Economic impact of comorbidities in spine surgery

Clinical article

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Comorbidities in patients undergoing spine surgery may reasonably be factors that increase health care costs. To verify this hypothesis, the authors conducted the following study.


Major comorbidities and age-adjusted Charlson Comorbidity Index scores were retrospectively analyzed for 816 patients who underwent spine surgery at the authors' institutions between 2005 and 2008, and treatment costs (hospital charges) were assessed with the help of statistical software. The sample was collected by a nonmedical staff (hired at the beginning of 2006). Patients underwent one of the three most common types of spine surgery: lumbar microdiscectomy (20.5%), anterior cervical decompression and fusion (ACDF; 60.3%), or lumbar decompression and fusion (LDF; 19.2%). Patients were nearly equally divided by sex (53% were female and 47% male), and 78% were Caucasian versus 21% who were African American; the rest were of mixed or unidentified race. The average age was 54 years, with an SD of ± 14 years.


There were significant differences in the prevalence of major comorbidities between male and female and between severely obese and nonseverely obese patients. The impact of comorbidities on the cost of spine surgery was more prominent in older patients, and an additive effect from some comorbidities was recorded in various types of spine surgery. For instance, in the ACDF group, female patients with both severe obesity and diabetes mellitus (DM) had significantly higher hospital charges than those with only one or neither of these conditions ($34,943 for both severe obesity and DM vs $25,633 for severe obesity only; $25,826 for DM only; and $25,153 for those with neither condition [p < 0.05]). In the LDF group, female patients with both DM and a history of depression had significantly higher hospital charges than those with only one or neither of these conditions ($65,782 for both DM and depression vs $53,504 for DM only; $55,990 for depression only; and $52,249 for those with neither condition [p < 0.05]). A significant difference was also found in hospital cost ($16,472 [p < 0.01]; 32% increase over baseline) in the LDF group between patients with the lowest and highest scores on the Charlson Index.


Comorbidities additively increase hospital costs for patients who undergo spine surgery, and should be considered in payment arrangements.

Abbreviations used in this paper: ACDF = anterior cervical decompression and fusion; BMI = body mass index; CABG = coronary artery bypass graft; DM = diabetes mellitus; DRG = Diagnosis-Related Group; LDF = lumbar decompression and fusion; LMD = lumbar microdiscectomy.

Article Information

Address correspondence to: M. Sami Walid, M.D., Ph.D., Medical Center of Central Georgia, Macon, Georgia 31201. email:

Please include this information when citing this paper: published online January 14, 2011; DOI: 10.3171/2010.11.SPINE10139.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Boxplot showing the dates of discharge of the patients in the study sample. The circles represent outliers, and the asterisks denote extreme values. ToS = type of surgery.

  • View in gallery

    Bar graph showing the impact of a history of CABG or stent surgery on hospital charges of LDF in younger and older male and female patients. Error bars represent ± 1 SD. HCost = hospital cost.

  • View in gallery

    Bar graph showing the additive effect of severe obesity and DM on hospital charges in patients who underwent ACDF.

  • View in gallery

    Bar graph showing the additive effect of DM and history of depression on hospital charges in female patients who underwent LDF.

  • View in gallery

    Bar graph showing length of stay per type of surgery, patient's sex, and Charlson Comorbidity Index score. The numbers on the y axis and also those above each bar represent the number of days in the hospital stay.



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