1. Biomechanics of Shoulder Complex.
Prepared by: Dr. Faryal Zaidi MSPT(KMU), BSPT(UHS), T-dpt*(KMU)

2. OBJECTIVES At the end of this lecture students should be able to:
Define different terms of biomechanics
Identify different structures in shoulder complex
Explain kinetics and kinematics of shoulder joint
Describe different pathologies of shoulder complex

3. What is biomechanics?

4. Biomechanics

5. Biomechanics
The term biomechanics combines the prefix bio, meaning “life,” with the field of mechanics, which is the study of the actions of forces, (both internal muscle forces and external forces.) In biomechanics we analyze the mechanical aspects of living organisms.

7. Why study biomechanics?

8. Subdivisions
statics: study of systems in constant motion, (including zero motion)
dynamics: study of systems subject to acceleration
kinematics: study of the appearance or description of motion
kinetics: study of the actions of forces (Force can be thought of as a push or pull acting on a body.)

9. kinematics
What we visually observe of a body in motion is called the kinematics of the movement. Kinematics is the study of the size, sequencing, and timing of movement, without regard for the forces that cause or result from the motion. The kinematics of an exercise or a sport skill is known, more commonly, as form or technique.

10. kinematics

11. Kinetics
Kinetics is the study of forces, including internal forces (muscle forces) and external forces (the forces of gravity).

12. Kinetics

13. Biomechanics VS kinesiology???

14. Shoulder complex

17. OSTEOLOGY

21. SHOULDER COMPLEX
Five Functional Joints 1. Glenohumeral Joint 2. Subacromial 3. Scapulothroasic 4. Acromioclavicular 5. Sternoclavicular

23. SC JOINT Clavicle articulates with manubrium of the sternum
Weak bony structure but held by strong ligaments
Fibrocartilaginous disk between articulating surfaces
Shock absorber and helps prevent displacement forward
Clavicle permitted to move up and down, forward and backward and in rotation
Clavicle must elevate 40 degrees to allow upward rotation of scapula and thus shoulder abduction

24. SC JOINT The only attachment of the upper extremity to axial skeleton
Plane synovial joint with degree of freedom 6, having joint capsule, joint disk and three major ligaments
Movement of the SC joint produces scapular movements, if it is fused the equal amount of movement will occur at AC joint

26. LIGAMENTS OF SC JOINT LIGAMENTS: Interclavicular Lig.
Costoclavicular Lig.
Posterior Ligament Sternoclavicular

28. MOVEMENTS OF SC JOINT
Movements in horizontal plane:
Protraction (30 degree) limited by costoclavicular and post. capsule
Retraction (30 degree) limited by costoclavicular and ant. capsule

29. MOVEMENTS OF SC JOINT Elevation (48 degree)
limited by costoclavicular
Depression (less than15 degree)
limited by first rib
Axial Rotation
Ant. Rot. (very limited – 10 degree)
Post. Rot. (50 degree)

31. Axial rotation

32. AC JOINT Lateral end of clavicle with acromion process of scapula
Weak joint and susceptible to sprain and separation
Joint capsule n two major ligaments and disk – present or absent

33. AC JOINT LIGAMENTS: Coracoclavicular Acromioclavicular Coracoacromial:
Medial: Conoid
Lateral: Trapezoid
Acromioclavicular
Superior
Inferior
Coracoacromial:
Coracoids process to acromiom process
Closed packed position is
when the humerus is abducted to 90 degree.
The fibers of the superior AC ligament are reinforced
by aponeurotic fibers of the trapezius and deltoid muscles,
which makes the superior joint support stronger
than the inferior. The trapezoid
ligament is quadrilateral in shape and is nearly
horizontal in orientation. The conoid ligament, medial
and slightly posterior to the trapezoid, is more triangular
and vertically oriented.

34. MOVEMENTS OF AC JOINT Internal and external rotation
Bringing the glenoid fossa of the scapula anteromedially and posterolaterally, respectively
Anterior and posterior tiping or tilting
Ant. - acromion tipping forward and the inferior angle tipping backward
Post. - rotate the acromion backward and the inferior angle forward.
Upward and downward rotation
Upward rotation tilts the glenoid fossa upward and downward rotation is the opposite motion.

35. Internal/external rotation

36. Anterior/posterior tipping

37. Upward/downward rotation

38. CORACOACROMIAL ARCH
Arch over the GH joint formed by Coracoacromial arch,acromion and coracoid process
Sub acromial space: area in between CA arch and humeral head
Supraspinatus tendon, long head biceps tendon, and sub acromial bursa
Subject to irritation and inflammation as a result of excessive humeral head translation or impingement from repeated overhead activity

39. SUBACROMIAL SPACE

40. Structures Within Suprahumeral Space
1. Long head of biceps 2. Superior capsule 3. Supraspinatus tendon 4. Upper margins of subscapularis & infraspinatus tendons 5. Subacromial bursa 6. Inferior surface of the A-C joint

41. SUBACROMIAL SPACE Clinical Relevance
Avoidance of impingement during elevation of the arm requires
External rotation of humerus to clear greater tuberosity
Upward rotation of scapula to elevate lateral end of acromiom

42. SUBACROMIAL SPACE Primary Impingement Secondary Impingement
Structural stenosis of subacromial space
Secondary Impingement
Functional stenosis of subacromial space due
to abnormal arthrokinematics

43. Glenohumeral Joint Three degrees of freedom Stability provided by
Ball and socket, synovial joint in which round head of humerus articulates with shallow glenoid fossa of scapula
stabilized slightly by fibrocartilaginous rim called the Glenoid Labrum
Humeral head larger than glenoid fossa
At any point during elevation of shoulder only 25 to 30% of humeral head is in contact with glenoid Statically stabilized by labrum and capsular ligaments Dynamically stabilized by deltoid and rotator cuff muscles
Three degrees of freedom
Stability provided by
Passive restraints
Active restraints

45. GH ARTICULATING SURFACES

46. Glenoid Labrum
When the arms hang dependently at the side, the two articular surfaces of the GH joint have little contact. The majority of the time, the inferior surface of the humeral head rests on only a small inferior portion of the fossa. The total available articular
surface of the glenoid fossa is enhanced by an accessory structure, the glenoid labrum. This structure surrounds and is attached to the periphery of the glenoid fossa enhancing the depth or curvature of the fossa by approximately 50%.
the labrum was traditionally thought to be synoviumlined fibrocartilage, more recently it has been proposed that it is actually a redundant fold of dense fibrous connective tissue with little fibrocartilage other than at the attachment of the labrum to the periphery of the fossa.
The labrum superiorly is loosely attached, whereas the inferior portion is firmly attached and relatively immobile.The glenoid labrum also serves as the attachment site for the glenohumeral ligaments and the tendon of the long head of the biceps brachii.

47. GH CAPSULE
The entire GH joint is surrounded by a large, loose capsule that is taut superiorly and slack anteriorly and inferiorly in the resting position (arm dependent at the side).The capsular surface area is twice that of the humeral head.39 More than 2.5 cm of distraction of the head from the glenoid fossa is allowed in the loose-packed position.
The relative laxity of the GH capsule is necessary for the large excursion of joint surfaces but provides little stability without the reinforcement of ligaments and muscles. When the humerus is abducted and laterally rotated on the glenoid fossa, the capsule twists on itself and tightens, making abduction and lateral rotation the close-packed position for the GH joint

49. GH LIGAMENTS
SGHL
MGHL
IGHL
Anterior band
Posterior band
Axillary band

51. Restraints to External Rotation
Dependent on arm position
0° - SGHL, C-H & subscapular
45° - SGHL & MGHL
90° - anterior band IGHLC

52. Restraints to Internal Rotation
Dependent on arm position
0° - posterior band of IGHLC
45° - anterior & posterior band of IGHLC
90° - anterior & posterior band of IGHLC

54. Restraints to Inferior Translation
Dependent on arm position
0° - SGHL, C-H
90° - IGHLC

55. Glenohumeral Motion Scapular Plane: Flexion/extension - 120°
Abduction/adduction - 120°
External/internal rotation
Horizontal abduction/adduction

56. Arthrokinematics of the GH Joint

57. CONVEX-CONCAVE RULE

58. DOWNWARD GLIDE

59. Scapulo thoracic (ST) Joint
Not a true joint, but movement of scapula on thoracic cage is critical to joint motion
Scapula capable of upward/downward rotation, external/internal rotation & anterior/posterior tipping
In addition to rotating other motions include scapular elevation and depression & protraction (abduction) and retraction (adduction)

60. ST Joint
During humeral elevation (flexion, abduction and scaption) scapula and humerus must move in synchronous fashion
Often termed scapulohumeral rhythm
Total range 180°: GH joint, 60° of scapular moments
Ratio of 2:1, degrees of GH movement to scapular movement after 30 degrees of abduction and 45 to 6 degrees of flexion
Maintain joint congruency
Length-tension relationship for numerous muscles
Adequate subacromial space

61. Scapulo humeral rhythm
During humeral elevation
Scapula upwardly rotates
Posteriorly tips
Externally rotates
Elevates
& Retracts
Alterations in these movement patterns can cause a variety of shoulder conditions

62. MOVEMENTS OF THE SCAPULA
Upward/Downward Rotation