The deadman theory of suture anchors: observations along a south Texas fence line.

Suture anchors are being increasingly reported as a means of fixation of torn rotator cuff tendons to bone. The author has developed a mechanical model for the suture anchor-rotator cuff construct based on an analogy to the deadman system used to stabilize a corner fence post. Using this model, one can demonstrate a mechanically favorable angle of insertion of the suture anchor (theta 1) such that the anchor's pullout strength is increased at low angles of theta 1. In addition, the angle that the suture makes with the direction of pull of the rotator cuff (theta 2) has a direct effect on tension in the suture. A low angle of theta 2 minimizes the total tension in the suture, thereby minimizing the chance of suture breakage.