Flexor Pulley System

Topic updated on 09/25/16 9:16am
Flexor Pulley System-Fingers
  • Annular ligaments
    • A2 and A4 are critical to prevent bowstringing
      • most biomechanically important  
    • A1, A3, and A5 overlie the MP, PIP and DIP joints respectively 
      • originate from palmar plate  
    • A1 pulley most commonly involved in trigger finger
  • Cruciate pulleys
    • function to prevent sheath collapse and expansion during digital motion
    • facilitates approximation of annular pulleys during flexion
    • 3 total at the level of the joints
Flexor Pulley System-Thumb

  • Oblique pulley (3-5mm)
    • originates at proximal half of proximal phalanx
    • most important pulley in thumb 
    • functions like cruciate pulley in fingers
      • in fingers A1-A2-C1-A3
      • in thumb A1-Av-oblique-A2
    • facilitates full excursion of FPL
    • prevents bowstringing of FPL 
  • Annular pulleys
    • A1 pulley (4-8mm)
      • at the level of the volar plate at the MCP joint
      • ~6mm in length
      • radial digital nerve is closest (2.7mm)
      • ulnar digital nerve is less close (5.4mm)
    • Av pulley (annular variable pulley) (4-8mm)
      • between A1 and oblique pulleys
        • previously thought to be part of oblique pulley
      • function
        • helps prevent bowstringing
      • 3 types
        • Type I - transverse, parallel to A1, with gap between Av and A1  
        • Type II - no gap between Av and A1  
        • Type III - triangular/oblique Av pulley with fibers converging to radial side  
    • A2 pulley (5-10mm)
      • contributes least to arc of motion of thumb
Pulley Reconstruction
  • Goals
    • preserve or reconstruct 3 or more pulleys
    • A2 is important
    • unclear if A4 reconstruction is absolutely necessary (can be sacrificed during acute flexor tendon surgery)
  • Graft material
    • extensor retinaculum 
      • synovialized pulley surface, provides least gliding resistance
    • excised tendon material
    • palmaris or plantaris
    • FDS
    • flexor tendon allograft
  • Techniques
    • first excise all scar dorsal to the flexor tendon
    • around-the-bone (encircling technique)
      • single-loop (Bunnell)  
      • triple loop (Okutsu)  
    • nonencircling reconstruction
      • ever-present-rim (Kleinert)  
      • belt-loop (Karev)  
      • extensor retinaculum (Lister)
      • palmaris longus transplantation through volar plate (Doyle and Blythe)
  • Location Specific
    • proximal phalanx (for A2 pulley)
      • use 3 loops (around-the-bone) - strongest reconstruction
      • pass DEEP to extensor mechanism
    • middle phalanx (for A4 pulley)
      • use 2 loops (around-the-bone)
      • pass SUPERFICIAL to extensors


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Qbank (2 Questions)

(OBQ08.274) Which of the following flexor tendon annular pulleys originate from palmar plates overlying joints? Topic Review Topic

1. A1, A3, A5
2. A2, A4
3. A1, A2, A4
4. A1, A2, A3
5. A2, A4, A5

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