Abstract
BACKGROUND CONTEXT
Current bundled payment programs in spine surgery, such as the bundled payment for
care improvement rely on the use of diagnosis-related groups (DRG) to define payments.
However, these DRGs may not be adequate enough to appropriately capture the large
amount of variation seen in spine procedures. For example, DRG 459 (spinal fusion
except cervical with major comorbidity or complication) and DRG 460 (spinal fusion
except cervical without major comorbidity or complication) do not differentiate between
the type of fusion (anterior or posterior), the levels/extent of fusion, the use of
interbody/graft/BMP, indication of surgery (primary vs. revision) or even if the surgery
was being performed for a vertebral fracture.
PURPOSE
We carried out a comprehensive analysis to report the factors responsible for cost-variation
in a bundled payment model for spinal fusions.
STUDY DESIGN
Retrospective review of a 5% national sample of Medicare claims from 2008 to 2014
(SAF5).
OUTCOME MEASURES
To understand the independent marginal cost impact of various patient-level, geographic-level,
and procedure-level characteristics on 90-day costs for patients undergoing spinal
fusions under DRG 459 and 460.
METHODS
The 2008 to 2014 Medicare 5% standard analytical files (SAF) were used to retrieve
patients undergoing spinal fusions under DRG 459 and DRG 460 only. Patients with missing
gender, age, and/or state-level data were excluded. Only those patients who had complete
data, with regard to payments/costs/reimbursements, starting from day 0 of surgery
up to 90 days postoperatively were included to prevent erroneous collection. Multivariate
linear regression models were built to assess the independent marginal cost impact
(decrease/increase) of each patient-level, state-level, and procedure-level characteristics
on the average 90-day cost while controlling for other covariates.
RESULTS
A total of 21,367 patients (DRG-460=20,154; DRG-459=1,213) were included in the study.
The average 90-day cost for all lumbar fusions was $31,716±$18,124, with the individual
90-day payments being $54,607±$30,643 (DRG-459) and $30,338±$16,074 (DRG-460). Increasing
age was associated with significant marginal increases in 90-day payments (70–74 years:
+$2,387, 75–79 years: +$3,389, 80–84 years: +$2,872, ≥85: +$1,627). With regards to
procedure-level factors—undergoing an anterior fusion (+$3,118), >3 level fusion (+$5,648)
vs. 1 to 3 level fusion, use of interbody device (+$581), intraoperative neuromonitoring
(+$1,413), concurrent decompression (+$768) and undergoing surgery for thoracolumbar
fracture (+$6,169) were associated with higher 90-day costs. Most individual comorbidities
were associated with higher 90-day costs, with malnutrition (+$12,264), CVA/stroke
(+$5,886), Alzheimer's (+$4,968), Parkinson's disease (+$4,415), and coagulopathy (+$3,810) having the highest marginal 90-day cost-increases. The top five states with
the highest marginal cost-increase, in comparison to Michigan (reference), were Maryland
(+$12,657), Alaska (+$11,292), California (+$10,040), Massachusetts (+$8,800), and
the District of Columbia (+$8,315).
CONCLUSIONS
Under the proposed DRG-based bundled payment model, providers would be reimbursed
the same amount for lumbar fusions regardless of the surgical approach (posterior
vs. anterior), the extent of fusion (1–3 level vs. >3 level), use of adjunct procedures
(decompressions) and cause/indication of surgery (fracture vs. degenerative pathology),
despite each of these factors having different resource utilization and associated
costs. When defining and developing future bundled payments for spinal fusions, health-policy
makers should strive to account for the individual patient-level, state-level, and
procedure-level variation seen within DRGs to prevent the creation of a financial
dis-incentive in taking care of sicker patients and/or performing more extensive complex
spinal fusions.
Keywords
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Article info
Publication history
Published online: May 21, 2019
Accepted:
April 17,
2019
Received in revised form:
March 5,
2019
Received:
January 24,
2019
Footnotes
FDA device/drug status: Not applicable.
Author disclosures: ATM: Nothing to disclose. FMP: Royalties: Nuvasive, Stryker, DePuy, Medtronic; Stock Ownership: Nuvasive, Theracell, SI-Bone, Expanding Orthopaedics, Providence, CarboFix. EY: Grants: Morley Research Foundation (B), Spinal Kinetics (C). SNK: Grants: Spinal Kinetics (C).
Identification
Copyright
© 2019 Elsevier Inc. All rights reserved.
