Trauma to the shoulder is common. Injuries range from a separated shoulder resulting from a fall onto the shoulder to a high-speed car accident that fractures the shoulder blade (scapula) or collar bone (clavicle). One thing is certain: everyone injures his or her shoulder at some point in life.
Anatomy

Shoulder Anatomy


The shoulder is made up of three bones:
Scapula (shoulder blade), Clavicle (collar bone), Humerus (arm bone), These bones are joined together by soft tissues (ligaments, tendons, muscles, and joint capsule) to form a platform for the arm to work.

The shoulder is made up of three joints:
Glenohumeral joint, Acromioclavicular joint, Sternoclavicular joint

The shoulder also has one articulation, which is the relationship between the scapula (shoulder blade) and the chest wall.

The main joint of the shoulder is the glenohumeral joint. This joint comprises a ball (the humeral head) on a golf-tee-shaped joint (the glenoid of the scapula).

The bones of the shoulder are covered by several layers of soft tissues.

The top layer is the deltoid muscle, a muscle just beneath the skin, which gives the shoulder a rounded appearance. The deltoid muscle helps to bring the arm overhead.
Directly beneath the deltoid muscle is sub-deltoid bursa, a fluid-filled sac, analogous to a water balloon.

Types of Shoulder Injuries

There are many types of shoulder injuries:

  • Fractures are broken bones. Fractures commonly involve the clavicle (collar bone), proximal humerus (top of the upper arm bone), and scapula (shoulder blade).
  • Dislocations occur when the bones on opposite sides of a joint do not line up. Dislocations can involve any of three different joints.
    • A dislocation of the acromioclavicular joint (collar bone joint) is called a « separated shoulder. »
    • A dislocation of the sternoclavicular joint interrupts the connection between the clavicle and the breastbone (sternum).
    • The glenohumeral joint (the ball and socket joint of the shoulder) can be dislocated toward the front (anteriorly) or toward the back (posteriorly).
  • Soft-tissue injuries are tears of the ligaments, tendons, muscles, and joint capsule of the shoulder, such as rotator cuff tears and labral tears.

The following discussion will focus on fractures and dislocations.

Cause

Fractures

Fractures of the clavicle or the proximal humerus can be caused by a direct blow to the area from a fall, collision, or motor vehicle accident.

Because the scapula is protected by the chest and surrounding muscles, it is not easily fractured. Therefore, fractures of the scapula are usually caused by high-energy trauma, such as a high speed motor vehicle accident. Scapula fractures are often associated with injuries to the chest.

Shoulder Dislocations

  • Anterior dislocations of the shoulder are caused by the arm being forcefully twisted outward (external rotation) when the arm is above the level of the shoulder. These injuries can occur from many different causes, including a fall or a direct blow to the shoulder.
  • Posterior dislocations of the shoulder are much less common than anterior dislocations of the shoulder. Posterior dislocations often occur from seizures or electric shocks when the muscles of the front of the shoulder contract and forcefully tighten.

Shoulder Separations

Dislocations of the acromioclavicular joint can be caused by a fall onto the shoulder or from lifting heavy objects. The term « shoulder separation » is not really correct, because the joint injured is actually not the true shoulder joint.

Symptoms of fractures

Symptoms of fractures about the shoulder are related to the specific type of fracture.

General Findings

  • Pain
  • Swelling and bruising
  • Inability to move the shoulder
  • A grinding sensation when the shoulder is moved
  • Deformity — « It does not look right »

Specific Findings: Clavicle Fracture

  • Swelling about the middle of the collarbone area
  • An area that may have a « bump, » which is actually the prominent ends of the fracture under the skin
  • Shoulder range of motion is limited, although not as much as with fractures of the proximal humerus

Specific Findings: Proximal Humerus Fracture

  • A severely swollen shoulder
  • Very limited movement of the shoulder
  • Severe pain

Specific Findings: Scapular Fracture

  • Pain
  • Swelling
  • Severe bruising about the shoulder blade

Specific Findings: Shoulder Separation (Acromioclavicular Joint Separation)

  • Pain over the top of the shoulder
  • A prominence or bump about the top of the shoulder
  • The sensation of something sticking up on the shoulder

Specific Findings: Shoulder Dislocation (Glenohumeral Joint Dislocation)

  • A prominence about the front of the shoulder
  • Inability to move the arm
  • An arm rotated outward
  • The sensation of a « dead arm »

Diagnosis

Most fractures are diagnosed with X-rays of the area and by physical examination. Sometimes, additional imaging techniques, such as computed tomography, are necessary.

Source: Orthopaedic Trauma Association & AAOS