ANATOMICAL PULLEYS.ppt

ANATOMICAL PULLEYS

1. ANATOMICAL PULLEYS
BY: AJAY KUMAR & SYED MASOOD

2. PULLEYS:
A pulley is a simple mechanical machine
and consists of a wheel that turns readily
on an axle.
The wheel is usually grooved for a rope or
a wire cable.

3. ANATOMICAL PULLEYS:
In the human body, in most cases the
pulley isreplaced by abone, cartilageor
ligament and the cord is replaced bya
muscle tendon.
The tendon is lubricated in a manner so
that it may easily slide over the pulley.

4. ANATOMICAL PULLEYS:
The fibers of a muscle or a muscle tendon
wrap around a bone or are deflected by a bone
prominence.
When the direction of pull is altered, the bone
or bony prominence causing the deflection
forms an anatomical pulley.

5. Functions of a pulley:
Redirect force to make task easier.
It makes task easier by deflecting the action
line of a muscle away from the joint axis, thus
inc the MA for a muscle force.

6. PULLEYS OF HAND:
The skeletal structure of the hand and fingers
is a set of rigid bones. Consequently, it takes
great muscular control to perform the fine
movements of the hand. Without this highly
specialized level of control, we would have
serious challenges performing all kinds of
activities from simply grasping an object to the
detailed motor control required to play a
musical instrument or writing.

7. PULLEYS OF HAND:
A unique biomechanical pulley system
provides the high level of control necessary to
move the rigid finger bones with precision. The
flexor tendons of the fingers run along the
anterior surface of the fingers, and these
tendons are tethered close to the bones by
connective tissue "pulleys" at eight different
locations from the metacarpophalangeal
(MCP) joint to the distal phalanx.

8. PULLEYS OF HAND:
Because the tendons are closely tethered to
the bones, their pulling force is more efficient.
Let's take a look at these pulleys, how they
work and what happens when they don't.

9. PULLEYS OF HAND:
There are mainly two types of
pulleysin the hand:
Annular Pulleys( five in number).
Cruciate pulleys or connective
tissue pulleys(three in number).

10. Annular pulleys:
There are five annular pulleys in the fingers,
and they are named A1 through A5.
The A1, A3, and A5 pulleys are smaller and
considered minor pulleys
(mostly due to size and
lack of importance).

11. Annular pulleys:
The A2 and A4 pulleys are larger and are
sometimes called the major pulleys.
The A1, A3, and A5 pulleys are located at the
MCP, PIP and DIP joints respectively.
The A2 and A4 pulleys are located in the
middle of the proximal and middle phalanx
respectively

12. Damage to annular pulleys:
The annular pulleys may be damaged from an
acute injury or from various degenerative
conditions in the fingers.
An example of the detrimental effect of rupture
of the annular pulleys is shown in Figure.

13. Damage to annular pulleys:
In this image, the A3 pulley has been
completely ruptured and there is a partial
rupture to the A2 pulley. As a result, the tendon
is pulled away from the PIP joint, in what is
referred to as a bowstringing effect.
With the tendon pulled away from the PIP joint,
its power is reduced and it is no longer able to
produce normal range of motion. As a result,
the hand is significantly weaker in gripping
activities.

14. Cruciate pulleys:
A second set of connective-tissue pulleys,
called cruciate pulleys, gives additional
support and stability to the tendon sheaths.
The term cruciate means cross, and you can
see by their structure where they get their
name.
The cruciate pulleys are much smaller than the
annular pulleys. There are three cruciate
pulleys, designated as C1, C2, and C3.

15. Cruciate pulleys:
Their role for improving the flexor tendon's
angle of pull is not as great, so if they are
damaged, finger movement is not impaired as
much as with the annular pulleys.