Age Is a Risk Factor for Postoperative Complications Following Excisional Laminectomy for Intradural Extramedullary Spinal Tumors.

STUDY
DESIGN: Retrospective analysis.
OBJECTIVE: The incidence of intradural extramedullary (IDEM) spinal tumors is increasing. Excisional laminectomy for removal and decompression is the standard of care, but complications associated with patient age are unreported in the literature. Our objective is to identify if age is a risk factor for postoperative complications after excisional laminectomy of IDEM spinal tumors.
METHODS: A retrospective analysis was performed on the 2011 to 2014 ACS-NSQIP (American College of Surgeons National Surgical Quality Improvement Program) database for patients undergoing excisional laminectomy of IDEM spinal tumors. Age groups were determined by interquartile analysis. Chi-squared tests, t tests, and multivariate logistic regression models were employed to identify independent risk factors. Institutional review board approval was not needed.
RESULTS: A total of 1368 patients met the inclusion criteria for the study. Group 1 (age ≤ 44) contained 372 patients, group 2 (age 45-54) contained 314 patients, group 3 (age 55-66) contained 364 patients, and group 4 (age > 66) contained 318 patients. The univariate analysis showed that mortality and unplanned readmission were highest among patients in group 4 (1.26%, P = .011, and 10.00%, P = .039, respectively). Postoperative wound complications were highest among patients in group 1 (2.15%, P = .009), and postoperative venous thromboembolism and cardiac complications were highest among patients in group 3 (4.4%, P = .007, and 1.10%, P = .032, respectively). Multivariate logistic regression revealed that elderly age was an independent risk factor for postoperative venous thromboembolism (group 3 vs group 1; odds ratio = 6.739, confidence interval = 1.522-29.831, P = .012).
CONCLUSIONS: This analysis revealed that increased age is an independent risk factor for postoperative venous thromboembolism in patients undergoing excisional laminectomy for IDEM spinal tumors.

Introduction

Primary spinal tumors are rare and account for approximately 5% to 15% of all adult spinal tumors.[1] Spinal tumors can be classified as either intradural (within the dural sac) or extradural (outside the dural sac); intradural intramedullary tumors exist within the spinal cord and extramedullary tumor exist outside the spinal cord.[1,2] Intradural extramedullary (IDEM) tumors account for 30% of all spinal tumors[3,4] of which majority are benign.[5,6] The most common IDEM tumors are schwannoma (30%) and meningioma (25%).[7-9] The incidence of benign primary spinal tumor is 0.76 per 100 000 (age adjusted) in the United States, benign primary spinal tumors are more common in females (60%) than in males (40%), and non-Hispanic races account for 90% of benign cases.[10] The incidence of tumor increases with age and peaks at an incidence of 2.53 per 100 000 at the age of 70 to 79 years.[5,10,11]

Patients with spinal neoplasms commonly present with back pain, motor deficits, and sensory deficits due to physical compression of the tumor.[6] Decompression and tumor resection are viewed as an appropriate option for IDEM tumors,[5,12-14] and both can be achieved with excisional laminectomy.[1,15] Studies have shown that tumor resection can improve general health, quality of living, pain, disability, and in some cases survival.[8,16-20] However, surgery for spinal tumors is often complicated, costly, and associated with multiple complications and high mortality.[13,21,22] It is therefore important to study the predictors and risk factors that affect the clinical outcomes and success of such operations. Prior studies have suggested factors such as patient comorbidities, tumor size and location, and surgeon-related factors can affect postoperative complications.[16-20,23-26] However, there are currently no studies that have investigated the relationship between elderly age and the clinical outcome of excisional laminectomy for IDEM spinal tumors.[27,28]

The American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database has accumulated data from over 500 medical centers in the United States, with information concerning the patients’ preoperative, intraoperative, and 30-day postoperative outcomes; it has also collected past clinical outcomes following operations for elective spinal surgeries including fusion for degenerative spinal diseases and spinal deformity.[29-39] The use of the ACS-NSQIP database has helped improve the quality of clinical management, and this is seen with reduction in surgical site infection (SSI) and mortality rates in the Veteran Affairs system.[39-41] This study aims to use the NSQIP database to help determine whether age can be a predictor for the clinical outcome of IDEM tumor resection via excisional laminectomy. The authors hope to improve clinical management by identifying which acute postoperative complications elderly patients are at risk for, which may help postoperative management and improve patient selection for spinal operations.

Methods

Data Source

This was a retrospective analysis of prospectively collected data from the NSQIP database between 2011 and 2014. ACS-NSQIP is a large national database with risk-adjusted 30-day postoperative morbidity and mortality outcomes. Over 500 hospitals that vary in size, socioeconomic location, and academic affiliation contributed data to the 2010 to 2014 ACS-NSQIP database.[42] The data is collected by dedicated staff at each participating institution and includes data on over 150 demographic, preoperative, intraoperative, and early postoperative variables.[42]

Inclusion and Exclusion Criteria

The ACS-NSQIP database from 2010 to 2014 was used in this study. Adult patients (≥18 years) undergoing laminectomy and excision of thoracic intradural and cervical intradural tumors were identified from the database. Cases with missing preoperative data; emergency cases; patients with a wound class of 2, 3, or 4; an open wound on their body; current sepsis; current pneumonia; prior surgeries within 30 days; and cases requiring cardiopulmonary resuscitation prior to surgery were excluded in order to reduce the risk of confounding variables. The patient population was divided into age quartiles: ≤44 years, 45 to 54 years, 55 to 66 years, and >66 years.

Variable Definition

Patient demographic variables included sex and race (white, black, Hispanic, and other). Other race included American Indian, Alaska Native, Asian, Native Hawaiian, Pacific Islander, or unknown/not reported. Preoperative variables included obesity (≥30 kg/m2), diabetes (non–insulin-dependent diabetes mellitus or insulin-dependent diabetes mellitus), current smoking (within 1 year of surgery), dyspnea (≤30 days prior to surgery), functional status prior to surgery (independent or partially/totally dependent ≤30 days prior to surgery), pulmonary comorbidity (ventilator dependent ≤48 hours prior to surgery or history of chronic obstructive pulmonary disease ≤30 days prior to surgery), cardiac comorbidity (use of hypertensive medication or history of chronic heart failure ≤30 days prior to surgery), renal comorbidity (acute renal failure ≤24 hours prior to surgery or dialysis treatment ≤2 weeks prior to surgery), steroid use for chronic condition (≤30 days prior to surgery), ≥10% loss of body weight (in the past 6 months), bleeding disorder (chronic, active condition), preoperative transfusion of ≥1 unit of whole/packed red blood cells (RBCs; ≤72 hours prior to surgery), and posterior fusion surgery.

Thirty-day postoperative outcome variables include mortality, wound complication (superficial or deep SSI, organ space infection, or wound dehiscence), pulmonary complication (pneumonia, unplanned reintubation, or duration of ventilator-assisted respiration ≥48 hours), venous thromboembolism (VTE; pulmonary embolism or deep vein thrombosis), renal complication (progressive renal insufficiency or acute renal failure), urinary tract infection, cardiac complication (cardiac arrest requiring cardiopulmonary resuscitation or myocardial infarction), intra-/postoperative RBC transfusion, reoperation (related to initial procedure), and unplanned readmission (related to initial procedure). Nonelective surgery unrelated to the procedure includes those where the patient was transferred from another acute care hospital to the hospital for surgery, transferred from an emergency clinic, undergoing emergent/urgent surgical case, or admitted to the hospital on the day(s) prior to a scheduled procedure for any reason. ACS-NSQIP provides further information on variable characteristics.

Statistical Analysis

Univariate analysis was performed on patient demographics and preoperative, intraoperative, and postoperative characteristics using Pearson’s χ2 test. Fischer’s exact test was used where appropriate. Multivariable logistic regression models were employed, adjusting for patient demographics, preoperative characteristics, and patient comorbidities, to identify the influence of patient age on 30-day postoperative outcomes. The C-statistic, which is the area under the receiver operating characteristic curve, was also retrieved from the multivariate logistic regression analysis and determined the accuracy of this model. The area under the receiver operating characteristic curve is a graph of the fallout rate (1 − specificity) against the sensitivity (true-positive rate). The area under this curve measures the ability of the model to correctly classify those with complication and those without complication. SAS Studio Version 3.4 (SAS Institute Inc, Cary, NC) was used for all statistical analysis.

Results

Study Population

A total of 1368 patients were included in this study, with an age range from 19 to 89 years Patients were grouped into 1 of the 4 age groups: quartile 1 (≤44 years) with 372 (27.2%) patients, quartile 2 (45-54 years) with 314 (23%) patients, quartile 3 (55-66 yeas) with 364 (26.6%) patients, and quartile 4 (>66 years) with 318 (23.3%) patients. Univariate analysis between the age cohorts with regard to patient demographics and preoperative and intraoperative variable showed significant differences in distribution of race (P < .001), diabetes (P < .001), pulmonary comorbidity (P < .001), cardiac comorbidity (P < .001), dyspnea (P = .03), and American Society of Anesthesiologists (ASA) class ≥3 (P < .01). There were no significant differences in proportion of patients with partially or totally dependent functional status between the age quartiles (P = .13). Compared with the young age group, the elderly group was more likely to be white and female (Table 1).

Table 1.

Univariate Analysis of Patient Demographics and Preoperative and Intraoperative Variables Between Age Cohorts (N = 1368).

Category	≤44 Years, n (%)	45-54 Years, n (%)	55-66 Years, n (%)	>66 Years, n (%)	P
Total	372 (27.2)	314 (23.0)	364 (26.6)	318 (23.3)	—
Sex
Female	180 (48.4)	156 (49.7)	208 (57.1)	198 (62.3)	<.001
Male	192 (51.6)	158 (50.3)	156 (42.9)	120 (37.7)
Race
White	256 (69.2)	250 (80.7)	300 (82.4)	268 (84.3)	<.001
Other	30 (8.1)	16 (5.2)	18 (5.0)	6 (1.9)
Black	36 (9.7)	12 (3.9)	18 (5.0)	14 (4.4)
Hispanic	48 (13.0)	32 (10.3)	28 (7.7)	30 (9.4)
Diabetes	8 (2.2)	24 (7.6)	50 (13.7)	64 (20.1)	<.001
Dyspnea	8 (2.2)	8 (2.6)	18 (5.0)	18 (5.7)	.03
Functional status
Independent	348 (93.6)	296 (94.3)	348 (95.6)	290 (91.2)	.13
Partially or totally dependent	24 (6.5)	18 (5.7)	16 (4.4)	28 (8.8)
Pulmonary comorbidity	2 (0.5)	2 (0.6)	10 (2.8)	16 (5.0)	<.001
Cardiac comorbidity	36 (9.7)	86 (27.4)	186 (51.1)	218 (68.6)	<.001
Renal comorbidity	2 (0.5)	0 (0.0)	0 (0.0)	0 (0.0)	.16
ASA class ≥3	100 (26.9)	126 (40.1)	188 (51.7)	238 (74.8)	<.001

Abbreviation: ASA, American Society of Anesthesiologists.

Univariate Analysis

Among the different 30-day postoperative clinical outcomes, we observed significant differences in mortality, wound complication, VTE, cardiac complication, and unplanned readmission between the 4 cohorts. Mortality rate was higher among the elderly patients (quartile 1 = 0%, quartile 2 = 0%, quartile 3 = 1.1%, quartile 4 = 1.3%; P = .01). Similarly, cardiac complication was also more prominent in the elderly group (quartile 1 = 0%, quartile 2 = 0%, quartile 3 = 1.1%, quartile 4 = 0.6%; P = .03), as well as unplanned readmission (quartile 1 = 0%, quartile 2 = 9.7%, quartile 3 = 3.6%, quartile 4 = 10%; P = .04). VTE was highest in quartile 3, and a significant difference is seen between cohorts as well (quartile 1 = 1.6%, quartile 2 = 0.6%, quartile 3 = 4.4%, quartile 4 = 1.9%; P = .01). With regard to wound complication, both elderly and young age group showed an equal rate (quartile 1 = 2.2%, quartile 2 = 0.6%, quartile 3 = 1.7%, quartile 4 = 0%; P = .01). No significant differences were found between the age cohorts for the following postoperative outcomes: length of stay (P = .08), pulmonary complication (P = .66), urinary tract infection (P = .18), intra-/postoperative RBC transfusion (P = .47), sepsis (P = .2), and reoperation related to initial procedure (P = .78; Table 2).

Table 2.

Univariate Analysis of 30-Day Postoperative Outcomes Between Age Cohorts (N = 1368).

Category	≤44 Years, n (%)	45-54 Years, n (%)	55-66 Years, n (%)	>66 Years, n (%)	P
Mortality	0 (0.0)	0 (0.0)	4 (1.1)	4 (1.3)	.01
Length of stay ≥5 days	134 (36.0)	108 (34.4)	120 (33.0)	134 (42.1)	.08
Wound complication	8 (2.2)	2 (0.6)	6 (1.7)	0 (0.0)	.01
Pulmonary complication	8 (2.2)	4 (1.3)	4 (1.1)	4 (1.3)	.66
Venous thromboembolism	6 (1.6)	2 (0.6)	16 (4.4)	6 (1.9)	.01
Renal complication	0 (0)	0 (0)	0 (0)	0 (0)	—
Urinary tract infection	12 (3.2)	6 (1.9)	18 (5.0)	12 (3.8)	.18
Cardiac complication	0 (0.0)	0 (0.0)	4 (1.1)	2 (0.6)	.03
Intra-/postoperative red blood cell transfusion	16 (4.3)	10 (3.2)	14 (3.9)	18 (5.7)	.47
Sepsis	10 (2.7)	2 (0.6)	6 (1.7)	6 (1.9)	.20
Reoperation related to initial procedure	10 (3.0)	8 (2.7)	6 (1.9)	6 (2.2)	.78
Unplanned readmissiona	0 (0.0)	6 (9.7)	2 (3.6)	4 (10.0)	.04

aOnly 2012 to 2014 data, N = 262.

Multivariate Analysis

After adjustment for confounders, multivariate analysis demonstrated that the third age quartile (55-56 years) had a significantly increased odds of VTE compared with the first quartile (age ≤44 years; odds ratio = 2.66, 95% confidence interval = 1.01-7.03, P = .048; Table 3). There were no differences between the age quartiles in terms of proportion of patients with other complications after confounder adjustment.

Table 3.

Multivariate Analysis of Age as a Risk Factor for 30-Day Postoperative Outcomes Following Excisional Laminectomy for Intradural Cervical and Thoracic Tumors (N = 1368).a

Outcome	Age	Odds Ratio	Lower Confidence Limit	Upper Confidence Limit	P, C-Statistic
Venous thromboembolism	45-54 years	0.40	0.08	1.98	.259
	56-66 years	2.66	1.01	7.03	.048 b
	>66 years	1.31	0.41	4.14	.651

aReference group was ≤44 years. bThe bolded value is a significant value (i.e., p < .05).

Discussion

With increasing age of the growing elderly population in the West,[27,28] patients often are frailer, have poorer physiological reserve, and are more susceptible to perioperative complications and poorer follow-up outcomes.[43,44] Although spinal tumors are rare and IDEM tumors only account for 30% of all spinal tumors, an increasing fraction of this population fall into the elderly category.[3,4] With the increase in age, there is a corresponding rise in spinal tumor incidence[5,10,11] and risk of postoperative complications.[45] Therefore, there needs to be an emphasis on understanding how age can influence postoperative complications, which directly translates into increased financial burden, length of stay, and mortality rates.[45] In our study, we analyzed 1368 patients and identified different 30-day postoperative complications the elderly patients were at risk for. Following multivariate adjustment, we identified that elderly patients had a greater risk for VTE complications. There were also no significant differences in other 30-day complications, despite the elderly patients having poorer preoperative comorbidities in terms of diabetes, dyspnea, ASA >3, pulmonary comorbidities, and cardiac comorbidities.

Cancer is a well-recognized risk factor for VTE given their prothrombotic and coagulopathic state.[46] Yoshioka et al showed that patients with spinal tumors and existing neurological deficits such as paralysis are risk factors in developing VTE complications.[47] Elderly age is another factor that resulted in a significant higher incidence of VTE.[48,49] Schoenfeld et al in their retrospective analysis of 27 730 spine surgery patients demonstrated that body mass index >40 kg/m2 and ASA >3 were also independent risk factors for development of VTE.[50] This association between age and VTE was also demonstrated for other spinal procedures, including anterior cervical discectomy and fusion.[51] The influence of age on VTE incidence is likely exacerbated in oncological patients, given that cancer alone is another risk factor for VTE development, up to 20-fold.[52] However, these trends have not been universal as Akeda et al did not find any significant correlation between risk of deep vein thrombosis with age or existing comorbidity in spinal tumor surgeries.[22] This finding may be due to their underpowered analysis given that only 4 out of 14 individuals that showed VTE complications in this study were spinal tumor-related surgery.[22]

Given the overall association between age and VTE complications particularly in IDEM spinal tumor patients, the suggested management includes the use of ultrasound for deep venous thrombosis diagnosis, use of compression stockings, and prophylactic drugs in high-risk patients.[22] In elderly patients, up to 10% to 20% of immediate death is due to VTE, and fatal pulmonary embolism is a preventable VTE consequence that accounts for 1% death of hospitalized patients.[53-57] According to recommended guidelines, patients in our study would be considered high risk as they demonstrate high-risk factors such as age >60 years, acute chronic lung or inflammatory disease, decompensated heart failure, active cancer, and >40 years with a major surgery >45 minutes.[53,54,57] Medical prophylactics for high-risk patients generally include low-dose unfractionated heparin, low-molecular-weight heparin (enoxaparin and dalteparin), and fondaparinux. With high-risk patients, the use of intermittent pneumatic compression over graduated compression stocking is viewed as a more effective mechanical prophylactic device.[53,54] In addition, the risk of deep venous thrombosis without any prophylactic measures are 25% for general surgery and 22% for neurosurgery.[53,54,57]

Patient preoperative morbidity as indicated by the ASA score may help explain why elderly patients (>55 years) were more likely to demonstrate a higher mortality rate and postoperative cardiac complications in univariate analysis of our data. Many of the patients in our study have an ASA score >3, and a higher ASA physical status class generally describes an individual who has more comorbidities, translating into longer hospital stay, higher postoperative mortality rate, and higher risk of myocardial injury.[58] The ASA class is a moderate predictor for the physical status of a patient, but the interrater reliability disagreement was significantly less likely to occur for procedures such as neurosurgery and orthopedic surgery.[58] In our study, differences in complication rates in elderly versus younger age quartiles were ameliorated following multivariate adjustment for confounders, suggesting that perioperative complications in the spinal tumor population is complex and multifactorial, and cannot be attributed to elderly age alone. Indeed, frailty indexes may be more representative of an elderly patient’s underlying comorbidities and physiological reserve, and has been shown to predict mortality and morbidity in older patients in spinal surgery[30,31] and cancer.[59]

Few studies to date have assessed large nationwide databases or registries to determine risk factors for complications following intradural spinal tumors. Karhade et al[60] performed an analysis of the NSQIP database to study patients undergoing spinal tumor surgery, and they evaluated 2207 patients with 36.4% intradural tumor, 51.4% extradural tumor, and 12.3% intramedullary tumor. The authors found that the most common reason for readmission was wound infection/SSI (23.7%) and VTE (12.7%); they found the predictor for readmission was dyspnea, hypertension, extended hospital stay, and preoperative steroid use.[60] In the present study, the rate of unplanned admission was higher in the elderly group (>55 years), and this group was also more likely to demonstrate dyspnea, hypertension, VTE, and wound infection in univariate analysis, but these differences became nonsignificant following multivariate adjustment.

Of interesting note was that aside from VTE, other perioperative complications including wound, pulmonary, renal, urinary tract, cardiac complications, transfusions, and unplanned readmissions were similar between the youngest age quartile and the eldest age quartile. This data suggests VTE is the main age-related complications in patients undergoing surgery for IDEM spinal tumors. As such, age alone should not be a contraindication to surgery in this population as the majority of perioperative morbidity and mortality outcomes are similar across the age quartiles. Our results support the notion that patient selection should focus on the underlying comorbidities of the patient rather than age alone. It is likely that patients who are with greater comorbidities are likely to have poorer outcomes following excisional laminectomy for IDEM tumors, but this remains to be formally investigated.

Limitations

The present study is constrained by several limitations. Patient cases were retrieved from the ACS-NSQIP database using Current Procedural Terminology (CPT) codes. This assumes that CPT codes were accurately recorded for each patient operation. The spinal procedure performed at each center may also be varied, and CPT codes do not account for this heterogeneity. Second, only 30-day perioperative outcomes were collected by ACS-NSQIP, and as such the presented results may not be applicable for long-term follow-up. Other relevant parameters including neurological outcomes, functional outcomes, intraoperative complications, tumor characteristic such as size and histology, as well as data on adjunctive chemotherapy or radiotherapy were not collected in this database, and as such could not be assessed in the present study. The NSQIP database is biased toward predominantly academic centers and may not be representative of results across the nation. Despite these limitations, analysis of the NSQIP database provides a large sample size and in-depth analysis of risk factors for perioperative complications following intradural spinal tumor surgery, which has not been well reported in the literature.

Conclusions

Using the ACS-NSQIP database to analyze IDEM spinal tumor excisional laminectomy, we demonstrated that elderly age to be independently associated with increased incidence of VTE but no difference in other perioperative complications. Our results suggest that elderly patients with an optimal risk profile should not be contraindicated from undergoing surgery for IDEM tumors. This data may help improve preoperative planning, optimization, and postoperative monitoring of patients undergoing excisional laminectomy for extramedullary spinal tumors.