Effect of A2 pulley release on repaired tendon gliding resistance and rupture in a chicken model

Release of part of the A2 pulley has been suggested to improve function after zone II primary flexor tendon repairs. The purpose of this study was to measure the effect of A2 pulley release compared with pulley preservation on repaired tendon gliding resistance and rupture in the early postoperative period in a chicken model.

We divided 104 long toes from 52 Leghorn chickens into 2 experimental groups. In group 1, the flexor digitorum profundus tendons were cut completely and repaired surgically with either release or preservation of the A2 pulley. The tendon laceration was positioned so that the repair had to glide through the pulley with toe flexion. The toes were subjected to simulated active flexion at the end of the 2nd and 4th postsurgical weeks. The rupture rates of the tendons were recorded. In group 2, the volar two thirds of the tendons were cut and repaired, also in the region of the A2 pulley, with the pulley released or preserved. The force resisting tendon motion and the work of digital flexion with simulated active digital flexion were tested 3, 5, 7, and 14 days after surgery.

At the end of the 2nd and 4th weeks, the tendon repairs showed significantly higher rates of rupture in the presence of an intact A2 pulley compared with those with the pulley released. Tendon gliding resistance was significantly increased with preservation of the pulley on postsurgical days 3, 5, 7, and 14; these toes required a greater number of motion cycles to reach steady levels of resistance and showed significantly higher steady resistance after digital motion.

Release of the A2 pulley decreases the rate of repair rupture and the resistance to tendon gliding when the site of tendon repair has to glide through the pulley in the early postsurgical period. The findings of this study support partial release of the A2 pulley to favor successful tendon repair.