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Anterior Lumbar Fusion: Differences in Patient Selection and Surgical Outcomes Between Neurosurgeons and Orthopaedic Surgeons
Original Article
Anterior Lumbar Fusion: Differences in Patient Selection and Surgical Outcomes Between Neurosurgeons and Orthopaedic Surgeons Rachel S. Bronheim1, Zoe B. Cheung1, Kevin Phan2,3, Samuel J.W. White1, Jun S. Kim1, Samuel K. Cho1
OBJECTIVE: Anterior lumbar fusion (ALF) is performed by both neurosurgeons and orthopaedic surgeons. The aim of this study was to determine differences between the 2 surgical subspecialties in terms of patient selection and postoperative outcomes after ALF.
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METHODS: A retrospective cohort study of adult patients undergoing ALF in the American College of Surgeons National Surgical Quality Improvement Program database from 2010 to 2014 was performed. Univariate analyses were performed to identify differences in baseline patient demographics, comorbidities, operative characteristics, and 30-day postoperative outcomes between neurosurgery and orthopaedic surgery patients. Multivariate logistic regression analysis was used to determine whether surgical subspecialty was an independent risk factor for postoperative complications.
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RESULTS: The study included 3182 patients, with 1629 (51.2%) neurosurgery patients and 1553 (48.8%) orthopaedic surgery patients. A greater proportion of neurosurgery patients were >65 years old, were being treated with preoperative steroids, had cardiac or pulmonary comorbidities, and had an American Society of Anesthesiologists classification III or higher. ALF procedures performed by neurosurgeons more frequently involved use of intervertebral devices and bone graft. On multivariate logistic regression analysis, ALF procedures performed by neurosurgeons were independently associated with a higher risk of reoperation (odds ratio [ 1.61; 95% confidence interval,
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Key words - Anterior lumbar fusion - Complications - Neurosurgery - NSQIP - Orthopaedic surgery - Patient selection Abbreviations and Acronyms ACS-NSQIP: American College of Surgeons National Surgical Quality Improvement Program ALF: Anterior lumbar fusion ASA: American Society of Anesthesiologists MVR: Multivariate regression UTI: Urinary tract infection
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1.02e2.56; P [ 0.042) and urinary tract infection (odds ratio [ 1.94; 95% confidence interval, 1.02e3.68; P [ 0.043). CONCLUSIONS: In addition to differences in baseline patient demographics and comorbidities and operative characteristics, ALF performed by neurosurgeons had a higher risk of 30-day reoperation and urinary tract infection compared with ALF performed by orthopaedic surgeons.
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INTRODUCTION
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nterior lumbar fusion (ALF) is a common procedure used to treat degenerative spine disorders and spinal deformity. The anterior approach preserves paraspinal muscles and ligaments and decreases the risk of dural tears compared with the posterior approach. However, the anterior approach requires mobilization of abdominal vasculature and viscera, thereby heightening the risk for vascular and visceral injury.1-3 The incidence of vascular injury in ALF has been reported to be 24%, and vascular injury most frequently occurs at the level of L4-L5.4-6 The relationship between ALF and postoperative morbidity is well established, with complication rates reaching 40%.2,3,7-9 Complications include sympathetic dysfunction, venous injury, sepsis, surgical site infection, unplanned reoperation, and sexual dysfunction.2,3,7-9 ALF procedures may be performed by either orthopaedic surgeons or neurosurgeons. Although both surgical subspecialties provide adequate training for this procedure, there are significant differences between the specialties in terms of residency training
From the 1Department of Orthopaedic Surgery, Icahn School of Medicine at Mount Sinai, New York, New York, USA; 2NeuroSpine Surgery Research Group, Prince of Wales Private Hospital, Sydney, Australia; and 3Department of Neurosurgery, Prince of Wales Hospital, Randwick, Sydney, Australia To whom correspondence should be addressed: Samuel K. Cho, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2018) 120:e221-e226. https://doi.org/10.1016/j.wneu.2018.08.034 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2018 Elsevier Inc. All rights reserved.
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experience. Studies show that neurosurgery residents perform 3 times as many spine surgeries as orthopaedic surgery residents over the course of their training.10,11 Overall, spine surgery makes up approximately 37% of neurosurgery residency training versus only 16% of orthopaedic surgery training.10,11 In addition, neurosurgery residents report higher levels of confidence in their abilities to perform spine procedures at the end of their residency training compared with orthopaedic surgery residents.11 It is unknown whether these disparities during residency training ultimately result in differences in clinical outcomes after ALF. Across a variety of spine surgeries, there has been no general consensus about whether outcomes and complications differ between neurosurgeons and orthopaedic surgeons.12-14 The objective of this study was to use a nationwide surgical outcomes database to determine whether there are differences in patient selection and postoperative complications between patients undergoing ALF with neurosurgeons versus orthopaedic surgeons. MATERIALS AND METHODS Study Design and Data Source The American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database was used to conduct this retrospective cohort study. The ACS-NSQIP database is a large, national surgical outcomes database derived from patient medical records. It collects data on patient demographics, comorbidities, intraoperative factors, and 30-day postoperative outcomes from >500 hospitals in the United States. The database encompasses a wide range of surgical subspecialties. Quality improvement initiatives based on the ACS-NSQIP database have been widely discussed and validated in the surgical literature.15,16 Data Collection and Variable Definitions Patients who underwent ALF between 2010 and 2014 were identified in the ACS-NSQIP database using Current Procedural Terminology code 22558. All patients included were adults (18 years old) undergoing elective, nonemergent ALF. Exclusion criteria included concurrent posterior cervical or lumbar procedures, concurrent anterior cervical procedures, pneumonia, sepsis, wound class II or higher, wound infection, and pregnancy. Patients were divided into 2 groups based on whether they underwent ALF performed by a neurosurgeon or an orthopaedic surgeon. Baseline patient demographics included age, sex, and race. Preoperative comorbidity variables included alcohol use, tobacco use, functional status (independent, partially dependent, totally dependent), cardiac comorbidity (hypertension requiring medication or history of congestive heart failure), pulmonary comorbidity (ventilator dependence 48 hours preoperatively or chronic obstructive pulmonary disease 30 days preoperatively), renal comorbidity (dialysis 2 weeks preoperatively or acute renal failure 24 hours preoperatively), steroid use (30 days preoperatively), 10% loss of body weight within 6 months, preoperative blood transfusion, bleeding disorder, and American Society of Anesthesiologists (ASA) classification. Intraoperative variables included use of bone graft, insertion of intervertebral device, osteotomy, fusion to the pelvis, length of fusion (short [3 levels] vs. long [4 levels]), and extended operative time (4 hours).
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Postoperative variables included prolonged length of stay 5 days, wound complications, cardiac complications (cardiac arrest requiring cardiopulmonary resuscitation or myocardial infarction), pulmonary complications (pneumonia, unplanned reintubation, or ventilator-assisted respiration), renal complications (progressive renal insufficiency or acute renal failure), urinary tract infection (UTI), blood transfusion, sepsis, reoperation, unplanned readmission, and mortality. Statistical Analysis Univariate analysis of baseline patient demographics, comorbidities, and intraoperative factors was performed using Pearson c2 test for categorical variables and t test for continuous variables. Univariate analysis of 30-day postoperative complications was also performed. Multivariate logistic regression (MVR) analysis was used to determine whether surgical subspecialty was an independent risk factor for 30-day postoperative complications after ALF. Statistical significance was set at P ¼ 0.05. All statistical analysis was conducted using IBM SPSS Version 20 for Windows (IBM Corp., Armonk, New York, USA). RESULTS The inclusion criteria for this study were met by 3182 patients, including 1629 (51.2%) neurosurgery patients and 1553 (48.8%) orthopaedic surgery patients. Within this cohort, 25.4% of patients were 65 years old. Women were overrepresented, composing 54.9% of the cohort. Of patients, 43.6% were obese. Baseline patient characteristics in the 2 study groups are outlined in Table 1. A smaller proportion of orthopaedic surgery patients was >65 years old compared with neurosurgery patients (22.5% vs. 28.3%, P < 0.001). In terms of medical comorbidities, a lower percentage of orthopaedic surgery patients were receiving preoperative steroids (1.9% vs. 3.3%, P ¼ 0.014), had pulmonary comorbidity (5.3% vs. 7.1%, P ¼ 0.039) or cardiac comorbidity (40.4% vs. 46.1%, P ¼ 0.001), and were ASA classification III or higher (33.1% vs. 41.0%, P < 0.001) compared with neurosurgical patients. There were no other significant differences in the remaining comorbidities between the 2 groups. Intraoperatively, ALF procedures performed by orthopaedic surgeons less frequently involved insertion of intervertebral devices (65.4% vs. 74.2%, P < 0.001) and use of bone graft (44.9% vs. 54.1%, P < 0.001). Several preoperative factors did not differ between the 2 specialties, including sex (P ¼ 0.562), diabetes (P ¼ 0.157), smoking (P ¼ 0.787), recent weight loss (P ¼ 0.953), bleeding disorder (P ¼ 0.528), preoperative transfusion (P ¼ 0.128), obesity (P ¼ 0.552), dyspnea (P ¼ 0.108), and functional status (P ¼ 0.989). Use of osteotomy (P ¼ 0.337), pelvic fusion (P ¼ 0.824), fusion length (P ¼ 0.212), and operative time >4 hours (P ¼ 0.602) did not differ between the 2 surgical subspecialties. On univariate analysis, there were no significant differences in 30-day postoperative complications between neurosurgery and orthopaedic surgery patients (Table 2). These complications included prolonged length of stay >5 days (P ¼ 0.395), discharge destination (P ¼ 0.167), wound complication (P ¼ 0.295), pulmonary complication (P ¼ 0.756), cardiac complication (P ¼ 0.246), renal complication (P ¼ 0.693), UTI
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Table 1. Baseline Patient Characteristics and Comorbidities Neurosurgery
Orthopaedic Surgery
P Value
Demographics and comorbidities Sex
0.562
Male
743 (45.6%)
692 (44.6%)
Female
887 (54.4%)
861 (55.4%)
Age 65 years
461 (28.3%)
350 (22.5%)
Other
77 (4.7%)
95 (6.1%)
White
1434 (88.0%)
1298 (83.6%)
Black
99 (6.1%)
125 (8.0%)
Hispanic
19 (1.2%)
32 (2.1%)
Diabetes
208 (12.8%)
173 (11.1%)
0.157
Smoking
394 (24.2%)
382 (24.6%)
0.787
53 (3.3%)
29 (1.9%)
0.014
Race
Steroid use
DISCUSSION <0.001 0.007
Recent weight loss
3 (0.2%)
3 (0.2%)
0.953
Bleeding disorders
16 (1.0%)
12 (0.8%)
0.528
Preoperative transfusion
3 (0.2%)
8 (0.5%)
0.128
Obesity
715 (44.1%)
667 (43.1%)
0.552
Dyspnea
75 (4.6%)
54 (3.5%)
0.108
1590 (97.6%)
1516 (97.6%)
Functional status Independent
0.989
Dependent
28 (1.7%)
26 (1.7%)
Pulmonary comorbidity
116 (7.1%)
83 (5.3%)
0.039
Cardiac comorbidity
751 (46.1%)
628 (40.4%)
0.001
Renal comorbidity ASA class III or higher
0 (0.0%)
5 (0.3%)
0.988
666 (41.0%)
514 (33.1%)
<0.001
Operative characteristics Osteotomy Intervertebral device Fusion to pelvis Bone graft
45 (2.8%)
52 (3.3%)
0.337
1209 (74.2%)
1015 (65.4%)
0.000
6 (0.4%)
5 (0.3%)
0.824
881 (54.1%)
697 (44.9%)
0.001
Fusion length
0.212
Short
1567 (96.2%)
1480 (95.3%)
Long
62 (3.8%)
73 (4.7%)
337 (20.7%)
333 (21.4%)
Operative time >4 hours
the MVR analysis are outlined in Table 3. ALF surgery performed by neurosurgeons was independently associated with an increased risk of reoperation (odds ratio ¼ 1.61; 95% confidence interval, 1.02e2.56; P ¼ 0.042) and UTI (odds ratio ¼ 1.94; 95% confidence interval, 1.02e3.68; P ¼ 0.043) compared with procedures performed by orthopaedic surgeons.
0.602
All values are number (%). ASA, American Society of Anesthesiologists.
(P ¼ 0.055), intraoperative or postoperative blood transfusion (P ¼ 0.358), sepsis (P ¼ 0.110), reoperation (P ¼ 0.100), unplanned readmission (P ¼ 0.065), and mortality (P ¼ 0.448). Results of
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There is significant overlap in the types of spine procedures performed by neurosurgeons and orthopaedic surgeons. However, previous literature has shown that there are differences between neurosurgery and orthopaedic surgery in clinical decision making in spine disorders.17-19 ALF is performed by both neurosurgeons and orthopaedic surgeons. The objective of this study was to identify differences in patient selection and surgical outcomes following ALF performed by neurosurgeons and orthopaedic surgeons. In a cohort of 3182 patients undergoing ALF in the ACS-NSQIP database, neurosurgeons and orthopaedic surgeons performed a comparable number of ALF procedures. Neurosurgical patients more frequently were >65 years old, were taking preoperative steroids, had cardiac and pulmonary comorbidities, and had a high ASA classification. They also more frequently underwent insertion of an intervertebral device and application of bone graft. Despite these differences, there were no significant differences in 30-day postoperative complications following ALF performed by neurosurgeons and orthopaedic surgeons. However, MVR analysis found that ALF performed by neurosurgeons was associated with a 1.6 and 1.9 times increased risk of reoperation and UTI, respectively. It has been well established in the literature that age is a risk factor for increased morbidity in spine surgery.20-24 We found that neurosurgeons more frequently operate on patients >65 years old compared with orthopaedic surgeons. This is in contrast to previous studies, which found no significant age difference between neurosurgery patients and orthopaedic surgery patients.12,14,25 It is unclear what accounts for the significant age difference found in our study, and this may be further investigated in future studies. Our results also demonstrated that neurosurgery patients were more frequently receiving preoperative steroids, had a greater incidence of cardiac and pulmonary comorbidities, and had higher ASA classifications compared with orthopaedic surgery patients. This suggests that neurosurgeons more often select patients who are medically complex with more comorbidities. With regard to steroid use, 3.3% of neurosurgery patients were receiving preoperative steroids compared with 1.9% of orthopaedic surgery patients. The ACS-NSQIP database does not include data on the indication for steroid therapy or the specific dosing regimen before surgery. However, this is still a significant finding, as steroid use has been shown to delay fusion after spinal surgery.26,27 The ACS-NSQIP database includes only 30-day postoperative outcomes, limiting our ability to determine the effect of preoperative steroids on long-term fusion rates. In this study, we also found that neurosurgery patients more commonly had cardiac comorbidities, pulmonary comorbidities, and high ASA classifications compared with orthopaedic surgery patients. This difference in the incidence of cardiac comorbidities
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Table 2. 30-Day Postoperative Complications Complication Length of stay >5 days Wound complication
Neurosurgery
Orthopaedic P Surgery Value
378 (23.3%)
341 (22.0%) 0.395
38 (2.3%)
28 (1.8%)
Table 3. Multivariate Regression Analysis of Surgical Subspecialty as an Independent Risk Factor for 30-Day Postoperative Complications Outcome
OR
95% CI
P Value
0.295
Reoperation
1.613
1.017e2.558
0.042
1.940
1.022e3.682
0.043
Pulmonary complication
21 (1.3%)
22 (1.4%)
0.756
UTI
Cardiac complication
5 (0.3%)
9 (0.6%)
0.246
OR, odds ratio; CI, confidence interval; UTI, urinary tract infection.
Renal complication
3 (0.2%)
2 (0.1%)
0.693
Urinary tract infection
30 (1.8%)
16 (1.0%)
0.055
Intraoperative/postoperative transfusion
131 (8.0%)
139 (9.0%)
0.358
Sepsis
15 (0.9%)
7 (0.5%)
0.110
Reoperation
51 (3.1%)
34 (2.2%)
0.100
Unplanned readmission
73 (4.5%)
50 (3.2%)
0.065
Mortality
4 (0.2%)
2 (0.2%)
0.448
All values are number (%).
is in contrast to prior studies that have found no significant difference between patients undergoing spine surgery with neurosurgeons and orthopaedic surgeons.12,14,25 However, the difference in pulmonary comorbidities is consistent with a study by Minhas et al.,14 which demonstrated that neurosurgery patients had a higher risk of preoperative dyspnea and chronic obstructive pulmonary disease compared with orthopaedic surgery patients. Cardiac and pulmonary comorbidities are well-recognized risk factors for postoperative complications after spine surgery.28-30 Additionally, prior studies have described a consistent relationship between higher ASA classification and a wide array of postoperative complications after spine surgery.31-35 For example, studies by Seicean et al.,12 Minhas et al.,14 and Kim et al.25 demonstrated that neurosurgery patients were more likely to have an ASA classification III or higher than orthopaedic surgery patients. One potential explanation for these findings is that neurosurgeons may tend to be more willing to electively operate on patients who are medically complex. This potential difference in patient selection is important to consider in the context of not only postoperative complications, but also for associated inpatient length of stay and health care costs. Another possible confounding factor is surgeons’ choice of approach (anterior vs. posterior) for patients with different comorbidities. The retrospective nature of the ACS-NSQIP database did not allow us to examine this observed difference in patient selection between neurosurgery and orthopaedic surgery in more detail. It would be interesting for future prospective studies to elucidate factors that contribute to the difference in patient selection for ALF performed by neurosurgeons versus orthopaedic surgeons. In this study, we also found that neurosurgeons more frequently used intervertebral devices and bone graft than orthopaedic surgeons. Previous studies comparing neurosurgeons and orthopaedic surgeons did not examine these 2 operative characteristics. Intervertebral devices have been associated with high rates of
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fusion, low rates of subsidence, and superior clinical outcomes.36-38 Likewise, bone graft has been shown to improve fusion rates and postoperative outcomes.37,38 Although this is an interesting finding, the underlying etiology of the observed difference remains unclear owing to the limitations of our retrospective cohort study. Despite the differences in baseline patient demographics and comorbidities as well operative variables, there were few significant differences in 30-day postoperative outcomes following ALF performed by neurosurgeons and orthopaedic surgeons. Neurosurgery patients had a 1.6 times increased odds of reoperation within 30 days. This finding is in contrast to prior studies in the literature that found no difference in reoperation rates between the 2 subspecialties.12,25,39 We speculate that perhaps the higher comorbidity burden of neurosurgery patients in this study may have contributed to the higher reoperation rate. However, it is also plausible that the difference in reoperation rates may be driven by factors not captured in the ACS-NSQIP database. Reoperation is a major complication, as it confers an increased risk of morbidity and mortality as well as a decrease in quality-of-life metrics.40 Therefore, it is important to understand the underlying etiology of this difference to develop effective strategies and protocols to decrease the risk of reoperation following ALF. This study has several limitations, which are largely related to the nature of our data source. First, the ACS-NSQIP database was designed to capture data relevant to a wide variety of surgical subspecialties. Therefore, data points are generic in that variables of interest are not specific to spine surgery. For example, specific radiographic findings or quality-of-life metrics are not collected in the database. In addition, the specific indication for each ALF was not included, limiting our ability to compare patients undergoing ALF for different indications. Second, the ACS-NSQIP database includes outcomes only up to 30 days postoperatively, limiting our ability to analyze midterm and long-term outcomes. In addition, academic tertiary care centers are overrepresented in this database, which may limit the generalizability of our findings to medical centers nationwide. Another limitation is the statistically significant differences in baseline patient characteristics between our comparison groups. Although we attempted to control for these baseline differences by including the relevant variables in our MVR analysis, we did not perform a formal matching process between the comparison groups. Our findings were therefore subject to potential confounding variables. Finally, the retrospective nature of this study does not allow us to determine causal relationships between surgical subspecialty and patient selection or postoperative outcomes. However, the identified associative
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relationships in this study may lend themselves to be the focus of future prospective studies. CONCLUSIONS In this retrospective cohort analysis of 3182 patients in the ACSNSQIP database, we found that neurosurgery patients undergoing ALF were older with medical comorbidities compared with orthopaedic surgery patients undergoing ALF. Neurosurgeons also
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
39. Bederman SS, Kreder HJ, Weller I, Finkelstein JA, Ford MH, Yee AJ. The who, what and when of surgery for the degenerative lumbar spine: a population-based study of surgeon factors, surgical procedures, recent trends and reoperation rates. Can J Surg. 2009;52:283-290.
Received 4 July 2018; accepted 6 August 2018
40. Scheer JK, Tang JA, Smith JS, Klineberg E, Hart RA, Mundis GM Jr, et al. Reoperation rates
1878-8750/$ - see front matter ª 2018 Elsevier Inc. All rights reserved.
Citation: World Neurosurg. (2018) 120:e221-e226. https://doi.org/10.1016/j.wneu.2018.08.034 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.08.034
Anterior Lumbar Fusion: Differences in Patient Selection and Surgical Outcomes Between Neurosurgeons and Orthopaedic Surgeons Rachel S. Bronheim1, Zoe B. Cheung1, Kevin Phan2,3, Samuel J.W. White1, Jun S. Kim1, Samuel K. Cho1
OBJECTIVE: Anterior lumbar fusion (ALF) is performed by both neurosurgeons and orthopaedic surgeons. The aim of this study was to determine differences between the 2 surgical subspecialties in terms of patient selection and postoperative outcomes after ALF.
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METHODS: A retrospective cohort study of adult patients undergoing ALF in the American College of Surgeons National Surgical Quality Improvement Program database from 2010 to 2014 was performed. Univariate analyses were performed to identify differences in baseline patient demographics, comorbidities, operative characteristics, and 30-day postoperative outcomes between neurosurgery and orthopaedic surgery patients. Multivariate logistic regression analysis was used to determine whether surgical subspecialty was an independent risk factor for postoperative complications.
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RESULTS: The study included 3182 patients, with 1629 (51.2%) neurosurgery patients and 1553 (48.8%) orthopaedic surgery patients. A greater proportion of neurosurgery patients were >65 years old, were being treated with preoperative steroids, had cardiac or pulmonary comorbidities, and had an American Society of Anesthesiologists classification III or higher. ALF procedures performed by neurosurgeons more frequently involved use of intervertebral devices and bone graft. On multivariate logistic regression analysis, ALF procedures performed by neurosurgeons were independently associated with a higher risk of reoperation (odds ratio [ 1.61; 95% confidence interval,
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Key words - Anterior lumbar fusion - Complications - Neurosurgery - NSQIP - Orthopaedic surgery - Patient selection Abbreviations and Acronyms ACS-NSQIP: American College of Surgeons National Surgical Quality Improvement Program ALF: Anterior lumbar fusion ASA: American Society of Anesthesiologists MVR: Multivariate regression UTI: Urinary tract infection
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1.02e2.56; P [ 0.042) and urinary tract infection (odds ratio [ 1.94; 95% confidence interval, 1.02e3.68; P [ 0.043). CONCLUSIONS: In addition to differences in baseline patient demographics and comorbidities and operative characteristics, ALF performed by neurosurgeons had a higher risk of 30-day reoperation and urinary tract infection compared with ALF performed by orthopaedic surgeons.
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INTRODUCTION
A
nterior lumbar fusion (ALF) is a common procedure used to treat degenerative spine disorders and spinal deformity. The anterior approach preserves paraspinal muscles and ligaments and decreases the risk of dural tears compared with the posterior approach. However, the anterior approach requires mobilization of abdominal vasculature and viscera, thereby heightening the risk for vascular and visceral injury.1-3 The incidence of vascular injury in ALF has been reported to be 24%, and vascular injury most frequently occurs at the level of L4-L5.4-6 The relationship between ALF and postoperative morbidity is well established, with complication rates reaching 40%.2,3,7-9 Complications include sympathetic dysfunction, venous injury, sepsis, surgical site infection, unplanned reoperation, and sexual dysfunction.2,3,7-9 ALF procedures may be performed by either orthopaedic surgeons or neurosurgeons. Although both surgical subspecialties provide adequate training for this procedure, there are significant differences between the specialties in terms of residency training
From the 1Department of Orthopaedic Surgery, Icahn School of Medicine at Mount Sinai, New York, New York, USA; 2NeuroSpine Surgery Research Group, Prince of Wales Private Hospital, Sydney, Australia; and 3Department of Neurosurgery, Prince of Wales Hospital, Randwick, Sydney, Australia To whom correspondence should be addressed: Samuel K. Cho, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2018) 120:e221-e226. https://doi.org/10.1016/j.wneu.2018.08.034 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2018 Elsevier Inc. All rights reserved.
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experience. Studies show that neurosurgery residents perform 3 times as many spine surgeries as orthopaedic surgery residents over the course of their training.10,11 Overall, spine surgery makes up approximately 37% of neurosurgery residency training versus only 16% of orthopaedic surgery training.10,11 In addition, neurosurgery residents report higher levels of confidence in their abilities to perform spine procedures at the end of their residency training compared with orthopaedic surgery residents.11 It is unknown whether these disparities during residency training ultimately result in differences in clinical outcomes after ALF. Across a variety of spine surgeries, there has been no general consensus about whether outcomes and complications differ between neurosurgeons and orthopaedic surgeons.12-14 The objective of this study was to use a nationwide surgical outcomes database to determine whether there are differences in patient selection and postoperative complications between patients undergoing ALF with neurosurgeons versus orthopaedic surgeons. MATERIALS AND METHODS Study Design and Data Source The American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database was used to conduct this retrospective cohort study. The ACS-NSQIP database is a large, national surgical outcomes database derived from patient medical records. It collects data on patient demographics, comorbidities, intraoperative factors, and 30-day postoperative outcomes from >500 hospitals in the United States. The database encompasses a wide range of surgical subspecialties. Quality improvement initiatives based on the ACS-NSQIP database have been widely discussed and validated in the surgical literature.15,16 Data Collection and Variable Definitions Patients who underwent ALF between 2010 and 2014 were identified in the ACS-NSQIP database using Current Procedural Terminology code 22558. All patients included were adults (18 years old) undergoing elective, nonemergent ALF. Exclusion criteria included concurrent posterior cervical or lumbar procedures, concurrent anterior cervical procedures, pneumonia, sepsis, wound class II or higher, wound infection, and pregnancy. Patients were divided into 2 groups based on whether they underwent ALF performed by a neurosurgeon or an orthopaedic surgeon. Baseline patient demographics included age, sex, and race. Preoperative comorbidity variables included alcohol use, tobacco use, functional status (independent, partially dependent, totally dependent), cardiac comorbidity (hypertension requiring medication or history of congestive heart failure), pulmonary comorbidity (ventilator dependence 48 hours preoperatively or chronic obstructive pulmonary disease 30 days preoperatively), renal comorbidity (dialysis 2 weeks preoperatively or acute renal failure 24 hours preoperatively), steroid use (30 days preoperatively), 10% loss of body weight within 6 months, preoperative blood transfusion, bleeding disorder, and American Society of Anesthesiologists (ASA) classification. Intraoperative variables included use of bone graft, insertion of intervertebral device, osteotomy, fusion to the pelvis, length of fusion (short [3 levels] vs. long [4 levels]), and extended operative time (4 hours).
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Postoperative variables included prolonged length of stay 5 days, wound complications, cardiac complications (cardiac arrest requiring cardiopulmonary resuscitation or myocardial infarction), pulmonary complications (pneumonia, unplanned reintubation, or ventilator-assisted respiration), renal complications (progressive renal insufficiency or acute renal failure), urinary tract infection (UTI), blood transfusion, sepsis, reoperation, unplanned readmission, and mortality. Statistical Analysis Univariate analysis of baseline patient demographics, comorbidities, and intraoperative factors was performed using Pearson c2 test for categorical variables and t test for continuous variables. Univariate analysis of 30-day postoperative complications was also performed. Multivariate logistic regression (MVR) analysis was used to determine whether surgical subspecialty was an independent risk factor for 30-day postoperative complications after ALF. Statistical significance was set at P ¼ 0.05. All statistical analysis was conducted using IBM SPSS Version 20 for Windows (IBM Corp., Armonk, New York, USA). RESULTS The inclusion criteria for this study were met by 3182 patients, including 1629 (51.2%) neurosurgery patients and 1553 (48.8%) orthopaedic surgery patients. Within this cohort, 25.4% of patients were 65 years old. Women were overrepresented, composing 54.9% of the cohort. Of patients, 43.6% were obese. Baseline patient characteristics in the 2 study groups are outlined in Table 1. A smaller proportion of orthopaedic surgery patients was >65 years old compared with neurosurgery patients (22.5% vs. 28.3%, P < 0.001). In terms of medical comorbidities, a lower percentage of orthopaedic surgery patients were receiving preoperative steroids (1.9% vs. 3.3%, P ¼ 0.014), had pulmonary comorbidity (5.3% vs. 7.1%, P ¼ 0.039) or cardiac comorbidity (40.4% vs. 46.1%, P ¼ 0.001), and were ASA classification III or higher (33.1% vs. 41.0%, P < 0.001) compared with neurosurgical patients. There were no other significant differences in the remaining comorbidities between the 2 groups. Intraoperatively, ALF procedures performed by orthopaedic surgeons less frequently involved insertion of intervertebral devices (65.4% vs. 74.2%, P < 0.001) and use of bone graft (44.9% vs. 54.1%, P < 0.001). Several preoperative factors did not differ between the 2 specialties, including sex (P ¼ 0.562), diabetes (P ¼ 0.157), smoking (P ¼ 0.787), recent weight loss (P ¼ 0.953), bleeding disorder (P ¼ 0.528), preoperative transfusion (P ¼ 0.128), obesity (P ¼ 0.552), dyspnea (P ¼ 0.108), and functional status (P ¼ 0.989). Use of osteotomy (P ¼ 0.337), pelvic fusion (P ¼ 0.824), fusion length (P ¼ 0.212), and operative time >4 hours (P ¼ 0.602) did not differ between the 2 surgical subspecialties. On univariate analysis, there were no significant differences in 30-day postoperative complications between neurosurgery and orthopaedic surgery patients (Table 2). These complications included prolonged length of stay >5 days (P ¼ 0.395), discharge destination (P ¼ 0.167), wound complication (P ¼ 0.295), pulmonary complication (P ¼ 0.756), cardiac complication (P ¼ 0.246), renal complication (P ¼ 0.693), UTI
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Table 1. Baseline Patient Characteristics and Comorbidities Neurosurgery
Orthopaedic Surgery
P Value
Demographics and comorbidities Sex
0.562
Male
743 (45.6%)
692 (44.6%)
Female
887 (54.4%)
861 (55.4%)
Age 65 years
461 (28.3%)
350 (22.5%)
Other
77 (4.7%)
95 (6.1%)
White
1434 (88.0%)
1298 (83.6%)
Black
99 (6.1%)
125 (8.0%)
Hispanic
19 (1.2%)
32 (2.1%)
Diabetes
208 (12.8%)
173 (11.1%)
0.157
Smoking
394 (24.2%)
382 (24.6%)
0.787
53 (3.3%)
29 (1.9%)
0.014
Race
Steroid use
DISCUSSION <0.001 0.007
Recent weight loss
3 (0.2%)
3 (0.2%)
0.953
Bleeding disorders
16 (1.0%)
12 (0.8%)
0.528
Preoperative transfusion
3 (0.2%)
8 (0.5%)
0.128
Obesity
715 (44.1%)
667 (43.1%)
0.552
Dyspnea
75 (4.6%)
54 (3.5%)
0.108
1590 (97.6%)
1516 (97.6%)
Functional status Independent
0.989
Dependent
28 (1.7%)
26 (1.7%)
Pulmonary comorbidity
116 (7.1%)
83 (5.3%)
0.039
Cardiac comorbidity
751 (46.1%)
628 (40.4%)
0.001
Renal comorbidity ASA class III or higher
0 (0.0%)
5 (0.3%)
0.988
666 (41.0%)
514 (33.1%)
<0.001
Operative characteristics Osteotomy Intervertebral device Fusion to pelvis Bone graft
45 (2.8%)
52 (3.3%)
0.337
1209 (74.2%)
1015 (65.4%)
0.000
6 (0.4%)
5 (0.3%)
0.824
881 (54.1%)
697 (44.9%)
0.001
Fusion length
0.212
Short
1567 (96.2%)
1480 (95.3%)
Long
62 (3.8%)
73 (4.7%)
337 (20.7%)
333 (21.4%)
Operative time >4 hours
the MVR analysis are outlined in Table 3. ALF surgery performed by neurosurgeons was independently associated with an increased risk of reoperation (odds ratio ¼ 1.61; 95% confidence interval, 1.02e2.56; P ¼ 0.042) and UTI (odds ratio ¼ 1.94; 95% confidence interval, 1.02e3.68; P ¼ 0.043) compared with procedures performed by orthopaedic surgeons.
0.602
All values are number (%). ASA, American Society of Anesthesiologists.
(P ¼ 0.055), intraoperative or postoperative blood transfusion (P ¼ 0.358), sepsis (P ¼ 0.110), reoperation (P ¼ 0.100), unplanned readmission (P ¼ 0.065), and mortality (P ¼ 0.448). Results of
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There is significant overlap in the types of spine procedures performed by neurosurgeons and orthopaedic surgeons. However, previous literature has shown that there are differences between neurosurgery and orthopaedic surgery in clinical decision making in spine disorders.17-19 ALF is performed by both neurosurgeons and orthopaedic surgeons. The objective of this study was to identify differences in patient selection and surgical outcomes following ALF performed by neurosurgeons and orthopaedic surgeons. In a cohort of 3182 patients undergoing ALF in the ACS-NSQIP database, neurosurgeons and orthopaedic surgeons performed a comparable number of ALF procedures. Neurosurgical patients more frequently were >65 years old, were taking preoperative steroids, had cardiac and pulmonary comorbidities, and had a high ASA classification. They also more frequently underwent insertion of an intervertebral device and application of bone graft. Despite these differences, there were no significant differences in 30-day postoperative complications following ALF performed by neurosurgeons and orthopaedic surgeons. However, MVR analysis found that ALF performed by neurosurgeons was associated with a 1.6 and 1.9 times increased risk of reoperation and UTI, respectively. It has been well established in the literature that age is a risk factor for increased morbidity in spine surgery.20-24 We found that neurosurgeons more frequently operate on patients >65 years old compared with orthopaedic surgeons. This is in contrast to previous studies, which found no significant age difference between neurosurgery patients and orthopaedic surgery patients.12,14,25 It is unclear what accounts for the significant age difference found in our study, and this may be further investigated in future studies. Our results also demonstrated that neurosurgery patients were more frequently receiving preoperative steroids, had a greater incidence of cardiac and pulmonary comorbidities, and had higher ASA classifications compared with orthopaedic surgery patients. This suggests that neurosurgeons more often select patients who are medically complex with more comorbidities. With regard to steroid use, 3.3% of neurosurgery patients were receiving preoperative steroids compared with 1.9% of orthopaedic surgery patients. The ACS-NSQIP database does not include data on the indication for steroid therapy or the specific dosing regimen before surgery. However, this is still a significant finding, as steroid use has been shown to delay fusion after spinal surgery.26,27 The ACS-NSQIP database includes only 30-day postoperative outcomes, limiting our ability to determine the effect of preoperative steroids on long-term fusion rates. In this study, we also found that neurosurgery patients more commonly had cardiac comorbidities, pulmonary comorbidities, and high ASA classifications compared with orthopaedic surgery patients. This difference in the incidence of cardiac comorbidities
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Table 2. 30-Day Postoperative Complications Complication Length of stay >5 days Wound complication
Neurosurgery
Orthopaedic P Surgery Value
378 (23.3%)
341 (22.0%) 0.395
38 (2.3%)
28 (1.8%)
Table 3. Multivariate Regression Analysis of Surgical Subspecialty as an Independent Risk Factor for 30-Day Postoperative Complications Outcome
OR
95% CI
P Value
0.295
Reoperation
1.613
1.017e2.558
0.042
1.940
1.022e3.682
0.043
Pulmonary complication
21 (1.3%)
22 (1.4%)
0.756
UTI
Cardiac complication
5 (0.3%)
9 (0.6%)
0.246
OR, odds ratio; CI, confidence interval; UTI, urinary tract infection.
Renal complication
3 (0.2%)
2 (0.1%)
0.693
Urinary tract infection
30 (1.8%)
16 (1.0%)
0.055
Intraoperative/postoperative transfusion
131 (8.0%)
139 (9.0%)
0.358
Sepsis
15 (0.9%)
7 (0.5%)
0.110
Reoperation
51 (3.1%)
34 (2.2%)
0.100
Unplanned readmission
73 (4.5%)
50 (3.2%)
0.065
Mortality
4 (0.2%)
2 (0.2%)
0.448
All values are number (%).
is in contrast to prior studies that have found no significant difference between patients undergoing spine surgery with neurosurgeons and orthopaedic surgeons.12,14,25 However, the difference in pulmonary comorbidities is consistent with a study by Minhas et al.,14 which demonstrated that neurosurgery patients had a higher risk of preoperative dyspnea and chronic obstructive pulmonary disease compared with orthopaedic surgery patients. Cardiac and pulmonary comorbidities are well-recognized risk factors for postoperative complications after spine surgery.28-30 Additionally, prior studies have described a consistent relationship between higher ASA classification and a wide array of postoperative complications after spine surgery.31-35 For example, studies by Seicean et al.,12 Minhas et al.,14 and Kim et al.25 demonstrated that neurosurgery patients were more likely to have an ASA classification III or higher than orthopaedic surgery patients. One potential explanation for these findings is that neurosurgeons may tend to be more willing to electively operate on patients who are medically complex. This potential difference in patient selection is important to consider in the context of not only postoperative complications, but also for associated inpatient length of stay and health care costs. Another possible confounding factor is surgeons’ choice of approach (anterior vs. posterior) for patients with different comorbidities. The retrospective nature of the ACS-NSQIP database did not allow us to examine this observed difference in patient selection between neurosurgery and orthopaedic surgery in more detail. It would be interesting for future prospective studies to elucidate factors that contribute to the difference in patient selection for ALF performed by neurosurgeons versus orthopaedic surgeons. In this study, we also found that neurosurgeons more frequently used intervertebral devices and bone graft than orthopaedic surgeons. Previous studies comparing neurosurgeons and orthopaedic surgeons did not examine these 2 operative characteristics. Intervertebral devices have been associated with high rates of
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fusion, low rates of subsidence, and superior clinical outcomes.36-38 Likewise, bone graft has been shown to improve fusion rates and postoperative outcomes.37,38 Although this is an interesting finding, the underlying etiology of the observed difference remains unclear owing to the limitations of our retrospective cohort study. Despite the differences in baseline patient demographics and comorbidities as well operative variables, there were few significant differences in 30-day postoperative outcomes following ALF performed by neurosurgeons and orthopaedic surgeons. Neurosurgery patients had a 1.6 times increased odds of reoperation within 30 days. This finding is in contrast to prior studies in the literature that found no difference in reoperation rates between the 2 subspecialties.12,25,39 We speculate that perhaps the higher comorbidity burden of neurosurgery patients in this study may have contributed to the higher reoperation rate. However, it is also plausible that the difference in reoperation rates may be driven by factors not captured in the ACS-NSQIP database. Reoperation is a major complication, as it confers an increased risk of morbidity and mortality as well as a decrease in quality-of-life metrics.40 Therefore, it is important to understand the underlying etiology of this difference to develop effective strategies and protocols to decrease the risk of reoperation following ALF. This study has several limitations, which are largely related to the nature of our data source. First, the ACS-NSQIP database was designed to capture data relevant to a wide variety of surgical subspecialties. Therefore, data points are generic in that variables of interest are not specific to spine surgery. For example, specific radiographic findings or quality-of-life metrics are not collected in the database. In addition, the specific indication for each ALF was not included, limiting our ability to compare patients undergoing ALF for different indications. Second, the ACS-NSQIP database includes outcomes only up to 30 days postoperatively, limiting our ability to analyze midterm and long-term outcomes. In addition, academic tertiary care centers are overrepresented in this database, which may limit the generalizability of our findings to medical centers nationwide. Another limitation is the statistically significant differences in baseline patient characteristics between our comparison groups. Although we attempted to control for these baseline differences by including the relevant variables in our MVR analysis, we did not perform a formal matching process between the comparison groups. Our findings were therefore subject to potential confounding variables. Finally, the retrospective nature of this study does not allow us to determine causal relationships between surgical subspecialty and patient selection or postoperative outcomes. However, the identified associative
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SURGICAL SUBSPECIALTY IN ALF
relationships in this study may lend themselves to be the focus of future prospective studies. CONCLUSIONS In this retrospective cohort analysis of 3182 patients in the ACSNSQIP database, we found that neurosurgery patients undergoing ALF were older with medical comorbidities compared with orthopaedic surgery patients undergoing ALF. Neurosurgeons also
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34. Hackett NJ, De Oliveira GS, Jain UK, Kim JY. ASA class is a reliable independent predictor of medical complications and mortality following surgery. Int J Surg. 2015;18:184-190. 35. Kay HF, Sathiyakumar V, Yoneda ZT, Lee YM, Jahangir AA, Ehrenfeld JM, et al. The effects of American Society of Anesthesiologists physical status on length of stay and inpatient cost in the surgical treatment of isolated orthopaedic fractures. J Orthop Trauma. 2014;28:e153-e159. 36. Hartl R, Joeris A, McGuire RA. Comparison of the safety outcomes between two surgical approaches for anterior lumbar fusion surgery: anterior lumbar interbody fusion (ALIF) and extreme lateral interbody fusion (ELIF). Eur Spine J. 2016;25: 1484-1521.
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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Citation: World Neurosurg. (2018) 120:e221-e226. https://doi.org/10.1016/j.wneu.2018.08.034 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.08.034