Research Papers

Evaluation of an In Situ Gelable and Injectable Hydrogel Treatment to Preserve Human Disc Mechanical Function Undergoing Physiologic Cyclic Loading Followed by Hydrated Recovery

[+] Author and Article Information
Brent L. Showalter

Department of Bioengineering,
University of Pennsylvania,
424 Stemmler, 36th and Hamilton Walk,
Philadelphia, PA 19104

Dawn M. Elliott

Department of Biomedical Engineering,
University of Delaware,
161 Colburn,
150 Academy Street,
Newark, DE 19716

Weiliam Chen

Endomedix, Inc.,
Enterprise Development Center,
New Jersey Institute of Technology,
211 Warren Street,
Newark, NJ 07103

Neil R. Malhotra

Department of Neurosurgery,
University of Pennsylvania,
3 Silverstein Pavilion,
3400 Spruce Street,
Philadelphia, PA 19104
e-mail: Neil.malhotra@uphs.upenn.edu

1Corresponding author.

Manuscript received July 21, 2014; final manuscript received April 27, 2015; published online June 16, 2015. Assoc. Editor: Sean S. Kohles.

J Biomech Eng 137(8), 081008 (Aug 01, 2015) (7 pages) Paper No: BIO-14-1334; doi: 10.1115/1.4030530 History: Received July 21, 2014; Revised April 27, 2015; Online June 16, 2015

Despite the prevalence of disc degeneration and its contributions to low back problems, many current treatments are palliative only and ultimately fail. To address this, nucleus pulposus replacements are under development. Previous work on an injectable hydrogel nucleus pulposus replacement composed of n-carboxyethyl chitosan, oxidized dextran, and teleostean has shown that it has properties similar to native nucleus pulposus, can restore compressive range of motion in ovine discs, is biocompatible, and promotes cell proliferation. The objective of this study was to determine if the hydrogel implant will be contained and if it will restore mechanics in human discs undergoing physiologic cyclic compressive loading. Fourteen human lumbar spine segments were tested using physiologic cyclic compressive loading while intact, following nucleotomy, and again following treatment of injecting either phosphate buffered saline (PBS) (sham, n = 7) or hydrogel (implant, n = 7). In each compressive test, mechanical parameters were measured immediately before and after 10,000 cycles of compressive loading and following a period of hydrated recovery. The hydrogel implant was not ejected from the disc during 10,000 cycles of physiological compression testing and appeared undamaged when discs were bisected following all mechanical tests. For sham samples, creep during cyclic loading increased (+15%) from creep during nucleotomy testing, while for implant samples creep strain decreased (−3%) toward normal. There was no difference in compressive modulus or compressive strains between implant and sham samples. These findings demonstrate that the implant interdigitates with the nucleus pulposus, preventing its expulsion during 10,000 cycles of compressive loading and preserves disc creep within human L5–S1 discs. This and previous studies provide a solid foundation for continuing to evaluate the efficacy of the hydrogel implant.

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Vernon-Roberts, B., Moore, R. J., and Fraser, R. D., 2007, “The Natural History of Age-Related Disc Degeneration: The Pathology and Sequelae of Tears,” Spine, 32(25), pp. 2797–2804. [CrossRef] [PubMed]
Katz, J. N., 2006, “Lumbar Disc Disorders and Low-Back Pain: Socioeconomic Factors and Consequences,” J. Bone Jt. Surg., 88(Suppl. 2), pp. 21–24. [CrossRef]
Luo, X., Pietrobon, R., Sun, S. X., Liu, G. G., and Hey, L., 2004, “Estimates and Patterns of Direct Health Care Expenditures Among Individuals With Back Pain in the United States,” Spine, 29(1), pp. 79–86. [CrossRef] [PubMed]
Andersson, G. B. J., 1999, “Epidemiological Features of Chronic Low-Back Pain,” Lancet, 354(9178), pp. 581–585. [CrossRef] [PubMed]
Rajaee, S. S., Bae, H. W., Kanim, L. E. A., and Delamarter, R. B., 2012, “Spinal Fusion in the United States,” Spine, 37(1), pp. 67–76. [CrossRef] [PubMed]
Mirza, S. K., and Deyo, R. A., 2007, “Systematic Review of Randomized Trials Comparing Lumbar Fusion Surgery to Nonoperative Care for Treatment of Chronic Back Pain,” Spine, 32(7), pp. 816–823. [CrossRef] [PubMed]
Hilibrand, A. S., and Robbins, M., 2004, “Adjacent Segment Degeneration and Adjacent Segment Disease: The Consequences of Spinal Fusion?,” Spine J., 4(Suppl. 6), pp. S190–S194. [CrossRef]
Bertagnoli, R., and Kumar, S., 2002, “Indications for Full Prosthetic Disc Arthroplasty: A Correlation of Clinical Outcome Against a Variety of Indications,” Eur. Spine J., 11(2), pp. S131–S136. [CrossRef] [PubMed]
Kurtz, S. M., van Ooij, A., Ross, R., de Waal Malefijt, J., Peloza, J., Ciccarelli, L., and Villarraga, M. L., 2007, “Polyethylene Wear and Rim Fracture in Total Disc Arthroplasty,” Spine J., 7(1), pp. 12–21. [CrossRef] [PubMed]
DiAngelo, D. J., Foley, K. T., Morrow, B. R., Schwab, J. S., Song, J., German, J. W., and Blair, E., 2004, “In Vitro Biomechanics of Cervical Disc Arthroplasty With the ProDisc-C Total Disc Implant,” Neurosurg. Focus, 17(3), pp. 44–54. [CrossRef]
Lewis, G., 2012, “Nucleus Pulposus Replacement and Regeneration/Repair Technologies: Present Status and Future Prospects,” J. Biomed. Mater. Res., Part B, 100(6), pp. 1702–1720. [CrossRef]
Reitmaier, S., Wolfram, U., Ignatius, A., Wilke, H.-J., Gloria, A., Martín-Martínez, J. M., Silva-Correia, J., Miguel Oliveira, J., Luís Reis, R., and Schmidt, H., 2012, “Hydrogels for Nucleus Replacement—Facing the Biomechanical Challenge,” J. Mech. Behav. Biomed. Mater., 14, pp. 67–77. [CrossRef] [PubMed]
Peroglio, M., Grad, S., Mortisen, D., Sprecher, C., Illien-Junger, S., Alini, M., and Eglin, D., 2011, “Injectable Thermoreversible Hyaluronan-Based Hydrogels for Nucleus Pulposus Cell Encapsulation,” Eur. Spine. J., 21(Suppl. 6), pp. S839–S849. [CrossRef] [PubMed]
Omlor, G., Nerlich, A., Lorenz, H., Bruckner, T., Richter, W., Pfeiffer, M., and Gühring, T., 2012, “Injection of a Polymerized Hyaluronic Acid/Collagen Hydrogel Matrix in an In Vivo Porcine Disc Degeneration Model,” Eur. Spine. J., 21(9), pp. 1700–1708. [CrossRef] [PubMed]
Zhang, H., Qadeer, A., Mynarcik, D., and Chen, W., 2011, “Delivery of Rosiglitazone From an Injectable Triple Interpenetrating Network Hydrogel Composed of Naturally Derived Materials,” Biomaterials, 32(3), pp. 890–898. [CrossRef] [PubMed]
Smith, L. J., Gorth, D. J., Showalter, B. L., Chiaro, J., Beattie, E. E., Elliott, D. M., Mauck, R. L., Chen, W., and Malhotra, N. R., 2014, “In Vitro Characterization of a Stem-Cell-Seeded Triple-Interpenetrating-Network Hydrogel for Functional Regeneration of the Nucleus Pulposus,” Tissue Eng., Part A, 20(13–14), pp. 1841–1849. [CrossRef]
Malhotra, N. R., Han, W. M., Beckstein, J., Cloyd, J., Chen, W., and Elliott, D. M., 2012, “An Injectable Nucleus Pulposus Implant Restores Compressive Range of Motion in the Ovine Disc,” Spine, 37(18), pp. E1099–E1105. [CrossRef] [PubMed]
Pelletier, M. H., Cohen, C. S., Ducheyne, P., and Walsh, W. R., “Restoring Segmental Biomechanics Through Nucleus Augmentation: An In Vitro Study,” J. Spinal Disord. Tech. (published online). [CrossRef]
Cloyd, J., Malhotra, N., Weng, L., Chen, W., Mauck, R., and Elliott, D., 2007, “Material Properties in Unconfined Compression of Human Nucleus Pulposus, Injectable Hyaluronic Acid-Based Hydrogels and Tissue Engineering Scaffolds,” Eur. Spine. J., 16(11), pp. 1892–1898. [CrossRef] [PubMed]
Reitmaier, S., Shirazi-Adl, A., Bashkuev, M., Wilke, H. J., Gloria, A., and Schmidt, H., 2012, “In Vitro and In Silico Investigations of Disc Nucleus Replacement,” J. R. Soc., Interface, 9(73), pp. 1869–1879. [CrossRef]
Sivan, S. S., Roberts, S., Urban, J. P., Menage, J., Bramhill, J., Campbell, D., Franklin, V. J., Lydon, F., Merkher, Y., Maroudas, A., and Tighe, B. J., 2014, “Injectable Hydrogels With High Fixed Charge Density and Swelling Pressure for Nucleus Pulposus Repair: Biomimetic Glycosaminoglycan Analogues,” Acta Biomater., 10(3), pp. 1124–1133. [CrossRef] [PubMed]
Dahl, M. C., Ellingson, A. M., Mehta, H. P., Huelman, J. H., and Nuckley, D. J., 2013, “The Biomechanics of a Multilevel Lumbar Spine Hybrid Using Nucleus Replacement in Conjunction With Fusion,” Spine J., 13(2), pp. 175–183. [CrossRef] [PubMed]
Heuer, F., Ulrich, S., Claes, L. E., and Wilke, H.-J., 2008, “Biomechanical Evaluation of Conventional Anulus Fibrosus Closure Methods Required for Nucleus Replacement,” J. Neurosurg., 9(3), pp. 307–313. [CrossRef]
Bertagnoli, R., Sabatino, C. T., Edwards, J. T., Gontarz, G. A., Prewett, A., and Parsons, J. R., 2005, “Mechanical Testing of a Novel Hydrogel Nucleus Replacement Implant,” Spine J., 5(6), pp. 672–681. [CrossRef] [PubMed]
Johannessen, W., Cloyd, J., O’Connell, G., Vresilovic, E., and Elliott, D., 2006, “Trans-Endplate Nucleotomy Increases Deformation and Creep Response in Axial Loading,” Ann. Biomed. Eng., 34(4), pp. 687–696. [CrossRef] [PubMed]
Showalter, B. L., Malhotra, N. R., Vresilovic, E. J., and Elliott, D. M., 2014, “Nucleotomy Reduces the Effects of Cyclic Compressive Loading With Unloaded Recovery on Human Intervertebral Discs,” J. Biomech., 47(11), pp. 2633–2640. [CrossRef] [PubMed]
Sivan, S., Merkher, Y., Wachtel, E., Ehrlich, S., and Maroudas, A., 2006, “Correlation of Swelling Pressure and Intrafibrillar Water in Young and Aged Human Intervertebral Discs,” J. Orthop. Res., 24(6), pp. 1292–1298. [CrossRef] [PubMed]
Adams, M. A., Dolan, P., Hutton, W. C., and Porter, R. W., 1990, “Diurnal Changes in Spinal Mechanics and Their Clinical Significance,” J. Bone Joint Surg., 72B(2), pp. 266–270.
Wilke, H. J., Neef, P., Caimi, M., Hoogland, T., and Claes, L. E., 1999, “New In Vivo Measurements of Pressures in the Intervertebral Disc in Daily Life,” Spine, 24(8), pp. 755–762. [CrossRef] [PubMed]
Balkovec, C., Vernengo, J., and McGill, S. M., 2013, “The Use of a Novel Injectable Hydrogel Nucleus Pulposus Replacement in Restoring the Mechanical Properties of Cyclically Fatigued Porcine Intervertebral Discs,” ASME J. Biomech. Eng., 135(6), p. 061004. [CrossRef]
Pfirrmann, C. W. A., Metzdorf, A., Zanetti, M., Hodler, J., and Boos, N., 2001, “Magnetic Resonance Classification of Lumbar Intervertebral Disc Degeneration,” Spine, 26(17), pp. 1873–1878. [CrossRef] [PubMed]
Marinelli, N. L., Haughton, V. M., and Anderson, P. A., 2010, “T2 Relaxation Times Correlated With Stage of Lumbar Intervertebral Disk Degeneration and Patient Age,” Am. J. Neuroradiology, 31(7), pp. 1278–1282. [CrossRef]
Kerttula, L., Kurunlahti, M., Jauhiainen, J., Koivula, A., Oikarinen, J., and Tervonen, O., 2001, “Apparent Diffusion Coefficients and T2 Relaxation Time Measurements to Evaluate Disc Degeneration. A Quantitative MR Study of Young Patients With Previous Vertebral Fracture,” Acta Radiol., 42(6), pp. 585–591. [CrossRef] [PubMed]
Weinstein, J. N., Lurie, J. D., Tosteson, T. D., Skinner, J. S., Hanscom, B., Tosteson, A. N. A., Herkowitz, H., Fischgrund, J., Cammisa, F. P., Albert, T., and Deyo, R. A., 2006, “Surgical Versus Nonoperative Treatment for Lumbar Disk Herniation,” JAMA, J. Am. Med. Assoc., 296(20), pp. 2451–2459. [CrossRef]
Beckstein, J. C., Sen, S., Schaer, T. P., Vresilovic, E. J., and Elliott, D. M., 2008, “Comparison of Animal Discs Used in Disc Research to Human Lumbar Disc: Axial Compression Mechanics and Glycosaminoglycan Content,” Spine, 33(6), pp. E166–E173. [CrossRef] [PubMed]
Elliott, D. M., and Sarver, J. J., 2004, “Young Investigator Award Winner: Validation of the Mouse and Rat Disc as Mechanical Models of the Human Lumbar Disc,” Spine, 29(7), pp. 713–722. [CrossRef] [PubMed]
Nachemson, A. L., 1981, “Disc Pressure Measurements,” Spine, 6(1), pp. 93–97. [CrossRef] [PubMed]
Brinckmann, P., Johannleweling, N., Hilweg, D., and Biggemann, M., 1987, “Fatigue Fracture of Human Lumbar Vertebrae,” Clin. Biomech., 2(2), pp. 94–96. [CrossRef]
Johannessen, W., Vresilovic, E. J., Wright, A. C., and Elliott, D. M., 2004, “Intervertebral Disc Mechanics Are Restored Following Cyclic Loading and Unloaded Recovery,” Ann. Biomed. Eng., 32(1), pp. 70–76. [CrossRef] [PubMed]
Dullerud, R., Amundsen, T., Johansen, J. G., and Magnaes, B., 1993, “Lumbar Percutaneous Automated Nucleotomy—Technique, Patient Selection, and Preliminary Results,” Acta Radiol., 34(6), pp. 536–542. [CrossRef] [PubMed]
Castro, W. H. M., Jerosch, J., Halm, H., and Rondhuis, J., 1992, “How Much Nuclear Material Is Removed With Percutaneous Nucleotomy,” Z. Orthopadie Grenzgeb., 130(6), pp. 467–471. [CrossRef]
Antoniou, J., Steffen, T., Nelson, F., Winterbottom, N., Hollander, A. P., Poole, R. A., Aebi, M., and Alini, M., 1996, “The Human Lumbar Intervertbral Disc: Evidence for Changes in the Biosynthesis and Denaturation of the Extracellular Matrix With Growth, Maturation, Ageing, and Degeneration,” J. Clin. Invest., 98(4), pp. 996–1003. [CrossRef] [PubMed]
Fountas, K. N., Kapsalaki, E. Z., Feltes, C. H., Smisson, H. F., Johnston, K. W., Vogel, R. L., and Robinson, J. S., 2004, “Correlation of the Amount of Disc Removed in a Lumbar Microdiscectomy With Long-Term Outcome,” Spine, 29(22), pp. 2521–2524. [CrossRef] [PubMed]
O’Connell, G. D., Vresilovic, E. J., and Elliott, D. M., 2007, “Comparison of Animals Used in Disc Research to Human Lumbar Disc Geometry,” Spine, 32(3), pp. 328–333. [CrossRef] [PubMed]
Ahrens, M., Tsantrizos, A., Donkersloot, P., Martens, F., Lauweryns, P., Le Huec, J. C., Moszko, S., Fekete, Z., Sherman, J., Yuan, H. A., and Halm, H., 2009, “Nucleus Replacement With the Dascor Disc Arthroplasty Device: Interim Two-Year Efficacy and Safety Results From Two Prospective, Non-Randomized Multicenter European Studies,” Spine, 34(13), pp. 1376–1384. [CrossRef] [PubMed]
Allen, M. J., Schoonmaker, J. E., Bauer, T. W., Williams, P. F., Higham, P. A., and Yuan, H. A., 2004, “Preclinical Evaluation of a Poly (Vinyl Alcohol) Hydrogel Implant as a Replacement for the Nucleus Pulposus,” Spine, 29(5), pp. 515–523. [CrossRef] [PubMed]
Bron, J. L., Helder, M. N., Meisel, H. J., Van Royen, B. J., and Smit, T. H., 2009, “Repair, Regenerative and Supportive Therapies of the Annulus Fibrosus: Achievements and Challenges,” Eur. Spine. J., 18(3), pp. 301–313. [CrossRef] [PubMed]
Mochida, J., Nishimura, K., Nomura, T., Toh, E., and Chiba, M., 1996, “The Importance of Preserving Disc Structure in Surgical Approaches to Lumbar Disc Herniation,” Spine, 21(13), pp. 1556–1564. [CrossRef] [PubMed]
Coric, D., and Mummaneni, P. V., 2008, “Nucleus Replacement Technologies,” J. Neurosurg., Spine, 8(2), pp. 115–120. [CrossRef]
Urban, J. P. G., Smith, S., and Fairbank, J. C. T., 2004, “Nutrition of the Intervertebral Disc,” Spine, 29(23), pp. 2700–2709. [CrossRef] [PubMed]
Liebscher, T., Haefeli, M., Wuertz, K., Nerlich, A. G., and Boos, N., 2011, “Age-Related Variation in Cell Density of Human Lumbar Intervertebral Disc,” Spine, 36(2), pp. 153–159. [CrossRef] [PubMed]
Iatridis, J. C., Weidenbaum, M., Setton, L. A., and Mow, V. C., 1996, “Is the Nucleus Pulposus a Solid or a Fluid? Mechanical Behaviors of the Nucleus Pulposus of the Human Intervertebral Disc,” Spine, 21(10), pp. 1174–1184. [CrossRef] [PubMed]
Kumar, D., Gerges, I., Tamplenizza, M., Lenardi, C., Forsyth, N. R., and Liu, Y., 2014, “Three-Dimensional Hypoxic Culture of Human Mesenchymal Stem Cells Encapsulated in a Photocurable, Biodegradable Polymer Hydrogel: A Potential Injectable Cellular Product for Nucleus Pulposus Regeneration,” Acta Biomater., 10(8), pp. 3463–3474. [CrossRef] [PubMed]
Omlor, G. W., Fischer, J., Kleinschmitt, K., Benz, K., Holschbach, J., Brohm, K., Anton, M., Guehring, T., and Richter, W., 2014, “Short-Term Follow-Up of Disc Cell Therapy in a Porcine Nucleotomy Model With an Albumin-Hyaluronan Hydrogel: In Vivo and In Vitro Results of Metabolic Disc Cell Activity and Implant Distribution,” Eur. Spine J., 23(9), pp. 1837–1847. [CrossRef] [PubMed]


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Fig. 2

The mechanical testing procedure altered disc hydration. Discs are fully hydrated in a PBS bath containing protease inhibitors (steps 1 and 5), and have reduced hydration after cyclic loading (step 3). Mechanical parameters are measured after each change in hydration level (steps 2, 4, and 6).

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Fig. 1

T2 relaxation times are strongly correlated to Pfirrmann scores for the human L5–S1 discs used in this study

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Fig. 3

Mechanical parameters are found using a trilinear fit of force–displacement curve from 50th cycle of the mechanical measurement steps (steps 2, 4, and 6 of the testing procedure). The compression loading curve (diamonds) is separated from the data. Compression range of motion is the displacement between 0 and 0.48 MPa on the compression loading curve. Compression stiffness is the slope of the line fit through 0.38 and 0.48 MPa. Compressive stiffness and range of motion are then normalized by intact disc area and height.

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Fig. 8

Percent change in compression modulus between the initial and cyclic time point for the samples in the implant group. This correlation was not significant for the samples while they were intact or following nucleotomy, but was significant following injection of the hydrogel. The slope (m) and y-intercepts (b) of the regression are show in the legend.

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Fig. 4

Bisected human L5–S1 disc after complete mechanical test, including 10,000 cycles of compressive loading. The hydrogel implant stayed intact within the disc, although some of the toluidine blue used to dye the gel leached into the surrounding disc tissue. The enlarged region shows that the implant (dark region in lower left corner of inset) filled in the irregular contours of the remaining nucleus pulposus (light region of inset).

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Fig. 5

Cyclic loading caused an increase in compression modulus (a) and compression strain (b) for both sham and implant samples. These increases were recovered following a period of overnight hydration, indicating that the changes are due to changes in hydration distribution within the intervertebral disc. Recoverable increases in compression modulus and strain are consistent with trends in intact and nucleotomy samples. Data presented as mean + standard error (* indicates p < 0.05).

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Fig. 6

Nucleotomy increased creep strain (a). Following treatment, strain continued to increase for sham samples, but decreased for implant samples (b). Data presented as mean + standard error (* indicates p < 0.05).

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Fig. 7

Percent change from nucleotomy values for sham and implant samples. Treatment caused no change in compression modulus (a). Compression strain continued to increase for both sham and implant samples at the cyclic and recovery time points (b). Data presented as mean + standard error (+ indicates p < 0.05 versus nucleotomy values).



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