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 bowstringing will occur if both A1 and oblique pulleys are cut 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) bowstringing will occur if both A1 and oblique pulleys are cut 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 if A2 is intact, cutting A1 or oblique pulley will not result in bowstringing 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) biomechanically strongest construct complications most worrisome is phalangeal fracture stiffness persistent bowstringing inadequate tensioning failure to remove scar tissue dorsal to tendon (tendon is not pressed against bone) 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