Hip Fracture in Emergency Medicine 

Fractures of the hip are relatively common in adults and often lead to devastating consequences. Disability frequently results from persistent pain and limited physical mobility. Hip fractures are associated with substantial morbidity and mortality; approximately 15-20% of patients die within 1 year of fracture. Interestingly, morbidity and mortality in those older than 90 years sustaining a hip fracture were not found to be statistically higher than others in the same age group without such an injury.

Most hip fractures occur in elderly individuals as a result of minimal trauma, such as a fall from standing height. In young, healthy patients, these fractures usually result from high-velocity injuries, such as motor vehicle collisions or falls from significant heights. Despite comparable fracture locations, the differences in low- and high-velocity injuries in older versus younger patients outweigh their similarities. High-velocity injuries are more difficult to treat and are associated with more complications than minor trauma injuries.

Egan et al identified several risk factors associated with the risk of a hip fracture patient sustaining a second fall.^[1] Increasing age, cognitive impairment, decreasing bone mass, decreasing depth perception, decreased mobility, dizziness, and a poor/fair self-perceived state of health were all linked to increasing likelihood of sustaining a second fall and thus a possible second hip fracture.

Several recent studies have identified additional risk factors for hip fracture. Sennerby et al identified generalized cardiovascular disease as a significant risk factor for hip fracture,^[2] while Carbone et al determined that heart failure is a specific risk for hip fracture^[3] . Specific characteristics in men were evaluated to determine the relationship to hip fracture; smoking, tall stature, stroke, and dementia were found to increase the risk of hip fracture, while non – work-related physical activity and high BMI were found to be protective.^[4] Kettunen at al studied previously elite male athletes and found that these individuals sustained hip fractures at significantly older ages than their less active counterparts.^[5]

Two medication classes have also been implicated in hip fractures. Nursing home patients on antipsychotic medications and HIV-positive patients on protease inhibitor therapy were more likely to sustain fractures than those on other agents.^{[6, 7]}

For more information, see Medscape's Fracture Resource Center.

This section discusses skeletal anatomy, vascular supply, and fracture classification.

The hip joint is a large multiaxial ball-and-socket synovial joint, enclosed by a thick articular capsule. The hip joint is designed for stability and a wide range of movement. Next to the shoulder, it is the most moveable of all joints. During standing, the entire weight of the upper body is transmitted to the heads and necks of the femurs. The round head of the femur articulates with the cuplike acetabulum. The depth of the acetabulum is increased by the reinforcing fibrocartilaginous labrum, which "grasps" the femoral head, covering more than half of it. Articular cartilage covers the entire head of the femur, except for the pit (fovea) for the ligament of the femoral head.

The strong, loose fibrous capsule permits free movement of the hip joint, attaching proximally to the acetabulum and transverse acetabular ligament. The fibrous capsule attaches distally to the neck of the femur only anteriorly at the intertrochanteric line and root of the greater trochanter. Posteriorly, the fibrous capsule crosses to the neck proximal to the intertrochanteric crest without attaching to it. The fibrous capsule thickens to form 3 ligaments of the hip joint: the Y-shaped iliofemoral ligament (of Bigelow), the pubofemoral ligament, and the ischiofemoral ligament.

The hip joint is further supported by the femur and the muscles that cross the joint; this bone and these muscles are the largest and most powerful in the human body. The anatomy of the femur is shown below.

The length, angle, and narrow circumference of the femoral neck permit substantial range of motion at the hip but also subject the femoral neck to incredible shearing forces. A fracture results when these forces exceed the strength of the bone. The intertrochanteric line is an oblique line that connects the greater and lesser trochanters, dividing the femoral neck from the shaft. Hip fractures involve fracture of any aspect of the proximal femur, from the head to the first 4-5 cm of the subtrochanteric area.

The vascular supply to the proximal femur is tenuous and provided largely by two sources.

Branches of the medial and lateral circumflex femoral arteries, usually branches of the deep femoral artery, ascend on the posterior aspect of the femoral neck in the retinacula (reflections of the capsule along the neck of the femur toward the head). The branches of the medial and lateral circumflex arteries perforate the bone just distal to the head of the femur where they anastomose with branches from the foveal artery and with medullary branches located within the shaft of the femur.

The ligament of the head of the femur usually contains the artery of the ligament of the head of the femur (foveal artery), a branch of the obturator artery. The foveal artery enters the head of the femur only when the center of the ossification has extended to the pit (fovea) for the ligament of the head, around age 11-13 years. This anastomosis persists even in advanced age but is never established in 20% of the population.

Femoral neck fractures often disrupt the blood supply to the head of the femur. The medial circumflex artery supplies most of the blood to the head and neck of the femur and is often torn in femoral neck fractures. In some cases, the blood supplied by the foveal artery may be the only blood received by the proximal fragment of the femoral head. If the blood vessels are ruptured, the fragment of bone may receive no blood and undergo avascular necrosis (AVN).

Hip fractures can be classified based on their relation to the hip capsule (intracapsular and extracapsular), geographic location (head, neck, trochanteric, intertrochanteric, and subtrochanteric), and degree of displacement. Higher-grade displacement implies worse prognosis. Fractures of the femoral head and neck are intracapsular, whereas those of the trochanteric, intertrochanteric, and subtrochanteric regions are extracapsular. The treatment as well as the prognosis for successful union and restoration of normal function varies considerably with fracture type.

Intracapsular hip fractures, like all other intracapsular fractures, frequently have complicated healing. The thick capsule that surrounds these fractures separates them from adjacent soft tissue and capillaries, leading to impaired callous formation. Thus, nonunion and AVN are added complications of these fractures.

Femoral head fractures

Isolated femoral head fractures are rare and are usually associated with hip dislocations. Superior femoral head fractures normally are associated with anterior dislocations, while inferior femoral head fractures are associated with posterior dislocations. They are usually best appreciated on postreduction radiographs for hip dislocations. Fractures of the femoral head are more common in younger patients as a result of major trauma, which is more likely to cause femoral neck fractures in older patients.

• Type 1 - Single fragment fractures (see image below)
• Type 2 - Comminuted fractures (see image below)Femoral head fractures. Top diagram is a single-fragment femoral head fracture. Bottom diagram is a comminuted femoral head fracture.

Femoral neck fractures

These are rare among younger patients but are commonly seen in older adults, most often secondary to osteoporosis or osteomalacia. These fractures usually result from minor trauma with falls accounting for 90%, or torsion. From proximal to distal, femoral neck fractures can be further delineated as subcapital, transcervical, and basicervical, all of which are intracapsular and associated with potential disruption of the vascular supply. The incidence of avascular necrosis (AVN) is up to 15% in nondisplaced fractures and increases to nearly 90% with untreated, completely displaced fractures.

• Type 1 - Stress fractures or incomplete fractures (see image below)
• Type 2 - Impacted fractures (see image below)Femoral neck fractures. Top diagram is a nondisplaced, or incomplete, femoral neck fracture. Bottom diagram is an impacted femoral neck fracture.
• Type 3 - Partially displaced fractures (see image below)Partially displaced femoral neck fracture.
• Type 4 - Completely displaced or comminuted fractures (see image below)
• {Imagenum5:825471}

Trochanteric fractures

Greater trochanteric fractures usually result from avulsion injuries at the insertion of the gluteus medius. Lesser trochanteric fractures may be caused by avulsion injuries of the iliopsoas secondary to forceful contraction. These are most common in children and young athletes (eg, dancers, gymnasts).

• Type 1 - Nondisplaced fractures (see image below)
• Type 2 - Displaced fractures; >1 mm displacement for fractures of the greater trochanter and >2 mm displacement for fractures of the lesser trochanter (see image below) Trochanteric fractures. Top diagram is a nondisplaced trochanteric fracture. Bottom diagram is a displaced trochanteric fracture.

Intertrochanteric fractures

These extracapsular fractures occur in a line between the greater and lesser trochanters, generally in elderly patients and women secondary to osteoporosis.

• Type 1 - Single fracture line without displacement; stable (see image below)
• Type 2 - Multiple fracture lines (comminution) with displacement; unstable (see image below)Intertrochanteric fractures. Top diagram is a single fracture line intertrochanteric fracture. Bottom diagram is a displaced, or multiple fracture line, intertrochanteric fracture.

Subtrochanteric fractures

These fractures have a bimodal age distribution and are seen most often in those aged 20-40 years in association with high-energy trauma and in patients older than 60 years secondary to falls on osteoporotic bones.

• Stable: Bony contact of medial and posterior femoral cortices
• Unstable

Frequency

United States

In the United States, hip fracture occurs in approximately 80 per 100,000 persons or approximately 250,000 persons each year. The rate of hip fracture increases with age, doubling each decade after age 50 years. Nearly half of all hip fractures occur in adults older than 80 years. Hip fracture at a young age is rare and is usually the result of a high-velocity injury or, rarely, secondary to bone pathology.

International

The US frequency of hip fracture, when age and sex are adjusted, ranks the highest in the world. Western Europe and New Zealand also have reported high rates, with the lowest rates occurring in the South African Bantu people and in East Asian countries, where the incidence of osteoporosis is low.

Mortality/Morbidity

• Reported overall mortality rate of hip fractures is 15-20%, yet in older persons this can increase to 36% over the year following hip fracture. Rate of mortality is greatest in the first few months following injury but remains high for up to 1 year. It then returns to the same rate for age- and sex-matched people without hip fracture. Surgical delay independently affects mortality. Patients for whom surgery is delayed for 2 days or more, have a 17% higher mortality rate at 1 month. A subsequent study showed increased mortality but decreased readmission rate in those repaired more than 4 days from the time of injury.^[8] Also, general anesthesia was associated with higher morbidity than was spinal/epidural anesthesia.^[8]
• Morbidity associated with hip fracture is staggering, especially in older persons. Morbidity from immobilization includes development of deep vein thrombosis, pulmonary embolism, pneumonia, and muscular deconditioning. Morbidity from surgical procedures includes complications of anesthesia, postoperative infection, loss of fixation, malunion or nonunion, as well as the complications associated with immobilization as outlined above.
• Surgical delay of greater than 48 hours has also been shown to increase morbidity and mortality.^[9]
• Hip fracture resulting from major trauma often is associated with other bone and soft-tissue injuries, intra-abdominal and intrapelvic injuries, major blood loss, head and neck injuries, and other extremity injuries. Morbidity associated with an inability to return to a prefracture level of mobility results in a loss of independence, reduction in quality of life, and depression, particularly in older persons.

Race

The incidence of hip fracture is 2-3 times greater in whites than in nonwhites, primarily because of the increased rate of osteoporosis in whites. This difference is not unique to females; African American and Asian men have been found to have significantly higher bone densities than their Caucasian and Latino counterparts.^[10]

Sex

Rate of hip fracture is 2-3 times greater in women than in men. At least 75% of all hip fractures occur in women. The lifetime risk of hip fracture in white women and men is 15% and 5%, respectively. Femoral neck fractures are more common in women than in men by about 4:1, while intertrochanteric fractures are more common in women than in men by about 5:1.