2. PULLEY SYSTEM:
The flexor pulley system of the hand is a complex
structure that co-ordinates flexion of the digits. It
consists of: Long flexor tendons – and their
associated synovial sheaths. ... Cruciate pulleys – 3
associated with each finger. Oblique pulley – 1
associated with the thumb.
Any interruption in pulleys or digital tendon
sheaths can result in substantial impairment of
FDS and FDP muscle functioning.
Flexor pulley system of hand
3. Flexor Tendon Pulley System of Hand
Flexor tendon pulley system maintains flexor tendons close to
joint’s axis of motion and prevents bowstringing.
Membranous part is composed of visceral and parietal layers. It
carries the flexor digitorum profundus and flexor digitorum
superficialis tendons in the distal aspect of the hand.
Digital flexor sheath is a synovial sheath which consists of
membranous and retinacular parts.
Digital sheath serves following functions:
Facilitates smooth gliding of the tendons
Pulleys from retinacular component provide a mechanical
advantage to flexion
Synovial fluid bathes and provides nutrition
4. Components Flexor Tendon Pulley
System
Palmar Aponeurosis Pulley
It is formed of transverse fascicular bands
approximately 1 cm in width arising from the
palmar aponeurosis.
This pulley moves closer to tendon surface
during grasping due to increased tension on the
palmar fascia by the flexor carpi ulnaris and
palmaris longus muscles.
5. ANNULAR PULLEYS.
A1 PULLEY:
A1 pulley is first annular pulley which arises from the palmar
plate and proximal portion of the proximal phalanx
This pulley is frequently involved in trigger finger.
A2 PULLEY:
The second annular pulley originates from the proximal and
lateral areas of the proximal phalanx.
The A2 pulley have been shown to be important in finger
flexor tendon function.
A3 PULLEY:
This is the third annular pulley and is located at the level of the
proximal interphalangeal joint.
A4 PULLEY:
A4 lies centrally on the middle phalanx.
It is considered the second most important flexor
tendon sheath pulley (after the A2)
It is a biomechanical pulley for maintaining independent
interphalangeal joint function.
A5 PULLEY: A5 lies at the base of the distal phalanx.
6. CRUCIATE PULLEY
3 obliquely oriented Cruciate Pulleys
(crisscrossing)
C1 : located between the A2 and A3 pulleys
C2 lies between the A3 and A4 pulleys
C3 lies between the A4 and A5 pulleys.
