United States' trends and regional variations in lumbar spine surgery: 1992-2003

Abstract

Study design: Repeated cross-sectional analysis using national Medicare data from the Dartmouth Atlas Project.

Objective: To describe recent trends and geographic variation in population-based rates of lumbar fusion spine surgery.

Summary of background data: Lumbar fusion rates have increased dramatically during the 1980s and even more so in the 1990s. The most rapid increase appeared to follow the approval of a new surgical implant device.

Methods: Medicare claims and enrollment data were used to calculate age, sex, and race-adjusted rates of lumbar laminectomy/discectomy and lumbar fusion for fee-for-service Medicare beneficiaries over age 65 in each of the 306 US Hospital Referral Regions between 1992 and 2003.

Results: Lumbar fusion rates have increased steadily since 1992 (0.3 per 1000 enrollees in 1992 to 1.1 per 1000 enrollees in 2003). Regional rates of lumbar discectomy, laminectomy, and fusion in 1992-1993 were highly correlated to rates of discectomy, laminectomy (R2 = 0.44), and fusion (R2 = 0.28) in 2002-2003. There was a nearly 8-fold variation in regional rates of lumbar discectomy and laminectomy in 2002 and 2003. In the case of lumbar fusion, there was nearly a 20-fold range in rates among Medicare enrollees in 2002 and 2003. This represents the largest coefficient of variation seen with any surgical procedure. Medicare spending for inpatient back surgery more than doubled over the decade. Spending for lumbar fusion increased more than 500%, from 75 million dollars to 482 million dollars. In 1992, lumbar fusion represented 14% of total spending for back surgery; by 2003, lumbar fusion accounted for 47% of spending.

Conclusions: The rate of specific procedures within a region or "surgical signature" is remarkably stable over time. However, there has been a marked increase in rates of fusion, and a coincident shift and increase in cost. Rates of back surgery were not correlated with the per-capita supply of orthopedic and neurosurgeons.

Figure 1

Trends in Rates of Discectomy/Laminectomy and Fusion, 1992–2003

Figure 2

Inpatient Medicare Reimbursements (in millions of dollars) for Back Surgery, 1992–2003

Figure 3

The Relationship between Rates of Lumbar Discectomy/Laminectomy and Lumbar Fusion, 2002–03

Figure 4

The Relationship between Changes in Rates of Lumbar Discectomy/Laminectomy and Lumbar Fusion, 1992–93 to 2002–03.

Figure 5

The Relationship Between Rates of Lumbar Discectomy/Laminectomy in 1992–93 and 2002–03 The 45 degree line represents equality between rates; if the dot representing an HRR is located above the line, enrollees in that HRR experienced higher rates of utilization in 2002–03 than in 1992–93.

Figure 6

The Relationship Between Rates of Lumbar Fusion in 1992–93 and 2002–03 The 45 degree line represents equality between rates; if the dot representing an HRR is located above the line, enrollees in that HRR experienced higher rates of utilization in 2002–03 than in 1992–93.

Figure 7

The Relationship Between Orthopedic Surgeons per 100,000 Residents (1999) and Rates of Back Surgery (1998–99)

Figure 8

The Relationship Between Neurosurgeons per 100,000 Residents (1999) and Rates of Back Surgery (1998–99)

Figure 9

Comparative magnitude of variability of orthopaedic procedures

Map 1. Lumbar Discectomy and Laminectomy

In 79 hospital referral regions, rates of lumbar discectomy and laminectomy were at least 30% higher than the United States average of 2.1 per 1,000 Medicare enrollees. In 55 hospital referral regions, rates were more than 25% lower than the national average.

Map 2. Lumbar Fusion

In 80 hospital referral regions, rates of lumbar fusion were at least 30% higher than the United States average of 1.0 per 1,000 Medicare enrollees. In 98 hospital referral regions, rates were more than 25% lower than the national average.