BIODEGRADABLE INTERFERENCE SCREW FIXATION EXHIBITS PULL-OUT FORCE ANDSTIFFNESS SIMILAR TO TITANIUM SCREWS

Recently, increased interest in biodegradable interference screws for bone-tendon-bone graft fixation has led to numerous screws becoming av ailable. The implants are made from different polymers and have differ ent designs, which might influence their mechanical properties. Severa l studies have reported a wide range of mechanical results for these s crews using different biomechanical models, The aim of the present stu dy is to compare reliable biomechanical data for six different biodegr adable interference screws, consisting of five different polymers, wit h a conventional titanium screw in a standardized model, Seventy proxi mal calf tibias were used to determine maximal pull-out force, stiffne ss of fixation, and insertion torque for interference screw fixation o f bone-tendon-bone grafts, Additionally, maximal torque at failure was determined, Data were analyzed with respect to aspects of screw desig n, such as drive and thread shape. Five of the six biodegradable screw s provided initial pull-out force and stiffness of fixation comparable with that of a conventional titanium screw, Torque at failure can be greatly increased by adapting the drive design to the mechanical prope rties of the polymeric raw material, A correlation between pull-out fo rce and thread height indicates that fixation rigidity depends on scre w design, even in a biodegradable implant.