Abstract
The reduction for unstable femoral intertrochanteric fracture should be extramedullary, which means that the proximal fragment protrudes for the distal fragment. However, only few articles have compared extramedullary and intramedullary reductions in a biomechanical study. Thus, we created unstable femoral intertrochanteric fracture models using imitational bone (extramedullary and intramedullary groups, each with 12 cases) and evaluated their biomechanical stabilities. The fracture type was 31-A2 according to the AO-OTA Classification of Fractures and Dislocations and greatly lacked bone on the posterior side. We performed compression examination and evaluated stiffness. The implant used for fixation was TFNA (DePuy Synthes). We applied axial compression with 20 adduction in the standing position. Statistical analysis was performed using the Mann-Whitney U test. No significant difference in initial loading force was found between the two groups. However, the axial stiffness of the extramedullary bone showed a significant increase (p < 0.05) in high loading force (800–1000 N). This means that the stability of the extramedullary reduction was superior to that of the intramedullary reduction in terms of high loading force in the standing position. We suggest that antero-medial bony buttress is important for unstable femoral intertrochanteric fractures. These data indicate that extramedullary reduction and fixation for unstable femoral intertrochanteric fractures increase stability.
