Fracture and dislocation

Disease/Disorder

Anatomy or system affected: Arms, bones, hands, hips, joints, knees, legs, musculoskeletal system

Specialties and related fields: Emergency medicine, orthopedics, sports medicine

Definition: A fracture is a break in a bone, which may be partial or complete; a dislocation is the forceful separation of bones in a joint.

Causes and Symptoms

A fracture is a linear deformation or discontinuity of a bone produced by the application of a force that exceeds the modulus of elasticity (ability to bend) of a bone. Normal bones require excessive force to fracture. Disease, tumor-related diseases, or tumors themselves weaken the physical structure of bones, which reduces their ability to withstand an impact. Bones respond to stresses placed upon them and can thus be strengthened through physical conditioning and made more resistant to fracture. This is a normal part of training in many athletic activities.

Fractures are classified according to the type of break or, more correctly, by the plane or surface that is fractured. A break that is at a right angle to the axis of the bone is called transverse. An oblique fracture is similar, but is found at any angle, other than perpendicular to the main axis of the bone. If a twisting force is applied, the break may be spiral, or twisted. A comminuted fracture is a break that results in two or more fragments of bone. If the pieces of bone remain in their original positions, the fracture is undisplaced. In a displaced fracture, the portions of bone are not properly aligned.

If bones do not penetrate the skin, the fracture is called closed, or simple. When bones protrude through the skin, the result is an open, or compound, fracture. Other types of fractures are associated with pathologic or disease processes. A stress fracture results from repeated stress or trauma to the same site of a bone. None of the individual stresses is sufficient to cause a break. If these stresses cause a callus to form, the bone will be strengthened and actual separation of fragments will not occur. A pathologic fracture occurs at the site of a tumor, infection, or other bone disease. A compression fracture results when bone is crushed; the force applied is greater than the ability of the bone to withstand it. A greenstick fracture is an incomplete separation of bone.

The diagnosis of a fracture is based on several criteria: instability, pain, swelling, deformity, and ecchymosis. The most reliable diagnostic criterion is instability. Pain is not universally present at a fracture site. Swelling may be delayed and occur at some time after a fracture is sustained. Deformity is obvious with open fractures but may not be apparent with other, undisplaced breaks.

Ecchymosis is a purplish patch caused by bleeding into skin; it will not be present if blood vessels are not broken. A definitive diagnosis is made with two-plane film X-rays taken at the site of a fracture at right angles to one another. If the fracture site is visually examined and palpated shortly after the injury occurs, an accurate tentative diagnosis may be made; this should be confirmed with X-rays as soon as it is convenient. Occasionally, an X-ray will not show undisplaced or chip fracture. If a patient experiences symptoms of pain, swelling, or ecchymosis but has a negative X-ray for a fracture, the site should be immobilized and X-rayed again in two to three weeks.

Fractures occur most commonly in the extremities: arms or legs. Such fractures must be evaluated to determine if injuries have occurred to other tissues such as nerves or blood vessels. The presence of bruising or ecchymosis indicates blood vessel damage. The absence of peripheral pulses with severe bruising indicates that the major arteries are injured. Venous flow is more difficult to evaluate. The venous circulation is a lower pressure system than arterial, so venous bleeding can be considered of lesser importance and therefore temporarily tolerated.

Neurologic functioning may be assessed by the ability of the patient to contract muscles or sense skin touches or pinpricks. Temporary immobilization may be necessary before nerve status can be evaluated accurately.

An open fracture creates a direct pathway between the skin surface and underlying tissues. If bacteria contaminate the site, an opportunity for osteomyelitis (infection of the bone) to form is created. Inadequate treatment by the initial surgeon may result in skin loss, delayed union, loss of joint mobility, osteomyelitis, and even amputation.

Skin damage may or may not be related to a fracture. When skin integrity is broken over or near a fracture site, bone involvement must be assumed. If there is infection of the fracture site; appropriate antibiotics are normally administered. If skin damage is extensive, final surgical reduction of the underlying fracture may have to be delayed until the skin is healed.

Delayed union refers to the inability of a fractured bone to heal. This is a potentially serious problem, as normal stability is not possible as long as a fracture exists. Joints may not function normally in the presence of a fracture. If a fracture heals improperly, bones may be misaligned and cause pain with movement, leading to limitations of motion. If the bones are affected by osteomyelitis, the infection may spread to the joint capsule and reduce the normal range of motion for the bones or the joint. Amputation may become necessary if infection becomes extensive in the area of a fracture. An infection, which becomes firmly established in bones or spreads widely into adjacent muscle tissue, may lead to cellulitis or gangrene and may compromise a portion of an extremity. Amputation may be performed if the pathologic process cannot be treated with antibiotics and/or surgery.

Adequate blood supply to tissues is critical for survival. In an extremity, the maximum time limit for complete ischemia (lack of blood flow) is six to eight hours; after that time, the likelihood of later amputation increases. Pain, pallor, pulselessness, and paralysis are indicators of impaired circulation. When two of these signs are present, the possibility of vascular damage must be thoroughly explored.

Dislocations occur at joints and are caused by an applied force that is greater than the strength of the ligaments and muscles that keep a joint intact. The result is a stretching deformity or injury to a joint and an abnormal movement of a bone out of the joint. Accidental trauma, commonly the result of an athletic injury or automobile accident, is the most common cause of a dislocation. Joints that are frequently dislocated include the shoulder and digits (fingers and toes). Dislocations of the ankle and hip are infrequent but serious; they require immediate management. Dislocations may accompany fractures, but the two injuries need not occur together.

When dislocations are reduced, the bones of the joint are returned to normal position. Reduction of a dislocation is accomplished by relaxing adjacent muscles and applying traction (pulling force) to the bone until it returns to its normal position within the joint. For most dislocations of the shoulder, the victim lies in a prone position and the dislocated arm hangs down freely. Gradual traction is applied until reduction occurs. This can be accomplished by bandaging a pail to the arm and slowly filling it with water. Alternatively, the victim can hold a heavy book while the muscles of the arm are allowed to relax until the dislocation is reduced. Such treatments are usually reserved for situations in which medical assistance is unavailable. Digits are reduced in a similar manner, by gentle pulling of the end of the finger or toe. Ankle and hip dislocations are potentially more serious because these joints are more complex and have extensive blood supplies. Reduction of dislocated ankles and hips should be undertaken by qualified medical personnel in an expedited manner.

After reduction, competent medical personnel should evaluate all dislocations. With dislocated digits, long-term damage is relatively unlikely but can occur because of damage to a ligament sustained in the initial injury. Dislocations of the shoulder may be accompanied by a fracture of the clavicle or collarbone and may involve nerve damage in the shoulder joint. Dislocations of the ankle and hip may lead to avascular necrosis (damage to the bone as a result of inadequate blood supply) if not evaluated and reduced promptly.

Treatment and Therapy

Fractures are usually treated by reduction and immobilization. Reduction, which refers to the process of returning the fractured bones to the normal position, may be either closed or open. Closed reduction is accomplished without surgery by manipulating the broken bone through overlying skin and muscles. Open reduction requires surgical intervention in which the broken pieces are exposed and returned to the normal position. Orthopedic appliances may be used to hold the bones in the correct position. The most common of these appliances are pins and screws, but metal plates and wires may also be employed. Orthopedic appliances are usually made of stainless steel. These may be left in the body indefinitely or may be surgically removed after healing is complete. Local anesthesia is usually used with closed reductions; open reductions are performed in an operating room, under sterile conditions using general anesthesia.

Immobilization is generally accomplished by the use of a cast. Casts are often made of plaster, but they may be constructed of inflatable plastic. It is important to hold bones in a rigid, fixed position for a sufficient length of time for the broken ends to unite and heal. The cast must be loose enough, however, to allow blood to circulate. Padding is usually put in place before plaster is applied to form a cast. Whenever possible, the newly immobilized body part is elevated to reduce the chance of swelling in the cast, which would compromise the blood supply to the fracture site and the portion of the body beyond the cast. Casts should be checked periodically to ensure that they do not impair circulation.

The broken bone and accompanying body part must be placed in an anatomically neutral position. This is done to minimize postfracture disability and improve the prospect for rehabilitation. The length of time that a fractured bone is immobilized is highly variable and dependent on a number of factors.

Traction may also be used to immobilize a fracture. Traction is the external application of force to overcome muscular resistance and hold bones in a desired position. Commonly, holes are drilled through bones and pins are inserted; the ends of these pins extend through the surface of the skin. Part of the body is fixed in position through the use of a strap or weights, and wires are attached to the pins in the body part to be stretched. Weights or tension is applied to the wires until the broken bone parts move into the desired position. Traction is maintained until healing has occurred.

Individual ends of a single fractured bone are sometimes held in position by external pins and screws. Holes are drilled through the bone, and pins are inserted. The pins on opposite sides of the fracture site are then attached to each other with threaded rods and locked in position by nuts. This process allows a fractured bone to be immobilized without using a cast.

Different bones require different amounts of time to heal. Furthermore, age is a factor in fracture healing. Fractures in young children heal more quickly than do broken bones in adults. Elderly individuals typically require even more time for healing. The availability of nutrients like calcium and vitamin D also affects the speed with which a fracture heals.

Delayed union of fractures is a term applied to fractures that either do not heal or take longer than normal to heal; there is no precise time frame associated with delayed union. Nonunion refers to fractures in which healing is not observed and cannot be expected even with prolonged immobilization. X-ray analysis of a nonunion will show that the bone ends have sclerosed (hardened), that the ends of the marrow canal have become plugged, and that a gap persists between the ends of a fractured bone. Nonunion may be caused by inadequate blood supply to the fracture site, which leads to the formation of cartilage instead of new bone between the broken pieces of bone. Nonunion may also be caused by injury to the soft tissues that surround a fracture site. This damage impairs the formation of a callus and the reestablishment of an adequate blood supply to the fracture site; it is frequently seen in young children. Inadequate immobilization may also allow soft tissue to enter the fracture site by slipping between the bone fragments, and may lead to nonunion. Respect for tissue and minimizing damage in the vicinity of a fracture, especially with open reduction, will minimize problems of nonunion. Subjecting the nonuniting fracture site to a low-level electromagnetic field will usually stimulate osteoblastic (bone-forming cell) activity and lead to healing.

The epiphyseal plate is the portion of bone where growth occurs. Bony epiphyses are active in children until they attain their adult height, at which time the epiphyses become inactive and close. Once an epiphysis ceases to function, further growth does not occur. In children, a fracture involving the epiphyseal plate is potentially dangerous because bone growth may be interrupted or halted. This situation can lead to inequalities in the length of extremities or impaired range of movement in joints. Accurate reduction of injuries involving an epiphyseal plate is necessary to minimize subsequent deformity. A key factor is blood supply to the injured area: If adequate blood supply is maintained, epiphyseal plate damage is minimized.

Fractures of the spinal vertebrae are potentially very dangerous because they can cause injury to the nerves and tracts of the spinal cord. Fractures of the vertebrae are commonly sustained in automobile accidents, athletic injuries, falls from heights, and other situations involving rapid deceleration. When vertebrae are fractured, the spinal cord can be compromised. Spinal cord injury can be direct and cut all or a portion of the spinal nerves at the site of the fracture. The extent of the damage is dependent on the level of the injury. An accident that completely severs the spinal cord will lead to a complete loss of function for all structures below the level of injury. Since spinal nerves are arranged segmentally, cord damage at a lower level involves compromise of fewer structures. As the level of injury becomes higher in the spinal cord, more vital structures are involved. Transection of the spinal cord in the neck usually leads to complete paralysis of the entire body; it can cause death if high enough to cut the nerves controlling the lungs. Individuals in whom vertebral fractures and thus spinal cord injuries are suspected must have the spinal column immobilized before they are moved. Only a highly skilled professional should undertake reduction of spinal cord fractures.

When bones having large marrow cavities such as the femur (thighbone) are fractured, fat globules may escape from the marrow and enter the bloodstream. Such a fat globule is then called an embolus (plural is emboli). Fat emboli are potentially dangerous in that they can become lodged in the capillaries of the lungs. This causes pain and can lead to impaired oxygenation of blood, a condition called hypoxemia. About 10 to 20 percent of individuals sustaining a fractured femur also have central nervous system depression and skin petechiae (minute spots caused by hemorrhage or bleeding into the skin) in addition to hypoxemia in the two to three days after the injury. This triad of signs is called fat embolism syndrome. It is treated medically with oxygen, steroids, and anticoagulant drugs.

Perspective and Prospects

Fractures rarely threaten a patient's life directly, and injuries to the brain, heart, circulatory system, and abdominal cavity must receive priority of treatment. It is imperative, however, not to move a patient in whom a fracture is suspected without first immobilizing the potential fracture site. This is especially true with suspected fractures of the spine. Instability may not be apparent when a patient is lying down but can become catastrophic if the person is moved without proper preparation and immobilization.

Crush injuries of the spinal cord are relatively common among victims of osteoporosis. Osteoporosis is a pathological syndrome defined by a decrease in the density of a bone below the level required for mechanical support and is frequently associated with a deficiency of calcium, problems related to calcium in the body, or a rate of bone cell breakdown that is greater than the rate of bone cell remodeling. Crush fractures occur when the bones become so weak that the weight of the upper portion of the body is greater than the ability of the vertebrae to support it. These crush injuries may occur slowly over time and cause no serious injury to the underlying spinal cord. The resulting deformity of the spine, however, impairs movement. There are limited treatments for osteoporotic crush fractures of the vertebrae. Most of the treatments aim to strengthen nearby muscles and aid in nutritional deficiencies causing the osteoporosis. However surgeries such as vertebroplasty, balloon kyphoplasty, and spinal fusion are available as last-line treatments for reoccurring or nonhealing (painful) vertebral fractures.

Occupational exposures may lead to fractures and dislocations. Professional athletes are clearly at increased risk for skeletal injuries. These individuals are also usually well conditioned, however, and so can withstand increased impacts and blows to the body. Many are also trained in methods that minimize the force of impact; they know how to fall properly.

The vast proportions of workers are not conditioned and are given minimal training to avoid situations that lead to fractures. Accident analysis reveals that carelessness is the most common predisposing factor. Workers operating without safety equipment such as belaying lines or belts may become overconfident. In such a situation, slips or falls can occur, and fractures result. Unsafe equipment can lead to hazardous situations and cause fractures or dislocations. Machinery that is not properly maintained can fail; parts may become detached, hit nearby workers, and cause fractures.

Recreational activities also result in fractures. Individuals who once were well conditioned may engage in sports without proper equipment and sustain fractures or dislocations. Contact sports such as hockey, football, and basketball are primary examples of such activities. Riding bicycles and motorized recreational vehicles without proper safety equipment can lead to serious skeletal injuries. Activities such as rock climbing are inherently dangerous. With proper training and use of safety equipment, accidents can be reduced or their severity minimized. The keys to avoiding fractures and dislocations when participating in recreational activities are receiving proper instruction and training, employing adequate safety equipment, and using common sense by avoiding difficult or hazardous situations that are beyond one's physical abilities or skill level.

Key Terms

anesthesia: a state characterized by loss of sensation, caused by or resulting from the pharmacological depression of normal nerve function

callus: a hard, bone-like substance made by osteocytes that is found in and around the ends of a fractured bone; it temporarily maintains bony alignment and is resorbed after complete healing or union of a fracture occurs

ecchymosis: a purplish patch on the skin caused by bleeding; the spots are easily visible to the naked eye

embolus: an obstruction or occlusion of a vessel (most commonly, an artery or vein) caused by a transported blood clot, vegetation, mass of bacteria, or other foreign material

epiphysis: the part of a long bone from which growth or elongation occurs

instability: excessive mobility of two or more bones caused by damage to ligaments, the joint capsule, or fracture of one or more bones

ischemia: a local anemia or area of diminished or insufficient blood supply due to mechanical obstruction, commonly narrowing of an artery

kyphoplasty: similar to vertebroplasty (see below), but uses a special balloon in order to restore vertebral height and lessen spinal deformity

osteoblast: a bone-forming cell

osteocyte: a bone cell

paralysis: the loss of power of voluntary movement or other function of a muscle as a result of disease or injury to its nerve supply

petechiae: minute spots caused by hemorrhage or bleeding into the skin; the spots are the size of pinheads

prone: the position of the body when face downward, on one's stomach and abdomen

pulse: the rhythmical dilation of an artery, produced by the increased volume of blood forced into the vessel by the contraction of the heart

transection: a partial or complete severance of the spinal cord

vertebroplasty: medical procedure where acrylic cement is injected into the body of the vertebra for stabilization

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