14.8 Injuries of the pelvis and hip in children

Paediatric hip fractures are rare, comprising less than 1% of all paediatric fractures. These severe injuries frequently have complications that have lifelong significance for the patient.

The proximal femoral physis contributes the majority of metaphyseal growth in the neck of the femur and to a lesser degree to the appositional growth of the femoral head. The trochanteric apophysis contributes mostly to the appositional growth of the greater trochanter and to a lesser degree to metaphyseal growth.

The metaphyseal and epiphyseal blood supplies of the proximal femur in children are functionally separate until physeal closure (usually at age 14–17 years) except for small penetrating vessels. The terminal branch of the medial femoral circumflex artery, the lateral epiphyseal artery, supplies the majority of the femoral head from childhood into adult life. The anterior portion of the femoral head receives a significant portion of its blood supply from branches of the lateral femoral circumflex artery until age 5–6 years. The obturator artery system supplies a minor contribution to the femoral head through the artery of the ligamentum teres. The dominance of the medial femoral circumflex arterial system makes the child’s femoral head vulnerable for avascular necrosis following femoral neck fracture. Fractures closer to the physis and fractures with greater displacement are at greater risk for arterial disruption and subsequent necrosis.

The most widely utilized classification of paediatric hip fractures is based on the anatomical location of the fracture. The classification divides children’s hip fractures as follows (Figure 14.8.1).

The patient presenting with a displaced proximal femoral fracture will show a shortened, externally rotated extremity with pain on movement. The symptoms of pain in the hip along with restricted motion should alert the physician to the possibility of a non-displaced fracture.

An anteroposterior pelvis radiograph is standard for the evaluation of a child involved in a major trauma. If a hip fracture is suspected on history/examination or seen on the screening film, further plain radiographs (anteroposterior and lateral views of the hip) are recommended.

Magnetic resonance imaging (MRI) may be helpful in delineating an occult fracture. Ultrasound followed by hip aspiration with or without arthrography can be used to differentiate between fracture and other potential pathology such as hip joint sepsis or synovitis. The aspiration should yield bloody fluid in the presence of fracture.

Controversy exists over the need for routine anterior capsulotomy and there are differing opinions on whether this procedure decreases the incidence of avascular necrosis.

These fractures can be managed with closed reduction and application of a hip spica cast with the hip in an abducted and externally rotated position. An anatomical reduction must be achieved unless the child is under the age of 2 years, when remodelling of the femoral neck can be anticipated (Figure 14.8.2). In children over the age of 2, if an anatomical reduction cannot be achieved closed, the fracture should be stabilized with percutaneous pins or cannulated screws. Smooth pins are preferred over threaded pins or screws, especially in children with significant growth remaining. If an anatomical reduction cannot be obtained by closed means, open reduction through an anterolateral approach should be performed followed by insertion of pins or cannulated screws. Fixation should be protected with a postoperative hip spica cast.

Type II fractures have been treated with closed reduction and casting with some success but this should be reserved for only truly non-displaced type II fractures. Most of these fractures should be treated operatively. Closed reduction, or an open reduction if an anatomical reduction cannot be obtained closed, is followed by fixation with two to three lag screws placed into the femoral neck short of the proximal femoral physis (Figure 14.8.3). Cannulated or solid screws ranging from 4.0–6.5mm are appropriate depending on the size of the child. Fixation may be supplemented with a hip spica cast.

Non-displaced type III fractures can be treated by application of a hip spica cast depending on the age of the patient. Close follow-up in the cast is mandatory to avoid loss of reduction and resultant coxa vara deformity. Operative treatment is preferred for most type III cervicotrochanteric fractures. The fixation of choice are lag screws inserted short of the proximal femoral physis unless physeal closure has occurred or is imminent in which case the physis may be crossed. Open reduction must be performed if a satisfactory reduction cannot be obtained closed. A supplementary hip spica cast may be used.

Some intertrochanteric fractures, particularly in younger patients, can be treated with skin or skeletal traction followed by application of a hip spica cast. Close follow-up is necessary to detect loss of reduction. Polytrauma patients, those who fail to obtain an adequate reduction in traction or those who lose reduction, and most patients older than 6 years of age should be managed with operative fixation. Closed reduction is frequently possible, but if a satisfactory reduction cannot be obtained, open reduction and internal fixation is required. In children under the age of 6 years, fixation is with threaded pins or lag screws. If the child is 6–12 years of age, lag screws are recommended or if the patient is large enough a paediatric sliding hip screw can be placed short of the proximal femoral physis (Figure 14.8.4). Children older than 12 years of age should be managed with a sliding hip screw or an angled blade plate short of the physis. Patients treated with only pin or screw fixation need supplemental immobilization in a hip spica cast.

The results of treatment of type I fractures are generally poor secondary to the frequent development of complications such as avascular necrosis, non-union, and premature physeal closure. Many type I fractures are accompanied by dislocation of the head from the acetabulum and dislocation further worsens the prognosis.

The results of treatment for type II fractures is more favourable than type I but significant numbers will have complications, such as premature proximal femoral physeal closure, non-union, and avascular necrosis Urgent open reduction and internal fixation with capsulotomy may favourably influence the results, but it appears that the initial displacement of the fracture is the greatest determinant in the development of avascular necrosis.

Improved results with fewer complications can be expected with type III fractures, although avascular necrosis (30% of cases), non-union, and coxa vara can all occur.

Avascular necrosis and premature physeal closure are rare in type IV fractures. The quality of reduction obtained will be the largest determinant of the incidence of malunion which is the most common problem following intertrochanteric fractures. Non-anatomical reductions and non-operatively treated fractures have a greater likelihood of developing coxa vara.

The rate of avascular necrosis depends on the fracture type. Between 80 and 100% of type I fractures (depending on whether the head is dislocated), 60% of type II fractures, and 30% of type III fractures develop this severe complication. Three patterns of avascular necrosis following paediatric hip fractures have been described (Figure 14.8.5).

The initial fracture displacement is the critical determinant for the development of necrosis. Patients with avascular necrosis fare poorly at long-term follow-up. There are no predictable treatments for avascular necrosis other than hip arthrodesis or arthroplasty when the patient’s symptoms become severe enough.

Non-union is more common in neck than intertrochanteric fractures. If non-union is associated with varus deformity, valgus osteotomy is indicated. If the neck–shaft alignment is normal, bone grafting and internal fixation is indicated. This complication can be minimized by obtaining good fixation at the time of initial treatment.

Up to 65% of proximal femoral fractures are complicated by physeal closure. The proximal femoral physis contributes 30% to overall femoral growth and limb-length discrepancy may be more than 2cm.

The use of internal fixation decreases the incidence and severity of coxa vara.

Historically, treatments for paediatric hip fractures have nearly always been non-operative. More recent series in which operative treatment has been more prevalent, have shown decreased incidence of complications and improved results. Future treatment should focus on anatomical reductions of these fractures and utilization of open approaches if necessary.

Although the incidence is estimated to be higher than paediatric hip fractures, traumatic hip dislocation in children is rare and comprises about 5% of paediatric dislocations. Posterior hip dislocations comprise the majority of dislocations, although anterior dislocations have been described.

Patients with a high-energy mechanism of injury must be closely examined and monitored for associated injuries involving the chest, abdomen, and head.

The dislocation can be generally classified into anterior (obturator, anterosuperior, anteroinferior) or posterior.

A patient presenting with an anterior hip dislocation will have abduction, external rotation, and extension at the hip while a posterior dislocation will present with adduction, internal rotation, and flexion. Function of the sciatic nerve should be documented prior to reduction of the hip.

Any child who has sustained high-energy trauma or has suggestive physical findings, should have an anteroposterior pelvic radiograph. If a fracture of the acetabulum is seen or suspected, Judet 45-degree oblique radiographs should be obtained. If a concentric reduction is not achieved (suggested by widening of the hip joint space on postreduction films) a postreduction computed tomography (CT) scan or MRI is indicated to evaluate for incarcerated osteocartilaginous fragments or soft tissues.

Closed reduction of the hip should be performed in the emergency department if adequate sedation can be achieved, otherwise the reduction should be performed in the operating room under general anaesthesia. The reduction must be done on an urgent basis, ideally within the first 6h after injury. If the hip cannot be reduced closed or postreduction studies reveal a non-concentric reduction, an open reduction must be performed. A posterior approach is indicated for a posterior dislocation while an anterior approach is best for an anterior dislocation. The obstacle to reduction is usually a button hole through the capsule, interposed piriformis tendon, or osteocartilaginous fragments.

Young children and those with questionable compliance should be managed in a one and one half hip spica cast. Older children can be managed with mobilization when the hip is comfortable with crutch ambulation for 3–4 weeks.

Traumatic hip dislocations without associated fractures generally do well. Higher-energy injuries, associated fractures, and delayed reduction all contribute to a higher number of poor results.

The incidence of avascular necrosis following traumatic hip dislocation in children is 10% or less and is more common in older children. Reduction of the hip as soon as possible and preferably within 6h of injury should remain the goal to minimize the chances of this complication.

Injury to the sciatic nerve or its peroneal division is not uncommon. Unfortunately not all of these nerves recover completely and the rate of recovery may not be better than that reported for adults which is only in roughly one-third of cases.

Early degenerative disease after hip dislocation is usually secondary to necrosis. Osteoarthritis is felt to be infrequent in the absence of avascular necrosis, but no good long-term studies on children’s hip dislocations have been done.

Recurrent dislocation following traumatic hip dislocation in a patient without a hyperlaxity syndrome such as Down syndrome is quite rare. Plication of the posterior capsule should be reserved for patients who fail 6 weeks of hip spica casting after their first episode of recurrent dislocation.

Pelvic fractures in children are uncommon. The majority are stable injuries and acetabular fractures are rare.

The anatomy of the pelvis in children differs from the adult secondary to the presence of the triradiate acetabular cartilage complex and the many extra-articular apophyses. The biomechanical properties of the child’s pelvis are also different. The child’s pelvis is more malleable, absorbs more energy prior to fracture, and therefore requires higher-energy trauma to produce a fracture. Even innocent fractures may be caused by high forces and have a significant incidence of associated injuries. The more ductile nature of paediatric bone and the increased elasticity of the joints allows for a single break in the pelvic ring in contrast to the adult where a double break is almost always present. Injury to the triradiate cartilage can result in growth arrest and a deficient acetabulum.

Because of the high-energy trauma required to produce a paediatric pelvic fracture, associated injuries are common. Mortality rates of 9–18% have been reported. Mortality and morbidity are highly related to associated injuries to the head, chest, and abdomen. Genitourinary injuries including urethral injury, bladder rupture, and vaginal lacerations occur more commonly in the more severe pelvic injuries.

Significant haemorrhage from paediatric pelvic fractures is not as common as in adults. This indicates that other sources for excessive bleeding should be sought. Management of haemorrhage from the pelvic fracture requires resuscitation, stabilization of the pelvis, and, if necessary, selective arteriography and embolization.

The system of Key and Conwell is commonly used and will be the classification system further described here (Table 14.8.1).

Although the system of Key and Conwell includes acetabular fractures, the classification system of Judet and Letournel devised for adult acetabular fractures should also be applied to delineate further the extent of the injury and treatment needed.

Paediatric pelvic ring injuries most commonly result from motor vehicle collisions or falls from a height. Pelvic injuries sustained in sports competition are usually avulsion fractures. Anterior muscle contraction with the hip in extension and the knee in flexion can result in avulsion fracture of the anterosuperior or anteroinferior iliac spine, whereas avulsion fracture of the ischial tuberosity occurs after maximal contraction of the hamstrings. The patient will complain of pain localized to the area of the injured apophysis.

A thorough general physical examination must be performed secondary to the high incidence of associated injuries. Once the general examination is complete and resuscitation initiated, the bony pelvic landmarks are evaluated for asymmetry and the stability of the pelvis is tested. Range of both hips should be tested. If a pelvic fracture with significant displacement of the rami is present, digital vaginal and rectal examination under sedation or general anaesthesia should be performed to rule out occult open fracture. The neurovascular examination must carefully assess the sciatic, femoral, and obturator nerves, and lumbosacral plexus.

Pelvic ring fractures should be evaluated with an anteroposterior pelvic radiograph as well as 40-degree caudad inlet–40-degree cephalad outlet pelvic views. If an acetabular fracture is present, Judet 45-degree oblique views should be obtained. If further detail on an acetabular, sacral, or sacroiliac joint injury is needed a CT scan is the study of choice and the common use of CT in trauma assessment may eliminate the need for pelvic radiographs in some cases.

Initial management of the child with a pelvic fracture is directed at haemodynamic resuscitation and treatment of associated life-threatening injuries. Although massive haemorrhage from pelvic fractures is uncommon in children, if an alternative source for blood loss cannot be found, pelvic external fixation to decrease the pelvic volume and control fracture movement and selective angiography with embolization is indicated. Provisional stabilization of the injured pelvis with a pelvic binder has decreased the need for acute external fixation.

Avulsion fractures about the pelvis require rest and hip positioning to decrease stretch on the involved muscle group. A short period of crutch ambulation with protected weight bearing may be required. Operative intervention is reserved for fractures which result in symptomatic non-union. The results of conservative treatment are generally good.

The plasticity of paediatric bone allows single ramus fractures to occur. These fractures are the most common pelvic fractures in children but are a result of higher-energy trauma than the ramus fractures seen in adults. Isolated pubic or ischial ramus fractures should be treated with bed rest followed by progressive ambulation when symptoms subside.

Fractures of the iliac wing often are accompanied by other fractures in the pelvis which may dictate the treatment required. The isolated iliac wing fracture can be treated with bed rest until comfortable with the hip abducted to relieve stretch on the hip abductor muscles. Once symptoms subside, a programme of progressive weight bearing is followed.

Fractures of the sacrum or coccyx should be treated by ambulation with progressive weight bearing as pain allows. Manual reductions should be avoided since reduction is often lost and there is a risk of rectal tearing with the technique of reduction during digital rectal examination.

The elasticity of the child’s sacroiliac joints and symphysis pubis allow for fractures which constitute a single break in the pelvic ring. Single breaks in the pelvic ring usually have minimal or no displacement. Although single breaks in the pelvic ring are stable and often look benign, the physician must remember that significant energy is required to produce these fractures, and associated injuries are not uncommon and must not be missed.

Fracture of the superior and inferior pubic rami on the same side, symphysis disruption, or fracture of the pubis near the symphysis constitute a break in the pelvic ring. These patterns are stable and require only short-term bed rest followed by protected, progressive weight-bearing on the affected side (Figure 14.8.6).

If significant symphysis displacement is present there must be posterior injury at the anterior sacroiliac joint. Widely displaced (over 3cm) symphysis disruptions of the ‘open book’ type are rotationally unstable injuries. Some authors feel the symphysis should be reduced with either external fixation or internal fixation with a plate. Plating is particularly efficacious if laparotomy is performed for abdominal injuries. Some of these disruptions will partially reduce spontaneously during conservative treatment. There is insufficient data about which disruptions will benefit from surgical reduction.

Double breaks in the pelvic ring are less common than single breaks. They are inherently unstable and usually the result of higher-energy trauma than single breaks. Associated injuries are common.

In double vertical fractures of the pubic rami (straddle fracture) there is often significant superior displacement of the free floating fragment created by the fracture of the bilateral superior and inferior pubic rami. This fracture does not involve the weight-bearing portion of the pelvis and does not require reduction via manipulation or traction. The fracture will usually heal and remodel even when significant displacement is present. Bed rest as necessary for comfort followed by progressive crutch ambulation.

Fracture of the ipsilateral pubic rami with ipsilateral/contralateral fracture of the ilium or dislocation/subluxation of the sacroiliac joint (Malgaine fracture) is a more severe injury. If significantly displaced, similar to adults, these injuries are commonly treated with reduction and internal fixation of the unstable hemipelvis. There are no good studies to determine how much displacement will lead to a poor outcome without being reduced and fixed. To avoid significant deformities more than 1cm of displacement of the posterior pelvic ring should be considered for surgery.

Injury to the triradiate cartilage can cause acetabular growth disturbance which should always be considered in paediatric acetabular fractures.

Small posterior wall fractures that do not result in hip joint instability can be treated with bed rest followed by protected ambulation. Since these usually occur with hip dislocation, the main goal of treatment is to ensure a congruent reduction of the hip.

Skeletal traction can be utilized to obtain reduction of paediatric acetabular fractures. If an adequate reduction (less than 2mm) can be obtained, traction can be used as definitive treatment. However, more frequently children with displaced acetabular fractures through the superior part of the acetabulum or through the triradiate cartilage are treated with open reduction and internal fixation using approaches similar to those used in adults.

Avulsions of the anterosuperior or anteroinferior iliac spine do well with rest and conservative treatment followed by a progressive strengthening programme prior to return to sport. Results of treatment of ischial spine avulsions have not been quite as predicable since persistent symptoms at the site are possible.

Single ramus fractures heal reliably. Despite the common presence of comminution or wide displacement fractures of the iliac wing, whether isolated or combined with other fractures, heal with conservative therapy and residual symptoms are rare.

Sacrum and coccyx fractures in children heal without long-term impairment in contrast to the frequent persistent symptoms seen in adults.

Fractures of two ipsilateral rami, isolated subluxation of the pubic symphysis, and fracture near the pubic symphysis can be expected to have excellent results with a short period of bed rest and progressive protected weight bearing. Isolated fracture near the sacroiliac joint or subluxation of the sacroiliac joint should result in good function after conservative treatment.

The results of double breaks in the pelvic ring are not as encouraging as those of single breaks in the ring. This is largely related to the energy of the injury and associated injuries. There is higher morbidity and mortality related to associated genitourinary, neurological, vascular, and abdominal injuries. Straddle fractures generally heal well without sequelae when treated conservatively. Operative treatment to prevent permanent deformity may be chosen particularly in older children

Conservative treatment of non-displaced acetabular fractures and fractures that reduced acceptably in traction can be good. Poor results are seen in those with non-congruent reductions and type V Salter–Harris triradiate injuries. Operative treatment of displaced transverse fractures of the acetabulum in children can lead to excellent outcomes if a satisfactory reduction is obtained.

Many of the complications of paediatric pelvic fractures are related to concomitant injuries to the head, chest, abdomen, long bones, and genitourinary system.

Delayed union and non-union may occur. Non-unions of the rami are frequently asymptomatic. If symptomatic non-union is present, open reduction and internal fixation and bone grafting are appropriate treatments.

Malunion of pelvic fractures may occur including limb-length discrepancy secondary to cephalad displacement of the hemiopelvis. Malunion can be prevented by obtaining and maintaining adequate reduction of the fracture.

Injury to the triradiate cartilage is a rare complication of acetabular injury which may result in premature closure of the physis and resultant acetabular dysplasia. Classifying triradiate injuries can be difficult, especially in type V injuries which are often not detected until physeal growth abnormality is present. Patients with documented or suspected triradiate injury need long-term follow-up to assess for the development of acetabular dysplasia. If dysplasia is seen consideration should be given to acetabular osteotomy or bar resection to prevent subluxation or degenerative changes.

Incongruity of the acetabulum following acetabular fracture can lead to osteoarthritis of the hip. This complication can best be prevented by accurate reduction of the acetabular fracture utilizing open reduction and internal fixation when necessary.

Paediatric pelvic fractures are usually secondary to high-energy trauma and carry a high risk of associated injury. The treating physician must be aware of this potential and look for other injuries when a pelvic fracture is seen. The majority of pelvic fractures in children can be treated non-operatively with the exception of widely displaced ring fractures and displaced acetabular fractures.