Disfiguring head injuries from car accidents, work injuries or personal injuries left plastic and cranial surgeons with the problem of how to fill the gaps. This problem may soon be medical history as a new polymer foam material has been invented that serves as a scaffold. With its interconnected pores it allows bone to fill the gaps and subsequently gets absorbed leaving new bone in the place where the scaffolding foam had been placed by the surgeon. Texas A&M and Rensselaer Polytechnic Institute researcher Melissa Grunlan who is an associate professor in the university’s Department of Biomedical Engineering develop this material together with her co-workers.
It has interesting properties. The shape of memory polymer foam (SMP foam) is malleable when treated with warm saline water and can be fitted into the bone gaps from the injury. After a short time it hardens in place and provides the scaffolding needed for new bone growth.
This new material lends itself to fill gaps from birth defects (like cleft palates), from facial injuries or from the removal of bone tumors in the head, jaw or face.
Traditionally, bone grafts were used to fill gaps. They had to be taken from an area like the hip, but there were problems attaching these grafts to the underlying bone to which the graft would hopefully attach to in the future. Many complications could occur like graft absorption leaving the original defect or infection of the grafted material.
With the new polymer foam material there is instant attachment, instant shaping of the surface of the material and very quick population of the foam with bone cells from the surrounding bone. In addition, the polymer foam has all its surfaces coated with a bioactive substance that attracts bone-forming cells, called osteoblasts. Experiments have shown that after only three days the coated sponge channels attracted five fold more osteoblasts than that of uncoated control foam material.
Traditional bone grafting
Traditionally, bone grafts are used to help with complicated fractures in the healing process. In spinal surgery bone grafts may be required to over bridge facet joints with end stage arthritis, as following successful healing after fusion surgery the back pain will improve significantly. Bone grafts have also been used when bone defects were present from severe infection, injury or congenital defects. In these cases the bone graft is used to fill in the defect. Finally, bone grafts are sometimes necessary to fill in bone following surgical hip joint replacements or after repairs of fractures with plates and screws. More about these traditional bone graft techniques can be found through this link.
Complications of traditional bone grafting
Complications depend very much on the location of the surgery and what type of procedure is being used. For instance when it comes to fusion surgery in the lower neck or lower back region, the traditional success rate of fusion surgery is about 70%, which means that in 30% of cases the procedure did not work. On the one hand the combination of mechanical stabilization through instrumentation with bone grafting has increased the success rate of fusion surgery above 70%. But smoking, older age, osteoporosis, obesity, diabetes, and prior spinal surgery have decreased the success rate as indicated in this review.
This overview about autografts (bone graft in the same patient), allografts (bone grafts with bone from a bone donor center), xenografts (bone from an animal) as well as synthetic bone grafting explains more details about these topics.
Another website also contains useful information about this topic.
Other applications for memory polymer foam
In the same facility Duncan Maitland, associate professor in the university’s Department of Biomedical Engineering, is researching the use of SMP foam for the treatment of brain aneurysms in humans. A flat piece of SMP foam is introduced into the aneurysm, a sac-like pouch of a brain blood vessel and activated through heat from a laser beam. This actives the foam to become round and fill the pouch of the aneurysm, closing off the area that could have ruptured and led to bleeding. This application has to be proven in clinical trials as well as does the use of the SMP foam for bone defects.
Often in medicine new ideas were necessary to lead to progress in treatments. For instance when hemoglobin A1C was detected by an Iranian team of doctors, all of a sudden a powerful tool to monitor treatment of diabetes had become available. Prostate specific antigen (the PSA test) is another example of a test that allows for a much earlier diagnosis of prostate cancer. Earlier detection of prostate cancer leads to a more successful treatment of this cancer.
With memory polymer foam (SMP foam) physicians will soon be given a new tool of closing big bone gaps to help their patients overcome unsightly appearances or unstable situations in the spine or in other body locations. The brain aneurysm application will help prevent brain hemorrhages. More research is needed for these clinical applications, but the initial research shows a lot of promise.
More information on bone cancer where following surgery large bone defects can remain: http://nethealthbook.com/cancer-overview/bone-cancer/
Last edited Nov. 8, 2014