Relationship of mechanical factors to the strength of proximal femur fractures fixed with cancellous screws.

摘要: The decision of whether to attempt screw fixation a femoral neck fracture is based partly on the estimated strength fixed bone/implant construct in relation loads it will be required bear. goal this study was determine vitro following biomechanical factors internally fractures subjected cyclic and failure loading: (a) square density cancellous bone head, (b) percent comminution inferior surface, (c) moment arm joint force, or distance from axis force (d) orientation angle surface medial/lateral plane relative shaft. Femoral were created each 38 fresh cadaveric proximal femora using dropweight with materials testing machine. After sustaining displaced fracture, achieved three cannulated screws. femur then 10,000 cycles sinusoidially varying load acting parallel shaft, an initial peak magnitude 2.2 times body weight, while hip flexed, extended, rotated mimic some motions gait. Muscle loading not simulated. decreased as head during cycling. mean for cycle over duration test defined average load. Following cycling, bone/screw loaded same direction, measurement termed maximum Average correlated four multiple regression analysis. These high degree (R2 = 0.771; p < 0.0001) lesser but still significant 0.458; 0.012), demonstrating that they can used estimate under these conditions. strongest correlation (p 0.005) length 0.072).