Page 194 - Clinical Anatomy

ECA3 7/18/06 6:45 PM Page 179

The bones and joints of the upper limb 179

Inflammation of the supraspinatus tendon (‘supraspinatus tendinitis’) is
characterized by a painful arc of shoulder movement between 60° and 120°;
in this range, the tendon impinges against the overlying acromion and the
coracoacromial ligament. The investigation of soft tissue lesions around the
shoulder has been greatly facilitated by magnetic resonance imaging (MRI)
which reveals the anatomical structures in exquisite detail (Fig. 130b).

Principal muscles acting on the shoulder joint
Abductors Adductors
◊◊supraspinatus ◊◊pectoralis major
◊◊deltoid ◊◊latissimus dorsi
Flexors Extensors
◊◊pectoralis major ◊◊teres major
◊◊coracobrachialis ◊◊latissimus dorsi
◊◊deltoid (anterior fibres) ◊◊deltoid (posterior fibres)
Medial rotators Lateral rotators
◊◊pectoralis major ◊◊infraspinatus
◊◊latissimus dorsi ◊◊teres minor
◊◊teres major ◊◊deltoid (posterior fibres)
◊◊deltoid (anterior fibres)
◊◊subscapularis

Clinical features

Dislocation of the shoulder
The wide range of movement possible at the shoulder is achieved only at
the cost of stability, and for this reason it is the most commonly dislocated
major joint. Its inferior aspect is completely unprotected by muscles and it
is here that, in violent abduction, the humeral head may slip away from the
glenoid to lie in the subglenoid region, whence it usually passes anteriorly
into a subcoracoid position (Fig. 131).
The axillary nerve, lying in relation to the surgical neck of the humerus,
may be torn in this injury.
The head of the humerus is drawn medially by the powerful adductors
of the shoulder; its greater tubercle, therefore, no longer remains the most
lateral bony projection of the shoulder region, being replaced for this
honour by the acromion process. The normal bulge of the deltoid over the
greater tubercle is lost; instead there is the characteristic flattening of this
muscle.
In reducing the dislocation by Kocher’s method the elbow is flexed and
the forearm rotated outwards; this stretches the subscapularis which is
holding the humeral head internally rotated. The elbow is then swung
medially across the trunk, thus levering the head of the humerus laterally
so that it slips back into place.
In the Hippocratic method, the foot is used as a fulcrum in the axilla,