stephen
stephen

Normal Anatomy of the Shoulder Joint

The shoulder is the most flexible joint in the body making it the most susceptible to instability and injury. It is a 'ball-and-socket' joint. A ‘ball' at the top of the upper arm bone, humerus, fits neatly into a 'socket’, called the glenoid, which is part of the shoulder blade, scapula.

The shoulder joint is made up several bones and soft tissues. It has three bones, the collarbone (clavicle), scapula, and humerus.

Humerus provides attachment to muscles of the upper arm. Scapula is the bone that connects the upper arm bone with the collarbone. It is a flat bone and roughly triangular in shape and provides attachment to the muscles of back and neck.

The clavicle is an S-shaped short bone that connects the shoulder girdle to the body (trunk). It supports the shoulder in a functional position with the axial skeleton so that the arm has maximum range of movement. It also protects major underlying nerves and blood vessels as they pass from the neck to the axilla.

The coracoid process is the extension of the scapula around the shoulder joint at the front portion of the scapula. The acromial process is the extension of scapula around the shoulder joint at the back that forms a roof, acromion.

Glenoid is the smooth shallow depression at the end of scapula that forms the socket of shoulder joint.

The soft tissues of shoulder joint include:

Rotator cuff – A group of 4 tendons make rotator cuff and it holds the head of the humerus in the socket.

Biceps tendon – The biceps tendon is a long cord-like structure which attaches the biceps muscle to the shoulder and helps to stabilize the joint.

Caraco Clavicular Ligament – This ligament connects the clavicle with the corocoid process of the scapula.

Acromio Clavicular Ligament – It connects the clavicle with the acromion process.

Glenoid labrum – The Glenoid labrum is a ring of fibro cartilage surrounding the cavity of the scapula for stabilization of the shoulder joint.

Articular cartilage or the capsule – It is a capsule that surrounds the shoulder joint and helps to keep the ball and socket normally aligned.


Shoulder Instability

Shoulder instability is a chronic condition that causes frequent dislocations of the shoulder joint.

Causes

A dislocation occurs when the end of the humerus (the ball portion) partially or completely dislocates from the glenoid (the socket portion) of the shoulder. A partial dislocation is referred to as a subluxation whereas a complete separation is referred to as a dislocation.

Risk Factors

The risk factors that increase the chances of developing shoulder instability include:

  • Injury or trauma to the shoulder
  • Falling on an outstretched hand
  • Repetitive overhead sports such as baseball, swimming, volleyball, or weightlifting
  • Loose shoulder ligaments or an enlarged capsule

Symptoms

The common symptoms of shoulder instability include pain with certain movements of the shoulder; popping or grinding sound may be heard or felt, swelling and bruising of the shoulder may be seen immediately following subluxation or dislocation. Visible deformity and loss of function of the shoulder occurs after subluxation or sensation changes such as numbness or even partial paralysis can occur below the dislocation as a result of pressure on nerves and blood vessels.

Conservative Treatment

The goal of conservative treatment for shoulder instability is to restore stability, strength, and full range of motion. Conservative treatment measures may include the following:

  • Closed Reduction: Following a dislocation, your surgeon can often manipulate the shoulder joint, usually under anesthesia, realigning it into proper position. Surgery may be necessary to restore normal function depending on your situation
  • Medications: Over the counter pain medications and NSAID’s can help reduce the pain and swelling. Steroidal injections may also be administered to decrease swelling
  • Rest: Rest the injured shoulder and avoid activities that require overhead motion. A sling may be worn for 2 weeks to facilitate healing
  • Ice: Ice packs should be applied to the affected area for 20 minutes every hour

Surgery

When the conservative treatment options fail to relieve shoulder instability, your surgeon may recommend shoulder stabilization surgery. Shoulder stabilization surgery is done to improve stability and function to the shoulder joint and prevent recurrent dislocations. It can be performed arthroscopically, depending on your particular situation, with much smaller incisions. Arthroscopy is a surgical procedure in which an arthroscope, a small flexible tube with a light and video camera at the end, is inserted into a joint to evaluate and treat of the condition. The benefits of arthroscopy compared to the alternative, open shoulder surgery are smaller incisions, minimal soft tissue trauma, less pain leading to faster recovery.