Child abuse is a rare cause of pelvic and acetabular fractures. The diagnosis of a pelvic fracture in infants and very young children, especially those without a reported history of high-energy injury, mandates a thorough investigation by the child protection team and child welfare services.
Associated Injuries with Pelvic and Acetabular Fractures
While death rates in children who sustain pelvic fractures have been reported to be as high as 25%, most series report a mortality rate of 2% to 12% in children.1,5,12–14 Significant hemorrhage that requires blood transfusion occurs in as many as 30% of patients with pelvic fractures80 and is most common in patients who sustain anterior and posterior pelvic ring fractures and those with unstable fractures. However, hemorrhage from pelvic fracture–related vascular injury is the cause of death in less than 1% of children as compared to 3.4% of adults who sustain pelvic ring and acetabular fractures.29,36 One possible explanation for the low rate of hemorrhage relates to the lack of underlying atherosclerotic disease and the increased contractility of children’s smaller arterial vessels, both of which result in greater vasoconstriction after injury.36 In addition, children are injured typically in motor vehicle versus pedestrian accidents and therefore tend to sustain lateral compression forces, as opposed to anterior–posterior forces like adults. Injuries caused by laterally directed forces do not as commonly result in expansion of the pelvic ring or disruption of the sacroiliac joints, generally resulting in less intrapelvic hemorrhage.30
Associated injuries, rather than fractures about the pelvis, are more commonly the causes of morbidity and mortality in children and adolescents who are diagnosed with pelvic ring and acetabular fractures. Between 58% and 87% of children who sustain pelvic fractures have at least one associated injury and many have several.11,20,25,30,69,83 The most common associated injuries are other fractures, particularly of the lower extremities and spine, which are identified in nearly half of children with pelvic fractures.25,80 In one study of 79 children with pelvic fractures, patients with even one additional fracture demonstrated a significantly increased need for other nonorthopedic procedures.97 The incidence of associated traumatic brain injuries varies from as little as 9% to nearly 50%4,11,25,30,52,55,69,83 and clearly is the most important comorbidity that influences outcomes. Associated thoracoabdominal injuries occur at a rate between 14% and 33% in children with pelvic fractures.4,11,14,25,55,80,83 These injuries are second only to head injuries as the primary cause of death in children with pelvic fractures and should be carefully ruled out in children who sustain serious pelvic ring or acetabular injuries.
Other less common injuries have been reported in children who sustain pelvic fractures. Vaginal and rectal lacerations are seen in 2% to 18% of children with pelvic fractures.3,67,89 The incidence of these injuries is much higher in open fractures of the pelvis, a rare injury in children.54 The surgeon must have a high index of suspicion for these types of injuries because early detection, appropriate irrigation and debridement, and repair of lacerations may prevent the development of infection. Genitourinary injuries, most commonly urethral tears and bladder disruptions, are diagnosed in 4% of patients who sustain fractures25 but hematuria has been noted in up to 50% of children with pelvic fractures.11,66,89 Peripheral nerve injury occurs in less than of 3% of children. Posterior displacement of the hemipelvis or the iliac wing from severe pelvic ring disruption can cause tension on the lumbosacral plexus and sciatic nerve as they exit the pelvis.20,67,92 A thorough neurologic examination of the lower extremities, including motor and sensory testing, and assessment of sphincter tone and perianal sensation should be routine in all patients with displaced fractures. Magnetic resonance imaging (MRI) is sometimes helpful to assess the integrity of the lumbosacral plexus. Neurophysiologic studies are indicated in the recovery phase if deficits persist.
Signs and Symptoms of Pelvic and Acetabular Fractures
A full systematic examination of the child with a pelvic or acetabular injury is indicated. The patient will often be first seen in the trauma bay by a multidisciplinary trauma team. Other life-threatening issues may prevent a complete examination immediately, and the patient’s mental status may be impaired. Secondary examinations after the patient is stabilized are critical to identify lesser injuries that may not have been as obvious initially.
Evaluation of a child with a suspected pelvic injury should begin with the assessment of the airway, breathing and circulatory status, as with any polytraumatized patient.95 Careful examination of the head, neck, and spine should be performed to assess for spinal injury and closed head injury. A complete neurovascular examination including peripheral pulses should be part of the initial survey. Documentation of the function of the muscles innervated by the lumbosacral plexus and the skin supplied by its sensory branches is sometimes difficult to fully assess in the acute setting. A secondary survey after stabilization of cardiovascular status and provisional treatment of injuries should include this neurologic evaluation in cooperative patients.
After the primary survey, the evaluation specific to pelvic injuries begins with a complete inspection of the pelvis and perineum to evaluate for lacerations and ecchymosis. The child should be gently log-rolled to facilitate a complete inspection. The Morel-Lavellee lesion (a degloving injury in which the skin and subcutaneous fat is sheared from the underlying muscle, creating a large space where a hematoma can form) may be identified95 (Fig. 25-2). A careful genitourinary evaluation must be performed because of the intimate relationship between the pelvis, bladder, and urethra. Rectal examination has historically been recommended for children with significantly displaced fractures pelvic or if there is any blood in the perineal area. A more recent study, however, revealed that routine use of this examination for all patients may not be necessary, but should be reserved for patients at higher risk for more significant injury.78
Pelvic landmarks including the anterior-superior iliac spine, crest of the ilium, sacroiliac joints, and symphysis pubis should be palpated. Manual manipulation should be performed carefully when needed. The maneuvers are often painful and if performed too vigorously may further displace the fracture or stimulate further intrapelvic bleeding. Pushing posteriorly on the anterior-superior iliac crest produces pain at the fracture site as the pelvic ring is opened. Compressing the pelvic ring by squeezing the right and left iliac wings together also causes pain, and crepitation may be felt if a pelvic fracture is present. Pressure downward on the symphysis pubis and posteriorly on the sacroiliac joints causes pain and possibly motion if there is a disruption. Pain with range of motion of the extremities, especially the hip joint, may indicate articular involvement and other fractures or tendon and ligament injuries.
Avulsion fractures of the pelvis typically result in localized swelling and tenderness at the site of the avulsion fracture. Motion is limited because of guarding, and pain may be mild or marked. In the case of repetitive stress injury, pain and limitation of motion usually are gradually progressive. In patients with ischial avulsions, pain at the ischial tuberosity can be elicited by flexing the hip and extending the knee (straight-leg raising). In this position, as the hip is moved into abduction, the pain increases. Patients may also have pain while sitting or moving on the involved tuberosity.
Imaging and Other Diagnostic Studies for Pelvic and Acetabular Fractures
Following initial stabilization of the child, all multitrauma patients and those with suspected pelvic or acetabular trauma should undergo an anteroposterior (AP) radiograph of the pelvis as part of the initial trauma series. Multiple fractures are often an indication of associated thoracoabdominal or head injuries. Once the primary survey is completed and the patient is stable, region-specific radiographs should be obtained of any area with signs of trauma on secondary assessment.
Additional views, including the inlet and outlet and Judet views are useful for further evaluation of pelvic ring injuries. The inlet view is obtained by directing the x-ray beam caudally at an angle of 60 degrees to the x-ray plate. The inlet view is best for the determination of posterior displacement of a hemipelvis. The outlet view is obtained by directing the x-ray beam in a cephalad direction at an angle of 45 degrees to the x-ray plate. The outlet view best demonstrates superior displacement of the hemipelvis or vertical shifting of the anterior pelvis.91 Internal and external rotation views (Judet or oblique) are primarily obtained when an acetabular fracture is identified.
A number of studies have tried to identify clinical criteria which would effectively rule out the need for any pelvic radiographs in childhood trauma patients.32,43,45 In general, children with no lower extremity fractures, a normal examination of the abdomen and pelvis, and who are alert and neurologically intact without pelvic pain regardless of a high-risk mechanism of injury, are unlikely to have sustained a pelvic fracture. The value of these criteria for avoiding radiation to the pelvis is a noble effort but its efficacy has not yet been established and most polytraumatized children do not meet these criteria.
Computer tomography (CT) scanning is considered to be the best modality to evaluate the bony pelvis, especially at the sacroiliac joint, sacrum, and acetabulum. Most authors agree that CT scanning is indicated if there is doubt about the diagnosis on the plain radiographs or if operative intervention is planned. This imaging modality helps better define the type of fracture, the degree of displacement, and can detect retained intra-articular fragments which can prevent concentric reduction (Fig. 25-3).7,9,27,51,82 This information is crucial for determining the best treatment option and selection of the operative approach.48 Three-dimensional CT reconstructions can give an excellent view of the overall bony fracture pattern but often underestimate the magnitude of cartilaginous fragments, especially of posterior wall fractures in children.71 Many trauma centers routinely obtain CT scans of the abdomen and pelvis looking for visceral injury.
MRI currently has minimal role in evaluation of the acute trauma patient, although this practice may evolve with quicker sequencing and better access. MRI is better than CT in delineating soft tissue injuries, and does not emit ionizing radiation. Cartilaginous structures, such as posterior wall fractures associated with hip dislocations, or nonacute fractures, such as occult stress fractures or avulsion fractures, may be diagnosed more readily with MRI.30,71 An MRI is recommended as an adjunctive imaging study for all pediatric acetabular fractures because MRI discloses the true size of largely cartilaginous posterior wall fragments in children (Fig. 25-4). Radioisotope bone scan is rarely indicated but may be useful for the identification of occult pelvic fractures or other acute injuries in children and adults with head injuries or multiple-system injuries.34,91
In children with avulsions of the pelvis, radiographs will usually show displacement of the affected apophysis. Avulsion injuries affect secondary centers of ossification before the center is fused with the pelvis, primarily in children of ages 11 to 17 years.18,53,88 Comparison views of the contralateral apophysis should be obtained to ensure that what appears to be an avulsion fracture is not in reality a normal adolescent variant. Radiographs of children with delayed presentations of these injuries may demonstrate callus formation and these findings can occasionally mimic a malignant process.
Classification of Pelvic and Acetabular Fractures
Pelvic Fracture Classification
The Torode and Zieg94 classification based on plain radiographs, and its most recent modification based on radiographs and CT scans,51 is the most commonly used classification of pediatric pelvic fractures. To create this classification, the authors reviewed 141 children with pelvic fractures and classified the injuries on the basis of the severity of the fractures as well as their associated prognosis. The classification has type I (avulsion fractures), type II (iliac wing fractures), type III (simple ring fractures), and type IV (ring disruptions). The modified scheme is identical to the earlier scheme but additionally divides type III “stable” simple ring injuries into IIIA (anterior only ring fractures) and IIIB (anterior and posterior ring fractures) (Table 25-1 and Fig. 25-5).51 The morbidity, mortality, and complications are all greatest in the type IV group with “unstable” ring disruptions. This classification does not include acetabular fractures.
TABLE 25-1 Modified Torode and Zieg Classification of Pelvic Fractures in Children
Silber and Flynn81 reviewed radiographs of 133 children and adolescents with pelvic fractures and classified them into two groups: Immature (Risser 0 and all physes open) and mature (closed triradiate cartilage). They suggested that in the immature group, management should focus on the associated injuries because the pelvic fractures rarely required surgical intervention compared to the group with mature pelvises. Fractures in the mature group were best classified and treated according to adult pelvic fracture classification and management principles.7,63,91
Quinby65 and Rang47 classified pelvic fractures in children into three categories: (i) Uncomplicated or mild fractures, (ii) fractures with visceral injury requiring surgical exploration, and (iii) fractures with immediate, massive hemorrhage often associated with multiple and severe pelvic fractures. This classification system emphasizes the importance of the associated soft tissue injuries, but does not account for the mechanism of injury or the prognosis of the pelvic fracture itself. Watts98 classified pediatric pelvic fractures according to the severity of skeletal injury: (a) Avulsion, caused by violent muscular contraction across the unfused apophysis; (b) fractures of the pelvic ring (secondary to crushing injuries), stable and unstable; and (c) acetabular fracture associated with hip dislocation.
Adult Pelvic Fracture Classifications
Pennal et al.60 classified adult pelvic fractures according to the direction of force producing the injury: (a) AP compression, (b) lateral compression with or without rotation, and (c) vertical shear. This classification was modified and expanded by Tile et al. (Table 25-2).94 Burgess et al.7 further modified the Pennal system and incorporated subsets to the lateral compression and AP compression groups to quantify the amount of force applied to the pelvic ring. They also created a fourth category, combined mechanical injury, to include injuries resulting from combined forces that may not be strictly categorized according to the classification scheme of Pennal.
TABLE 25-2 Tile and Pennal Classification of Pelvic Fractures
The Tile classification has been incorporated into the Orthopaedic Trauma Association/AO classification, which is divided into bone segments, types, and groups (Table 25-3).63 The Orthopaedic Trauma Association/AO system classifies pelvic fractures on the basis of stability versus instability, and surgical indications are based on the fracture types. Surgery is rarely indicated for type A fractures, whereas anterior and/or posterior surgical stabilization may be indicated for type B and C fractures. Numerous subtypes are included, and further details are described in the chapter on adult pelvic fractures.
TABLE 25-3 AO/Association for the Study of Internal Fixation Classification of Pelvic Fractures
In general, the basic classifications, (a) mature or immature pelvis and (b) stable or unstable fracture, are very useful for making treatment decisions. Regardless of the classification system that is used, if there is a break in the anterior and posterior pelvic ring, an extremely misshapen pelvis, a displaced posterior ring injury, or a displaced triradiate fracture, the pelvis is unstable.
Acetabular Fracture Classification
Pediatric Classifications. Bucholz et al.6 classified pediatric acetabular fractures based on the Salter–Harris classification (Fig. 25-6). Their classification system is used to help determine the prognosis of a triradiate cartilage injury that may result in a deformity of the acetabulum with growth. The anatomy of the triradiate is such that the superior weight-bearing portion of the acetabulum is separated from the inferior third by the superior arms of the triradiate cartilage. These superior arms are usually the ones involved in a fracture. In the Bucholz classification, a type I or II injury occurs from a traumatic force to the ischial ramus, pubic ramus, or proximal femur resulting in a shearing force through the superior arms of the triradiate cartilage. If there is a metaphyseal bone fragment, this is a type II fracture. A type V injury is a crush injury to the physis.6,45,98 Watts98 described four types of acetabular fractures in children: (i) Small fragments that most often occur with dislocation of the hip, (ii) linear fractures that occur in association with pelvic fractures without displacement and usually are stable, (iii) linear fractures with hip joint instability, and (iv) fractures secondary to central fracture-dislocation of the hip.
Adult Acetabular Fractures
Acetabular fractures in children can also be described similarly to those in adults, which are usually classified by the system of Judet et al.37 and Letournel and Judet.44 A more comprehensive system is the AO fracture classification, which groups all fractures into A, B, and C types with increasing severity. Type A acetabular fractures involve a single wall or column; type B fractures involve both columns (transverse or T-types) and a portion of the dome remains attached to the intact ilium; and type C fractures involve both columns and separate the dome fragment from the axial skeleton by a fracture through the ilium. Both of these classification systems are discussed in more detail in Rockwood and Green’s, Fractures in Adults, Chapter 36, Volume 2.68
Outcome Measures for Pelvic and Acetabular Fractures
Outcome data has been assessed by several functional assessments. A national multicenter study is currently tracking outcomes using the WeeFim functional assessment.58 Other measures used to evaluate the quality of life in trauma patients include the Child Health Questionnaire (CHQ), the Functional Independence Measure, the Impact of Family Scale,76 and the Health Related Quality of Life (HRQOL) scale.75 Preliminary results demonstrate that 6-month functional scores after injury approach baseline levels,58 despite the increased patient and family stress encountered.
PATHOANATOMY AND APPLIED ANATOMY RELATING TO PELVIC AND ACETABULAR FRACTURES
Pelvic and Acetabular Development
The pelvis of a child arises from three primary ossification centers: The ilium, ischium, and pubis. The three centers meet at the triradiate cartilage and fuse at approximately 12 to 14 years of age (Fig. 25-7).59 The pubis and ischium fuse inferiorly at the pubic ramus at 6 or 7 years of age. Occasionally, at approximately the time of fusion of the ischium to the pubis, an asymptomatic lucent area is noted on radiographs in the midportion of the inferior pubic ramus, termed the ischiopubic synchondrosis. It is often bilateral, fuses completely in most children, and may be confused with an acute or stress fracture of the pelvis.
Secondary centers of ossification arise in the iliac crest, ischium, anterior-inferior iliac spine, pubic tubercle, angle of the pubis, ischial spine, and the lateral wing of the sacrum. Secondary ossification of the iliac crest is first seen at age 13 to 15 years and fuses to the ilium by age 15 to 17 years. The secondary ossification center of the ischium is first seen at 15 to 17 years and fuses at 19 years of age, although in some young adults it may fuse as late as 25 years of age. A center of ossification appears at the anterior-inferior iliac spine at approximately 14 years, fusing at 16 years of age.59,98 Knowledge about the location, age of appearance, and fusion of the secondary centers are important in differentiating these centers from fractures and avulsion injuries.
The acetabulum contains the shared physes of the ilium, ischium, and pubis that merge to become the triradiate cartilage. Interstitial growth in the triradiate part of the cartilage complex causes the acetabulum to expand during growth and causes the pubis, ischium, and ilium to enlarge as well. The concavity of the acetabulum develops in response to the presence of a spherical head. The depth of the acetabulum increases during development as the result of interstitial growth in the acetabular cartilage, appositional growth of the periphery of this cartilage, and periosteal new bone formation at the acetabular margin.64 The triradiate cartilage of the acetabulum closes at approximately 12 years of age in girls and 14 years of age in boys.95 At puberty, three secondary centers of ossification appear in the hyaline cartilage surrounding the acetabular cavity. The os acetabuli, which is the epiphysis of the pubis, forms the anterior wall of the acetabulum. The epiphysis of the ilium, the acetabular epiphysis64,98 forms a large part of the superior wall of the acetabulum. The small secondary center of the ischium is rarely seen. The os acetabuli, the largest part, starts to develop at approximately 8 years of age and expands to form the major portion of the anterior wall of the acetabulum; it unites with the pubis at approximately 18 years of age. The acetabular epiphysis develops in the iliac acetabular cartilage at approximately 8 years and fuses with the ilium at 18 years of age, forming a substantial part of the superior acetabular joint surface (Fig. 25-8). The secondary center of the ischium, the smallest of the three, develops in the ninth year, unites with the acetabulum at 17 years, and contributes very little to acetabular development. These secondary centers are sometimes confused with avulsion fractures or loose bodies in the hip joint.
Child Versus Adult Pelvis
As mentioned previously, there are important anatomic differences between the pelvis of a child and that of an adult (Table 25-4). Because of some of these differences, the pediatric pelvis is better able to absorb energy without significant displacement. Minimally displaced fractures and single breaks of the ring are frequently seen in pediatric pelvic fractures, a finding opposed to the traditional concept of a mandatory “double break” in the ring seen in adult fractures.47,59 More importantly, a child may sustain a higher energy injury than suspected from the bony injury, making it crucial that the surgeon be aware that even minor pelvic fractures may be associated with other potentially serious injuries.
TABLE 25-4 Characteristics of the Pediatric Pelvis That Distinguish it from the Adult Pelvis
TREATMENT OPTIONS FOR STABLE PELVIC FRACTURES
Avulsion Fractures (Torode and Zieg Type I)
Of the 268 pelvic avulsion fractures reported in the four largest series,18,21,70,88 50% were ischial avulsions, 23% were avulsions of the anterior-superior iliac spine, 22% were avulsions of the anterior-inferior iliac spine, and 2% were avulsion of the iliac apophysis. Athletes who participate in jumping sports also sustain avulsions of the lesser trochanter from traction by the iliopsoas muscle, injuries that are often reported with pelvic apophyseal avulsion fractures (although more accurately a femur fracture) (Fig. 25-9). Most pelvic avulsion fractures in children heal satisfactorily with nonoperative management including rest, partial weight bearing on crutches for 2 or more weeks, and extremity positioning to minimize muscle stretch. Typically children resume normal activities by 6 to 8 weeks. Two small series of adolescents with pelvic avulsion fractures treated conservatively concluded that nonsurgical treatment was successful in all patients, and all patients returned to preinjury activity levels.18,53 In another series, only 3 of 198 competitive adolescent athletes with pelvic avulsion fractures were treated operatively.70
Others, however, have suggested that nonoperative treatment is associated with a higher incidence of functional disability and inability to return to competitive athletic activity.88 In one long-term follow-up study of 12 patients with ischial avulsions, 8 reported significant reduction in athletic ability and 5 had persistent local symptoms.73 Thus, some controversy exists surrounding the acute management of displaced ischial avulsion fractures. Although many have satisfactory outcomes without surgery, indications for surgical management are not clear nor is the best operative technique established. Most agree that excision of the ischial apophysis is indicated in the setting of chronic pain and disability. Some authors, however, recommend open reduction and internal fixation of those rare acute ischial avulsion fragments displaced more than 1 to 2 cm (Fig. 25-10).46 Operative treatment of the other types of avulsion fractures is rarely indicated.
Indications/Contraindications. Most avulsion fractures may be successfully treated nonsurgically. Significant displacement greater than 1 to 2 cm, persistent pain, or bony prominence that interferes with sitting are all relative indications for surgery.
Ischial Avulsion Fracture
Preoperative planning checklist includes:
2. Fluoroscopic table such as a Jackson table
3. Screw set including 4.5- to 6.5-mm screws with washers
Positioning: prone surgical approach for open reduction and internal fixation of an ischial avulsion fracture.
After appropriate anesthesia, the patient should be placed in a prone position with the hip and knee slightly flexed. An approximately 7- to 10-cm incision is made along the gluteal crease. The inferior edge of the gluteus maximus is identified and elevated. The plane between gluteus maximus and the hamstring muscles is then developed as the gluteus maximus is traced proximally. The bony fragment with the hamstrings attached is identified. Radiographs or C-arm can be used to identify this more clearly if needed. The fragment may be reduced more easily with the hip extended and the knee slightly flexed. After reduction, the fragment is stabilized with cancellous screws, with or without washers. If necessary, additional fixation with suture anchors, cables, or wires may be needed to ensure stability.
After surgery, the patient is permitted to sit up with the hips and knees slightly flexed to decrease stress on the hamstrings. Initially made nonweight bearing, patients may progress to full weight bearing in 3 to 6 weeks. At 12 weeks postoperatively, the patient may resume full activities.
Isolated Iliac Wing Fractures (Torode and Zeig Type II)
Direct trauma may fracture the wing of the ilium, but isolated iliac wing fractures are relatively rare, with a reported incidence of 5% to 14% in children with fractures of the pelvis.66,69,80 However, iliac wing fractures often occur in conjunction with other fractures of the pelvis, and thus the overall incidence of iliac wing fractures is significantly higher than the incidence of isolated iliac wing fractures.
The patient with an iliac wing fracture typically presents with pain that is located over the wing of the ilium. On examination, motion at the fracture site may be noted. A painful Trendelenburg gait may be present because of spasm of the hip abductor muscles. A fracture of the wing of the ilium may be overlooked on an underexposed radiograph of the pelvis where the ilium is poorly seen as a large area of radiolucency. Displacement of the fracture usually occurs laterally, but it may occur medially or proximally. Severe displacement is rare because the iliac wing is tethered by the abdominal muscles and the hip abductors.
Treatment of an iliac wing fracture is mostly dictated by the associated injuries. Symptomatic treatment is all that is necessary for most iliac wing fractures and typically includes pain management and partial weight bearing on crutches until the symptoms are completely resolved. Regardless of comminution or displacement, these fractures usually unite without complications or sequelae (Fig. 25-11). Open reduction with screws or plating is rarely indicated except for large fragments with severe displacement.
Other Stable Fractures
Fractures of the Sacrum
Sacral fractures constitute a small fraction of pelvic fractures reported in children. Rieger and Brug69 reported two sacral fractures and seven sacroiliac fracture-dislocations in their 54 patients. Sacral fractures are probably more common than reported, but because they are obscured by the bony pelvis and the soft tissue shadows of the abdominal viscera, and because they are rarely displaced, they may be overlooked. Nine of 166 patients (5.4%) with pelvic fractures in the series by Silber et al.83 had associated sacral fractures, none with nerve root involvement. There are two general types of sacral injuries. Spinal-type injuries may present as crush injury with vertical foreshortening of the sacrum or horizontal fractures across the sacrum. These fractures may be significant because they may damage the sacral nerves, resulting in the loss of bowel and bladder function. Alar-type injuries are generally vertical fractures through the ala or foramina. These fractures are significant in that they may represent the posterior break of the double ring fracture.
The presence of sacral fractures may be suggested clinically. Pain and swelling may be present, usually over the sacrum. Because digital rectal examination in pediatric trauma patients has a high false-negative rate, its usefulness is questionable and is not routinely performed in all centers.79 When the examination is performed in patients with sacral fractures, fracture fragments, rectal tears, and urethral disruptions may sometimes be identified.
Sacral fractures are difficult to see on plain radiographs. The fracture can be oblique, but most are transverse with minimal displacement and occur through a sacral foramen, which is the weakest part of the body of the sacrum. Minimal offset of the foramen or offset of the lateral edge of the body of the sacrum is an indication of sacral fracture. Lateral views are helpful only if there is anterior displacement, which is rare. A 35-degree caudal view of the pelvis may reveal a fracture of the body of the sacrum. CT and MRI scans are best in the identification of sacral fractures missed on plain radiographic images.24,27,77 In one study comparing radiographs with CT scans in a consecutive series of 103 pediatric trauma patients with pelvic radiographs and pelvic CT scans, only three sacral fractures were identified with plain radiographs whereas nine sacral fractures were identified with CT (Fig. 25-12).27 Sacral fractures are generally managed expectantly and treated symptomatically. In rare cases, pinched sacral nerve roots may need to be decompressed.
Fractures of the Coccyx
Many children fall on the tailbone and have subsequent pain. The possibility of fracture must be entertained. Because the coccyx is made up of multiple small segments, is obscured by soft tissue, and naturally has a crook in it, it is difficult to determine on radiographs whether a coccygeal fracture has occurred, especially in a child. These fractures rarely have associated injuries. Clinically, patients describe immediate, severe pain in the area of the coccyx. Pain on defecation may be present as well as pain on rectal examination. Because radiographic identification is difficult, the diagnosis should be made clinically by digital rectal examination. Exquisite pain may be elicited, and an abnormal mobility of the coccygeal fragments may be noted. Acute symptoms may abate in 1 to 2 weeks, but may be remarkably persistent. The differential diagnosis is between fracture and coccydynia. Lateral radiographs of the coccyx with the hips flexed maximally may reveal a fracture (Fig. 25-13). Apex posterior angulation of the coccyx is a normal variant, and should not be falsely interpreted as a fracture or dislocation. CT and MRI scanning may be helpful in differentiating between physeal plates and fracture lines.13 Treatment is symptomatic only and consists of activity restriction and a pressure-relieving cushion for sitting with an expectation of resolution in 4 to 6 weeks for acute fractures. In our experience, however, some patients have chronic pain that persists for several months, probably better described by the diagnosis “coccydynia.” Symptomatic treatments, injections, and coccygectomy are some management options with good results in adolescents.26
Stress Fractures of the Pubis or Ischium
Stress fractures are rare in small children, but they do occur in adolescents and young adults from chronic, repetitive stress to a bony area or during the last trimester of pregnancy. Stress fractures of the pubis are likewise uncommon, but a small series of stress fractures, primarily in the inferior pubic rami, has been reported. Chronic symptoms and pain increased by stress may be noted in the inferior pubic area. Radiographs may show no evidence of fracture for as long as 4 to 6 weeks, and then only faint callus formation may be visible; however, MRI or a technetium bone scan may reveal increased uptake early.34 Treatment should consist of avoiding the stressful activity and limited weight bearing for 4 to 6 weeks.
The ischiopubic synchondrosis usually closes between 4 and 8 years of age.40 The radiographic appearance of the synchondrosis at the ischiopubic junction may be misinterpreted as a fracture. Caffey and Ross8,42 noted that bilateral fusion of the ischiopubic synchondrosis is complete in 6% of children at 4 years of age and in 83% of children at 12 years of age. The presence of the synchondrosis itself is common and usually asymptomatic. Bilateral swelling of the synchondrosis was also noted in 47% of children at age 7 years. Irregular ossification and clinical swelling at the ischiopubic synchondrosis has been called ischiopubic osteochondritis or van Neck disease. If this syndrome is noted in a child older than 10 years of age, it should be treated as a repetitive stress injury (Fig. 25-14).