A comparison of readmission and complication rates and charges of inpatient and outpatient multiple-level anterior cervical discectomy and fusion surgeries in the Medicare population

Syed I. Khalid Departments of Neurosurgery and
Rosalind Franklin University of Medicine and Science, Chicago Medical School, North Chicago, Illinois; and
General Surgery, Rush University Medical Center, Chicago;

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Ryan Kelly Georgetown University School of Medicine, Washington, DC

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Rita Wu Rosalind Franklin University of Medicine and Science, Chicago Medical School, North Chicago, Illinois; and

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Akhil Peta Rosalind Franklin University of Medicine and Science, Chicago Medical School, North Chicago, Illinois; and

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Adam Carlton Rosalind Franklin University of Medicine and Science, Chicago Medical School, North Chicago, Illinois; and

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Owoicho Adogwa Departments of Neurosurgery and

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OBJECTIVE

This study aims to assess the relationship of comorbidities and postoperative complications to rates of readmission for geriatric patients undergoing anterior cervical discectomy and fusion (ACDF) involving more than 2 levels on an inpatient or outpatient basis. With the rising costs of healthcare in the United States, understanding the safety and efficacy of performing common surgical interventions (including ACDF) as outpatient procedures could prove to be of great economic impact.Objective This study aims to assess the effect of comorbidities and postoperative complications on the rates of readmission of geriatric patients undergoing multilevel anterior cervical discectomy and fusion (ACDF) procedures (i.e., ACDF involving 3 or more levels) on an inpatient or outpatient basis. Same-day surgery has been demonstrated to be a safe and cost-effective alternative to the traditional inpatient option for many surgical interventions. With the rising costs of healthcare, understanding the safety and efficacy of performing common surgical interventions as outpatient procedures could prove to be of great economic impact.

METHODS

The study population included total of 2492 patients: 2348 inpatients and 144 outpatients having ACDF procedures involving 3 or more levels in the Medicare Standard Analytical Files database. Age, sex, comorbidities, postoperative complications, readmission rates, and surgical procedure charges were compared between both cohorts. For selected variables, logistic regression was used to model odds ratios for various comorbidities against readmission rates for both inpatient and outpatient cohorts. Chi-square tests were also calculated to compare these comorbidities with readmission in each cohort.

RESULTS

Overall complication rates within 30 postoperative days were greater for inpatients than for outpatients (44.2% vs 12.5%, p < 0.001). More inpatients developed postoperative urinary tract infection (7.9% vs 0%, p < 0.001), and the inpatient cohort had increased risk of readmission with comorbidities of anemia (OR 1.52, p < 0.001), smoking (OR 2.12, p < 0.001), and BMI ≥ 30 (OR 1.43, p < 0.001). Outpatients had increased risk of readmission with comorbidities of anemia (OR 2.78, p = 0.047), diabetes mellitus type 1 or 2 (OR 3.25, p = 0.033), and BMI ≥ 30 (OR 3.95, p = 0.008). Inpatients also had increased readmission risk with a postoperative complication of surgical site infection (OR 2.38, p < 0.001). The average charges for inpatient multilevel ACDF were significantly higher than for multilevel ACDF performed on an outpatient basis ($12,734.27 vs $12,152.18, p = 0.0019).

CONCLUSIONS

This study suggests that ACDF surgery involving 3 or more levels performed as an outpatient procedure in the geriatric population may be associated with lower rates of readmissions, complications, and surgical charges.

ABBREVIATIONS

ACDF = anterior cervical discectomy and fusion; BMI = body mass index; CPT = Current Procedural Terminology; DM = diabetes mellitus; DVT = deep vein thrombosis; ICD-9 = International Classification of Diseases, Ninth Revision; MI = myocardial infarction; PE = pulmonary embolism; SASD = State Ambulatory Surgery and Services Database; UTI = urinary tract infection.

OBJECTIVE

This study aims to assess the relationship of comorbidities and postoperative complications to rates of readmission for geriatric patients undergoing anterior cervical discectomy and fusion (ACDF) involving more than 2 levels on an inpatient or outpatient basis. With the rising costs of healthcare in the United States, understanding the safety and efficacy of performing common surgical interventions (including ACDF) as outpatient procedures could prove to be of great economic impact.Objective This study aims to assess the effect of comorbidities and postoperative complications on the rates of readmission of geriatric patients undergoing multilevel anterior cervical discectomy and fusion (ACDF) procedures (i.e., ACDF involving 3 or more levels) on an inpatient or outpatient basis. Same-day surgery has been demonstrated to be a safe and cost-effective alternative to the traditional inpatient option for many surgical interventions. With the rising costs of healthcare, understanding the safety and efficacy of performing common surgical interventions as outpatient procedures could prove to be of great economic impact.

METHODS

The study population included total of 2492 patients: 2348 inpatients and 144 outpatients having ACDF procedures involving 3 or more levels in the Medicare Standard Analytical Files database. Age, sex, comorbidities, postoperative complications, readmission rates, and surgical procedure charges were compared between both cohorts. For selected variables, logistic regression was used to model odds ratios for various comorbidities against readmission rates for both inpatient and outpatient cohorts. Chi-square tests were also calculated to compare these comorbidities with readmission in each cohort.

RESULTS

Overall complication rates within 30 postoperative days were greater for inpatients than for outpatients (44.2% vs 12.5%, p < 0.001). More inpatients developed postoperative urinary tract infection (7.9% vs 0%, p < 0.001), and the inpatient cohort had increased risk of readmission with comorbidities of anemia (OR 1.52, p < 0.001), smoking (OR 2.12, p < 0.001), and BMI ≥ 30 (OR 1.43, p < 0.001). Outpatients had increased risk of readmission with comorbidities of anemia (OR 2.78, p = 0.047), diabetes mellitus type 1 or 2 (OR 3.25, p = 0.033), and BMI ≥ 30 (OR 3.95, p = 0.008). Inpatients also had increased readmission risk with a postoperative complication of surgical site infection (OR 2.38, p < 0.001). The average charges for inpatient multilevel ACDF were significantly higher than for multilevel ACDF performed on an outpatient basis ($12,734.27 vs $12,152.18, p = 0.0019).

CONCLUSIONS

This study suggests that ACDF surgery involving 3 or more levels performed as an outpatient procedure in the geriatric population may be associated with lower rates of readmissions, complications, and surgical charges.

In Brief

This study aims to assess the relationship of comorbidities and postoperative complications to rates of readmission for geriatric patients undergoing anterior cervical discectomy and fusion (ACDF) involving more than 2 levels on an inpatient or outpatient basis. With the rising costs of healthcare in the United States, understanding the safety and efficacy of performing common surgical interventions (including ACDF) as outpatient procedures could prove to be of great economic impact.

Anterior cervical discectomy and fusion (ACDF) was first described by Smith, Robinson, and Cloward in 19583,30 and has since been shown to be a relatively reliable procedure for treatment of many degenerative spinal diseases8 with improved outcomes compared to nonoperative therapy.14,36 Previous literature has shown an associated rise in prevalence of degenerative spinal disorders with an aging population.22 With the proportion of the population over the age of 65 years in the United States projected to increase from 12% in 2000 to 20% by 203031 and the demand for surgical intervention for degenerative spine disease increasing especially in this patient population,27 there has been growing interest in cost-saving strategies. One such cost-saving strategy has been shown in the shifting of traditional in-hospital procedures to ambulatory centers.1 Recent studies have shown that performing similar procedures in an outpatient setting rather than an inpatient setting reduced the average cost by 2- to 3-fold.5 While such savings can be helpful, the safety of transitioning traditional inpatient surgery to outpatient ambulatory procedures remains an important question in the geriatric population (age 65 years or older).

Previous literature has shown outpatient ACDF to be a safe and effective procedure with low postoperative complications—some studies showing no significant differences between inpatient and outpatient outcomes and others showing improved outcomes with outpatient procedures.1,9,10,12,13,17,19–21,24,28,29,32,34 However, most of these studies focused on 1- and/or 2-level ACDF procedures, and few assessed outcomes of multilevel (> 2-level) ACDF performed in an outpatient setting.9,18 This may be because multilevel ACDF has been shown to have greater rates of complications and 30-day readmissions as the number of segments fused increases.6,7,11,33 Previous studies have also typically focused on the overall adult population, with average age of patients being around 50 years old,1,9,17,24 and few have specifically assessed the geriatric population. The geriatric population presents interesting and important considerations regarding the increased rates of postoperative complications and prevalence of comorbidities from spinal procedures that can affect long-term outcomes in this cohort.2,4,25

In the current study, we utilized the Medicare Standard Analytical Files database, derived from Medicare parts A and B, which provide coverage to over 51 million patients, and focused on assessing outcomes, complication rates, and cost differences between inpatient and outpatient multilevel ACDF procedures specific to the geriatric population. Furthermore, we aimed to evaluate the role of comorbidities on postoperative complication rates in order to gain greater insight as to which patients may be most appropriately treated in an outpatient setting.

Methods

Data Collection

Data were acquired from the Medicare Standard Analytical Files database derived from Medicare parts A and B, for the years 2007–2012, which contain 100% of inpatient and outpatient facility records billed to Medicare, and retrospectively analyzed. Patients 65 years of age or older undergoing multilevel ACDF were identified based on International Classification of Diseases, Ninth Revision (ICD-9) diagnosis codes, ICD-9 procedure codes, and Current Procedural Terminology (CPT) codes.

Patients undergoing ACDF were identified by querying the database for coincidence of two of the following CPT codes: 1) CPT-22551 [arthrodesis, anterior interbody, including disc space preparation, discectomy, osteophytectomy and decompression of spinal cord and/or nerve roots] and 2) CPT-22554 [arthrodesis, anterior interbody technique, including minimal discectomy to prepare interspace (other than for decompression)]. Only those cases co-coded with ICD-9 81.63 (fusion or refusion of 4–8 vertebrae) or ICD-9 81.64 (fusion or refusion of 9 or more vertebrae) for fusion of 3 or more levels were included for both cohorts. Inpatients and outpatients were identified using service location modifiers “21” and “22,” respectively. The service location modifier “22” represents discharge occurring from either a hospital or an ambulatory surgery setting without an associated inpatient hospital admission and an absolute length of stay less than 24 hours.

Baseline Demographics

Demographic data for aggregate records included sex and age. Only patients 65 years of age or older were included in the study. Patients were further stratified by age into the following groups to evaluate for disparities in age proportions: 65–69 years, 70–74 years, 75–79 years, 80–84 years, and 85 years or older.

Comorbidities

ICD-9-CM diagnosis codes were used to identify comorbidities as listed in Supplementary Table 1. Comorbidities were noted as the following: anemia, diabetes mellitus (DM), myocardial infarction (MI), atrial fibrillation, pulmonary condition, smoker, and body mass index (BMI) ≥ 30.

Complications

Cohorts were queried to identify patients who had complications leading to readmission within 30 days after discharge based on ICD-9 diagnosis codes as listed in Supplementary Table 2. Complications were noted as the following: urinary tract infection (UTI), surgical site infection, deep vein thrombosis (DVT), pulmonary embolism (PE), and MI.

Statistical Analysis

Descriptive statistics were calculated for age, sex, comorbidities, and postoperative complications. For selected variables, logistic regression was used to model odds ratios for various comorbidities against readmission rates in both inpatient and outpatient cohorts. Chi-square tests were then calculated to compare these comorbidities with readmission in each cohort. The data were analyzed using R statistical software (version 3.4.2, 2017, R Project).

Results

From 2007 through 2012, a total of 2492 geriatric patients (age ≥ 65 years) who underwent multilevel (> 2-level) ACDF were identified. Of this population, 2348 patients (94.2%) were identified as undergoing the procedure on an inpatient basis (inpatients) and 144 (5.8%) as undergoing it on an outpatient basis (outpatients). Female patients accounted for 52.9% (n = 1242) of the inpatient population and 49.3% (n = 71) of the outpatient population.

Common preoperative comorbidities among the whole group included anemia (43.1%), DM type 1 and 2 (46.7%), previous MI (6.3%), atrial fibrillation (14.6%), pulmonary condition (15.2%), smoking (16.7%), and BMI ≥ 30 (27.4%). The inpatient cohort reported more comorbidities of anemia (43.5% vs 36.1%, p < 0.081) and fewer comorbidities of previous MI (4.8% vs 31.3%, p < 0.001) compared with the outpatient group. Further details of the descriptive characteristics can be found in Table 1.

TABLE 1.

Characteristics of patients over 65 years of age undergoing multilevel ACDF surgery

ParameterTotal (n = 2492)Inpatient (n = 2348)Outpatient (n = 144)p Value
Age in yrs<0.023*
 65–69, n (%)1147 (46.0)1073 (45.7)74 (51.4)
 70–74, n (%)753 (30.2)711 (30.3)42 (29.2)
 75–79, n (%)430 (17.3)402 (17.1)28 (19.4)
 80–84, n (%)127 (5.1)127 (5.4)0 (0)
 ≥85, n (%)35 (1.4)35 (1.5)0 (0)
Sex
 Male, n (%)1179 (47.3)1106 (47.1)73 (50.7)<0.04*
 Female, n (%)1313 (52.7)1242 (52.9)71 (49.3)
Comorbidities
 Anemia, n (%)1074 (43.1)1022 (43.5)52 (36.1)0.081
 DM (type 1 or 2), n (%)1164 (46.7)1100 (46.8)64 (44.4)0.575
 MI, n (%)157 (6.3)112 (4.8)45 (31.3)<0.001*
 Atrial fibrillation, n (%)365 (14.6)343 (14.6)22 (15.3)0.825
 Pulmonary condition, n (%)380 (15.2)358 (15.2)22 (15.3)0.992
 Smoker, n (%)415 (16.7)389 (16.6)26 (18.1)0.642
 BMI ≥30, n (%)684 (27.4)643 (27.4)41 (28.5)0.777
Postop complications
 UTI, n (%)186 (7.5)186 (7.9)0 (0)<0.001*
 SSI, n (%)49 (2.0)49 (2.1)0 (0)0.08
 DVT, n (%)37 (1.5)37 (1.6)0 (0)0.129
 PE, n (%)26 (1.0)26 (1.1)0 (0)0.204
 MI, n (%)11 (0.4)11 (0.5)0 (0)0.41
All-cause 30-day readmission, n (%)1055 (42.3)1037 (44.2)18 (12.5)<0.001*
Average charge, $ (SD)12,740.00 (5213.20)12,734.27 (4049.87)12,152.18 (4233.42)0.0019*

SSI = surgical site infection.

Multilevel ACDF refers to ACDF at 3 or more levels.

Statistically significant (p < 0.05)

The total complication rates within the first 30 days after surgery were significantly higher in the inpatient group than in the outpatient group (44.2% vs 12.5%, p < 0.001). In particular, the proportion of patients who developed a postoperative UTI (7.9% vs 0%, p < 0.001) was significantly higher in the inpatient cohort than in the outpatient cohort. The mean value for surgical procedure charges was also found to be significantly higher when multilevel ACDF surgery was performed in an inpatient setting than when it was performed in an outpatient setting ($12,734.27 vs $12,152.18, p = 0.0019).

Readmission outcomes were assessed between outpatient and inpatient groups with respect to various preoperative comorbidities and perioperative complications. Odds ratios were calculated and chi-square tests were performed to assess risk of readmission for each factor based on cohort (outpatient or inpatient). Inpatients had increased risk of readmission with comorbidities of anemia (OR 1.52, 95% CI 1.32–1.76, p < 0.001), pulmonary condition (OR 1.50, 95% CI 1.24–1.80, p < 0.001), smoking (OR 2.12, 95% CI 1.78–2.52, p < 0.001), and BMI ≥ 30 (OR 1.43, 95% CI 1.23–1.68, p < 0.001) (Table 2). Inpatients also had an increased risk of readmission with a postoperative complication of surgical site infection (OR 2.38, 95% CI 1.59–3.55, p < 0.001) but a decreased risk of readmission with PE (OR 0.04, 95% CI 0.00–0.69, p = 0.027) (Table 3).

TABLE 2.

Odds of all-cause readmission following multilevel ACDF surgery in patients over 65 years of age

TotalInpatientOutpatient
ParameterOR95% CIp ValueOR95% CIp ValueOR95% CIp Value
Anemia1.561.35–1.80<0.00011.521.32–1.76<0.00012.781.02–7.610.0465
DM*1.181.02–1.360.02571.151.00–1.340.05433.251.10–9.590.0328
MI0.940.70–1.280.71071.290.94–1.770.11470.060.00–1.000.0502
Atrial fibrillation1.100.90–1.350.33061.130.92–1.380.23310.150.01–2.530.1867
Pulmonary condition1.461.22–1.75<0.00011.501.24–1.80<0.00010.150.01–2.530.1867
Smoker2.051.73–2.43<0.00012.121.78–2.52<0.00010.120.01–2.070.1448
BMI ≥301.461.25–1.70<0.00011.431.23–1.68<0.00013.951.43–10.890.0080

Includes both type 1 and type 2.

TABLE 3.

Odds of all-cause readmission following multilevel ACDF surgery in patients over 65 years of age

TotalInpatientOutpatient
ParameterOR95% CIp ValueOR95% CIp ValueOR95% CIp Value
UTI1.270.98–1.640.06761.210.94–1.570.13977.810.15–405.560.31
SSI2.481.66–3.70<0.00012.381.59–3.55<0.00017.810.15–405.560.31
DVT1.480.87–2.500.14451.420.84–2.400.19407.810.15–405.560.31
PE0.040.00–0.720.02880.040.00–0.690.02677.810.15–405.560.31
MI0.100.01–1.740.11450.100.01–1.660.10797.810.15–405.560.31

Outpatients had increased risk of readmission with comorbidities of anemia (OR 2.78, 95% CI 1.02–7.61, p = 0.047), DM type 1 or 2 (OR 3.25, 95% CI 1.10–9.59, p = 0.033), and BMI ≥ 30 (OR 3.95, 95% CI 1.43–10.89, p = 0.008) (Table 2). Outpatients did not have increased risk of readmission with any of the noted postoperative complications (Table 3).

Discussion

Previous literature, including prospective, retrospective, single-institution, and large database studies, have demonstrated the safety and effectiveness of outpatient 1- and 2-level ACDF procedures compared to traditional inpatient surgery.9,13,17,19,20,24,25,28,29,32 Few studies have evaluated the safety and efficacy of outpatient ACDF procedures in comparison to inpatient surgery in elderly patients undergoing > 3-level ACDF. A recent single-surgeon, single-institution retrospective study by Mullins et al. assessing 282 multilevel ACDF procedures (116 outpatient and 166 inpatient) showed significantly higher rates of complications in the inpatient group compared to the outpatient group for those undergoing 3-level ACDF and no difference in complication rates for 4-level surgery.21 In that study, a total of 246 three-level ACDFs (44.7% outpatient, 55.3% inpatient) and 36 four-level ACDFs (16.7% outpatient, 83.3% inpatient) were analyzed, with overall complication rates of 5.7% for three-level surgery and 19.4% for four-level surgery. The average age of the patients was 50.2 years, with outpatients noted to be significantly younger than inpatients (47.5 vs 53 years, respectively). In the present study, we performed a retrospective analysis of data from 2492 cases involving geriatric patients, comparing inpatient versus outpatient multilevel ACDF. The inpatient cohort was found to have an overall greater tendency for readmission with postoperative complications within 30 days compared to the outpatient cohort (44.2% vs 12.5%, p < 0.001). Specifically, the frequency of postoperative UTI (7.9% vs 0%, p < 0.001) was significantly higher in the inpatient group compared with the outpatient group, while the rates of surgical site infection (2.1% vs 0%, p = 0.080), DVT (1.6% vs 0%, p = 0.129), and PE (1.1% vs 0%, p = 0.204) were also higher but did not reach statistical significance.

While some early studies have illustrated that ACDF procedures can be performed safely in an ambulatory setting with rates of favorable outcomes similar to those achieved with in-hospital surgery,10,12,34 other more recent studies suggest that postoperative complication rates may be lower for outpatient procedures. In a retrospective study of the National Surgical Quality Improvement Program (NSQIP) database, Fu et al.,9 analyzing 21,025, 1- and 2-level ACDF procedures (4597 outpatient, 16,428 inpatient), found a significantly lower incidence of postoperative complications in the outpatient cohort than in the inpatient group (1-level: 1.01% vs 4.05%; 2-level: 1.47% vs 3.94%). Notably, comparison of the outpatient and inpatient cohorts showed significantly lower incidences of pulmonary complications (1-level: 0.22% vs 1.36%; 2-level 0.28% vs 1.40%), reoperation (1-level: 0.28% vs 1.53%; 2-level: 0.49% vs 1.63), blood transfusion (1-level: 0.09% vs 0.82%), and UTI (1-level: 0.60% vs 2.22%) in the outpatient cohort. A later retrospective study of 10,080 patients who underwent 1- or 2-level ACDF procedures by McClelland et al.19 was based on the Nationwide Inpatient Sample (NIS) and the State Ambulatory Services Database (SASD) of New Jersey and demonstrated a significant decrease in postoperative durotomy, paraplegia, infection, hematoma/seroma, respiratory complications, acute post-hemorrhagic anemia, and red blood cell transfusion in the outpatient cohort. The average age of the outpatients in this study was 47.7 years and the average age of the inpatients was 51 years. Our results, though specific to our geriatric population, showed a similar decrease in overall postoperative complications leading to readmission within 30 days for the inpatient cohort (44.2% vs 12.5% for the outpatient cohort, p < 0.001). Specifically, rates of postoperative complications of UTI (7.9% vs 0%, p < 0.001) were significantly higher in the inpatient ACDF group than in the outpatient group. Furthermore, the odds of readmission were significantly increased in inpatients who had postoperative complications of surgical site infection (OR 2.38, p < 0.001) and decreased risk in patients with PE pulmonary embolism (OR 0.04, p = 0.0267). The inpatients who developed PE all developed it during their initial hospitalization, and no patient was readmitted for this complication.

Previous studies assessing outcomes of various spinal surgeries for degenerative spinal disorders have shown increased risk of complications and morbidity in patients with increased comorbidity burden, particularly those with higher BMI, American Society of Anesthesiologists (ASA) comorbidity grades greater than 2, and pulmonary conditions.15,26 In regard to ACDF, a retrospective study of the Health and Human Services’ Agency for Healthcare Research and Quality State Inpatient Databases (SID), the State Ambulatory Surgery and Services Databases (SASD), and the State Emergency Department Databases (SEDD) by Purger et al., including data from 50,131 patients undergoing 1-, 2-, or 3- level ACDF procedures (3135 SID inpatient; 46,996 SASD outpatient), showed that readmission rates within 30 postoperative days were less likely in the outpatient cohort than in the inpatient group regardless of baseline Charlson Comorbidity Index (CCI) score, a weighted comorbid illness severity score. Outpatients who had a CCI of 0% had a 1.58% risk of readmission compared to 2.94% for inpatients with the same CCI classification. Outpatients who had a CCI > 1% had a 1.9% risk of readmission compared to 5.96% for inpatients. Inpatients were significantly older (average age 53 years vs 48 years) at baseline and had higher CCI scores (0.37% vs 0.17%) than outpatients. Our current study demonstrates that the presence of comorbidities such as anemia (OR 1.52, p < 0.001), pulmonary condition (OR 1.50, p < 0.001), smoking (OR 2.12, p < 0.001), and BMI ≥ 30 (OR 1.43, p < 0.001) in the inpatient cohort and anemia (OR 2.78, p = 0.047), DM type 1 or 2 (OR 3.25, p = 0.033), and BMI ≥ 30 (OR 3.95, p = 0.008) in the outpatient cohort increases the odds of readmission in geriatric patients. Analysis of the overall baseline characteristics of this study population showed greater prevalence of comorbid anemia in inpatients than in outpatients (43.5% vs 36.1%, p < 0.081) and lower prevalence of previous MI (4.8% vs 31.3%, p < 0.001). The effect of comorbidities on the readmission rates of geriatric patients undergoing multilevel ACDF procedures was seen in our population regardless of the inpatient or outpatient status of the patient. These findings suggest that comorbidities should be taken into consideration when selecting geriatric patients to undergo multilevel ACDF in the ambulatory setting versus a traditional hospital.

The number of ACDF procedures performed nationally increased 800% between 1990 and 2000, with the costs associated increasing from $672 million to $2.1 billion within that same time span.16,23 An early study by Silvers et al.29 on 50 outpatient ACDF surgeries showed an average $1800 savings per patient with a total reduction of > $900,000 in hospital costs. Similarly, a later study by Purger et al.24 on 50,131 ACDF patients (46,996 inpatients, 3135 outpatients) demonstrated not only significantly lower average costs with outpatient versus inpatient ACDF ($9305.57 vs $15,624.63), but also significantly lower 90-day cumulative charges ($33,362.51 outpatient vs $74,667.04 inpatient). However, these studies were limited to 1- and 2-level ACDF procedures. In a more recent study, Mullins et al.21 assessed 1-, 2-, 3-, and 4- level ACDF procedures and showed a significant 74% savings in commercial insurance reimbursements with outpatient surgery ($18,095 average reimbursement for treatment in the outpatient setting vs $24,492 for treatment in the inpatient setting). The present study shows a significant decrease in average surgical procedure charges with multilevel ACDF performed in an outpatient setting ($12,152.18) compared to inpatient surgery ($12,734.27, p = 0.0019). This decrease in hospital cost can help with monetary allocation and provide hospitals with more resources that can be distributed to other services. These figures alone do not fully account for the total actual savings realized by shifting this procedure from inpatient to outpatient basis, as they are for the surgical charges alone and do not account for the additional downstream savings of not having an associated inpatient stay.

Limitations

Although the use of administrative data allows access to a large number of medical visits nationwide and longitudinal tracking of such patients through distinct identifiers based on a standardized coding system, important limitations must be considered. Specifically, as the intent of most administrative data is typically for financial and administrative use rather than research purposes, the detail and accuracy of information may vary. For example, this type of data may be less reliable for information on events not resulting in use of a diagnostic code, such as nausea. Moreover, application of the ICD-9 codes may be subject to interpretation of physician records by the medical reviewer entering the codes and changing coding practices. Administrative data also do not provide qualifiable details on severity of disease states or patient-reported outcome scores or allow for standardization of treatment protocols or surgeon technique or expertise, which may mask certain confounding factors. The significantly smaller size of the outpatient group and the lack of any instances of postoperative complications alongside readmission have the potential to skew the data as well.

As a result of these data limitations, there is no way to perform subpopulation analysis to look at factors such as treatment indication, different groups of pathology, or other measures such as the length of the inpatient stay, and the exact primary cause for which a given patient was readmitted, which would all provide meaningful clinical insight. For those reasons this study is largely limited to economic conclusions and implications for in-depth exploration of the safety of outpatient ACDF from a clinically focused perspective in the future.

Conclusions

The current study demonstrates that multilevel ACDF procedures can be performed safely and effectively in an outpatient setting with overall reduction in 30-day postoperative complication rates compared to traditional inpatient surgery in the geriatric population. To our knowledge, this is one of the first studies assessing the potential role of comorbidities in readmission rates and offers important considerations for selecting geriatric patients to undergo multilevel ACDF procedures.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: Adogwa, Khalid. Acquisition of data: Adogwa, Khalid, Wu, Peta, Carlton. Analysis and interpretation of data: all authors. Drafting the article: Khalid, Wu, Peta, Carlton. Critically revising the article: Adogwa, Khalid, Kelly. Reviewed submitted version of manuscript: Adogwa, Khalid, Kelly. Statistical analysis: Kelly, Wu, Peta, Carlton. Administrative/technical/material support: Adogwa, Khalid. Study supervision: Adogwa, Khalid.

Supplemental Information

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Supplemental material is available with the online version of the article.

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