The double sheath system and tendon gliding in zone 2C

Area of Science:

• Hand surgery
• Anatomy
• Biomechanics

Background:

• Zone 2C of the flexor tendon sheath presents unique anatomical challenges.
• The flexor digitorum superficialis (FDS) tendon acts as a secondary sheath for the flexor digitorum profundus (FDP) tendon in zone 2C.
• This anatomical arrangement contributes to suboptimal outcomes in FDP tendon repairs within zone 2C.

Purpose of the Study:

• To investigate the anatomical characteristics of zone 2C.
• To evaluate the effect of A2 pulley modification on tendon gliding and finger range of motion.
• To determine the feasibility of A2 pulley intervention for improving tendon repair outcomes in zone 2C.

Main Methods:

• Anatomical dissection of 40 fingers from ten preserved cadaver hands.
• Assessment of tendon gliding amplitude and finger range of motion after sheath incision.
• Evaluation of the impact of partial A2 pulley incision on sheath integrity and strength.

Main Results:

• The FDS tendon functionally envelops the FDP tendon in zone 2C, forming a "double sheath" system.
• Tendon repairs in zone 2C glide into zone 2D, highlighting the importance of the zone 2D gliding tunnel.
• Partial or enlarged A2 pulley incision did not significantly affect the range of motion or markedly decrease overall sheath strength.

Conclusions:

• The "double sheath" in zone 2C complicates flexor tendon repair.
• The gliding tunnel of zone 2D is crucial for successful tendon repair in zone 2C.
• Partial A2 pulley modification is a viable option for tendon repairs in zone 2C without compromising functional mechanics.