Photo-Crosslinkable Poly(trimethylene carbonate)-Based Macromers for Closure of Ruptured Intervertebral Discs

In patients with low back pain, surgical removal of the partially herniated nucleus pulposus may lead to clinical improvement but ultimately leads to intervertebral disc degeneration and recurrence of back pain is frequent. As an alternative treatment, use of an injectable material which solidifies in situ, is proposed. Such materials can easily fill oddly-shaped defects in the annulus fibrosus and seal the disc through a minimally invasive surgical procedure, thereby protecting the disc from further degeneration. In this study, a series of injectable and photo-crosslinkable macromers based on poly trimethylene carbonate (PTMC) and polyethylene glycol (PEG) were prepared. It is shown that these materials are injectable and solidify within two minutes upon illumination with visible light. By varying the PTMC to PEG block ratios, material properties such as elastic modulus and water content could easily be tuned to match those of the native annulus fibrosus. Ex vivo results using canine cadaveric spines showed the potential of the materials to seal an opening in the annulus fibrosus, although the adhesion of the photo-crosslinked material to the disc tissue needs to be improved.