Metal and biodegradable interference screws: comparison of failure strength

The purpose of this laboratory investigation was to determine if there was any difference in the force required to pull out a patellar bone-tendon-bone graft from a femoral bone tunnel when secured by an interference screw of different materials, metal or biodegradable. The tibial end of the bone-tendon-bone graft was placed in the femoral tunnel. A 9-mm metal interference screw was used on the left side, and a 9-mm biodegradable screw was used on the right to secure the graft. Ultimate load to failure was determined by Instron testing. The average load before failure for the graft secured by the metal screw was 436 Newtons and for the biodegradable screw was 565 Newtons. A statistical significance was not demonstrated because there was wide range of loads between donor specimens, probably because of variations in bone density.