eMedicine Specialties > Radiology > Musculoskeletal

Femoral Neck, Fractures

Author: Hieu T Truong, MD, Staff Physician, Department of Radiological Sciences, University of California at Los Angeles Medical Center
Coauthor(s): Amilcare Gentili, MD, Clinical Professor of Radiology, University of California at San Diego; Consulting Staff, Department of Radiology, Thornton Hospital
Contributor Information and Disclosures

Updated: Nov 2, 2007

Introduction

Background

Femoral neck fractures have proven to be serious injuries that are associated with high mortality and significant morbidity in the geriatric population. The incidence has increased since the 1960s and is expected to increase in the foreseeable future, as life expectancies increase.¹ Despite advances in surgical hardware and techniques, these injuries still pose a significant clinical challenge.^1,2,3 (See also the eMedicine articles Femoral Neck Stress and Insufficiency Fractures [in the Orthopedic Surgery section], Femoral Neck Fracture [in the Sports Medicine section], and Fractures, Hip [in the Emergency Medicine section], as well as the articles Hip Protector Does Not Prevent Hip Fractures in Elderly Nursing Home Residents and Journal Watch (General) - Don't Delay Surgery After Hip Fracture, on Medscape.)

For excellent patient education resources, visit eMedicine's Bone, Joint, and Muscle Center, Fractures and Broken Bones Center, and Arthritis Center. Also, see eMedicine's patient education articles Breaks, Fractures, and Dislocations and Osteoporosis and Bone Health.

Pathophysiology

Femoral neck fractures occur most commonly after falls. Factors that increase the risk of injuries are related to conditions that increase the probability of falls and those that decrease the intrinsic ability of the person to withstand the trauma. Physical deconditioning, malnutrition, impaired vision and balance, neurologic problems, and slower reflexes all increase the risk of falls. Osteoporosis is the most important risk factor that contributes to hip fractures. This condition decreases bone strength and, therefore, the bone's ability to resist trauma. (See also the eMedicine articles Osteoporosis [in the Rheumatology section] and Osteoporosis [in the Orthopedic Surgery section], as well as the Osteoporosis Resource Center, on Medscape.)

Femoral neck fractures can also be related to chronic stress instead of a single traumatic event. The resulting stress fractures can be divided into fatigue fractures and insufficiency fractures. Fatigue fractures are a result of an increased or abnormal stress placed on normal bone,⁴ whereas insufficiency fractures are due to normal stresses placed on diseased bone, such as an osteoporotic bone. (See also the eMedicine articles Femoral Neck Stress and Insufficiency Fractures and Stress Fractures [in the Orthopedic Surgery section] and Stress Fracture [in the Radiology section].) 

Frequency

United States

The incidence of hip fractures exceeds 250,000 per year, with an estimated cost of nearly $10 billion.¹

Mortality/Morbidity

The primary complications arising from femoral neck fractures are nonunion and avascular necrosis (AVN). The rates of these events vary widely in the literature. In one review of reports from 1975-1990 involving patients older than 65 years, the rate of osteonecrosis was 33%, and the rate of nonunion in those treated with internal fixation was 16%. Other authors estimate the nonunion rate to be about 20%, and that of AVN is approximately 25%. Moreover, the mortality rate attributed to femoral neck fractures is on the order of 10%. (See also the eMedicine articles Femoral Head Avascular Necrosis [in the Sports Medicine section] and Avascular Necrosis, Femoral Head [in the Radiology section].)

Race

The rate of observed hip fractures is highest in white women, followed by white men, black women, and black men. These differences are thought to be due to differences in bone density among these groups.

Sex

Femoral neck fractures are more common in white women than in other patients because of the increased prevalence of osteoporosis in this group.

Age

Traumatic femoral neck fractures most commonly occur in the elderly, even after apparently trivial falls or twisting injuries. In young persons, traumatic femoral neck fractures are usually the result of high-energy trauma and are usually associated with multiple concomitant injuries.⁴ Stress fractures of the femoral neck can occur in both age groups, with insufficiency fractures found in the elderly and fatigue fractures found in young athletes.

Anatomy

The joint capsule of the hip extends from the acetabulum to the intertrochanteric line anteriorly and to the junction of the middle and distal thirds of the femoral neck posteriorly. Femoral neck fractures are therefore intracapsular injuries. This distinction is important because intracapsular fractures are more prone to posttraumatic complications. The main complication is osteonecrosis because the blood supply to the femoral head originates from the circumflex femoral arteries, which have branches that course recurrently along the joint capsule past the femoral neck to supply the femoral head.⁵ Fractures of the femoral neck and/or damage to the capsule can disrupt these supplying arteries.⁵ The ligamentum teres artery, which supplies the femoral head directly from a more proximal route by coursing through the acetabular fossa, provides insufficient vascularization to the femoral head by itself to prevent AVN. In fact, it may be completely atretic after puberty. (See alsothe eMedicine article Osteonecrosis, Hip.)

Some studies suggest that the retinacular arteries on the surface of the femoral neck and the ligamentum teres artery are sensitive to changes in intracapsular pressure.⁶ Increased pressure from an intracapsular bleed compromises this circulation. Because of the inelastic character of the joint capsule, small increases in volume (eg, from a bleed) can result in large increases in joint pressure. The exact pressure at which circulation is compromised is not known, but it has been estimated by some authorities to be around 40 mm Hg.

The hip joint itself is a ball-and-socket joint, which allows for the wide range of motion required for ambulation. The acetabulum, which covers 40% of the femoral head, is formed by the ilium, ischium, and pubic bones. The greater trochanter of the hip serves as the insertion site for the gluteus medius and minimus, obturator internus and externus, superior and inferior gemelli, and piriformis tendons. The lesser trochanter is the site of attachment of the iliopsoas tendon. The femoral neck extends from the base of the femoral head to the intertrochanteric line.

Preferred Examination

Radiography should always be the initial imaging modality.⁷ Then, depending on the clinical concern, additional studies can be obtained. Magnetic resonance imaging (MRI)^8,9 or nuclear medicine scintigraphy^10,11,12,13 may provide additional information if the presence of a fracture is equivocal on radiographs. Computed tomography (CT) scanning may be useful if more osseous details (eg, degree of comminution and possible intra-articular bone fragments) are required.

Limitations of Techniques

Some fractures are not visible on plain films. Spiral fractures can be difficult to detect on a single view (see Radiograph, Degree of Confidence, below). Some stress fractures may not be seen at all. In general, nondisplaced or minimally displaced fractures are difficult to perceive using plain radiographs.

Differential Diagnoses

Other Problems to Be Considered

Pathologic fractures
Femoral Head Avascular Necrosis (in the Sports Medicine section), Avascular Necrosis, Femoral Head (in the Radiology section)
Osteonecrosis, Hip
Deep Venous Thrombosis and Thrombophlebitis

• Search for CME/CE on This Topic »

• Acetabulum Fractures (Orthopedic Surgery)
• Intertrochanteric Hip Fractures (Orthopedic Surgery)
• Femoral Neck Stress and Insufficiency Fractures (Orthopedic Surgery)
• Femoral Neck Fracture (Sports Medicine)

• Bone Fractures More Likely in HIV-Positive Postmenopausal Minority Women
• Alendronate Improves BMD in Men on Anti-Androgen Therapy
• Zoledronic Acid Prevents Bone Loss in Postmenopausal Women With Osteopenia

• The Effect of Time-to-Surgery on Outcome in Elderly Patients With Proximal Femoral Fractures
• Preventing Nonvertebral Osteoporotic Fractures With Extended-Interval Bisphosphonates: Regimen Selection and Clinical Application
• Atypical Fractures in Long-term Bisphosphonate Users

• Fracture Resource Center