Femoral Neck Fracture Case File
Eugene C. Toy, MD, Andrew J. Rosenbaum, MD, Timothy T. Roberts, MD, Joshua S. Dines, MD
CASE 4
A 76-year-old Caucasian female is brought to the emergency department (ED) with complaints of left groin pain after stumbling and falling in the hallway of her home. Previously she ambulated without assistance, but she states that now she cannot bear weight on her left leg. Although she did not lose consciousness, she recalls feeling “a little light-headed” before she fell. She has no other complaints or pains. She takes several medications for a history of cardiac arrhythmias, including warfarin. On physical exam, the patient is laying comfortably in the stretcher with her left leg held in slight external rotation. She reports pain with gentle passive rotation of her hip. There is a slight ecchymosis over her left greater trochanter. She readily dorsi- and plantarflexes her left ankle and flexes and extends her toes; her sensation is intact throughout her leg. Gentle palpation of all other joints is negative for tenderness or notable deformity. Her temperature is 98ºF, blood pressure 134/88 mmHg, and heart rate is 155 beats/min. An electrocardiogram shows a rapid, erratic ventricular rate without discernible p waves. Initial laboratory tests show a hemoglobin and hematocrit of 11.5 g/dL and 35.0%, respectively, and an international normalized ratio (INR) of 3.4. A radiograph is obtained and can be seen in Figure 4–1.
► What is the most likely diagnosis?
► What is the best treatment for this patient?
► What are other additional immediate concerns for this patient?
Figure 4–1. AP radiograph of the left hip.
ANSWER TO CASE 4:
Femoral Neck Fracture
Summary: A 76-year-old woman complains of left hip pain after suffering a presyncopal fall onto her left hip. She suffers a nondisplaced femoral neck fracture.
- Most likely diagnosis: Anteroposterior (AP) radiograph of the left hip showing a fracture that extends obliquely across the femoral neck. The femoral head is not significantly displaced from the femur, but impacted into the neck and rotated away from the midline. This results in a valgus deformity.
- Treatment options: Although treatment options always include nonoperative management—historically treated with prolonged bed rest and traction— fractures of the femoral neck are best treated surgically. Basic methods include fixation with screws and hip arthroplasty.
- Additional concerns: The patient’s elevated INR puts her at risk for significant perioperative bleeding, especially if she requires hip prosthesis placement. Furthermore, her history of unsteady gate and dizziness requires a thorough workup for presyncope. Her cardiac comorbidities, age, and additional aspects of her history place her at risk for multiple perioperative complications. Anesthesia, internal medicine, and/or cardiology are often consulted for assistance with perioperative risk management.
ANALYSIS
Objectives
- Distinguish different types of femoral neck fractures and their classifications.
- Determine the appropriate treatment options for various types of femoral neck fractures with regard to patient age, comorbidities, and prior activity level.
- Understand the mechanics and anatomy of the hip with special regard to its blood supply.
- Be familiar with the complications associated with femoral neck fractures.
Considerations
This mechanism of injury—a low-energy, direct fall onto the great trochanter—is perhaps the most common cause of hip fracture in elderly patients. The affected extremity may be shortened and externally rotated with displaced fractures; however, in neck fractures that are nondisplaced, physical signs may be subtle and limited to pain with weight bearing or with movement, especially rotation, of the hip. Femoral neck fractures are not usually associated with neurovascular injury unless accompanied by other injuries; these should be of greater suspicion in younger patients who have sustained hip fractures from high-energy mechanisms.
This patient exhibits many risk factors for an insufficiency fracture of the hip, including her postmenopausal age, female sex, white race, and history of tobacco use. Despite these risk factors, however, the patient maintained a fairly active lifestyle, ambulating and participating in many daily activities; such activity levels help guide expectations and treatments.
Additionally, this patient has atrial fibrillation that is not rate-controlled on presentation. Her anticoagulation status, secondary to warfarin use, precludes all but the most drastic of surgical interventions. The patient’s elevated INR must be reversed before invasive procedures are performed. An unstable cardiac history of arrhythmias or valve replacements necessitates careful evaluation and optimization before surgery, balancing the importance of anticoagulation with perioperative
bleeding. Fortunately, this patient’s nondisplaced neck fracture need not be fixed in an emergent manner; however, some types of nondisplaced hip fractures, as discussed below, demand a more prompt, emergency fixation to preserve blood supply to vulnerable bone. During her hospitalization, this patient should have her presyncopal symptoms and coagulation addressed by her medical team.
Preoperative risks must be addressed quickly and minimized when possible, as many studies show improved patient outcomes with early (< 4 days in some studies) versus delayed surgical interventions. Advantages include reduced hospital stays, risks of pulmonary complications, venous thromboembolism, and pressure ulceration.
APPROACH TO:
Femoral Neck Fracture
DEFINITIONS
AVASCULAR (OSTEO)NECROSIS (AVN): Bone death secondary to inadequate blood supply. May be idiopathic; secondary to biological, chemical, or physical insults; or, in femoral neck fractures, the result of traumatic loss of vascular supply.
CALCAR FEMORALE: Dense, vertically oriented bone originating in the posteromedial portion of the femoral shaft under the lesser trochanter. It radiates laterally toward the posterior aspect of the greater trochanter, reinforcing the femoral neck posteroinferiorly.
INTRACAPSULAR FEMORAL NECK: This term refers to the area of the femoral neck that is located within the joint capsule. Anteriorly, the capsule attaches to the intertrochanteric line. Posteriorly, it attaches 1 to 1.5 cm proximal to the intertrochanteric line at the base of the neck.
EXTRACAPSULAR FEMORAL NECK: This term refers to the more distal area of the femoral neck, which is located outside the joint capsule. This predominantly metaphyseal region has excellent blood supply and therefore has a comparatively low risk of nonunion/AVN.
CROSS-TABLE LATERAL X-RAYS: A radiographic view that allows perpendicular assessment of the femoral neck without need for manipulation of the affected extremity. It is obtained by flexing the contralateral hip out of the x-ray plane and obtaining x-rays perpendicular to the femoral neck.
HEMIARTHROPLASTY: A surgical procedure that replaces the femoral portion of the hip joint; the femoral head and neck are removed and replaced with a prosthesis containing a femoral head component that swivels in the remnant acetabulum.
CLINICAL APPROACH
Anatomy
The hip joint is a ball-and-socket joint consisting of the femoral head articulating with the acetabulum. The femoral neck is characterized by a 120 to 135-degree angle formed between the femoral neck and femoral shaft in the coronal plane and 15 to 25 degrees of anteversion, or forward rotation, in the sagittal plane. The predominantly cortical bone in the femoral neck has a highly organized arrangement, with trabeculae oriented in the direction of major stress forces across the hip joint.
In adults, blood supply to the femoral neck and head is primarily through the medial circumflex femoral artery, a branch of the deep femoral (or profunda femoris) artery. Additional supplies are from the lateral femoral circumflex artery and the foveal artery, which travels through the ligamentum teres directly into the femoral head. Both circumflex femoral vessels form an extracapsular anastomotic ring at the base of the femoral neck and then penetrate the capsule to become intracapsular, thereby ascending to supply the head. Unlike the shaft of the femur, the intracapsular portion of its neck is devoid of periosteum; all healing must therefore occur through endosteal means, which necessitates an intact blood supply. It is critical to restore anatomic alignment in displaced fractures and to stabilize nondisplaced fractures to prevent future compromise to blood supply.
Mechanism of Injury
High-energy trauma, regardless of age, sex, or comorbidity, may cause femoral neck fractures. In the elderly or debilitated, however, femoral neck fracture most commonly occurs secondary to low-energy falls, either directly through forces on the greater trochanter, which transmits a force onto the femoral neck, or from forceful external rotation of the limb. Additional mechanisms include the repetitive loading forces experienced by athletes that gradually weaken portions of bone over time and manifest in stress fractures. Similar stress fractures may occur in patients with osteoporosis.
Evaluation and Diagnosis
In the setting of high-energy mechanisms, advanced traumatic life support protocols should be initiated to evaluate for any life-threatening injuries. With low-energy mechanisms such as a fall from standing, the patient should be evaluated for additional acute injuries such as head, cervical spine, or limb trauma. In patients without a history of acute trauma, other causes must be evaluated, including repetitive load cycling, particularly in physically active males and females with osteoporosis secondary to medical conditions including anorexia nervosa and renal or endocrine disorders.
The affected extremity should be evaluated for shortening, rotation, and neurovascular integrity. In some cases, physical signs may be very subtle. Gentle range of motion of the hip may elicit pain. Radiographic evaluation should use both an AP pelvis and a cross-table lateral image of the involved side. When history and physical exam are clinically suggestive of fracture despite normal x-ray findings, magnetic resonance imaging or bone scan may reveal occult fractures.
Classification
Femoral neck fractures are described using a variety of methods, including classification by anatomic location, by displacement of the fracture fragments, or by the vertical angulation of the fracture lines.
Anatomic Descriptors: Simple anatomic descriptors include the following:
Subcapital fracture: An intracapsular fracture located at the junction between the femoral head and neck.
Transcervical fracture: An intracapsular fracture extending across the mid-portion of the femoral neck.
Basicervical fracture: An extracapsular fracture located at the base of the femoral neck. Although this fracture is anatomically located within the femoral neck, it is often treated as an intertrochanteric fracture because of the biomechanical forces across this fracture.
Garden Classification: Describes fractures based primarily on the degree of displacement noted in the AP radiograph. The risk of avascular necrosis and nonunion is predicted to be higher with increasing grade. The orientation of trabecular bone of the head with regard to that of the acetabulum is helpful in distinguishing these fracture types. Table 4–1 outlines the definitions and radiographic features of the Garden classification of femoral neck fractures.
Pauwel Classification: Fractures are categorized according to the angle that they form with the horizontal plane: grade I, 0 to 30 degrees; II, 30 to 70 degrees; and III, > 70 degrees. At low angles, the forces of weightbearing are perpendicular to the fracture line and actually assist healing by compressing the pieces together to promote bone growth. As the angle increases, however, these forces become shear forces, exacerbating displacement of the pieces or failure of fixation. Pauwel type III fractures are thus associated with significant instability and high risks of nonunion and avascular necrosis. The stability of a fracture pattern no doubt influences the method of its treatment.
TREATMENT
Regardless of fracture type, the goals are almost universal: Minimize patient discomfort, restore hip function, and allow mobilization as early and safely as possible. Although most nondisplaced extremity fractures are treated with nonoperative immobilization, the difficulties of effective, comfortable, or practical immobilization of the hip are almost insurmountable. Furthermore, in the rare cases of nonoperative hip fracture treatment, subsequent displacement rates are as high as 40%. Nonoperative management is therefore reserved for only those absolutely medically unfit for surgery or severely demented and pain-free nonambulators.
Nondisplaced Fractures
Internal Fixation: Surgical fixation of nondisplaced fractures is most commonly achieved with cancellous lag screws percutaneously placed through the femoral neck. Typically, 3 screws are inserted in an inverted-triangular configuration, first using thin K-wires placed under x-ray fluoroscopy, which are then replaced by cannulated, or hollow, screws inserted over the wires. Care should be taken to avoid starting the screws distal to the level of the lesser trochanter, as the extreme tension forces on this side of the bone would be prone to stress riser forces and propagation of fracture.
General indications for percutaneous pinning include impacted and nondisplaced femoral neck fractures (ie, Gardner I or II fractures or those with low Pauwel angles [type I]). In situ screw fixation is contraindicated, however, in patients with pathologic fractures or severe osteoarthritis or rheumatoid arthritis; such patients should be alternatively managed with prosthetic replacement.
Displaced Fractures
Fracture Reduction and Fixation: There are a variety of surgical treatment options for displaced fractures, which vary significantly with regard to patient age, previous activity level, and comorbidities.
In young, otherwise healthy individuals, displaced transcervical or subcapital fractures pose a unique challenge. Here, prompt reduction of the femur is essential to restoring blood flow to support adequate healing. Femoral neck fractures in young individuals are generally considered an orthopaedic emergency, as risks of osteonecrosis may increase with increasing time until reduction. Reductions, too, must be anatomic to maximally preserve the blood supply.
Reduction in displaced neck fractures is typically achieved by externally rotating and flexing the hip under gentle traction to disengage fragments, then internally rotating to approximate the ends. Reduction must be evaluated by AP and crosstable lateral views. If prompt reduction is achieved, percutaneous pins, using the methods previously described, may be used to fix the unstable reduction. If reduction cannot be achieved using these closed methods, open reduction and internal fixation should be performed. Such constructs may be performed with sliding-screw or fixed-angle devices. If there is significant comminution, extensive damage, and stripped vasculature and soft tissue support, or significant comminution of the femoral neck, especially in the compression load-bearing calcar femorale region, the risks of AVN are high.
Arthroplasty: In elderly patients, patients with limited ambulatory status (those who previously ambulated with walkers or crutches or were wheelchair bound), and patients with underlying significant arthritis or osteoporosis, arthroplasty is generally the treatment of choice. By replacing the femoral head and neck, arthroplasty eliminates the risks of nonunion, avascular necrosis, and hardware failure that may be a consequence of internal fixation. Arthroplasty may be total (a replacement of both the acetabular cup and the femoral neck and head) or hemi (meaning the replacement of the femoral components placed into a native acetabulum). Hemiarthroplasty prostheses may be unipolar, involving a static implant that swivels in the acetabular cup, or, more commonly, bipolar, which provide an extraarticulating junction between the femoral head shell and inner ball. Although total arthroplasty is the most extensive and invasive option, it may afford the highest level of function to elderly albeit healthy individuals who previously maintained active lifestyles.
Complications
Femoral neck fractures impose a high mortality risk in the elderly population, reaching up to 30% at 1 year. Surgical treatment with internal fixation carries its own risks, most commonly:
Nonunion: Displaced femoral neck fractures generally take longer to heal, often 6 months or longer. The total rate of nonunion is reported to be 6%.
Hardware failure: This complication is most commonly reported concomitantly with nonunion and may require a conversion arthroplasty to fix.
Avascular necrosis: This tends to be a delayed complication, more commonly a complication of fractures displaced at presentation. AVN may not be evident until at least 2 years postoperatively. Conversion total arthroplasty is preferred over hemiarthroplasty, as the acetabulum often also exhibits degenerative changes due to collapse of the femoral head.
COMPREHENSION QUESTIONS
4.1 A 42-year-old man complains of right hip pain after being ejected from an allterrain vehicle. He denies neurologic changes or other symptoms. His right leg does not appear to be shortened or externally rotated. Right hip radiographs demonstrate a complete, nondisplaced transcervical fracture. What is the most appropriate treatment for this patient?
A. Nonoperative observation with pain control, limited weightbearing, and close follow-upB. Percutaneous pinningC. Bipolar hemiarthroplastyD. Total hip arthroplasty
4.2 A 66-year-old avid cross-country skier sustains a displaced femoral neck fracture after a fall down an icy embankment. What is the best treatment option for this patient?
A. Bipolar hemiarthroplastyB. Open reduction internal fixationC. Unipolar hemiarthroplastyD. Nonoperative treatment with close follow-upE. Total hip arthroplasty
4.3 A 72-year-old man sustains a completely displaced, subcapital femoral neck fracture after tripping over a step on a neighbors porch. Awake and lucid in the ED, he is most likely to assume which of the following positions for his fractured extremity?
A. Flexion and external rotationB. Extension and external rotationC. Flexion and neutral rotation and flexionD. Extension and neutral rotationE. Flexion and internal rotation
ANSWERS
4.1 B. The patient’s young age and fracture severity are the major determinants of management. Of the surgical options listed, percutaneous pinning is the least invasive option in the setting of nondisplaced fractures. Regardless of displacement, closed reduction with internal fixation is the recommended choice of treatment in this age group. Arthroplasty is more commonly performed in the elderly population.
4.2 E. Given the presence of a displaced femoral neck fracture in an elderly patient, arthroplasty (options A, C, and E) is indicated. Given this patient’s previously active lifestyle, total hip arthroplasty, option E, would best restore this patient to his previous level of function.
4.3 A. Patients with intracapsular pathology of the hip tend to hold their extremities in a position of external rotation and flexion. This patient has suffered subcapital fracture of the femoral neck, which is an intracapsular injury, thus resulting in hematoma formation and increased pressure within the hip socket. In a position of external rotation and flexion, the volume of the hip socket is greatest, and thus patients fi nd relative comfort in this position. Additionally, children with septic arthritis of the hip will assume this position, as pain from pressurized inflammatory responses is similarly minimized.
CLINICAL PEARLS
► In the absence of absolute medical contraindications to surgery, the great majority of hip fractures are treated operatively. ► Despite significant improvements in the ability to surgically treat hip fractures and manage medical comorbidities, the mortality of hip fractures in patients ≥ 80 years of age is upward of 30% within 1 year from fracture. |
REFERENCES
Buchholz RW, Court-Brown CM, Heckman JD, Tornetta P, eds. Femoral neck fractures. In: Rockwood and Green’s Fractures in Adults. 7th ed. 2 vol. Philadelphia, PA: Lippincott Williams & Wilkins; 2010:1561-1596.
Egol KE, Koval KJ, Zukerman JD, eds. Femoral neck fractures. In: Handbook of Fractures. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010:378-387.
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