Biomechanical stability of short versus long proximal femoral nails in osteoporotic subtrochanteric A3 reverse-oblique femoral fractures: a cadaveric study

Abstract

Purpose Due to the demographic change towards an older society, osteoporosis-related proximal femur fractures are steadily increasing. Intramedullary nail osteosyntheses are available in different lengths, where the field of application overlaps. The aim of this study was to investigate whether subtrochanteric fractures can also be treated stably using a short femoral intramedullary nail in cadaveric bones. Methods A short PFNA and a long PFNA were implanted in both seven artificial bones and osteoporotic human specimens. A standardized AO 31-A3 (reverse-oblique) fracture was placed in the specimens with a lateral fracture spur 2 cm proximal to the distal locking screw (short PFNA) and embedded. The simulated iliotibial tract was preloaded to 50 N. The force was applied at 10 mm/min up to a force of 200–800 N (artificial bones) and 200–400 N (human specimens). The dislocation of the fracture gap, the axial bone stiffness of bone construct and the force curve of the tractus iliotibialis were measured. Results There is no difference in the use of a short versus long PFNA in terms of stiffness of the overall construct and only a slight increase in dislocation in the fracture gap results with short PFNA compared to a long intramedullary nail. Conclusion In summary of the available literature, the present study supports the thesis that there is no clinical difference between long versus short nails in A3 femur fractures. Furthermore, the present study defines a safe biomechanical range of fracture extension above the locking screw of the short intramedullary nail. Level of Evidence III

Failure of Fixation in Trochanteric Hip Fractures: Does Nail Design Matter?

“…27,31,43 Moreover, recent biomechanical evaluation of 31A3 fracture fixation comparing long and short nails found no clear superiority for long nails in fixation of these fracture patterns. 44,45 The indication and advantages of treating these fractures with long nails are still to be explored.…”

Biomechanical Comparison of Short-, Mid-, and Long-Length Proximal Femoral Nails for Femoral Intertrochanteric Fracture (AO/OTA 31A3.3) Fixation

“…Then, the femora were cyclically loaded up to 750 N (2000 cycles) with reference to the pressure settings of past cyclic tests on synthetic femur models. 12 , 13 The displacements in the machine axial direction at cycles 10-100, 100-500, 500-1000, 1000-1500, and 1500-2000 were determined through software calculations of actuator displacements during cycling. The translations of the actuator at cycles 100, 500, 1000, 1500, and 2000 were calculated and determined using software.…”

“…In our pilot study, we tried cyclic loading tests between 1000 and 2000 N, but the synthetic femur model broke, and we were unable to complete the testing. Therefore, we chose a cyclic load of 750 N with reference to the pressure settings of past cyclic tests on synthetic femur models, 12 , 13 and chose 2000 cycles according to the setting in a previous report that assumed the value in a sedentary patient with proximal femoral fracture. 8 …”

Research Progress of Surgical Treatment of Subtrochanteric Fracture of the Femur

“…It was also found that patients treated with short intramedullary nack for subtrochanteric fractures had a higher proportion of periprosthetic fractures. Linhart [19] 's biomechanical study of short and long intramedullary nails showed that there was no difference in overall structural stiffness between short and long PFnas, with increased fracture space displacement compared to long intramedullary nails. It has also been shown [20] that long-headed intramedullary nails with at least two distal locking screws are preferred for subtrochanteric fracture fixation; For high subtrochanteric fractures, short intramedullary nails are also a viable option.…”