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Sliding Hip Screws: Low Plate Angle

- Discussion:
    - device that is placed at lower angle has less force working parallel to sliding axis & more force working perpendicular to sliding axis.
            - this perpendicular force acts to jam or bend the device, thereby preventing impaction.
    - device that is placed at lower angle may be used effectively in Stable Frx because controlled collapse is not important for impaction of the fracture and early weight-bearing;
    - 130 deg plate
            - bent w/ loading, resulting in jamming of nail in 2/6 of cases with unstable fractures;
            - as compared to higher angled plates, 130 deg plates showed highest tensile forces;
            - conclusion is that, in most cases 135 or 140 deg plate should be used;
    - 135 deg plate:
         - 135 deg plates are indicated for most patients - for anatomic reduction;
         - easier to insert in desired central position of femoral head;
         - insertion point is in metaphyseal bone, which produces less of stress riser effect than diaphyseal insertion point required for 150 deg devices;
         - nail entry site is directly opposite lesser trochanter;
    - 140 deg plates:
         - have lowest plate tensile forces

A biomechanical analysis of the sliding hip screw: the question of plate angle.