Fig. 5

Side-by-side comparison of a representative screw movement in non-augmented (top) and augmented (bottom) samples with subsequent load change. Typical windshield wiper effect of both screw tips in the non-augmented sample until approx. 4000 cycles, when the screw tip loosens (left, right top); beyond 4000 cycles, a typical effect of increased load transfer by screw clamping (until dashed line) occurs within the right pedicle (right top); after approx. 10,000 cycles, the right tip increases again and a load transfer to the left screw follows until 12,000 cycles. Subsequently, the loosening increases for both sides until machine abort criterion are reached - displayed as absolute values