Biomechanics Lecture 04

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Common injuries of the Shoulder

COMMON INJURIES OF THE SHOULDER

—  The shoulder is susceptible to:

—  Traumatic Injuries

—  Overuse Injuries, (including 8–13% of all sport-related injuries)

—  Dislocation  

—  Glenohumeral

—  Acromioclavicular

—  Rotator Cuff Injuries -Shoulder impingement syndrome

—  Rotational Injuries

—  Subscapular Neuropathy

                                                                DIFFERENCE

Dislocation??

“Complete separation of articular surfaces with soft tissue                                           damage”

Subluxation??

“Incomplete separation of articular surfaces with or without soft tissue damage”


GLENO HUMERAL JOINT DISLOCATION

Glenohumeral Joint

—  most commonly dislocated joint in body

Reason

—  loose structure of  glenohumeral joint enables extreme mobility but provides little stability

Direction of Dislocation:

—   Anterior

—  Posterior

—  Inferior

DISLOCATION

Superior direction

—  Strong coracohumeral ligament prevents displacement in the superior direction.

Mechanism of dislocation:

—  Glenohumeral dislocations occur when humerus is abducted and externally rotated.

—  Antero-inferior dislocations more common than those in other directions.

 Factors that predisposes the joint to dislocations include:

—  Inadequate size of  glenoid fossa

—  Anterior tilt of the glenoid fossa

—  Inadequate retroversion of  humeral head and deficits in  rotator cuff muscles

—  Once the joint has been dislocated, the stretching of the surrounding collagenous tissues beyond their elastic limits commonly predisposes it to subsequent dislocations.

—  Glenohumeral capsular laxity due to genetic factors; Individuals with this condition should strengthen their shoulder muscles before athletic participation

     DISLOCATION

—  Dislocated shoulders tend to occur more often in males than in females. This is probably because of association with contact sports.

—  In men, the peak age is 20-30 years and in women it is 61-80 years (due to susceptibility to falls).

—  Repeated episodes of dislocation should raise the possibility of hypermobility or  Ehlers-Danlossyndrome being present.

—  Ehlers-Danlos syndrome (EDS) is a rare inherited condition with disruption of the integrity of structural proteins in skin, ligaments, cartilage and blood vessels, leading to fragility of connective tissues.

MECHANISM OF INJURY

v  Anterior dislocation – Fall with abduction and posteriorly directed force on arm.

v  Fall on out stretched hand – common in elderly

CAUSES OF DISLOCATIONS

—  Dislocation may results from large external force. During accident , during contact sports such as wrestling and football.

—  laxity of glenohumeral joint capsule due

to genetic factors.

ACROMIOCLAVICULAR JOINT DISLOCATION

Dislocations or separations of acromioclavicular joint

Sports: common among wrestlers and football players.

Mechanism:

When a rigidly outstretched arm sustains force of a full-body fall, either acromioclavicular separation or fracture of clavicle is likely to result.

ROTATIONAL INJURIES

Structures involved forceful rotation at shoulder:

—  Tears of  labrum

—  Rotator cuff muscles

—  Biceps brachi tendon

Sports including forceful rotational movements

—  Throwing, serving in tennis, and spiking in volleyball

OTHER PATHOLOGIES

—  Calcification of soft tissues of joint.

—  Degenerative changes in articular surfaces.

Bursitis:

“Inflammation of one or more bursae, is another overuse syndrome, generally caused by friction within bursa

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