biomechanics of shoulder01.ppt2121254258

biomechanics of shoulder

1. Biomechanics of Biomechanics of
S
houlder Joint
S
houlder Joint
PresentedPresented
ByBy
Dr. Nazish RafiqueDr. Nazish Rafique
LecturerLecturer

2. The shoulder is the most complex joint in the
human body.
Joint which has a high degree of mobility but
not without compromising stability
Involved in a variety of overhead activities
I
ntroduction

3. C
omponents of the
S
houlder Complex

Bones are :
Clavicle
Scapula
Humerus
Joints are :
Sternoclavicle (SC) joint.
Acromioclavicular (AC) joint.
Glenohumeral (GH) joint.
Scapulothoracic (ST) joint.
 costoclavicular joint.

5. S
ternoclavicular
(
SC)Joint
 Synovial joint, saddle like
shape, joint between the
proximal clavicle and the
manubrium of the sternum.
This joint provides the major
axis of rotation for
movements of the clavicle
and scapula.

6. S
ternoclavicular Disk
A fibrocartilaginous articular disc improves the fit
of the articulating bone surfaces
and serves as a shock absorber.
The SC disk serves an important
stability function by increasing
joint congruence and absorbing
forces that may be transmitted
along the clavicle from its
lateral end.

7. T
hree-Compartment SC Joint
Three functional units of the SC
joint:
Lateral compartment between
the disk and clavicle for
elevation and depression,
Medial compartment between
the disk and manubrium for
protraction and retraction,
Costoclavicular joint for anterior
and posterior long axis rotation.

8. The clavicles and the scapulae make up the
shoulder girdle.
Most of the motion of the shoulder girdle
takes place at the sternoclavicular joints.
The close-packed position for the SC joint
occurs with maximal shoulder elevation.
S
ternoclavicular
(
SC)Joint

9. S
ternoclavicular (SC)Joint
L
igaments
Three ligaments:
Sternoclavicular ligaments,
Costoclavicular ligament,
Interclavicular ligament.

10. L
igaments
Costo-clavicular ligament is a very strong ligament
found between the clavicle & the interclavicular
ligament. Resist upward and posterior displacement
of clavicle.
The interclavicular ligament resists excessive
depression of the distal clavicle and superior glide of
the medial end of the clavicle.
The limitation to clavicular depression is critical to
protecting structures such as the brachial plexus and
subclavian artery that pass under the clavicle and
over the first rib.

11. Sternoclavicular ligaments: The anterior and posterior
SC ligaments reinforce the capsule and function
primarily to check anterior and posterior translatory
movement of the medial end of the clavicle.

12. Clavicle
The clavicle serves four roles:
Providing a barrier to protect underlying structures.
Acting as a strut to stabilize the shoulder.
Prevent medial displacement when the muscles
contract.
Preventing an inferior migration of the shoulder
girdle.

14. S
ternoclavicular (SC)Joint
movement
The three rotatory degrees at the SC joint:
Elevation/depression
Protraction/retraction
Anterior/posterior rotation of the clavicle

15. E
levation/Depression:
Clavicular elevation/depression at the SC joint occurs as movement
of the lateral clavicle about an A-P axis. The medial clavicle also has
small magnitudes of medial/lateral translation and superior/inferior
translation at the SC joint.
Elevation/depression: 30
o

16. P
rotraction/Retraction
Clavicular protraction/retraction at the SC joint occurs as
movement of the lateral clavicle (and attached scapula) around a
vertical axis. The medial clavicle also has a small magnitude of
anterior/posterior translation at the SC joint.
Protraction /Retraction:15
o
-20
o
/20
o
-30
o

17. A
nterior/posterior rotation
Clavicular rotation at the SC joint occurs as a spin of the entire
clavicle around a long axis that has a medial/lateral orientation. As
the clavicle posterior rotates, the lateral end flips up; anterior
rotation is a return to resting position.
Anterior/Posterior Rotation: less than 50
o

18. 4 degrees of clavicular elevation
for every 10 degrees of arm
elevation.

19. A
cromioclavicular (AC) joint
The articulation of the acromion process of
the scapula with the distal end of the clavicle.
Plane synovial joint.
The close-packed position of the AC joint
occurs when the humerus is abducted to 90°.

21. A
cromioclavicular
(
AC)
Joint
D
isk
The disk of the AC
joint is variable in
size between
individuals.
Through 2 years of
age, the joint is
actually a
fibrocartilaginos
union.

22. A
cromioclavicular Capsule
The capsule of the AC joint is weak
and cannot maintain integrity of the
joint without reinforcement of the
ligaments.

23. A
cromioclavicular Joint
L
igament
The important ligament are
Superior acromioclavicular ligament
Inferior acromioclavicular ligament
Coracoclavicular ligaments

24. S
uperior acromioclavicular
ligament
The superior acromioclavicular ligament
assists the capsule in apposing articular
surfaces and in controlling A-P joint stability.
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.

25. C
oracoclavicular
ligament
Divided into two parts:
Lateral portion, the trapezoid ligament:
majority of resistance to posterior translatory
forces applied to the distal clavicle.
Medial portion, the conoid ligament: The
conoid portion of the coracoclavicular
ligament provides the primary restraint for
the AC joint in the superior and inferior
directions.

27. A
cromioclavicular Joint
M
ovement
The articular facets of the AC joint are
small, afford limited motion,
Internal/External rotation,
Anterior/Posterior tipping or tilting,
Upward/Downward rotation.

28. I
nternal/External rotation
Internal/external rotation of the scapula
in relation to the clavicle occurs around
an approximately vertical axis through
the AC joint.
Internal/external rotation: 30
o

30. A
nterior/Posterior
tipping/tilting
Anterior/Posterior tipping or tilting of
the scapula in relation to the clavicle
around an oblique coronal axis through
the joint.
Anterior/Posterior tipping: 60
o

32. U
pward/Downward Rotation
Upward/Downward rotation of the
scapula in relation to the clavicle about
an oblique A-P axis.
Upward/Downward rotation: 30
o

35. C
oracoclavicular Joint
The coracoclavicular joint is a
syndesmosis,
Formed where the coracoid process of
the scapula and the inferior surface of
the clavicle are bound together by the
coracoclavicular ligament.
This joint permits little movement.