Table 2.
The interpedicular travel (IPT) and interpedicular displacement (ID) of DTO and Isobar at transition segment were evaluated by calculating scale difference.
| Load condition | Device | IPT | ID | ||||||
|---|---|---|---|---|---|---|---|---|---|
| A (mm) | B (mm) | B/A | P value | C (mm) | D (mm) | D/C | P value | ||
| Axial load | DTO | 0.17 ± 0.10 | 0.20 ± 0.07 | 1.18 | 0.28 | −0.01 ± 0.03 | −0.07 ± 0.05 | 7 | <0.001 |
| Isobar | 0.95 ± 0.07 | 0.58 ± 0.23 | 0.61 | <0.001 | 0.10 ± 0.07 | 0.02 ± 0.05 | 0.20 | 0.02 | |
| Axial+flexion | DTO | 0.14 ± 0.05 | 0.18 ± 0.10 | 1.29 | 0.18 | −0.01 ± 0.05 | −0.04 ± 0.02 | 4 | 0.13 |
| Isobar | 0.84 ± 0.07 | 0.75 ± 0.06 | 0.87 | 0.01 | 0.45 ± 0.11 | 0.11 ± 0.06 | 0.24 | <0.001 | |
| Axial+bending (stretching side) | DTO | 0.52 ± 0.10 | 0.47 ± 0.04 | 0.90 | 0.21 | 0.07 ± 0.02 | 0.11 ± 0.01 | 1.57 | 0.01 |
| Isobar | 1.00 ± 0.06 | 0.80 ± 0.06 | 0.80 | 0.01 | 0.25 ± 0.06 | 0.25 ± 0.03 | 1.00 | 0.43 | |
| Axial+bending (contraction side) | DTO | 0.66 ± 0.12 | 0.63 ± 0.09 | 0.95 | 0.36 | −0.38 ± 0.04 | −0.44 ± 0.01 | 1.16 | 0.02 |
| Isobar | 1.02 ± 0.08 | 0.51 ± 0.09 | 0.50 | <0.001 | −0.22 ± 0.06 | −0.06 ± 0.02 | 0.27 | <0.001 | |
Note: the stiffness of 600 N/mm (A and C) and 1100 N/mm (B and D), respectively, were used to simulate different grades of mild degeneration at L3/4. The stiffness of 1600 N/mm was used to stimulate moderate degeneration at L4/5 for all models in the mean time.