Pediatric Pelvis Fractures

Pediatric Pelvis Fractures

Prepared by Dr. Murat TASCI

Epidemiology:
Pelvic fractures account for approximately 1–2% of all pediatric fractures and have been reported to occur in 1 out of every 100,000 children annually (1) (2).

• Among all pediatric pelvic fractures, the incidence of acetabular fractures ranges between 4% and 20% (3) (4).
• Most acetabular fractures occur in the adolescent age group  (5).

Clinical Presentation:
In the pediatric age group, the presence of a large amount of cartilage tissue and a thick periosteum in the pelvis reduces the likelihood of pelvic fractures.

• If pelvic fractures are encountered in pediatric patients, they are usually the result of high-energy trauma and are highly likely to be accompanied by injuries to other organs  (6) (7).

ANATOMY

• The pelvic region begins to develop in the second month of embryological development. The ilium, ischium, and pubis bones converge at the triradiate cartilage, forming the acetabulum.
• The symphysis pubis, which has a thick cartilaginous structure, shows variable ossification until around the age of 10. The iliac crest and prominences remain cartilaginous until adolescence, with secondary ossification centers appearing between the ages of 13 and 15.
• Ossification of the iliac apophysis occurs from anterior to posterior (toward the posterior superior iliac spine). It fuses with the remainder of the ilium between the ages of 15 and 17, and this process continues until approximately age 25  (7).
• In relation to age, children have a higher proportion of cartilage and a thicker periosteum.
• As the cartilaginous structure increases, so does elasticity. Compared to adults, the sacroiliac and symphyseal joints in children are wider and thicker, with greater capacity for energy absorption  (8).
• Since fractures in the pelvis are rare, if a fracture is detected, accompanying organ injuries must be thoroughly investigated.
• Mortality is generally due to head, thoracic, or abdominal injuries. Mortality due to isolated pelvic fractures is lower in children than in adults  (7) (9). The thick periosteum provides a strong tamponade effect, helping to reduce bleeding  (10).

TRAUMA MECHANISM

• The most common causes are motor vehicle accidents (both as a pedestrian or occupant) and motorcycle accidents  (7).
• These typically result in lateral compression injuries and are often accompanied by head and thoracic trauma (11).
• The predominance of lateral compression injuries in pediatric patients results in less pelvic volume expansion, which contributes to lower mortality rates in this population (12).
• Apophyseal avulsion fractures, on the other hand, usually occur due to low-energy trauma such as jumping. These are typically tendon origin avulsion-type injuries.
• Examples include:
  • Ischial avulsion fracture: due to hamstring and adductor muscle traction.
  • Anterior inferior iliac spine (AIIS) avulsion: by rectus femoris.
  • Anterior superior iliac spine (ASIS) avulsion: by sartorius muscle.
  • Symphysis pubis or iliac crest avulsion: due to abdominal muscle traction.
  • Lesser trochanter avulsion fracture: by iliopsoas muscle.

Imaging

• Anteroposterior (AP) and lateral pelvic radiographs are routinely obtained. In some cases, whole-body computed tomography (CT) scans may also be performed to evaluate for polytrauma  (13) (14).
• The necessity of CT imaging in children remains controversial due to concerns about radiation exposure and whether the findings will alter clinical management.
• In addition to the standard AP view, inlet, outlet, and oblique Judet views may also be obtained for a more detailed assessment.
  • In young children, the pubic symphysis width may be up to 10–12 mm, whereas in older children, it is typically 2–4 mm.
• Acetabulum fractures:
  • Acetabular fractures may be accompanied by hip dislocations, which must be reduced promptly to preserve femoral head vascularity.
  • Following reduction, radiographs and CT scans, and if necessary, MRI, can be used to assess for intra-articular loose bodies and joint congruity.

Classification

• Watts’ Classification:
  • Includes simple avulsion fractures, pelvic ring fractures (either stable or unstable), and acetabular fractures.
• Torode and Zieg Classification (1985):
  • Developed in 1985 by Torode and Zieg  (15), this classification is based on plain radiographs.
  • It incorporates both anatomical and mechanical factors.
  • It also associates the mechanism of injury with the severity of the fracture (15).

Type		Description
Type I		Avulsion fractures
Type II		Iliac wing fractures (usually caused by direct lateral trauma)
	Type IIa	Separation of the iliac apophysis
	Type IIb	Fracture of the iliac wing
Type III		Simple pelvic ring fractures involving the pubic rami or symphysis pubis
	Type IIIa	Pubic fractures and symphyseal diastasis
	Type IIIb	Acetabular fracture without involvement of the pelvic ring
Type IV		Unstable pelvic ring fractures involving the joint
	Type IVa	Straddle fractures involving bilateral superior and inferior pubic rami
	Type IVb	Combined fractures involving the pubic ramus or symphysis and posterior ring
	Type IVc	Fractures or dislocations creating an unstable segment between the anterior ring and acetabulum

Modified Shore Classification and Additional Considerations

• Type IV fractures are high-morbidity and potentially high-mortality injuries that may lead to growth disturbances and deformities.
• In 2012, the classification was modified by Shore with the integration of computed tomography (CT) findings in addition to direct radiographic evaluations (16).
• Type III fractures were further subdivided as:
  • Type IIIa: Stable anterior pelvic ring injuries
  • Type IIIb: Stable injuries involving both the anterior and posterior pelvic ring
• The criteria for stability included:
  • Maintenance of bone alignment under pelvic compression
  • Less than 2 mm displacement of anterior and posterior pelvic fracture fragments on CT imaging (16)
• In older children with closed triradiate cartilage, pelvic fractures are evaluated and managed similarly to adults. In such cases, adult fracture classifications such as Tile, AO, or Young-Burgess can be utilized.

Classification of acetabular fractures:

Watts Classification
Type I	Small fragments associated with hip dislocation
Type II	Generally stable linear fractures associated with pelvic fractures
Type III	Fractures associated with hip joint instability
Type IV	Central fracture-dislocations

Letournel–Judet classification can be used in patients with closed triradiate cartilage (17).

Evaluation and Treatment

• A thorough general trauma examination should be performed. Pelvic asymmetry, limb shortening, rotation, and deformity should be evaluated. Open pelvic fractures must not be overlooked.
• Pelvic stability and hip range of motion should be assessed for potential pelvic and acetabular fractures.
• Although Morel-Lavallée lesions are less common in children than in adults, they may be seen in overweight adolescents (18).
• The pubic rami, iliac wings, and pelvis should be palpated, and tenderness should be evaluated. Stability should be assessed through compression; however, repeated examination should be avoided to prevent disturbing any existing clot formation.
• If an unstable pelvic injury is diagnosed, a pelvic binder or sheet (sling) should be applied to reduce the intrapelvic dead space and provide tamponade.
• The urethral meatus, scrotum, vagina, rectum, and surrounding structures must be examined carefully. A retrograde urethrogram should be performed to evaluate the urinary tract before placing a catheter.
• If a bladder injury is identified, a suprapubic catheter should be placed, but its location should be planned to avoid interfering with any future orthopedic intervention. If a bone fragment is palpated in the rectum during rectal examination, it should be considered an open fracture.
• In skeletally immature patients, conservative treatment methods are generally preferred due to the high remodeling potential of immature bones and cartilage.
• According to the Torode and Zieg classification, Type I avulsion fractures, Type II iliac wing fractures that do not extend to the acetabular roof, and Type III fractures without significant displacement (<2 cm) or instability can be treated conservatively.
• Straddle fractures can also be managed conservatively since they only affect the anterior pelvis. Conservative methods include bed rest and skeletal traction, but early rehabilitation is crucial, and mobilization should begin as early as possible.
• Isometric muscle exercises should be initiated.
• Weight-bearing can begin once callus formation is seen on follow-up radiographs (in small children, callus formation can be seen in as early as two weeks), and full union is typically achieved in 4–6 weeks (19).

Surgical Treatment

• Surgical treatment is recommended in pediatric pelvic fractures when there is pelvic asymmetry greater than 1 cm in order to prevent long-term morbidity (20).
• The surgical group generally includes Torode and Zieg Type IV fractures, which are unstable and displaced (>2 cm). These include:
  • Tile C equivalent fractures involving both the anterior and posterior pelvic ring,
  • Displaced vertical sacral fractures,
  • Sacroiliac dislocations affecting the posterior ring,
  • Displaced iliac wing fractures extending to the sacroiliac joint, and
  • Certain acetabular fractures with displacement.
• In open reduction and internal fixation procedures for children, extra caution should be taken to avoid injury to the physes. Surgical approaches should be minimally invasive with a small footprint, and implants should be removed after fracture healing, without leaving them exposed or uncovered by bone.
• When using external fixation, typically a single pin per side is preferred. Thin pins should be selected based on the child’s bone structure, taking care to avoid injury to growth plates—especially the triradiate cartilage (21).
• The pins are usually placed in a supra-acetabular position (22).

Acetabulum

• Skeletal traction may be applied in displaced fractures to maintain reduction and to relieve pressure on the cartilage.
• In patients with closed triradiate cartilage, acetabular fractures are treated similarly to adult fractures.
• Surgical intervention is indicated in the following cases:
  • If joint surface displacement exceeds 2 mm,
  • If concentric reduction cannot be achieved,
  • If there are intra-articular bone fragments or soft tissue interposition,
  • In cases of open acetabular fractures,
  • Or when the acetabular fracture is associated with a displaced pelvic fracture (23).

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Prognosis

• Complications are rare.
• However, the need for surgical intervention increases after the triradiate cartilage has closed.

Complications

• Mortality is rare and usually results from associated head, abdominal, or thoracic injuries.
• Physeal arrest of the acetabulum may develop following acetabular fractures (reported in <5% of cases). The risk is higher if the physeal injury occurs before the age of 10.
• Limb length discrepancy may develop, particularly in cases with vertical displacement greater than 2 cm.
• Although rare, malunion or nonunion may occur.
• There is a risk of neurovascular injury or heterotopic ossification.
• In acetabular fractures involving the femoral head, there is a potential risk of avascular necrosis (AVN).
• Acetabular fractures may also lead to degenerative joint disease over time.

References:

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19. Musemeche CA, Fischer RP, Cotler HB, Andrassy RJ. Selective management of pediatric pelvic fractures: A conservative approach. J Pediatr Surg 1987 – 22(6):538-40.

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23. Blanchard C, Kushare I, Boyles A, Mundy A, Beebe AC, Klingele KE. Traumatic posterior pediatric hip dislocations with associated posterior labrum osteochondral avulsion: Recognizing the acetabular fleck sign. J Pediatr Orthop 2016 – 36:602-7.