1. The document discusses the embryology, anatomy, and movements of the shoulder joint. It describes the development of the limb buds and rotation of the upper limb. 2. Key anatomical structures around the shoulder are described, including muscles, ligaments, vascular structures, and bones. The shoulder joint is a multiaxial ball and socket synovial joint between the humerus and scapula. 3. Flexion, extension, abduction, medial/lateral rotation of the shoulder are explained. The roles of various muscles in producing these movements are provided.

1. Embryology
• Paraxial mesoderm
• Lateral Plate mesoderm—Shoulder Girdle
• Neural Crest

2. • Limb buds visible at the end of 4th
week
• In 7th
week upper limb rotates laterally 90
deg
• Pre axial border in embryo becomes
lateral border in adults

3. • Cartilaginous condensations
• Chondrogenesis is arrested
• Joint inter-zone induced
• Cells increase in no. and density
• Joint cavity formed by cell death
• Surrounding cells differentiate to form joint
capsule

4. • Inductive Signal for Joint Positioning: WNT 14
• Limb positioning : HOX genes
• AP axis patterning: ZPA (zone of polarizing
activity)
ZPA produces retinoic acid which expresses
sonic hedgehog.

6. SHOULDER JOINT
• Multiaxial, ball & socket, synovial joint
• 4:1 disproportion
• Deepened by labrum
Capsular attachments:
1. scapula-beyond supraglenoid tubercle
2. Anatomical neck of humerus EXCEPT
inferiorly where it is on surgical neck

7. • Bridges gap between GT and LT as
Transverse Humeral Ligament
• Gap in ant. Capsule for communication
with subscapularis bursa
• Thick, tough BUT lax
• Long tendon of biceps - Intracapsular

8. SYNOVIAL MEMBRANE:
Attached to glenoid labrum and lines
capsule at:
1. Articular margin humeral head
2. Invests long head of biceps
3. Covers bare area – surgical neck
4. Reflected along flr of IT sulcus; lines THL

9. HILTON’S LAW: “Nerves crossing a joint
give off branches and innervate it.”
1. Axillary nerve
2. Suprascapular nerve
3. Musculocutaneous nerve
4. Subscapular nerve

10. Muscles around shoulder
• Subscapularis
• Supraspinatous
• Infraspinatous
• Teres Minor
• Teres Major
• Deltoid

11. Ligaments around shoulder
• Glenohumeral ligament
3 thick bands btw glenoid labrum and humerus
Reinforce anterior capsule
Visible only from within the joint cavity
Function depends on:
1. Collagenous integrity
2. Attachment site
3. Position of the arm
Inf. GHL is main stabiliser of abducted arm
Ant. And posterior bands. (Hammock like)

12. • Coracohumeral ligament
Coracoid process to front of GT
Blends with the capsule
• Coracoacromial ligament
Flat triangular band
Medial border of acromion ant. to AC jt. to
lateral border of coracoid
Lies above humeral head
Separated from rotator cuff by subacromial
bursa

14. Movements
• Flexion: Cl. Head pect. Major
Ant. Deltoid
Coracobrachialis
Short head biceps
• Extension: Lat. Dorsi
Teres major
Post. Deltoid
Sternocostal part of pectoralis major can extend a
fully flexed arm and flex a fully extended arm

15. • Abduction: supraspinatous
Deltoid
>120 deg Trapezius/Serratus anterior
• Medial Rotation: Subscapularis
Teres Major
• Lateral Rotation: Teres Minor
Infraspinatous
• Circumduction

16. AXILLARY ARTERY
• Continuation of 3rd
part of subclavian
• Starts @ outer border 1st
rib
• Ends @ lower border teres major
• Lies on 1st
digitation of serratus anterior
• Enclosed in sheath with Br. plexus cords
• Divided by pectoralis minor into parts
Above, behind and below

18. Dorsal
Scapular artery
Suprascapular A.
Subscapular A.
Circumflex
Scapular A

19. Scapula vascularity
• Vessels in muscle taking origin from it
• Vessels communicate with bony vessels
• Circulation in scapula is metaphyseal
• Periosteal vessels larger than usual
• Communicate freely with medullary
vessels
• Nutrient artery enters through lateral
supra/infrascapular fossa

20. Sternoclavicular Joint
• Clavicle protrudes superiorly and
posteriorly
• Ant. And post sternoclavicular ligs.
• Disk divides jt
• Disk attached to 1st
rib below and to sup.
Surface of clavicle through interclavicular
lig
• Elevn - depression in jt bet clavicle & disk
• AP and rotn between disk & sternum

21. • 30-35 deg elevation
• 35deg AP movt.
• 44-50 deg rotation
• Elevation occurs at 30- 90 deg arm
elevation
• Rotation occurs after 70-80 deg elevation

22. • Blood supply
Clavicular branch thoracoacromial A
Internal mammery A
Suprascapular A.
• Nerve supply:
N. To subclavius
Medial supraclavicular N.
• Relation:
Ant: SCM
Post: Sternohyoid, Sternothyroid
Great vessels and trachea

23. AC Joint
• Capsule has diarthrodial joint incompletely divided by
perforated disk
• Inferiorly capsule is thin
• 20 deg rotation btw acromion and clavicle
in 1st
20 deg and last 40 deg of elevation
• Blood supply
Acromial A. br. Of deltoid A of thoracoacromial A
Suprascapular A
• Nerve Supply
Lateral pectoral
Axillary
Suprascapular

24. • AP stability: Acromioclavicular lig
• Sup & Inf translation: Conoid and
trapezoid parts of Coracoclavicular lig
• Types of acromion (Bigliani)
1. Flat undersurface
2. Curved
3. Hooked (Max. chance of impingement)

25. Humerus
• Radius of curvature of head 2.25 cm
• Humeral retroversion 25 deg
• Intertubercular groove lies 1cm lateral to
midline of humerus
• Axis of humeral head passes 9mm post to
bicipital groove
• Head shaft angle 135 deg
• Head size correlates best with height

26. • Because of its distance from centre of
rotation, GT lengthens lever arm of
supraspinatus as elevation increases
beyond 30 deg
• It also acts as a pulley by increasing lever
arm of deltoid below 60 deg.