Biomechanical comparison of proximal interlocking screw constructs in different subtrochanteric fracture models

Background: Depending on the size of the proximal bone segment, either a standard locking construct or a recon locking construct can be used in intramedullary nailing for a subtrochanteric fracture. However, the most appropriate construct for a given size of proximal bone segment has not yet been determined. Therefore, this study aimed to identify the appropriate construct using biomechanical testing. Methods: Fourteen intramedullary nails for each locking construct (standard and recon) were inserted into 28 synthetic femurs. Fourteen subtrochanteric fracture models were developed by creating parallel defects (2 cm in size) 2 cm distal to the lower edge of the lesser trochanter (low fracture group), and 14 fracture models were developed with identical defects situated 1 cm distal to the lower edge of the lesser trochanter (high fracture group). An axial load experiment was conducted to measure the stiffness and failure load for each proximal interlocking screw construct. Results: There were no statistically significant differences in the stiffness and failure load between the locking constructs in the low fracture group. However, the stiffness and failure load were significantly greater for the recon locking construct than for the standard locking construct in the high fracture group. Conclusion: The standard locking system allows for sufficient fixation strength when performing intramedullary nailing for subtrochanteric fractures located 2 cm distal to the lower edge of the lesser trochanter.