Flexor Pulley System of the Hand
(Redirected from A1 Pulley of the Hand)
Introduction
Other Names
- Annular ligaments of fingers
- A pulleys
- Flexor Pulley System of the Hand
General
- Flexor pulley system of the hand is a complex structure that coordinates flexion of the digits
- Main purpose is to hold the flexor tendons against the phalanges
- This prevents them from pulling away, bowstringing
- Facilitates efficient flexion of individual digits by the long flexor muscles
General Composition
- Long flexor tendons
- Annular pulleys: 5 with each finger, 2 with the thumb
- Cruciate pulleys: 3 with each finger
- Oblique pulley: 1 with the thumb
Long Flexor Tendons
- Arise from the flexor digitorum superficialis, flexor digitorum profundus
- Enter the hand through the carpal tunnel
- Once in the hand, the tendons fan out along their respective fibrous flexor sheaths
- Each sheath is a strong ligamentous tunnel associated with an individual digit
- At the base of the proximal phalanx
- FDS splits into two and attaches at the base of the middle phalanx
- FDP passes between them and attaches at the base of the distal phalanx
Annular Pulleys
- Represent fiber areas where the fibrous flexor sheaths are reinforced by circular fibers
- A2 to A4 are most important in preventing bowstringing
- A1: overlies the metacarpophalangeal joint
- A2: overlies the proximal aspect of the proximal phalanx
- A3: overlies the proximal interphalangeal joint
- A4: overlies the mid-portion of the middle phalanx
- A5: overlies the distal interphalangeal joint
Cruciate Pulleys
- Areas where the fibrous flexor sheaths are reinforced by cruciform fibers
- C1: located between A2 and A3
- C2: located between A3 and A4
- C3: located between A4 and A5
Flexor Pulley System of the Thumb
- Long flexor tendon arises from flexor pollicis longus
- Passes through carpal tunnel as it enters the hand
- FPL tendon enters fibrous sheath at the base of the thumb
- Fibrous sheath is reinforced by 3 pulleys:
- A1: overlies the metacarpophalangeal joint
- Oblique: overlies the proximal half of proximal phalanx
- A2: overlies the distal half of proximal phalanx
Description of the A1 Pulley
- Arises from the volar plate of the metacarpophalangeal joint (MCP)
- Located ~5 mm proximal to the joint
- Extends to the base of the proximal phalanx
- Average length 1 cm
- Proximal crease of the hand can be used as a surface marker for the A1 pulley[4]
- Proximal edge of A1 pulley lies ~1.5-2 cm from proximal finger crease
- Distal edge of A1 pulley lies approximately 1 cm from proximal finger crease
Actions
- Facilitates efficient flexion of individual digits by the long flexor muscles
- Main purpose is to hold the flexor tendons against the phalanges
- This prevents them from pulling away, bowstringing
Vascular Supply
- Needs to be updated
Innervation
- Needs to be updated
Clinical Significance
See Also
References
- ↑ 1.0 1.1 1.2 Image courtesy of teachmeanatomy.info, "flexor pulley system of the hand"
- ↑ Bajaj, Ajay, et al. "Soft Hand Exoskeleton for Adaptive Grasping using a Novel Differential Mechanism."
- ↑ Zhong, Wei-xing, et al. "Identification of the length and location of the A1 pulley combining palpation technique with palm landmarks: a cadaveric study." Scientific Reports 13.1 (2023): 22801.
- ↑ Florini HJ, Santos JBG, Kirakaw CK, et al. Anatomical study of the a1 pulley: length and location by means of cutaneous landmarks on the palmar surface. J Hand Surg. March 2011;36(3):464–468.