• FEMORAL NECK FRACTURES

   

   

   

   

  EPIDEMIOLOGY

• More than 250,000 hip fractures occur in the United States each year (50% involve the femoral neck). This number is projected to double by the year 2050.

• Eighty percent occur in women. This incidence doubles every 5 to 6 years in women age >30 years.

• There is a bimodal incidence. The incidence in younger patients is very low and is associated mainly with high-energy trauma. The majority occur in the elderly (average age of 72 years) as a result of low-energy falls.

• The incidence of femoral neck fractures in the United States is 63.3 and 27.7 per 100,000 population per year for women and men, respectively.

• Risk factors include female sex, white race, increasing age, poor health, tobacco and alcohol use, previous fracture, fall history, and low estrogen level.

  ANATOMY

• The upper femoral epiphysis closes by age 16 years.

• Neck-shaft angle: 130 ± 7 degrees

• Femoral anteversion: 10 ± 7 degrees

• There is minimal periosteum about the femoral neck; thus, any callus that forms must do so by endosteal proliferation.

• Calcar femorale: This is a vertically oriented plate from the posteromedial portion of the femoral shaft radiating superiorly toward the greater trochanter.

• The capsule is attached anteriorly to the intertrochanteric line and posteriorly 1 to 1.5 cm proximal to the intertrochanteric line.

• Three ligaments attach in this region:

  1. Iliofemoral: Y-ligament of Bigelow (anterior)

  2. Pubofemoral: anterior

  3. Ischiofemoral: posterior

• Vascular supply (see Fig. 27.3)

• Forces acting across the hip joint

  • Straight leg raise: 1.5 × body weight

  • One-legged stance: 2.5 × body weight

  • Two-legged stance: 0.5 × body weight

• Internal anatomy: The direction of the trabeculae parallels the direction of compressive forces. The bony trabeculae are laid down along the lines of internal stress. A set of vertically oriented trabeculae results from the weight-bearing forces across the femoral head and a set of horizontally oriented trabeculae results from the force of the abductor muscles. These two trabeculae systems cross each other at right angles.

  MECHANISM OF INJURY

• Low-energy trauma: This is most common in older patients.

  • Direct: A fall onto the greater trochanter (valgus impaction) or forced external rotation of the lower extremity impinges an osteoporotic neck onto the posterior lip of the acetabulum (resulting in posterior comminution).

  • Indirect: Muscle forces overwhelm the strength of the femoral neck.

• High-energy trauma: This accounts for femoral neck fractures in both younger and older patients, such as motor vehicle accident or fall from a significant height.

• Cyclical loading-stress fractures: These are seen in athletes, military recruits, and ballet dancers.

• Insufficiency fractures: Patients with osteoporosis and osteopenia are at particular risk.

  CLINICAL EVALUATION

• Patients with displaced femoral neck fractures are typically nonambulatory on presentation, with shortening and external rotation of the lower extremity. Patients with impacted or stress fractures may lack deformity and they may be able to bear weight. They may, however, demonstrate subtle findings, such as groin pain and pain with axial compression.

• Those involved in high-energy trauma should be subjected to standard Advanced Trauma Life Support (ATLS) protocols.

• Pain is evident on attempted range of hip motion, with pain on axial compression, and with tenderness to palpation of the groin.

• An accurate history is important in the low-energy fracture that usually occurs in older individuals. Obtaining a history of loss of consciousness, prior syncopal episodes, medical history, chest pain, prior hip pain (pathologic fracture), and preinjury ambulatory status is essential and critical in determining optimal treatment and disposition.

• All patients should undergo a thorough secondary survey to evaluate for associated injuries.

  RADIOGRAPHIC EVALUATION

• An anteroposterior (AP) view of the pelvis and an AP and a cross-table lateral view of the involved proximal femur are indicated (Fig. 29.1). A frog lateral is contraindicated.

   

   

   

• A physician-assisted internal rotation view of the injured hip is always helpful to further clarify the fracture pattern and determine treatment plans.

• A computed tomography (CT) scan is of value in the trauma patient. Abdominal–pelvic CT cuts can be scanned for nondisplaced femoral neck fractures.

• Magnetic resonance imaging (MRI) is currently the imaging study of choice in delineating nondisplaced or occult fractures that are not apparent on plain radiographs (Fig. 29.2). Bone scans or CT scanning is reserved for those who have contraindications to MRI.

   

   

   

  CLASSIFICATION

  Anatomic Location

• Subcapital (most common)

• Transcervical

• Basicervical

  Pauwel

  This is based on the angle of fracture from the horizontal (Fig. 29.3).

  Type I: <30 degrees Type II: 31 to 70 degrees Type III: >70 degrees

  Increasing shear forces with increasing angle leads to more fracture instability.

   

   

   

  Garden

  This is based on the degree of valgus displacement (Fig. 29.4).

  Type I: Incomplete/valgus impacted

  Type II: Complete and nondisplaced on AP and lateral views

  Type III: Complete with partial displacement; trabecular pattern of the femoral head does not line up with that of the acetabulum

  Type IV: Completely displaced; trabecular pattern of the head assumes a parallel orientation with that of the acetabulum

   

   

   

  Orthopaedic Trauma Association Classification of Femoral Neck Fractures See Fracture and Dislocation Classification Compendium at http://www.ota.org/compendium/compendium.html.

  Because of poor intraobserver and interobserver reliability in using the various classifications,

  femoral neck fractures are commonly described as either:

• Nondisplaced: Impacted valgus femoral neck fractures/stress fractures: This is a much better prognostic situation.

• Displaced: This is characterized by any detectable fracture displacement.

  TREATMENT

• Goals of treatment are to minimize patient discomfort, restore hip function, and allow rapid mobilization by obtaining early anatomic reduction and stable internal fixation or prosthetic

  replacement.

• Nonoperative treatment for traumatic fractures is indicated only for patients who are at extreme medical risk for surgery; it may also be considered for demented nonambulators who have minimal hip pain.

• Early bed to chair mobilization is essential to avoid increased risks and complications of prolonged recumbency, including poor pulmonary toilet, atelectasis, venous stasis, and pressure ulceration (Fig. 29.5).

   

   

   

  Fatigue/Stress Fractures

• Tension-sided stress fractures (seen at the superior lateral neck on an internally rotated AP view): These are at significant risk for displacement; in situ screw fixation is recommended.

• Compression-sided stress fractures (seen as a haze of callus at the inferior neck): These are at minimal risk for displacement without additional trauma; protective crutch ambulation is recommended until asymptomatic. Surgery is reserved for painful, refractory fractures.

  Impacted/Nondisplaced Fractures

• Up to 40% of “impacted” or nondisplaced fractures will displace without internal fixation.

• Five percent to 15% develop osteonecrosis.

• In situ fixation with two to three cancellous screws is indicated. Exceptions are pathologic fractures, severe osteoarthritis/rheumatoid arthritis, Paget disease, and other metabolic conditions. These conditions may require prosthetic replacement.

  Displaced Fractures

• Young patient with high-energy injury and normal bone: Urgent closed or open reduction with internal fixation and capsulotomy is performed. Fixed-angle implant may be indicated in these fractures.

• Elderly patients: Treatment is controversial.

  • High functional demands and good bone quality: Almost all should receive a total hip replacement. Open or closed reduction and fixation may be considered, with a 40% reoperation rate in these patients.

  • Low demand and poor bone quality: Perform hemiarthroplasty using a cemented unipolar prosthesis.

  • Severely ill, demented, bedridden patients: Consider nonoperative treatment or prosthetic

    replacement for intolerable pain.

    Operative Treatment Principles

• Fracture reduction should be achieved in a timely fashion. Risk of osteonecrosis may increase with increasing time to fracture reduction. Furthermore, the quality of fracture reduction is believed to be a more important factor.

  • Fracture reduction maneuver: Perform hip flexion with gentle traction and external rotation to disengage the fragments, then slow extension and internal rotation to achieve reduction. Reduction must be confirmed on the AP and lateral images.

  • Guidelines for acceptable reduction: On the AP view, valgus or anatomic alignment is seen; on the lateral view, maintain anteversion while avoiding any posterior translation of the fracture surfaces.

  • Posterior comminution must be assessed.

• Internal fixation

  • Multiple screw fixation: This is the most accepted method of fixation. Threads should cross the fracture site to allow for compression.

  • Three parallel screws are the usual number for fixation. Additional screws add no additional

    stability and increase the chances of penetrating the joint. The screws should be in an inverted triangular configuration, with one screw adjacent to the inferior femoral neck and one adjacent to the posterior femoral neck.

  • Avoid screw insertion distal to the lesser trochanter secondary to a stress riser effect and risk of subsequent subtrochanteric fracture.

• Sliding-screw and side plate devices: If they are used, a second pin or screw should be inserted

  superiorly to control rotation during screw insertion. Improve resistance to shear forces in a high Pauwel angle fractures.

• Prosthetic replacement

  • Advantages over open reduction and internal fixation (ORIF)

    • It may allow faster full weight bearing.

    • It eliminates nonunion, osteonecrosis, and failure of fixation risks (>20% to 40% of cases with ORIF require secondary surgery).

  • Disadvantages

    • It is a more extensive procedure with greater blood loss.

  • Bipolar versus unipolar implants

  • There is no proven benefit of bipolar implants over unipolar implants.

  • Over time, the bipolar implant may lose motion at its inner bearing and functionally become unipolar.

  • A unipolar implant is a less expensive implant.

• Cemented versus noncemented

  • There is a lower incidence of intraoperative fracture and less thigh pain.

  • There is a risk of intraoperative hypotension and death with pressurization of cement.

• Primary total hip replacement

  • Recent enthusiasm has been reported with the use of total hip replacement for acute treatment of displaced femoral neck fractures. It is becoming the standard in active patients.

  • Studies have reported better functional results compared with hemiarthroplasty and internal

    fixation.

  • It eliminates the potential for acetabular erosion seen with hemiarthroplasty.

 

COMPLICATIONS

• Nonunion (ORIF): This is usually apparent by 12 months as groin or buttock pain, pain on hip extension, or pain with weight bearing. It may complicate up to 5% of nondisplaced fractures and up to 25% of displaced fractures. Elderly individuals presenting with nonunion may be adequately treated with arthroplasty, whereas younger patients may benefit from proximal femoral osteotomy. Cancellous bone grafting or muscle pedicle graft has fallen out of favor.

• Osteonecrosis (ORIF): This may present as groin, buttock, or proximal thigh pain; it complicates up to 10% of nondisplaced fractures and up to 30% of displaced fractures. Not all cases develop evidence of radiographic collapse. Treatment is guided by symptoms.

  • Early without x-ray changes: Individuals may be treated with protected weight bearing or possible core decompression.

  • Late with x-ray changes: Elderly individuals may be treated with arthroplasty, whereas

    younger patients may be treated with osteotomy, arthrodesis, or arthroplasty.

• Fixation failure (ORIF): This is usually related to osteoporotic bone or technical problems (malreduction, poor implant insertion). It may be treated with attempted repeat ORIF or prosthetic replacement.

• Prominent hardware may occur secondary to fracture collapse and screw “backout” following fracture compression.

• Dislocation (replacement): Total hip arthroplasty has a greater incidence than hemiarthroplasty. Overall it is 1% to 2%.