Biomechanical analysis of recently released cephalomedullary nails for trochanteric femoral fracture fixation in a human cadaveric model

Background Recently, two novel concepts for intramedullary nailing of trochanteric fractures using a helical blade or interlocking dual screws have demonstrated advantages as compared to standard single-screw systems. However, these two concepts have not been subjected to a direct biomechanical comparison so far. The aims of this study were to investigate in a human cadaveric model with low bone quality (1) the biomechanical competence of nailing with the use of a helical blade versus interlocking screws, and (2) the effect of cement augmentation on the fixation strength of the helical blade. Methods Twelve osteoporotic and osteopenic human cadaveric femoral pairs were assigned for pairwise implantation using either a short TFN-ADVANCED Proximal Femoral Nailing System (TFNA) with a helical blade head element or a short TRIGEN INTERTAN Intertrochanteric Antegrade Nail (InterTAN) with interlocking screws. Six osteoporotic femora, implanted with TFNA, were augmented with bone cement. Four groups were created: group 1 (TFNA) paired with group 2 (InterTAN), both consisting of osteopenic specimens, and group 3 (TFNA augmented) paired with group 4 (InterTAN), both consisting of osteoporotic specimens. An unstable trochanteric AO/OTA 31-A2.2 fracture was simulated and all specimens were tested until failure under progressively increasing cyclic loading. Results Stiffness in group 3 was significantly higher versus group 4, p = 0.03. Varus (degrees) and femoral head rotation around the femoral neck axis (degrees) after 10,000 cycles were 1.9 +/- 1.0/0.3 +/- 0.2 in group 1, 2.2 +/- 0.7/0.7 +/- 0.4 in group 2, 1.5 +/- 1.3/0.3 +/- 0.2 in group 3 and 3.5 +/- 2.8/0.9 +/- 0.6 in group 4, being significantly different between groups 3 and 4, p = 0.04. Cycles to failure and failure load (N) at 5 degrees varus or 10 degrees femoral head rotation around the neck axis in groups 1-4 were 21,428 +/- 6020/1571.4 +/- 301.0, 20,611 +/- 7453/1530.6 +/- 372.7, 21,739 +/- 4248/1587.0 +/- 212.4 and 18,622 +/- 6733/1431.1 +/- 336.7, being significantly different between groups 3 and 4, p = 0.04. Conclusions Nailing of trochanteric femoral fractures with use of helical blades is comparable to interlocking dual screws fixation in femoral head fragments with low bone quality. Bone cement augmentation of helical blades provides significantly greater fixation strength compared to interlocking screws constructs.

Automated summary

In a study using a cadaveric model with low bone quality, nailing trochanteric femoral fractures with helical blades showed similar fixation strength to interlocking dual screws, with significantly greater strength when augmented with bone cement.