The effect of partial A2 pulley excision on gliding resistance and pulley strength in vitro.

PURPOSE The purpose of this study was to investigate the effect of partial excision of the A2 pulley on the gliding resistance and the strength of the residual pulleys in a human in vitro model with or without tendon repair. METHODS We used 32 cadaveric human fingers from 11 cadavers. The A2 pulley was excised successively 25%, 50%, and 75%, cutting either from the distal toward the proximal edge or from the proximal toward the distal edge. The peak gliding resistance between intact or repaired tendon and partially excised pulley was measured. After the gliding resistance test the pulley breaking strength and stiffness were measured. RESULTS The peak gliding resistance exhibited the same statistical trends for the intact tendon and the repaired tendon groups. In the intact tendon groups the sequential excision of the A2 pulley from the distal toward the proximal edge had no significant effect on peak gliding resistance. With the A2 pulley cut from the proximal toward the distal edge, however, there was a significant increase in peak gliding resistance with 25% remaining pulley distally (0.82 N) compared with intact (0.42 N), 75% (0.57 N), and 50% (0.63 N) pulley remaining proximally. The 25% distal portion of the A2 pulley had a significantly higher breaking strength than the 25% proximal portion (160 N vs 96.7 N, respectively). Similarly the stiffness was greater in the distal portion compared with the proximal portion (120 N/mm vs 70.5 N/mm). CONCLUSIONS After A2 pulley excision the size and location of the remaining pulley affects the resulting gliding resistance, stiffness, and failure strength. At the most extreme excision level tested the residual 25% distal segment of the pulley exhibited significantly greater peak gliding resistance compared with the 25% proximal segment, as well as greater strength and stiffness. If excision of the A2 pulley is limited to 50% (either proximally or distally), however, there is little increase in gliding resistance and the retained strength of the pulley is substantial. These data support the clinical practice of partial pulley excision, up to a limit of 50%, to facilitate exposure and tendon repair.