Shoulder Complex Flashcards
4 Joints that make up shoulder complex
GH, SC, AC, ST Joints
True Joints
GH, AC, SC Joints
Functional Joint (not a true “joint”)
ST “joint”
Dynamic Stabilization
-active forces or dynamic muscular control
What type of joint is the Sternoclavicular (SC) joint?
-Synovial with 3 DOF;
-Saddle-shaped;
-Reciprocal convex-concave surfaces
SC fibrocartilage disc
-Improves stability
-Increase congruence between the articulating surfaces and dissipates joint loads
A/P SC Ligaments
-Reinforces capsule
-Restraint A/P translations
SC-Costoclavicular Ligament (A/P laminae)
-Limit lateral elevation and medial translation of clavicle
-Absorb and transmits superior forces
SC-Interclavicular Ligament
-Limits excessive depression of lateral clavicle
-Limits superior gliding of medial clavicle
Interclavicular ligament protect?
-Brachial plexus and subclavian artery
Joint connecting UE to axial skeleton?
-SC Joint
Coracoclavicular Ligament Critical Function
-Couple posterior rotation of the clavicle + upward rotation of scapula
Resting position of scapula
-Approx. 5cm from midline
-Betw. ribs 2-7
-Tilted ant. 10-15 degrees from vertical
-Up. rotated 10-15 degrees from vertical
-IR 34-45 degrees from coronal plane
SC Open-packed position
-arm resting by the side
SC Close-packed position
-Max UE elevation
SC Osteokinematics
Elevation/Depression
Protraction/Retraction
A/P Rotation
Subacromial Space structures
-Rotator cuff tendons
-LH of biceps tendon
-Subacromial bursae
Coracoacromial arch (Osteoligamentous vault over humeral head) Consists of…
coracoid process
acromion
coracoacromial ligament
AC joint
ST “joint” Functions
-Orient contact of scapula with thorax, glenoid fossa with humeral head
-Provide stable base for controlled motions between humeral head and glenoid fossa
-Add range to elevation of arm
Muscles Synergistically Stabilizing GH joint
-Rotator cuff muscles + Deltoid
Full elevation of arm, ST “joint” needs to
-Up. rotate, post. tilt, and ER to open subacromial space
The upper trap, serratus anterior, and lower trap fire _______________ to produce scapular upward rotation while the rhomboids fire ______________ to stabilize this motion.
-concentrically; eccentrically
What type of joint is the Acromioclavicular (AC) Joint?
-Incongruent Plane synovial w/ 3 DOF
Primary function of the AC Joint
-allow scapula to rotate in 3D; increasing UE motion, positions glenoid beneath humeral head, max scapula contact with thorax
AC Osteokinematics
IR/ER
A/P Tilting
Up/Down Rotation
AC Open packed position
Arm resting by side
AC Close-Packed position
90 degrees ABd.
AC superior and inferior ligaments
-assist capsule in apposing the articular surfaces
-provide horizontal stability and prevent superior dislocation of the AC joint
Superior AC ligament
-Stronger than inferior;
restrain movement caused by anterior forces to lateral clavicle
AC-Coracoclavicular ligament
-Provide joint’s superior, inferior and rotational stability
AC-Coraco. Conoid Ligament
-Triangular/vertical oriented
-restrain inferior translation of acromion related to lateral clavicle
AC-Coraco. Trapezoid ligament
-Quadrilateral /horizontal oriented;
-restrain posterior translations of lateral clavicle relative to acromion
Conoid and Trapezoid ligaments together
-limit up. rotation of scapula at AC joint
What type joint is the Scapulothoracic (ST) Joint?
-Functional joint, not a true joint
ST Osteokinematics
Elevation/Depression
Pro/Retraction
Up/Down Rotation
IR/ER
A/P tilting
What type joint is Glenohumeral (GH) Joint?
Synovial Ball-and-Socket with 3 DOF
GH Osteokinematics
Flexion/Extension
Abduction/Adduction
IR/ER
Open-packed Position of GH joint
-55 degrees ABd, 30 degreed Horiz. ADd, slight ER
Close-packed position of GH Joint
Full ABd, full ER
GH proximal articulation
Glenoid fossa rests lateral, inferior and anterior relative to head of humerus
GH distal articulation
Humeral head rests medial, superior and posterior relative to shaft of humerus
GH Distal articulation Angle of inclination and torsion
Inclination: normal 130-150 degrees
Torsion: normal 30 degrees posteriorly (retroversion)
GH - Glenoid labrum
-enhances total available articular surface;
-resists humeral head translations
-protect bony edges
-min joint friction
-dissipate joint contact forces
When the arm is at rest at the side, the superior glenohumeral (GH) capsule is ______ whereas the inferior capsule is ______.
Taut;slack
GH Superior Ligament
-Ant/Post stability
-limit ant. / inferior translations of the humeral head when 0 deg ABD
GH Middle ligament
-Ant. stability
-limit ant. humeral translation when 60 deg ABD
GH Inferior ligament (IGHLC)
-Joint stability when ABD beyond 45 deg or combined ABD and Rotation
GH- Coracohumeral ligament
-Limits inf. translation of humeral head in dependent arm position
-resists humeral ER with arm ADD
-2ndry stabilizer for humerus when rotator cuff muscles impaired
Scapulohumeral Rhythm - Shoulder Elevation
-ABD. or Flexion
-2:1 ratio (120 GH : 60 ST)
Humeral contributions with shld. elevation that clear greater tuberosity from CC arch
lateral rotation (ER)
Scapular contributions with shld. elevation that opens SA space
-Posterior tilt, ER @ end-range elevation
-early flexion: protraction and IR
Muscles stabilizing ST joint
Upward rotation:
-upper traps
-serratus anterior
-lower traps
With elevation of the lateral clavicle, at the sternoclavicular joint the medial clavicle rolls __________ and glides ______.
(superiorly; inferiorly)
With depression of the lateral clavicle, at the SC joint the medial clavicle rolls _______ and glides _______.
(inferiorly, superiorly)
With protraction of the lateral clavicle, at the SC joint the medial clavicle rolls _______and glides _________.
(anteriorly; anteriorly)
With retraction of the lateral clavicle, at the SC joint the medial clavicle rolls _____ and glides _________.
(posteriorly; posteriorly)
At the SC joint, the clavicle rotates primarily posteriorly from neutral, bringing the inferior surface of the clavicle to face _______.
anteriorly
From a posteriorly rotated position, at the SC joint the clavicle can then rotate ________ to return to neutral.
anteriorly
At the AC joint with IR, the medial border moves _____, glenoid fossa moves _____ and _____.
(away; anteriorly; in)
At the AC joint with ER, the medial border moves _____, glenoid fossa moves _____ and _____.
(towards; posteriorly; out)
At the AC joint with anterior tilt, the acromion moves _______, inferior angle moves _______ and ______from ribcage.
(anteriorly; posteriorly; away)
At the AC joint with posterior tilt, the acromion moves _______, inferior angle moves _______ and _____ the ribcage
(posteriorly; anteriorly; towards)
At the AC joint with upward rotation, inferior angle will move ______, while the glenoid fossa moves ______.
(laterally; superiorly)
At the AC joint with downward rotation, inferior angle will move ______, while the glenoid fossa moves ______.
(medially; inferiorly)
Flexion at the GH joint involves ______ roll and an ________glide of the head of the humerus.
(anterior; posterior)
Extension at the GH joint involves ______ roll and an ________glide of the head of the humerus.
(posterior; anterior)
Abduction at the GH joint involves ______ roll and an ________glide of the head of the humerus.
(superior; inferior)
Adduction at the GH joint involves ______ roll and an ________glide of the head of the humerus.
(inferior; superior)
IR at the GH joint involves ______ roll and an ________glide of the head of the humerus.
(anterior; posterior)
