Article Figures & Data
Figures
- Fig. 1
Articulating PEEK nucleus replacement used in this study.
- Fig. 2
Radiographic image of trial spacer for sizing of the nucleus implant in (A) AP and (B) lateral views.
- Fig. 3
Biomechanical test setup of an example test specimen in left lateral bending before fatigue test protocol.
- Fig. 4
Macroscopic cross-section of the intervertebral disc following fatigue testing of 100(k) cycles for (A) an intact, untreated disc and (B) an implanted disc.
- Fig. 5
Mean loss in disc height (mm) at peak compressive load for the 3 disc conditions.
- Fig. 6
CT slice of an L1 vertebra. There are superior and inferior endplate fractures (shown by red arrows), all of which are likely to be chronic given the intact cortex. Notice the small osteophytes (yellow arrow) at the inferior endplate. A 3D reconstruction (not shown) confirmed these observations.
- Fig. 7
CT slice of a L1 vertebra. Fracture of the endplate (shown by red arrow) at the control level.
Tables
Specimen Gender Age BMD (g/cm3) Disc depth (cm) Disc width (cm) Disc area (cm2) Percenatge of implant/disc area 7761 (T12-L2) M 54 1.538 4.11 5.43 17.84 10.65 7761 (L3-5) M 54 1.538 4.07 6.37 20.02 9.49 7827 (T12-L2) M 58 0.786 3.79 5.21 15.53 15.52 7827 (L3-5) M 58 0.786 3.98 5.36 17.57 13.72 7760 (T12-L2) M 65 0.919 3.73 5.45 16.99 14.18 7760 (L3-5) M 65 0.919 3.74 5.43 16.51 14.60 Mean 59 1.081 3.90 5.54 17.41 13.03 St. dev. 5 0.359 0.17 0.42 1.52 2.39 Abbreviations: BMD, bone mineral density; St. dev., standard deviation.
Mode Intact Discectomy Implant Left torsion 2.46 ± 0.54 2.75 ± 0.29 2.62 ± 0.42 Right torsion 2.50 ± 0.51 2.80 ± 0.27 2.61 ± 0.38 - Table 3
Mean ROM values (degrees) for the sagittal and coronal bending test modes in the conditions tested
Mode Level Intact Discectomy Implant Flexion Control
Surgical3.59 ± 0.61
3.51 ± 0.803.67 ± 0.54
4.55 ± 1.573.42 ± 0.60
4.07 ± 1.66Extension Control
Surgical2.44 ± 1.17
2.77 ± 1.142.34 ± 1.14
1.80 ± 0.81*2.33 ± 1.28
2.59 ± 0.98Left bend Control
Surgical2.73 ± 0.70
3.42 ± 0.992.67 ± 0.69
3.35 ± 1.212.71 ± 0.68
3.04 ± 1.11Right bend Control
Surgical2.64 ± 0.74
3.20 ± 0.952.65 ± 0.79
3.49 ± 1.092.64 ± 0.80
3.78 ± 1.46↵* Denotes significant difference (P < .05) from intact.
- Table 4
Mean stiffness values for the pure compression and torsion test modes in the conditions tested
Mode Intact Discectomy Implant Pure comp (N/mm) 1485 ± 229 1364 ± 235 1362 ± 241 Left torsion (Nmm/degree) 4056 ± 600 3610 ± 425 3848 ± 316 Right torsion (Nmm/degree) 3696 ± 493 3259 ± 243 3518 ± 278 - Table 5
Mean stiffness values (N = 6) for the sagittal and coronal bending test modes (Nmm/degree)
Mode Level Intact Discectomy Implant Flexion Control
Surgical4168 ± 566
4785 ± 14373804 ± 360
4817 ± 12204034 ± 627
4911 ± 1432Extension Control
Surgical6032 ± 2148
4759 ± 24416754 ± 2220
8925 ± 5397*5983 ± 1640
5904 ± 2632Left bend Control
Surgical4557 ± 1214
3566 ± 8694578 ± 1294
4191 ± 10984522 ± 1283
4594 ± 1092Right bend Control
Surgical4764 ± 1658
3923 ± 12604738 ± 1720
4310 ± 11504731 ± 1711
4006 ± 1097↵* Denotes significant difference (P < .05) from intact.
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