Traumatic pelvic fractures in children and adolescents
Introduction
Pelvic fractures are extremely uncommon traumatic injuries in pediatrics, occurring with an estimated incidence of 1 per 100,000 children per year.5, 6 Despite their rarity, such injuries are identified in 2.4–7.5% of the pediatric trauma patient population.1, 2, 3, 7, 8, 9 It is therefore important for traumatology, emergency medicine, critical care, and orthopedic providers to understand how patterns of pelvic and acetabular fractures affect management and prognosis.
Pelvic fractures in children differ significantly from those in adults because of differences in physiology and mechanism of injury. The pediatric pelvis is particularly resistant to fracture due to its intrinsic flexibility. Accordingly, the incidence of pelvic fractures in the pediatric trauma population is approximately half the rate seen in adults.1, 2 Because of the inherent resiliency of the immature pelvis, a non-avulsion pelvic fracture in a child should be considered a marker of high-energy trauma and alert providers to the likelihood of concomitant injuries that may represent a significant threat to survival.
The majority of traumatic pelvic fractures in children occur as the result of pedestrian versus motor vehicle accidents. This mechanism accounts for 39–78% of cases.2, 8, 9, 10, 11, 12, 13, 14, 15 Motor vehicle accidents (passenger injuries) are the major cause of adult pelvic fractures and the second most common cause of pediatric pelvic fractures, causing 10–30% of cases.2, 8, 9, 10, 11, 12, 13, 14, 15 The anterior–posterior compression experienced by passengers during rapid vehicle deceleration is more likely to cause pelvic enlargement, sacroiliac (SI) joint disruption, and pelvic vessel laceration.16 Thus, adults are naturally at a higher risk for fracture-related vascular injury and exsanguination.
Other common mechanisms for pediatric pelvic fractures include falls, bicycle and motor bike accidents, and high-energy sports injuries.
Flexible bone and thick, strong periosteum help to account for the pediatric pelvic ring׳s resilience. Additionally, when compared to adults, the sacroiliac and symphyseal joints of children are more elastic and the symphysis pubis is thicker. The immature pelvis is therefore able to dissipate a relatively large amount of energy before failing. As a result, multifocal ring fractures and pelvic ligament disruptions are quite rare in children. While the adult pelvis has been likened to a hard pretzel—impossible to break in one place without causing a second fracture17—this analogy does not extend to pediatric patients. In children, unifocal ring injuries are not unusual. A more appropriate analogy for the disruption of the immature pelvis may be the breaking of a soft pretzel—a break in one location does not necessitate a second one. Unstable, segmental ring fractures are thus much less common in children than adults.
While children have durable pelvic rings, they also have more effective hemostatic responses. When compared to the sclerotic vessels of adults, children׳s blood vessels are smaller in caliber and more reliably vasoconstrict in the event of hemorrhage. The thick, adherent periosteum of pediatric bones also limits fracture displacement and tamponades bleeding from raw bony surfaces. Due to these physiologic factors, traumatic pelvic fractures almost never lead to life-threatening arterial hemorrhage in children, while they do so in 10–20% of adult traumatic pelvic fracture cases.18, 19, 20
The immature pelvic bone is marked by the presence of growth plates (physes) and cartilage undergoing endochondral ossification. Three primary ossification centers in each pelvic bone represent the developing ilium, ischium, and pubis. Several secondary ossification centers arise as development continues. Practitioners must be aware of these structures in order to appropriately interpret radiologic studies of the pediatric pelvis (Figure 1). The physeal junction of the ilium, ischium, and pubis occurs at the immature acetabulum, comprising the Y-shaped triradiate cartilage. The closure of this structure, which occurs at 12–14 years of age,4 has been shown to be one of the best radiographic indicators of skeletal maturity in a patient.8 In patients with fused triradiate cartilage, acetabular injury patterns are more like those seen in adults. In these patients, adult orthopedic trauma specialists should be consulted.8 Injury to an open triradiate cartilage, which may be isolated or part of a larger pelvic ring fracture, must be identified, as it greatly affects treatment and can result in long-term growth arrest of the acetabulum (see section on Acetabular dysplasia).
Practitioners should be aware of when other ossification centers appear and close (Figure 1B). For example, the pubis and ischium fuse at the inferior pubic ramus at age 6–7, the main iliac crest ossification center appears at age 13–15 and fuses at age 15–17, and the secondary ischial ossification center appears at age 15–17 and typically fuses by age 19. The anterior–inferior iliac spine (AIIS) ossification center appears around age 14 and disappears by age 16. Three secondary ossification centers also appear in the acetabulum around adolescence.4 As these normal structures and variants can easily be confused for fractures, it is recommended that an experienced pediatric orthopedist or radiologist assist in analyzing any radiologic studies.
Many secondary ossification centers represent muscle origins, which are separated from main ossification centers by cartilaginous apophyses. Avulsion fractures, which are some of the most common pediatric pelvic fractures, are low-energy injuries that occur when traction from an attached muscle pulls a developing muscle origin from its normal anatomic site. These apophyseal injuries—which include ischial tuberosity, anterior–superior iliac spine (ASIS), and AIIS avulsions as well as iliac apophysitis—are typically seen in the context of sports injuries. Avulsions are low-energy fractures that are managed on an outpatient basis and tend to heal with protected weight‐bearing and temporary activity restriction. Accordingly, they are not the focus of this article.
Section snippets
Diagnosis of traumatic pelvic fractures in children
The approach to the pediatric trauma patient must be systematic and multidisciplinary. Although evaluation and management is typically led by a surgical traumatologist or emergency medicine physician, it is important to include orthopedic specialists and others throughout the patient׳s course. With potentially complicated polytrauma patients entering the trauma bay, it is vital that the team follow a standardized, validated care approach.
Management of pelvic fractures
After initial surveys and imaging have revealed a pelvic fracture, the subsequent approach to care depends upon the type of fracture and the presence of other injuries. As the patient is evaluated, it is important to recognize the status of the triradiate cartilage. Recognizing pelvic instability and the presence of multiple pelvic fractures is also important, as it has been shown that those with multiple pelvic fractures are more likely to need orthopedic surgical intervention and blood
Associated injuries
Research has shown that approximately 58–100% of children with traumatic pelvic fractures also have associated non-pelvic injuries.2, 10, 11, 14, 35, 36 Thus, pelvic fractures should be seen as indicative of other concomitant injury, especially if the patient has obvious deformities, depressed mental status (GCS < 15), or hypotension. Of the 15% of patients who presented with blood pressure more than 10 mmHg below normal values for age in a study by Chia et al.,11 all had suffered at least one
Mortality
Published series dating back to 1991 show a mortality rate ranging from 0% to 12%2, 10, 11, 13, 14, 15, 24, 30, 37 for children with traumatic pelvic fractures versus about 17.5% for adults.14 However, most pediatric deaths are due to neurologic or visceral injury. Pelvic fracture and related hemorrhage has been deemed responsible for death in less than 1% of all pediatric cases in contrast to the 3.4% rate seen in adults.3, 37 Mortality and morbidity generally increase with fracture severity.
Conclusion
Traumatic pelvic fractures are much different in children than adults. While they occur much less frequently, these fractures should not be taken lightly. Trauma providers should take away several key messages about these injuries.
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When dealing with patients with traumatic pelvic fractures, ATLS principles still take precedence. Stabilizing the patient must be the top priority of the treating team.
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Despite the resilience of the pediatric pelvis, unstable pelvic ring injuries are possible, and
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