30- and 90-day readmission after elective spine surgery—does postoperative inpatient medical optimization affect readmission rates: a retrospective cross-sectional study

Introduction

Background

Spine decompression, instrumentation and fusion are some of the most performed elective orthopedic procedures. The rate of spine surgery continues to grow due to patient demand, advancement in technology, equipment, and approaches; however, readmission and associated health care costs continue to be a measure of health care success and patient outcomes (1). With the advent of new bundled payment systems, such as the Bundled Payments for Care Improvement model, 90-day readmission rates are critical to hospitals, health insurance companies responsible for coverage and subsequently physicians caring for patients. Similarly seen with joint arthroplasty, the bundled payment allows for a predetermined time period of care which reimburses a fixed amount for the entirety of the patient’s care including surgery and postoperative management (2). A recent cost analysis study performed at an urban medical center in New York demonstrated that the bundled payment model had increased total cost for spinal fusion by $8,291, which was attributed to surgical technique and instrumentation (3). While examining the modifiable components of the bundled payment, post-operative readmissions represent an area where cost reduction can be achieved. Rubel et al. found that the average cost for elective lumbar patients in the non-readmit cohort was $34,241 [standard deviation (SD) $23,303] and cost for readmitted patients within 90 days to be $129,527 (SD $96,221), a mean added cost of $95,286 (2).

In 2017, approximately 20% of all Medicare patients undergoing spine surgery were readmitted within 30 days, most commonly due to inefficient coordination of care post-operatively (4). A meta-analysis and systemic review by Bernatz and Anderson found 30-day readmission rates between 2.6% and 14.2% amongst 13 studies (5). Within those studies it was determined the most common reason for readmission was wound infection (28.2%) and medical complication (26.6%) which included deep venous thrombosis, pulmonary embolism (PE), pneumonia, or urinary tract infections (5). Several studies have demonstrated risk factors for readmission for 30 days following spine surgery including American Society of Anesthesiologists (ASA) score of 4+, operative duration, intensive care unit (ICU) admission, previous spine surgery and Medicare/Medicaid insurance (1,5,6). Rubel et al. reviewed 169,788 patients undergoing elective lumbar surgery and their 90-day readmission rates were 2.5% with associated predictors for readmission such as anemia, uncomplicated diabetes, diabetes with chronic complications, disruption of surgical wound during index admission, acute myocardial infarction, self-pay, and anterior approach (2).

Rationale and knowledge gap

To the authors’ best of knowledge, no study has determined if the number of inpatient consults and length of stay (LOS) affects the readmission rate. The authors of this study believed that this study affords interprofessional opportunities to improve patient outcomes and optimization in the early postsurgical period with the goal of decreasing medical costs associated with readmission and subsequent medical workups.

Objective

The primary purpose of this study was to determine if the number of consults at discharge, indicating medical optimization, leads to a decreased 30- and 90-day readmission rate. The secondary purpose was to determine if the LOS affects the rate of readmission. The authors present this article in accordance with the STROBE reporting checklist (available at https://asj.amegroups.com/article/view/10.21037/asj-24-1/rc) (7).

Methods

After obtaining institutional review board approval, a retrospective database review was performed. Inclusion criteria were all patients 18 years or older who had undergone elective spine surgery and required at least one night of hospital admission after the index procedures between a 17-month period from 1/1/2014 to 5/11/2015 at the University of Toledo Medical Center. Exclusion criteria were patients that were same day discharge, spine trauma requiring stabilization, infection, or oncologic spinal tumors. All index surgeries were performed at a single academic center by five fellowship trained spine surgeons, three orthopedic and two neurosurgeons. All patients admitted from all spine surgeons that fit inclusion criteria during this timeline were evaluated to minimize risk of confounding variables or biases. The patients were categorized into surgical groups based on the type of index procedure to better convene the patient population included in the study. The surgical groups included 1 level anterior cervical discectomy and fusions (ACDFs), ≥2 level ACDF, posterior cervical procedures, single level, two level and three or more level lumbar decompression and fusions, kyphoplasty, laminectomy alone, and microdiscectomy alone. A total of 593 patients were identified and included in the study. At the institution the authors practice at, microdiscectomies are the only procedure where patients may be able to discharge home the same day of surgery. The electronic medical records were reviewed for patient demographics such as gender and age, index surgical diagnosis, medical comorbidities, ASA scores, LOS, number of consults and which services were consulted. Readmission of patients within 30 days of their spine procedure and 31–90 days from spine procedure with associated reason for admission were recorded into each respective group. Medical comorbidities that were collected included hypertension, diabetes mellitus, cardiac disease, obesity, chronic kidney disease, thyroid disease, asthma/chronic obstructive pulmonary disease, autoimmune diseases, psychologic conditions, and other. Reasons for readmission were categorized into deep venous thrombosis/PE, cerebrospinal fluid (CSF) leak, neurological complications which were typically a result of weakness or numbness, tingling in an extremity, instrumentation complications, recurrent pain, renal complications, cardiac complications, gastrointestinal (GI) complications, and pulmonary complications.

The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the Department for Human Research Protections Biomedical Institutional Review Board (IRB #200582) at the University of Toledo and individual consent for this retrospective analysis was waived.

Statistical analyses

All data available within patient’s chart was collected for analysis, however, we cannot account for missing documentation such as incomplete past medical history retrospectively. Statistical analyses were performed using SPSS 11.0 (IBM Corp., Armonk, NY, USA) for Windows. The patients’ demographics and outcomes of the two groups (readmitted and not readmitted) were compared using t-test or Mann-Whitney nonparametric tests (where appropriate) for continuous variables and χ² tests for categorical variables. Logistic regression models were used to assess the impact of the number of postoperative consults on 30- and 90-day readmission. In both models, the authors adjusted for the effect of age and number of comorbidities. The authors then used Shapiro-Wilk test for normality distribution of the continuous variables. Only LOS was not normally distributed, so we used non-parametric test for this variable.

Results

Patient demographics

A total of 593 patients were identified from January 2014 to May 2015 having underwent admission after an index elective spine procedure. The average patient age was 50.8 years (range, 26–90 years). Of these 593 patients, 343 of them were females (57.8%) and 250 were males (42.2%). The average estimated blood loss for all surgeries was 300 cc (range, 100–900 cc). The average ASA classification for the patient population in this study was 1.99. Subgroup analysis demonstrates an average ASA in the non-readmitted population to be 1.95, 2.31 in the 30-day readmitted group, and 2.24 in the 90-day readmitted group. Patients were categorized into groups based on which type of index spinal procedure was performed. Table 1 outlines patient demographics, the number of patients that underwent each procedure and the total number of patients that were not readmitted or readmitted at 30 or 90 days for each procedure.

Post-operative consults and readmission rate

From the 593 patients included in study, the average number of diagnoses at discharge was 2.36, and average number of inpatient consults was less than 1 (0.13) with a range of 0–4 total consults. There was a total of 78 consultations with hospitalist service being the most common (63 consults), followed by cardiology (6). Neurology, psychiatry, and urology received two consultations and urology, pulmonology, and heme/oncology received one consultation each (Table 2). Table 1 outlines the average number of consults for patients within the non-readmitted group, 30-day, and 90-day readmission as 0.11, 0.29 and 0.33 respectively. Additionally, Table 2 outlines the number of each consultation based on type of comorbidity. It is noteworthy that patients admitted within 90 days had the highest average number of consultations. Patients that typically received hospitalist consultation had a higher prevalence of hypertension, diabetes mellitus, history of heart disease, and pulmonary disease such as asthma or chronic obstructive pulmonary disease. The authors of the current study found as the number of consultations increased during initial admission, there was a significant odds reduction in both 30- and 90-day readmission. The current study found there was a 49% and 48% reduction in 30-day [P=0.02, odds ratio (OR) 0.51, 95% confidence interval (CI): 0.29–0.89] and 90-day (P=0.01, OR 0.52, 95% CI: 0.31–0.87) readmission, respectively, based on number of postoperative consults (Table 3).

LOS and readmission

The median LOS was 2 days (range, 1–12 days), and the interquartile range (IQR) was between 1 and 3 days. The median LOS during the initial hospital admission were significantly higher for 30-day readmitted patients compared to patients who did not require readmission [3 (IQR, 2–5) vs. 2 (IQR, 1–3) days, P=0.002]. The median LOS during the initial hospital admission for 90-day readmitted patients was significantly higher than that for not readmitted patients [3 (IQR, 2–4) vs. 2 (IQR, 1–3) days, P=0.03].

Forty-seven patients (7.9%) were readmitted within 30 days of hospital discharge. Surgical complications accounted for 33 (5.6% of entire study population and 70% for readmitted population) patients which included wound complications (n=21), pain (n=4), instrumentation complications (n=3), neurologic complication (n=3), CSF leak (n=2) (Table 4). Medical complications resulted in 14 (2.4% of entire study population and 30% for readmitted population) patients which included cardiac related (n=5), pulmonary (n=5), and renal (n=4).

Thirty-eight patients (6.4%) were readmitted between 31 and 90 days of discharge. Surgical complications accounted for 21 (3.5% of study population and 55% of readmitted population) patients which included wound complications (n=11), pain (n=4), instrumentation complications (n=3), and neurological issues (n=3) (Table 4). Readmission for medical reasons was totaled to be 17 (2.9% of study population and 45% of readmitted population) patients including GI complications (n=6), cardiac (n=5), pulmonary (n=3), renal (n=3) and PE (n=1). One patient was readmitted for both GI and renal complications. There were 4 (0.7%) patients that were readmitted within both 30- and 90-day time periods from discharge.

Discussion

Key findings

Data for readmission at the 30- and 90-day has been reported with variations in rates and causes for readmission. The current study included 593 patients that underwent elective spine surgery at academic medical center found to have 30- and 90-day readmission rates of 7.9% and 6.4% respectively. Of the 7.9% for 30-day readmission, 5.6% (n=33) were attributed to surgical causes and 2.4% (n=14) were medical causes. Of the 6.4% for 90-day readmission, 3.5% (n=21) were due to surgical causes and 2.9% (n=17) were attributed to medical causes. Within the readmitted population, surgical complications were found to be the primary causes for both 30- and 90-day readmission (70% and 55%, respectively) with wound complications and pain control issues being the most common reason for readmission. When controlling our study population for age and number of medical comorbidities, the results of this study found the number of consults while admitted during the index admission had a 49% odds reduction in readmission at 30 days. The number of consults at index admission had the odds reduction of 48% of readmission at 90 days. Additionally, the median LOS was 2 days (range, 1–12 days) during the initial admission, with a significant median LOS for readmitted patients within 30 and 90 days when compared to not readmitted patients (P=0.002 and P=0.03, respectively).

Strengths and limitations

The highlights of this study provide a unique perspective on identifying patients who may be at an elevated risk for readmission after elective spine surgery. The authors of the current study believe there is situational value of inpatient consultation and associated additional LOS to provide adequate time to optimize patients for safe discharge, decrease the odds of readmission and thus lower healthcare related costs.

The current study has the inherent limitation of being a retrospective study and depends on data entered into a clinical database with some incomplete information. The data is from a tertiary care center, where there may be patient selection bias for those with more medical comorbidities; medical optimization prior to discharge appeared to be protective of subsequent readmission. Additionally, there are potential confounding factors that may contribute to increased risk of patient readmission that was not collected in this study such as fragility of patients or insurance status.

Some patients may present at an outside hospital and require admission after surgery, most of these patients were usually transferred to the authors’ hospital where the index surgical procedure was performed and therefore counted as readmission. However, this cannot be universally applied as some of these patients may be admitted to an outside hospital, but the authors did not have a database system to track all outside hospital admissions.

Comparison with similar research

Duc et al. investigated 30- and 90-day readmission rates in 1,399 patients that underwent lumbar surgery and found medical causes for 30-day readmission consisted of majority medical issues (64%) which was significantly higher (P<0.001) than surgical causes (36%) (8). Interestingly their data showed a higher discrepancy at 90 days; 85% medical vs. 15% surgical causes for readmission. This study contrasts our results where we had a larger proportion readmitted as a result of surgical causes, however, this study could further support medical co-management to optimize patients prior to discharge to try lowering the number of medical readmittance. Furthermore, similar to our results, Hills et al. retrospective review of unplanned 90-day readmissions amongst 2,761 patients undergoing spine surgeries found surgery related reasons (52%, n=82) to be the most common reason (9).

In conjunction with our study, these results bring a cause for concern to investigate root causes of each medical and surgical issue. It seems wound complications and pain control issues are commonly at the top of the list. The study by Hill et al. discussed their surgical causes encompass surgical site infections, surgical failure, CSF leaks and wound related issues (9). The second most common reason was medical complications (38%, n=60), followed by pain (10%, n=15). Adogwa et al. found 34.8% of readmissions after spine surgery were due to concerns for infection, and 19.7% were for pain control (4). Our results found the most common causes for readmission after spine surgery to be attributed to wound complications and pain control for both time frames (Table 4) and correlate with previously published studies that early readmissions within 30 days are likely related to surgical issues (5,8-10).

Explanation of findings

The interpretation of the data does not prove causation; however, Table 1 demonstrate the delineation between which types of surgeries patient are readmitted with and associated demographic data such as age, gender, LOS, average number of consults for patients both 30 and 90 days. While controlling for age and number of medical comorbidities we did note the number of consults during the initial admission was related to a significant odds reduction in readmission at 30 and 90 days. Interestingly, LOS, average number of consultations, and ASA classification was higher in the patients that were readmitted. We attribute these findings to patients with more medical comorbidities, thus higher ASA, typically require more consultations. This can lead to inherently longer lengths of stay to allow for optimization of the patient to allow for safe discharge. Additionally, the reason for readmission for our patient population was proportionally more likely to be related to surgical causes than medical at both 30 and 90 days. As previously stated, this contrasts the literature but may be a unique finding because patients are less likely to be readmitted for medical causes due to the optimization at their index admission. The complexity of surgeries undoubtedly leads to prolonged anesthesia time, larger blood loss, and higher pain control issues which play a role in higher risk of readmission. Posterior cervical procedures demonstrate a noteworthy percentage of the patients being readmitted. This may be attested to the high complication rates with posterior cervical decompression and fusion cases, reported between 15–25% and as high as 49% (11). The authors of this study believe there may be a potential benefit to increased LOS peri-operatively for patients with specific risk factors such as medical comorbidities, complexity of surgery, and blood loss requiring additional interprofessional co-management to optimize patients prior to discharge. The authors of this study believe there is utility in interprofessional co-management of patient care with nursing staff, therapists, social workers, and additional specialty teams for patients with complex medical comorbidities. At our facility we see this time as an opportunity to allow increased surveillance and management of pain control in the early peri-operative period, patient education including discharge pain regimen, adequate patient mobilization, proper discharge disposition, and sufficient stabilization of medical comorbidities by consulting physicians if needed. Brown et al. investigated if short stays in elective spine surgeries benefit patients and found that LOS ≤1 day showed an overall increase in the odds of hospital readmission when controlling for age and body mass index (BMI) (12). Our data shows that the number of consults is related to odds reduction in readmission. Our readmitted populations did have higher ASA values and comorbidities suggesting optimizing medical and surgical treatment prior to hospital discharge may decrease the readmission rate following elective spine surgery.

On the contrary, not every patient requires prolonged hospitalization and unnecessary consultation to medical services as many of these patients are likely preoperatively optimized by their primary care and subspeciality physicians to clear them for surgery. However, unforeseen events do occur and preoperative discussions about postoperative expectations may be forgotten given the psychological strain patients endure when preparing for surgery. Attempts to identify patients at risk of readmission may allow for intervention prior to discharge to reduce readmission rates. Identifiable risk factors for readmission after elective spine procedures include older patients, male sex, African Americans, ASA class >II, more levels involved, anterior approach, higher baseline Oswestry Disability Index (ODI) scores, development of a cardiac complication, and obesity (10,13-16).

Implications and actions needed

Several initiatives have been set forth to aid in prediction of those patients at risk for post-operative readmission. Sivaganesan et al. initiated a perioperative order set for routine use in patients undergoing elective spine surgery that involved standardized activity, early mobilization, bracing, multimodal pain control, antibiotics, and discharge planning prior to surgery. With a standardized approach, they were able to decrease their LOS during admission and decrease 90-day complications, however, no differences were noted in 90-day readmission rates (16). Additionally, Abt et al. found that discharge to rehabilitation was associated with a decreased odds of 30-day unplanned readmission following elective spine surgeries (17). Villavicencio et al. studied unplanned readmissions after spine surgery and found that longer hospitalizations were a highly significant predictor of wound related complications, discharge to home or with home health and patients with lower ASA scores (6). Interestingly, they found that younger age patients predicted readmission due to pain and higher ASA predicted readmission due to medical complications rather than surgical complications (6). What seems to be left undealt with is wound complications within the 30- and 90-day period. Undoubtedly continued research is required to further address these issues including potential subgroup analysis of what types of patients are getting wound related complications, if use of extended oral antibiotics provides any benefit, or postponing surgery in patients with uncontrolled diabetes and smokers versus utilizing minimally invasive techniques as this population is typically known for healing complications regardless of surgical procedure performed.

In addition to our surgical skills as spine surgeons, being a clinician and health care provider includes identifying patients at high risk to be medically optimized postoperatively, even at the cost of an extended inpatient hospital stay to decrease the risk of future readmission. Other studies have demonstrated surgical complications such as infections or wound complications are the most common (4,9). Villavicencio et al. does suggest that prolonged hospitalization may lead to higher chance of surgical site infections and subsequently higher readmission rates (6). However, the data from the current study demonstrates these patients are medically complex, and the risk of readmission may warrant optimization through medical consultation co-management. The current study demonstrates that patients who received more inpatient consultations have an odd reduction in both 30- and 90-day readmission and that the number of comorbidities likely plays a significant role in readmission rates. In 2021 hospital adjusted expense per inpatient day nationally to be $2,883/day based on the American Hospital Association national survey (18). In our perspective, an additional inpatient stay for $28,883 per day to allow for better pain control with a dedicated discharge regimen in place, appropriate discharge disposition, stabilization of medical comorbidities, and extra strengthening/mobilization far exceeds the risk of readmission. Patient readmission not only worsens patient morbidity and decreases patient satisfaction but can result in extensive hospital costs as Rubel et al. previously stated a mean added cost of over $95,000 for a lumbar spine patient readmission (2).

Conclusions

Patients medically optimized at discharge, following elective spine surgery, have a much lower likelihood of readmission at 30 and 90 days postoperatively. Medical optimization may require increased number of inpatient consultations and a longer LOS but may decrease associated penalties with post-operative readmissions.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://asj.amegroups.com/article/view/10.21037/asj-24-1/rc

Data Sharing Statement: Available at https://asj.amegroups.com/article/view/10.21037/asj-24-1/dss

Peer Review File: Available at https://asj.amegroups.com/article/view/10.21037/asj-24-1/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://asj.amegroups.com/article/view/10.21037/asj-24-1/coif). H.E. serves as an unpaid editorial board member of AME Surgical Journal from October 2023 to September 2025. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the Department for Human Research Protections Biomedical Institutional Review Board (IRB #200582) at the University of Toledo and individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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