. APC fractures were divided into anterior ring widening with intact posterior elements(I); SI anterior widening, external rotation of the ilium and disruption of sacrotuberous and sacrospinous ligaments (II); and complete posterior/SI disruption (III). One of the strengths of this system is that it is predictive of associated injuries and may aid in the initial evaluation and stabilization of the patient.
Stability - Bucholtz in 1981 and Tile in 1988 created a system based on stability. The Tile classification contains Type A, stable (1-avulsion and 2-minimally displaced ring), Type B, rotationally unstable and Type C, rotationally and vertically unstable. The OTA/AO scheme present a variation where Type A is stable (avulsion, impaction, transverse sacral/coccygeal), B is partially stable (unilateral/partial in external or internal rotation, bilateral/partial) and C is unstable (unilateral/complete, bilateral/complete-incomplete, bilateral/complete).
Presentation
Mechanisms of Injury - direct impact to the pelvis with indirect transfer of forces to anterior and posterior ring elements. Most common settings include motor vehicle and pedestrian-vehicle crashes. Motorcycle crashes, fall from heights and crush injuries are less common. Mechanisms can include LC, APC, VS or combinations thereof with impact forces resulting in rotation-translation of a hemipelvis fragment relative to the sacrum in the axial plane or translation in the coronal plane.
Other systems within the pelvis injured - Arteries injured include the Iliolumbar artery, superior gluteal artery, lateral sacral artery and the internal iliac artery. When an actively bleeding artery if identified, it is most frequently the internal pudendal. Neurologically, L5, S1 are the most commonly injured spinal nerve roots. The degree of displacement of the posterior elements rather than specific location appears to be more important determinants of injury. Injuries to the bladder, urethra, rectum or distal colon (and the vagina in women), is not uncommon.
Comorbidities - significant injuries to the viscera, great vessels (highest in APC-III) and head (highest in LC-II) are common with high energy mechanisms. APCs have the highest rate of blood loss and death with APC-IIIs having a mortality rate as high as 37%. Newer studies, however, have called into question these particular associations with specific fracture patterns. Nonetheless, the risk of additional injuries approaches 40-50 percent.
Diagnosis
Patients with significant pelvic ring injuries should receive a full trauma evaluation including assessment of Airway, Breathing, Circulation according to American College of Surgeon's Advanced Trauma Life Support.
Radiographic evaluation
Initial radiographic evaluation includes AP, Inlet (40 degree caudal) and Outlet (40 degree cephalad) views of the Pelvis. The AP provides initial assessment of the anterior and posterior portions of the ring and possible concomitant acetabular injuries. Anterior ring injuries are often easily seen and include symphysis diastasis and pubic rami fractures. Posterior injuries can be more subtle especially if they involve the sacrum or sacroiliac (SI) joint. Signs of posterior injury or instability include irregularities of the SI joint, fracture of the L5 transverse process and inferior pubic ramus fracture. The inlet view provides information regarding rotation of each hemipelvis/illium and translation of the ilium relative to the sacrum (most often posterior translation in SI dislocations and SI fracture-dislocations aka crescent fracture). The outlet view shows sagital plane rotation, vertical displacement (often cephalad migration of ilium--complete separation and migration named a Malgaign fracture) and sacral fractures. Judet views are not typically need unless there is a concomitant acetabular fracture or a better view of a ramus rootlet fracture is sought (especially in preparation of an anterior column screw).
With any significant pelvic injury, a CT scan with fine cuts should be obtains. Special attention should be paid to the posterior elements as sacral fractures can be missed on plain radiographs. In addition, CT allows for measurement of "safe zone" in the bodies of S1 or S2 if iliosacral screws are indicated, degree of anterior,posterior sacral alar comminution or SI gapping with hemipelvis rotation and sacral foraminal involvement on coronal images.
Treatment
Operative versus nonoperative
Initial stabilization - anterior external fixator v posterior C clamp
Definitive operative fixation
Complications
Infection and soft tissue
Thromboembolism
Malunion
Nonunion
Screw misplacement
Red Flags and Controversies
Morel Lavale Lesion
Outcomes (oku & tile book)
Functional outcome measures
Nature of injury and quality of reduction
Associated injuries
Misc.
Pelvic fractures and pregency
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