Removing extensive spinal tumors often requires taking out the entire bone segment and adjacent intervertebral discs from the affected area. Then, something must fill the void to maintain the integrity of the spine and protect the spinal cord.

A polymer graft offers a non-invasive, inexpensive method to fill gaps in the spine after tumor removal. Image source: American Chemical Society. In the past, a surgeon might open the chest cavity and insert metal cages or bone grafts to replace the missing fragment. A less invasive option involved making a cut in the back, but that offered only enough space to insert short expandable titanium rods, which could be costly.

A less expensive graft compatible with the posterior spinal surgery option was developed by researchers at the Mayo Clinic in the U.S., who sought a material that could be dehydrated down to a size suitable for the procedure. The implant then absorbs fluids from the body, expanding to replace the missing vertebrae.

A biocompatible polymer, oligo[poly(ethylene glycol) fumarate], was crosslinked to create a hollow hydrophilic cage — the scaffold of the graft — which could then be filled with stabilizing materials and therapeutics. The researchers focused on controlling the size of the graft and the kinetics of the expansion. That’s because if the cage expands too quickly, a surgeon may not have enough time to position it correctly. A slow expansion, meanwhile, could mean a longer-than-necessary surgery. Modifying the degree and timing of the polymer graft’s expansion was a matter of chemistry, and entailed modulating the molecular weight and charge of the polymer.

The next step is to study the grafts in cadavers and simulate an in-patient procedure, with the goal of conducting clinical trials within the next few years.

The researchers presented their work at the National Meeting & Exposition of the American Chemical Society.