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BACKGROUND CONTEXT
Current bundled-payment programs in spine surgery, such as the BCPI, 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 instance, 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/SETTING
Retrospective review of a 5% national sample of Medicare claims from 2008-2014 (SAF5).
PATIENT SAMPLE
The 2008-2014 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.
OUTCOME MEASURES
All payments made to service providers (surgeon, anesthesiologists and post-acute
care) starting from day 0 of surgery up to 90-days postoperatively were used to calculate
90-day costs.
METHODS
Multivariate linear regression models were built to assess the independent marginal
cost impact (decrease/increase) of each patient-level, state-level and procedure-level
characteristic 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
(70-74y: + $2,387, 75-79y: + $3,389, 80-84y: + $2,872, ≥85: + $1,627). With regards
to procedure-level factors – undergoing an anterior fusion (+ $3,118), >3 level fusion
(+ $5,648) vs 1-3 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 (+ $4,415) and coagulopathy (+ $3,810)
having the highest marginal 90-day cost-increases. The top 5 states with the highest
marginal cost-increase, in comparison to the study population average, were Maryland
(+ $12,657), Alaska (+ $11,292), California (+ $10,040), Massachusetts (+ $8,800)
and DC (+ $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.
FDA DEVICE/DRUG STATUS
This abstract does not discuss or include any applicable devices or drugs.
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© 2019 Published by Elsevier Inc.
