The study examines trends and regional variations in lumbar spine surgery rates in the United States from 1992 to 2003 using Medicare data. Lumbar fusion rates increased steadily, from 0.3 per 1,000 enrollees in 1992 to 1.1 per 1,000 in 2003. Regional variations were significant, with rates of lumbar fusion varying by nearly 20-fold. Medicare spending on back surgery more than doubled over the decade, with lumbar fusion spending increasing over 500%. By 2003, lumbar fusion accounted for 47% of total back surgery spending. Rates of lumbar discectomy/laminectomy and fusion were positively correlated across regions, but changes in one did not correlate with changes in the other. Rates of back surgery were not correlated with the per-capita supply of orthopaedic and neurosurgeons. The study highlights the lack of scientific evidence and financial incentives as potential factors behind the variations. The scientific evaluation of outcomes for spine surgery has not kept up with changes in operative techniques, and there is a need for further research to assess the effectiveness of spinal procedures. The study emphasizes the importance of evaluating new technologies and existing practices to improve the scientific basis of everyday practice.The study examines trends and regional variations in lumbar spine surgery rates in the United States from 1992 to 2003 using Medicare data. Lumbar fusion rates increased steadily, from 0.3 per 1,000 enrollees in 1992 to 1.1 per 1,000 in 2003. Regional variations were significant, with rates of lumbar fusion varying by nearly 20-fold. Medicare spending on back surgery more than doubled over the decade, with lumbar fusion spending increasing over 500%. By 2003, lumbar fusion accounted for 47% of total back surgery spending. Rates of lumbar discectomy/laminectomy and fusion were positively correlated across regions, but changes in one did not correlate with changes in the other. Rates of back surgery were not correlated with the per-capita supply of orthopaedic and neurosurgeons. The study highlights the lack of scientific evidence and financial incentives as potential factors behind the variations. The scientific evaluation of outcomes for spine surgery has not kept up with changes in operative techniques, and there is a need for further research to assess the effectiveness of spinal procedures. The study emphasizes the importance of evaluating new technologies and existing practices to improve the scientific basis of everyday practice.