Dislocations and Subluxations (Encyclopedia of Medicine)
In medicine, the terms dislocation and subluxation refer to the displacement of bones that form a joint. These conditions affecting the joint most often result from trauma that causes adjoining bones to no longer align with each other. A partial or incomplete dislocation is called a subluxation.
In a healthy joint, the bones are normally held together with tough, fibrous bands called ligaments. These ligaments are attached to each bone along with a fibrous sac surrounding the joint called the articular capsule or joint capsule. The ligaments and joint capsule are relatively strong and nonelastic but permit movement within normal limits for each particular joint. In the event of a dislocation, one of the bones making up the joint is forced out of its natural alignment from excessive stretching and tearing of the joint ligaments and capsule. Muscles and tendons surrounding the joint are usually stretched and injured to some degree.
Causes and symptoms
A violent movement at the joint that exceeds normal limits usually causes a joint dislocation. Although dislocations often result from trauma, they sometimes occur as a result of disease affecting the joint structures. In the process of the dislocation, there is tearing of the ligaments and the articular capsule,...
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Dislocations and Subluxations (Encyclopedia of Nursing & Allied Health)
Dislocation is the displacement of bones that form a joint. A joint is where two or more bones meet. In a dislocation, the surfaces of the bones that normally articulate with each other (i.e., join together to allow movement) no longer line up correctly, and none of the joint surfaces are touching. Subluxation is a partial dislocation, so some contact remains between the joint surfaces.
Ligaments and joint capsules are tough bands of connective tissue that hold the bones together. Muscles and tendons also help strengthen joints. Any event that subjects a joint to unusual force may cause a dislocation by stretching and tearing these supporting structures. This trauma allows one or more of the bones to go out of alignment, so that the articular (joint) surfaces of the bones no longer have their correct relationship with each other. A dislocation may affect any size joint in the body. The most common dislocations of the major joints involve the shoulder, patella (i.e., kneecap), and elbow. The process of restoring the bones to their correct alignment is known as reduction.
Several important problems that may arise from a dislocation require urgent attention. First, the injury is almost always very painful until the dislocation is reduced. Second, the deformity produced by the dislocation may stretch, kink, or tear adjacent major blood vessels or nerves. This effect on the neurovascular structures may severely threaten the circulation or nerve function in the more distal part of the limb, and may cause irreversible damage if not corrected in time. Complete dislocation of the knee (i.e., not just the kneecap) is especially dangerous in this regard. A different problem, which particularly affects the hip, is that part of the bone may receive its normal blood supply through the joint itself; when the joint dislocates, that part of the bone may lose its blood supply and become ischemic. Finally, hemorrhage and swelling progressively develop in the joint and the surrounding structures, so relocating the bones may become more difficult as time elapses. For all these reasons, prompt reduction of a dislocation is important.
Physicians describe a dislocation by referring to the movement of the more distal of the bones involved. Thus, an anterior dislocation of the shoulder is one in which the humerus shifts anteriorly with respect to the shoulder socket. Additionally, a dislocation may be open or closed.
This refers to the skin overlying the joint, meaning that an open injury is one in which the joint surfaces are exposed to the environment outside the body. An open injury creates a serious risk of bacterial infection of the joint. In a closed dislocation the skin remains intact.
Causes and symptoms
Common causes of dislocations and subluxations include falls, motor vehicle accidents, sports, and horseplay. These activities may apply isolated or combined forces such as stretching, twisting, and compression to the affected joint. The force involved may be as minor as yawning, which may allow the mandible to slip out of the temporomandibular joint. Conditions that predispose to dislocation include:
- shallow or abnormally formed joints
- joints weakened by disease or previous dislocation
- previous joint replacement surgery
- medical diseases that contribute to falls
A thorough history is important to determine:
- the circumstances that led to the injury
- the time at which the injury occurred
- the type of force applied to the joint
- the likelihood of other associated injuries
- other medical and orthopedic history
- medications and allergies
- use of alcohol and illicit drugs
- time of the last oral intake
- tetanus status, if there are any open wounds
The examination must always start with the ABCs of resuscitation: airway, breathing, and circulation. Doctors and nurses must not allow a painful, deformed joint to distract them from potentially life-threatening injuries to the head, neck, chest, or abdomen. The examination of a dislocated joint typically will show deformity, tenderness, and resistance to movement. There may not be visible swelling. The distal neurovascular examination is very important dislocation that causes loss of the pulse in a limb is a far greater emergency than one in which the circulation is intact. Also, later exams will determine whether efforts to reduce the dislocation have affected the neurovascular function. The nurse must frequently inspect the injured limb for color, pulse, and function of motor and sensory nerves.
Standard x-ray pictures of a joint usually will show a dislocation, and may show the additional presence of a fracture or other injury. Occasionally, special views or even advanced techniques such as computerized tomography (CT) may be necessary to demonstrate the problem.
A shoulder dislocation is a condition in which the head of the upper arm bone (humerus) is dislocated from the socket (glenoid). It can dislocate forward, backward, or downward. The injury is extremely painful, and may happen when throwing an object forcefully. The affected arm will be put in a sling, and instructions for the care of the injury will be given to the patient. The area should be iced three or four times every day, and the shoulder should be exercised to speed healing and prevent reinjury in the future.
A different condition that may be mistaken for a dislocation is acromioclavicular separation, often called AC separation or shoulder separation. This is technically a sprain, involving the stretching and tearing of ligaments that hold the tips of the acromion (i.e., part of the scapula) and the clavicle near each other. Shoulder separation typically results from a direct blow to the top of the shoulder, often in a young man, as may occur in contact sports or a motorcycle accident. The injury is painful, the patient will not want to move the shoulder, and the shoulder may lose its normal contour. The part of the shoulder just beyond the tip of the clavicle will be very tender. Regular x-ray pictures may not demonstrate a widening of the space between these two bony areas.
A patellar or patellofemoral dislocation (dislocation of the knee cap) is another common injury. In this condition, the knee cap moves laterally (to the outside of the leg) due to sideways motion of the lower leg while the upper leg is stationary. The injury will present with swelling and pain in the knee area. On palpation, the patella is discovered to be in the wrong position. Weakness of the joint makes it more susceptible to rein-jury, and certain exercises may be prescribed to strengthen the area. Patellar injury also makes a person more likely to develop arthritis in the joint.
Another injury, common only in children between the ages of one to four, is subluxation of the radial head, or Nursemaid's elbow. This condition may also cause damage to the annular ligament. The case of Nursemaid's elbow demonstrates some of the challenges and pitfalls of diagnosing dislocation or subluxation. The cause is a simple, direct pull on the outstretched hand or wrist of a small child; this may occur when dangling a toddler by the hands in play, or when lifting a child who has fallen. The pulling action causes the head of the radius to move slightly out of position at the elbow. Often the caregiver may not associate such an innocent act with the onset of the problem. The child keeps the arm still against the body and cries if someone moves it. Often, the caregiver and even the medical staff will mistakenly believe that the problem lies in the wrist or the shoulder. The nurse and doctor must question the caregiver in detail about the events leading to the onset of pain. Then, a careful examination will show that even slight supination of the forearm, which rotates the radius, is the motion that causes pain and resistance. X-ray studies are of little use in this condition, because the head of the radius is not displaced enough to appear abnormal.
Immediate treatment of a dislocation involves splinting the affected area. Splinting diminishes pain, protects the joint and nearby structures from further injury, and assists in transporting the patient. The patient may effectively splint the joint by supporting it with the hand; otherwise, the initial care provider may use pillows, a sling, folded cardboard, or other handy material to fit around the area. Application of ice helps control swelling and pain. The patient must receive nothing by mouth, in case anesthesia is necessary. Care providers should remove any rings or other constricting items distal to the site of injury. The patient will appreciate prompt medication for pain.
Emergency department reduction
Successful reduction of many dislocations and subluxations is possible in the emergency department (ED). Often, the physician will order intravenous (IV) medications such as narcotics (i.e., fentanyl) or morphine sulfate (Morphine) and benzodiazepines (i.e., lorazepam [Ativan] or midazolam [Versed]) to relieve pain, sedate the patient, and relax the surrounding muscles. Then the physician will employ a suitable technique of manipulating the joint in order to bring the bones back into alignment.
Reduction in the ED is not always successful, sometimes due to the patient's severe pain or anxiety. In other cases, swelling and entrapment of structures around the joint prevent the bones from returning to their proper position. In these instances, the patient will require general anesthesia in the operating room (OR). Also, in cases of open dislocation, the orthopedist usually will take the patient to the OR in order to thoroughly flush contamination from the joint.
The pain and limitation of joint movement will improve substantially after successful reduction. After any manipulation the nurse and physician must recheck and document the neurovascular function in the limb. In almost all cases the physician will request repeat x-ray studies in order to demonstrate that the reduction was
Anterioroward the front of the body.
Benzodiazepineshe class of drugs related to diazepam (Valium), used to relax muscles and cause sedation.
Distalarther from the center of the body.
Humerushe arm bone, connecting the shoulder and the elbow.
Ischemicuffering from lack of arterial blood supply.
Narcoticshe class of drugs related to morphine, used to relieve pain.
Neurovascularertaining to the function of nerves and blood vessels.
Prostheticeferring to an artificial part of the body.
Radiushe bone of the forearm which joins the wrist on the same side as the thumb.
Reductionhe restoring of bones to their correct alignment.
Scapulahe shoulder blade.
Splintingreventing movement of a joint.
Supinationhe twisting motion of the forearm, wrist, and hand that turns the palm upward.
Temporomandibularelating to the meeting point of the skull and the lower jaw.
successful. The physician will usually order pain medicine and a splint or support for the injured area. Most patients will be able to go home after reduction of a dislocation, although a patient who receives heavy sedation or anesthesia may require several hours of recovery before discharge. The nurse will need to instruct the patient and caregivers regarding:
- allowable movement of the injured area
- proper application of a splint or other support
- use of ice (Heat treatments are contraindicated in acute and subacute stages.)
- dosing and side effects of medications
- warning signs of impending problems with neurovascular function
- plans for follow-up appointments
Almost all patients who have a dislocation will need follow-up with an orthopedist. The injured ligaments and other joint structures may require many weeks to heal. Exercises and physical therapy will help improve function and decrease pain. Recurring dislocation or persistent loss of function may lead to surgical reconstruction, or even replacement of a joint.
Numerous factors influence the ultimate outcome of a dislocation. These include:
- extent of the original injury to the joint
- presence of associated injuries
- time delay to reduction of the dislocation
- the patient's prior overall fitness as well as previous function of the affected joint
- the patient's motivation to exercise and strengthen the injured area
- the patient's ability to modify behavior and avoid re-injury
For some patients, especially athletes, decrease in limb function and time lost from normal activities may jeopardize career prospects and future earning potential. The patient, family, or coaches may put pressure on the doctor and support staff for a rapid and complete recovery, although this may not always be possible.
Health care team roles
Emergency medical technicians perform initial rescue, begin to stabilize the patient, splint the injured area, and transport the patient to the hospital. The nurse receives the patient at the ED, performs further assessment, and orders x-ray tests directly or after consulting with the physician, depending on local policies. Later, the nurse carries out orders for medications and other treatments as directed by the physician, monitors the patient throughout the hospital stay, and prepares the patient for discharge. The aide assists the nurse.
A radiology technician performs the x-ray studies ordered by the doctor or nurse. Later, a social worker may help coordinate care after discharge. The physical therapist works to rehabilitate the patient through exercise, massage, and other treatments. A certified athletic trainer (ATC) is sometimes employed in an effort to reduce the possibility of repeated injury in susceptible persons.
Prevention of dislocations and subluxations starts with awareness of inherently dangerous activities (e.g., riding motorcycles, climbing ladders, consuming alcohol) and avoidance of behavior that may cause specific injuries (e.g., crossing the legs for prosthetic hip dislocation, pulling toddler by hand for Nursemaid's elbow). Participants should use appropriate protective equipment for work or sports, maintain good overall fitness, and allow sufficient time for healing of a previously injured body part before resuming full activity.
Menkes, Jeffrey S. "Initial Evaluation and Management of Orthopedic Injuries." In Emergency Medicine: A Comprehensive Study Guide, edited by Tintinalli, Judith E., Gabor D. Kelen, and J. Stephan Stapczynski. 5th ed. New York: McGraw-Hill, 2000, pp.1739-53.
American Academy of Orthopedic Surgeons. 6300 North River Road, Rosemont, IL 60018-4262. (800) 346-AAOS. <<a href="http://www.aaos.org">http://www.aaos.org>.
American Academy of Orthopedic Surgeons. "Dislocated Shoulder." <<a href="http://orthoinfo.aaos.org/fact/thr_report.cfm?Thread_ID=171&topcategory=Shoulder">http://orthoinfo.aaos.org/fact/thr_report.cfm?Thread_ID=171... >.
Medline Plus. "Knee Cap Dislocation." Medical Encyclopedia. <<a href="http://www.nlm.nih.gov/medlineplus/ency/article/001070.htm">http://www.nlm.nih.gov/medlineplus/ency/article/001070.htm>.
Kenneth J. Berniker, M.D.