Scapula
The scapula is a flat triangular bone that lies on the
posterior chest wall between the 2nd and 7th ribs. On its posterior surface,
the spine of the scapula projects backward.
The lateral end of the spine is free and forms the acromion,
which articulates with the clavicle. The superolateral angle of the scapula
forms the pear-shaped glenoid cavity, or fossa, which articulates
with the head of the humerus at the shoulder joint. The coracoid process projects
upward and forward above the glenoid cavity and provides attachment for muscles
and ligaments. Medial to the base of the coracoid process is the suprascapular
notch.
The anterior surface of the scapula is concave and forms the
shallow subscapular fossa. The posterior surface of the scapula is
divided by the spine into the supraspinous fossa above and an infraspinous
fossa below. The inferior angle of the scapula can be palpated
easily in the living subject and marks the level of the 7th rib and the spine
of the 7th thoracic vertebra.
Fractures
of the Scapula
Fractures of the scapula are usually the result of severe trauma,
such as occurs in run-over accident victims or in occupants of automobiles
involved in crashes. Injuries are usually associated with fractured ribs. Most
fractures of the scapula require little treatment because the muscles on the
anterior and posterior surfaces adequately splint the fragments.
Dropped
Shoulder and Winged Scapula
The position of the scapula on the posterior wall of the
thorax is maintained by the tone and balance of the muscles attached to it. If
one of these muscles is paralyzed, the balance is upset, as in dropped
shoulder, which occurs with paralysis of the trapezius, or winged scapula,
caused by paralysis of the serratus anterior. Such imbalance can be detected by
careful physical examination.
Clavicle
The clavicle is a long, slender bone ,acts as a strut that
holds the arm away from the trunk that lies horizontally across the root of the
neck just beneath the skin. It articulates with the sternum and 1st costal
cartilage medially and with the acromion process of the scapula laterally.. It
also transmits forces from the upper limb to the axial skeleton and provides
attachment for muscles. The medial two thirds of the clavicle is convex forward
and its lateral third is concave forward. The important muscles and ligaments
attached to the clavicle.
Fractures
of the Clavicle
The clavicle is a strut that holds the arm laterally so that
it can move freely on the trunk. Unfortunately, because of its position, it is
exposed to trauma and transmits forces from the upper limb to the trunk. It is
the most commonly fractured bone in the body.
The fracture usually occurs as a result of a fall on the
shoulder or outstretched hand. The force is transmitted along the clavicle,
which breaks at its weakest point, the junction of the middle and outer thirds.
After the fracture, the lateral fragment is depressed by the weight of the arm,
and it is pulled medially and forward by the strong adductor muscles of the
shoulder joint, especially the pectoralis major. The medial end is tilted
upward by the sternocleidomastoid muscle.
The close relationship of the supraclavicular nerves to the
clavicle may result in their involvement in callus formation after fracture of
the bone. This may be the cause of persistent pain over the side of the neck.
Compression
of the Brachial Plexus, Subclavian Artery, and Subclavian Vein by the Clavicle
The interval between the clavicle and the first rib in some
patients may become narrowed and thus is responsible for compression of nerves
and blood vessels.
No comments:
Post a Comment