What makes vertical femoral neck fracture with posterior inferior comminution different? An analysis of biomechanical features and optimal internal fixation strategy.

Posterior-inferior comminution primarily increases superior-middle detached interfragmentary movement in VFNF, which results in varus deformation. For comminuted VFNF with or without osteoporosis, alpha fixation has the best interfragmentary stability and anti-shear property among six current mainstream fixation strategies, but a relatively weaker stiffness and anti-varus property compared to fixed-angle devices. FNS is advantageous owing to stiffness, anti-varus property and bone yielding rate in osteoporosis cases, but is insufficient in anti-shear property.