Intramedullary fixation of unstable intertrochanteric XXXX : one or two lag screws.

@entity1 @entity2003 @entity173 @entity27376 @entity7443
OBJECTIVE: To compare the screw sliding characteristics and biomechanical stability of four-part intertrochanteric @entity173 stabilized with an intramedullary nail using either one large-diameter lag screw (intramedullary hip screw [IMHS]; Smith _ Nephew, Memphis, @entity7443 ) or two small-diameter lag screws (trochanteric antegrade nail [ @entity27376 ]; Smith _ Nephew, Memphis, @entity7443 ). DESIGN: Laboratory investigation using eight matched pairs of cadaveric @entity1 femurs with simulated, unstable intertrochanteric @entity173 . INTERVENTION: One femur of each matched pair was stabilized with an IMHS intramedullary nail, and the other was stabilized with a @entity27376 intramedullary nail. Femurs were statically, then cyclically loaded on a servohydraulic materials testing machine. Finally, all specimens were loaded to failure. MAIN OUTCOME MEASURES: Screw sliding and inferior and lateral head displacements were measured for applied static loads from 500N to 1250N. The same measurements were obtained before and after cyclically loading the specimens at 1250N. Ultimate failure strength of the implant constructs also was determined. RESULTS: There was no significant difference between the @entity27376 and IMHS in static or cyclical loading with respect to screw sliding or inferior and lateral head displacements. There was a statistically significant difference (P < 0.02) in failure strength, with the IMHS construct failing at an average of 2162N and the @entity27376 construct failing at an average of 3238N. CONCLUSION: The two constructs showed equivalent @entity2003 and stability in all parameters assessed in elastic and cyclical tests. The @entity27376 had a greater ultimate failure load.
