Biomechanical comparison of Gamma3 and InterTan nails for stable and unstable intertrochanteric fractures

Abstract

Objective To compare the biomechanical properties of Gamma3 and InterTan nails in the fixation of femoral intertrochanteric fractures. Methods Twelve synthetic femora of 4th generation were randomized into 4 equal groups (n=3) for assessment of the 2 constructs of fracture fixation (Gamma3 versus InterTan nails). Groups A and B were made into models of stable femoral intertrochanteric fracture (AO/OTA type 31-A1.1) and groups C and D into unstable ones(AO/OTA type 31-A2.3). The biomechanical properties of Gamma3 and InterTan nails in the 4 models were tested and compared. Results For stable fracture models, the fracture gap movement increased with the increasing axial load and the torque increased with the increasing torsion angle. There were significant differences between groups A and B in fracture gap movement and torque (P 0.05). For unstable fracture models, there were no significant differences between groups C and D in fracture gap movement when the axial loads were 500 N, 600 N or 700 N (P >0.05), but there was a significant difference between the 2 groups when the axial load was larger than 800 N (P< 0.05). With the increasing torsion angle, the torque increased in groups C and D. There was a significant difference between the 2 groups in the torque at the same torsion angle (P< 0.05). There were a significant difference between groups C and D in failure load (2,781.5±600.6 N versus 3,150.5±633.8 N) (P=0.007). Conclusions For stable femoral intertrochanteric fractures, InterTan and Gamma3 nails may exhibit similar biomechanical properties. For unstable femoral intertrochanteric fractures, InterTan nails may provide obviously better biomechanical stability than Gamma3 nails. Key words: Hip fractures; Fracture fixation, intramedullary; Bone nails; Biomechanics