A mechanical comparison of subtrochanteric femur fracture fixation.
OBJECTIVE
To determine whether the mechanical properties of first-generation interlocking femoral nails are different from those of second-generation interlocking femoral nails in a subtrochanteric femur fracture model.


METHODS
Randomized laboratory investigation using a synthetic subtrochanteric femur fracture model.


METHODS
Simulated stable and unstable fractures were created at three levels in the subtrochanteric region of synthetic femora. Instrumented specimens were tested elastically in a biomaterials testing system.


METHODS
Synthetic femora were instrumented with either a statically locked first-generation femoral nail or a statically locked second-generation femoral nail.


METHODS
Elastic stiffness for both the stable and unstable fracture groups was measured in both compression and torsion. Unstable fracture specimens were tested to failure in compression, and load to failure was measured.


RESULTS
Throughout the subtrochanteric region, second-generation femoral nail constructs were consistently stiffer in compression and torsion than were statically locked first-generation femoral nail constructs. In general, second-generation constructs also withstood larger loads to failure in the unstable fracture model.


CONCLUSIONS
Second-generation nails provided significantly enhanced mechanical stiffness compared with first-generation femoral nails when used to treat both stable and unstable subtrochanteric femur fractures. Although these results were obtained by using a well-controlled, mechanically consistent model, clinical validation of an increased incidence of fracture unions or of decreased time to union is required before we can recommend that second-generation nails be used routinely to treat subtrochantenic femur fractures.
Department of Surgery, University of Kentucky Chandler Medical Center, Lexington, USA.
K J
KJ
Pugh
R A
RA
Morgan
J T
JT
Gorczyca
D
D
Pienkowski
D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D001858:Bone Nails; D005264:Femoral Fractures / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D011446:Prospective Studies; D011897:Random Allocation