Step-by-step diagnostic approach
Symptoms and signs of joint dislocation include pain, swelling, characteristic posturing, and the inability to move. Diagnosis is usually confirmed with plain x-rays.
History
Any patient presenting after a traumatic injury complaining of shoulder, finger, knee, or elbow pain, accompanied by painful or incomplete range of motion or characteristic posturing, needs prompt work-up with appropriate imaging.
Physical examination
Shoulder dislocation
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Patients commonly present with an arm in a characteristic position of external rotation and slight abduction. They usually have significant pain when attempting motion and are apprehensive about moving the affected joint.
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Fullness anteroinferior to the coracoid process is palpable.
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A thorough neurological examination is essential to document function of the radial, ulnar, axillary, and median nerves prior to any reduction, and the patency of the axillary artery must be confirmed by the presence of symmetrical radial pulses.
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Radial nerve function is assessed by having the patient demonstrate thumb, finger, and wrist extension, along with intact sensation over the dorsum of the hand. Ulnar nerve function is assessed by having the patient demonstrate active finger abduction and intact sensation over the medial border of the hand including the small finger and ulnar border of the ring finger. Median nerve function is assessed by having the patient demonstrate finger flexion, the OK sign, and intact sensation over the palm and thenar eminence. Axillary nerve motor function is difficult to assess secondary to pain and swelling, but intact sensation over the deltoid indicates some function of the nerve.
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While most common shoulder dislocations are anterior (>95%), posterior dislocations do occur (2% to 4%), often following electrocution or seizure, and present with the arm held in adduction and internal rotation; they will also be unable to externally rotate the affected extremity actively or passively. Inferior dislocations (i.e., luxatio erectae) occur in 0.5% of cases, and present with a palpable mass in the axilla and the arm fully abducted over the head, with the inability to adduct the arm. They often occur following accidents involving a high-energy impact such as a motorcycle collision. Inferior dislocations are associated with a high rate of complications such as tendon and ligament injuries, vascular compromise, and neurological damage.
Finger dislocation
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Patients often present with varying degrees of oedema and ecchymosis (bruising), and are apprehensive about moving the affected joint.
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Care must be taken to document the neurovascular status of the affected finger by documenting the presence of sensation on the radial and ulnar borders of the digit.
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Any abrasions or lacerations to the joint should alert the physician to the possibility of an open wound, necessitating immediate antibiotic coverage and orthopaedic consultation.
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Distal finger dislocations are often considered to be sprains and are often missed. [10] While most dislocations of the PIP, DIP, and MCP joints are dorsal, some may be volar (i.e., towards the palm). Volar injuries are often unstable and can be easily missed. [10] [26]
Patellar dislocation
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Patients often present with a swollen knee held in flexion and no obvious lateral prominence. However, it is not uncommon for patella dislocations to reduce spontaneously during transport, leg extension, or examination.
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Patella dislocation is often associated with haemarthrosis (bleeding into joint spaces) and a positive apprehension test. In this test, the patient lies supine on a table with the knee flexed to 20° to 30° and the quadriceps relaxed. The examiner carefully glides the patella laterally, observing for the apprehension sign (i.e., anxiety and resistance), which denotes a positive test.
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Tenderness to palpation over the medial patellar retinaculum indicates a tear of the medial patellofemoral ligament. If pain permits, the physician should also perform a full knee examination to determine concomitant injury to the other ligamentous structures. This may include the anterior/posterior draw and Lachman's tests to examine the cruciate ligaments, the McMurray's test to evaluate for meniscal tears, and varus and valgus stress testing to evaluate the function of various knee ligaments.
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The patient should demonstrate the ability to perform a supine straight leg raise to exclude patellar or quadriceps tendon rupture. [11] [19] [27] [28]
Elbow dislocation
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Patients typically present with the elbow held in flexion and have significant pain following any attempt at active or passive movement.
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The olecranon is prominent, and there is often a significant amount of soft tissue swelling around the elbow.
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A thorough neurological examination is imperative to document function of the radial, ulnar, and median nerves prior to any reduction. The patency of the brachial artery must be confirmed by the presence of symmetrical radial pulses.
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Radial nerve function is assessed by having the patient demonstrate thumb, finger, and wrist extension, along with intact sensation over the dorsum of the hand. Ulnar nerve function is assessed by having the patient demonstrate active finger abduction and intact sensation over the medial border of the hand including the small finger and ulnar border of the ring finger. Median nerve function is assessed by having the patient demonstrate finger flexion, the OK sign, and intact sensation over the palm and thenar eminence. Axillary nerve motor function is difficult to assess secondary to pain and swelling, but intact sensation over the deltoid indicates some function of the nerve.
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Most elbow dislocations are posterior or posterolateral (80% to 90%), but some can be anterior. In these circumstances the arm is held in extension and will appear shortened relative to the contralateral extremity. A posterior dislocation of the elbow associated with a fracture of the coronoid process and the radial head is described as the "terrible triad".
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Intra-articular dislocations are rare, but when they occur usually require general anaesthesia for closed or open reduction. [29]
Imaging
Shoulder dislocation
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The diagnosis can be made on x-rays alone.
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An anteroposterior (AP) x-ray view of the shoulder should be taken with internal and external humeral rotation. [30] These should be accompanied by axillary lateral and/or scapular Y views to confirm diagnosis. View image Each of these x-ray views is 92% sensitive for acute shoulder dislocation. [31] On a scapular Y view, the humeral head lies anteriorly to the Y in anterior dislocations, and posteriorly to the Y in posterior dislocations. View image In standard AP views, the humeral head rests anteroinferiorly to the coracoid in anterior dislocations. View image However, in posterior dislocations, the humerus can appear to be reduced. View image Therefore, axillary or scapular Y views are essential for accurate diagnosis, as up to 79% of posterior shoulder dislocations are initially misdiagnosed. View image Axillary views can correctly identify posterior dislocations in 100% of patients when combined with AP views of the shoulder. [32] [33] An axillary lateral or a modified axillary view known as the Velpeau view may also be used to confirm diagnosis.
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A possible fracture of the proximal humerus should be excluded, as attempts at reduction could further displace this fracture.
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If a vascular injury is of concern based on the physical examination, an arteriogram may be required.
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MRI scans provide excellent visualisation of soft tissue anatomy and may be ordered if any associated injuries (e.g., rotator cuff tears) are suspected.
Finger dislocation
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Clinical suspicion is based on the history and physical examination and may warrant plain film imaging of the hand or individual finger.
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AP, oblique, and lateral views of the affected joint are mandatory in evaluating a patient with a hand injury to exclude fracture and/or dislocation.
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These x-rays should be closely inspected for associated fractures and avulsions, which may indicate ligament or tendon damage.
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Further imaging is usually not necessary in the acute management of simple dislocations.
Patella dislocation
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Clinical suspicion is based on the history, and physical examination warrants AP and lateral x-ray views of the knee. However, it is not uncommon for patella dislocations to reduce spontaneously during examination or following leg extension.
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Dislocation can be confirmed on a Merchant or sunrise (infra-patellar) view, which should demonstrate the medial facet of the patella resting on the lateral trochlea of the femur.
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Images should be inspected closely for evidence of osteochondral lesions.
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CT scans are not necessary unless adequate x-rays cannot be obtained or are inconclusive.
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MRI scans of the knee joint can be useful in determining associated ligament injuries or osteochondral lesions but are not necessary to confirm an acute patellar dislocation. [28]
Elbow dislocation
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Clinical suspicion is based on the history, and physical examination should prompt radiographic imaging of the elbow.
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Dislocations are posterior in more than 90% of cases. Standard AP and lateral x-ray views of the elbow joint are the initial radiographic study of choice. View image In a posterior dislocation, these show the radius and ulna lying posterior to the distal humerus.
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The radial head should always be in line with the capitellum, and the olecranon should rest in the trochlea on a standard lateral view. View image
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In addition, AP and lateral x-ray views of the forearm are necessary to exclude associated forearm fractures (e.g., Monteggia fracture).
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A radial head/capitellum view may be used to discern radial head and coronoid fractures. Radial head fractures and coronoid fractures can be difficult to discern on plain x-rays but are readily apparent on a non-contrast CT scan of the elbow. [23]
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Further imaging to exclude other extremity injuries may be required and should be based on a thorough physical examination.
