Effect of anchor threads on the pullout strength: A biomechanical study.

Pullout tests to determine the effect of anchor threads on the pullout strength was conducted by using universal testing machine, synthetic cancellous bone and thread-less metallic anchor. Anchors were inserted at 45°, 90° or 135° from the surface and they were pulled at 45° from the surface. The maximum load to failure was compared among the 3 insertion angles. Pullout strength of the anchors inserted at 45° was significantly greater than those inserted at 90° or 135°. Pullout strength of the thread-less anchor was the greatest when it was inserted at 45° to the bone surface. LEVEL OF EVIDENCE: level II.