Cost and quality of life outcome analysis of postoperative infections after posterior lumbar decompression and fusion

Journal of Clinical Neuroscience xxx (xxxx) xxx

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Clinical study

Cost and quality of life outcome analysis of postoperative infections after posterior lumbar decompression and fusion Zach Pennington a, Swetha J. Sundar b, Daniel Lubelski a, Matthew D. Alvin c, Edward C. Benzel d,e,f, Thomas E. Mroz d,e,f,⇑ a

Department of Neurosurgery, Johns Hopkins School of Medicine, Baltimore, MD, USA Department of Plastic and Reconstructive Surgery, Case Western University School of Medicine, Cleveland, OH, USA Department of Diagnostic Radiology, Johns Hopkins School of Medicine, Baltimore, MD, USA d Cleveland Clinic Center for Spine Health, Cleveland Clinic, Cleveland, OH, USA e Cleveland Clinic Lerner College of Medicine, Cleveland, OH, USA f Department of Neurological Surgery, Cleveland Clinic, Cleveland, OH, USA b c

a r t i c l e

i n f o

Article history: Received 14 April 2019 Accepted 5 July 2019 Available online xxxx Keywords: Postoperative infection Lumbar fusion Cost effectiveness Quality of life Outcomes Wound infection

a b s t r a c t Surgical site infections (SSI) following spine procedures are serious and costly complications that may reduce patient quality of life (QOL). Deep SSIs may also extend hospitalizations and require surgical debridement or antibiotic therapy, increasing costs to both patients and the healthcare system. Here we sought to evaluate the effect of deep SSI on care cost and QOL outcomes in patients undergoing posterior lumbar decompression and fusion. To do so we performed a retrospective study of patients undergoing lumbar decompression and fusion between 2008 and 2012. Patients experiencing postoperative deep SSI were matched to controls not experiencing a deep SSI. Included patients had prospectivelygathered QOL outcome measures collected preoperatively and at 6 months postoperatively. Health resource utilization was recorded from patient electronic medical records over the 6-month follow-up. Direct costs were estimated using Medicare national payment amounts. Indirect costs were based on missed work days and patient income. We found both cohorts experienced significant improvements in QOL scores following surgery, and there were no significant differences between the cohorts. The average total cost was significantly higher in the infected cohort compared to controls ($37,009 vs. $16,227; p < 0.0001). Compared to controls, patients experiencing deep SSI had greater costs in each of the following categories: hospitalizations (p < 0.01), office visits (p = 0.03), imaging (p < 0.01), and medications (p < 0.01). Among those experiencing deep SSI, there are significant increases in costs, with minimal long-term impact on QOL outcomes as compared with controls at the six-month follow-up. Ó 2019 Elsevier Ltd. All rights reserved.

1. Introduction Surgical site infections (SSIs) are an uncommon, but potentially devastating postoperative complication seen in 2–13% of patients undergoing posterior lumbar spine surgery [1–4]. Given the rising Abbreviations: BDI, Beck Depression Inventory; COMI, Core Outcome Measures Index; EMR, Electronic medical record; EQ-5D, EuroQol 5-Dimensions; HADS, Hospital Anxiety and Depression Scale; NRS, Numerical Rating Scale [of pain]; PDQ, Pain/Disability Questionnaire; PHQ-9, Pain Health Questionnaire; PRO, Patientreported outcome; QOL, Quality of life; SF-36, 36-item Short Form Health Survey; SSI, Surgical site infection; TLIF, Transforaminal lumbar interbody fusion; VAS, Visual analog scale. ⇑ Corresponding author at: Center for Spine Health, 9500 Euclid Avenue, Suite S80, Cleveland, OH 44195, USA. E-mail address: [email protected] (T.E. Mroz).

rates of spinal fusion procedures [5] it is estimated that upwards of 30,000 patients will experience an SSI annually. Consequently, it is incumbent upon the spine surgical community to identify the risk factors for these infections, the interventions capable of reducing their occurrence, and the long-term effects that they have on patients clinical and financial well-being. Furthermore, it is essential to quantify the costs of SSI to the healthcare system to help define the extent to which payors can and should invest in prophylaxis against SSI. Multiple studies have identified risk factors that predispose patients to experience SSI, including obesity, diabetes, smoking history, extended preoperative hospitalization, and previous spine surgery [2,4,6–8]. Similar, many studies, including several randomized controlled trials [9,10], have been published

https://doi.org/10.1016/j.jocn.2019.07.025 0967-5868/Ó 2019 Elsevier Ltd. All rights reserved.

Please cite this article as: Z. Pennington, S. J. Sundar, D. Lubelski et al., Cost and quality of life outcome analysis of postoperative infections after posterior lumbar decompression and fusion, Journal of Clinical Neuroscience, https://doi.org/10.1016/j.jocn.2019.07.025

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2. Methods

The EQ-5D is a validated questionnaire that measures multiple aspects of the patients’ QOL [20]. The pain disability questionnaire (PDQ) assesses how pain affects a patient’s ability to function in 15 categories. It is subdivided into functional and psychosocial components, which combine to give a total score with a maximum of 150 points, with higher scores indicating greater levels of disability [21]. Finally, the PHQ-9 is a validated 9-question depression screening tool based on the diagnostic criteria established by the DSM-IV [17]. PHQ-9 scores between 5 and 10 are indicative of minor depression and scores over 10 are indicative of major depression [17]. The MCID used for the EQ-5D, VAS, PDQ, and PHQ-9 at 1 year were 0.14, 2, 26, and 5 respectively [22–26]. In addition to evaluating changes on PROs, we also estimated the quality-adjusted life years (QALYs) gained by patients in the infected and control cohorts. QALYs are a metric used by payors to compare the overall effectiveness of treatments across medical specialties [27]. Here we calculated QALY gain using the formula QALY = (Years of Life)
(Utility Value), where a year in perfect health is assigned a utility value of 1.0 and death is assigned 0.0 [28].

2.1. Demographics

2.3. Cost data

After obtaining IRB approval, we queried the electronic medical records (EMRs) of all patients who underwent posterior lumbar decompression and fusion at our facility between 2008 and 2012. Patients were included if they had a minimum 6-month followup time and experienced a deep wound infection. The occurrence of a deep wound infection was determined according to the Centers for Disease Control (CDC) [15] definition, which classifies deep SSIs as infections occurring within 90 days of surgery that involve deep soft tissues of the incision and which include at least one of the following: purulent drainage from the incision, identification of an abscess or other evidence of wound infection on physical exam or imaging study, or wound dehiscence or purposeful opening of the wound by a care provider with positive cultures and clinical evidence of infection (fever >38 °C or tenderness of the wound site). Patients were excluded if they were younger than 18 years of age or had prior spine surgery complicated by infection. Patients in the infection cohort were individually matched to a cohort of patients that underwent posterior lumbar decompression or fusion, but did not develop deep wound infections. Patients were matched to gender, age ± 5 years, date of surgery, operating surgeon, and BMI ± 5. When possible, we also controlled for identified risks for SSI including hypertension, hyperlipidemia, and diabetes [7]; no significant differences in comorbidities remained between the final cohorts.

Direct healthcare costs were collected from the EMR and included hospital stay, surgery, outpatient visits, imaging, physical and occupational therapy, and medications. Medicare national payment amounts were used to calculate and standardize direct cost data and reflect charges associated with healthcare payers. Direct healthcare costs were calculated based on the primary Diagnosis Related Group (DRG) and national Medicare payment amounts were found in the Ingenix DRG Expert [29]. Current Procedural Terminology (CPT) codes for the original surgery, repeat surgery, outpatient visits, imaging, and therapy were used to calculate costs based on the 2013 physician fee reimbursement schedule obtained from the Center for Medicare and Medicaid Services [30]. Therapy costs included inpatient physical and occupational sessions. Medication costs were calculated from the 2010 Red Book, a pharmaceutical resource detailing costs of drug therapy by specific dosage and route of administration [31]. All antibiotics and analgesics administered post-operatively were considered. Indirect cost was calculated from the median income by patient zip code and self-reported lost days of work [32]. Cost data was standardized using inflation data from the United States Bureau of Labor Statistics [33].

evaluating interventions designed to decrease the rate of SSI. However, few studies exist that have specifically focused on the effect of SSIs on both patient quality of life (QOL) outcomes and healthcare costs [11–14]. Analyzing the impact of SSIs on cost and QOL is important not only to improve patient outcomes, but also to highlight the value of those interventions aimed at preventing SSI, an increasingly important concern given the rising prevalence of quality-based reimbursement. To this end, we decided to evaluate care costs and patient QOL, as assessed by standardized patient-reported outcomes (PROs), in a cohort of patients who underwent posterior lumbar decompression and fusion. We sought to comment on the relative impact of SSI on financial and QOL outcomes. We also hoped to evaluate the degree to which differences in these outcomes should guide investment in prophylaxis against surgical wound infections.

2.2. QOL data The QOL outcome data used in this study included the following standardized PROs: Euro-Qol 5 Dimensions (EQ-5D) [16], Visual Analog Scale (VAS), Patient Health Questionnaire 9 (PHQ-9) [17], and the Patient Disability Questionnaire (PDQ) [18]. The data was obtained via the institutional Knowledge Program (KP), an EMRbased outcomes assessment tool that prospectively compiles patient-reported data gathered at each outpatient visit. Preoperative QOL data was acquired in the 30-days prior to the index operation. Postoperative data was collected at the 6-months follow-up appointment, which was defined as 6-months post-decompression for the non-infected patients and 6-months post-debridement for patients who experienced an SSI. This was done to account for the variability in the time between initial surgery and diagnosis of deep wound infection. The PROs employed in this study have all been previously validated in the spine surgery population [19,20].

2.4. Statistical analysis Data was analyzed using the JMP Pro 10 statistical software (SAS Institute Inc., Cary, North Carolina 2012). Descriptive statistics summarizing patient demographics were presented as means and standard deviations or counts with percent as appropriate. Pre to post-operative changes in outcomes were analyzed with paired ttests and Wilcoxon Signed-Rank tests for parametric and nonparametric data, respectively. The infection and non-infection cohorts were compared with respect to numeric variables using independent sample t-tests and categorical variables using Fisher’s exact tests. All values of p < 0.05 were considered statistically significant. 3. Results 3.1. Patient sample Of the 547 patients that underwent posterior lumbar decompression/fusion, 18 patients (3.3%) developed postoperative deep wound infection (Table 1). The average age of patients in the infection and non-infection cohorts was 58 years and 54 years, respec-

Please cite this article as: Z. Pennington, S. J. Sundar, D. Lubelski et al., Cost and quality of life outcome analysis of postoperative infections after posterior lumbar decompression and fusion, Journal of Clinical Neuroscience, https://doi.org/10.1016/j.jocn.2019.07.025

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Z. Pennington et al. / Journal of Clinical Neuroscience xxx (xxxx) xxx

tively. Both cohorts had 12 men and 6 women. The infection cohort had an average post-infection follow-up time of 6.4 months and the control cohort had an average post-surgery follow up time of 6.1 months. There were no statistically significant differences between the infection and non-infection cohorts for any of the demographic or operative variables collected. 3.2. QOL data Preoperatively, the cohorts were not statistically different in EQ-5D, VAS, PDQ, or PHQ-9 scores (Table 2). At 6 months, both cohorts showed significant improvement on the EQ-5D, PDQ, and VAS (p < 0.01 for all questionnaires). Regarding the PHQ-9, the infection cohort showed statistically significant improvement (p = 0.01) whereas the non-infection cohort trended towards significance (p = 0.08). For the EQ-5D, 53% of infection patients and 71% of non-infection patients achieved the MCID (p = 0.48). Additionally, converting the EQ-5D data, we found that the QALYs gained per 6-month period were 0.10 for patients experiencing post-operative infections and 0.15 for those not experiencing infection; there was no significant difference between these gains. For the VAS, 82% of infection patients and 88% of non-infection patients achieved the MCID (p = 0.99). On the PHQ-9, 57% of infection patients and 43% of non-infection patients achieved the MCID (p = 0.71), and on the PDQ, 67% of infection patients and 40% of non-infection patients achieved the MCID (p = 0.27). There were no significant differences between the two cohorts in the percentage of patients achieving the MCID for any questionnaire at 6 months.

Table 1 Demographic information for infection and non-infection cohorts. Variable

Infection

Non-infection

p valuey

n Age at Surgery Male Gender Body Mass Index (kg/m2) Hyperlipidemia Hypertension Diabetes mellitus Annual Income

18 54.2 ± 15.3 12 (67%) 30.9 ± 4.5 7 (39%) 9 (50%) 2 (11%) $49,694 ± $14,704

18 58.2 ± 15.5 12 (67%) 32.5 ± 5.4 9 (50%) 9 (50%) 3 (17%) $52,678 ± $10,062

0.4 0.99 0.35 0.74 0.99 0.99 0.5

y

Student t test was used for continuous variables and the Fisher exact test was used for categorical variables.

Table 3 Direct, indirect, and total costs.

y

Direct Cost Indirect Cost (MD)à Total Cost§

Infection

Non-infection

p

$35,432 ± $4844 $1669 ± $1024 $37009 ± $5423

$14,992 ± $837 $1589 ± $1104 $16,227 ± $1201

0.0001* 0.92 0.0001*

All costs in 2013 dollars. y Direct cost is the hospital cost, surgeon cost, and postoperative cost combined. à Indirect cost is based on miss work days and average income. § Total cost is the combination of direct and indirect costs. * p-value  0.05.

3.3. Cost data Direct costs were more than twice as high for the infection cohort compared to the control cohort ($35,432 vs. $14,992; p < 0.01) (Table 3). The difference in indirect cost between the two cohorts ($1669 for the infection cohort and $1589 for the non-infection cohort) was not significant (p = 0.92). The average total cost for the infection cohort was $37,009, compared with $16,227 for the non-infection cohort (p < 0.01). Accordingly, the direct cost of a deep wound infection following lumbar fusion and decompression surgery was $20,440. This value includes the additional costs of readmission, surgical debridement, as well as additional outpatient visits, imaging, medication, and therapy. The average cost of the readmission(s) and debridement(s) was $17,099, which was a cost that was only incurred by the infection cohort. Postoperative direct costs, including medications, imaging, therapy and outpatient visits were $4432 for the infection cohort, compared to $1094 for the non-infection cohort (p < 0.01) (Table 4). There were no significant differences in indirect costs (missed work-days) associated with having a postoperative infection (Table 3). Lastly, using the QALY gained per 12-month period (extrapolated from the observed 6-month gains), we found that post-operative SSIs were associated with an increase in the cost per QALY ($185,045 vs. $55,955). 4. Discussion Given the rising number of spine surgeries conducted each year [5], the management of surgical site infections is becoming an increasingly important part of clinical practice of spine surgeons. Though many studies have been conducted to identify risk factors

Table 2 Patient reported outcomes (PROs). Metric

pà

Preop n

Value

EQ-5D Infection Non-infection

17 17

0.36 0.38

VAS Infection Non-infection

17 17

PDQ Infection Non-infection PHQ-9 Infection Non-infection

6 Months

py

pà

n

Value

0.68

18 18

0.56 0.67

0.003* 0.0004*

0.19

7.4 8.0

0.30

17 16

3.6 3.6

0.0008* 0.0003*

0.98

18 17

102 95

0.37

15 16

66 70

0.003* 0.008*

0.77

15 15

12.3 11.1

0.64

14 16

8.4 7.2

0.01* 0.08

0.66

Key: EQ-5D – EuroQol 5-dimension; PDQ – pain/disability questionnaire; PHQ-9 – pain health questionnaire-9; VAS – visual analog scale. Student t test was used to determine significance for differences between infection and non-infection cohorts. y p value for the pre and postoperative PRO values within the cohorts. à p value for the difference between the infection and non-infection cohorts. * p value 0.05 matched pair t test was used to determine significance for postoperative values compared to preoperative values.

Please cite this article as: Z. Pennington, S. J. Sundar, D. Lubelski et al., Cost and quality of life outcome analysis of postoperative infections after posterior lumbar decompression and fusion, Journal of Clinical Neuroscience, https://doi.org/10.1016/j.jocn.2019.07.025

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Z. Pennington et al. / Journal of Clinical Neuroscience xxx (xxxx) xxx

Table 4 Postoperative costs.

y

Medications Therapyà Imaging§ Outpatient visitsk Total

Infection

Non-infection

p value

$1842 ± $833 $959 ± $827 $1275 ± $496 $356 ± $78 $4432 ± $1790

$242 ± $138 $359 ± $126 $249 ± $166 $243 ± $57 $1094 ± $297

0.002* 0.18 0.001* 0.03* 0.001*

All costs in 2013 dollars. y Total medication costs included costs associated with antibiotics and pain management. à Therapy costs include inpatient physical therapy and occupational therapy. § Imaging costs included radiographs, CT scans, and MRIs associated with the lumbar spine and possible infection. k Outpatient visit costs include all outpatient spine visits. * p value 0.05.

for surgical site infection [2,4,6–8] and possible interventions to reduce surgical site infection [9,10], there is a relative paucity of literature describing quality of life outcomes among and direct financial costs to patients who experience this complication. Here we present a study exploring these very outcomes in patients undergoing posterior lumbar decompression and fusion. We find that surgical site infections are associated with a 128% increase in total costs, but do not lead to a significant difference in QOL outcomes. This suggests that while increasing the risk of reoperation and short-term morbidity [34], surgical site infections may not produce long-term reductions in quality of life. 4.1. SSIs and quality of life outcomes The first study to examine the effect of SSIs on long-term QOL outcomes in patients undergoing lumbar fusion was published by Mok et al. [11] Using the 36-item Short-Form Health Survey (SF36) and a mean follow-up of 61mo (minimum 24mo), the authors demonstrated that infection had no significant difference on overall physical or mental health outcomes. Soon thereafter Falavigna et al. [35] published the results of a case-control study comparing changes in scores on the SF-36, Oswestry Disability Index (ODI), Beck Depression Inventory (BDI), Hospital Anxiety and Depression Scale (HADS), and Numerical Rating Scale of pain (NRS) between infected and non-infected patients. Like Mok et al and consistent with our own findings, they found that the degree of improvement seen by infected patients on the NRS, ODI, BDI, HADS, and all domains of the SF-36 was similar to that seen by non-infected, matched controls. Despite this, infected patients reported overall lower satisfaction with the procedure, suggesting that overall satisfaction might be colored by the most negative experience in the episode of care. Subsequently, Petilon et al described QOL outcomes at the 2year follow-up in patients undergoing anterior and/or posterior lumbar fusion using the ODI and SF-36 [14]. Infected patients were noted to be significantly less likely to see an improvement in their back-related disability at 2-years as assessed by the ODI and saw lower overall improvements in their back pain; outcomes on the SF-36 were similar to those of non-infected controls. Similar findings have been made in other spine populations, including patients undergoing surgical correction of adolescent idiopathic scoliosis [36], adult spinal deformity [12,37], and posterior cervical fusion [13]. Glassman et al. [37], Kuhns et al. [13] and Rihn et al. [36] all failed to find differences in QOL outcomes between infected and non-infected groups. Additionally, although Haddad et al. [12] documented worse improvement on the ODI and Core Outcome Measures Index (COMI) among infected patients at the 6- and 12-month endpoints, QOL scores obtained at the 2-year follow-up were similar between groups, consistent

with the notion that SSIs may delay but not prevent QOL improvements. Consistent with our own findings, this suggests that surgical site infections do not significantly alter long term outcomes. 4.2. SSIs and healthcare costs Multiple prior studies have examined the direct healthcare costs associated with post-operative wound infections. The first, published by Calderone et al, found that the occurrence of SSI increased costs by more than 300% [38]. Subsequent studies by McGirt et al. [39], Yeramaneni et al. [40], and others have stratified SSI-associated costs by surgical procedure and have found the direct costs of SSI to vary between $15,817 for a minimally invasive transforaminal lumbar interbody fusion (TLIF) to $29,290. However, with the exception of a prior publication of the senior author examining patients undergoing posterior cervical operations, there have been no studies examining both QOL outcomes and costs of surgical site infections. The merit to an approach considering both QOL outcomes and overall costs is that it allows for a valuation of the costeffectiveness of an intervention, which has become increasingly relevant in the era of quality-based reimbursement schema. Here we found that SSI infection was associated with a more than 250% increase in the cost per QALY. Using the baseline of $50,000 per QALY as the definition of a cost-effective measure [41], we found that SSI resulted in surgical intervention shifting from being a marginally cost-effective intervention to a highly cost-ineffective method. This is consistent with the prior results of Kuhns et al, who found a significant increase in cost per QALY at the 6-month endpoint among patients undergoing posterior cervical procedures [13]. Contextualized, these results, along with those of Kuhns et al. [13] suggest that not only the overall costs, but also the costeffectiveness of surgery are highly predicated upon the avoidance of post-operative complications, notably wound infection. Our results suggest that the main driver of both endpoints are increases in inpatient costs (136% higher for patients experiencing infection), though increases in post-operative cost are also notably higher in patients experiencing infection. Therefore, there is likely a strong financial incentive for payors to reimburse programs aimed at preventing SSIs, including adequate glycemic control in diabetic patients, encouragement of smoking cessation and pre-operative weight loss, screening for colonization by methicillin-resistant Staphylococcus aureus, use of preoperative antibiotics, and treatment of the wound with topical vancomycin [42]. Though these interventions increase the upfront costs of hospitalization, by reducing the risk of surgical site infection, they may decrease patient morbidity and overall episode-of-care costs. Painted against the backdrop of modern reimbursement systems, they may also help to ensure that these procedures remain cost effective, regardless of payor. 4.3. Limitations One limitation to this study is the relatively short patient follow-up time, which only affords us the opportunity to estimate short-term cost effectiveness of lumbar decompression and fusion. Prior work by Kuhns et al. [13] has suggested that the costeffectiveness of surgery may change with extended follow-up. Though SSI caused surgery to be cost-ineffective at both endpoints examined, the degree to which it is ineffective in the present study may change with increased follow-up. We believe it is unlikely to change substantially however, given prior evidence demonstrating the relative robustness of QOL improvements irrespective of the occurrence of SSI [11,14,35,37]. Another limitation is the relatively small sample size used. Sample samples increase the odds of data

Please cite this article as: Z. Pennington, S. J. Sundar, D. Lubelski et al., Cost and quality of life outcome analysis of postoperative infections after posterior lumbar decompression and fusion, Journal of Clinical Neuroscience, https://doi.org/10.1016/j.jocn.2019.07.025

Z. Pennington et al. / Journal of Clinical Neuroscience xxx (xxxx) xxx

skewing by statistical outliers. Such skewing could potentially magnify the cost or QOL differences observed between the infected and non-infected groups. A pre-study power analysis had demonstrated that the study, as designed, was sufficiently powered to detect differences in cost, but was too small detect any but the largest of differences in QOL outcomes. Nonetheless, our finding of no difference in QOL outcomes between infected and non-infected cohorts is supported by the existing literature, lending weight to our findings. 5. Conclusion Among patients undergoing posterior lumbar decompression and fusion procedures, we found that postoperative infections were associated with significantly increased care costs of approximately $20,782, but did not significantly affect missed workdays or overall QOL outcomes. Using QOL outcomes, we also found that SSIs significantly decreased the cost-effectiveness of lumbar decompression and fusion, pushing it from a cost-effective to a cost-ineffective intervention. These data identify a significant financial incentive for payors to identify and invest in management strategies designed to reduce the incidence of infection. Disclosure of funding None. Personal disclosures Zach Pennington None. Swetha J. Sundar: None. Daniel Lubelski: None. Matthew D. Alvin: None. Edward C. Benzel: None. Thomas E. Mroz: Stock ownership in Pearldiver Inc. Consultant for Globus. Speaking/Teaching Arrangements with AOSpine. IRB approval IRB approval was obtained prior to initiation of the study (IRB # 13-378). Acknowledgements None. References [1] Collins I, Wilson-MacDonald J, Chami G, Burgoyne W, Vineyakam P, Berendt T, et al. The diagnosis and management of infection following instrumented spinal fusion. Eur Spine J 2008;17:445–50. https://doi.org/10.1007/s00586007-0559-8. [2] Schimmel JJP, Horsting PP, de Kleuver M, Wonders G, van Limbeek J. Risk factors for deep surgical site infections after spinal fusion. Eur Spine J 2010;19:1711–9. https://doi.org/10.1007/s00586-010-1421-y. [3] O’Neill KR, Smith JG, Abtahi AM, Archer KR, Spengler DM, McGirt MJ, et al. Reduced surgical site infections in patients undergoing posterior spinal stabilization of traumatic injuries using vancomycin powder. Spine J 2011;11:641–6. https://doi.org/10.1016/j.spinee.2011.04.025. [4] Liu J-M, Deng H-L, Chen X-Y, Zhou Y, Yang D, Duan M-S, et al. Factors for surgical site infection after posterior lumbar spinal surgery. Spine (Phila Pa 1976;2018(43):732–7. https://doi.org/10.1097/BRS.0000000000002419. [5] Martin BI, Mirza SK, Spina N, Spiker WR, Lawrence B, Brodke DS. Trends in lumbar fusion procedure rates and associated hospital costs for degenerative spinal diseases in the United States, 2004 to 2015. Spine (Phila Pa 1976) 2019;44:369–76. https://doi.org/10.1097/BRS.0000000000002822. [6] Wimmer C, Gluch H, Franzreb M, Ogon M. Predisposing factors for infection in spine surgery: a survey of 850 spinal procedures. J Spinal Disord 1998;11:124–8.

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[7] Meng F, Cao J, Meng X. Risk factors for surgical site infections following spinal surgery. J Clin Neurosci 2015;22:1862–6. [8] Fei Q, Li J, Lin J-SJ, Li D, Wang B-QB, Meng H, et al. Factors for surgical site infection after spinal surgery: a meta-analysis. World Neurosurg 2016;95:507–15. https://doi.org/10.1016/j.wneu.2015.05.059. [9] Takeuchi M, Wakao N, Kamiya M, Hirasawa A, Murotani K, Takayasu M. A double-blind randomized controlled trial of the local application of vancomycin versus ampicillin powder into the operative field for thoracic and/or lumbar fusions. J Neurosurg Spine 2018;29:553–9. https://doi.org/ 10.3171/2018.3.SPINE171111. [10] Mirzashahi B, Chehrassan M, Mortazavi SMJ. Intrawound application of vancomycin changes the responsible germ in elective spine surgery without significant effect on the rate of infection: a randomized prospective study. Musculoskelet Surg 2017;102:35–9. https://doi.org/10.1007/s12306-0170490-z. [11] Mok JM, Guillaume TJ, Talu U, Berven SH, Deviren V, Kroeber M, et al. Clinical outcome of deep wound infection after instrumented posterior spinal fusion: a matched cohort analysis. Spine (Phila Pa 1976) 2009;34:578–83. https://doi. org/10.1097/BRS.0b013e31819a827c. [12] Haddad S, Núñez-Pereira S, Pigrau C, Rodríguez-Pardo D, Vila-Casademunt A, Alanay A, et al. The impact of deep surgical site infection on surgical outcomes after posterior adult spinal deformity surgery: a matched control study. Eur Spine J 2018;27:2518–28. https://doi.org/10.1007/s00586-018-5583-3. [13] Kuhns BD, Lubelski D, Alvin MD, Taub JS, McGirt MJ, Benzel EC, et al. Cost and quality of life outcome analysis of postoperative infections after subaxial dorsal cervical fusions. J Neurosurg Spine 2015;22:381–6. https://doi.org/ 10.3171/2014.10.SPINE14228. [14] Petilon JM, Glassman SD, Dimar JR, Carreon LY. Clinical outcomes after lumbar fusion complicated by deep wound infection. Spine (Phila Pa 1976) 2012;37:1370–4. https://doi.org/10.1097/BRS.0b013e31824a4d93. [15] Mangram AJ, Horan TC, Pearson ML, Silver LC, Jarvis WR. Guideline for prevention of surgical site infection, 1999. Am J Infect Control 1999;27:97–134. https://doi.org/10.1016/S0196-6553(99)70088-X. [16] Herdman M, Gudex C, Lloyd A, Janssen M, Kind P, Parkin D, et al. Development and preliminary testing of the new five-level version of EQ-5D (EQ-5D-5L). Qual Life Res 2011;20:1727–36. https://doi.org/10.1007/s11136-011-9903-x. [17] Kroenke K, Spitzer RL, Williams JB. The PHQ-9: validity of a brief depression severity measure. J Gen Intern Med 2001;16:606–13. [18] Anagnostis C, Gatchel RJ, Mayer TG. The pain disability questionnaire: a new psychometrically sound measure for chronic musculoskeletal disorders. Spine (Phila Pa 1976) 2004;29:2290–302. discussion 2303. [19] Tharin S, Mayer E, Krishnaney A. Lumbar microdiscectomy and lumbar decompression improve functional outcomes and depression scores. Evid Based Spine Care J 2012;3:65–6. https://doi.org/10.1055/s-0032-1328146. [20] Mueller B, Carreon LY, Glassman SD. Comparison of the EuroQOL-5D with the Oswestry Disability Index, back and leg pain scores in patients with degenerative lumbar spine pathology. Spine (Phila Pa 1976) 2013;38:757–61. https://doi.org/10.1097/BRS.0b013e31827ab803. [21] Freynhagen R, Baron R, Gockel U, Tölle TR. painDETECT: a new screening questionnaire to identify neuropathic components in patients with back pain. Curr Med Res Opin 2006;22:1911–20. https://doi.org/10.1185/ 030079906X132488. [22] Parker SL, Godil SS, Shau DN, Mendenhall SK, McGirt MJ. Assessment of the minimum clinically important difference in pain, disability, and quality of life after anterior cervical discectomy and fusion. J Neurosurg Spine 2013;18:154–60. https://doi.org/10.3171/2012.10.SPINE12312. [23] Löwe B, Unützer J, Callahan CM, Perkins AJ, Kroenke K. Monitoring depression treatment outcomes with the patient health questionnaire-9. Med Care 2004;42:1194–201. [24] Farrar JT, Young JP, LaMoreaux L, Werth JL, Poole RM. Clinical importance of changes in chronic pain intensity measured on an 11-point numerical pain rating scale. Pain 2001;94:149–58. [25] Parker SL, Adogwa O, Paul AR, Anderson WN, Aaronson O, Cheng JS, et al. Utility of minimum clinically important difference in assessing pain, disability, and health state after transforaminal lumbar interbody fusion for degenerative lumbar spondylolisthesis. J Neurosurg Spine 2011;14:598–604. https://doi. org/10.3171/2010.12.SPINE10472. [26] Parker SL, Adogwa O, Mendenhall SK, Shau DN, Anderson WN, Cheng JS, et al. Determination of minimum clinically important difference (MCID) in pain, disability, and quality of life after revision fusion for symptomatic pseudoarthrosis. Spine J 2012;12:1122–8. https://doi.org/10.1016/j. spinee.2012.10.006. [27] Räsänen P, Roine E, Sintonen H, Semberg-Konttinen V, Ryynänen O-P, Roine R. Use of quality-adjusted life years for the estimation of effectiveness of health care: a systematic literature review. Int J Technol Assess Health Care 2006;22:235–41. https://doi.org/10.1017/S0266462306051051. [28] EuroQol Group. EuroQol–a new facility for the measurement of health-related quality of life. Health Policy 1990;16:199–208. [29] Krawzik K. DRG Expert – volume 1&2. 2019th ed. Salt Lake City, UT: Optuminsight Inc; 2019. [30] Centers for Medicare & Medicaid Services. Physician Fee Schedule Search. CMSGov 2019. https://www.cms.gov/apps/physician-fee-schedule/search/ search-criteria.aspx (accessed March 21, 2019). [31] Book Red. Pharmacy’s fundamental reference. 111th ed. PDR Network; 2007. [32] Alvin MD, Lubelski D, Abdullah KG, Whitmore RG, Benzel EC, Mroz TE. Costutility analysis of anterior cervical discectomy and fusion with plating (ACDFP)

Please cite this article as: Z. Pennington, S. J. Sundar, D. Lubelski et al., Cost and quality of life outcome analysis of postoperative infections after posterior lumbar decompression and fusion, Journal of Clinical Neuroscience, https://doi.org/10.1016/j.jocn.2019.07.025

6

[33]

[34]

[35]

[36]

[37]

Z. Pennington et al. / Journal of Clinical Neuroscience xxx (xxxx) xxx versus posterior cervical foraminotomy (PCF) for patients with single-level cervical radiculopathy at 1-year follow-up. Clin Spine Surg 2016;29:E67–72. https://doi.org/10.1097/BSD.0000000000000099. St. Louis Federal Reserve. Inflation – Economic Data Series | FRED | St. Louis Fed. Econ Res Fed Reserv Back St Louis 2019. https://fred.stlouisfed.org/tags/ series?t=inflation (accessed March 21, 2019). Shaffrey E, Smith JS, Lenke LG, Polly DW, Chen C-J, Coe JD, et al. Rates and causes of mortality associated with spine surgery. Spine (Phila Pa 1976) 2014;39:579–86. https://doi.org/10.1097/BRS.0000000000000201. Falavigna A, Righesso O, Traynelis VC, Teles AR, da Silva PG. Effect of deep wound infection following lumbar arthrodesis for degenerative disc disease on long-term outcome: a prospective study: clinical article. J Neurosurg Spine 2011;15:399–403. https://doi.org/10.3171/2011.5.SPINE10825. Rihn JA, Lee JY, Ward WT. Infection after the surgical treatment of adolescent idiopathic scoliosis. Spine (Phila Pa 1976) 2008;33:289–94. https://doi.org/ 10.1097/BRS.0b013e318162016e. Glassman SD, Hamill CL, Bridwell KH, Schwab FJ, Dimar JR, Lowe TG. The impact of perioperative complications on clinical outcome in adult deformity

[38] [39]

[40]

[41]

[42]

surgery. Spine (Phila Pa 1976) 2007;32:2764–70. https://doi.org/10.1097/ BRS.0b013e31815a7644. Calderone RR, Garland DE, Capen DA, Oster H. Cost of medical care for postoperative spinal infections. Orthop Clin North Am 1996;27:171–82. McGirt MJ, Parker SL, Lerner J, Engelhart L, Knight T, Wang MY. Comparative analysis of perioperative surgical site infection after minimally invasive versus open posterior/transforaminal lumbar interbody fusion: analysis of hospital billing and discharge data from 5170 patients. J Neurosurg Spine 2011;14:771–8. https://doi.org/10.3171/2011.1.SPINE10571. Yeramaneni S, Gum JL, Carreon LY, Klineberg EO, Smith JS, Jain A, et al. Impact of readmissions in episodic care of adult spinal deformity. J Bone Jt Surg 2018;100:487–95. https://doi.org/10.2106/JBJS.16.01589. Neumann PJ, Cohen JT, Weinstein MC. Updating cost-effectiveness—the curious resilience of the $50,000-per-QALY threshold. N Engl J Med 2014;371:796–7. https://doi.org/10.1056/NEJMp1405158. Anderson PA, Savage JW, Vaccaro AR, Radcliff K, Arnold PM, Lawrence BD, et al. Prevention of surgical site infection in spine surgery. Neurosurgery 2017;80: S114–23. https://doi.org/10.1093/neuros/nyw066.

Please cite this article as: Z. Pennington, S. J. Sundar, D. Lubelski et al., Cost and quality of life outcome analysis of postoperative infections after posterior lumbar decompression and fusion, Journal of Clinical Neuroscience, https://doi.org/10.1016/j.jocn.2019.07.025