Small area analysis of surgery for low-back pain.

Rates of spine surgery (discectomy, laminectomy, fusion) vary several-fold among "small areas" such as counties or hospital market areas. To ascertain why this is so, an analysis was conducted of variability in rates among counties in the State of Washington (N = 39). Since, unlike previous published reports, this study excluded patients with cancer, major trauma, and infection, as well as those with cervical and thoracic procedures, rates in this study pertain specifically to the problem of low-back pain. Six classes of variables to explain variability among county rates were defined: I) percentage of the labor force in heavy labor and transportation occupations; II) socioeconomic conditions; III) neurologic and orthopedic surgeon density; IV) occupancy rate of back surgery hospitals; V) primary payer and VI) health care availability. In all, the effect of 28 explanatory variables was tested. In doing so, the authors took into account the possibility of spurious correlation. The rate of surgery for low-back pain varied nearly 15-fold among counties. The explanatory variables that were tested, however, accounted for only a minor part of the variability. The hypothesis that "physician practice style factor" accounts for the major part is explored; potential properties of practice style factor are specified for further testing.