The shoulder is made up of three bones: the arm bone (humerus), the wide and nearly flat shoulder bone (scapula) and the collar bone (clavicle). The head of the arm bone fits into a rounded cavity of the scapula called the glenoid. A combination of muscles and tendons keeps the arm bone centered on the shoulder socket. These tissues or tendons are called “rotator cuff” and cover the humeral head and join it to the shoulder blade. Most shoulder problems fall into four main categories: tendon inflammation or tear (bursitis or tendinitis), instability, osteoarthritis, fracture (broken bone).
The rotator cuff is a common tendon formed by the four muscles that surround the shoulder joint. The rotator cuff is responsible for joint rotation, captures the humeral head in the concavity of the scapula (glenoid cavity), to allow limb elevation, and contributes to shoulder stability to prevent joint dislocation.
Rotator cuff tears may occur as a result of trauma (falls) or sudden contraction of one of the rotators. They may also occur due to attrition rupture as a consequence of chronic tendon surface abrasion.
Total shoulder replacement is a surgery performed to treat different shoulder conditions and injuries, such as severe shoulder fractures, arthrosis, rheumatoid arthritis and rotator muscle injury.
Shoulder prosthesis or replacement or arthroplasty is a surgical procedure in which the glenohumeral joint (the joint between the head of the humerus and the scapula) is replaced with a prosthetic implant.
It is the total dislocation of the joint between the humeral head and the glenoid cavity of the scapula. When the patient undergoes a forced rotational movement of the arm together with muscle strain or compression, the resilience capacity of the joints which stabilize the articulation is exceeded and the shoulder gets dislocated.
The dislocation is typically anterior, that is, the humeral head moves forward and is typical of falling on the hand. It is more common in men than in women and affects mostly young people. When the dislocation is posterior humeral head moves back and is typical of the patient suffering seizures: epilepsy, electrocution, etc.