TheeffectofstressdistributionduetothechangesofthedistalscrewalignmentinrelationtotheGammanailandthefemoralshaftisthoroughlystudiedinthispaper.FailureoftheGammanailcompositeoccursthroughthecranialapertureofthedistalscrewsandtheinsertionholeforthelagscrewduetononunion,delayed-unionandcontinuedweight-bearing.Athree-dimensionalfiniteelementmodelwasusedtostudythefracturedfemur,theGammanail,thelagscrewandthedistallockingscrews.ThefirstandtheseconddistalscrewswereinsertedintotheGammanailinfourdifferentconfigurations.WefoundthatthestressoftheGammanailcompositewassubstantiallyreducedwiththetwoscrewsconfiguredintheanteriortoposteriordirection.Thisalignmentcanbeargreaterloadinginthemoredemandingfracturetypes.Inthesubtrochantericfractureorthecomminutedfracturesattheproximalfemur,theoptimalalignmentofthetwodistalscrewswasintheanteriortoposteriordirection.
