[The dependence of the removal torque of a leg screw a screw surface and implantation time (author's transl)].

The experiment was performed on 17 sheep tibiae in vivo. 4.5 mm ASIF leg screws with a constant insertion torque (68.6 Ncm) but different surfaces (smooth or rough) were removed after 3 s, 7, 28, 56 and 112 days after insertion. The screws with a rough surface which were implanted for 28 days and longer exhibited a significantly greater removal torque. For instance rough screws which were implanted for 112 days displayed a removal torque eight times greater than after 3 s.