Flexor Tendon Pulleys and Sheaths
- See: Flexor Tendon Repair, Pulley Reconstruction, Flexor Tendon Nutrition
- Flexor Tendon Pulleys:
- A1 pulley:
- arises from volar plate of MP joint, beginning 5 mm proximal to the MP joint and ending at the base of the proximal phalanx;
- average length of A1 pulley is 1 cm;
- proximal edge of the 1st annular pulley lies about 2 cm from the proximal finger crease;
- distal edge of A1 pulley lies about 1 cm from the proximal finger crease;
- note that the proximal phalangeal crease which lies over the mid portion of the proximal phalanx, and that the A2 pulley
begins and ends in the proximal half of the proximal phalanx;
- hence, a tendon sheath incision which extends past the level of proximal phalangeal crease will probably incise most the A2 pulley;
- note that at the level of the A1 pulley, the FDS flattens out and bifurcates, allowing the FDP tendon to pass superficial;
- ref: Anatomical Study of the A1 Pulley: Length and Location by Means of Cutaneous Landmarks on Palmar Surface
- A2 pulley
- arises from periosteum of proximal half of the proximal phalanx;
- total length is 20 mm, along the mid portion of the proximal phalanx;
- of all of the flexor tendon sheaths, this is probably the most important;
- vascular considerations:
- their is a avascular zone within the intrasynovial portion of the FDS and FDP tendons under the A2 pulley;
- distal to the A2 pulley, a digital arterial ladder branch provides arterial inflow to the vinculum to FDS and long vinculum FDP;
- in study by G. Mitsionis MD et al (JHS 1999), it was found that 25% of A2 or A4 pulleys may be excised either separately or in combination;
- these authors noted that even excision of upto 75% of the pulley resulted in only minimal decreases in PIP angular ROM;
- The second annular pulley: a histologic examination
- Flexor pulley system: anatomy, injury, and management.
- Importance of proximal A2 and A4 pulleys to maintaining kinematics in the hand: a biomechanical study
- C1 pulley;
- A3 pulley:
- arises from volar plate of PIP joint;
- in the report by Tang JB, et al, the authors studied the effects of the A3 pulley and adjacent sheath integrity on tendon function
at the proximal interphalangeal (PIP) joint was investigated in 21 fingers in 7 fresh-frozen cadaver hands;
- 11 fingers were tested after incision of the A3 pulley, of the A3 pulley and its distal sheath up to the A4 pulley, and of the
sheath from the A3 to A4 pulleys;
- tendon bowstringing was 0.3 mm after incision of A3 pulley, 0.6 mm after incision of A3 pulley with its distal sheath, 0.8 mm after
incision of pulley with its proximal sheath, 1.4 mm after incision of sheath from A3 to A4 pulleys, and 1.6 mm after
incision of sheath between A2 and A4 pulleys;
- sheath adjacent to the A3 pulley plays an important role in restraining tendon bowstringing at the PIP joint, whereas A3
pulley alone is of little importance;
- Effect of A3 pulley and adjacent sheath integrity on tendon excursion and bowstringing.
- The A3 pulley
- C2 pulley
- A4 pulley
- arises from periosteum of mid-portion of middle phalanx;
- this is the second most important flexor tendon sheath pulley (after the A2);
- when the FDS tendon is lost, the A4 pulley becomes most essential;
- there is an avascular zone of the FDP underneath the A4 pulley;
- in study by Mitsionis G, et al (1999), it was found that 25% of A2 or A4 pulleys may be excised either separately or in combination;
- these authors noted that even excision of up to 75% of the pulley resulted in only minimal decreases in PIP angular ROM;
- Flexor pulley system: anatomy, injury, and management
- Importance of proximal A2 and A4 pulleys to maintaining kinematics in the hand: a biomechanical study.
- C3 pulley;
- A5 pulley arises from volar plate of the DIP joint;
- reference: - Anatomy and histology of the A5 pulley
- An unusual role of the vinculum after complete laceration of the flexor tendons
- Biomechanical Influence of the Vincula Tendinum on Digital Motion After Isolated Flexor Tendon Injury: A Cadaveric Study- Vincula tendinum of human hands with special reference to vascular patency
- Vascular anatomy of flexor tendons. I. Vincular system and blood supply of the profundus tendon in the digital sheath
- [The Omega "Omega" pulley plasty. A new technique to increase the diameter of the annular flexor digital pulleys].
- The vincula to the flexor tendons of the hand
- Accessory Roles of the Vinculum Breve of the Flexor Digitorum Profundus and Check-Rein Ligaments at the Distal Interphalangeal Joint
Digital flexor tendon sheath: an anatomic study.
Anatomy of the finger flexor tendon sheath and pulley system. JR Doyle. J. Hand Surg. Vol 13-A. 1988. p 473.
Palmar and digital flexor tendon pulleys.
Year Book: Postnatal Growth and Development of the Flexor Tendon Pulley System.
Tendon and pulleys at the metacarpophalangeal joint of a finger.
Effect of pulley integrity on excursions and work of flexion in healing flexor tendons
Clinical anatomy of the chiasma tendlinum (camper) in the fingers
Original Text by Clifford R. Wheeless, III, MD.
Last updated by Clifford R. Wheeless, III, MD on Thursday, July 9, 2015 2:11 pm