6 Femoral Neck Fractures
Reduction and Fixation
Defining the Injury
Fractures of the proximal femur are generally categorized as follows: (1) femoral head fractures, (2) femoral neck fractures, and (3) trochanteric fractures (including the subtrochanteric region). In their 1961 study of the proximal femur, Garden et al defined femoral neck fractures as subcapital fractures of the femur with fracture lines present between the femoral head and the trochanteric region.1 These investigators also highlighted the importance of differentiating between fractures lending themselves to stable reduction and fractures less amenable to stabilization.1,2 Based on the position and displacement of the fragments, Garden et al demonstrated that unstable fractures are more likely than stable fractures to damage the blood vessels of the femoral head and potentially cause avascular femoral head necrosis.
Several other authors defined intracapsular medial femoral neck fractures, in which the fracture line is close to the femoral head, as well as extracapsular lateral (basocervical) femoral neck fractures, which occur close to the intertrochanteric line.
There are several comprehensive classification systems for femoral neck fractures and related prognostic factors such as femoral head necrosis, fracture nonunion, and fracture stability. The best-known classification systems are those of Garden (1964) and Pauwels (1935).3,4
Many investigators have devised classification schemes for femoral neck fractures that indicate prognostic differences according to fracture type. The first classification of femoral neck fractures was published in 1823 by Cooper, who divided these injuries into intracapsular and extracapsular fractures.5 Waldenström in 1924 and Cotton in 1927 classified these injuries as either abduction fractures and adduction fractures, according to their displacement features.6,7 In 1955, Watson-Jones developed a system based on the age of the patient. He concluded that certain fracture types were typical in certain age groups.8 Enduring and meaningful classification systems were finally developed by Pauwels in 1935, Linton in 1941, and Garden in 1961.3,4,9,10
Classification System of Garden
In 1964, Garden et al created a classification system for femoral neck fractures that consisted of four fracture types (Garden I to Garden IV), depending on the position and displacement of the femoral head in the anteroposterior (AP) projection (Fig. 6-1). In this system, type I includes fractures with an incomplete fracture line through the femoral neck and valgus position of the proximal fragment, type II comprises fractures with a complete fracture line through the femoral neck and no displacement between the proximal and distal fragments, type III includes fractures with a complete fracture line through the femoral neck and varus displacement of the proximal fragment that is less than 50% of the femoral neck diameter, and type IV comprises fractures with varus displacement of more than 50% of the femoral neck diameter or complete dissociation of the proximal and distal fragments.
This classification scheme provides information about the likelihood of developing avascular femoral head necrosis. Patients with type I fractures have a probability of femoral head necrosis of less than 5%. In type II fractures, the likelihood of this complication is less than 10%. However, the probability of avascular necrosis is more than 50% in type III fractures and more than 80% in type IV fractures. The Garden classification is still the most important and commonly used scheme to classify femoral neck fractures and to determine individual strategies for treatment of these injuries.
Classification System of Pauwels
In 1935, Pauwels published a classification system of femoral neck fractures that included three types (Pauwels I to Pauwels III). The fractures were divided according to the angle between the fracture line and the horizontal line in the AP radiographic projection (Fig. 6-2). In this system, type I fractures have an angle smaller than 30 degrees between the fracture line and the horizontal line, type II fractures have an angle between 30 and 70 degrees, and type III fractures have an angle larger than 70 degrees.
The prognostic value of this scheme includes the likelihood of fracture nonunion based on the vertical sheerness of the fracture. Type I fractures (0 to 30 degrees) are associated with a likelihood of fracture nonunion of less than 5%, type II fractures (30 to 70 degrees) have a less than 10% probability of nonunion, and type III (>70 degrees) fractures have a likelihood of nonunion of more than 25%.
The AO (Arbeitsgemeinschaft für Osteosynthesefragen, Switzerland, 1958) developed a simplified classification for femoral neck fractures including three subtypes (31 B1 to 31 B3). This system is arranged in order of increasing severity of these injuries according to complexity of the fracture, difficulty in treatment, and prognosis. These fractures are finally categorized by fracture site (subcapital, transcervical), as well as by impaction and displacement of the femoral head. Subtype B1 describes subcapital fractures with impaction and slight displacement, subtype II fractures are transcervical, and the subtype III category includes subcapital and nonimpacted fractures with strong displacement (Fig. 6-3).
Classification System of Linton
In 1941, Linton presented his classification scheme, which included three different types of femoral neck fractures based on the angulations between the median femoral neck trabeculae and the femur’s medial cortical trabeculae. This angle is normally 160 degrees in the AP projection (Fig. 6-4). Linton also considered the displacement of the central axis of the femoral head to the central axis of the femoral neck in the axial view, which is usually in a straight line of 180 degrees. Fractures were finally divided into the following categories: (1) fractures in adduction, with varus displacement and an angle between the median femoral neck trabeculae and the femur’s medial cortical trabeculae much smaller than 160 degrees; (2) fractures in abduction, with valgus displacement and parallel median femoral neck and femoral medial cortical trabeculae; and (3) intermediate fractures, corresponding to displacement halfway between adduction and abduction.
For adequate diagnosis of femoral neck fractures, a thorough clinical examination is performed, and complementary radiographic studies are obtained. Common clinical characteristics of patients with femoral neck fractures include shortening and external rotation of the affected limb, pain during active and passive mobilization, and an inability to walk or to raise the outstretched leg from the surface.
Although these features are seen in most patients with femoral neck fractures, not all patients have this clinical presentation. For example, in patients with incomplete abduction fractures with valgus impaction or stress fractures without any displacement, these characteristics may be notably diminished or even absent. A detailed patient interview and history, as well as a complete review of the patient’s medical records, may aid in the diagnosis of suspected pathologic fractures or fractures secondary to irradiation.
The initial diagnosis of patients with suspected femoral neck fractures includes three standard radiographs: (1) a pelvic radiograph, (2) an AP view of the affected hip, and (3) an axial view of the affected hip (Lauenstein projection). The standard radiographs usually allow sufficient assessment of the fracture type and estimation of fracture stability, as well as prognostic outcome, to determine individual strategies for treatment of these injuries. In patients with clinical evidence of femoral neck fractures that are not definitely verifiable on standard radiographs, changes in the trabecular lines may be observed and are indications for further imaging studies. In pathologic fractures, metastases usually become visible as rounded osteolytic or sclerotic lesions when more than 30% to 50% of bone resorption has already occurred.
Further radiographic examinations are indicated in patients with clinical evidence of femoral neck fractures that are not obvious or verifiable on standard radiographs. In most of these cases, a computed tomography (CT) scan of the pelvis (with three-dimensional helical reconstruction) establishes the definitive diagnosis. Because delays in the diagnosis of these injuries occur with an incidence up to 15% and additionally increase morbidity in these patients, a CT scan of the pelvis should be considered obligatory in patients with a clear onset of symptoms but uncertain radiographic findings.
Further examinations, such as magnetic resonance imaging and bone scintigraphy, of the pelvis or the affected hip are usually reserved for particular questions and problems and are not considered in the primary evaluation of these injuries. Both techniques are commonly requested as screening methods for early detection of malignant metastases or other bone-weakening diseases.
The best treatment option for femoral neck fractures is still controversial. It is aimed at restoring hip function and enabling the patient to achieve early and rapid mobilization, to reduce the risks of medical complications, and to improve functional outcome.
The approach to management of femoral neck fractures must take into account the following considerations: fracture type (especially whether the fracture is displaced or nondisplaced), chronologic and physiologic age of the patient, life expectancy, and overall health condition, which includes activity level, bone quality, and medical comorbidities. Operative management has become the treatment of choice for most femoral neck fractures because it permits early patient mobilization and minimizes many of the complications of prolonged recumbency. However, no clear consensus about the method of treatment has emerged to date, especially for elderly patients. The decision to perform internal fixation, unipolar or bipolar hemiarthroplasty, or total hip arthroplasty (THA) must be based on the patient’s mental status, age, living arrangements, level of independence and activity, and bone and joint quality.
Nonsurgical management of intracapsular hip fractures is limited. Occasionally, nonsurgical treatment may be indicated for debilitated, demented, or nonambulatory bedridden patients or for patients whose medical condition carries a high risk of mortality from surgery and anesthesia.
In some cases, nonsurgical treatment can also be an option in patients with undisplaced impacted valgus fractures classified as Garden type I or Pauwels type I. Impaction must be evident on both AP and true lateral radiographic views, and axial alignment of the femoral neck must also be intact. Nonoperative management begins with bed rest and exercises in bed until the pain subsides. Gradual mobilization begins with transfer to a chair, walking without weight bearing with crutches or other walking aids, and later walking with partial weight bearing. After 6 to 8 weeks, full weight bearing can be started. Radiographs should be taken regularly, especially at the beginning of mobilization, after partial weight bearing, and before full weight bearing. In literature, outcome after nonoperatively treated impacted fractures is still controversial. Raaymakers et al reported satisfactory results after conservative treatment, but they also reported a high rate of secondary fracture displacement, especially in elderly patients.11,12 These investigators found secondary instability in 41% of patients more than 70 years of age, but only in 7% of healthy patients less than 70 years of age. Shuqiang et al also found secondary displacement in 41% of their patients, and the highest displacement rate was at age 60 to 80 years.13 Bentley, Hilleboe et al, and Jensen and Hogh showed a fracture displacement or disimpaction rate of 10% to 27% with conservative treatment.14–16 Raaymakers et al also found a high correlation between comorbidity and secondary instability.11 Verheyen et al stated that the stability of the fracture depended on several intrinsic and extrinsic factors such as age, comorbidity, Pauwels angle, and retroversion.17
Because of these results, more and more investigators have recommended primary operative stabilization of impacted fractures. When there are no comorbidities representing an increased risk for surgery, most surgeons feel confident about implementing a strategy of prophylactic internal fixation in patients with impacted or nondisplaced femoral neck fractures.