A self-guided screwdriver for cannulated screws: its design, mechanical tests and clinical application

Abstract

Objective To present a self-designed self-guided driver for clinical removal of cannulated screws. Methods The diameter of the selfguided rod is 2.8 mm and its length is 50 mm.The hexagonal driver head is 4 mm in height,2 mm in width and 5 mm in length.The other parts are similar to those of a solid driver.We then tested the stabilization of the selfdesigned driver by measuring the lateral load and displacement in 5 different experimental groups.Next we put it into use in the 26 patients who had been treated in our department from July 2008 to July 2009.They had been divided into 2 groups randomly.In the self-guided group,there were 9 males and 4 females,with an average age of 36 years and an interval of 30 months after the first operation.In the solid driver group.there were 7 males and 6 females.with an average age of 43 years and an interval of 21 months after the first operation. Results The mechanical tests revealed that the instrument designed by us was stable and could prevent lateral displacement.In clinic.the 39 screws were removed saccessfully in the self-guide driver group.The mean surgical time and incision in the self-guided driver group were significantly less and smaller than in the solid driver group.Conclnsions The self-guided driver is as stiff as a common solid driver and as stable as a cannulated driver.It can reduce the likelihood of screw invalidation which may make the operation very difficult and timeconsuming.It is a simple,timesaving,and less traumatic instrument,especially fit for removal of cannulated screws of the femoral neck. Key words: Bone nails; Device removal; Femoral neck fractures; Driver