Mechanism of injury and associated damage
Displacement of the humeral head most often occurs via an indirect mechanism—as a result of a load applied along the axis of an abducted and externally rotated limb. At this moment, the joint capsule tears, and the head leaves the glenoid cavity of the scapula.
Injury is rarely isolated. Typical intra-articular injuries include:
- Bankart lesion: avulsion of the labrum along with the capsuloligamentous complex from the anterior edge of the glenoid rim of the scapula.
- Hill-Sachs lesion: an impression fracture on the humeral head itself. With repeated trauma, this defect increases, leading to dyscoordination and the development of arthrosis.
- Rotator cuff tears: injury to the tendons of the supraspinatus, infraspinatus, teres minor, or subscapularis muscles.
- Avulsion of the greater tubercle (occurs in 10–40% of cases).
Clinical presentation and examination
The victim assumes a characteristic forced posture: the head is tilted toward the injury, the shoulder girdle is lowered, and the healthy hand gently supports the injured arm. The limb itself is in a position of slight abduction, flexed at the elbow, and visually appears elongated.
Examination reveals the following signs:
- Contour deformation: the joint loses its normal rounded shape, the deltoid muscle is flattened, and the free acromion process is clearly palpable under the skin.
- In muscular or obese individuals, the deformation may be masked. In such cases, Marx's sign is checked: with symmetrical pressure on the shoulder girdles, the finger on the injured side sinks deeper (distal to the acromion).
- Springing resistance sign: when the doctor attempts to passively abduct, adduct, or raise the patient's arm, elastic fixation is felt; the elbow cannot be pressed against the torso.
Mandatory rule: it is necessary to thoroughly check the pulse on the radial artery and skin sensitivity. When the shoulder is abducted, the neurovascular bundle is stretched over the humeral head, threatening compression, ischemia, or paresis (n. axillaris most commonly suffers).
Classification of anterior dislocations
Depending on the degree of displacement of the humeral head relative to the coracoid process of the scapula, anterior dislocations are divided into three types:
- Subcoracoid: most of the articular head is located lateral to the vertical line of the coracoid process.
- Intracoracoid: more than half of the head crosses this line.
- Subclavicular: the entire head is displaced medially to the line of the coracoid process.
Principles and methods of closed reduction
Reduction is an emergency procedure. Its main principle consists of minimal trauma so as not to exacerbate capsule tears. This requires complete muscle relaxation. Usual administration of a local anesthetic into the joint does not provide the necessary relaxation, so the procedure is performed primarily under general anesthesia.
Basic methods of reduction:
- Kocher's maneuver. A multistage leverage method for young patients. Consists of 4 phases: traction and adduction of the elbow to the torso -> external rotation of the forearm -> bringing the elbow anteriorly and upward -> sharp internal rotation (throwing the hand onto the healthy shoulder girdle). Absolutely contraindicated in osteoporosis due to the risk of fracture of the surgical neck of the humerus.
- Janelidze's method. A muscle fatigue method. The patient lies on their side for 10–20 minutes, letting the injured arm hang off the table. Then the doctor smoothly pushes the forearm downward, making slight rotational movements until a click is heard.
- Chaklin's method. The doctor pulls the shoulder along its axis, while the other hand, inserted into the patient's armpit, pushes the humeral head outward. This is the gentlest method, indicated even for fracture-dislocations.
Post-traumatic management and surgery
After successful reduction, immobilization is required (e.g., with a Desault bandage) for a period of at least 1 month to prevent relapses. In elderly patients, the tactics are different: a lightweight sling is used for about 3 weeks to minimize the risk of hypostatic pneumonia due to limited chest excursion.
If the dislocation is chronic (more than 4 weeks), closed reduction is generally impossible due to scarring of the capsule, loss of muscle elasticity, and organized hematomas. In such cases, as well as with soft tissue interposition (e.g., biceps tendon), open reduction is indicated.
In modern practice, arthroscopy is actively used for accurate diagnosis and treatment (eliminating the Bankart lesion, repairing the cuff), making it possible to stabilize the joint without a wide incision.
Briefly: answers to topical questions
Which nerves and vessels of the brachial plexus can be injured in an anterior shoulder dislocation in addition to the axillary nerve?
In addition to the axillary nerve (n. axillaris), shoulder dislocation can involve injury to:
- median nerve (n. medianus);
- ulnar nerve (n. ulnaris);
- radial nerve (n. radialis).
When the neurovascular bundle is compressed or injured, the pulse on the radial artery (a. radialis) may be weakened or absent.
What classical methods of closed reduction of shoulder dislocation exist besides the Kocher, Janelidze, and Chaklin methods?
In addition to the listed methods, the classical methods of closed reduction of shoulder dislocation include the Hippocrates-Cooper method.
- Hippocrates-Cooper method — the doctor performs traction along the axis of the limb by the patient's hand with simultaneous pressure of the heel of their foot onto the humeral head in the axillary cavity.
In modern medical practice, this method is rarely used due to its high traumatizing nature.
Which radiographic projections are mandatory for reliable diagnosis of shoulder dislocation and exclusion of fractures?
X-ray examination for shoulder dislocation is mandatory in two projections. The standard is the anteroposterior projection. In doubtful cases, a radiograph of the scapula in a strictly lateral projection is performed.
The stages of Kocher's reduction can be remembered by the movements of the forearm: Down (traction) → Out (rotation) → Up (bringing the elbow forward) → In (hand on the opposite shoulder).
Class and exam questions
Why should Kocher's method not be used in elderly patients?
Kocher's method uses the bone as a rigid lever. In elderly people against the background of osteoporosis, this will highly likely lead to an iatrogenic impacted fracture of the surgical neck of the humerus.
How to distinguish a shoulder dislocation from a humerus neck fracture before an X-ray?
In a fracture, the springing resistance sign characteristic of a dislocation is absent, the shoulder is shortened (not elongated), is not in a forced abducted position, and bone crepitus may be determined upon palpation and movement.
Is it permissible to reduce a chronic shoulder dislocation in an outpatient clinic?
No. Dislocations lasting from 3 days to 3 weeks are reduced exclusively under anesthesia in a hospital. For a duration of more than 4 weeks, the joint capsule shrinks, scars form, and open surgical intervention is required.
What else to study on this topic
- Biomechanics of Bankart and Hill-Sachs lesions
- Recurrent shoulder dislocation: pathogenesis of instability and methods of surgical stabilization
- Specificity of arthroscopy in intra-articular shoulder injuries
- Differential diagnosis of impacted fracture of the surgical neck of the humerus
- Exercise therapy and physical therapy protocols after cast removal
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