Shoulder Complex Overview/Pathology/Stabilizers Flashcards
What are the joints that make up the shoulder complex?
sternoclavicular
acromioclavicular
glenohumeral
scapulothoracic
What is the one joint in the shoulder girdle that is not a true synovial joint?
scapulothoracic
SC joint
articulation between : Sternal end of clavicle, clavicular notch of sternum, superior surface of first costal cartilage; intra-articular fibrocartilaginous disc
type: saddle joint
motion: gliding and rotation motion
the articular disc divides the joint in two; increases the surface area of the joint, and increases shock absorption
SC joint convex and concave joint surfaces:
clavicle:
superior-inferior: convex
anterior posterior- concave
manubrium
superior-inferior: concave
anterior-posterior- convex
protraction:
-anterior roll and glide of the concave clavicle on the manubrium
retraction: posterior roll and glide of the clavicle
elevation: superior roll and inferior glide of the convex clavicle on concave manubrium
depression: inferior roll and superior glide of convex clavicle on concave manubirum
ligaments of the SC joint:
SC ligament - anterior and posterior; dense thickening of the capsule
costoclavicular ligament - taught with elevation and retraction
interclavicular ligament integrates into the fascia of the neck
What muscle stabilizes the SC joint?
subclavius muscle
SC joint dislocation:
-can happen ant or posterior
-very rare
-direct trauma or blow to the clavicle or with fall on an outstretched arm
-MUCH more common to fracture the clavicle
-anterior dislocation usually does well non-surgically
-posterior dislocation–> more risk to structures behind sternum
-surgery (autograft or allograft) may be indicated- semitendinosus tendon
AC joint characteristics
type: plane/gliding joint
articulation: Acromion of scapula, acromial end of clavicle
motions: gliding in all directions
ligaments:
-AC lig
-coracoclavicular ligament:
—trapezoid (more lateral)
—conoid (more medial, deeper)
with abduction-adduction of shoulder girdle- rotation of acromion on clavicle
AC joint sprain (separated shoulder)
-progressive disruption of ligaments
—AC lig
—coracoclavicular ligaments
-graded by degree of displacement
-grades 1-3 can be managed non-surgically
GRADE 1 - not torn AC lig just sprain, no medial lig damage
GRADE 2- AC torn, stretched medial ligs
GRADE 3- complete luxation of the joint due to tearing of all the ligaments
GRADE 4- clavicle is severely displaced posteriorly
GRADE 5 - clavicle is severely displaced superiorly
GRADE 6- clavicle is displaced under the coracoid process
Scapulothoracic joint characteristics
“pseudo” joint
-muscular joint between the scapula and the thoracic cage
-required for full ROM at the GH joint
-no direct ligament attachment
MOVEMENTS:
-abduction (protraction)
-adduction (retraction)
-upward rotations, downward rotation , IR, ER, anterior and posterior tilt
-depression and elevation
rotations are fully reliant on muscular control
Scapular positioning/scapulohumeral rhythm:
The glenoid moves like a seal’s nose to remain in the right spot to control the ball (head)– > congruency is very important
SCAPULOHUMERAL RHYTHM (movement coordination) function:
-allows for greater overall shoulder ROM
-maintains optimal contact between the humeral head and the glenoid fossa
-Assists with maintaining an optimal length-tension relationship of the glenohumeral muscles.
Characteristics SH Rhythm
-integrated movements of GH, ST, AC, AND SC JOINTS
-sequential fashion –> full motion of shoulder complex
ARM ELEVATION EVIDENCE:
-more elevation on non-dom side (more upward rotation)
-between 1:3 AND 1:5 scapula to humerus motion –> depends on plane of humeral motion, side of dominance, and age of patient
-movement patterns depend on if you’re moving unilaterally or bilaterally
How is the thoracic spine involved in scapulohumeral rhythm?
Bilateral shoulder motion: 10-30 degrees of thoracic extension
(primarily lower) with full shoulder elevation
- Unilateral shoulder motion:10-30 degrees of thoracic rotation
and/or side-bending - Clinical relevance: Assess thoracic motion in patients with shoulder symptoms!
Glenohumeral joint characteristics
shoulder joint
synovial
multiaxial
ball and socket
largest ROM and movement in the body
-shallow joint
-extensive joint capsule
-limited ligamentous support
Static stabilizers of the GH joint:
LABRUM
-the fossa is 1/4 the size of the humeral head
-fossa is pear-shaped–> reducing congruency
-the labrum helps increase concavity of the glenoid fossa as well as the articular cartilage (but to a lesser extent)
-fossa is smaller on the superior aspect than inferior
-the labrum deepens the socket 50-75%
-Glenoid faces lateral, anterior, and superior
–> angle of inclination changes with the position of the scapula (scapulohumeral rhythm)
JOINT CAPSULE
-tissue: anterior and
posterior continues laterally on
the humerus into the neck of the humerus
-anterior and inferior capsule much thicker than posterior
LIGAMENT COMPLEX
-SGHL
-MGHL
-IGHL
Dynamic stabilizers of the GH joint:
muscles surrounding the joint
ROTATOR CUFF - pulls head of humerus into glenoid fossa
-supraspinatus
-infraspinatus
-subscapularis
-teres minor
** Long head of the biceps (not technically)
-tendons intimate with capsule
-tendinitis is rarely isolated to one tendon –> muscles and tendons DO NOT function in isolation
DELTOID
-large stabilizing component, regardless of humeral position
-** primary function to swing humerus
Static stabilizers of the GH joint:
LABRUM
-the fossa is 1/4 the size of the humeral head
-fossa is pear-shaped–> reducing congruency
-the labrum helps increase concavity of the labrum as well as the articular cartilage (but to a lesser extent)
-fossa is smaller on the superior aspect than inferior
-the labrum deepens the socket 50-75%
JOINT CAPSULE
-tissue: anterior and
posterior continues laterally on
the humerus into the neck of the humerus
-anterior and inferior capsule much thicker than posterior
LIGAMENTS
-anterior GH ligaments
-inferior- pliable redundant ligamentous complex
RESTRAINTS TO SHOULDER ER
0 ABDUCTION
-subscapularis
-SGHL
45 ABDUCTION
-SGHL
-MGHL
90 ABDUCTION
-anterior band of IGHLC
RESTRAINTS TO SHOULDER IR
0 ABDUCITON
-posterior band of IGHLC
45 ABDUCITON
-anterior and posterior band IGHLC
-teres minor
-infraspinatus
90 ABDUCTION
-anterior and posterior band IGHLC
RESTRAINTS TO INFERIOR TRANSLATION
0 ABDUCTION
-SGHL
-coracohumeral lig
90 ABDUCTION
-IGHLC (superior elements are lax)
LOOSE AND CLOSED PACK POSITION GH JOINT
OPEN/LOOSE PACK
-55 deg abduction, 30 deg horizontal adduction
CLOSE PACK
-end range abduction and ER
Research study about capsule tightness and how that affects motion of the GH joint:
The humeral head will glide away from the tightest portion of the capsule
- generally, the humeral head will stay in the center of the glenoid fossa–> although the head will glide away from the tightest portion–> it’s important to work on capsular mobility
Force coupling at GH joint
Need forces of the rotator cuff muscles to center the glenoid and oppose the shearing forces of the deltoid as the deltoid moves to swing the bone
-without rotator cuff the deltoid would pull the humeral head superiorly at 0 degrees of abduction
Possible causes of subacrominal impingement
RTC tendon and/or LHB may get repeatedly compressed, along with the bursa
CAUSES:
-RTC dysfunction
-scapular positioning
-shape of acromion
-GH joint mobility deficit or hypermobility
