Shoulder Flashcards
Why are non-unions/mal-unions common in clavicles?
Weight and load from UE
Angle of glenoid
Lateral
Anterior
Superior
Glenoid Inclination
5 degrees of upward inclination –> lends passive stability
–Downward rotation of scapula reduces joint stability
Humerus Inclination
130-150 degrees toward body
Humerus Retroversion
20-30 degrees
- Diminishes IR
- This and humerus inclination facilitate articulation with the superiorly oriented glenoid
Sternoclavicular Joint
Sellar
Contains a meniscus, which absorbs shock and can become painful or stiff
Anterior and posterior sternoclavicular ligaments
How does clavicle rotate with arm elevation?
Posteriorly
AC Joint
Resists inferior translation of arm
Diarthrodial joint with meniscus (but meniscus doesn’t do much shock absorption)
Frequent site of DJD
AC Joint Ligaments
Acromioclavicular Ligament Coracoacromial Ligament Coracoclavicular Ligaments - Trapezoid - Conoid (more medial)
Muscles that reinforce the AC joint
Deltoid, Trapezius
Classification of AC Joint Injury
Rockwood Classification Type I-III: Same as tissue sprain classification Type IV: Surgery considered Type V: 100-300% increase in CC space Type VI: Less than normal CC space
Scapulothoracic Joint Functions
- Increase GH stability/ Congruency
- Increase arm elevation ROM (2:1 GH to ST ratio)
- Muscle attachments
- Optimizes length-tension relation of deltoid, e.g. - Absorb force from arm/ allow reaching
- Maintain subacromial space
Scaption
30-40 degrees anterior to the frontal plane
Plane of maximal GH elevation
Allows humeral head to remain centered on the glenoid
- Equal sharing of tension in GH ligaments
Functional position of arm
What nerve innervates Serratus Anterior?
Long thoracic
Anterior Scapular Stabilizers
Serratus Anterior Pec Minor (--> Downward tilt of scapula)
Rhomboid
Scapular retraction AND elevation
Upward Rotators of Scapula
Upper trap, lower trap, serratus
Downward Rotators of Scapula
Levator, rhomboids, pec minor
Phases of scapulohumeral rhythm
I (Setting), II (Critical) and III
Setting phase of scapulohumeral rhythm
Scapular Stabilization
- Clavicular Elevation
- AC Rotation
- GH Spin/Roll/Glide
3. 3GH: 1 ST
Critical phase of scapulohumeral rhythm
0-90 degrees
Clavicular Rhotation
GH Roll and Glide (Inferior translation)
0.7GH: 1 ST
Phase III of scapulohumeral rhythm
90 degrees and higher AC Rotation GH Roll and Glide Thoracic and lumbar spine **Where compensations begin (e.g. arching back) 3.5GH: 1 ST