Rotator
Cuff
The rotator cuff is the name given to the tendons of the subscapularis,
supraspinatus, infraspinatus, and teres minor muscles, which are fused to the
underlying capsule of the shoulder joint. The cuff plays a very important role
in stabilizing the shoulder joint. The tone of these muscles assists in holding
the head of the humerus in the glenoid cavity of the scapula during movements
at the shoulder joint. The cuff lies on the anterior, superior, and posterior
aspects of the joint. The cuff is deficient inferiorly, and this is a site of
potential weakness.
Quadrangular
Space
The quadrangular space is an intermuscular space, located immediately
below the shoulder joint. It is bounded above by the subscapularis and capsule
of the shoulder joint and below by the teres major muscle. It is bounded
medially by the long head of the triceps and laterally by the surgical neck of
the humerus.
The axillary nerve and the posterior circumflex humeral vessels
pass backward through this space .
Rotator
Cuff Tendinitis
The rotator cuff, consisting of the tendons of the
subscapularis, supraspinatus, infraspinatus, and teres minor muscles, which are
fused to the underlying capsule of the shoulder joint, plays an important role
in stabilizing the shoulder joint. The rotator cuff presses the humeral head
into the glenoid cavity. Lesions of the cuff are a common cause of pain in the
shoulder region.
Failure of the cuff is due to either wear or tear. Wear is
age related. Excessive overhead activity of the upper limb may be the cause of
tendinitis, although many cases appear spontaneously. During abduction of the
shoulder joint, the supraspinatus tendon is exposed to friction against the
acromion. Under normal conditions, the amount of friction is reduced to a
minimum by the large subacromial bursa, which extends laterally beneath the
deltoid. Degenerative changes in the bursa are followed by degenerative changes
in the underlying supraspinatus tendon, and these may extend into the other
tendons of the rotator cuff. Clinically, the condition is known as subacromial
bursitis, supraspinatus tendinitis, or pericapsulitis. It is
characterized by the presence of a spasm of pain in the middle range of
abduction, when the diseased area impinges on the acromion. Extensive acute
traumatic tears are best repaired surgically as soon as possible. Small chronic
cuff injuries are best managed without surgery using nonsteroidal
anti-inflammatory drugs and muscle exercises.
Rupture
of the Supraspinatus Tendon
In advanced cases of rotator cuff tendinitis, the necrotic
supraspinatus tendon can become calcified or rupture. Rupture of the tendon
seriously interferes with the normal abduction movement of the shoulder joint.
It will be remembered that the main function of the supraspinatus muscle is to
hold the head of the humerus in the glenoid fossa at the commencement of
abduction. The patient with a ruptured supraspinatus tendon is unable to
initiate abduction of the arm. However, if the arm is passively assisted for
the first 15° of abduction, the deltoid can then take over and complete the
movement to a right angle
.
.
Arterial
Anastomosis around the Shoulder Joint
The extreme mobility of the shoulder joint may result in kinking
of the axillary artery and a temporary occlusion of its lumen. To compensate
for this, an important arterial anastomosis exists between the branches of the
subclavian artery and the axillary artery, thus ensuring that an adequate blood
flow takes place into the upper limb irrespective of the position of the arm
Branches
from the Subclavian Artery
■■ The
suprascapular artery, which is distributed to the supraspinous and infraspinous
fossae of the scapula
■■ The
superficial cervical artery, which gives off a deep branch that runs down the
medial border of the scapula
Branches from the Axillary Artery
Branches from the Axillary Artery
■■ The
subscapular artery and its circumflex scapular branch supply the subscapular
and infraspinous fossae of the scapula, respectively.
■■ The
anterior circumflex humeral artery
■■ The
posterior circumflex humeral artery Both the circumflex arteries form an
anastomosing circle around the surgical neck of the humerus.
Arterial
Anastomosis and Ligation of the Axillary Artery
The existence of the anastomosis around the shoulder joint is
vital to preserving the upper limb should it be necessary to ligate the
axillary artery.
