The incidence of neural tube defects (NTDs) is declining in several areas of the world, including the United States. While the reasons for this are unclear, there seems to be some effect from prenatal diagnosis, genetic counseling, and possibly nutritional supplementation 1)
There is marked geographic variation in the rates of arthrodesis in treatment of spondylolisthesis within the United States. This variation remains pronounced after accounting for patient-level demographic differences. Costs of surgery and quality outcomes also vary widely. Further study is necessary to understand the drivers of this variation 3).