Figure 1.
The different kinds of pedicle screws used in this study.
“a” is the conventional pedicle screw (CPS). “b” is the component elements of expansive pedicle screw (EPS), including EPS, bolt, rod and nut. “c” is the expanding EPS, which was achieved through inserting the bolt into the interior of EPS, pressing the rod onto end of the bolt and tightening the nut into the end of screw.
Figure 2.
The load-displacement curve in the axial pullout test.
On the curve, the maximum pullout strength (Fmax) was defined as the inflection point where the load peaked and then sharply decreased with the increasing displacement and energy absorbed to failure was determined as the area under the curve before the onset of failure point.
Figure 3.
ROI of anterior part of screw.
Left was CPS and right was EPS. ROI indicates regions of interest.
Table 1.
BMD of lumbar vertebrae pre-induction and post-induction (n = 8, means ± SD).
Table 2.
Results in axial pullout tests in three groups (n = 8, means ± SD).
Figure 4.
Three-dimension micro-CT reconstruction of interface between bone and screw in three groups at 6-week.
“a”, “b” and “c” indicate CPS group, PMMA-PS group and EPS group, respectively. Brown color, blue color and white color represent bone tissue, screw and PMMA, respectively. (Resolution 21 µm, 2048×2048).
Figure 5.
Three-dimension micro-CT reconstruction of interface between bone and screw in three groups at 12-week.
“a”, “b” and “c” indicate CPS group, PMMA-PS group and EPS group, respectively. Brown color, blue color and white color represent bone tissue, screw and PMMA, respectively. (Resolution 21 µm, 2048×2048).
Table 3.
Three dimensional parameters of RIO in CPS and EPS groups (n = 8, means ± SD).
Figure 6.
Histological observations of interface between bone and screw in three groups at 6-week and 12-week.
“a”, “b” and “c” indicate CPS group, PMMA-PS group and EPS group, respectively. “1″ and “2″ indicate16 and 50 times magnification in microscope, respectively. Red color and saffron yellow color represent mature bone trabeculae and fibrous tissue, respectively. Round black and irregularly-shaped black colors represent screw and PMMA, respectively.