The Shoulder = glenohumeral jt

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The Shoulder glenohumeral jt

• The glenohumeral joint is a ball-and-socket joint
  that allows for the arm to move in a circular
  rotation as well as movement of the arm towards
  and away from the body. The motion that the
  glenohumeral joint provides is flexion,
  extension, abduction and adduction.

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In Anatomical Position, the head of the humerus
is medial, slightly posterior and superior in the
glenoid fossa. While the glenoid cavity faces
laterally forward and superior.
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Acromioclavicular Joint (AC joint)

• a gliding joint within the shoulder. This joint
  is specific to primates and humans, allowing for
  the ability to raise the arm above the head. This
  joint functions as a pivot point, acting like a
  strut to help with movement of the scapula
  resulting in a greater degree of arm rotation.
  Also, the AV joint allows for the transmission of
  force from the upper arm to the rest of the
  skeleton

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The AV joint is formed between the clavicle and
the scapula. The acromion, a section of the
scapula, is the binding site for the clavicle.
These two bones fit together, but are not stable
on their own. Ligaments muscles are used to
stabilize the AV joint.
Two sets of muscles are important for the
stabilization of this joint in the proper joint
formation. help stabilize the clavicle and the
scapula 1) the trapezius The upper trapezius
muscle fibers connects the lower base of the
skull to the clavicle. The middle and lower
trapezius muscle fibers connect vertebrae in the
spine to the scapula. 2) the deltoid The
anterior deltoid connects the clavicle to the
humerus, while the posterior and lateral deltoid
fibers connect the scapula to the humerus.
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Trapezius

• Large superficial, flat triangular muscle of
  upper back. Originates on the occipital bone of
  skull, ligamentum nuchae and 7 cervical and all
  thoracic vertebrae and inserts onto the clavicle,
  acromion and spine of the scapula.
• Because the fibers run in different directions,
  it has a variety of actions. Different fibers
  control different actions
• The superior (upper) fibers elevate the scapula
  scapular elevation (shrugging up),
• the middle fibers retract it scapular adduction
  (drawing the shoulder blades together)
• The inferior (lower) fibers depress it
  depression (pulling the shoulder blades down)
• When the superior and inferior fibers act
  together
• they superiorly (upwardly) rotate the scapula.

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Deltoids

• forms the rounded contour of the human shoulder.

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Origin

• It arises in three distinct sets of fibers
• Anterior fibers from the anterior border and
  upper surface of the lateral third of the
  clavicle
• Middle fibers from the lateral margin and upper
  surface of the acromion.
• Posterior fibers from the lower lip of the
  posterior border of the spine of the scapula, as
  far back as the triangular surface at its medial
  end

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Insertion

• All the fibers converge, the middle passing
  vertically, the anterior obliquely backward and
  lateralward, the posterior obliquely forward and
  lateralward
• they unite in a thick tendon, which is inserted
  into the V-shaped deltoid tubercle on the middle
  of the lateral aspect of the shaft of the
  humerus.

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Action

• The anterior fibers shoulder abduction when the
  shoulder is externally rotated.
• The posterior fibers involved in transverse
  extension. The posterior deltoid is also the
  primary shoulder hyperextensor.
• The lateral fibers shoulder abduction when the
  shoulder is internally rotated, are involved in
  shoulder flexion when the shoulder is internally
  rotated, and are involved in shoulder transverse
  abduction (shoulder externally rotated) -- but
  are not utilized significantly during strict
  transverse extension (shoulder internally
  rotated).

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Rotator Cuff

• an anatomical term given to the group of muscles
  their tendons that act to stabilize the
  shoulder.

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Function of Rotator Cuff

• hold the head of the humerus in the small and
  shallow glenoid fossa of the scapula. During
  elevation of the arm, the rotator cuff compresses
  the glenohumeral joint in order to allow the
  large deltoid muscle to further elevate the arm.
  In other words, without the rotator cuff, the
  humeral head would ride up partially out of the
  glenoid fossa and the efficiency of the deltoid
  muscle would be much less.

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Muscles comprising rotator cuff

• Supraspinatus
• Infraspinatus
• Teres Minor
• Subscapularis
• A mnemonic to remember what muscles form the
  rotator cuff is SITS (supraspinatus,
  infraspinatus, teres minor, subscapularis)

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Rotator Cuff Injury

• injury to 1 or more of the 4 muscles in the
  shoulder. This shoulder injury may come on
  suddenly and be associated with a specific injury
  such as a fall (acute), or it may be something
  that gets progressively worse over time with
  activity that aggravates the muscle(s) (chronic).
  
• can range from an inflammation of the muscle
  without any permanent damage, such as tendinitis,
  to a complete or partial tear of the muscle that
  might require surgery to fix it.

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Chronic tear

• Found among people in occupations or sports
  requiring excessive overhead activity (examples
  painters, baseball pitchers)
• Variations in the shoulder structure causing
  narrowing under the outer edge of the collarbone

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Symptoms

• Occur more often in a person's dominant arm
• More commonly found among men older than 40 years
  
• Pain usually worse at night and interferes with
  sleep
• Worsening pain followed by gradual weakness
• Decrease in ability to move the arm, especially
  out to the side
• Able to use arm for most activities but unable to
  use the injured arm for activities that entail
  lifting the arm as high or higher than the
  shoulder to the front or side

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Acute tear

• Sudden powerful raising of the arm against
  resistance, often in an attempt to cushion a fall
  (examples heavy lifting, a fall on the shoulder)
  
• Injury usually associated with a significant
  amount of force if person is younger than 30
  years

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Symptoms

• Sudden tearing sensation followed by severe pain
  shooting through the arm
• Motion limited by pain and muscle spasm
• Acute pain from bleeding and muscle spasm (often
  goes away in a few days)
• Point tenderness over the site of rupture
• With large tears, inability to raise the arm out
  to the side, although this can be done with help

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Tendinitis

• Degeneration (wearing out) of the muscles with
  age
• Repetitive trauma to the muscle by everyday
  movement of the shoulder

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Symptoms

• More common in women aged 35-50 years
• Deep ache in the shoulder also felt on the
  outside upper arm
• Point tenderness
• Pain comes on gradually and becomes worse with
  lifting the arm to the side or turning it inward
  
• May lead to a chronic tear

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When to call the doctor

• If shoulder pain lasts more than 2 days
• If shoulder problems (pain) do not allow you to
  work
• If you are unable to reach overhead to get an
  item in a cabinet above shoulder level, for
  example
• If you are unable to play a certain sport such as
  baseball or engage in an activity such as
  swimming

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When to go to the hospital

• For any acute injury in which you are unable to
  move the injured shoulder as well as the
  uninjured shoulder, seek emergency medical care.

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