The Effect of Kurosaka Screw Divergence on the Holding Strength of Bone-Tendon-Bone Grafts

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Abstract
Fresh-frozen porcine knees were used to demonstrate the effects of diverging Kurosaka screw placement on linear load to failure in simulated anterior cruciate liga ment reconstructions. Screws, placed anteromedially (rear-entry or tibial type) or intraarticularly (endoscopic femoral type) into each tibia, were directed at 0°, 15°, or 30° divergence angles relative to a guide wire. Grafts were axially loaded to failure to determine holding strength. Hierarchical analysis of variance was used to analyze differences between tibial side and endoscopic femoral type screw placement and the angles of diver gence. Overall, the difference in pullout strength be tween rear-entry (or tibial side) and endoscopic femoral type fixation was shown to be statistically significant (P < 0.001). Anteromedially placed screws showed a sta tistically significant decrease in holding strength at 15° and 30° compared with 0° of divergence (P < 0.05). Intraarticular screw placement resulted in a statistically significant decrease in holding strength only at 30° of divergence (P < 0.05). This study supports the impor tance of accurate screw placement within the tibia to ensure optimal interference fixation and suggests that endoscopic screw placement may offer significant added security when there are minor degrees of divergence.