1 Anatomy and classification

The basic principles of pelvic anatomy is the same in children and adults; the pelvis is formed from three main bone elements that develop from three primary ossification centers: the ilium (iliac bone), the ischium (ischial bone), and the pubis (pubic bone). These three elements meet at the triradiate cartilage (Y physis), which is part of the acetabulum ( Fig 1.14-1 ). Depending on the development and the gender of the child, the triradiate cartilage closes between ages 14 and 18 years [1, 2]. Pelvic injuries in children can be problematic because the skeletal segments may not yet be fused, depending on the child′s age and skeletal maturity.

By the age of 20, all physes/apophyses are usually closed. This special characteristic of the immature skeleton in which cartilaginous elements mature later into bone structures means that serious fractures are seldom seen, especially in younger children. Up to the teenage years the pelvis is highly elastic and malleable. However, the normal x-ray visibility of cartilaginous elements adjoining the bone presents a significant diagnostic problem ( Fig 1.14-2 ).

In addition to the three main growth centers fused as triradiate cartilage at the acetabulum, a child′s pelvis has several apophyses. These secondary ossification regions include the iliac crest apophysis, which is the largest, the ischial apophysis as the attachment of the ischiocrural (hamstring) muscles, the anteroinferior spine as the attachment of the rectus femoris muscle, the pubic tubercle, the angle of the pubis, the ischial spine, and the lateral wing of the sacrum.

The developmental appearance of the iliac crest apophysis determines the degree of skeletal maturity [1–3]. Physes and apophyses represent anatomical weak points and therefore are particularly subject to injury. Apophyseal injuries often lead to diagnostic errors (eg, suspicion of a tumor) or simply can be overlooked.

The ability to understand and interpret relevant, age-specific pathology and recognize skeletal peculiarities in children is essential. These characteristics change relatively rapidly during puberty; thus, from this age on, fractures and other injuries can be considered equivalent to those in adults for the purpose of diagnosis and treatment. This chapter focuses on the developing pelvis in children younger than age 12–13 years.

Histological investigations have shown the triradiate cartilage physis to be bipolar, a germinative zone extending along all three arms of the pelvis beside a highly vascular central zone. From there, three dimensional (3-D) growth of the acetabulum takes shape. In contrast to a normal physis, which is peripherally bounded by the zone of Ranvier, the triradiate cartilage has two elements: an intraarticular, cartilage-covered element and a strong intrapelvic perichondral-fibrous element, described by Ponseti [4]. The latter is durable but produces a massive callus when injured, which can cause growth abnormalities or growth arrest through bridging to the acetabulum ( Fig 1.14-3 ) [5].

The largest apophysis is on the iliac crest ( Fig 1.14-4 ). Although it remains invisible radiographically during the first years of life, the iliac crest ossifies at the beginning of puberty. This process proceeds from anterior to posterior and can exhibit multiple growth centers. This apophysis serves as the 3-D point of attachment for the all abdominal muscles. Other muscle attachments are recognizable along the ischial apophysis and the anterior inferior iliac spine. The ischial spine serves as a tendon attachment, whereas the apophysis of the pubic bone provides a symphysis with a discoid connection across the two halves of the pubis.

The connection between ischial and pubic branches is neither apophysis nor actually physis; it is called a synchondrosis and can exhibit specific variations in growth and closure, which often leads to diagnostic errors. A blister-like formation seen shortly before closure often is misinterpreted as a malignant tumor ( Fig 1.14-5 ).

These three pubic elements are radiographically visible before birth. When following skeletal development radiographically from birth to adolescence, these three elements are seen to ossify and grow outward eccentrically from the triradiate cartilage or acetabulum [2].

1.1 Classification of injuries

There is no special classification for pelvic fractures in children. Hence, most surgeons use the AO/OTA Fracture and Dislocation Classification for adults originally proposed by Pennal and Tile [6]. This system consists of three principal groups: type A (stable fractures); type B (rotationally unstable, vertically stable fractures); and type C (rotationally and vertically unstable fractures) ( Fig 1.14-6 ). (For details, see Chapter 1.3).

Other classification systems have been described [7–10]. Silber et al [7] used closure of the triradiate cartilage as a main distinguishing criterion. The four-type system of Key and Cornwell [8] differs little from the AO/OTA Fracture and Dislocation Classification system, except that the authors further consider the acetabulum. Torode and Zieg [9] also propose a four-group system, both von Laer et al [10] and Thannheimer and Bühren [11] proposed just two groups. This simplified approach is for children younger than age 10–12 years and is both practical and prognostically relevant. Injuries are classified into two groups: those with potentially serious long-term defects and/or malunion and those without:

Injuries without expectation of serious negative effects and/or malunion include avulsion fractures, fractures of the iliac body, isolated fractures of the pubic bone, and instability in the iliosacral joint.

Injuries with potentially serious negative effects and/or malunion include rupture of the symphysis, overlooked or unrecognized iliac crest avulsions, acetabular fractures, and Malgaigne fractures.

With appropriate treatment, even complex fractures of purely bone elements generally heal well cosmetically and without long-term negative effects because even simple fractures of osteochondral and physeal elements can lead to serious pubic growth abnormalities ( Fig 1.14-7 ) [12].

With respect to fracture stability, the same criteria apply in children as in adults. Also with children, it should be stability first; this means stability of the pelvis has a higher priority than fracture displacement or fracture morphology.

1.1.1 Stable fracture criteria:

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  Apophyseal injuries/avulsions. Attachment of the rectus femoris (anterior inferior iliac spine)

  
  
  
  
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    – Adductor attachment in the region of the pubic apophysis

    
    
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    – All flexor attachments (biceps femoris, semitendinosus plus semimembranosus muscles in the region of the ischial bone [ischial tuberosity])

    
    
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    – Sartorius in the region of the anterior superior iliac spine

  
  
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  Fractures of the iliac bone

  
  
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  Fractures of the pubic bone

  
  
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  Stable iliosacral joint lesions

1.1.2 Unstable fracture criteria:

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  Rupture of the symphysis

  
  
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  Fractures of the acetabulum

  
  
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  Malgaigne fractures (double vertical fractures of the pelvic ring on the pubic bone and the iliosacral joint)

1.2 Diagnosis

A detailed case history can greatly assist the diagnosis, especially with children below age 10. For example, if a large tractor wheel rolls over a child on soft ground in a farming accident, the child generally is pressed deeply into the ground, often sustaining only slight injury. The same mechanism of injury in a larger or older child could cause more serious injuries (eg, bone and abdominal lesions).

The quality of imaging studies is of critical diagnostic importance, especially in younger children. Besides the typical changes seen in the pelvic skeleton, indirect signs of injury must be identified. Even today, in the era of the spiral computed tomography (CT), conventional x-ray remains the gold standard. Inlet and outlet view x-rays can deliver essential information, even in a child in stable condition [13].

However, in cases of uncertainty or for the purpose of operative planning, CT scans, including 2-D reconstructions, are considered the gold standard. These images are better able to show a fracture pattern than is possible on the surface of a 3-D reconstruction, especially in the acetabular and iliosacral regions ( Fig 1.14-8 ) [14, 15].

Magnetic resonance imaging (MRI) should not be included among the primary diagnostic procedures, as it usually requires anesthesia, is time consuming and poorly demonstrates bone structures [16]. Ultrasound does not work well for diagnostic imaging of bone structures but sometimes can be used immediately in the emergency department as a so-called “fast-sono” to assess abdominal organs or identify larger hematomas. It also is helpful in demonstrating apophyseal injuries and evaluating dislocations because these injuries typically are not apparent on x-rays in younger children (ie, under 8–10 years old).

2 Patient selection and indications

The etiology of pelvic and acetabular injuries in children is relatively uniform, owing to the anatomical and morphological features already described. Pelvic injuries in children generally are the result of high-energy trauma. This mechanism of injury in children historically has been rare but its frequency recently has increased worldwide. Younger children sustain severe pelvic injuries with serious long-term consequences from high-speed motor vehicle collisions. Young children also are injured in high-energy sports. With a normal fall, the amount of kinetic energy is too low for a 5- or 6-year-old child to sustain severe pelvic energy. The amount of energy changes dramatically when sporting equipment such as inline skates or skateboards is used. Hence, the frequency of pelvic fractures in growing children differs widely regionally as socioeconomic aspects and regional hospital catchment areas vary considerably. In a major Swiss pediatric orthopedic referral center, more cases were cited than in a parallel multicenter German study [13, 17, 18]. This highlights the problem of any statistics or publication. The frequency of an injury varies significantly depending on the location of any given hospital. The above-mentioned Swiss clinic is located in a popular skiing area; there are consequently many skiing accidents with patients frequently sustaining pelvic injuries.

Indications for operative therapy in children depend on a variety of factors. In children older than 12–14 years, the same criteria apply as for adults, specifically the need for pelvic stabilization in the context of damage control and permanent anatomical and functional stabilization [13, 19]. Pelvic fractures frequently occur in combination with other serious injuries; of these, head injuries are the most common (25%) ( Fig 1.14-9 ). Various frequencies and combinations of other injuries also have been documented ( Table 1.14-1 ).

In children younger than age 8–12 years, the pelvis is still elastic and can readily deform without causing severely displaced fractures. The thick periosteum and the tendinous structures of the pelvis contribute to this resistance to deform. Following severe pelvic injuries, the risk for hemorrhage may remain high, and the need for emergency intervention because of circulatory problems represents the exception. If associated injures to internal organ (eg, bladder, urethra, rectum) have been excluded, there is sufficient time to form a clear picture of the pelvic injury and potential long-term outcome. This allows an opportunity for injury- and agedependent options to be considered and treatment to be initiated [20, 21].

The width of the symphysis changes significantly with growth. In early childhood, it is almost 1.5 cm wide; however, by the time a child is 12 or 13 years old, it measures only 5–6 mm. Lack of familiarity with this anatomical feature can often lead to misdiagnosis. In small children, for example, a radiographic diagnosis of symphysis rupture can be made but clinical symptoms ignored. This misinterpretation leads to unnecessary stabilization measures or even surgery. Thus, when in doubt, functional imaging is indicated ( Fig 1.14-10 ).

Note: Less experienced colleagues have enough time to obtain consultation with a specialist or to transfer the child to an appropriate center that specializes in treating children. Instituting inappropriate therapy is to be avoided.

3 Preoperative planning

Before a definite decision about the mode of therapy can be made, the following investigations should be performed during emergency and primary care, preferably according to a standardized algorithm [1, 22]:

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  Clinical stability test

  
  
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  Examination and evaluation of body orifices (urethra/rectum/vagina)

  
  
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  Examination of genital organs

  
  
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  Radiographic assessment of urethra and bladder using a contrast agent

  
  
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  Abdominal ultrasound

  
  
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  Adequate diagnostic imaging studies (pelvic x-ray and CT)

The goal of treatment should be to provide pelvic stability that facilitates early mobilization and early functional treatment, allows easy care, and results in complete recovery.

Related posts:

1.15.2 Insufficiency fractures of the pelvis: operative management 1.13 Urological injuries in pelvic ring trauma: assessment and management in male patients 1.15.1 Insufficiency fractures of the pelvis: metabolic and nonoperative workup 1.11 Open pelvic fracture 1.12 Pelvic ring disruption in women: genitourinary and obstetrical implications 1.10 Lumbosacral instability and stabilization

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