Shoulder joint consists of Acromio-Clavicular Joint and Gleno-Humeral Joint. Shoulder joint dislocation is often seen with Gleno-Humeral joint. Shoulder joint separation is either partial or complete. Partial separation is known as subluxation and complete separation is known as dislocation. Dislocation is a breakage of link between humerus and glenoid socket of scapula. Shoulder joint dislocation is more common than any other joint dislocation because shoulder joint has a wide range of movement and is used extensively during daily activities.
Close reduction can result in complete recovery in 6 to 8 weeks and open or surgical reduction may take 12 to 16 week for complete recovery. Twenty five percent of shoulder joint dislocation is associated with fracture of one of the shoulder joint bone.
Causes Of Shoulder Joint Dislocation
A. Sport Injury
Most of the shoulder joint dislocation during sporting activities are caused when athlete tries to prevent fall with outstretch arm.
- Rock climbing
B. Work Injury or Accident
- Shoulder joint injury results following fall on hard surface from height.
- Abnormal rotation of the shoulder joint while using heavy equipment may result in shoulder joint dislocation.
- Accidental forceful pull or push of upper arm while using chain or rope at work may result in shoulder joint dislocation.
C. Automobile Accident
- Shoulder joint dislocation results when pedestrian tries to prevent impact with outstretched arm.
- Shoulder joint dislocation with fracture may occur during high velocity impact of shoulder joint against dashboard of the car or side door.
- Abnormal rotation of the shoulder joint during automobile accident may result in anterior or posterior shoulder joint dislocation
D. Domestic Injury
- Domestic injury resulting in shoulder joint dislocation mostly involves elderly patients.
- Fall on slippery surface or off the staircase often causes shoulder joint dislocation.
Types Of Shoulder Joint Dislocation
- Anterior (Front) Dislocation Of The Shoulder Joint
- Posterior (Backward) Dislocation Of The Shoulder Joint
- Inferior (downward to armpit) Dislocation Of The Shoulder Joint.
Anterior Dislocation Of The Shoulder Joint
- Anterior dislocation is a most common (95%) shoulder joint dislocation.
- Injury is caused by direct forceful impact of shoulder joint while arm is outstretched.
Types of Anterior Dislocation Of The Shoulder Joint-
- Subcoracoid shoulder joint dislocation- Head of humerus lies anterior to glenoid cavity and inferior to coracoid process.
- Subglenoid shoulder joint dislocation- Head of humerus lies anterior (front) and inferior (lower) to glenoid cavity.
- Subclavicular shoulder joint dislocation-
- Head of the humerus is in front and medial to glenoid cavity.
- Dislocated head of humerus is shifted medially or inward resulting in position underneath the clavicle.
Arm Position Following Anterior Dislocation Of The Shoulder Joint-
- Arm is held in abduction 10 to 20 degree away from side of the body and externally rotated.
- Deltoid and acromion prominence is shifted posterior and laterally.
- Head of humerus is felt anterior to joint.
Posterior Dislocation Of The Shoulder Joint
- Posterior dislocations are rare
- Injury is often seen following automobile accident or following fall during seizures.
- Diagnosis of posterior dislocation is often delayed despite patient complaining of shoulder joint pain.
Arm Position in Posterior Dislocation Of The Shoulder Joint-
- Following posterior dislocation, arm is adducted (lies against side of the body) and internally rotated at shoulder joint.
- Arm is often flexed at elbow joint.
Inferior Dislocation of The Shoulder
Less than 1% of the shoulder joint dislocation falls in this group.
Arm Position in Inferior dislocation of Shoulder
- Arm is held upward and behind the head until dislocation is corrected.
- Arm position is known as "Luxatio Erecta".
Complications Of Shoulder Joint Dislocation
- Laceration or tear of axillary artery causes minor or major bleeding.
- Axillary artery injury is mostly seen following anterior and inferior dislocation.
- Injury or laceration of axillary brachial plexus causes nerve injury of the upper extremity.
- Sensory nerve fiber damage causes tingling and numbness
- Motor nerve (nerve to muscles) injury causes weakness in group of muscles supplied by the injured nerve.
- Nerve Injury is mostly seen with inferior dislocation.
- Inferior dislocation causes tear or laceration of tendons located around the shoulder joint.
- Rotator cuff injury is also common with shoulder joint dislocation.
- Ligamental injury is common following inferior and anterior dislocation.
- Inferior dislocation causes tear or laceration of posterior shoulder joint ligaments
- Rotator cuff injuries are commonly seen in older patients who dislocate their shoulder. The diagnosis may be difficult to make initially and often is made in follow-up visits with the health-care provider.
Joint Capsule and Labrum Injury-
- Shoulder joint dislocation may be associated with significant injury of joint capsule and labrum.
- Glenoid Labrum partial tear or laceration
- Capsular ligament partial tear or laceration
- Shoulder joint capsule injury
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