BY: AJAY KUMAR & SYED MASOOD

 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.

 In the human body,
in most cases the
pulley is replaced by
a bone, cartilage or
ligament and the
cord is replaced by a
muscle tendon.
 The tendon is
lubricated in a
manner so that it
may easily slide over
the pulley.
anat.pulley

 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. anat. 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.

 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.

 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.
MCP
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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.

 There are mainly
two types of pulleys
in the hand:
 Annular Pulleys(
five in number).
 Cruciate pulleys or
connective tissue
pulleys(three in
number).
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 There are five
annular pulleys in
the fingers, and
they are named
A1,A2,A3,A4 & A5.
 The A1, A3, and A5
pulleys are smaller
and considered
minor pulleys
(mostly due to size
and lack of
importance).

 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

 A1 pulley: The first annular pulley
arises from the palmar plate and
proximal portion of the proximal
phalanx. The A1 pulley overlies the
membranous sheath at the level of
the MCP joint and is
approximately 8 mm in width.
 A2 pulley: The second annular
pulley consists of oblique fibers
that overlie annular fibers. It
originates from the proximal and
lateral areas of the proximal
phalanx and is approximately 17
mm in width.
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MCP

 A3 pulley: The third annular pulley is
located at the level of the PIP joint. This
pulley attaches to the palmar plate and
is approximately 3 mm in width.
 A4 pulley: Like the A2 pulley, the
fourth annular pulley, located in the
middle phalanx, also consists of oblique
fibers overlying annular fibers and is
always preserved during surgery of the
retinacular system. The A4 pulley is
approximately 6.7 mm in width and has
been shown to be the most important
biomechanical pulley for maintaining
independent interphalangeal joint
function.
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MCP

 A5 pulley :The fifth
annular pulley is located
proximal to the DIP joint,
just proximal to the
termination of the
membranous sheath. The
A5 pulley is the thinnest of
the 5 annular pulleys and
has a width of 4 mm.
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MCP

 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.

 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.

 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.
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 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
 The cruciate pulleys are much
smaller than the annular pulleys.
There are three cruciate pulleys,
designated as C1, C2, and C3
pulleys.

 C1 Pulley: The first cruciform
pulley lies just distal to the A2
pulley.
 C2 Pulley: The second cruciform
pulley is located in the space
between the A3 and A4 pulleys.
 C3 Pulley: The third cruciform
pulley is located distal to the A4
pulley. A number of anatomic
variations have been described
for the retinacular system
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MCP

THANK
UUUUUUUUUUU.