Effect of hydrogel injection on the biomechanical behaviour of herniated discs
Citation for published version (APA):
Barthelemy, V. M. P., van Esterik, F. A. S., Petterson, R., Papen-Botterhuis, N. E., Craenmehr, E. G. M., & Ito, K. (2012). Effect of hydrogel injection on the biomechanical behaviour of herniated discs. Poster session presented at Mate Poster Award 2012 : 17th Annual Poster Contest.
Document status and date: Published: 01/01/2012 Document Version:
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Aim: Evaluate a thermo-responsive hydrogel with similar dynamic and Young’s modulus to NP tissue (Craenmehr, 2009).
Hypothesis: By replacing the herniated NP (HNP) volume
with a material of similar mechanical properties, the biomechanical characteristics of the intervertebral disc would be restored.
Methods
Reproducible ex-vivo bovine disc herniation model
Herniated discs were created by stabbing the full depth of the annulus with a scalpel, and then applying a cyclic compression in a flexed position (Fig. 2) (Adams, 1985).
To simulate treatment, 2 groups:
- hydrogel injected in the nucleus (n=6) - HNP tissue reinserted (n=3)
In both cases, the annulus was glued and sutured.
Mechanical test: Disc axial displacements were measured
under creep loading for the three disc conditions: healthy, herniated and treated (Fig. 3).
Introduction
Hydrogel-based nucleus pulposus (NP) replenishment is a promising treatment to restore the decreased NP volume in herniated discs (Fig. 1) (Kurtz, 2006).
Effect of hydrogel injection on the
biomechanical behaviour of herniated discs
V. Barthelemy, F. van Esterik, R. Petterson, N. Papen-Botterhuis (TNO), E. Craenmehr (TNO), K. Ito
/ Department of Biomedical Engineering
References
Adams et al, Spine, 10:524-531, 1985. Craenmehr et al, WO2009131454, 2009.
Kurtz et al, Spine Technology Handbook, 2006.
Results
Healthy, herniated, hydrogel injected and NP reinserted discs, showed similar creep responses, whereas the initial strain for herniated and hydrogel injected discs were significantly different (p < 0.05) from healthy discs (Fig.4).
However, no significant differences were observed between herniated and hydrogel conditions as well as between herniated and reinserted discs (Fig. 4).
Discussion
The creep testing showed no improvement of the biomechanical properties neither in hydrogel injected or HNP reinserted discs. It appears that the axial biomechanical properties of the herniated SMSs were dominated by a defect other than that of HNP tissue volume loss. Although the annular defect was sutured and glued, this appears to be insufficient.
Conclusion
Thus, in this model NP replenishment alone could not restore the healthy axial disc behaviour, and the development of better annular repair methods are encouraged.
Orthopaedic Biomechanics
Fig. 4 Initial strain and creep strain for healthy, herniated and hydrogel injected disc (n=6, left) or NP reinserted disc (n=3, right), * p < 0.05.
-0.35 -0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.00
Initial loading Creep
St ra in Healthy Herniated treated -0.35 -0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.00
Initial loading Creep
Stra in Healthy Herniated treated * *
Fig. 2 Left: Stab incision of the annulus;
Right: Apparatus used to apply cyclic
compression in a flexed angle (adapted from Adams 1985).
Fig. 3. Left: Loading protocol, right: Typical displacement curve.
PBS Nucleus pulposus Annulus fibrosus Herniation of Nucleus pulposus
Compressed nerve root AF defect
Fig. 1. Herniated intervertebral disc.
-1 -0.5 0 0 20 40 60 80 100 Co mpre ssiv e load Time (min)
(MPa) Initial loading
