Table 2.
Nucleus pulposus repair or replacement devices
| Polymer | Trade name or reference | Clinical trials? | Measurement outcomes/comments |
|---|---|---|---|
| Injectable synthetic polymers | |||
| Copolymeric hydrogel (PAN and polyacrylamide) encased in a polyethylene fiber jacket | PDN | Yes | No longer in use |
| Semihydrated poly(vinyl) alcohol | Aquarelle | Yes | No longer in use |
| Copolymer of poly(vinyl alcohol) [and poly(vinyl pyrrolidone) or modified PAN] reinforced by a Dacron mesh | NeuDisc™ | Yes | Restored compressive stiffness |
| Hydrating PAN | NucleoFix™ | Yes | Marketed under CE mark |
| In situ forming (or cross-linked) synthetic and biologically based polymers | |||
| In situ curing polymer using inflatable polyurethane “balloon” | DASCOR™ | Yes | Restored multidirectional segment flexibility |
| In situ curing polymerized water-in-oil emulsion composite | DiscCell™ | Yes | From in vitro work: restored motion segment stabilitya |
| Glutaraldehyde cross-linked albumin | Biodisc™ | Yes | Uncertain status |
| Hydrogel of a chemically cross-linked elastin and silk polypeptide | NuCore™ | Yes | Maintenance of disc height; significantly reduced leg and back pain; improved function scores in discectomy patients |
| Oxidized hyaluronic acid gelatin implant | 133 | Preclinical | Restored motion segment stability; no changes in stiffness |
| Thiol-modified hyaluronan and elastin-like polypeptide | 134 | Preclinical | Restored stiffness |
| Sulfonate-containing glycosaminoglycan surrogates | 135 | NA | Restored stiffness; maintained disc height under compression |
| Silk fibroin/polyurethane composite | 136 | Preclinical | Mechanical properties stable over time; higher stiffness than native NP but conducive for cell support |
| PNIPAAm-PEG hydrogels | 137 | NA | Enhanced recovery from compressive strain, was thermoresponsive, sustained drug release |
| Chitosan gels | 138 | NA | Supported matrix accumulation for native cells and retention of proteoglycan |
| Hyaluronic acid/collagen hydrogel | 93 | Preclinical | Implant did not improve disc height; increased scarring and inflammation in AF |
| Hyaluronan polymers | 139 | Preclinical | Prevented fibrotic changes; supported cell growth; no mechanical outcomes |
| Hyaluroan / PEG crosslinked copolymer | 102 | NA | Engineered design that could be targeted to maintain NP or AF cell phenotype in vitro |
| Collagen type II / hyaluronan-PEG crosslinked hydrogel | 104 | NA | Supported maintenance of cell phenotype and biosynthesis for native NP cells |
Restored stability is equivalent to reduced range of motion in flexion—extension, lateral bending, or restored neutral zone mechanics. Abbreviations: AF, anulus fibrosus; CE, European Conformity; NP, nucleus pulposus; PAN, polyacrylonitrile; PEG, polyethylene glycol; PNIPPAm, poly(N-isopropyl acrylamide).