ANTERIOR DISLOCATION OF GLENOHUMERAL
JOINT
About 95% of shoulder
dislocations are anterior and are chiefly due to an indirect mechanism. The
most common anterior dislocation type is a subcoracoid dislocation; the most
uncommon is a subclavicular dislocation. Anterior dislocations are seen in all
age groups and are most commonly seen in adolescents and young adults. They are
often due to athletic injuries in which there is trauma to the shoulder
generally from a fall or contact to the more distal aspect of the shoulder
where the arm is placed into abduction and external rotation (i.e., a cocked
arm position for overhead throwing). It is also in this position that patients
are most likely to have a recurrent dislocation of the shoulder or have a sense
of instability of the shoulder.
The clinical appearance of anterior dislocation
demonstrates a prominent acromion and a flattened area of the lateral deltoid
region with a prominence of the humeral head anteriorly. The arm is often in
an abducted and internally rotated position with loss of passive external
rotation. The axillary nerve is located anteriorly immediately outside the
anterior inferior axillary portion of the capsular ligaments. With a
traumatic anterior dislocation of the shoulder there is often a traction-type
injury to the axillary nerve. This will result in an area of decreased
sensation in the lateral aspect of the arm as well as a weakness of deltoid
function. In addition, the musculocutaneous nerve is located 5 to 7 cm distal
to the tip of the corticoid and can be injured by compression or traction in
the anterior shoulder dislocation. This will often result in decreased
sensation in the preaxial border of the forearm and will result in weakness of
elbow flexion.
Closed
reduction of the shoulder is most commonly performed at the location of the
dislocation if a trained person is available or in an emergency department
setting. First-time dislocations are often the most difficult to reduce. The
sooner a dislocation can be safely reduced, the least likely further damage
could occur to the cartilage of the joint, to the posterior aspect of the
humeral head (Hill-Sachs lesion), or to axillary and/or musculocutaneous
nerves. In all methods of closed reduction, relaxation of the patient and the
muscles around the shoulder and axial traction are components of the successful
reduction. The less rotational manipulation, the less likely it is to create
further trauma as a result of the reduction. A commonly used method of reduction
is the Stimson maneuver. The patient is placed prone and given conscious
sedation or pain medication. The arm is gently placed over the edge of the bed
and traction applied either manually or by a static weight, as shown in Plate 1-26.
In most cases, when the patient becomes relaxed the humeral head becomes
disengaged from the anterior g enoid and the shoulder reduces into the glenoid
fossa.
