BIOMECHANICAL EVALUATION OF POLYLACTIDE ABSORBABLE SCREWS USED FOR SYNDESMOSIS INJURY REPAIR

Simulated syndesmosis injuries were created in 12 fresh-frozen, below- knee cadaver specimens. Six specimens were repaired with a 4.5 mm stai nless steel screw, and six were repaired with a 4.5 mm polylactide scr ew. Three specimens of each group were tested in load to failure by ax ially loading with 1400 N and externally rotating to 90 degrees. Three specimens in each group underwent fatigue testing by axially loading with 700 N and applying 2.5 N-m of torque for 57,700 cycles. Radiograp hs and computed tomography scans were evaluated. None of the screws br oke or failed. Similar load to failure was noted in polylactide and co ntrol groups. Fatigue testing revealed no significant change in stiffn ess. No significant screw damage was evident on radiographic or comput ed tomography evaluation. The data suggest that a polylactide screw ha s sufficient fatigue and failure strength to allow for healing of this injury in a clinical situation.