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Wheeless' Textbook of Orthopaedics

Flexor Tendon Pulleys and Sheaths


- See: Flexor Tendon RepairPulley 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;
           - references:
                   - Feasibility of partial A2 and A4 pulley excision: effect on finger flexor tendon biomechanics.
                   - The second annular pulley: a histologic examination  
                   - The effect of partial A2 pulley excision on gliding resistance and pulley strength in vitro.
                   - "Venting" or partial lateral release of the A2 and A4 pulleys after repair of zone 2 flexor tendon injuries. 
                   - Flexor tendon pulley V-Y plasty: an alternative to pulley venting or resection
                   - A2 pulley incision or one slip of the superficialis improves flexor tendon repairs.
                   - Three-loop technique for A2 pulley reconstruction.

    - 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;
                 - references:
                            - 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;
           - references:
                   - Feasibility of partial A2 and A4 pulley excision: effect on finger flexor tendon biomechanics. 
                   - "Venting" or partial lateral release of the A2 and A4 pulleys after repair of zone 2 flexor tendon injuries. 
                   - Quantification of partial or complete A4 pulley release with FDP repair in cadaveric tendons 
                   - The flexor digitorum profundus "demi-tendon"--a new technique for passage of the flexor profundus tendon through the A4 pulley.
    - C3 pulley;
    - A5 pulley arises from volar plate of the DIP joint;
           - reference: - Anatomy and histology of the A5 pulley

- Vincula:
     - references:
            - An unusual role of the vinculum after complete laceration of the flexor tendons             - 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

Flexor tendon pulley V-Y plasty: an alternative to pulley venting or resection.

"Venting" or partial lateral release of the A2 and A4 pulleys after repair of zone 2 flexor tendon injuries.

Clinical anatomy of the chiasma tendlinum (camper) in the fingers



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Monday, December 31, 2012 2:22 pm