Biomechanical Comparison of INTERTAN Nail and Gamma3 Nail for Intertrochanteric Fractures

Abstract

Objective: To compare the biomechanical stabilities of Gamma3 nail and INTERTAN nail (ITN) for stable (AO/OTA 31A1.1) and unstable (AO/OTA 31A2.2) femoral intertrochanteric fracture. Methods: Twenty-four synthetic femora were randomly divided into four groups. After internal fixation (Gamma3 nail or ITN) had been implanted, stable and unstable intertrochanteric fracture models were produced. A cyclic testing protocol with increasing loads was performed for both stable and unstable intertrochanteric fracture models, and then torsional test and axial compression failure test were conducted. Stiffness, failure load, torque, and fragment displacement were recorded. Results: For stable fracture model: fragment displacement in ITN group were smaller than Gamma3 nail group (Gamma3 nail: 1.66 ± 0.13 mm; ITN: 1.55 ± 0.1 mm); stiffness (Gamma3 nail: 1142.6 ± 161.1 N/mm, ITN: 1159.3 ± 203.5 N/mm, P = 0.872) and failure load (Gamma3 nail: 5715.42 ± 616.34 N, ITN: 5690.27 ± 625.59 N, P = 0. 951) of the two nails were similar after cyclic test; torque of the ITN group was larger than the Gamma3 nail group. For unstable fracture model: fragment displacement in ITN group was significantly smaller than in the Gamma3 nail group when the axial load was larger than 800 N (Gamma3 nail: 3.59 ± 0.19 mm; ITN: 2.93 ± 0.28 mm); ITN group showed a significantly higher failure load than Gamma3 nail group (Gamma3 nail: 2942.77 ± 573.4 N, ITN: 3672.3 ± 790.5 N, P = 0. 011); torque was significantly higher for the ITN group compared to the Gamma3 nail group for three different angles. Conclusions: Both ITN and Gamma3 nail can maintain sufficient biomechanical stability for stable intertrochanteric fractures, but ITN was a better choice for unstable intertrochanteric fractures.