Zone II is a segment of anatomy in the hand from the mid-palm to the joint adjacent to the tip of the finger where the flexor tendons of each finger glide back and forth inside a tight segmental tunnel structure called the flexor tendon sheath, or pulley, system. The complexity of repairing a tendon in Zone II is alluded to by the name given to this area by hand surgeons, “no man’s land.”
In essence, a tendon is like a rope, woven of individual collagen fibers. As long as the tendon is inside the flexor tendon sheath and under some tension, the tendon is healthy. When a lacerated tendon retracts outside the pulley system (flexor tendon sheath), the tendon swells and frays, such that it may be very difficult to place it back into its sheath. Simultaneously, the empty flexor tendon sheath begins to contract, until after several weeks the sheath itself becomes practically obliterated.