Impact of Complications on DRG Assignment for Adult Spinal Deformity Surgery Using the ISSG-AO Classification System

Abstract

Study design: Retrospective cohort.

Objective: The ISSG-AO Spinal Deformity Complication Classification System (SDCCS) predicts Diagnosis Related Group (DRG) coding and cost.

Background: Inconsistent definitions of complications contribute to variation in reported surgical complication rates. Incorrect complication reporting can lead to over or under DRG reimbursement. The ISSG-AO SDCCS provides improved complication reporting reproducibility and may help predict complication costs.

Methods: ASD patients were grouped into: DRG without complication or comorbidity (CC) or Major CC (MCC) (DRGs 455 & 458), with CC (DRGs 454 & 457), and with MCC (DRGs 453 & 456). Complications were graded by intervention severity per ISSG-AO system: grade 0 (none), 1 (mild-e.g., med change), 2 (moderate-e.g., ICU), 3 (severe-e.g., reoperation). Cost were based on Medicare inpatient prospective payment system (IPSS, Medicare Allowable rate). A multinomial logistic model identified key predictors of DRG assignment by complication grades.

Results: Of the 675 patients, 14% were in DRGs without CC/MCC, 71% in DRGs with CC, and 15% were DRGs with MCC. Patients with complications requiring intervention mostly fell into the higher DRG categories (97%). Patients who received an intervention are approximately 6.75 (2.01-22.75, P<.0021) times more likely to be classified under DRG with CC and 15.72 (95% CI, 4.23-58.45, P<.0001) times more likely to be classified with DRG with MCC compared to those who did not receive an intervention. Each unit increase in Edmonton Frailty Score raises the odds of being in DRG with MCC by 1.24 (95% CI 1.04-1.48, P 0.017). Similar trends were seen for OR time and LOS. Reimbursement showed incremental increase from $49.5K to $56K to $70K across DRG categories.

Conclusions: Patients with elevated ISSG-AO scores are more likely to be categorized into higher DRGs, experience extended lengths of stay and generate greater healthcare expenditures. The ISSG-AO SDCCS predicts DRG thereby helping standardize complication reporting.

Keywords: DRG; ISSG-AO classification system; United States; adult spinal deformity; costs and cost-analysis; healthcare economics; medicare; retrospective studies; spine surgery outcomes; surgical complications.