The invention relates to a tissue anchor which is an open helix of biocompatible material having a slope of from 0.5 to 10 turns per centimeter, a length from 3 to 75 millimeters, a diameter of from 1.5 to 11 millimeters, and an aspect ratio of from about 3 to about 5 to 1. The anchor can have a head which is capable of securing or clamping tissue together, such as holding a suture to secure a ligament or tendon to bone. The anchor can also have a head which causes an inward, compressive loading for use in fastening bone to bone, orthopedic plates to bone, or cartilage to bone. The head may be an integral member and may include a self-reinforcing wedge which joins the helix to the head. Further, the elongate member, or filament that forms the helix may have a tapering diameter along its length.