SPINE Volume 40, Number 7, pp 500-504 ©2015, Wolters Kluwer Health, Inc. All rights reserved.
SURGERY
Obesity Is Associated With an Increased Rate of Incidental Durotomy in Lumbar Spine Surgery Christopher A. Burks, MD, Brian C. Werner, MD, Scott Yang, MD, and Adam L. Shimer, MD
Study Design. Retrospective database analysis. Objective. To determine the impact of obesity on the rate of incidental durotomy in lumbar spine surgery. Summary of Background Data. There is a paucity of data on the overall impact of obesity on the rate of incidental durotomy in lumbar spine surgery, specifically with regard to the type of procedure performed. Methods. A large administrative database was queried for all patients who underwent lumbar spine surgery for decompression and/or fusion. They were then stratified into separate cohorts on the basis of body mass index and by procedural codes. Documentation of incidental durotomy was noted. Patient demographics and associated comorbidities were assessed. Odds ratios and 95% confidence intervals were calculated and χ2 test was used to assess for statistical significance. Results. The incidental durotomy ranged from 0.5% to 2.6%, with the highest rates observed in multilevel laminectomies and revision decompressions in the obese and morbidly obese groups. For patients who underwent decompression only procedures, nonobese patients had a significantly lower rate of durotomy than the obese and morbidly obese cohorts. For patients who underwent fusion with or without decompression, there was a significantly increased rate of durotomy in obese patients compared with nonobese patients. The morbidly obese cohort also had significantly higher rates of incidental durotomy than the nonobese cohort in both revision decompression and revision fusion procedures. Conclusion. This analysis of a large administrative database demonstrates that obesity is associated with increased rates of incidental durotomy in lumbar spine surgery. Furthermore, obesity, in association with increasing complexity of the procedure, increases
From the Department of Orthopaedic Surgery, University of Virginia, Charlottesville, VA. Acknowledgment date: September 29, 2014. Revision date: January 3, 2015. Acceptance date: January 13, 2015. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. Relevant financial activities outside the submitted work: consultancy, grants, payment for lectures. Address correspondence and reprint requests to Adam L. Shimer, MD, Department of Orthopaedic Surgery, University of Virginia, PO Box 800159, Charlottesville, VA 22908; E-mail: [email protected] DOI: 10.1097/BRS.0000000000000784
500
the rate of incidental durotomy in lumbar spine surgery. Surgeons must be aware of these increased risks as the rate of obesity increases in the population. Key words: obesity, morbid obesity, body mass index, durotomy, dural tear, cerebrospinal fluid leak, lumbar spine surgery, risk factor, incidence, complication, database. Level of Evidence: 3 Spine 2015;40:500–504
O
besity has been associated with increased operative time, blood loss, length of stay, hospital costs, reoperation rates, infections, deep vein thrombosis, pulmonary embolism, mortality, and incidence of postoperative visual loss in spine surgery.1–10 Incidental durotomy during spine surgery is a common intraoperative complication, with a reported incidence ranging from 0% to 35%.11–22 Risk factors for incidental durotomy include older age, revision surgery, prior local radiation, type of surgery, experience level of the surgeon, and pre-existing conditions such as diabetes and inflammatory conditions.12,19–21,23–26 Most dural tears identified and managed with direct or indirect repair at the time of surgery are associated with no long-term sequelae; however, in rare occasions, they may cause persistent cerebrospinal fluid leak, neurological deficit, meningocele, durocutaneous fistula, meningitis, arachnoiditis, chronic pain, and sepsis.14 The impact of body mass index (BMI) on the incidence of incidental durotomy is unknown, with multiple studies showing conflicting data. Many of the studies assessing complications associated with obesity in spine surgery have not included incidental durotomy as a complication or have lacked sufficient numbers to detect an effect. To date, no large population-based study has assessed the effect of obesity on the rate of incidental durotomy in lumbar spine surgery. The objective of this study is to use a national database to assess the effect of obesity on the incidence of durotomy during commonly performed lumbar spine procedures.
MATERIALS AND METHODS All data were derived from a for-fee database of patients, the PearlDiver Patient Records Database (www.pearldiverinc .com; PearlDiver Inc, Fort Wayne, IN). The database contains procedure volumes, demographics, and average charge information for patients with International Classification of
www.spinejournal.com
April 2015
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited. SPINE141282_LR 500
12/03/15 4:31 PM
SURGERY
Obesity and Incidental Durotomy • Burks et al
Diseases, Ninth Revision (ICD-9) diagnoses and procedures or Current Procedural Terminology (CPT) codes. Data for the present study were derived from 2 databases within the PearlDiver database: a private-payer database and a Medicare-based database. The private-payer database has its largest contribution from UnitedHealth Group (Decatur, IL), with more than 30 million individual patient records from 2007 to 2011. The Medicare database has more than 100 million individual patient records from 2005 to 2011. To prevent overlap of patients between the 2 databases or counting patients who used both private and Medicare insurances for a single procedure, all patients from the privatepayer database were restricted to age less than 65 years, and all patients from the Medicare database were restricted to age greater than 65 years. Access to the database was granted by PearlDiver Technologies for the purpose of academic research. The database was stored on a password-protected server maintained by PearlDiver. The database was queried for various lumbar spine surgical procedures by CPT code, creating 8 surgical cohorts that were broadly classified as (1) decompression alone, (2) fusion with or without decompression, and (3) revision surgery. For each surgical cohort of interest, patients with only the procedures of interest were isolated by excluding patients with any other CPT spine surgical CPT code. For example, in “decompression alone” cohorts, patients with any fusion, revision, or other relevant spine CPT code were excluded. Table 1 lists the CPT codes used for each of the surgical procedure cohort.
TABLE 1. Summary of ICD-9 and CPT Codes Description
CPT/ICD-9 Code
Procedural groups Decompression overall
CPTs 63001, 63003, 63005, 63011, 63012, 63017, 63030, 63035, 63047, 63056
1-level hemilaminotomy
CPT 63030 not 63035
1-level laminectomy
CPT 63047 not 63048
2+ level hemilaminotomy
CPT 63030 and 63035
2+ level laminectomy
CPT 63047 and 63048
Posterior fusion
CPTs 22612, 22630, 22633, 22842, 22843, 22844
Revision decompression
CPTs 63042, 63044
Revision fusion
CPTs 22830, 22852
Diagnosis codes Obesity (BMI 30–40)
ICD-9s 278.00, V85.30– V85.39
Morbid obesity (BMI 40+)
ICD-9s 278.01, V85.40– V85.49
Dural tear
ICD-9s 349.31, 349.39
CPT indicates Current Procedural Terminology; ICD-9, International Classification of Diseases, Ninth Revision; BMI, body mass index.
Spine
Each of the 8 surgical cohorts was then stratified as nonobese, obese, or morbidly obese on the basis of ICD-9 coding. Obese patients were defined by the ICD-9 code for obesity (278.00) and/or ICD-9 codes for BMI between 30 and 40 kg/m2 (V85.30-V85.39). Morbidly obese patients were defined by the ICD-9 code for morbid obesity (278.01) and/or ICD-9 codes for BMI greater than 40 kg/m2 (V85.41-V85.45). The incidence of intraoperative durotomy was then assessed for each of the cohorts using the ICD-9 for durotomy (349.31, 349.39) at the same time as surgery. The nonobese, obese, and morbidly obese cohorts for the overall patient population were queried for basic demographics including sex, age, smoking status, and numerous medical comorbidities, including diabetes mellitus, obstructive sleep apnea, hyperlipidemia, hypertension, peripheral vascular disease, congestive heart failure, coronary artery disease, chronic kidney disease, chronic lung disease, and chronic liver disease, using ICD-9 codes for each disease. Odds ratios (ORs) and 95% confidence intervals were calculated for each comparison between cohorts. Chi square tests were calculated to determine statistical significance, with P value of less than 0.05 considered as significant.
RESULTS A comparison of patient characteristics in each of the nonobese, obese, and morbidly obese groups demonstrated a higher proportion of female patients and higher rates of all chronic medical comorbidities queried in the morbidly obese and obese versus nonobese groups (Table 2). Overall, the rate of incidental durotomy ranged from 0.5% to 2.6%, with the highest rates observed for 2+ level laminectomies and revision decompressions in the obese and morbidly obese groups (1.7%–2.6%). Nonobese patients had a less than 1% incidental durotomy rate except with more involved surgical procedures, including 2+ level laminectomy, fusion with or without decompression, or revision surgery (Table 3). For patients who underwent lumbar spinal decompression surgery, the rate of incidental durotomy was significantly increased in the morbidly obese versus nonobese groups (OR = 1.75, P < 0.0001), the obese versus nonobese groups (OR = 1.34, P < 0.0001), and the morbidly obese versus obese groups (OR = 1.30, P = 0.02). Statistically significant increases in durotomy rates were noted for multiple decompression subcategories in the morbidly obese versus nonobese groups and the obese versus nonobese groups (Table 4). For patients who underwent lumbar spinal fusion with or without decompression, the rate of incidental durotomy was significantly increased in the obese versus nonobese groups (OR = 1.26, P = 0.018). A trend toward increased incidental durotomy rates was noted in the morbidly obese compared with the nonobese groups (OR = 1.25, P = 0.074) (Table 4). For patients who underwent revision lumbar decompression, the rate of incidental durotomy was significantly higher in the morbidly obese versus nonobese groups (OR = 1.59, P = 0.04) and obese versus nonobese groups (OR = 1.47, P = 0.02). The rate of incidental durotomy was also significantly www.spinejournal.com
501
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited. SPINE141282_LR 501
12/03/15 4:31 PM
SURGERY
Obesity and Incidental Durotomy • Burks et al
TABLE 2. Comparison of Cohorts: All Spine
Procedures
Nonobese
Obese
Morbidly Obese
245,439
36,196
16,244
Female
48.2%
56.5%
62.4%
Male
51.8%
43.5%
37.6%
Age
SURGERY
Obesity Is Associated With an Increased Rate of Incidental Durotomy in Lumbar Spine Surgery Christopher A. Burks, MD, Brian C. Werner, MD, Scott Yang, MD, and Adam L. Shimer, MD
Study Design. Retrospective database analysis. Objective. To determine the impact of obesity on the rate of incidental durotomy in lumbar spine surgery. Summary of Background Data. There is a paucity of data on the overall impact of obesity on the rate of incidental durotomy in lumbar spine surgery, specifically with regard to the type of procedure performed. Methods. A large administrative database was queried for all patients who underwent lumbar spine surgery for decompression and/or fusion. They were then stratified into separate cohorts on the basis of body mass index and by procedural codes. Documentation of incidental durotomy was noted. Patient demographics and associated comorbidities were assessed. Odds ratios and 95% confidence intervals were calculated and χ2 test was used to assess for statistical significance. Results. The incidental durotomy ranged from 0.5% to 2.6%, with the highest rates observed in multilevel laminectomies and revision decompressions in the obese and morbidly obese groups. For patients who underwent decompression only procedures, nonobese patients had a significantly lower rate of durotomy than the obese and morbidly obese cohorts. For patients who underwent fusion with or without decompression, there was a significantly increased rate of durotomy in obese patients compared with nonobese patients. The morbidly obese cohort also had significantly higher rates of incidental durotomy than the nonobese cohort in both revision decompression and revision fusion procedures. Conclusion. This analysis of a large administrative database demonstrates that obesity is associated with increased rates of incidental durotomy in lumbar spine surgery. Furthermore, obesity, in association with increasing complexity of the procedure, increases
From the Department of Orthopaedic Surgery, University of Virginia, Charlottesville, VA. Acknowledgment date: September 29, 2014. Revision date: January 3, 2015. Acceptance date: January 13, 2015. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. Relevant financial activities outside the submitted work: consultancy, grants, payment for lectures. Address correspondence and reprint requests to Adam L. Shimer, MD, Department of Orthopaedic Surgery, University of Virginia, PO Box 800159, Charlottesville, VA 22908; E-mail: [email protected] DOI: 10.1097/BRS.0000000000000784
500
the rate of incidental durotomy in lumbar spine surgery. Surgeons must be aware of these increased risks as the rate of obesity increases in the population. Key words: obesity, morbid obesity, body mass index, durotomy, dural tear, cerebrospinal fluid leak, lumbar spine surgery, risk factor, incidence, complication, database. Level of Evidence: 3 Spine 2015;40:500–504
O
besity has been associated with increased operative time, blood loss, length of stay, hospital costs, reoperation rates, infections, deep vein thrombosis, pulmonary embolism, mortality, and incidence of postoperative visual loss in spine surgery.1–10 Incidental durotomy during spine surgery is a common intraoperative complication, with a reported incidence ranging from 0% to 35%.11–22 Risk factors for incidental durotomy include older age, revision surgery, prior local radiation, type of surgery, experience level of the surgeon, and pre-existing conditions such as diabetes and inflammatory conditions.12,19–21,23–26 Most dural tears identified and managed with direct or indirect repair at the time of surgery are associated with no long-term sequelae; however, in rare occasions, they may cause persistent cerebrospinal fluid leak, neurological deficit, meningocele, durocutaneous fistula, meningitis, arachnoiditis, chronic pain, and sepsis.14 The impact of body mass index (BMI) on the incidence of incidental durotomy is unknown, with multiple studies showing conflicting data. Many of the studies assessing complications associated with obesity in spine surgery have not included incidental durotomy as a complication or have lacked sufficient numbers to detect an effect. To date, no large population-based study has assessed the effect of obesity on the rate of incidental durotomy in lumbar spine surgery. The objective of this study is to use a national database to assess the effect of obesity on the incidence of durotomy during commonly performed lumbar spine procedures.
MATERIALS AND METHODS All data were derived from a for-fee database of patients, the PearlDiver Patient Records Database (www.pearldiverinc .com; PearlDiver Inc, Fort Wayne, IN). The database contains procedure volumes, demographics, and average charge information for patients with International Classification of
www.spinejournal.com
April 2015
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited. SPINE141282_LR 500
12/03/15 4:31 PM
SURGERY
Obesity and Incidental Durotomy • Burks et al
Diseases, Ninth Revision (ICD-9) diagnoses and procedures or Current Procedural Terminology (CPT) codes. Data for the present study were derived from 2 databases within the PearlDiver database: a private-payer database and a Medicare-based database. The private-payer database has its largest contribution from UnitedHealth Group (Decatur, IL), with more than 30 million individual patient records from 2007 to 2011. The Medicare database has more than 100 million individual patient records from 2005 to 2011. To prevent overlap of patients between the 2 databases or counting patients who used both private and Medicare insurances for a single procedure, all patients from the privatepayer database were restricted to age less than 65 years, and all patients from the Medicare database were restricted to age greater than 65 years. Access to the database was granted by PearlDiver Technologies for the purpose of academic research. The database was stored on a password-protected server maintained by PearlDiver. The database was queried for various lumbar spine surgical procedures by CPT code, creating 8 surgical cohorts that were broadly classified as (1) decompression alone, (2) fusion with or without decompression, and (3) revision surgery. For each surgical cohort of interest, patients with only the procedures of interest were isolated by excluding patients with any other CPT spine surgical CPT code. For example, in “decompression alone” cohorts, patients with any fusion, revision, or other relevant spine CPT code were excluded. Table 1 lists the CPT codes used for each of the surgical procedure cohort.
TABLE 1. Summary of ICD-9 and CPT Codes Description
CPT/ICD-9 Code
Procedural groups Decompression overall
CPTs 63001, 63003, 63005, 63011, 63012, 63017, 63030, 63035, 63047, 63056
1-level hemilaminotomy
CPT 63030 not 63035
1-level laminectomy
CPT 63047 not 63048
2+ level hemilaminotomy
CPT 63030 and 63035
2+ level laminectomy
CPT 63047 and 63048
Posterior fusion
CPTs 22612, 22630, 22633, 22842, 22843, 22844
Revision decompression
CPTs 63042, 63044
Revision fusion
CPTs 22830, 22852
Diagnosis codes Obesity (BMI 30–40)
ICD-9s 278.00, V85.30– V85.39
Morbid obesity (BMI 40+)
ICD-9s 278.01, V85.40– V85.49
Dural tear
ICD-9s 349.31, 349.39
CPT indicates Current Procedural Terminology; ICD-9, International Classification of Diseases, Ninth Revision; BMI, body mass index.
Spine
Each of the 8 surgical cohorts was then stratified as nonobese, obese, or morbidly obese on the basis of ICD-9 coding. Obese patients were defined by the ICD-9 code for obesity (278.00) and/or ICD-9 codes for BMI between 30 and 40 kg/m2 (V85.30-V85.39). Morbidly obese patients were defined by the ICD-9 code for morbid obesity (278.01) and/or ICD-9 codes for BMI greater than 40 kg/m2 (V85.41-V85.45). The incidence of intraoperative durotomy was then assessed for each of the cohorts using the ICD-9 for durotomy (349.31, 349.39) at the same time as surgery. The nonobese, obese, and morbidly obese cohorts for the overall patient population were queried for basic demographics including sex, age, smoking status, and numerous medical comorbidities, including diabetes mellitus, obstructive sleep apnea, hyperlipidemia, hypertension, peripheral vascular disease, congestive heart failure, coronary artery disease, chronic kidney disease, chronic lung disease, and chronic liver disease, using ICD-9 codes for each disease. Odds ratios (ORs) and 95% confidence intervals were calculated for each comparison between cohorts. Chi square tests were calculated to determine statistical significance, with P value of less than 0.05 considered as significant.
RESULTS A comparison of patient characteristics in each of the nonobese, obese, and morbidly obese groups demonstrated a higher proportion of female patients and higher rates of all chronic medical comorbidities queried in the morbidly obese and obese versus nonobese groups (Table 2). Overall, the rate of incidental durotomy ranged from 0.5% to 2.6%, with the highest rates observed for 2+ level laminectomies and revision decompressions in the obese and morbidly obese groups (1.7%–2.6%). Nonobese patients had a less than 1% incidental durotomy rate except with more involved surgical procedures, including 2+ level laminectomy, fusion with or without decompression, or revision surgery (Table 3). For patients who underwent lumbar spinal decompression surgery, the rate of incidental durotomy was significantly increased in the morbidly obese versus nonobese groups (OR = 1.75, P < 0.0001), the obese versus nonobese groups (OR = 1.34, P < 0.0001), and the morbidly obese versus obese groups (OR = 1.30, P = 0.02). Statistically significant increases in durotomy rates were noted for multiple decompression subcategories in the morbidly obese versus nonobese groups and the obese versus nonobese groups (Table 4). For patients who underwent lumbar spinal fusion with or without decompression, the rate of incidental durotomy was significantly increased in the obese versus nonobese groups (OR = 1.26, P = 0.018). A trend toward increased incidental durotomy rates was noted in the morbidly obese compared with the nonobese groups (OR = 1.25, P = 0.074) (Table 4). For patients who underwent revision lumbar decompression, the rate of incidental durotomy was significantly higher in the morbidly obese versus nonobese groups (OR = 1.59, P = 0.04) and obese versus nonobese groups (OR = 1.47, P = 0.02). The rate of incidental durotomy was also significantly www.spinejournal.com
501
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited. SPINE141282_LR 501
12/03/15 4:31 PM
SURGERY
Obesity and Incidental Durotomy • Burks et al
TABLE 2. Comparison of Cohorts: All Spine
Procedures
Nonobese
Obese
Morbidly Obese
245,439
36,196
16,244
Female
48.2%
56.5%
62.4%
Male
51.8%
43.5%
37.6%
Age
