A new intramedullary sustained dynamic compression nail for the treatment of long bone fractures: a biomechanical study

Abstract

Objectives: We developed a new intramedullary interlocking nail (sustained dynamic compressive nail; SDCN) which can sustain a continuous dynamic compressive force on the fracture edges to overcome implant failure, screw loosening and nonunion complications encountered in the traditionally used static intramedullary nailing (SIMN). Materials and methods: Six pairs of composite femurs were fixed with SIMN and SDCN. The axial compression, bending, torsional stiffness, and strain values were analyzed.
Results: The mean axial compression stiffness values were 427.1 N/mm for the SDCN and 217.8 N/mm for SIMN, indicating a statistically significant difference (p=0.006). The mean stiffness values of rotation were 1.42 Nm/° for the SDCN and 0.89 Nm/° for SIMN. Anteroposterior bending tests were carried out. The mean results of stiffness were measured as 218 N/mm for the SDCN and 182.7 N/mm for the SIMN. The mean strain measurements in compression were 2454.5 µ-strain for the SDCN and 1123.8 µ-strain for the SIMN.
Conclusion: Biomechanically, the intramedullary SDCN is more stable than the SIMN system and it provides good abutment of the nail to the bone. Also, SDCN increases the stability by producing continuous compression and increasing the contact pressure of the fracture ends.