eMedicine Specialties > Sports Medicine > Hip

Femoral Neck Fracture

Author: Gerard A Malanga, MD, Founder and Director, New Jersey Sports Medicine Institute; Director of Pain Management, Overlook Hospital; Director of Sports Medicine, Sports Medicine Fellowship Director, Mountainside Hospital; Clinical Chief, Rehabilitation Medicine and Electrodiagnosis, St Michael's Medical Center; Medical Director, Consultant, Horizon Healthcare Worker's Compensation Services, Blue Cross and Blue Shield Worker's Compensation
Coauthor(s): Neil N Jasey, Jr, MD, Staff Physician, Department of Physical Medicine and Rehabilitation, Kessler Institute for Rehabilitation, University of Medicine and Dentistry of New Jersey; Jennifer Solomon, MD, Staff Physician, Department On Physical Medicine and Rehabilitation, University of Medicine and Dentistry of New Jersey
Contributor Information and Disclosures

Updated: Jan 28, 2009

Introduction

Background

The number of individuals participating in athletic activities is continually increasing, whether these individuals are highly competitive athletes or weekend sports enthusiasts. Stress fractures of the femoral neck are uncommon injuries. In general, these injuries occur in 2 distinct populations, (1) young, active individuals with unaccustomed strenuous activity or changes in activity, such as runners or endurance athletes, and (2) elderly individuals with osteoporosis. Elderly individuals may also sustain femoral neck stress fractures; however, hip fractures are much more common and are often devastating injuries.

Femoral neck fractures in young patients are usually caused by high-energy trauma. These fractures are often associated with multiple injuries and high rates of avascular necrosis and nonunion. Results of this injury depend on (1) the extent of injury (ie, amount of displacement, amount of comminution, whether circulation has been disturbed), (2) the adequacy of the reduction, and (3) the adequacy of fixation. Recognition of the disabling complications of femoral neck fractures requires meticulous attention to detail in their management.

For excellent patient education resources, visit eMedicine's Breaks, Fractures, and Dislocations Center and Sports Injury Center. Also, see eMedicine's patient education article Total Hip Replacement.

Frequency

United States

Stress fractures of the femoral neck are uncommon, but they may have serious consequences. Markey reported that femoral neck fractures comprise 5-10% of all stress fractures. Certain groups of athletes, including long-distance runners who suddenly change or add activities, appear to have a higher prevalence of femoral neck stress fractures compared with the general population.

Plancher and Donshik reported a prevalence rate of at least 10% for ipsilateral femoral shaft fractures, of which 30% are missed on the initial presentation.¹ Brukner reported that women have a higher rate of stress fractures than men, with relative risks ranging from 1.2 to 10 for similar training volumes.² Training errors are the most common risk factors, including a sudden increase in the quantity or intensity of training and the introduction of a new activity.

A number of factors predispose the elderly population to fractures, including osteoporosis, malnutrition, decreased physical activity, impaired vision, neurologic disease, poor balance, and muscle atrophy. Hip fractures are common and are often devastating in the geriatric population. More than 250,000 hip fractures occur in the United States each year; however, as reported by Koval and Zuckerman, with an aging population, the annual number of hip fractures is expected to double by the year 2050.³

Prevention of osteoporosis is key to reducing these numbers, as osteoporosis remains the single most important contributing factor to hip fractures. The prevalence of hip fractures, regardless of location, is highest among white women, followed by white men, black women, and black men.

Koval and Zuckerman noted the age-adjusted incidence of femoral neck fractures in the United States is 63.3 cases per 100,000 person-years for women and 27.7 cases per 100,000 person-years for men.³ Femoral neck fractures in elderly patients occur most commonly after minor falls or twisting injuries, and they are more common in women. In addition, Joshi et al noted stress fractures of the ipsilateral femoral neck as a rare consequence of total knee arthroplasty.⁴ Influencing factors are correction of a significant knee deformity and inactivity before the total knee arthroplasty.

International

The exact incidence of femoral neck stress fractures is not known. Volpin et al reported a rate of 4.7% in 194 Israeli military recruits.⁵ Zahger et al reported a higher rate of femoral neck stress fractures in Israeli female military recruits.⁶ Insufficiency fractures are more common in females secondary to osteoporosis.

Functional Anatomy

The femoral aspect of the hip is made up of the femoral head with its articular cartilage and the femoral neck, which connects the head to the shaft in the region of the lesser and greater trochanters. The synovial membrane incorporates the entire femoral head and the anterior neck, but only the proximal half of the posterior neck. The shape and size of the femoral neck vary widely.

Crock standardized the nomenclature of the vessels around the base of the femoral neck. The blood supply to the proximal end of the femur is divided into 3 major groups. The first is the extracapsular arterial ring located at the base of the femoral neck. The second is the ascending cervical branches of the arterial ring on the surface of the femoral neck. The third is the arteries of the ligamentum teres.

A large branch of the medial femoral circumflex artery forms the extracapsular arterial ring posteriorly and anteriorly by a branch from the lateral femoral circumflex artery. The ascending cervical branches ascend on the surface on the femoral neck anteriorly along the intertrochanteric line. Posteriorly, the cervical branches run under the synovial reflection toward the rim of the articular cartilage, which demarcates the femoral neck from its head. The lateral vessels are the most vulnerable to injury in femoral neck fractures.

A second ring of vessels is formed as the ascending cervical vessels approach the articular margin of the femoral head. From this second ring of vessels, the epiphyseal arteries are formed. The lateral epiphyseal arterial group supplies the lateral weight-bearing portion of the femoral head. The epiphyseal vessels are joined by the inferior metaphyseal vessels and vessels from the ligamentum teres.

Femoral neck fractures frequently disrupt the blood supply to the femoral head. The superior retinacular and lateral epiphyseal vessels are the most important sources of this blood supply. Widely displaced intracapsular hip fractures tear the synovium and the surrounding vessels. The progressive disruption of the blood supply can lead to serious clinical conditions and complications, including osteonecrosis and nonunion.

In 1961, Garden described the classification of femoral neck fractures. In this classification, femoral neck fractures are divided into the following 4 grades based on the degree of displacement of the fracture fragment:

• Grade I is an incomplete or valgus impacted fracture.
• Grade II is a complete fracture without bone displacement.
• Grade III is a complete fracture with partial displacement of the fracture fragments.
• Grade IV is a complete fracture with total displacement of the fracture fragments.

Frandersen et al concluded that clinically differentiating the 4 grades of fractures is difficult. Multiple observers were able to completely agree on the Garden classification in only 22% of the cases. Hence, classifying femoral neck fractures as nondisplaced (Garden grades I or II) or displaced (Garden grades III or IV) is more accurate.

Femoral neck fractures are usually intracapsular. The femoral neck has essentially no periosteal layer; hence, all healing is endosteal in origin. The synovial fluid bathing the fracture may interfere with the healing process. Angiogenic-inhibiting factors in synovial fluid can inhibit fracture repair. These factors, along with the precarious blood supply to the femoral head, make healing unpredictable and nonunions fairly frequent.

Bone physiology

Bone is a dynamic tissue, which continually reacts to stressful events. According to data from Maitra and Johnson, stress fractures result from an imbalance between bone resorption and bone deposition during the host bone response to repeated stressful events.⁷ Most cortical stress involves tension or torsion; however, bone is weaker in tension and tends to fail by fracturing along a cement line.

Maitra and Johnson went on to report that tension forces promote osteoclastic resorption, whereas compressive forces promote an osteoblastic response.⁷ With repeated stress, new bone formation cannot keep pace with bone resorption. This inability to keep up results in thinning and weakening of cortical bone, with propagation of cracks through cement lines, and, eventually, the development of microfractures. Without proper rest to correct this imbalance, these microfractures can progress to clinical fractures, the sine qua non of overuse.

A stress fracture is the result of a dynamic process over time, unlike an acute fracture, which is usually the result of a single supraphysiologic event. Markey reported that stress fractures can be described as a normal host response to abnormal stress, and this is different from insufficiency fractures, which are an abnormal host response to normal stresses.⁸

Devas, in 1965, classified stress fractures into 2 types that differ radiologically and have different clinical outcomes.⁹ The first is the tension stress fracture, which results in a transverse fracture directed perpendicular to the line of force transmitted in the femoral neck and originates at the superior surface of the femoral neck. This fracture pattern is at increased risk for displacement. These fractures carry a risk for further advancement of the fracture line superiorly and eventual displacement, leading to nonunion and avascular necrosis. Hence, early diagnosis and treatment are essential.

The second type is a compression type of femoral neck stress fracture, which has evidence of internal callus formation on radiographic images. The fracture is usually located at the inferior margin of the femoral neck without cortical discontinuity. This fracture pattern is thought to be mechanically stable. The compression fracture occurs mostly in younger patients, and continued stress does not usually cause displacement. The earliest radiographic evidence of a compression stress fracture is usually a haze of internal callus in the inferior cortex of the femoral neck. Eventually, a small fracture line appears in this area, and it gradually scleroses.

Fullerton and Snowdy described a femoral neck stress fracture classification with the following 3 categories¹⁰ : (1) tension, (2) compression, and (3) displaced. Tension fractures occur on the superolateral aspect of femoral neck and are at high risk for displacement. Compression fractures are similar to those described by Devas, which occur on the inferomedial aspect of the femoral neck and have a low risk for displacement.

Sport-Specific Biomechanics

Several theories have been developed to explain the mechanisms of femoral neck stress fractures and the biomechanics of the hip. Nordin and Frankel described the biomechanics of the hip. The load on the femoral neck can exceed 3-5 times the body weight when an individual is walking or running. Gravity acts on the center of the body mass, which results in torque on the medial aspect of the hip joint. This torque is counterbalanced by the contraction of the gluteus medius and minor. The total load on the femoral head is the sum of the forces producing these 2 torque forces. Then, these forces on the femoral head are transmitted through the femoral neck to the shaft, which create a significant amount of stress on the femoral neck as a result of compression and bending.

Minimal tension or compressive strains have been confirmed to occur in the superior aspect of the femoral neck during a normal single-leg stance. When tension increases, the inferior aspect of the femoral neck takes over the burden of damping the forces of compression. When a patient bends forward, stress is induced on the superior aspect of the femoral head; however, counter traction of the abductor muscles also occurs. Hence, if the gluteus medius muscle is fatigued, the strain is placed entirely on the superior aspect of the femoral neck. This strain can predispose patients to femoral neck stress fractures. If the abductor muscles fatigue and are unable to provide normal tension, the tensile stress in the femoral neck increases.

Muscle fatigue has been implicated as a contributing factor in the development of stress fractures. Muscle imbalance leads to changes in the application of stress across the femoral neck that may exceed the bone's capability to respond appropriately to stress. Muscle fatigue secondary to repetitive activity can decrease its shock-absorbing capacity so that higher peak stresses occur in the femoral neck. This can lead to gait abnormalities, which, in turn, can alter the body's center of gravity and change the patterns of stress placed on the femoral neck.

In the 1960s, Frankel proposed that femoral neck fractures occur in the presence of a high ratio of axial load to bending load. Altered muscle balance may also increase the risk of a hip fracture. Another theory is that a fall onto the hip with a direct blow to the greater trochanter may generate an axial force along the neck, creating an impaction fracture. The combination of axial and rotational forces has also been proposed as a mechanism.

The miserable malalignment syndrome combines femoral neck anteversion, genu valgum, increased Q-angle, tibia vera, and compensatory foot pronation that may not allow individuals to compensate for overuse. Leg-length discrepancy may also predispose individuals to injuries by creating an unequal distribution of stress and tension across the hip joint.

Clinical

History

Establishing a diagnosis in an athlete experiencing groin or hip pain with ambulation begins with a detailed history and physical examination. The basic history should include a temporal account of the patient's symptoms and a complete description of complaints. The clinician should ask the patient whether the symptoms are associated with participation in a specific sport or activity. A comprehensive training history should be obtained, and recent changes in activity level, equipment, intensity levels, and technique should be noted.

• A careful menstrual history should be obtained from all female patients. Amenorrhea is often associated with decreased serum estrogen levels. Lack of protective estrogen leads to decreases in bone mass. The female athlete triad of amenorrhea, osteoporosis, and disordered eating affects many active women. Signs and symptoms of the female triad include the following:
  • Fatigue
  • Anemia
  • Depression
  • Cold intolerance
  • Lanugo
  • Eroded tooth enamel
  • Use of laxatives
• Poor eating habits can lead to disturbances of the endocrine, cardiovascular, and gastrointestinal systems and to irreversible bone loss. The clinician should be alert to stress fractures and understand the possible signs of the female athlete triad, particularly noting unusual fractures that occur from minimal trauma.
• Most athletes describe an insidious onset of pain over 2-3 weeks, which corresponds with a recent change in training or equipment. Typically, runners have recently increased their mileage or intensity, changed their terrain, or switched running shoes. The physician should inquire about the individual's training log and mileage.
• Features common to all stress fractures include the following:
  • Participation in repetitive cyclic activity
  • Insidious onset of pain
  • Recent change in activity or equipment
  • Atraumatic history
  • Pain with weight bearing
  • Relief of pain with rest
  • Menstrual irregularities
  • Predisposing osteopenia
• Patients usually report a history of gradual- or acute-onset anterior hip, groin, or knee pain that worsens with exercise. A typical feature of a stress fracture is a history of exercise-related localized pain that increases with activity and either abates with rest or persists with less forceful activity. Pain progressively worsens with continued training. The pain is reproducible with repeated activity, and it is relieved with rest.
• The examiner should inquire whether these symptoms have occurred in the past, and, if so, whether the patient tried using ice or heat or any medications (eg, acetaminophen, aspirin, nonsteroidal anti-inflammatory drugs [NSAIDs]). Questions should be asked about previous participation in a physical therapy program, and the physician should attempt to understand the treatment plan used.

Physical

A comprehensive physical examination of the athlete with groin or hip pain should include an in-depth evaluation of the neurologic and musculoskeletal systems. Combining the findings from the history and physical examination should increase the overall predictive value of the evaluation process. The degree and type of fracture usually dictate the severity of clinical deformity.

• Inspection: The examination begins with observation of the patient during the history portion of the evaluation. Note any grimacing or abnormal gait patterns. Patients with displaced femoral neck fractures are usually unable to stand or ambulate. Observe the iliac crest for any difference in height, which may indicate a functional leg-length discrepancy. Alignment and length of the extremity is usually normal; however, the classic presentation of patients with displaced fractures is a shortened and externally rotated extremity. Assessing for any muscle atrophy or asymmetry is also important.
• Palpation: Determine any tender points in the anterior groin and hip regions. The most common physical feature of stress fractures in general is local bony tenderness; however, the neck of the femur is relatively deep and bony pain or tenderness may be absent. Palpate the trochanter for any tenderness that might indicate trochanteric bursitis.
• Range of motion: Determine the range of motion for hip flexion, extension, abduction, adduction, and internal and external rotation and for knee flexion and extension. Findings include pain and restriction at the end of passive range of motion at the hip. Perform a passive straight-leg raise, Thomas, and rectus femoris stretch test. Examine the iliotibial band by performing the Ober test.In addition to range of motion of the hip, assess the spine and other lower extremity joints, because pain referral patterns may be confusing. Examine the low back both actively and passively, looking at forward flexion, side bending, and extension. Perform a straight-leg raise test and tests for the Lasegue and Bragard signs. A patient with anterior thigh and knee pain may actually have pathology at the hip joint. Reproduction of the patient's pain with hip internal rotation, external rotation, or other provocative maneuvers may further distinguish hip pathology from spine involvement.
• Muscle strength: Manual muscle testing is important to determine whether weakness is present and whether the distribution of weakness corresponds to any nerve injuries. Additionally, evaluate the dynamic stabilizers of the pelvis, including hip flexors, extensors, and abductors. A Trendelenburg gait pattern is indicative of hip abduction weakness. Test hip flexion (L2, L3), extension (L5, S1, S2), abduction (L4, L5, S1), and adduction (L3, L4).
• Sensory examination: Upon sensory examination, a dermatomal decrease or loss of sensation can indicate or exclude any specific nerve damage. Muscle stretch reflexes are helpful in the evaluation of patients presenting with hip pain. Abnormal reflexes can indicate nerve root abnormality. The asymmetry of reflexes is most significant; therefore, a patient's reflexes must be compared with the contralateral side.
• Hop test: Approximately 70% of patients with stress fractures of the femur demonstrate a positive hop test result. The hop test involves the patient hopping on the affected leg to reproduce symptoms. Other maneuvers that can place a stress on the femur also may reproduce pain.

Causes

Training errors are the most common risk factors for femoral neck fractures, including a sudden increase in the quantity or intensity of training and the introduction of a new activity. Other factors include low bone density, abnormal body composition, dietary deficiencies, biomechanical abnormalities, and menstrual irregularities.

• Predisposing factors, such as anatomic variations, relative osteopenia, poor physical conditioning, systemic medical conditions that demineralize bone, or temporary inactivity, can make bone more susceptible to stress fractures. As reported by Monteleone, studies have indicated that women have an increased incidence of stress fractures, which may be the result of anatomic variations.¹¹ Women tend to direct axial force during weight bearing along different axes of long bones compared with men. Women also have 25% less muscle mass per body weight than men. This may concentrate, rather than dissipate, the stabilizing forces through the bony anatomy.
• Markey reported that Hersman et al documented women have a higher incidence of stress fractures.⁸ This higher incidence is partly a result of mechanical differences and anatomic variations between men and women. Differences in women include various stride lengths, number of strides per distance, a wider pelvis, coxa vara, and genu valgum.
• Exercise-induced endocrine abnormalities are well known to result in amenorrhea or nutritional deficiencies, which can lead to bone demineralization and can place these patients at risk for various overuse injuries. Stress fractures, especially in trabecular bone, have shown a decrease in bone mineral content. This decrease can be reproduced by a decrease in circulating estrogen, which is observed in amenorrheic female athletes. Lack of protective estrogen leads to a decrease in bone mass. The female athlete triad of amenorrhea, osteoporosis, and disordered eating affects many active women. Irreversible bone loss places the patient at a higher risk for fractures.
• Most people are not competitive athletes and may not be at a level of optimum fitness. Individuals often force themselves to participate at a level for which they are not physically fit. Flexibility, muscle strength, and neuromuscular coordination contribute to injuries when individuals are not properly trained.

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