anatomy,biomechanics

1. Dr. HARSHA NANDINI TALASILA
M.S. ORTHO
ANATOMY AND
BIOMECHANICS OF
THE SHOULDER
JOINT

2. • Shoulder joint complex is formed by articular surfaces of
scapula, clavicle and proximal humerus.
It includes 4 joints-
1. Glenohumeral
2. Acromioclavicular
3. Sternoclavicular
4. Scapulothoracic

3. Glenohumeral Joint
• Glenohumeral joint is a ball and socket type of
synovial joint .
• The joint is formed by the articulation of the
scapula and the head of the humerus.
• Structurally it is a weak joint because the
glenoid cavity is too small and shallow to hold
the head of the humerus in place.

4. • Stability of the joint is maintained by
1. Coracoacromial arch or secondary socket for
the head of the humerus
2. Musculotendinous cuff of the shoulder.
3. Glenoid labrum
4. Muscles attaching the proximal humerus to
pelvic girdle like long head of the biceps
brachii and long head of the triceps brachii

5. Coracoacromial Arch(Supra
humeral arch)
• Formed by acromian,coracoid,coracohumeral
ligament,inferior surface of acromioclavicular joint
• Space b/w arch and head is subacromial space
• contents: subacromial bursae
rotator cuff tendons
tendon of biceps
• Prevents superior dislocation and protects contents
of subacromial space

7. Articular surfaces
Glenoid fossa-pear shaped
shallow
directed laterally and upwards
deepened by glenoid labrum
Head of humerus-globular structure
directed medially,superiorly and
posteriorly
4times the size of glenoid cavity

8. LIGAMENTS
1. Capsular ligament
2. Coracohumeral ligament
3. Transverse humeral ligament
4. The glenoid labrum

9. CAPSULAR LIGAMENT
• The capsule is very loose and permits free
movements
• The capsule is lined by the synovial membrane.
• The extension of this membrane forms a tubular
sheath for the tendon of the long head of the biceps
brachii.

10. ATTACHMENTS OF THE CAPSULE
• Medially-scapula beyond supraglenoid
tubercle and the margins of the labrum
• Laterally-anatomical neck
• Inferiorly-surgical neck
• Superiorly –deficient for the passage of the
tendon of long head of biceps brachii
• Anteriorly-superior,middle and inferior
glenohumeral ligaments

12. Coracohumeral ligaments
• Extends from the root of coracoid process to
neck of humerus opposite to greater
tuberosity
• It gives strength to the capsule

13. TRANSVERSE HUMERAL LIGAMENT
• Bridges of bicipital groove of humerus
• Long head of biceps passes deep to this
ligament

15. Glenoid labrum
-Fibrocartilage rim attaching margin of glenoid.
-Deepens cavity for articulation
-Protects edges of bone
-Reduction of joint friction and dissipation of joint
contact forces
-Continuous above with long head of biceps

17. Bursae
• Subacromial bursa or Subdeltoid bursa
• Subscapularis bursa
• Infraspinatus bursa

18. Relations of shoulder joint
Superiorly
•Coracoacromial arch
•Sub acromial bursae
•Supraspinatous
•Deltoid
Inferiorly
•Long head of triceps brachii
•With in the joint
•Tendon of long head of biceps brachii.

19. Anteriorly
•Sub scapularis
•Coracobrachialis
•Short head of biceps
•Deltoid
Posteriorly
•Infra spinatous
•Teres minor
•Deltoid

20. Relations of shoulder joint

21. Movements -muscles
•Flexion- Pectoralis major,Anterior fibres of Deltoid
•Extension- Latissmus dorsi ,Posterior fibres of Deltoid
•Abduction- 0-15 degrees-Supraspinatus
15-90 degrees –deltoid
90-180 degrees-Serratus
anterior,Trapezius
•Adduction- Pectoralis major,Lattisimus Dorsi,Short
head of biceps, long head of triceps

22. •Medial Rotation – Pectoralis Major,Teres Major,
Lattisimus Dorsi, Deltoid.
•Lateral rotation - Deltoid, Teres Minor,Infra
spinatus

23. Range of motions

24. Blood supply of shoulder joint
• Anterior circumflex humeral vessels
• Posterior circumflex humeral vessels
• Suprascapular vessels
• Subscapularis vessels

25. Nerve supply
• Axillary nerve
• Musculocutaneous nerve
• Suprascapular nerve

26. Acromioclavicular joint
• Plain synovial joint
• Facets present between the lateral end of clavicle and Medial
marigin of acromian process of the scapula.
• Facets covered with fibro cartilage
• Bones held together by fibrous capsule and articular disc
• Blood supply – Supra scapular and thoraco acromial vessels
• Nerve supply- Suprascapular nerve
• Movements- IR, ER, Anterior/ Posterior tilt
Up ward/ Down ward rotation

27. Sternoclavicular joint
• Synovial joint
• Facets lined by fibro cartilage
• Compound joint  Medial end of clavicle
Clavicular notch of Manubrium sterni.
Upper surface of first costal cartilage.
• It is a complex joint, as its cavity sub divided in to supero
medial and infero lateral compartment by intra articular disc
• It is strong anterior and posteriorly due to presence of
anterior and posterior sternoclavicular ligaments

28. • Ligaments-Inter clavicular ligament
Costo clavicular ligament
• Blood supply- internal thoracic , supra scapular
arteries
• Nerve Supply- supra scapular nerve
• Movements -Protraction, Retraction
-Elevation, Depression
-Translations( Ant,Post,Lat,Med)

29. CORACOCLAVICULAR LIGAMENT
• The ligament consists of two parts
1. Conoid
2. Trapezoid
• Conoid is attached
above to inferior surface of the clavicle on
conoid tubercle.
Below to the root of the coracoid process

30. • Trapzoid is attached
above to trapezoid line on the inferior surface
of the lateral part of the clavicle.
Below to the upper surface of the coracoid
process.

32. BIOMECHANICS
• The science that deals with the study of the
forces (both internal and external) acting on
the joints and the effects produced by these
forces.

33. STATIC STABILIZERS
1. Glenoid labrum
2. Coracohumeral ligament
3. Superior glenohumeral ligament
4. Middle glenohumeral ligament
5. Inferior glenohumeral ligament complex
6. Posterior capsule

34. 1. Superior glenohumeral ligament -forms
part of rotatory interval
-prevents excessive inferior
translation and external rotation
2. Middle glenohumeral ligament –prevents
anterior translation of the humeral head
when the arm is abducted greater than 40
degree and externally rotated.
-Also prevents inferior translation of the
adducted and externally rotated shoulder

35. Inferior glenohumeral ligament
prevents the anteroinferior translation of
the humeral head when the shoulder is
abducted and externally rotated at 90 degree
Axillary pouch-on abduction prevent inferior
head translation

37. • Posterior capsule : prevents the posterior
displacement of the humeral head.

38. DYNAMIC STABILIZERS
• Rotator cuff muscles
• Long head of the biceps

39. • Rotator cuff muscles and tendon of long head
of biceps play a major role in the stability of
joint by acting as antagonists by acting in
opposite directions.
• This opposite forces maintain head centered
in the glenoid through full range of shoulder
movements.

40. • Loss of balance between these forces leads to
compression of rotator cuff and adjacent soft
tissue between humeral head and
coracoacromial arch leading to
IMPINGEMENT.

41. • Rotator cuff muscles function as head
compressors in any position of the
glenohumeral joint.
• Subscapularis-primary anterior compressor
• Supraspinatus-primary superior compressor
• Infraspinatus assisted by teres minor-primary
posterior compressor

42. • The humeral head is believed to be more convex in the
anterior-posterior direction than in the superior-inferior
direction.
• During active and passive arm elevation,the superior-inferior
translation of the humeral head is only 0.3 to 0.35 mm in
normal shoulders.
• Anterior-posterior translation is substantially larger as a result
of the bony configuration of the glenoid because it is more
concave in the superior-inferior direction than in the anterior-
posterior direction

43. • During elevation the deltoid is the prime
mover of the humeral head while the
supraspinatous exerts a depressive force that
stabilizes the joint’s centre of rotation.
• The biceps also acts as an accessory humeral
head depressor

44. SCAPULOTHORACIC
ARTICULATION
• Suspended and Controlled by
Serratus anterior :Holds the medial angle of
the scapula against the chest wall.
Trapezius : rotates and elevates the scapula
with elevation of the arm

45. • During elevation,the glenohumeral joint
rotates 2 degrees for every 1 degree of
scapulothoracic rotation.
• For 180 degree of abduction,there is 120
degrees from the glenohumeral joint and 60
degrees from the scapulothoracic joint.

46. GEOMETRY
Articular surface of humerus is spherical with an
arc of 160 degree covered by articular catilage
Radius of curvature is approximately 25mm is
slightly greater in males
Average neck shaft angle is 45 degree
Position of glenoid in relation to axis of the
scapula ranges from 2 degree of anteversion
to 7 degree of retroversion

47. FORCES
• The force couple in the frontal plane consists
of the deltoid and supraspinatus muscles as
elevators and inferior portions of the rotator-
cuff muscles as depressors.
• The force couple in the horizontal plane
comprises the subscapularis anteriorly and
infraspinatus and teres minor muscles
posteriorly .

48. RANGE OF MOVEMENTS
• FLEXION 0-180degrees
• Extension 0-60degrees
• Abduction 0-180degrees
• Adduction 180-0degree
• Lateral rotation 0-90degrees
• Medial rotation 0-90degrees

49. THANK YOU