The effect of Kurosaka screw divergence on the holding strength of bone-tendon-bone grafts.

Fresh-frozen porcine knees were used to demonstrate the effects of diverging Kurosaka screw placement on linear load to failure in simulated anterior cruciate ligament reconstructions. Screws, placed anteromedially (rear-entry or tibial type) or intraarticularly (endoscopic femoral type) into each tibia, were directed at 0 degree, 15 degrees, or 30 degrees 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 divergence. Overall, the difference in pullout strength between rear-entry (or tibial side) and endoscopic femoral type fixation was shown to be statistically significant (P < 0.001). Anteromedially placed screws showed a statistically significant decrease in holding strength at 15 degrees and 30 degrees compared with 0 degree of divergence (P < 0.05). Intraarticular screw placement resulted in a statistically significant decrease in holding strength only at 30 degrees of divergence (P < 0.05). This study supports the importance 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.