This cadaveric biomechanical study tested the new femoral neck system (FNS) against established fixation methods for unstable femoral neck fractures. It compared FNS to DHS with antirotation screw, DHS-blade, and three cannulated screws in a Pauwels III model. The question: can a minimally invasive single-bolt implant match the stability of bulkier DHS constructs?
When you face an unstable vertical (Pauwels III) femoral neck fracture, the construct choice matters more than for stable patterns because of the high shear across the fracture line. This study shows three cannulated screws fail at roughly half the load of an angular-stable device and migrate six times as much. That is the biomechanical reason 3CS struggle with vertical fractures.
The practical takeaway: the new FNS gives you DHS-level stability through a smaller, minimally invasive approach that preserves more femoral head bone. It is a valid alternative when you want a sliding angular-stable construct.
One caveat for boards and the OR: the DHS-screw showed the least varus tilting, because parallel screws give two-point fixation while the FNS bolt and screw converge to one point. Whether that small difference matters clinically is still unproven. Remember this is a cadaveric model with no soft tissue and excludes severe osteoporosis, so it speaks to mechanics, not healing or AVN.
This cadaveric biomechanical study tested the new femoral neck system (FNS) against established fixation methods for unstable femoral neck fractures. It compared FNS to DHS with antirotation screw, DHS-blade, and three cannulated screws in a Pauwels III model. The question: can a minimally invasive single-bolt implant match the stability of bulkier DHS constructs?
When you face an unstable vertical (Pauwels III) femoral neck fracture, the construct choice matters more than for stable patterns because of the high shear across the fracture line. This study shows three cannulated screws fail at roughly half the load of an angular-stable device and migrate six times as much. That is the biomechanical reason 3CS struggle with vertical fractures.
The practical takeaway: the new FNS gives you DHS-level stability through a smaller, minimally invasive approach that preserves more femoral head bone. It is a valid alternative when you want a sliding angular-stable construct.
One caveat for boards and the OR: the DHS-screw showed the least varus tilting, because parallel screws give two-point fixation while the FNS bolt and screw converge to one point. Whether that small difference matters clinically is still unproven. Remember this is a cadaveric model with no soft tissue and excludes severe osteoporosis, so it speaks to mechanics, not healing or AVN.