InSafeLock endopin versus conventional distal locking screws for femoral shaft fractures: A comparative laboratory biomechanical study

The InSafeLock femoral nail is a recently developed implant that uses endopin instead of screws in its distal locking mechanism. This study aimed to compare the biomechanical features of the distal locking mechanisms of InSafeLock and conventional nails. Twenty-four artificial femoral bones were used for mechanical tests. InSafeLock nails with endopin (Group 1) and conventional nails with distal locking screws (Group 2) were inserted into the artificial bones. The biomechanical features were evaluated using axial compression and rotational performance tests. There was no statistically significant difference between Group 1 and Group 2 in the axial compression displacement tests (P = .683). No visual damage was observed on the artificial bones or intramedullary nails after axial compression fatigue tests in either group. During axial compression failure testing performed after fatigue testing, the mean failure load of Group 1 was significantly lower than that of Group 2 (1132.5 ± 15.5 N vs 11,965.5 ± 9.5 N, respectively; P = .002). Rotational performance tests showed that the torsional yield strength of the groups was not statistically different (P = .333). While the InSafeLock endopin offers ease in distal locking, it exhibits a significantly lower failure load under high axial compression forces than conventional screws.