Clinical Presentation of Glenohumeral Instability.
Last updated Tuesday, February 01, 2005
Physical examination of the dislocated shoulderAnterior dislocation The acutely dislocated shoulder is usually very painful. Muscles are in
spasm in an attempt to stabilize the joint. The humeral head may be
palpable anteriorly. The posterior shoulder shows a hollow beneath the
acromion. The arm is held in slight abduction and external rotation.
Internal rotation and adduction are usually limited. Because of the
frequent association of nerve injuries (de Laat et al, 1994) and, to a
lesser extent, vascular injuries, (Blom and Dahlback, 1970) an
essential part of the physical examination of the anteriorly dislocated
shoulder is the assessment of the neurovascular status of the upper
extremity and the charting of the findings prior to reduction.Posterior disclocation Recognition of a posterior dislocation may be impaired by the lack
of a striking deformity of the shoulder and by the fact that the
shoulder is held in the traditional sling position of adduction and
internal rotation. However, a directed physical examination will reveal
the diagnosis. The classical features of a posterior dislocation
include:
- Limited external rotation of the shoulder (often to less than zero degrees).
- Limited elevation of the arm (often to less than 90 degrees).
- Posterior prominence and rounding of the shoulder compared with the normal side.
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- Flattening of the anterior aspect of the shoulder.
- Prominence of the coracoid process on the dislocated side.
-
Asymmetry of the shoulder contours can often be best visualized by
viewing the shoulders from above while standing behind the patient.
The motion is limited because the head of the humerus is fixed on
the posterior glenoid rim by muscle forces, or the head may actually be
impaled on the glenoid rim. With the passage of time, the posterior rim
of the glenoid may further impact the fracture of the humeral head and
produce a deep hatchet-like defect or V-shaped compression fracture,
which engages the head even more securely. Patients with old, unreduced
posterior dislocations of the shoulder may have 30 to 40 degrees of
glenohumeral abduction and some humeral rotation owing to enlargement
of the groove. With long-standing disuse of the muscles about the
shoulder, atrophy will be present, which accentuates the flattening of
the anterior shoulder, the prominence of the coracoid, and the fullness
of the posterior shoulder.
Proper physical examination is essential. Rowe and Zarins (Rowe and
Zarins, 1982) reported 23 cases of unreduced dislocation of the
shoulder, of which 14 were posterior. Hill and McLaughlin (Hill and
McLaughlin, 1963) reported that in their series the average time from
injury to diagnosis was eight months. In the interval before the
diagnosis of posterior dislocation of the shoulder is made, the injury
may be misdiagnosed as a "frozen shoulder" (Hill and McLaughlin, 1963;
McLaughlin, 1963a; McLaughlin, 1963b) for which vigorous therapy may be
mistakenly instituted in an attempt to restore the range of motion.
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