The tendons run through a tight sheath and work in a very similar way to brake-cables on a bicycle. The tendons are commonly cut in accidents. The ends can joined and stitched in the month after injury. Sometimes, however, the repairs fail or it is not realised that the tendon has been cut. This ability can only be recovered if the tendon is reconstructed.
Reconstruction is complicated and requires two operations.
The damaged tendon is removed and a soft silicone rod is passed along the length of the sheath. This remains in place for about ten weeks. During this time, a new lining forms around the rod. This will both nourish and allow movement of the tendon graft. This operation involves a long zigzag incision from finger tip into the palm.