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Oct 2017

Best Papers Focus on Disc Regeneration, Pelvic Incidence

Reproduced from North American Spine Society

Regenerating degenerated discs and realigning a distorted spine are two of the ultimate goals of spinal medicine. Two abstracts presented during the Best Papers session on Thursday moved clinicians closer to both goals.

Degenerative disc disease is one of the most intractable conditions seen in many spinal practices. New data show that disc degeneration is not irreversible in rats and may not be irreversible in humans.

William Mark Erwin, DC, PhD

“The holy grail is if we can induce any biological effect that can affect disc degeneration,” said William Mark Erwin, DC, PhD, of Krembil Research Institute in Toronto, Canada. “In other words, is regeneration possible? Our findings suggest that regeneration is not only possible, but that it may be possible to develop a minimally invasive, percutaneous delivery of cell-based bioreactive factors to mediate the progression of degeneration of the disc.”

Dr. Erwin was lead author on a study designed to identify factors secreted by the notochordal cell-rich intervertebral disc nucleus pulposus that are necessary and sufficient to regenerate the disc. Researchers previously found that notochordal cell conditioned medium (NCCM) can somehow suppress the catabolic effects on inflammatory cytokines on nucleus pulposus cells and stimulate near normal anabolic activity and suppress apoptotic signaling.

A single injection of NCCM into the degenerative disc of a rodent model of degenerative disc disease (DDD) can protect the intervertebral disc from degeneration. What they did not know was which components of NCCM were responsible for the protective and restorative activity. The current round of research identified two proteins, TGFB1 (transforming growth factor beta-1) and CTGF (connective tissue growth factor), that are both necessary and sufficient to regenerate the degenerative disc in a rat-tail model of DDD.

Researchers used a needle puncture injury to stimulate disc degeneration in rat tails. Within eight to 10 weeks of injury, the degenerative disc assumes a fibrocartilaginous phenotype with loss of notochordal and stem cells, a proliferation of chondrocyte-like cells and a characteristic pattern of cellular and extracellular matrix remodeling.

“Injection of recombinant forms of notochordal cell-secreted factors reverses this trend and preserves and regenerates the IVD NP back to a near normal phenotype,” Dr. Erwin said. “We hope to be able to use these proteins to spur regeneration of regenerative discs in the future.”

New findings on pelvic incidence (PI) could be equally transformative to spine practice. Clinicians and researchers in adult spinal deformity generally assume that the base of the spine, the pelvic vertebrae, are fixed, forming a solid and unmoving base for the spine. Emerging evidence suggests otherwise.

Howard M. Place, MD

“Pelvic parameters have become a very hot topic,” said Howard M. Place, MD, of St. Louis University. “Many of the recent studies addressing adult spinal deformity look to the position of the fused spine as it relates to the position of the pelvis as the outcome. We recognize that pelvic tilt (PT) and sacral slope (SS) can change, but we assume PI is a fixed value for an individual. But is it? What if the PI varies with pelvic rotation?”

Dr. Place was lead author on a study in 50 healthy volunteers that suggests the conventional wisdom about PI being a fixed value is incorrect. While the implications of the new findings are still emerging, they immediately cast doubt on the mathematical relationship of the pelvic parameters that is commonly used in preoperative planning.

Researchers compared standing lateral radiographs for each of 50 healthy volunteers in three positions: resting, anterior pelvic rotation and posterior pelvic rotation. An orthopedic spine surgeon and a musculoskeletal radiologist measured PT, SS and PI.

While this was a single sample observational study at a single site, the internal consistency for all 150 PI measurements was excellent, Dr. Place said, with an R value of 0.971.

The PI values changed in 88% of the subjects (44 of 50) when comparing resting position with maximal anterior pelvic rotation. The mean change was small, 2.9o, but change was consistent across the cohort. Nearly half of the cohort (46%) had a change of 3o or more.

Results were similar for maximal posterior rotation. PI values changed in 80% of subjects (40 of 50), with a mean change of 2.82o. Just over half of the subjects (27) showed a change of 3o or greater.

In addition to casting doubt on the parameters commonly used to realign patients surgically, the findings also play into common notions about sacroiliac mobilization as a treatment for low back pain. Many orthopedic surgeons dismiss the concept because they assume there is no motion at this joint. It may be time to reconsider physical therapy options for patients with certain types of lumbopelvic dysfunction.

“We need to stop thinking of PI as a fixed value,” Dr. Place said. “The foundation of the spine is clearly mobile.”

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