(For spinal dislocations, see Nontraumatic Spinal Subluxation; for atlantoaxial subluxation, see Atlantoaxial Subluxation; and for mandibular dislocation, see Mandibular Dislocation.)
Dislocation is a complete separation of the bone ends that normally articulate to form a joint; subluxation is a partial separation.
The most commonly dislocated limb joint is the glenohumeral (shoulder). Arterial and nerve injuries, although uncommon, are a risk with dislocations (eg, of the knee, elbow, or hip), particularly those that are not rapidly reduced.
Symptoms and signs include pain, swelling, deformity, and inability to move. Diagnosis is by plain x-rays. Treatment is usually closed reduction as soon as possible; it requires sedation and analgesia or, occasionally, general anesthesia. Neurovascular assessment is done before and after reduction. If closed reduction is ineffective, open reduction is necessary.
Glenohumeral (shoulder) dislocations:
Glenohumeral dislocations are anterior in ≥ 95% of patients; the cause is abduction and external rotation of the humerus. Occasionally, the axillary nerve is injured, or the greater tuberosity is fractured, particularly in patients > 45. The acromion is prominent; the humeral head is displaced anteriorly and inferiorly and cannot be palpated in its usual position. Sensation over the lateral deltoid is tested to check for axillary nerve injury. Treatment is usually closed reduction with using conscious sedation. The traction-countertraction technique is one of many commonly used methods of reduction (see see Traction-countertraction technique for reducing anterior shoulder dislocations.). After reduction, the joint is immobilized immediately with a sling and swathe (see see Joint immobilization as acute treatment: some commonly used techniques.).
Occasionally, dislocation is posterior—a commonly missed injury—or inferior (luxatio erecta). In patients with luxatio erecta, the brachial artery or brachial plexus is often also injured.
|Traction-countertraction technique for reducing anterior shoulder dislocations.
The patient lies on a stretcher, and its wheels are locked. One practitioner pulls on a folded sheet wrapped around the patient's chest. Another practitioner pulls the affected limb down and laterally 45°. After the humerus is free, slight lateral traction on the upper humerus may be needed.
Most elbow dislocations result from a fall on an extended, abducted arm. They are common and usually posterior. Associated injuries may include fractures, injuries to the ulnar or median nerve, and possibly injury to the brachial artery. The joint is usually flexed about 45°, and the olecranon is prominent and posterior to the humeral epicondyles; however, these anatomic relationships may be difficult to determine because of swelling. Reduction is usually with sustained, gentle traction after sedation and analgesia.
Radial head subluxations (nursemaid's elbow):
In adults, the radial head is wider than the radial neck; consequently, the head cannot fit through ligaments that tightly surround the neck. However, in toddlers (about 2 to 3 yr old), the radial head is no wider than the radial neck and can easily slip through these ligaments (radial head subluxation). Subluxation results from traction on the forearm as when a caregiver pulls a reluctant toddler forward or catches the toddler by the wrist during a fall—actions many caregivers do not remember. Symptoms may include pain and tenderness; however, many toddlers cannot describe their symptoms and simply avoid moving the affected elbow (pseudoparalysis).
Plain x-rays are normal and considered unnecessary by some experts unless an alternate diagnosis is clinically suspected. Reduction may be diagnostic and therapeutic. The elbow is completely extended and supinated, then flexed, usually without sedation or analgesia. Reduction is often marked by a subtle palpable pop or click as the radial head resumes normal position. Children may start to move the elbow after about 20 min. Immobilization is unnecessary. If pain or dysfunction lasts longer than 24 h, incomplete reduction or an occult fracture should be suspected.
Proximal interphalangeal (PIP) joint dislocations:
PIP joint dislocations are common. Dorsal dislocations, which are more common than volar, are usually due to hyperextension, sometimes displacing the volar joint structures intra-articularly. Volar dislocations can rupture the central slip of the extensor tendon, causing boutonnière deformity (see Boutonnière Deformity). Dislocations usually cause obvious deformities. A lateral x-ray should be taken with the affected digit visibly separated from the others.
For most dislocations, closed reduction using digital block anesthesia is done. Axial traction and volar force are used for dorsal dislocations, and dorsal force is used for volar dislocations. Dorsal dislocations are splinted at 15° of flexion for 3 wk. Volar dislocations are splinted at extension for 1 to 2 wk. Some dorsal dislocations require open reduction.
Most hip dislocations are posterior and result from a severe posteriorly directed force to the knee with the knee and hip flexed (eg, against a car dashboard). Complications may include arterial injury (particularly if the dislocation is anterior) with subsequent avascular necrosis of the femoral head and sciatic nerve injury. Treatment is reduction as soon as possible, followed by bed rest or joint immobilization.
Knee (tibiofemoral) dislocations:
Most anterior dislocations result from hyperextension; most posterior dislocations result from a posteriorly directed force to the proximal tibia with the knee slightly flexed. Most knee dislocations result from severe trauma (eg, high-speed motor vehicle collisions), but seemingly slight trauma, such as stepping in a hole, coupled with a twisting movement, can dislocate the knee. Some dislocations spontaneously reduce before medical evaluation, resulting in a large hemarthrosis and gross instability of the knee. Concomitant arterial injury may be seen with a spontaneously reduced knee dislocation.
Popliteal artery injury is a serious complication, but it is often a subtle injury in the early stages. The popliteal artery may be injured, even if ischemia is not initially evident. When the intima is torn, occlusion of the artery may be delayed. Thus, some experts believe that serial clinical evaluations of the distal pulse can rule out a popliteal artery injury if the pulse is normal over a period of time. However, some experts believe that angiography is indicated for every patient with a knee dislocation or with gross instability.
Treatment is immediate reduction and surgical repair.
Lateral patellar dislocations:
The usual injury mechanism is quadriceps contraction plus flexion and external tibial rotation. Most patients have an underlying chronic patellofemoral abnormality. Many dislocations spontaneously reduce before medical evaluation. Treatment is reduction; with the hip flexed, the patella is gently moved medially while the knee is extended. Reduction is followed by a cylindrical leg cast or surgical repair
Last full review/revision October 2007 by James R. Roberts, MD
Content last modified August 2013