Traumatic Injuries to the Hip: Femoral Neck Fracture and Posterior Dislocation



Traumatic Injuries to the Hip: Femoral Neck Fracture and Posterior Dislocation





BACKGROUND

Traumatic injuries involving the hip in children and adolescents, including femoral neck fracture, posterior hip dislocation, and acetabular wall fractures are relatively rare and usually associated with a high-energy mechanism. As these injuries are associated with severe complications such as osteonecrosis of the femoral head, understanding the principles that guide surgical treatment is crucial to achieve the best outcomes.


Femoral Neck Fractures

Pediatric femoral neck fracture is a rare injury typically associated with high-energy trauma, which accounts for less than 1% of all pediatric fractures.1,2,3 The diagnosis is based on a history of trauma and examination, revealing a shortened and externally rotated lower extremity complemented by imaging. Radiographs should include an anteroposterior view of the pelvis and a cross-table lateral view of the femur. Frog-leg lateral imaging should be avoided because of further displacement and pain. Rarely, advanced imaging, including a computed tomography (CT) or magnetic resonance imaging (MRI), is used for a suspected occult fracture.

Femoral neck fractures in children and adolescents are classified on the basis of the anatomic location of the fracture according to the four-part system described by Delbet and popularized by Colonna4 (Figure 20.1). The classification is important because of its correlation with the development of osteonecrosis of the capital femoral epiphysis. Type I is a fracture through the capital femoral epiphysis growth plate, which can be associated with dislocation of the hip joint. These fractures have a high rate of complications. Virtually, 100% of the type I fractures associated with a dislocation of the hip (type IB) complicate with osteonecrosis. Type II fractures are truly transcervical fractures, whereas type III fractures or basocervical fractures occur through the base of the femoral neck. It is essential to distinguish between the transcervical (type II) versus the basocervical (type III) because the risk of osteonecrosis of the femoral head is higher following a type II fracture. Type IV fractures are intertrochanteric fractures, which have a much lower risk of osteonecrosis. However, type IV fractures may complicate with malunion if not well reduced and appropriately fixed. Although widely used because of the association with the risk of osteonecrosis, the Delbet-Colonna classification system is incomplete because it does not take into consideration the degree of displacement of the fracture and the inclination of the fracture through the neck. Fracture displacement and the angle of fracture from the horizontal are important features for classifying femoral neck fracture in adults.5,6 The severity of displacement and angulation of the fracture should be taken into consideration for pediatric fractures because of their association with osteonecrosis of the femoral head and malunion, respectively.7






FIGURE 20.1. Delbet-Colonna classification of femoral neck fractures in children.

Treatment of femoral neck fractures in children and adolescents is surgical. Although nondisplaced and incomplete fractures may be amenable to nonoperative treatment with cast immobilization in the very young child, our preference is for percutaneous fixation to avoid malunion. In toddlers, fixation may be achieved with smooth Kirschner wires, followed by spica cast immobilization.
In older children, fixation of nondisplaced femoral neck fractures should be performed with cannulated screws or a pediatric hip sliding screw. In general, a fracture of the femoral neck should be fixed with mechanical stability of the fixation in mind. For this reason, it is often necessary to include fixation of the fracture that includes the capital femoral epiphysis growth plate to enhance stability of the fixation. Rarely, slipped capital femoral epiphysis has been described following fixation of a femoral neck fracture preserving the growth plate.8 This catastrophic complication is to be avoided by including fixation of the capital femoral epiphysis into the construct of a femoral neck fracture fixation. After surgical treatment, children younger than 6 years of age may benefit from a spica cast immobilization. In older children, an abduction foam immobilizer should be sufficient. Patients are recommended to remain non-weight-bearing for a minimum of 6 to 8 weeks and then transition to weight-bearing with a walker or crutches. Femoral neck fractures should be followed for a minimum of 2 years because of the risk of late osteonecrosis.

Minimally displaced and angulated fractures may be treated by closed reduction using an operative traction table and percutaneous or internal fixation. Decompression of the intracapsular hematoma has been suggested as an adjunct to closed reduction. However, the role of decompression to decrease the risk of osteonecrosis remains controversial. Our preference for displaced femoral neck fractures is to perform an open reduction to achieve anatomic reduction of the fragments. Two types of surgical approaches can be used for the open treatment of femoral neck fractures. The anterior approach through the Smith-Petersen modified incision and dissection between the sartorius and tensor fascia lata allows adequate exposure of the anterior aspect of the femoral neck for reduction. Fixation of the fracture is then performed through a small lateral approach for the placement of cannulated screws or a sliding hip screw. We favor the use of an anterolateral approach described by Watson-Jones (Figure 20.2). Our technique for the treatment of femoral neck fractures using the Watson-Jones approach is similar to that described for the treatment of acute unstable slipped capital femoral epiphysis in Chapter 7. The rationale for using the Watson-Jones approach is that it allows full exposure of the superior, anterior, and medial aspects of the femoral neck and fixation through the same incision. Briefly, the patient is positioned in a sloppy lateral position with a bump under the ipsilateral scapula and the gluteal muscles. A curvilinear incision is made about 1 or 2 cm distal and lateral to the anterior superior iliac spine, aiming toward the greater trochanter and curved down to the lateral aspect of the thigh. The fascia lata is incised in line with the skin incision. The interval between the gluteus medius and the tensor fascia lata is dissected. It is easier to start the dissection distally and move proximally. Attention is required to avoid injury to nerve branches from the superior gluteal nerve which innervates the tensor fascia lata. Small vessels in this area can be ligated or cauterized as needed. We start the dissection by identifying the interval between the gluteus medius and the vastus lateralis distal in the trochanteric region and move proximally, retracting the gluteus medius proximally and laterally. As the dissection moves proximally, the gluteus minimus is identified and elevated from the posterosuperior aspect of the hip capsule. The iliocapsularis muscle is also elevated but in the anterior and medial direction. This allows full exposure of the hip capsule. A good reference for adequate exposure is visualization of the indirect head of the rectus femoris tendon. The joint capsule is then open longitudinally in line with the femoral neck up to the level of the acetabular labrum. The capsule is open medially and laterally just distal to the labrum for about a centimeter and a half for a final T-shaped capsulotomy. The fracture hematoma is evacuated, and the fracture fragments are cleaned using a curette. Reduction is gently achieved by manual traction to the lower extremity along with slight internal rotation by an assistant while the surgeon can guide the rotation using a ball spike instrument or a small bone hook. Rarely, reduction is achieved by insertion of a Schanz pin into the fragments to facilitate the manipulation. Once the fracture is anatomically reduced, provisional K-wires are introduced to hold the fixation in place while definitive fixation is planned. Definitive fixation can be achieved by sliding a hip screw with the addition of an antirotational screw or with cannulated partially threaded screws for compression with one fully threaded screw to avoid shortening of the neck. The choice of the implant is based on the fracture classification and obliquity. As a general rule, types I and II fractures are fixed with cannulated screws, whereas types III and IV fractures are fixed with a pediatric sliding hip screw with an antirotational screw. (Figure 20.3) We preferred the sliding hip screw rather than a fixed angle locking plate for fixation of femoral neck fractures, but in rare instances, where patients may have an associated metabolic condition with pathologic bone fragility, a locking device with fixed angle may be appropriate.

The most challenging aspect of treating a femoral neck fracture is the high proportion of complications, previously reported to be as high as 94%.9 Reported complications include osteonecrosis of the femoral head, malunion, nonunion, premature physeal growth arrest, infection, leg length discrepancy, and implant failure. The most worrisome complication is osteonecrosis of the femoral head. Numerous factors have been implicated in the development of osteonecrosis, including age,10,11 fracture type,10,12,13 displacement,9,12,14 surgical timing,10,12,15,16 surgical fixation,6,17 treatment type (open versus closed),16,18 and quality of reduction.11 Nevertheless, the best treatment strategy to reduce the occurrence of osteonecrosis remains controversial. Some reports suggest that open reduction and internal fixation (ORIF) reduces the risk,7,18,19
while others, report an increased incidence of ON associated with open treatment16,20 However, in adult patients, the quality of reduction has been shown to be the most important factor for favorable fracture healing. Notably, the best outcomes have been reported when anatomic reduction and stable internal fixation are implemented.6,21

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May 10, 2021 | Posted by in ORTHOPEDIC | Comments Off on Traumatic Injuries to the Hip: Femoral Neck Fracture and Posterior Dislocation
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