PEDIATRIC HIP

PEDIATRIC HIP FRACTURES

Epidemiology

Hip fractures are rare in children, occurring less than 1% as often as in adults.

Anatomy

Ossification (Fig. 47.1)

• Proximal femur: week 7 in utero

• Proximal femoral epiphysis: ages 4 to 8 months

• Trochanter: 4 years

   

   

   

The proximal femoral epiphysis fuses by age 18 years, the trochanteric apophysis by ages 16 to 18 years.

The proximal femoral physis contributes significantly to metaphyseal growth of the femoral neck and less to primary appositional growth of the femoral head. Thus, disruptions in this region may lead to architectural changes that may affect the overall anatomic development of the proximal femur.

The trochanteric apophysis contributes significantly to appositional growth of the greater trochanter and less to the metaphyseal growth of the femur.

Blood is supplied to the hip by the lateral femoral circumflex artery and, more importantly, the medial femoral circumflex artery. Anastomoses at the anterosuperior portion of the intertrochanteric groove form the extracapsular ring. Ascending retinacular vessels go to the epiphysis (Fig. 47.2).

By 3 or 4 years of age, the lateral posterosuperior vessels (branches of the medial femoral circumflex) predominate and supply the entire anterolateral portion of the capital femoral epiphysis.

Vessels of the ligamentum teres contribute little before age 8 years and approximately 20% in adulthood.

Capsulotomy does not damage the blood supply to the femoral head, but violation of the intertrochanteric notch or the lateral ascending cervical vessels can render the femoral head avascular.

Mechanism of Injury

Axial loading, torsion, hyperabduction, or a direct blow can result in a hip fracture. Severe, direct trauma (e.g., motor vehicle accident) accounts for 75% to 80% of pediatric hip fractures.

Pathologic: Fracture occurs through bone cyst or fibrous dysplasia; tumors account for the remainder.

Stress fractures: These are uncommon.

Clinical Evaluation

The patient typically presents with a shortened and externally rotated lower extremity.

Range of hip motion is painful with variable crepitus.

Swelling, ecchymosis, and tenderness to palpation are generally present over the injured hip.

A careful neurovascular examination should be performed.

Radiographic Evaluation

Anteroposterior (AP) views of the pelvis and a cross-table lateral view of the affected hip should be obtained, with the leg extended and internally rotated as far as is tolerable by the patient.

Developmental coxa vara should not be confused with hip fracture, especially in patients <5 years of age. Comparison with the contralateral hip may aid in the distinction.

Computed tomography may aid in the diagnosis of nondisplaced fractures or stress fractures.

A radioisotope bone scan obtained 48 hours after injury may demonstrate increased uptake at the occult fracture site.

Magnetic resonance imaging may detect occult fractures within 24 hours of injury.

Classification

Delbert Classification of Pediatric Hip Fractures (Fig. 47.3)

Type I: Transepiphyseal fracture

• 8% of pediatric hip fractures

• Incidence of osteonecrosis approaches 100%, especially if associated with a hip dislocation

• End of spectrum of slipped capital femoral epiphysis; consider hypothyroidism, hypogonadism, and renal disease

• In newborns, differential diagnosis includes development dysplasia of the hip (DDH)

  and septic arthritis

  Type II: Transcervical fracture

• 45% of pediatric hip fractures (most common type)

• 80% are displaced

• Osteonecrosis in up to 50% of cases

  Type III: Cervicotrochanteric fracture

• 30% of pediatric hip fractures

• More common in children than in adults

• Rate of osteonecrosis of 20% to 30%

  Type IV: Intertrochanteric fracture

• 10% to 15% of pediatric hip fractures

• Fewer complications than in other hip fractures because vascular supply is more abundant

   

  Treatment

  Type I: Closed reduction with pin fixation is indicated, using partially threaded pins in an older child and smooth pins in a younger child. Open reduction and internal fixation may be necessary if the fracture is irreducible by closed methods.

  Type II: Nondisplaced: The choice is abduction spica cast versus in situ pinning; these fractures may go on to coxa vara or nonunion.

  Displaced: Closed reduction and pinning (open reduction if necessary) are indicated; transphyseal pinning should be avoided.

  Type III: Nondisplaced: Traction is indicated and then spica cast versus immediate abduction spica versus in situ pinning.

  Displaced: Open reduction and internal fixation are recommended, with avoidance of transphyseal pinning.

  Type IV: Depends on age and size of patient. Two to 3 weeks of traction are indicated and then abduction spica for 6 to 12 weeks is indicated for nondisplaced fractures. Open reduction and internal fixation may be necessary for unstable fractures or if one is unable to achieve or maintain a closed reduction.

  Complications

Osteonecrosis: The overall incidence is 40% after pediatric hip fracture. This is directly related to initial fracture displacement and fracture location. Some surgeons report evacuation of the intracapsular hematoma to reduce the potential of osteonecrosis. Ratliff described three types (Fig. 47.4):

Type I: Diffuse, complete head involvement, and collapse; poor prognosis (60%)

Type II: Localized head involvement only; minimal collapse (22%)

Type III: Femoral neck involved only; head sparing (18%)

Premature physeal closure: The incidence is ≤60%, with increased incidence with pins penetrating the physis. It may result in femoral shortening, coxa vara, and short femoral neck. The proximal femoral epiphysis contributes to only 15% of growth of the entire lower extremity. The presence of premature physeal closure in association of osteonecrosis may result in significant leg length discrepancy.

Coxa vara: The incidence is 20%, usually secondary to inadequate reduction. Open reduction and internal fixation are associated with a reduced incidence of coxa vara.

Nonunion: The incidence is 10%, primarily owing to inadequate reduction or inadequate internal fixation. It may require valgus osteotomy with or without bone graft to achieve union.

TRAUMATIC DISLOCATION OF THE HIP

Epidemiology

More common than hip fractures.

Bimodal distribution: The incidence is greater between 2 and 5 years, owing to joint laxity and soft pliable cartilage, and between 11 and 15 years of age as athletic injuries and those associated with vehicular trauma become more common.

Posterior dislocations: These occur 10 times more frequently than anterior dislocations.

Mechanism of Injury

Younger patients (age <5 years): These injuries may occur with relatively insignificant trauma such as a fall from a standing height.

Older patients (age >11 years): These injuries tend to occur with athletic participation and vehicular accidents (bicycles, automobiles, etc.). In this age group, there is a higher association with acetabular fractures.

Posterior dislocations are usually the result of an axial load applied to a flexed and adducted hip; anterior dislocations occur with a combination of abduction and external rotation.

Clinical Evaluation

In cases of posterior hip dislocation, the patient typically presents with the affected hip flexed, adducted, and internally rotated. Anterior hip dislocation typically presents with extension,

abduction, and external rotation of the affected hip.

A careful neurovascular examination is essential, with documentation of integrity of the sciatic nerve and its branches in posterior dislocations. Femoral nerve function and limb perfusion should be carefully assessed in anterior dislocations. This examination should be repeated after closed reduction.

Ipsilateral femur fracture often occurs and must be ruled out prior to hip manipulation.

Radiographic Evaluation

AP views of the pelvis and a lateral view of the affected hip should be obtained. Pain, swelling, or obvious deformity in the femoral region is an indication for femoral radiographs, to rule out associated fracture.

Fracture fragments from the femoral head or acetabulum are typically more readily appreciated on radiographs obtained after reduction of the hip dislocation because anatomic landmarks are more clearly delineated. Depending on age, fracture fragments may not be visible on plain radiographs or computed tomography (CT).

Following reduction, CT should be obtained to delineate associated femoral head or acetabular fracture, as well as the presence of interposed soft tissue.

Classification

Descriptive

Direction: Anterior versus posterior

Fracture-dislocation: Fractures to the femoral head or acetabulum

Associated injuries: Presence of ipsilateral femur fracture, etc.

Treatment

Nonoperative

Closed reduction using conscious sedation may be performed for patients presenting less than 12 hours after dislocation.

Skeletal traction may be used for reduction of a chronic or neglected hip dislocation, with reduction taking place over a 3- to 6-day period and continued traction for an additional 2 to 3 weeks to achieve stability.

Operative

Dislocations more than 12 hours old may require reduction with the patient under general anesthesia. Open reduction may be necessary, if irreducible, with surgical removal of interposing capsule, inverted limbus, or osteocartilaginous fragments.

Open reduction is also indicated in cases of sciatic nerve compromise in which surgical exploration is necessary.

Hip dislocations associated with ipsilateral femoral shaft fractures should initially be addressed

with reduction of the dislocation under general anesthesia. If manipulative closed reduction is unsuccessful, skeletal traction may be applied to the trochanteric region to allow control of the proximal fragment. Internal or external fixation of the femoral shaft fracture may then be performed. Occasionally, operative fixation of the femoral shaft fracture is necessary to achieve stable reduction of the hip.

Hip stability should be assessed intraoperatively. Isolated dislocations are usually stable.

Postoperatively, the patient should be placed in skeletal traction or spica cast for 4 to 6 weeks if hip stability is in question.

Complications

Osteonecrosis (8% to 10%): decreased incidence with patient age <5 years and an increased incidence with severe displacement and delay in reduction.

Epiphyseal separation: Traumatic physeal injury may occur at the time of dislocation and may result in osteonecrosis or growth arrest.

Recurrent dislocation: In traumatic cases, it may result from absolute capsular tears or capsular attenuation. It is also associated with hyperlaxity or congenital syndromes (e.g., Down syndrome). It may be addressed with surgical “tightening” of the hip, with capsular repair, or with plication as well as spica casting for 4 to 6 weeks postoperatively.

Degenerative joint disease: This may result from nonconcentric hip reduction secondary to trapped soft tissue or bony fragments or from the initial trauma. Articular incongruity secondary to associated femoral head or acetabular fracture, or entrapped osteochondral fragments, may exacerbate degenerative processes.

Nerve injury (2% to 13%): Sciatic nerve injury can occur with posterior dislocation and is typically a neurapraxia. Treatment is usually observation, unless laceration or incarceration in the joint is suspected (rare).

Chondrolysis (6%): Injury occurs at the time of hip dislocation. Management is symptomatic treatment with nonsteroidal anti-inflammatory drugs and weight-relieving devices as needed. Distraction arthroplasty may be necessary at some point.