Femur and Hip Injuries

Skeletal Anatomy

The femur is the longest and strongest bone in the human body and is routinely subjected to substantial forces during powerful muscle contraction and weight transmission. It consists of the femoral head, neck, and shaft. The femoral head is firmly seated in the acetabulum , reinforced by the labral cartilage. The well-developed capsule, overlying ligaments, and proximal musculature of the lower extremity add strength to the joint ( Fig. 47.1 ). Structurally, the femoral neck serves as an oblique strut between the pelvis (the horizontal beam) and the shaft of the femur (the vertical beam) ( Fig. 47.2 ). The length, angle, and narrow circumference of the femoral neck permit substantial range of motion at the hip, but these same characteristics subject the neck to significant shearing forces.

The type of bone in the femur changes depending on location, which affects fracture patterns. The bone in the femoral head, neck, and intertrochanteric region is predominantly cancellous, which is less resistant to torsional forces. Distal to the intertrochanteric region, including the subtrochanteric region and femoral shaft, the bone is cortical, which requires increased force to fracture. At the distal metaphysis, the femur widens as the cortical bone thins, lessening its resistance to stress.

Musculature

The musculature of the hip and thigh is the largest and most powerful in the human body . Grouped according to the primary action at the hip, the muscles in this region of the body are located within three compartments, each containing associated nerves and vessels ( Table 47.1 ). Knowledge of the major muscle actions offers insight into common injury patterns and deformities ( Fig. 47.3 ).

Arterial Supply

The arterial supply of the femoral head, neck, and shaft arises from different sources. The major arterial supply to the femoral head and neck comes from the medial and lateral circumflex arteries, which are branches of the femoral artery ( Fig. 47.4 ). These branches form an extracapsular arterial ring around the femoral neck. Another blood supply source to the femoral head typically arises from the obturator artery and courses through the ligamentum teres.

As the external iliac artery passes beneath the inguinal ligament, it becomes the common femoral artery. At this point, the artery is located midway between the anterior superior iliac spine (ASIS) and the symphysis pubis. Approximately 3 to 4 cm distal to the inguinal ligament, the deep femoral artery branches off. The deep femoral artery is predominantly responsible for the vascular supply of the femur. It runs posterolaterally to the superficial femoral artery, supplies the hamstrings, and terminates in the distal third of the thigh as small branches supply the belly of the adductor magnus. The superficial femoral artery continues to pass along the anteromedial aspect of the thigh and terminates at the junction of the middle and lower thirds of the thigh. Here, the superficial femoral artery passes through the adductor hiatus and becomes the popliteal artery.

Venous System

In the proximal two-thirds of the thigh, the common and superficial femoral veins lie adjacent to the common and superficial femoral arteries. At the inguinal ligament, the common femoral vein is posterior and medial to the common femoral artery and moves to the lateral position as it passes distally. The deep femoral vein and the greater saphenous vein are the two main tributaries to the common and superficial femoral veins. The deep femoral vein and artery run in parallel as the vein joins the superficial femoral vein just distal to the inguinal ligament. The greater saphenous vein arises in the dorsum of the foot and ascends anterior to the medial malleolus. This vein is relatively superficial as it traverses up the medial aspect of the leg to join the common femoral vein distal to the inguinal ligament.

Nerves

The femoral and sciatic nerves are the major nerves within the thigh. The femoral nerve is the largest branch of the lumbar plexus; it passes under the inguinal ligament lateral to the femoral artery and divides into anterior and posterior branches soon after entering the thigh. The sensory divisions of the anterior branch, the intermediate and medial cutaneous nerves, supply sensation to the anteromedial aspect of the thigh. The motor division of the anterior branch innervates the pectineus and sartorius muscles. The posterior femoral branch gives off the saphenous nerve, which supplies sensation to the skin along the medial aspect of the lower part of the leg. The posterior branch also supplies motor function to the muscles of the quadriceps femoris group.

The sciatic nerve is the largest peripheral nerve in the body . It arises from the sacral plexus. The sciatic nerve exits the pelvis through the greater sciatic foramen and travels through the posterior thigh; it extends from the inferior border of the pyriformis muscle to the distal third of the thigh. The sciatic nerve gives off articular branches that supply the hip joint. In the thigh, muscular branches innervate the adductor magnus and hamstring muscles. Just proximal to the popliteal fossa, the sciatic nerve divides to form the tibial and common peroneal nerves.

Fractures and Trauma of the Femur and Hip

The vast majority of hip fractures occur in elderly patients with preexisting bone disease who sustain low-energy trauma, usually a ground-level mechanical fall. In young, healthy individuals, high energy trauma, such as a motor vehicle collision (MVC) or a fall from a significant height, is responsible for most fractures.

Twenty percent of patients with hip fracture die during the first year after the injury, mostly from sequelae of the fracture rather than the fracture itself. One-third of patients require nursing home placement, and less than one-third regain their pre-fracture level of physical function. The economic impact of these fractures is significant.

Osteoporosis of the Femur

Osteoporosis is the leading cause of hip fracture . The pathophysiology of osteoporosis is not completely understood, but strong associations with hormonal changes related to aging, genetic predisposition, vitamin D deficiency, lack of physical activity, and smoking have been recognized. Severe osteoporosis and hip fractures are most common in elderly white women; however, a decrease in bone density after age 30 is seen across all demographic groups. The trabeculae of the femoral head and neck strengthen the bone and therefore support the large mechanical forces produced across the hip joint. As osteoporosis progresses, the trabeculae disappear and increase the risk of fracture. Osteoporosis currently affects more than 10 million people in the United States and is projected to affect approximately 14 million adults older than 50 years by the year 2020. The number of hip fractures attributable to osteoporosis is expected to be more than 6 million by the year 2050, although the incidence in women has been decreasing in recent years. An important factor to consider is that while age standardized rates may be falling, the effects of an aging population significantly overcomes this decline, leading to an overall increase in incidence. ^,

Osteoarthritis of the hip

A large percentage of the American population experiences chronic pain from degenerative osteoarthritis of the hip. Disability often results from persistent pain, limited physical mobility, and sacrcopenia. The progression of osteoarthritis can be demonstrated with serial radiographs of the affected hip ( Fig. 47.5 ); however, radiographic findings do not necessarily correlate with symptoms.

Avascular Necrosis

When a patient has an increasingly painful hip, buttock, thigh, or knee and no history of recent trauma, AVN of the femoral head and sciatica should be considered. AVN has been referred to as aseptic necrosis, ischemic necrosis, and osteonecrosis. It is the result of ischemic bone death of the femoral head after compromise of its blood supply ( Fig. 47.6 ). AVN is bilateral in 40% to 80% of patients. It is common in relatively young patients, the mean age at diagnosis being 38 years old. Although a specific causative disorder is not identified in 20% of cases, known atraumatic causes include chronic corticosteroid therapy, chronic alcoholism, hemoglobinopathy (e.g., sickle cell anemia), dysbarism, and chronic pancreatitis. AVN is an emerging complication associated with human immunodeficiency virus (HIV) infection. It is unclear whether the pathologic agent is the virus itself or an adverse side-effect of the treatment.

Traumatic AVN, a subacute manifestation after hip dislocation or femoral neck fracture, is a direct result of disruption of the blood supply to the femoral head. It is more common in males and African Americans. The incidence of AVN as a subacute complication is clearly related to both the initial degree of trauma and the amount of time the femoral head remains dislocated. Multiple studies have demonstrated a relationship between the length of time the hip is dislocated and the rates of AVN: it develops in about 5% of patients when reduction is performed within 6 hours and as many as 60% when reduction occurs after 12 hours. For this reason, a hip dislocation is an orthopedic emergency . The emergency clinician should perform reduction as soon as possible and definitely if orthopedic consultation will be delayed more than 6 hours.

Even with optimal treatment, owing to the tenuous blood supply to the area, femoral neck fractures can be complicated by AVN in up to 20% of cases. Immediately after fracture, bleeding may cause high intracapsular pressure and a tamponade effect on the femoral head, thereby impairing the blood supply. In contrast, intertrochanteric and subtrochanteric fractures are located in an area with a rich extracapsular arterial supply; therefore, AVN is a rare complication of these fractures.

Myositis Ossificans

Myositis ossificans (or heterotrophic ossification) is pathologic bone formation at a site where bone is not normally found; the thigh and hip muscles are often involved. Traumatic myositis ossificans results most commonly from a direct blow to muscle or from repeated minor trauma. Bleeding into the muscle after trauma produces a local hematoma with subsequent new bone formation within it. Depending on its location, the ossific mass might be palpable, painful, and might limit range of motion.

Myositis ossificans occurs in up to 20% of patients undergoing medical evaluation for thigh contusions, likely related to the severity of the injury. The incidence of myositis ossificans after hip surgery is approximately 2%, and these lesions are clinically significant in 10% to 20% of cases. Increased susceptibility to myositis ossificans has been described in persons with hemophilia and other bleeding disorders in conjunction with soft tissue injury. Radiographically, myositis ossificans appears as irregularly shaped masses of heterogeneous bone in the soft tissues around the joint or along fascial planes ( Fig. 47.7 ). It can be seen as early as 10 to 21 days after injury, but radiographic evidence typically lags behind the onset of symptoms by weeks. Its appearance might simulate primary bone neoplasm, especially when the periosteum is involved. Computed tomography (CT) can be helpful in distinguishing between neoplasm and myositis ossificans, because the lesions of myositis ossificans begin to calcify at the periphery and progress toward the center, and those of osteosarcoma begin to calcify at the center first.

Calcific Bursitis and Calcifying Peritendinitis

Calcification surrounding tendons and bursae or occurring in the joint capsule is referred to as calcific bursitis or calcifying peritendinitis. The cause of these lesions is unclear. No relationship has been documented between the radiographic findings and acute symptoms. Calcific bursitis of the hip is uncommon, but when it does occur, it most frequently affects the trochanteric bursa ( Fig. 47.8 ). Other possible affected areas include the gluteal muscles and the hip flexors and adductors. The bursal calcification is seen on radiographs as an amorphous, poorly marginated line that is clearly separate from the cortex of the femur.

Neoplastic Disease in the Hip

The most common neoplastic disease of bone is metastatic, generally from breast, kidney, lung, thyroid, or prostate tumors. Primary bone lesions also occur, the most common being osteoid osteoma ( Fig. 47.9 ). Bone lesions can be osteoblastic or osteolytic. Patients present with significant bone pain or a large mass that has become irritated or painful ( Fig. 47.10 ). Neoplasms place the patient at higher risk for pathologic fractures, especially if the lesions are large, lytic, or have eroded the cortex. Osteosarcoma and periosteal osteogenic sarcoma should be considered in the differential diagnoses of hip pain.

Physical Examination

Patients with femoral pathology can have a multitude of presentations; therefore, a thorough physical examination is important. Due to the major forces that are sustained in multisystem trauma, hypotension is a problem commonly encountered during the initial resuscitation. Hypotension, neurovascular compromise, or suspicion for multiple injuries are indications for transfer to a specialized trauma center.

After life-threatening conditions have been addressed, the injured extremity can be evaluated carefully. The position of the leg can offer a clue to radiographic findings. External rotation, abduction, and shortening suggest a displaced femoral neck fracture. External rotation with shortening suggests an intertrochanteric fracture. Visual inspection may reveal pallor, ecchymosis, asymmetry, or deformity. The presence of abrasions, lacerations, and open wounds may indicate forces that caused the injury and direct the evaluation for concomitant fractures. Nondisplaced fractures, including stress fractures, should not produce limb shortening or rotational deformities but will be painful on passive range of motion, particularly internal and external rotation. In patients with obvious deformities, testing range of motion should be deferred until after radiographs have been obtained and vascular integrity has been verified.

Systematic examination of the injured extremity may reveal focal tenderness or warmth suggesting injury or infection. Active and passive range of motion and assessment of muscle strength, though offering important information, are frequently limited by pain. A detailed neurovascular assessment is vital, as femoral nerve and arterial injuries often occur in conjunction with subtrochanteric and femoral shaft fractures or anterior hip dislocations. The sciatic nerve can be injured with a hip fracture or posterior hip dislocation. Neurologic examination includes evaluation of light touch, pinprick sensation, and proprioception. The examination should also assess for any signs of arterial injury indicating a rapidly expanding hematoma. Femoral, popliteal, dorsalis pedis, and posterior tibial pulses should all be assessed. Comparative blood pressures obtained by Doppler examination in the injured and uninjured extremities (arterial pressure index) are useful in diagnosing occult femoral arterial injuries. The ankle-brachial index (ABI) also can be determined by comparing the systolic pressures of the affected extremity and the ipsilateral arm. An index less than 0.9 necessitates further diagnostic studies. Although acute compartment syndrome of the thigh is rare, consideration should be given to this diagnosis if the patient sustained a severe mechanism of injury and has tense swelling in the thigh.

Occult Hip Fracture

If radiographs do not show an overt fracture or injury, the emergency clinician should assess the patient’s gait. Inability to ambulate or difficulty in weight bearing suggests an occult fracture. Up to 10% of all hip fractures are radiographically “occult” on plain films. Failure to detect these injuries increases the risk of subsequent displacement of the fracture, the incidence of AVN, and the risk of death. When a painful hip prevents ambulation and plain radiographs do not reveal a fracture, advanced imaging (CT or magnetic resonance imaging [MRI]) is indicated ( Fig. 47.14 ). Elderly patients with unexplained hip pain lasting more than 3 weeks may be harboring an occult fracture even if they continue to walk. T1-weighted MRI will reveal a fracture that was imperceptible at the time of injury with nearly 100% accuracy and is cost-effective compared with other strategies. MRI is superior to CT and remains the “gold standard” for diagnosing occult hip fractures and helps guide treatment decisions (see Fig. 47.12 ).

Bone scans have been useful in older patients with occult fractures, but they lack adequate sensitivity. To identify most occult fractures, this type of scan should be delayed for 72 hours after the injury, which limits its use in the ED setting.

Vascular assessment must be considered when there is any concern for any vascular injury including pallor, compartment syndrome, or rapidly expanding hematomas. This can include Doppler measurements including ABI. If the systolic pressure in the affected extremity is 90% or less (ratio less than 0.9) than that in the unaffected extremity, additional diagnostic studies should be performed. Vascular assessment studies include Doppler flow ultrasound imaging, computed tomography angiography (CTA), or angiography alone.

Systemic Analgesia

Pain control in the ED is often inadequate. For patients with femoral fractures, opioid analgesia is often indicated in combination with other pain-relief strategies. In addition to parenteral medications, other pain-relieving strategies include immobilization of the injured extremity, placement of the injured extremity in a position of comfort, and the administration of local nerve blocks .

Pharmacologic Approaches

The classic pharmacologic treatment for pain management in patients with traumatic femoral injuries is opioid analgesics. Morphine, fentanyl, and hydromorphone are all acceptable options. Fentanyl and hydromorphone are the preferred IV opioid analgesics in patients with renal dysfunction. Due to the unpredictability of the supply chain and negative associations of opioids, many pre-hospital providers now use ketamine for pain relief. Meperidine should not be used because of unpredictable side effects, including seizures. Nonsteroidal antiinflammatory drugs (NSAIDs), while safe in younger populations, can be difficult to use, especially in the elderly, due to their renal and gastrointestinal side effects.

Femoral Nerve Block

The femoral nerve block is an excellent option as an adjunct or alternative to systemic analgesics in patients at risk for hypotension. Femoral nerve blocks significantly decrease the time to the lowest pain score compared with intravenous narcotics, and patients require significantly lower doses of narcotics. With the assistance of a peripheral nerve stimulator to localize the nerve or bedside ultrasound to directly visualize the nerve, the anesthetic is injected, safely, and under sterile conditions. The procedure can also be performed by emergency clinicians without the assistance of peripheral nerve stimulators or ultrasound. If a long-acting anesthetic such as bupivacaine is used, the expected onset of analgesia is within 30 minutes and its duration (on average) is 6 to 8 hours. A Cochrane review demonstrated that regional blockade reduced pain on movement within 30 minutes after block placement, and there is moderate quality of evidence for reduced time to first mobilization, reduced cost of analgesic, and decreased risk of pneumonia.

A neurovascular examination should be performed and documented before the femoral nerve block is performed. After the nerve block, continued assessment of the femoral muscular compartments is advisable to check for the development of compartment syndrome. If an injury is considered to be at especially high risk for compartment syndrome, orthopedic surgery consultation should be obtained before the block, and measurement of compartment pressures after the block should be considered. Because the sciatic nerve innervates the compartments of the lower limb, a femoral nerve block will not mask the clinical presentation of compartment syndrome in the lower leg.

Avulsion Fractures

Management

As depicted in Fig. 47.15 , avulsion at the ASIS involves the separation of a thin piece of bone as the sartorius muscle suddenly contracts (see Fig. 47.15A ). The anterior inferior iliac spine (AIIS) is avulsed by the rectus femoris, and the hamstrings group can displace the ischial tuberosity (see Fig. 47.15B ). Avulsion fractures of the ASIS and AIIS are managed nonoperatively. Treatment of avulsion fractures of the ischial tuberosity is more controversial. Most experts recommend conservative treatment for avulsion injuries with less than 2 cm of displacement. Fractures with more than 2 cm of displacement might benefit from operative fixation to prevent nonunion, as well as union achieved by exuberant callus formation.

Proximal Femur Fracture

Fractures of the proximal end of the femur are classified on the basis of their relationship to the hip capsule (intracapsular or extracapsular), anatomic location (neck, trochanteric, intertrochanteric, subtrochanteric, and shaft fractures), and degree of displacement.

Femoral Neck Fractures