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Original Article

Rates, Causes, and Predictive Factors of Hospital Readmissions After Spine Surgery for Lumbar Spinal Stenosis: A Nationwide Retrospective Cohort Study

Lingxiao Chen1,2,3,*orcid, Jiaming Ding1,*orcid, Zhuo Chen1orcid, David B. Anderson4orcid, Maja R. Radojčić3orcid, Ruiyuan Zheng1orcid, Qingyu Sun1orcid, Wenjian Yuan1orcid, Jiuxiao Sun1orcid, Runhan Fu1orcid, Baoyi Shi5orcid, Yujie Chen6,7orcid, Lei Qi1orcid, Hengxing Zhou1,8,9orcid, Shiqing Feng1,8orcid
Neurospine 2025;22(2):523-539.
Published online: June 30, 2025

1Department of Orthopaedics, Qilu Hospital of Shandong University, Shandong University Centre for Orthopaedics, Advanced Medical Research Institute, Cheeloo College of Medicine, Shandong University, Jinan, China

2Department of Biostatistics, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, China

3Division of Psychology and Mental Health, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK

4School of Health Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney Musculoskeletal Health, Patyegarang Precinct, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia

5Department of Biostatistics, Mailman School of Public Health, Columbia University, NY, USA

6Program in Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, ON, Canada

7Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, ON, Canada

8The Second Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, China

9Center for Reproductive Medicine, Shandong University, Jinan, China

Corresponding Author Shiqing Feng Department of Orthopaedics, Qilu Hospital of Shandong University, Shandong University Centre for Orthopaedics, Advanced Medical Research Institute, Cheeloo College of Medicine, Shandong University, No. 107 Wenhua West Road, Lixia District, Jinan, Shandong 250012, China Email: shiqingfeng@sdu.edu.cn
Co-corresponding Author Lei Qi Department of Orthopaedics, Qilu Hospital of Shandong University, No. 107 Wenhua West Road, Lixia District, Jinan, Shandong 250012, China Email: qilei@sdu.edu.cn

Lingxiao Chen and Jiaming Ding contributed equally to this study as co-first authors.

• Received: November 30, 2024   • Revised: February 21, 2025   • Accepted: March 5, 2025

Copyright © 2025 by the Korean Spinal Neurosurgery Society

This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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  • Objective
    This study aimed to determine the rates, causes, and predictive factors of readmissions at different periods following spine surgery, up to 180 days.
  • Methods
    This study utilized data from the 2018 to 2019 Nationwide Readmissions Database and included four postoperative periods: 0 to 7 days, 8 to 30 days, 31 to 90 days, and 91 to 180 days. The causes of readmissions and potential predictive factors were systematically identified. All analyses were performed for each period.
  • Results
    For the 180,281 patients (mean age, 65.4 years) included, 2.4% were readmitted between 0 and 7 days, 3.5% between 8 and 30 days, 3.7% between 31 and 90 days, and 4.3% between 91 and 180 days (cumulative rates: 2.4%, 5.9%, 9.3%, and 12.1%, respectively). The causes of readmissions varied across different periods: surgical site-related causes predominated within the first 30 days, whereas nonsurgical site-related causes were more prevalent from 31 to 180 days; other surgical care complication (e.g., infection) was the most prevalent cause between 0 and 7 days (10.7%) and between 8 and 30 days (29.2%), while spondylopathies/spondyloarthropathy (e.g., spinal stenosis) were the leading causes between 31 and 90 days (12.6%) and between 91 and 180 days (17.5%). The predictive factors associated with readmissions also varied across different periods. For example, patients who underwent fusion was associated with a decreased risk of readmissions between 31 and 180 days (e.g., between 91 and 180 days: odds ratio [OR], 0.79; 95% confidence interval [CI], 0.72–0.86; p<0.001), rather than between 0 and 30 days (e.g., between 0 and 7 days: OR, 0.99; 95% CI, 0.90–1.08; p=0.81).
  • Conclusion
    About 6% of patients with lumbar spinal stenosis who underwent spine surgery were readmitted within 30 days and 12% by 180 days. The causes of readmissions and predictive factors varied by period, providing valuable insights for quality improvement efforts and the burden of readmission reductions.
  • Keywords: Lumbar spinal stenosis, Spine surgery, Readmission, Cause, Predictive factor, Period
Lumbar spinal stenosis (LSS) is a common cause of low back pain and associated disability [1]. Although most patients with LSS are treated in primary care, not all receive satisfactory treatment responses, which can lead to hospitalization and spine surgery [2]. In the United States (US), hospitalizations for LSS increased by 19.9% between 2016 and 2019 [3]. Readmissions after spine surgery for LSS have also remained high; reducing these readmissions can improve healthcare quality and decrease healthcare costs [4]. Although several studies have previously assessed readmissions after spine surgery for patients with LSS, these studies have had key limitations, namely: single-site inclusions [5,6], restrictions to a single payer system [7-9], and data being now out of date [7-10]. Some studies have used nationally representative data to explore readmissions after elective lumbar spine surgery [11-13]. However, these studies combined multiple spinal diseases (e.g., one study included lumbar disc herniation, lumber stenosis, acquired spondylolisthesis, and degeneration of lumbar or lumbosacral intervertebral disc [11]), which may bias the results due to the population heterogenicity [14]. Additionally, patients with LSS are usually not young, which may require an extended recovery period [15]. Previous relevant studies often assessed 30- or 90-day readmissions, but monitoring longer-term outcomes following surgery is required to better understand surgical quality and safety [16]. This need for extended monitoring was endorsed by the National Institutes of Health and the American College of Surgeons in 2016 [17]. Moreover, studies in other areas have emphasized that the causes and predictive factors of readmissions may vary across different periods after surgery [18-20]. This information is useful for clinicians and policymakers in their efforts to reduce and manage readmissions, as different strategies may be needed at different periods after surgery.
Therefore, in this nationally representative retrospective cohort study of patients with LSS who underwent spine surgery, we determined the rates, causes, and predictive factors of readmissions at different periods following spine surgery, up to 180 days.
The study was reported following the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) reporting guideline [21]. As this was a secondary analysis of publicly available deidentified databases, Institutional Review Board approval and patient written informed consent were not required as it did not involve human participants.
1. Data Sources
The data used in this study came from the Nationwide Readmissions Database (NRD), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality [22]. It provides nationally representative data on hospital readmissions in the US. For example, the 2019 NRD data account for 61.8% of the total US resident population and 60.4% of all US hospitalizations [23]. When deciding which data waves to include, 2 types of issues were considered. First, the diagnosis and procedure groups file, available in the NRD since 2018, is required because the Clinical Classifications Software Refined (CCSR) for the International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) diagnoses are needed to determine the causes of readmissions [24,25]. Second, the coronavirus disease 2019 lockdown significantly impacted health service use, potentially providing biased estimates if data from the pandemic period was included [26]. Therefore, this study included adults over 18 years old across two annual waves (2018 and 2019).
2. Outcomes
Primary outcomes included the rates, causes, and predictive factors of first readmissions following spine surgery (identified through ICD-10 Procedure Coding System [ICD-10-PCS]; detailed in Supplementary Table 1) in patients with LSS (identified through ICD-10-CM; detailed in Supplementary Tables 2 and 3) [19]. Based on the discharge date of initial hospitalization, 4 periods were included: 0 and 7 days, 8 and 30 days, 31 and 90 days, and 91 and 180 days after the initial hospitalization [19]. Patients who died during the initial hospitalization were excluded as the proportion of death is small (detailed in Fig. 1). To ensure accurate analysis of the NRD dataset, it is important to consider the issue of immortal time bias [27]. For instance, patients admitted in December may not have sufficient follow-up time to observe a 30-day follow-up. To mitigate this potential bias, we have employed the following strategy: (1) exclusion of patients admitted in December for the analysis of 7 and 30 days; (2) exclusion of patients admitted from October to December for the analysis of 90 days; (3) exclusion of patients admitted from July to December for the analysis of 180 days [19].
Causes of readmissions were defined based on the principal diagnosis category (grouped through CCSR for ICD-10-CM diagnoses; detailed in Supplementary Tables 4 and 5) [28]. The CCSR for ICD-10-CM diagnoses aggregates more than 70,000 ICD-10-CM diagnosis codes into over 530 clinically meaningful categories. Version 2024.1 was used and can handle ICD-10-CM codes from October 2015 through September 2024.
Potential predictive factors were identified and confirmed based on prior literature (detailed in the Supplementary Methods) and their identifiability in the NRD. A total of 24 predictive factors (detailed in Supplementary Methods) were explored: age, sex, insurance type, median household income, patient location, day of admission, length of hospital stay, discharge status, admission type, Elixhauser Comorbidity Index [29], type of surgery, depression, anxiety, rheumatoid arthritis, osteoarthritis, osteoporosis, overweight, obesity, hypertriglyceridemia, hypertension, alcohol use disorders, drug use disorders, smoking, and sleep disorders.
3. Statistical Analysis
For each period, rates and causes of readmissions were reported as proportions; multivariable logistic regression was used to examine the association (reported as odds ratio [OR] with 95% confidence interval [CI]) between potential predictive factors and the readmission, with adjustments for all variables. The cumulative readmission rates (7 days, 30 days, 90 days, and 180 days) and subgroup (based on those mentioned above potential predictive factors) results were also estimated to facilitate communication. To ensure causes of readmissions meet the interests of clinicians and policymakers, a three-level hierarchy was used to represent them: level one, surgical site-related and nonsurgical site-related causes; level two, categories through CCSR for ICD-10-CM diagnoses; level three, conditions through ICD-10-CM coding system.
As the NRD collected data through the complex sampling strategy, weights were used to ensure that the estimates were nationally representative, and weights and design variables were included to obtain unbiased estimates and standard errors [30]. Complete case analysis was performed as the proportion of missing data was small (detailed in Supplementary Table 6). Based on the requirements for publishing with HCUP data, cell sizes less than or equal to 10 were not reported. The significance was defined as 2-sided p-value at 0.05. Data were analyzed through Stata version 17.0 (StataCorp LLC, College Station, TX, USA) and IBM SPSS Statistics ver. 27.0 (IBM Co., Armonk, NY, USA).
The analysis sample included 180,281 patients (Fig. 1). Characteristics of included patients are presented in Table 1. The study participants had a mean age of 65.4 years. 51.7% of the participants were female, 85.6% had at least one comorbidity, and 78.8% underwent fusion.
1. Readmissions Between 0 and 7 Days
Of 2.4% of the participants readmitted, the top ten causes (Table 2) were: other surgical care complication (e.g., infection) (10.7%), postoperative nervous system complication (e.g., hematoma and seroma of a nervous system structure) (7.9%), septicemia (6.8%), nervous system pain and pain syndromes (6.0%), spondylopathies/spondyloarthropathy (e.g., spinal stenosis) (5.8%), postoperative musculoskeletal system complication (e.g., hematoma and seroma of a musculoskeletal structure) (4.4%), other nervous system disorders (3.3%), acute pulmonary embolism (2.6%), urinary tract infections (2.5%), and intestinal obstruction and ileus (2.3%). Among the ten causes listed above, the proportion of surgical site-related complications is higher than that of nonsurgical site-related complications (28.9% vs. 23.3%, p<0.001) (Supplementary Table 7). At level 3, the top 3 conditions were infection (8.3%), acute postsurgical pain (5.9%), and hematoma and seroma of a nervous system structure (4.5%).
Estimates for statistically significant predictive factors are provided in Table 3, while estimates for other predictors are detailed in Supplementary Table 8. Several predictive factors were identified as being associated with an increased risk of readmissions. For example, patients aged 85 years or older had a higher risk compared to those aged 18 to 44 years (OR, 1.59; 95% CI, 1.18 to 2.15; p=0.003). Several predictive factors were identified as being associated with a reduced risk of readmissions. For example, being female compared to male was associated with a reduced risk (OR, 0.78; 95% CI, 0.72–0.84; p<0.001).
2. Readmissions Between 8 and 30 Days
Of 3.5% of the participants readmitted, the top 10 causes (Table 4) were: other surgical care complication (e.g., infection) (29.2%), spondylopathies/spondyloarthropathy (e.g., spinal stenosis) (7.7%), septicemia (6.2%), internal orthopedic device or implant complication (4.5%), postoperative nervous system complication (e.g., hematoma and seroma of a nervous system structure) (4.2%), postoperative musculoskeletal system complication (e.g., hematoma and seroma of a musculoskeletal structure) (3.4%), acute pulmonary embolism (3.4%), acute renal failure (1.9%), urinary tract infections (1.9%), and other nervous system disorders (e.g., toxic encephalopathy) (1.7%). Among the 10 causes listed above, the proportion of surgical site-related complications is higher than that of nonsurgical site-related complications (41.4% vs. 22.7%, p<0.001) (Supplementary Table 7). At level 3, the top 3 conditions were infection (22.3%), disruption of wound (5.4%), and sepsis (4.3%).
Estimates for statistically significant predictive factors are provided in Table 3, while estimates for other predictors are detailed in Supplementary Table 8. Several predictive factors were identified as being associated with an increased risk of readmissions. For example, discharge to home health care compared to routine discharge was associated with an increased risk (OR, 1.24; 95% CI, 1.14–1.35; p<0.001). Several predictive factors were identified as being associated with a reduced risk of readmissions. For example, having private insurance compared to Medicare was associated with a reduced risk (OR, 0.72; 95% CI, 0.65–0.80; p<0.001).
3. Readmissions Between 31 and 90 Days
Of 3.7% of the participants readmitted, the top ten causes (Table 5) were: spondylopathies/spondyloarthropathy (e.g., spinal stenosis) (12.6%), other surgical care complication (e.g., injection) (11.4%), internal orthopedic device or implant complication (6.3%), osteoarthritis (6.0%), septicemia (5.3%), postoperative musculoskeletal system complication (e.g., hematoma and seroma of a musculoskeletal structure) (2.0%), heart failure (1.9%), pneumonia (1.9%), postoperative nervous system complication (e.g., hematoma and seroma of a nervous system structure) (1.8%), and urinary tract infections (1.7%). Among the ten causes listed above, the proportion of nonsurgical site-related complications is higher than that of surgical site-related complications (29.3% vs. 21.4%, p<0.001) (Supplementary Table 7). At level three, the top three conditions were infection (8.2%), spinal stenosis (6.0%), and sepsis (3.5%).
Estimates for statistically significant predictive factors are provided in Table 6, while estimates for other predictors are detailed in Supplementary Table 9. Several predictive factors were identified as being associated with an increased risk of readmissions. For example, patients aged 85 years or older had a higher risk compared to those aged 18 to 44 years (OR, 1.42; 95% CI, 1.09–1.84; p=0.009). Several predictive factors were identified as being associated with a reduced risk of readmissions. For example, having private insurance compared to Medicare was associated with a reduced risk (OR, 0.79; 95% CI, 0.71–0.89; p<0.001).
4. Readmissions Between 91 and 180 Days
Of 4.3% of the participants readmitted, the top 10 causes (Table 7) were: spondylopathies/spondyloarthropathy (e.g., spinal stenosis) (17.5%), osteoarthritis (16.7%), septicemia (4.7%), internal orthopedic device or implant complication (5.4%), postoperative musculoskeletal system complication (e.g., hematoma and seroma of a musculoskeletal structure) (2.5%), heart failure (2.1%), cardiac dysrhythmias (1.8%), other surgical care complication (e.g., infection) (1.7%), coronary atherosclerosis and other heart disease (1.7%), and pneumonia (1.5%). Among the ten causes listed above, the proportion of nonsurgical site-related complications is higher than that of surgical site-related complications (46.04% vs. 9.72%, p<0.001) (Supplementary Table 7). At level 3, the top 3 conditions were unilateral primary osteoarthritis of hip (9.2%), spinal stenosis (8.7%), and unilateral primary osteoarthritis of knee (4.9%).
Estimates for statistically significant predictive factors are provided in Table 6, while estimates for other predictors are detailed in Supplementary Table 9. Several predictive factors were identified as being associated with an increased risk of readmissions. For example, patients aged 85 years or older had a higher risk compared to those aged 18 to 44 years (OR, 1.50; 95% CI, 1.11–2.03; p=0.008). Several predictive factors were identified as being associated with a reduced risk of readmissions. For example, having private insurance compared to Medicare was associated with a reduced risk (OR, 0.78; 95% CI, 0.70–0.87; p<0.001).
5. Cumulative Readmission Rates
The cumulative readmission rates at 7, 30, 90, and 180 days were 2.4%, 5.9%, 9.3%, and 12.1% respectively (detailed in Supplementary Table 10). These rates varied a lot across different subgroups. For example, the lowest rate was 7.6% in patients with an Elixhauser Comorbidity Index score of 0, while the highest rate was 25.7% in patients transferred to a short-term hospital.
1. Principal Findings
This large nationally representative retrospective cohort study showed that about 6% of patients with LSS who underwent spine surgery were readmitted within 30 days and 12% by 180 days. The causes of readmissions varied across different periods: surgical site-related causes predominated within the first 30 days, whereas nonsurgical site-related causes were more prevalent from 31 to 180 days. Considering CCSR for ICD-10-CM diagnoses, other surgical care complication (e.g., infection) was the most prevalent cause within the first 30 days, whereas spondylopathies/spondyloarthropathy (e.g., spinal stenosis) became the most prevalent cause from 31 to 180 days. Considering conditions directly identified by the ICD-10-CM coding system, infection was the most prevalent cause within the first 90 days, whereas unilateral primary osteoarthritis of hip became the most prevalent cause from 91 to 180 days. The predictive factors associated with readmissions also varied across different periods. For example, patients who underwent fusion was associated with a decreased risk of readmissions between 31 and 180 days, rather than between 0 and 30 days.
2. Comparison With Previous Studies
We systematically searched (detailed in Supplementary Methods) for studies focused on readmissions in US patients with LSS who underwent spine surgery and identified five relevant studies. Therefore, we compared the rates of readmissions, causes of readmissions, and predictive factors of readmissions from our study with these 5 studies [5,7-10].
For estimating rates of readmissions, three studies reported 30-day readmission rates, with estimates of 9.1%, 3.7%, and 4.0% [5,7,10]. One study reported a 90-day readmission rate, with an estimate of 7.2% [5]. One study reported a 1-year readmission rate, with an estimate of 9.7% in patients undergoing fusion with decompression and 7.2% in patients undergoing decompression alone [8]. Another study reported a 1-year readmission rate with an estimate of 17.5% [9]. These differences, either within different studies or compared with ours, could be due to the following explanations (detailed in Supplement Methods): firstly, variations in inclusion and exclusion criteria. For example, while Deyo et al. [7] and Modhia et al. [8] broadly categorized surgical procedures as “decompression” or “fusion” without providing detailed coding specifications, and Basques et al. [10] relied on ICD-9-CM codes, our study used precise ICD-10-PCS codes to identify specific procedures such as “discectomy,” “diskectomy,” “lamilaminectomy,” and “laminotomy”; secondly, differences in the representativeness of the population. Prior studies, such as those by Deyo et al. [7] and Ong et al. [9], were limited to Medicare beneficiaries aged 65 and older, while Ilyas et al. [5] focused on a single-center cohort. In contrast, our study utilized the NRD database, which provides nationally representative data on hospital readmissions in the US. And thirdly, the timeframes for recruiting patients. Early studies, such as Ilyas et al. [5], included data from 2014–2015 and focused solely on readmissions within 90 days after surgery, without evaluating long-term outcomes. Our study used nationally representative data and adhered to strictly defined inclusion and exclusion criteria. It provided estimates at different periods after surgery, facilitating further comparison with estimates from other countries. The persistent rise in readmission rates indicates that quality improvement efforts to reduce the burden of readmissions should continue for at least 180 days after spine surgery.
For analyzing causes of readmissions, the study by Ilyas et al. [5] reported a binary cause (i.e., surgical and nonsurgical) for 90-day readmissions, while the study by Basques et al. [10] reported suspected reasons for 30-day readmissions. Our study extended previous studies through 2 aspects. Firstly, our study used a systematic method to define causes. Secondly, our study reported these causes at different periods after surgery, allowing us to observe relevant changes over time. Contrary to expectations, infections peaked between 8 and 30 days rather than in the initial 7 days, which may indicate insufficient management of postoperative infections. Although current guidelines acknowledge the need for managing postoperative infections, they do not provide specific strategies [31,32]. Thus, one feasible approach is to educate patients on the signs and symptoms of surgical site infections prior to hospital discharge, enabling them to seek appropriate and timely care at home and potentially preventing some readmissions. The reasons why infections are most common between 8 and 30 days after surgery remain unclear. One potential direction for future studies is to conduct genomic-based microbial tracking, starting from the built environment (i.e., the operating room), through the patient’s own microbiome, and ultimately to the surgical site [33]. This approach could help elucidate the true pathogenesis of infections and enable the development of more targeted interventions. A potential reason why unilateral primary osteoarthritis of the hip became the most prevalent cause between 91 and 180 days could be related to the hip-spine syndrome [34]. This condition suggests that the pathological changes caused by degenerative diseases in both the hip and the spine may be interrelated. Although the exact reason should be further explored, surgeons should communicate this type of readmission to patients.
For analyzing predictive factors of readmissions, the previous 5 studies each included at least one factor, but none of them comprehensively explored this area [5,7-10]. Our study identified potential predictive factors by systematically reviewing prior literature. The results indicated that the role of some predictors was inconsistent across different periods. For example, patients with alcohol use disorders were associated with a higher risk of readmission after 90 days after surgery. Although we could not identify the reason in the NRD dataset, future studies should assess whether certain changes, such as behavioral modifications, occurred in these patients at specific time points after surgery to improve management in specific subpopulations. We broadened the definition of comorbidity by using a systematic approach rather than selecting a few specific types of conditions, and the consistent results across different periods showed that 2 or more comorbidities were associated with increased readmissions, and the association became stronger as the number of comorbidities increased. This information highlights the need for ongoing management of patients with a high number of comorbidities. We also assessed the role of the type of surgery and the results appear to contradict traditional thinking as fusion being associated with a higher risk of readmission compared to decompression alone. A previous study found that patients who underwent fusion for LSS had a higher 1-year readmission rate compared to those who had decompression alone (9.7% vs. 7.2%, p=0.03) [8]. One potential reason could be spinal instability. A previous randomized controlled trial by Ghogawala et al. [35] reported the cumulative risk of reoperation in both the decompression-only and fusion groups. The findings indicated that patients in the decompression-only group had a higher risk of early reoperation, beginning as early as 4 months post-surgery, due to instability. Surgeons should effectively communicate this information to patients to help guide the selection of the most appropriate surgical approach.
3. Limitations
Several limitations should be mentioned. Firstly, the NRD could not track patients who were readmitted to another state, so the readmission rates may be underestimated [23]. Secondly, the NRD is an administrative database without data linkage to other databases. Therefore, variables requiring additional tests, such as genetic factors, those needing patient responses, such as quality of life, or data from other healthcare settings, such as prescriptions from general practice, could not be included in this study. Some of these variables are potential predictive factors (detailed in Supplementary Methods), which should be explored further. Thirdly, some lifestyle factors were defined through the ICD-10-CM coding system, which may bring biases. For example, using a self-reported survey, smoking status can be categorized as nonsmoker, former smoker, or current smoker, with the current smoker group further classified by varying levels of smoking intensity. This approach provides more comprehensive information compared to the binary classification available through the ICD-10-CM coding system.
About 6% of patients with LSS who underwent spine surgery were readmitted within 30 days and 12% by 180 days. The causes of readmissions and predictive factors varied by period, providing valuable insights for quality improvement efforts aimed at reducing the burden of readmissions.
Supplementary Methods and Supplementary Tables 1-10 are available at https://doi.org/10.14245/ns.2449316.658.
Supplementary Methods.
ns-2449316-658-Supplementary-Methods.pdf
Supplementary Table 1.
Details to define spine surgery
ns-2449316-658-Supplementary-Table-1.pdf
Supplementary Table 2.
Details to define lumber spinal stenosis
ns-2449316-658-Supplementary-Table-2.pdf
Supplementary Table 3.
Details to define the exclusion criteria
ns-2449316-658-Supplementary-Table-3.pdf
Supplementary Table 4.
Details to define readmission causes (0-7 days and 8-30 days)
ns-2449316-658-Supplementary-Table-4.pdf
Supplementary Table 5.
Details to define readmission causes (31-90 days and 91-180 days)
ns-2449316-658-Supplementary-Table-5.pdf
Supplementary Table 6.
Missing data
ns-2449316-658-Supplementary-Table-6.pdf
Supplementary Table 7.
Comparison between surgical site-related and nonsurgical site-related causes of readmission
ns-2449316-658-Supplementary-Table-7.pdf
Supplementary Table 8.
Remaining predictive factors a of readmissions at different periods (0-7 days and 8-30 days)
ns-2449316-658-Supplementary-Table-8.pdf
Supplementary Table 9.
Remaining predictive factors a of readmissions at different periods (31-90 days and 91-180 days)
ns-2449316-658-Supplementary-Table-9.pdf
Supplementary Table 10.
Cumulative Readmission Rates
ns-2449316-658-Supplementary-Table-10.pdf

Conflict of Interest

The authors have nothing to disclose.

Funding/Support

LC is funded by the Taishan Scholars Program of Shandong Province-Young Taishan Scholars (tsqn 202408347), Shandong Provincial Natural Science Fund for Excellent Young Scientist Fund Program (Overseas) (2025HWYQ017) and Shandong Provincial Natural Science Foundation (ZR2024QH573). MRR is funded by the National Institute for Health and Social Care (NIHR) Manchester Biomedical Research Centre (NIHR203308). The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care. LQ is funded by the Natural Science Foundation of Shandong Province (ZR2024ZD23). HZ is funded by Cutting Edge Development Fund of Advanced Medical Research Institute (Shandong University). SF is funded by Taishan Scholars Program of Shandong Province-Pandeng Taishan Scholars (tspd20210320).

Author Contribution

Conceptualization: LC, LQ, HZ, SF; Formal analysis: LC, JD, ZC; Investigation: JD, ZC, RZ, QS, WY, JS, RF; Methodology: LC, DBA, MRR; Project administration: LQ, HZ, SF; Writing – original draft: LC, JD, ZC; Writing – review & editing: LC, JD, ZC, DBA, MRR, RZ, QS, WY, JS, RF, BS, YC, LQ, HZ, SF.

Fig. 1.
Flowchart of patient inclusion and exclusion. *Patient Linkage Number is a data element used to associate all hospitalizations associated with a unique patient to identify discharges belonging to the same patient. To identify index events (the starting point for analyzing repeat hospitalizations), we excluded subsequent hospitalizations. LSS, lumbar spinal stenosis.
ns-2449316-658f1.jpg
Table 1.
Characteristics of included patients (n=180,281)
Table 1.
Characteristic Initial hospitalization
Unweighted No Weighted* percent (%)
Age (yr), mean ± SD 65.4 ± 11.4
Age group
 18–44 9,048 5.2
 45–54 20,136 11.3
 55–64 45,778 25.6
 65–74 66,129 36.5
 75–84 35,273 19.3
 ≥ 85 3,917 2.1
Sex
 Male 87,331 48.3
 Female 92,950 51.7
Insurance type
 Medicare 106,310 58.8
 Medicaid 9,296 5.0
Private insurance 53,284 30.1
 Self-pay 907 0.5
 No charge 144 0.1
 Other† 10,151 5.4
Median household income
 0–25th percentile 37,207 22.1
 26th to 50th percentile 46,884 27.5
 51th to 75th percentile 48,540 26.5
 76th to 100th percentile 45,232 22.6
Patient location
 “Central” counties of metro areas of ≥ 1 million population 40,158 19.4
 “Fringe” counties of metro areas of ≥ 1 million population 48,512 27.0
 Counties in metro areas of 250,000–999,999 population 42,288 23.1
 Counties in metro areas of 50,000–249,999 population 19,446 11.4
 Micropolitan counties 17,409 11.0
 Not metropolitan or micropolitan counties 12,274 8.2
Day of admission
 Weekday 177,337 98.4
 Weekend 2,944 1.6
 Length of stay (day), median (IQR) 3 (2–4)
Discharge status
 Routine 108,338 62.0
 Transfer to short-term hospital 499 0.3
 Transfer to SNF, ICF, other 26,808 14.7
 Home health care 44,458 23.0
 Against medical advice 178 0.1
Admission type
 Nonelective admission 14,711 8.1
 Elective admission 165,354 91.8
Elixhauser Comorbidity Index score
 0 26,478 14.4
 1 41,954 23.1
 2–3 76,197 42.4
 4–5 28,626 16.1
 ≥6 7,026 4.0
Type of surgery
 Decompression alone 40,485 21.2
 Fusion 139,796 78.8
 Depression 29,566 16.9
 Anxiety 29,019 16.5
 Rheumatoid arthritis 191 0.1
 Osteoarthritis 24,899 14.1
 Osteoporosis 8,602 4.8
 Overweight 4,121 2.2
 Obesity 38,491 21.7
 Hypertriglyceridemia 684 0.4
 Hypertension 116,798 65.4
 Alcohol use disorders 2,485 1.4
 Drug use disorders 3,597 1.8
 Smoking‡ 67,321 37.8
 Sleep disorders 35,321 20.0

SD, standard deviation; IQR, interquartile range; SNF, skilled nursing facility; ICF, intermediate care facility.

*Weights provided by the Healthcare Cost and Utilization Project, Nationwide Readmissions Database were used to ensure that the estimates were nationally representative, and weights and design variables were included to obtain unbiased estimates and standard errors.

†“Other” includes Worker’s Compensation, CHAMPUS (Civilian Health and Medical Program of the Uniformed Services), CHAMPVA (Civilian Health and Medical Program of the Department of Veteran’s Affairs), Title V, and other government programs.

‡“Smoking” includes tobacco/nicotine dependence, and secondhand smoke exposure.

Table 2.
Top 10 causes of readmission between 0 and 7 days coded by clinical classifications software refined for the International Classification of Diseases, Tenth Revision, Clinical Modification Diagnoses
Table 2.
Cause Readmission between 0 and 7 days (%)
Total index patients (n = 180,281) 4,388 (2.4)
Surgical site-related 28.9
Other surgical care complication 10.7
Infection 8.3
Disruption of wound 1.1
Vascular complications 0.6
Other complications 0.4
Postoperative nervous system complication 7.9
Postoperative hematoma and seroma of a nervous system structure 4.5
Other complications of nervous system 2.6
Accidental puncture and laceration of a nervous system structure 0.4
Nervous system pain and pain syndromes 6.0
Acute postprocedural pain 5.9
Postoperative musculoskeletal system complication 4.4
Postoperative hematoma and seroma of a musculoskeletal structure 3.5
Other complications of musculoskeletal system 0.4
Nonsurgical site-related 23.3
Septicemia 6.8
Sepsis, unspecified organism 5.5
Sepsis due to other Gram-negative organisms 0.7
Spondylopathies/spondyloarthropathy 5.8
Spinal stenosis 2.6
Radiculopathy 0.9
Spondylolisthesis 0.8
Thoracic, thoracolumbar and lumbosacral intervertebral disc disorders with radiculopathy 0.6
Other nervous system disorders 3.3
Toxic encephalopathy 1.6
Other and unspecified encephalopathy 0.7
Cerebrospinal fluid leak 0.6
Acute pulmonary embolism 2.6
Pulmonary embolism without acute cor pulmonale 2.3
Urinary tract infections 2.5
Urinary tract infection, site not specified 1.9
Acute cystitis 0.4
Intestinal obstruction and ileus 2.3
Ileus, unspecified 1.4
Other and unspecified intestinal obstruction 0.6
Table 3.
Predictive factors of readmissions at different periods* (0–7 days and 8–30 days)
Table 3.
Characteristic Readmission between 0 and 7 days
 Readmission between 8 and 30 days
Rate (%) OR (95% CI) p-value Rate (%) OR (95% CI) p-value
Total 2.4 (2.3–2.5) 3.5 (3.4–3.7)
Age group (yr)
 18–44 1.6 (1.3–1.9) 1 (reference) 2.9 (2.5–3.3) 1 (reference)
 45–54 1.8 (1.6–2.0) 1.06 (0.86–1.32) 0.58 3.1 (2.8–3.5) 0.99 (0.83–1.18) 0.93
 55–64 2.0 (1.9–2.2) 1.15 (0.94–1.41) 0.19 3.2 (3.0–3.4) 0.92 (0.78–1.08) 0.31
 65–74 2.5 (2.4–2.7) 1.20 (0.96–1.50) 0.11 3.5 (3.3–3.7) 0.76 (0.64–0.91) 0.002
 75–84 3.0 (2.8–3.2) 1.33 (1.04–1.69) 0.02 4.2 (3.9–4.4) 0.80 (0.66–0.96) 0.02
 ≥ 85 3.9 (3.2–4.6) 1.59 (1.18–2.15) 0.003 6.3 (5.4–7.2) 1.07 (0.85–1.33) 0.57
Sex
 Male 2.6 (2.4–2.7) 1 (reference) 3.3 (3.1–3.5) 1 (reference)
 Female 2.2 (2.1–2.3) 0.78 (0.72–0.84) < 0.001 3.8 (3.6–4.0) 1.02 (0.96–1.09) 0.50
Insurance type
 Medicare 2.8 (2.7–2.9) 1 (reference) 4.1 (3.9–4.2) 1 (reference)
 Medicaid 2.5 (2.1–2.8) 1.04 (0.86–1.25) 0.69 4.2 (3.7–4.7) 0.96 (0.83–1.12) 0.62
 Private insurance 1.7 (1.5–1.8) 0.77 (0.68–0.87) < 0.001 2.6 (2.4–2.7) 0.72 (0.65–0.80) < 0.001
 Self-pay 2.4 (1.2–3.6) 1.01 (0.62–1.67) 0.96 5.1 (3.5–6.8) 1.33 (0.93–1.91) 0.12
 No charge 2.6 (-0.2–5.4) 0.87 (0.24–3.09) 0.83 6.8 (2.0–11.7) 1.53 (0.67–3.49) 0.31
 Other† 1.9 (1.6–2.2) 0.77 (0.63–0.94) 0.01 2.7 (2.3–3.1) 0.75 (0.64–0.88) 0.001
Median household income
 0–25th percentile 2.5 (2.3–2.7) 1 (reference) 3.8 (3.5–4.0) 1 (reference)
 26th to 50th percentile 2.4 (2.2–2.5) 0.95 (0.85–1.05) 0.33 3.6 (3.4–3.8) 0.99 (0.91–1.08) 0.85
 51th to 75th percentile 2.3 (2.1–2.4) 0.89 (0.80–0.99) 0.04 3.5 (3.3–3.7) 0.97 (0.89–1.06) 0.46
 76th to 100th percentile 2.4 (2.2–2.6) 0.94 (0.83–1.06) 0.29 3.2 (3.0–3.5) 0.88 (0.80–0.97) 0.01
Length of stay (day) NA 1.02 (1.01–1.02) < 0.001 NA 1.03 (1.02–1.03) < 0.001
Discharge status
 Routine 1.9 (1.8–2.0) 1 (reference) 2.6 (2.5–2.7) 1 (reference)
 Transfer to short-term hospital 13.0 (7.5–18.5) 6.30 (3.89–10.21) < 0.001 5.1 (2.8–7.4) 1.48 (0.91–2.40) 0.11
 Transfer to SNF, ICF, other 3.6 (3.3–3.9) 1.48 (1.33–1.64) < 0.001 7.2 (6.8–7.6) 2.12 (1.97–2.29) < 0.001
 Home health care 2.8 (2.6–3.0) 1.32 (1.21–1.45) < 0.001 3.8 (3.5–4.0) 1.24 (1.14–1.35) < 0.001
 Against medical advice 6.9 (2.4–11.5) 2.84 (1.36–5.96) 0.006 5.2 (1.5–8.9) 1.53 (0.72–3.28) 0.27
 Admission type
 Nonelective admission 3.3 (2.9–3.7) 1 (reference) 6.0 (5.4–6.6) 1 (reference)
 Elective admission 2.3 (2.2–2.4) 0.86 (0.75–0.98) 0.03 3.3 (3.2–3.5) 0.74 (0.67–0.83) < 0.001
Elixhauser Comorbidity Index score
 0 1.6 (1.4–1.8) 1 (reference) 2.0 (1.8–2.3) 1 (reference)
 1 1.8 (1.7–2.0) 1.07 (0.92–1.25) 0.35 2.5 (2.3–2.7) 1.18 (1.03–1.34) 0.02
 2–3 2.4 (2.3–2.6) 1.38 (1.17–1.62) < 0.001 3.5 (3.4–3.7) 1.54 (1.34–1.76) < 0.001
 4–5 3.2 (3.0–3.4) 1.65 (1.37–1.98) < 0.001 5.4 (5.1–5.7) 2.07 (1.75–2.44) < 0.001
 ≥6 4.7 (4.1–5.3) 2.12 (1.67–2.69) < 0.001 8.0 (7.2–8.7) 2.49 (2.04–3.04) < 0.001
Type of surgery
 Decompression alone 2.7 (2.5–2.8) 1 (reference) 3.8 (3.5–4.0) 1 (reference)
 Fusion 2.3 (2.2–2.4) 0.99 (0.90–1.08) 0.81 3.5 (3.3–3.6) 1.00 (0.93–1.08) 0.96
 Anxiety
  No 2.3 (2.2–2.4) 1 (reference) 3.4 (3.3–3.6) 1 (reference)
  Yes 2.7 (2.5–2.9) 1.11 (1.01–1.23) 0.03 4.1 (3.8–4.4) 1.04 (0.96–1.13) 0.35
 Osteoarthritis
  No 2.4 (2.3–2.5) 1 (reference) 3.5 (3.3–3.6) 1 (reference)
  Yes 2.6 (2.3–2.8) 0.97 (0.88–1.08) 0.62 3.9 (3.6–4.2) 0.98 (0.91–1.07) 0.71
 Osteoporosis
  No 2.4 (2.3–2.5) 1 (reference) 3.5 (3.4–3.7) 1 (reference)
  Yes 2.5 (2.1–2.9) 0.93 (0.79–1.10) 0.40 4.1 (3.6–4.6) 0.96 (0.85–1.09) 0.52
 Obesity
  No 2.3 (2.2–2.4) 1 (reference) 3.3 (3.2–3.4) 1 (reference)
  Yes 2.7 (2.5–2.9) 1.00 (0.91–1.10) 0.99 4.4 (4.2–4.7) 1.04 (0.96–1.12) 0.37
 Alcohol use disorders
  No 2.4 (2.3–2.5) 1 (reference) 3.5 (3.4–3.7) 1 (reference)
  Yes 2.8 (2.1–3.5) 0.85 (0.64–1.13) 0.26 5.3 (4.4–6.3) 1.10 (0.89–1.35) 0.39

OR, odds ratio; CI, confidence interval; NA, not available; SNF, skilled nursing facility; ICF, intermediate care facility.

*This table includes only predictors with statistically significant estimates for at least one of the 4 periods.

†“Other” includes Worker’s Compensation, CHAMPUS (Civilian Health and Medical Program of the Uniformed Services), CHAMPVA (Civilian Health and Medical Program of the Department of Veteran’s Affairs), Title V, and other government programs.

Table 4.
Top 10 causes of readmission between 8 and 30 days coded by clinical classifications software refined for the International Classification of Diseases, Tenth Revision, Clinical Modification Diagnoses
Table 4.
Cause Readmission between 8 and 30 days (%)
Total index patients (n = 180,281) 6,385 (3.5)
Surgical site-related 41.4
 Other surgical care complication 29.2
  Infection 22.3
  Disruption of wound 5.4
  Vascular complications 0.6
  Other complications 0.4
 Internal orthopedic device or implant complication 4.5
  Displacement of internal fixation device of vertebrae 1.6
  Infection due to internal fixation device of spine 1.0
  Pain due to internal orthopedic prosthetic devices, implants and grafts 0.3
  Infection due to other internal orthopedic prosthetic devices, implants and grafts 0.2
  Mechanical loosening of other internal prosthetic joint 0.2
 Postoperative nervous system complication 4.2
  Other complications of nervous system 2.5
  Postoperative hematoma and seroma of a nervous system structure 1.5
  Accidental puncture and laceration of a nervous system structure 0.2
 Postoperative musculoskeletal system complication 3.4
  Postoperative hematoma and seroma of a musculoskeletal structure 2.6
  Other complications of musculoskeletal system 0.2
  Postlaminectomy syndrome 0.2
  Pseudarthrosis after fusion or arthrodesis 0.2
Nonsurgical site-related 22.7
 Spondylopathies/spondyloarthropathy 7.7
  Spinal stenosis 3.7
  Radiculopathy 1.0
  Thoracic, thoracolumbar and lumbosacral intervertebral disc disorders with radiculopathy 0.9
  Spondylolisthesis 0.6
  Spondylosis 0.5
  Other thoracic, thoracolumbar and lumbosacral intervertebral disc displacement 0.4
 Septicemia 6.2
  Sepsis, unspecified organism 4.3
  Sepsis due to other Gram-negative organisms 1.2
  Other specified sepsis 0.3
 Acute pulmonary embolism 3.4
  Pulmonary embolism without acute cor pulmonale 3.1
  Pulmonary embolism with acute cor pulmonale 0.3
 Acute and unspecified renal failure 1.9
  Acute kidney failure, unspecified 1.7
  Acute kidney failure with tubular necrosis 0.2
 Urinary tract infections 1.9
  Urinary tract infection, site not specified 1.4
  Acute cystitis 0.2
 Other nervous system disorders 1.7
  Toxic encephalopathy 0.6
  Cerebrospinal fluid leak 0.4
  Other and unspecified encephalopathy 0.3
Table 5.
Top 10 causes of readmission between 31 and 90 days coded by clinical classifications software refined for the International Classification of Diseases, Tenth Revision, Clinical Modification Diagnoses
Table 5.
Cause Readmission between 31 and 90 days (%)
Total index patients (n = 144,667) 5,992 (4.1)
Surgical site-related 21.4
Other surgical care complication 11.4
 Infection 8.2
 Disruption of wound 2.4
 Other complications 0.4
Internal orthopedic device or implant complication 6.3
 Displacement of internal fixation device of vertebrae 2.1
 Infection due to internal fixation device of spine 0.6
 Breakdown of internal fixation device of vertebrae 0.5
 Mechanical loosening of other internal prosthetic joint 0.3
 Other mechanical complication of internal fixation device of vertebrae 0.3
 Displacement of other internal orthopedic devices, implants and grafts 0.3
 Infection due to other internal orthopedic prosthetic devices, implants and grafts 0.2
Postoperative musculoskeletal system complication 2.0
 Postoperative hematoma and seroma of a musculoskeletal structure 0.8
 Pseudarthrosis after fusion or arthrodesis 0.7
 Postlaminectomy syndrome 0.3
 Fracture of other bone following insertion of orthopedic implant, joint prosthesis, or bone plate 0.2
Postoperative nervous system complication 1.8
 Other complications of nervous system 1.2
 Postoperative hematoma and seroma of a nervous system structure 0.3
Nonsurgical site-related 29.3
 Spondylopathies/spondyloarthropathy 12.6
  Spinal stenosis 6.0
  Thoracic, thoracolumbar and lumbosacral intervertebral disc disorders with radiculopathy 1.3
  Spondylosis 1.2
  Radiculopathy 1.2
  Spondylolisthesis 0.9
  Other thoracic, thoracolumbar and lumbosacral intervertebral disc displacement 0.3
  Discitis 0.2
  Other thoracic, thoracolumbar and lumbosacral intervertebral disc degeneration 0.3
Osteoarthritis 6.0
 Unilateral primary osteoarthritis of hip 3.1
 Unilateral primary osteoarthritis of knee 2.0
 Primary osteoarthritis of other joints 0.5
Septicemia 5.3
 Sepsis, unspecified organism 3.5
 Sepsis due to other Gram-negative organisms 0.9
 Other specified sepsis 0.3
 Sepsis due to Staphylococcus aureus 0.3
Heart failure 1.9
 Hypertensive heart disease with heart failure 1.0
 Hypertensive heart and chronic kidney disease with heart failure 0.8
Pneumonia 1.9
 Pneumonia, unspecified organism 1.2
 Lobar pneumonia, unspecified organism 0.3
Urinary tract infections 1.7
 Urinary tract infection, site not specified 1.0
 Acute cystitis 0.2
Table 6.
Predictive factors of readmissions at different periods* (31–90 days and 91–180 days)
Table 6.
Characteristic Readmission between 31 and 90 days
 Readmission between 91 and 180 days
Rate (%) OR (95% CI) p-value Rate (%) OR (95% CI) p-value
Total 3.7 (3.6–3.8) 4.3 (4.2–4.5)
Age group (yr)
 18–44 2.5 (2.1–3.0) 1 (reference) 2.7 (2.2–3.2) 1 (reference)
 45–54 2.8 (2.5–3.0) 1.02 (0.84–1.24) 0.84 3.6 (3.2–4.0) 1.27 (1.02–1.58) 0.04
 55–64 3.4 (3.2–3.6) 1.19 (0.99–1.43) 0.07 4.1 (3.8–4.4) 1.34 (1.09–1.65) 0.005
 65–74 3.8 (3.6–4.0) 1.11 (0.91–1.35) 0.31 4.5 (4.2–4.7) 1.22 (0.98–1.52) 0.08
 75–84 4.6 (4.3–4.8) 1.16 (0.94–1.43) 0.17 5.0 (4.7–5.4) 1.26 (1.00–1.59) < 0.05
 ≥ 85 6.4 (5.4–7.3) 1.42 (1.09–1.84) 0.009 6.6 (5.4–7.9) 1.50 (1.11–2.03) 0.008
Sex
 Male 3.7 (3.6–3.9) 1 (reference) 4.4 (4.2–4.7) 1 (reference)
 Female 3.7 (3.5–3.9) 0.90 (0.84–0.96) 0.002 4.2 (4.0–4.4) 0.91 (0.84–0.98) 0.02
Insurance type
 Medicare 4.3 (4.1–4.4) 1 (reference) 4.9 (4.7–5.1) 1 (reference)
 Medicaid 4.5 (3.9–5.0) 1.16 (0.98–1.37) 0.08 4.9 (4.2–5.6) 1.08 (0.90–1.30) 0.41
 Private insurance 2.7 (2.5–2.9) 0.79 (0.71–0.89) < 0.001 3.4 (3.1–3.6) 0.78 (0.70–0.87) < 0.001
 Self-pay 4.5 (2.6–6.3) 1.23 (0.80–1.90) 0.34 4.5 (2.0–7.0) 0.98 (0.55–1.74) 0.95
 No charge 2.3 (-0.6–5.2) 0.58 (0.16–2.10) 0.41 9.7 (4.1–15.2) 2.24 (1.17–4.25) 0.01
 Other† 2.8 (2.4–3.2) 0.79 (0.66–0.94) 0.007 3.0 (2.5–3.5) 0.67 (0.55–0.82) < 0.001
Median household income
 0–25th percentile 4.0 (3.7–4.2) 1 (reference) 4.6 (4.3–4.9) 1 (reference)
 26–50th percentile 3.9 (3.7–4.1) 0.99 (0.90–1.09) 0.85 4.4 (4.1–4.6) 0.97 (0.87–1.08) 0.57
 51–75th percentile 3.7 (3.5–3.9) 0.91 (0.83–1.01) 0.06 4.3 (3.9–4.6) 0.95 (0.85–1.06) 0.35
 76–100th percentile 3.3 (3.1–3.6) 0.81 (0.73–0.90) < 0.001 4.1 (3.8–4.4) 0.91 (0.81–1.03) 0.13
Length of stay (day) NA 1.02 (1.02–1.03) < 0.001 NA 1.01 (1.00–1.02) 0.02
 Discharge status
 Routine 2.9 (2.7–3.0) 1 (reference) 3.8 (3.6–4.0) 1 (reference)
 Transfer to short-term hospital 5.0 (2.6–7.4) 1.37 (0.82–2.29) 0.23 3.6 (0.8–6.4) 0.78 (0.35–1.76) 0.56
 Transfer to SNF, ICF, other 6.7 (6.3–7.1) 1.76 (1.61–1.92) < 0.001 6.2 (5.8–6.7) 1.34 (1.20–1.48) < 0.001
 Home health care 4.0 (3.8–4.3) 1.18 (1.09–1.29) < 0.001 4.5 (4.2–4.9) 1.07 (0.98–1.18) 0.13
 Against medical advice 6.4 (2.2–10.6) 1.65 (0.80–3.40) 0.17 7.4 (1.6–13.1) 1.62 (0.68–3.84) 0.27
Admission type
 Nonelective admission 5.9 (5.4–6.5) 1 (reference) 5.4 (4.7–6.0) 1 (reference)
 Elective admission 3.5 (3.4–3.6) 0.79 (0.70–0.89) < 0.001 4.2 (4.1–4.4) 0.95 (0.82–1.09) 0.43
Elixhauser Comorbidity Index score
 0 2.3 (2.1–2.5) 1 (reference) 2.8 (2.5–3.2) 1 (reference)
 1 2.7 (2.5–2.9) 1.12 (0.98–1.29) 0.10 3.5 (3.2–3.8) 1.20 (1.02–1.39) 0.02
 2–3 3.8 (3.6–4.0) 1.50 (1.29–1.74) < 0.001 4.4 (4.1–4.6) 1.46 (1.24–1.71) < 0.001
 4–5 5.4 (5.1–5.8) 1.91 (1.61–2.26) < 0.001 6.0 (5.6–6.5) 1.96 (1.62–2.36) < 0.001
 ≥6 7.3 (6.5–8.0) 2.15 (1.74–2.66) < 0.001 7.4 (6.4–8.4) 2.23 (1.75–2.84) < 0.001
Type of surgery
 Decompression alone 4.6 (4.3–4.9) 1 (reference) 5.4 (5.0–5.7) 1 (reference)
 Fusion 3.5 (3.3–3.6) 0.81 (0.75–0.88) < 0.001 4.0 (3.9–4.2) 0.79 (0.72–0.86) < 0.001
 Anxiety
  No 3.6 (3.5–3.7) 1 (reference) 4.2 (4.0–4.4) 1 (reference)
  Yes 4.3 (4.0–4.7) 1.10 (1.00–1.21) 0.04 5.0 (4.6–5.4) 1.12 (1.01–1.24) 0.03
 Osteoarthritis
  No 3.7 (3.5–3.8) 1 (reference) 4.2 (4.0–4.4) 1 (reference)
  Yes 4.0 (3.6–4.3) 0.94 (0.86–1.03) 0.19 5.2 (4.8–5.6) 1.14 (1.04–1.25) 0.007
 Osteoporosis
  No 3.7 (3.5–3.8) 1 (reference) 4.3 (4.2–4.5) 1 (reference)
  Yes 4.9 (4.3–5.5) 1.16 (1.01–1.34) 0.04 4.5 (3.8–5.2) 0.92 (0.77–1.09) 0.33
 Obesity
  No 3.6 (3.5–3.7) 1 (reference) 4.2 (4.1–4.4) 1 (reference)
  Yes 4.2 (3.9–4.4) 0.94 (0.86–1.02) 0.12 4.6 (4.3–5.0) 0.88 (0.80–0.98) 0.02
 Alcohol use disorders
  No 3.7 (3.6–3.8) 1 (reference) 4.3 (4.1–4.5) 1 (reference)
  Yes 5.2 (4.1–6.3) 1.01 (0.80–1.28) 0.92 7.3 (5.7–9.0) 1.32 (1.03–1.70) 0.03

OR, odds ratio; CI, confidence interval; NA, not available; SNF, skilled nursing facility; ICF, intermediate care facility.

*This table includes only predictors with statistically significant estimates for at least one of the 4 periods.

†“Other” includes Worker’s Compensation, CHAMPUS (Civilian Health and Medical Program of the Uniformed Services), CHAMPVA (Civilian Health and Medical Program of the Department of Veteran’s Affairs), Title V, and other government programs.

Table 7.
Top 10 causes of readmission between 91 and 180 days coded by clinical classifications software refined for the International Classification of Diseases, Tenth Revision, Clinical Modification Diagnoses
Table 7.
Cause Readmission between 91 and 180 days (%)
Total index patients (n = 96,562) 5,191 (5.4)
Surgical site-related 9.7
 Internal orthopedic device or implant complication 5.4
  Displacement of internal fixation device of vertebrae 1.5
  Breakdown of internal fixation device of vertebrae 0.4
  Infection due to internal fixation device of spine 0.3
  Mechanical loosening of other internal prosthetic joint 0.2
  Other specified complication 0.3
  Pain due to internal orthopedic prosthetic devices, implants and grafts 0.2
 Postoperative musculoskeletal system complication 2.5
  Pseudarthrosis after fusion or arthrodesis 1.8
  Postlaminectomy syndrome 0.4
  Postoperative hematoma and seroma of a musculoskeletal structure 0.2
 Other surgical care complication 1.7
  Infection 1.0
Nonsurgical site-related 46.0
 Spondylopathies/spondyloarthropathy 17.5
  Spinal stenosis 8.7
  Spondylosis 1.9
  Thoracic, thoracolumbar and lumbosacral intervertebral disc disorders with radiculopathy 1.3
  Radiculopathy 0.9
  Other thoracic, thoracolumbar and lumbosacral intervertebral disc displacement 0.7
  Cervical disc disorder with radiculopathy 0.5
  Cervical disc disorder with myelopathy 0.5
  Other thoracic, thoracolumbar and lumbosacral intervertebral disc degeneration 0.4
 Osteoarthritis 16.7
  Unilateral primary osteoarthritis of hip 9.2
  Unilateral primary osteoarthritis of knee 4.9
  Primary osteoarthritis of other joints 1.6
  Bilateral primary osteoarthritis of knee 0.6
  Bilateral primary osteoarthritis of hip 0.4
 Septicemia 4.7
  Sepsis, unspecified organism 3.1
  Sepsis due to other Gram-negative organisms 0.9
  Sepsis due to Staphylococcus aureus 0.3
 Heart failure 2.1
  Hypertensive heart disease with heart failure 1.1
  Hypertensive heart and chronic kidney disease with heart failure 0.8
 Cardiac dysrhythmias 1.8
  Unspecified atrial fibrillation and atrial flutter 0.6
  Paroxysmal atrial fibrillation 0.5
  Persistent atrial fibrillation 0.3
 Coronary atherosclerosis and other heart disease 1.7
  Atherosclerotic heart disease of native coronary artery 1.5
 Pneumonia 1.5
  Pneumonia, unspecified organism 1.0
  Lobar pneumonia, unspecified organism 0.3
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Rates, Causes, and Predictive Factors of Hospital Readmissions After Spine Surgery for Lumbar Spinal Stenosis: A Nationwide Retrospective Cohort Study
Neurospine. 2025;22(2):523-539.   Published online June 30, 2025
DOI: https://doi.org/10.14245/ns.2449316.658
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Rates, Causes, and Predictive Factors of Hospital Readmissions After Spine Surgery for Lumbar Spinal Stenosis: A Nationwide Retrospective Cohort Study
Neurospine. 2025;22(2):523-539.   Published online June 30, 2025
DOI: https://doi.org/10.14245/ns.2449316.658
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Rates, Causes, and Predictive Factors of Hospital Readmissions After Spine Surgery for Lumbar Spinal Stenosis: A Nationwide Retrospective Cohort Study
Image
Fig. 1. Flowchart of patient inclusion and exclusion. *Patient Linkage Number is a data element used to associate all hospitalizations associated with a unique patient to identify discharges belonging to the same patient. To identify index events (the starting point for analyzing repeat hospitalizations), we excluded subsequent hospitalizations. LSS, lumbar spinal stenosis.

Fig. 1.

Rates, Causes, and Predictive Factors of Hospital Readmissions After Spine Surgery for Lumbar Spinal Stenosis: A Nationwide Retrospective Cohort Study
Characteristic Initial hospitalization
Unweighted No Weighted* percent (%)
Age (yr), mean ± SD 65.4 ± 11.4
Age group
 18–44 9,048 5.2
 45–54 20,136 11.3
 55–64 45,778 25.6
 65–74 66,129 36.5
 75–84 35,273 19.3
 ≥ 85 3,917 2.1
Sex
 Male 87,331 48.3
 Female 92,950 51.7
Insurance type
 Medicare 106,310 58.8
 Medicaid 9,296 5.0
Private insurance 53,284 30.1
 Self-pay 907 0.5
 No charge 144 0.1
 Other† 10,151 5.4
Median household income
 0–25th percentile 37,207 22.1
 26th to 50th percentile 46,884 27.5
 51th to 75th percentile 48,540 26.5
 76th to 100th percentile 45,232 22.6
Patient location
 “Central” counties of metro areas of ≥ 1 million population 40,158 19.4
 “Fringe” counties of metro areas of ≥ 1 million population 48,512 27.0
 Counties in metro areas of 250,000–999,999 population 42,288 23.1
 Counties in metro areas of 50,000–249,999 population 19,446 11.4
 Micropolitan counties 17,409 11.0
 Not metropolitan or micropolitan counties 12,274 8.2
Day of admission
 Weekday 177,337 98.4
 Weekend 2,944 1.6
 Length of stay (day), median (IQR) 3 (2–4)
Discharge status
 Routine 108,338 62.0
 Transfer to short-term hospital 499 0.3
 Transfer to SNF, ICF, other 26,808 14.7
 Home health care 44,458 23.0
 Against medical advice 178 0.1
Admission type
 Nonelective admission 14,711 8.1
 Elective admission 165,354 91.8
Elixhauser Comorbidity Index score
 0 26,478 14.4
 1 41,954 23.1
 2–3 76,197 42.4
 4–5 28,626 16.1
 ≥6 7,026 4.0
Type of surgery
 Decompression alone 40,485 21.2
 Fusion 139,796 78.8
 Depression 29,566 16.9
 Anxiety 29,019 16.5
 Rheumatoid arthritis 191 0.1
 Osteoarthritis 24,899 14.1
 Osteoporosis 8,602 4.8
 Overweight 4,121 2.2
 Obesity 38,491 21.7
 Hypertriglyceridemia 684 0.4
 Hypertension 116,798 65.4
 Alcohol use disorders 2,485 1.4
 Drug use disorders 3,597 1.8
 Smoking‡ 67,321 37.8
 Sleep disorders 35,321 20.0
Cause Readmission between 0 and 7 days (%)
Total index patients (n = 180,281) 4,388 (2.4)
Surgical site-related 28.9
Other surgical care complication 10.7
Infection 8.3
Disruption of wound 1.1
Vascular complications 0.6
Other complications 0.4
Postoperative nervous system complication 7.9
Postoperative hematoma and seroma of a nervous system structure 4.5
Other complications of nervous system 2.6
Accidental puncture and laceration of a nervous system structure 0.4
Nervous system pain and pain syndromes 6.0
Acute postprocedural pain 5.9
Postoperative musculoskeletal system complication 4.4
Postoperative hematoma and seroma of a musculoskeletal structure 3.5
Other complications of musculoskeletal system 0.4
Nonsurgical site-related 23.3
Septicemia 6.8
Sepsis, unspecified organism 5.5
Sepsis due to other Gram-negative organisms 0.7
Spondylopathies/spondyloarthropathy 5.8
Spinal stenosis 2.6
Radiculopathy 0.9
Spondylolisthesis 0.8
Thoracic, thoracolumbar and lumbosacral intervertebral disc disorders with radiculopathy 0.6
Other nervous system disorders 3.3
Toxic encephalopathy 1.6
Other and unspecified encephalopathy 0.7
Cerebrospinal fluid leak 0.6
Acute pulmonary embolism 2.6
Pulmonary embolism without acute cor pulmonale 2.3
Urinary tract infections 2.5
Urinary tract infection, site not specified 1.9
Acute cystitis 0.4
Intestinal obstruction and ileus 2.3
Ileus, unspecified 1.4
Other and unspecified intestinal obstruction 0.6
Characteristic Readmission between 0 and 7 days
 Readmission between 8 and 30 days
Rate (%) OR (95% CI) p-value Rate (%) OR (95% CI) p-value
Total 2.4 (2.3–2.5) 3.5 (3.4–3.7)
Age group (yr)
 18–44 1.6 (1.3–1.9) 1 (reference) 2.9 (2.5–3.3) 1 (reference)
 45–54 1.8 (1.6–2.0) 1.06 (0.86–1.32) 0.58 3.1 (2.8–3.5) 0.99 (0.83–1.18) 0.93
 55–64 2.0 (1.9–2.2) 1.15 (0.94–1.41) 0.19 3.2 (3.0–3.4) 0.92 (0.78–1.08) 0.31
 65–74 2.5 (2.4–2.7) 1.20 (0.96–1.50) 0.11 3.5 (3.3–3.7) 0.76 (0.64–0.91) 0.002
 75–84 3.0 (2.8–3.2) 1.33 (1.04–1.69) 0.02 4.2 (3.9–4.4) 0.80 (0.66–0.96) 0.02
 ≥ 85 3.9 (3.2–4.6) 1.59 (1.18–2.15) 0.003 6.3 (5.4–7.2) 1.07 (0.85–1.33) 0.57
Sex
 Male 2.6 (2.4–2.7) 1 (reference) 3.3 (3.1–3.5) 1 (reference)
 Female 2.2 (2.1–2.3) 0.78 (0.72–0.84) < 0.001 3.8 (3.6–4.0) 1.02 (0.96–1.09) 0.50
Insurance type
 Medicare 2.8 (2.7–2.9) 1 (reference) 4.1 (3.9–4.2) 1 (reference)
 Medicaid 2.5 (2.1–2.8) 1.04 (0.86–1.25) 0.69 4.2 (3.7–4.7) 0.96 (0.83–1.12) 0.62
 Private insurance 1.7 (1.5–1.8) 0.77 (0.68–0.87) < 0.001 2.6 (2.4–2.7) 0.72 (0.65–0.80) < 0.001
 Self-pay 2.4 (1.2–3.6) 1.01 (0.62–1.67) 0.96 5.1 (3.5–6.8) 1.33 (0.93–1.91) 0.12
 No charge 2.6 (-0.2–5.4) 0.87 (0.24–3.09) 0.83 6.8 (2.0–11.7) 1.53 (0.67–3.49) 0.31
 Other† 1.9 (1.6–2.2) 0.77 (0.63–0.94) 0.01 2.7 (2.3–3.1) 0.75 (0.64–0.88) 0.001
Median household income
 0–25th percentile 2.5 (2.3–2.7) 1 (reference) 3.8 (3.5–4.0) 1 (reference)
 26th to 50th percentile 2.4 (2.2–2.5) 0.95 (0.85–1.05) 0.33 3.6 (3.4–3.8) 0.99 (0.91–1.08) 0.85
 51th to 75th percentile 2.3 (2.1–2.4) 0.89 (0.80–0.99) 0.04 3.5 (3.3–3.7) 0.97 (0.89–1.06) 0.46
 76th to 100th percentile 2.4 (2.2–2.6) 0.94 (0.83–1.06) 0.29 3.2 (3.0–3.5) 0.88 (0.80–0.97) 0.01
Length of stay (day) NA 1.02 (1.01–1.02) < 0.001 NA 1.03 (1.02–1.03) < 0.001
Discharge status
 Routine 1.9 (1.8–2.0) 1 (reference) 2.6 (2.5–2.7) 1 (reference)
 Transfer to short-term hospital 13.0 (7.5–18.5) 6.30 (3.89–10.21) < 0.001 5.1 (2.8–7.4) 1.48 (0.91–2.40) 0.11
 Transfer to SNF, ICF, other 3.6 (3.3–3.9) 1.48 (1.33–1.64) < 0.001 7.2 (6.8–7.6) 2.12 (1.97–2.29) < 0.001
 Home health care 2.8 (2.6–3.0) 1.32 (1.21–1.45) < 0.001 3.8 (3.5–4.0) 1.24 (1.14–1.35) < 0.001
 Against medical advice 6.9 (2.4–11.5) 2.84 (1.36–5.96) 0.006 5.2 (1.5–8.9) 1.53 (0.72–3.28) 0.27
 Admission type
 Nonelective admission 3.3 (2.9–3.7) 1 (reference) 6.0 (5.4–6.6) 1 (reference)
 Elective admission 2.3 (2.2–2.4) 0.86 (0.75–0.98) 0.03 3.3 (3.2–3.5) 0.74 (0.67–0.83) < 0.001
Elixhauser Comorbidity Index score
 0 1.6 (1.4–1.8) 1 (reference) 2.0 (1.8–2.3) 1 (reference)
 1 1.8 (1.7–2.0) 1.07 (0.92–1.25) 0.35 2.5 (2.3–2.7) 1.18 (1.03–1.34) 0.02
 2–3 2.4 (2.3–2.6) 1.38 (1.17–1.62) < 0.001 3.5 (3.4–3.7) 1.54 (1.34–1.76) < 0.001
 4–5 3.2 (3.0–3.4) 1.65 (1.37–1.98) < 0.001 5.4 (5.1–5.7) 2.07 (1.75–2.44) < 0.001
 ≥6 4.7 (4.1–5.3) 2.12 (1.67–2.69) < 0.001 8.0 (7.2–8.7) 2.49 (2.04–3.04) < 0.001
Type of surgery
 Decompression alone 2.7 (2.5–2.8) 1 (reference) 3.8 (3.5–4.0) 1 (reference)
 Fusion 2.3 (2.2–2.4) 0.99 (0.90–1.08) 0.81 3.5 (3.3–3.6) 1.00 (0.93–1.08) 0.96
 Anxiety
  No 2.3 (2.2–2.4) 1 (reference) 3.4 (3.3–3.6) 1 (reference)
  Yes 2.7 (2.5–2.9) 1.11 (1.01–1.23) 0.03 4.1 (3.8–4.4) 1.04 (0.96–1.13) 0.35
 Osteoarthritis
  No 2.4 (2.3–2.5) 1 (reference) 3.5 (3.3–3.6) 1 (reference)
  Yes 2.6 (2.3–2.8) 0.97 (0.88–1.08) 0.62 3.9 (3.6–4.2) 0.98 (0.91–1.07) 0.71
 Osteoporosis
  No 2.4 (2.3–2.5) 1 (reference) 3.5 (3.4–3.7) 1 (reference)
  Yes 2.5 (2.1–2.9) 0.93 (0.79–1.10) 0.40 4.1 (3.6–4.6) 0.96 (0.85–1.09) 0.52
 Obesity
  No 2.3 (2.2–2.4) 1 (reference) 3.3 (3.2–3.4) 1 (reference)
  Yes 2.7 (2.5–2.9) 1.00 (0.91–1.10) 0.99 4.4 (4.2–4.7) 1.04 (0.96–1.12) 0.37
 Alcohol use disorders
  No 2.4 (2.3–2.5) 1 (reference) 3.5 (3.4–3.7) 1 (reference)
  Yes 2.8 (2.1–3.5) 0.85 (0.64–1.13) 0.26 5.3 (4.4–6.3) 1.10 (0.89–1.35) 0.39
Cause Readmission between 8 and 30 days (%)
Total index patients (n = 180,281) 6,385 (3.5)
Surgical site-related 41.4
 Other surgical care complication 29.2
  Infection 22.3
  Disruption of wound 5.4
  Vascular complications 0.6
  Other complications 0.4
 Internal orthopedic device or implant complication 4.5
  Displacement of internal fixation device of vertebrae 1.6
  Infection due to internal fixation device of spine 1.0
  Pain due to internal orthopedic prosthetic devices, implants and grafts 0.3
  Infection due to other internal orthopedic prosthetic devices, implants and grafts 0.2
  Mechanical loosening of other internal prosthetic joint 0.2
 Postoperative nervous system complication 4.2
  Other complications of nervous system 2.5
  Postoperative hematoma and seroma of a nervous system structure 1.5
  Accidental puncture and laceration of a nervous system structure 0.2
 Postoperative musculoskeletal system complication 3.4
  Postoperative hematoma and seroma of a musculoskeletal structure 2.6
  Other complications of musculoskeletal system 0.2
  Postlaminectomy syndrome 0.2
  Pseudarthrosis after fusion or arthrodesis 0.2
Nonsurgical site-related 22.7
 Spondylopathies/spondyloarthropathy 7.7
  Spinal stenosis 3.7
  Radiculopathy 1.0
  Thoracic, thoracolumbar and lumbosacral intervertebral disc disorders with radiculopathy 0.9
  Spondylolisthesis 0.6
  Spondylosis 0.5
  Other thoracic, thoracolumbar and lumbosacral intervertebral disc displacement 0.4
 Septicemia 6.2
  Sepsis, unspecified organism 4.3
  Sepsis due to other Gram-negative organisms 1.2
  Other specified sepsis 0.3
 Acute pulmonary embolism 3.4
  Pulmonary embolism without acute cor pulmonale 3.1
  Pulmonary embolism with acute cor pulmonale 0.3
 Acute and unspecified renal failure 1.9
  Acute kidney failure, unspecified 1.7
  Acute kidney failure with tubular necrosis 0.2
 Urinary tract infections 1.9
  Urinary tract infection, site not specified 1.4
  Acute cystitis 0.2
 Other nervous system disorders 1.7
  Toxic encephalopathy 0.6
  Cerebrospinal fluid leak 0.4
  Other and unspecified encephalopathy 0.3
Cause Readmission between 31 and 90 days (%)
Total index patients (n = 144,667) 5,992 (4.1)
Surgical site-related 21.4
Other surgical care complication 11.4
 Infection 8.2
 Disruption of wound 2.4
 Other complications 0.4
Internal orthopedic device or implant complication 6.3
 Displacement of internal fixation device of vertebrae 2.1
 Infection due to internal fixation device of spine 0.6
 Breakdown of internal fixation device of vertebrae 0.5
 Mechanical loosening of other internal prosthetic joint 0.3
 Other mechanical complication of internal fixation device of vertebrae 0.3
 Displacement of other internal orthopedic devices, implants and grafts 0.3
 Infection due to other internal orthopedic prosthetic devices, implants and grafts 0.2
Postoperative musculoskeletal system complication 2.0
 Postoperative hematoma and seroma of a musculoskeletal structure 0.8
 Pseudarthrosis after fusion or arthrodesis 0.7
 Postlaminectomy syndrome 0.3
 Fracture of other bone following insertion of orthopedic implant, joint prosthesis, or bone plate 0.2
Postoperative nervous system complication 1.8
 Other complications of nervous system 1.2
 Postoperative hematoma and seroma of a nervous system structure 0.3
Nonsurgical site-related 29.3
 Spondylopathies/spondyloarthropathy 12.6
  Spinal stenosis 6.0
  Thoracic, thoracolumbar and lumbosacral intervertebral disc disorders with radiculopathy 1.3
  Spondylosis 1.2
  Radiculopathy 1.2
  Spondylolisthesis 0.9
  Other thoracic, thoracolumbar and lumbosacral intervertebral disc displacement 0.3
  Discitis 0.2
  Other thoracic, thoracolumbar and lumbosacral intervertebral disc degeneration 0.3
Osteoarthritis 6.0
 Unilateral primary osteoarthritis of hip 3.1
 Unilateral primary osteoarthritis of knee 2.0
 Primary osteoarthritis of other joints 0.5
Septicemia 5.3
 Sepsis, unspecified organism 3.5
 Sepsis due to other Gram-negative organisms 0.9
 Other specified sepsis 0.3
 Sepsis due to Staphylococcus aureus 0.3
Heart failure 1.9
 Hypertensive heart disease with heart failure 1.0
 Hypertensive heart and chronic kidney disease with heart failure 0.8
Pneumonia 1.9
 Pneumonia, unspecified organism 1.2
 Lobar pneumonia, unspecified organism 0.3
Urinary tract infections 1.7
 Urinary tract infection, site not specified 1.0
 Acute cystitis 0.2
Characteristic Readmission between 31 and 90 days
 Readmission between 91 and 180 days
Rate (%) OR (95% CI) p-value Rate (%) OR (95% CI) p-value
Total 3.7 (3.6–3.8) 4.3 (4.2–4.5)
Age group (yr)
 18–44 2.5 (2.1–3.0) 1 (reference) 2.7 (2.2–3.2) 1 (reference)
 45–54 2.8 (2.5–3.0) 1.02 (0.84–1.24) 0.84 3.6 (3.2–4.0) 1.27 (1.02–1.58) 0.04
 55–64 3.4 (3.2–3.6) 1.19 (0.99–1.43) 0.07 4.1 (3.8–4.4) 1.34 (1.09–1.65) 0.005
 65–74 3.8 (3.6–4.0) 1.11 (0.91–1.35) 0.31 4.5 (4.2–4.7) 1.22 (0.98–1.52) 0.08
 75–84 4.6 (4.3–4.8) 1.16 (0.94–1.43) 0.17 5.0 (4.7–5.4) 1.26 (1.00–1.59) < 0.05
 ≥ 85 6.4 (5.4–7.3) 1.42 (1.09–1.84) 0.009 6.6 (5.4–7.9) 1.50 (1.11–2.03) 0.008
Sex
 Male 3.7 (3.6–3.9) 1 (reference) 4.4 (4.2–4.7) 1 (reference)
 Female 3.7 (3.5–3.9) 0.90 (0.84–0.96) 0.002 4.2 (4.0–4.4) 0.91 (0.84–0.98) 0.02
Insurance type
 Medicare 4.3 (4.1–4.4) 1 (reference) 4.9 (4.7–5.1) 1 (reference)
 Medicaid 4.5 (3.9–5.0) 1.16 (0.98–1.37) 0.08 4.9 (4.2–5.6) 1.08 (0.90–1.30) 0.41
 Private insurance 2.7 (2.5–2.9) 0.79 (0.71–0.89) < 0.001 3.4 (3.1–3.6) 0.78 (0.70–0.87) < 0.001
 Self-pay 4.5 (2.6–6.3) 1.23 (0.80–1.90) 0.34 4.5 (2.0–7.0) 0.98 (0.55–1.74) 0.95
 No charge 2.3 (-0.6–5.2) 0.58 (0.16–2.10) 0.41 9.7 (4.1–15.2) 2.24 (1.17–4.25) 0.01
 Other† 2.8 (2.4–3.2) 0.79 (0.66–0.94) 0.007 3.0 (2.5–3.5) 0.67 (0.55–0.82) < 0.001
Median household income
 0–25th percentile 4.0 (3.7–4.2) 1 (reference) 4.6 (4.3–4.9) 1 (reference)
 26–50th percentile 3.9 (3.7–4.1) 0.99 (0.90–1.09) 0.85 4.4 (4.1–4.6) 0.97 (0.87–1.08) 0.57
 51–75th percentile 3.7 (3.5–3.9) 0.91 (0.83–1.01) 0.06 4.3 (3.9–4.6) 0.95 (0.85–1.06) 0.35
 76–100th percentile 3.3 (3.1–3.6) 0.81 (0.73–0.90) < 0.001 4.1 (3.8–4.4) 0.91 (0.81–1.03) 0.13
Length of stay (day) NA 1.02 (1.02–1.03) < 0.001 NA 1.01 (1.00–1.02) 0.02
 Discharge status
 Routine 2.9 (2.7–3.0) 1 (reference) 3.8 (3.6–4.0) 1 (reference)
 Transfer to short-term hospital 5.0 (2.6–7.4) 1.37 (0.82–2.29) 0.23 3.6 (0.8–6.4) 0.78 (0.35–1.76) 0.56
 Transfer to SNF, ICF, other 6.7 (6.3–7.1) 1.76 (1.61–1.92) < 0.001 6.2 (5.8–6.7) 1.34 (1.20–1.48) < 0.001
 Home health care 4.0 (3.8–4.3) 1.18 (1.09–1.29) < 0.001 4.5 (4.2–4.9) 1.07 (0.98–1.18) 0.13
 Against medical advice 6.4 (2.2–10.6) 1.65 (0.80–3.40) 0.17 7.4 (1.6–13.1) 1.62 (0.68–3.84) 0.27
Admission type
 Nonelective admission 5.9 (5.4–6.5) 1 (reference) 5.4 (4.7–6.0) 1 (reference)
 Elective admission 3.5 (3.4–3.6) 0.79 (0.70–0.89) < 0.001 4.2 (4.1–4.4) 0.95 (0.82–1.09) 0.43
Elixhauser Comorbidity Index score
 0 2.3 (2.1–2.5) 1 (reference) 2.8 (2.5–3.2) 1 (reference)
 1 2.7 (2.5–2.9) 1.12 (0.98–1.29) 0.10 3.5 (3.2–3.8) 1.20 (1.02–1.39) 0.02
 2–3 3.8 (3.6–4.0) 1.50 (1.29–1.74) < 0.001 4.4 (4.1–4.6) 1.46 (1.24–1.71) < 0.001
 4–5 5.4 (5.1–5.8) 1.91 (1.61–2.26) < 0.001 6.0 (5.6–6.5) 1.96 (1.62–2.36) < 0.001
 ≥6 7.3 (6.5–8.0) 2.15 (1.74–2.66) < 0.001 7.4 (6.4–8.4) 2.23 (1.75–2.84) < 0.001
Type of surgery
 Decompression alone 4.6 (4.3–4.9) 1 (reference) 5.4 (5.0–5.7) 1 (reference)
 Fusion 3.5 (3.3–3.6) 0.81 (0.75–0.88) < 0.001 4.0 (3.9–4.2) 0.79 (0.72–0.86) < 0.001
 Anxiety
  No 3.6 (3.5–3.7) 1 (reference) 4.2 (4.0–4.4) 1 (reference)
  Yes 4.3 (4.0–4.7) 1.10 (1.00–1.21) 0.04 5.0 (4.6–5.4) 1.12 (1.01–1.24) 0.03
 Osteoarthritis
  No 3.7 (3.5–3.8) 1 (reference) 4.2 (4.0–4.4) 1 (reference)
  Yes 4.0 (3.6–4.3) 0.94 (0.86–1.03) 0.19 5.2 (4.8–5.6) 1.14 (1.04–1.25) 0.007
 Osteoporosis
  No 3.7 (3.5–3.8) 1 (reference) 4.3 (4.2–4.5) 1 (reference)
  Yes 4.9 (4.3–5.5) 1.16 (1.01–1.34) 0.04 4.5 (3.8–5.2) 0.92 (0.77–1.09) 0.33
 Obesity
  No 3.6 (3.5–3.7) 1 (reference) 4.2 (4.1–4.4) 1 (reference)
  Yes 4.2 (3.9–4.4) 0.94 (0.86–1.02) 0.12 4.6 (4.3–5.0) 0.88 (0.80–0.98) 0.02
 Alcohol use disorders
  No 3.7 (3.6–3.8) 1 (reference) 4.3 (4.1–4.5) 1 (reference)
  Yes 5.2 (4.1–6.3) 1.01 (0.80–1.28) 0.92 7.3 (5.7–9.0) 1.32 (1.03–1.70) 0.03
Cause Readmission between 91 and 180 days (%)
Total index patients (n = 96,562) 5,191 (5.4)
Surgical site-related 9.7
 Internal orthopedic device or implant complication 5.4
  Displacement of internal fixation device of vertebrae 1.5
  Breakdown of internal fixation device of vertebrae 0.4
  Infection due to internal fixation device of spine 0.3
  Mechanical loosening of other internal prosthetic joint 0.2
  Other specified complication 0.3
  Pain due to internal orthopedic prosthetic devices, implants and grafts 0.2
 Postoperative musculoskeletal system complication 2.5
  Pseudarthrosis after fusion or arthrodesis 1.8
  Postlaminectomy syndrome 0.4
  Postoperative hematoma and seroma of a musculoskeletal structure 0.2
 Other surgical care complication 1.7
  Infection 1.0
Nonsurgical site-related 46.0
 Spondylopathies/spondyloarthropathy 17.5
  Spinal stenosis 8.7
  Spondylosis 1.9
  Thoracic, thoracolumbar and lumbosacral intervertebral disc disorders with radiculopathy 1.3
  Radiculopathy 0.9
  Other thoracic, thoracolumbar and lumbosacral intervertebral disc displacement 0.7
  Cervical disc disorder with radiculopathy 0.5
  Cervical disc disorder with myelopathy 0.5
  Other thoracic, thoracolumbar and lumbosacral intervertebral disc degeneration 0.4
 Osteoarthritis 16.7
  Unilateral primary osteoarthritis of hip 9.2
  Unilateral primary osteoarthritis of knee 4.9
  Primary osteoarthritis of other joints 1.6
  Bilateral primary osteoarthritis of knee 0.6
  Bilateral primary osteoarthritis of hip 0.4
 Septicemia 4.7
  Sepsis, unspecified organism 3.1
  Sepsis due to other Gram-negative organisms 0.9
  Sepsis due to Staphylococcus aureus 0.3
 Heart failure 2.1
  Hypertensive heart disease with heart failure 1.1
  Hypertensive heart and chronic kidney disease with heart failure 0.8
 Cardiac dysrhythmias 1.8
  Unspecified atrial fibrillation and atrial flutter 0.6
  Paroxysmal atrial fibrillation 0.5
  Persistent atrial fibrillation 0.3
 Coronary atherosclerosis and other heart disease 1.7
  Atherosclerotic heart disease of native coronary artery 1.5
 Pneumonia 1.5
  Pneumonia, unspecified organism 1.0
  Lobar pneumonia, unspecified organism 0.3
Table 1. Characteristics of included patients (n=180,281)

SD, standard deviation; IQR, interquartile range; SNF, skilled nursing facility; ICF, intermediate care facility.

Weights provided by the Healthcare Cost and Utilization Project, Nationwide Readmissions Database were used to ensure that the estimates were nationally representative, and weights and design variables were included to obtain unbiased estimates and standard errors.

“Other” includes Worker’s Compensation, CHAMPUS (Civilian Health and Medical Program of the Uniformed Services), CHAMPVA (Civilian Health and Medical Program of the Department of Veteran’s Affairs), Title V, and other government programs.

“Smoking” includes tobacco/nicotine dependence, and secondhand smoke exposure.

Table 2. Top 10 causes of readmission between 0 and 7 days coded by clinical classifications software refined for the International Classification of Diseases, Tenth Revision, Clinical Modification Diagnoses
Table 3. Predictive factors of readmissions at different periods* (0–7 days and 8–30 days)

OR, odds ratio; CI, confidence interval; NA, not available; SNF, skilled nursing facility; ICF, intermediate care facility.

This table includes only predictors with statistically significant estimates for at least one of the 4 periods.

“Other” includes Worker’s Compensation, CHAMPUS (Civilian Health and Medical Program of the Uniformed Services), CHAMPVA (Civilian Health and Medical Program of the Department of Veteran’s Affairs), Title V, and other government programs.

Table 4. Top 10 causes of readmission between 8 and 30 days coded by clinical classifications software refined for the International Classification of Diseases, Tenth Revision, Clinical Modification Diagnoses
Table 5. Top 10 causes of readmission between 31 and 90 days coded by clinical classifications software refined for the International Classification of Diseases, Tenth Revision, Clinical Modification Diagnoses
Table 6. Predictive factors of readmissions at different periods* (31–90 days and 91–180 days)

OR, odds ratio; CI, confidence interval; NA, not available; SNF, skilled nursing facility; ICF, intermediate care facility.

This table includes only predictors with statistically significant estimates for at least one of the 4 periods.

“Other” includes Worker’s Compensation, CHAMPUS (Civilian Health and Medical Program of the Uniformed Services), CHAMPVA (Civilian Health and Medical Program of the Department of Veteran’s Affairs), Title V, and other government programs.

Table 7. Top 10 causes of readmission between 91 and 180 days coded by clinical classifications software refined for the International Classification of Diseases, Tenth Revision, Clinical Modification Diagnoses

Table 1.

Table 2.

Table 3.

Table 4.

Table 5.

Table 6.

Table 7.

NS : Neurospine
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