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Abstract

Study design

Systematic review.

Objectives

Surgical procedures for lumbar degenerative diseases (LDD), which have emerged in the 21-century, are commonly practiced worldwide. Regarding financial burdens and health costs, readmissions within 30days following surgery are inconvenient. We performed a systematic review to integrate real-world evidence and report the current risk factors associated with 30-day readmission following surgery for LDD.

Methods

The Cochrane Library, Embase, and Medline electronic databases were searched from inception to April 2022 to identify relevant studies reporting risk factors for 30-day readmission following surgery for LDD.

Results

Thirty-six studies were included in the review. Potential risk factors were identified in the included studies that reported multivariate analysis results, including age, race, obesity, higher American Society of Anesthesiologists score, anemia, bleeding disorder, chronic pulmonary disease, heart failure, dependent status, depression, diabetes, frailty, malnutrition, chronic steroid use, surgeries with anterior approach, multilevel spinal surgeries, perioperative transfusion, presence of postoperative complications, prolonged operative time, and prolonged length of stay.

Conclusions

There are several potential perioperative risk factors associated with unplanned readmission following surgery for LDD. Preoperatively identifying patients that are at increased risk of readmission is critical for achieving the best possible outcomes.

Keywords

lumbar degenerative diseases readmission risk factors spine surgery

Introduction

With the increase in average life expectancy, lumbar degenerative diseases (LDD), including spondylolisthesis, disc degeneration, and spinal stenosis, are becoming increasingly common worldwide.¹ LDD often induce lower back pain, lower extremity numbness or pain, claudication, and disability,¹ which results in negative effects on the patient’s quality of life. Surgical treatment is indicated for patients in whom medical therapy fails. With advances in patient care and medical technologies, an increasing number of patients are willing to undergo surgery. Therefore, surgical procedures for LDD, such as decompression, discectomy, fusion and implantation of prostheses, have emerged in the 21st century.² Spine surgery and related care expenditures significantly contribute to healthcare economics.³ Regarding financial burdens and health costs, readmissions within 30 days following surgery (30-day readmission) are troublesome.^4,5

The American College of Surgeons National Surgical Quality Improvement Program (NSQIP)⁶ has registered 30-day readmissions following spine surgery in the database since 2011.⁷ The incidence of 30-day readmissions following spine surgery for LDD is approximately 5-10%, varying according to the procedure.^8,9 Although several studies aimed to identify predictors of 30-day readmissions from either nationwide or institutional databases, the reported risk factors or predictors were not consistent in the literature.

From the literature review, only 1 meta-analysis in 2014,¹⁰ summarized the predictors of 30-day readmission following not only surgeries for LDD but all spinal surgeries. Therefore, a great diversity of spinal pathologies, including tumors, deformities, trauma, infection, and degeneration were included at the surgical level, encompassing the cervical, thoracic, and lumbar spine. In recent years, there has been an increase in publications focusing on readmission following surgeries for LDD. Therefore, we aimed to perform a systematic review to integrate real-world evidence and update the risk factors associated with 30-day readmission following surgery for LDD.

Methods

We conducted the present systematic review based on the Cochrane Handbook for Systematic Reviews and Interventions¹¹ and reported the results following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and Meta-analysis Of Observational Studies in Epidemiology guidelines (eMethods 1 and 2 in the supplementary information). This review was registered on the PROSPERO online platform (ID: CRD42022312510). Electronic databases of the Cochrane library, Embase and Medline were searched, from the inception of the database until April 2022 encompassing all languages. Two investigators (LYC and YC) independently conducted the search to identify relevant studies to be included, and any discrepancy was addressed by reaching a consensus or by consulting senior reviewers (PHL, CCH and JSL). The search details are presented in eMethod 3 in the supplementary information.

Eligibility Criteria

The articles meeting the following criteria were included:

(1) Prospective/retrospective cohort or case-control studies were included; in contrast, case reports, editorials, letters to the editor, review articles, and conference abstracts were excluded; (2) studies reporting at least 1 risk factor for 30-day readmission following spine surgeries were included; (3) studies of spine surgeries with non-degenerative conditions were excluded (eg, traumatic injuries, infections, deformities, or tumors); (4) studies with less than 20 readmitted patients were excluded; and (5) studies of robotic surgeries and endoscopic spine surgeries were excluded because of the apparent variation compared to conventional surgical procedures.

Data Extraction

Two investigators independently extracted relevant information from the tables or results of eligible articles. Extracted data included the first author’s name, publication year, country where the study was conducted, data source, inclusion criteria, exclusion criteria, follow-up time, number of participants, and significant risk factors for readmission with multivariable adjustment.

Quality Assessment

Two investigators independently completed a critical appraisal of the included literature using the Quality In Prognosis Studies (QUIPS) tool.¹² The domains included patient selection, study attrition, measurement of prognostic factors, outcome measurement, study confounding, statistical analysis, and reporting, which were rated as having a low, moderate, or high risk of bias. Any item on which assessors did not reach consensus was addressed through discussion with a third investigator (JSL).

Results

Study Selection

Our search strategy identified 6482 references from the Cochrane Library, Embase, and Medline electronic databases. After screening the titles and abstracts, we excluded duplicates (n = 676) and irrelevant references (n = 5714). The remaining 92 studies were retrieved for full-text review, 36^7-9,13-45 of which were included in the review. (Figure 1).

Figure 1.

PRISMA diagram. We initially extracted 6482 potential references. Eventually, 36 studies fulfilled the eligibility criteria, and were included.

Study Characteristics and Risk Factors

A total of 36 studies^7-9,13-45 were included (Table 1). Of these, 26^{7,13-18,20-22,24,25,27,28,33-40,42-45} were retrospective cohort studies, 1²³ was a prospective cohort study and 9^{8,9,19,26,29-32,41} were case-control studies. Among them, 20^{7,9,15-17,23,25,26,29,32-36,38-40,42,44,45} included patients from the NSQIP database, 2 from State Inpatient Databases (SID)^13,28, 3 from Nationwide Readmissions Database (NRD)^8,18,41, 4 from the Medicare database^20,24,37,43, 2 from the Quality Outcomes Database (QOD)^21,22, and 3 from institutional database^14,19,31. In addition, 1 study³⁰ enrolled patients from both the NSQIP and NRD and another 1²⁷ enrolled patients from the QOD, DaneSpine database and Japan Multicenter Spine Database (JAMSD).

Quality Assessment of the Included Studies

The quality assessment of the inclusion studies using QUISP is summarized in Supplemental eTable 1.

A total of 23 studies^{7-9,14,15,19,20,23,26,28-33,35,38-43,45} were defined as having a moderate risk of bias and 13 ^{13,16-18,21,22,24,25,27,34,36,37,44} were deemed to have a high risk of bias.

Table 1.

Characteristics of Included Studies.

Study	Study Design	Database	Inclusion Period	Inclusion Criteria	Exclusion Criteria	Sample Size	Significant Risk Factors
Badhiwala 2019¹⁵	RC	NSQIP	2011-2015	Lumbar spinal fusion for spondylolisthesis	Admission from acute care hospital, emergency department, or nursing home	2238	N/A
Blaginykh 2020¹⁶	RC	NSQIP	2012-2016	Elective posterior and posterolateral lumbar fusion	N/A	29 830	N/A
Chan 2021¹⁷	RC	NSQIP	2010-2018	Posterior lumbar decompression with or without single level posterior fusion for spondylolisthesis	N/A	15 658	Frailty score, BMI
Darveau 2021²³	PC	NSQIP	2012-2018	Laminectomy and fusion for lumbar stenosis	End organ failure, admission more than 1 day preoperatively, not arriving home, pregnancy, or missing hematocrit	16 329	Blood transfusion
Elsamadicy 2021²⁵	RC	NSQIP	2010-2016	Spinal decompression and fusion for spondylolisthesis	N/A	5296	Age, black race, malnourished, pneumonia, UTI
Garcia 2016²⁶	RCC	NSQIP	2006-2013	Elective single level ALIF	Emergent, urgent unplanned cases	2042	Age, pneumonia, wound infection
Garcia 2017⁹	RCC	NSQIP	2011-2013	Elective single level TLIF	Emergent, urgent unplanned cases	4992	Severe COPD, ASA, operative time, SSI, UTI
Kim 2014²⁹	RCC	NSQIP	2011	Lumbar decompression for degenerative disease	N/A	7016	Anemia, dependent functional status, OP time, ASA class 4
Kurian 2020³⁰	RCC	NSQIP NRD	2014-2015	PLF	Concurrent ACDF, trauma, tumors, or infections	15 025 120 977	Age, BMI, obesity, dependent status, steroid use, DM, dyspnea, dialysis, LOS, discharge to rehabilitation settings
Lee 2018³²	RCC	NSQIP	2011-2012	PLF, PLIF and TLIF	Spinal deformity surgery, anterior lumbar fusion, emergency surgery	2301	LOS, bleeding disorder, insulin dependent, wound complication, thromboembolism, transfusion
Malik 2018³³	RC	NSQIP	2012-2016	Elective 1-2-level PLF for degenerative pathologies	Multi-level fusion, fracture, fusion for malignancy	23 481	Discharge to skilled care or rehabilitation facilities
Malik 2019³⁴	RC	NSQIP	2013-2016	ALIF	Concurrent posterior approaches or laminoplasty/laminectomies, revision surgery, hybrid procedures	4011	N/A
Malik 2019³⁵	RC	NSQIP	2012-2016	1- 2-Level PLF for degenerative spinal pathology	Deformity, malignancy, or fracture cases	19 179	Chronic steroid use, age, bleeding disorder, ASA, LOS, COPD, 2-level, operative time, complications
Phan 2019³⁶	RC	NSQIP	2005-2012	PLIF or TLIF or PLF	Deformity surgery, combined anterior approaches, nonelective surgery, pregnancy, ventilator dependent, preoperative sepsis, LOS >365 days, CNS tumor, malignancy, acute renal failure	2410	Hypoalbuminemia, bleeding disorder
Ranson 2018³⁹	RC	NSQIP	2011-2014	Elective PLF	Pneumonia, sepsis, or cardiopulmonary resuscitation prior to surgery, pregnancy contaminated wound open wound or prior operation within 30 days, spinal trauma or neoplasm	22 909	Super obesity female
Samuel 2020⁴⁰	RC	NSQIP	2013-2017	Lumbar discectomy	Infection, fracture, or neoplasms, simultaneous spinal fusion or cervical spine surgery; corpectomy, osteotomy, or vertebral column resection for spinal deformity	62 690	Female, obesity, age, multi-level surgery
Wahood 2019⁴²	RC	NSQIP	2011-2015	Lumbar decompression, lumbo-sacral decompression, posterior lumbar fusion or lumbosacral fusion	Fractures, cysts, or tumors	60 222	Female, age, BMI, dependent status, CHF, COPD, dialysis, disseminated cancer, steroid use, bleeding disorder
Weaver 2019⁴⁴	RC	NSQIP	2012-2016	Elective PLF for degenerative spine pathology	Primary thoracolumbar fracture, malignancy, or deformity	23 516	Modified 5-Item frailty Index
Webb 2017⁴⁵	RC	NSQIP	2012-2014	Lumbar laminotomy or discectomy	Additional procedures or multilevel procedures	20 376	ASA class 3 or 4, prolonged operative time
Katz 2019⁷	RC	NSQIP	2005-2015	ALIF or PLIF	Emergency or nonelective procedures, or spinal deformity surgery	26 336	COPD, disseminated cancer, ASA, complications
Qin 2016³⁸	RC	NSQIP	2005-2013	ALIF, PLIF, lumbar discectomy or decompression	N/A	51 277	DM
Aladdin 2019¹³	RC	HCUP-SID	2007-2014	Lumbar spinal fusion surgery	Combined cervical fusion procedure	267 976	Black race
Jain 2019²⁸	RC	HCUP-SID	2005-2010	1-2 level lumbar spine fusion	Bone cancer/ metastases, infection, and trauma	92 262	Age, female, hispanic, black race, insurance, anterior approach, CVD, lung disease, CHF, DM, rheumatic disease, drug abuse, electrolyte disorder, osteoporosis, obesity, malnutrition
Chen 2021¹⁸	RC	HCUP-NRD	2013-2017	Elective single and multilevel lumbar spine fusion	Malnourished, anorexic, or underweight patients, and surgical indications of trauma or neoplasm	86 697	BMI
Elsamadicy 2018⁸	RCC	HCUP-NRD	2013-2014	Elective lumbar discectomy, laminectomy, or spinal fusion for degenerative disease	N/A	144 123	Age, insurance status, COPD, depression, DM, HTN, anemia, obesity
Taree 2021⁴¹	RCC	HCUP-NRD	2012-2014	PLF for intervertebral disk disorders, ankylosing spondylitis or spondylolisthesis	Nonelective surgery, LOS >365 d discharged against medical advice CNS cancer, current chemotherapy or radiation	65 121	Insurance, deficiency anemia, obesity, depression, DM, psychosis, liver disease, renal failure
Cook 2018²⁰	RC	Medicare	2012-2014	Age > 65, lumbar spinal fusion for disc herniation, disc degeneration, spinal stenosis, instability, and miscellaneous thoracolumbar disorders	Surgery not performed in an acute short-stay hospital, infection, neoplasia, spina bifida, trauma, fracture, death in hospital or within 30 days of discharge, discharge against medical advice	261 558	Age, male, black race, LOS, elixhauser score, discharge to rehabilitation settings
Donnally 2019²⁴	RC	Medicare	2005-2014	1- 2-Level lumbar spinal fusion for a degenerative lumbar spine condition	Trauma, infection, metastasis of the spine, revision surgery, concomitant cervical, thoracic, ALIF, PLIF or TLIF	18 692	Fibromyalgia
Puvanesarajah 2016³⁷	RC	Medicare	2005-2012	PLIF, PLF or lumbosacral spinal fusion surgery for degenerative disease	Prior trauma, infection, cancer, revision surgery, ≥ 3 levels, concurrent fusion	52 567	Obesity
Wang 2012⁴³	RC	Medicare	2003-2007	Elective spine procedures for degenerative conditions in the lumbosacral spine	Beneficiaries enrolled in a health Maintenance organization	284 640	Age, fusions, anterior approach, black race, charlson comorbidity index
Cook 2021²¹	RC	QOD	2012-2016	Lumbar surgery for degenerative lumbar disorders	N/A	39 732	Revision surgery
Cook 2021²²	RC	QOD	2012-2018	Lumbar surgery for degenerative lumbar disorders	Spine infection, tumor, fracture, traumatic dislocation, and neurologic paralysis	57 199	Baseline oswestry disability index
Glassman 2017²⁷	RC	QOD DaneSpine JAMSD	NA	Lumbar fusion for degenerative disease	NA	2653 1993 3798	Gender, employment status, database
Cho 20 202¹⁹	RCC	Institution	2005-2012	Elective lumbar surgery for degenerative disease	N/A	3933	Previous surgery, fusion surgery, operative time, ICU admission, LOS, medical expenses
Lee 2019³¹	RCC	Institution	2005-2015	Age > 70, degenerative lumbar spinal surgery	Tumors, deformities, trauma, or infection	1248	Abnormal electrocardiography
Arrighi-Allisan 2022	RC	Institution	2008-2016	PLF	Surgery for tumors, trauma, and infections	3226	DM
ACDF, anterior cervical discectomy and fusion, ALIF, anterior lumbar interbody fusion, ASA, american society of anesthesiologists, BMI, body mass index, CHF, chronic heart failure, COPD, chronic obstructive pulmonary disease, CVD, cardiovascular disease, DM, diabetes mellitus, HTN, hypertension, LOS, length of stay, N/A, not applicable, NRD, national readmissions database, NSQIP, national surgical quality improvement program, PC, prospective cochort, PLF, posterior lumbar fusion, PLIF, posterior lumbar interbody fusion, RC, retrospective cohort, RCC, retrospective case control

Risk Factors for 30-day Readmission

The risk factors with multivariate analysis reported in more than 2 studies are summarized in Supplemental eTable 1 and 2 in the supplementary information.

Patient Risk Factors (eTable 1)

Fifteen studies^{7,8,15,19,20,25,26,28-31,35,40,42,43} reported the association of age and readmission with multivariate adjusted odds ratio, with significant correlation observed in 6 studies^{7,19,20,25,26,43} using linear regression and 6^{8,15,28,35,40,42} using cut-off value of age.

Five studies investigated the risk of readmission in different races,^{13,20,25,28,43} with Black patients exhibiting a significantly higher risk. The impact of obesity was analyzed in 10^{7,8,18,25,28,30,31,39-41} studies, 5^{8,18,28,30,39,41} of which reported obesity as a significant risk factor, 2^18,40 reported that body mass index (BMI) > 30 was associated with a higher risk of readmission and 1³⁰ found similar correlation using linear regression of BMI.

Eleven studies^{7-9,20,25,28,31,39,40,42,43} compared the incidence of readmission between men and women with only 5 studies^{20,28,39,40,42} reporting a significant difference (4 of the studies reported a higher risk for females^28,39,40,42 and 1 for males²⁰). There was no difference in the risk of readmission between inpatient and outpatient surgery.^16,30 The impact of the American Society of Antitheology (ASA) score was reported in 8 studies.^{7,9,25,29-31,35,45} Kim et al²⁹ reported that ASA 4 was a significant risk factor compared to ASA 1. Katz,⁷ Malik³⁵ and Webb⁴⁵ reported that ASA 3 or 4 was significantly associated with readmission compared with ASA 1 or 2. Garcia⁹ also reported ASA was a significant risk factor using linear regression. Increased rates of readmission were observed in 4 of the 5 studies reporting bleeding disorder.^32,35,36,42 Anemia was considered as a risk factor in 3 of the 4 studies where it was reported.^8,29,41 Chronic pulmonary disease (non-specified) was reported in 8 studies,^{7-9,26,28,29,35,42} of which, Elsamadicy⁸ and Jain²⁸ considered it as a significant risk factor. Among these studies, 5 reported a history of chronic obstructive pulmonary disease (COPD)^7,9,26,35,42 associated with readmission. Eleven studies^{7,8,14,28-32,38,41,42} reported diabetes mellitus (DM) as a potential risk factor, 9^{7,8,14,28,30,32,38,41,42} of which showed statistically significant results in this regard. Three studies^7,28,42 reported heart failure and 2 of them^28,42 found that patients with heart failure had a higher risk of readmission. Five studies^8,29-31,42 reported hypertension and only 1⁸ considered it as a significant risk factor. Two studies^8,28 investigated the impact of hypothyroidism and found no significant differences. The impact of underlying malignancy on the risk of readmission was investigated in 3 studies^7,28,42 with only Wahood⁴² reporting a significant risk in patients with disseminated cancer. Three studies^7,30,42 investigated the influence of hemodialysis (HD) and 2^30,42 of them reported significant higher risk. Two studies investigated the impact of comorbidity with 1 using the Charlson comorbidity index⁴³ and the other using the Elixhauser score.²⁰ A higher frailty index was associated with higher risk of readmission in 3 studies.^17,25,44 A higher Oswestry disability index was associated with a higher risk of readmission in 1 study.²² Three studies^29,30,42 reported that patients with dependent status had a higher risk of readmission. Regarding preoperative nutritional status, 3 studies^25,28,36 found malnutrition to be a significant risk factor for readmission. Two studies^8,28 found that depression significantly increased readmission rates. Six studies^{7,25,29,30,35,42} compared readmission rates between patients with baseline chronic steroids and non-users and significant detrimental effect was found in 3 studies.^30,35,42 There are 2 studies^28,30 reporting alcohol abuse with significant elevated risk of readmission in 1.³⁰

Perioperative Risk Factors (eTable 2)

Three studies^19,31,43 compared the incidence of readmission following decompression alone vs fusion, and only 1 study⁴³ showed a significant difference. Two studies^28,43 investigated surgical approaches, and patients receiving surgery with anterior approach have higher 30-day readmission rate compared to posterior approach. Regarding postoperative complications, Malik,³⁵ Katz⁷ and Lee³² reported that non-specific complications were associated with a higher incidence of readmission. Garcia^9,26 identified surgical site infection, pneumonia, and urinary tract infection (UTI) as significant risk factors, and Elsamadicy²⁵ found that adverse events including pneumonia and UTI are predictors of readmission. Four studies^7,21,28,40 compared readmission in patients undergoing primary vs revision surgery, and Cook²¹ and Katz⁷ found revision surgery to be associated with a higher risk of readmission; however no difference was found in the other 2 studies.^28,40

The impact of prolonged operative time was reported in 5 studies^{9,19,29,35,45} with significant findings observed in 3 studies^9,19,29 using linear regression and 2 using cut-off values (151⁴⁵ and 210³⁵ minutes). Three studies^31,35,40 reported relevant results regarding surgical levels, and multi-level surgeries led to a higher risk of readmission in 2 studies^35,40 but no significant difference in the other 1 that reported surgical level by linear regression.³¹ Two studies^23,32 reported post/intra-operative blood transfusion and an increased risk of readmission was noted. Six studies^{19,20,30-32,35} reported the association between prolonged length of stay (LOS) and readmission rate with a positive correlation was observed in 5 studies.^{19,20,30,32,35} The impact of discharge destination was reported in 4 studies^20,30,33,34 and discharge to inpatient care facilities³³ or rehabilitation-based facilities^20,30 was associated with higher risk of readmission.

Discussion

To our best knowledge, this is the first systematic review to provide an overview of predictors of 30-day readmission following spine surgeries for LDD. We identified potential risk factors associated with 30-day readmission, including age, race, obesity, higher ASA score, anemia, bleeding disorder, chronic pulmonary disease, heart failure, dependent status, depression, DM, frailty, malnutrition, chronic steroid use, surgeries with an anterior approach, multi-level spinal surgeries, perioperative transfusion, presence of postoperative complications, prolonged operative time, and prolonged LOS, which were categorized into patient risk factors and perioperative risk factors in the following discussion.

Patient Risk Factors

Spine surgery can be safely performed in older patients and old age alone is not a contraindication for lumbar surgery.⁴⁶ However, the prevalence of co-occurring chronic diseases and disorders increases greatly with age,⁴⁷ which may negatively impact postoperative condition, recovery, and quality of life. In addition, an increase in aging bone, the degeneration of discs and facet joints, and the wasting of ligaments and muscles may lead to great destabilization and imbalance of the spine.⁴⁸ Owing to the severity of degeneration in older patients, surgical procedures have become more complex, such as longer instrumented segments, which are associated with a higher risk of complications and relatively worse clinical outcomes.⁴⁹ Based on our review, patients over 70-year-old exhibited much higher risk of 30-day readmission, which could be related not only to the surgical procedures but also to the patients’ preoperative condition.

Obesity imposes more loading on axial bones and inevitably accelerate spinal degeneration.^50,51 Furthermore, compared to the general population, obesity can lead to more adverse events following lumbar spine surgery,⁵² including increased surgical time, extended length of stay, wound complications, higher blood loss, urinary complications and thromboembolism events,⁵³ which subsequently lead to a higher incidence of unplanned readmission. Obesity is defined as a BMI ≥30, with morbid obesity being defined as a BMI ≥40. While the prevalence of obesity is on the increase, there are limited studies investigating strategies for weight loss before spine surgery in obese patients (BMI 30-40).⁵² The benefits of bariatric procedures for morbid obesity before spine surgery have been reported in several studies, including fewer overall and wound-related complications, reduced in-hospital mortality, and improved healthcare utilization.^54-56

Unplanned readmission may be related to underlying diseases and medical conditions, not the surgical procedures themselves. DM,⁵⁷ COPD⁵⁸ and heart failure⁵⁹ are common medical problems with high prevalence among older adults. Most included studies demonstrated a positive correlation of these conditions and unplanned readmission following surgery. Moreover, patients undergoing HD are vulnerable during the perioperative periods and the maintenance of stable homeostasis during hospitalization is a clinical challenge for surgeons and nephrologist.⁶⁰ On the surgical aspect, both DM and renal failure negatively impact wound healing and increases the risk of surgical site infection, which may further necessitate readmission and inpatient managements.⁶¹

Anemia and bleeding disorders are associated with a higher risk of unplanned readmissions.^8,25,29,41 Intraoperative transfusion may be required in patients with unstable hemodynamics. However, transfusion has been reported as an independent predictor of adverse postoperative outcomes,^62,63 postoperative infection,⁶⁴ and prolonged hospital stay,⁶⁵ which could explain the higher unplanned readmission rate.²³

It is evident that patients’ underlying comorbidities are detrimental to their postoperative outcomes and recovery. In this line, a positive correlation between overall comorbidities and the incidence of readmission following lumbar spinal fusion surgery has been shown.^20,43 This finding is in consistence with that higher ASA is also a significant risk factor in several studies.^9,29,35,45 There are studies^17,44 investigating the association of frailty index and unplanned readmission of patients receiving elective spinal fusion surgery, which yield the similar results. General functional status is also associated with postoperative morbidity and mortality.^29,42 Performance assessment can partially reflect the aforementioned medical comorbidities since patients with multiple underlying medical co-morbidities usually have worse functional status. Malnutrition impairs wound healing postoperatively and compromise the immune system against infection, therefore, associated with several adverse events including wound complications and surgical site infections in not only spine surgery but other orthopedic surgery.^66-68 It should be noted that presence postoperative adverse event is a strong predictor for unplanned readmission. Identifying malnourished patients and preoperative nutrition support may have benefit on postoperative outcome.⁶⁹

Chronic steroid use is associated with poor wound healing, infection, and minor or major complications following surgery.⁷⁰ Moreover, patients receiving steroids have poor bone quality, which increases the risk of implant loosening and readmission.⁷¹ No doubt, chronic steroid use increases the risks 30-day readmission following surgery for LDD.

Aside from the patients’ physical medical conditions, mental issues, such as affective disorders, are topics of interest in multiple medical and surgical fields. Affective disorders, especially depression is associated with chronic back pain in general population and unsatisfactory outcomes in spine surgeries.⁷² This is evident from the result of 2 large population-based studies^8,28 in which patients with depression were associated with higher 30-day readmission following surgeries for LDD.

Perioperative Risk Factors

With the growing number of lumbar spinal surgeries for LDD and the increasing variety of fusion techniques, it is important to clarify the comparative risk of complications and postoperative outcomes of various types of surgery. Surgical complexity may influence its results and potential complications owing to prolonged surgical time, increased tissue damage, and blood loss. Our review demonstrated that anterior lumbar surgeries were associated with a higher risk of readmission. Anatomically, in order to access to the vertebrae, the anterior approach requires the dissection and retraction of abdominal vessels, while the posterior approach needs the subperiosteal muscle dissection. The great vessels overly the disc spaces, and their retraction is essential when exploring the discs of interest through an anterior approach. Direct vascular injury can result in immediate complications and mortality, but may not necessitate readmission within 30days. However, prolonged retraction of the great vessels during ALIF may be associated with a higher risk of DVT than posterior lumbar surgery.⁷³ Furthermore, since the posterior approach is standard for most spinal pathologies, it is the most commonly practiced procedure for spinal surgeons and particularly for entry-level residents.⁷⁴ Owing to the complex vascular anatomy and lower frequency of utilization, the anterior approach may impose an increased risk of vascular and wound events, resulting in a higher readmission rate than the posterior approach.⁷⁵ However, only 2 studies^28,43 have compared the 30-day readmission risk of the anterior and posterior approaches. Wang et al⁴³ grouped patients into anterior, posterior, and concomitant anterior and posterior approach groups. Their analysis found that an anterior only approach was associated with a significantly higher incidence of readmission compared to the posterior only approach. In the other study, Jain et al²⁸ investigated patients undergoing posterior lumbar fusion, and found that patients operated on through a concomitant anterior approach experienced a significantly higher risk of readmission. Due to the limited data obtained from these studies, as well as their heterogeneity, further studies focusing on readmission with respect to surgical approach are warranted.

At the surgical level, multi-level spinal surgery is associated with a prolonged operative time, subsequently lead to postoperative complications and unplanned readmission.⁷⁶ However, Lee et al.³¹ Reported that multi-level spinal surgery is not a significant risk factor, possibly because of advances in minimally invasive surgical techniques combined with appropriate patient selection.

The prevalence of complications following spine surgery is reported in around 20-40%^77,78 of the patients, and is associated with increased morbidity, mortality, length of hospital stay, and health costs.⁷⁷ In our review, postoperative UTI, pneumonia, thromboembolism, and wound infection, were highly associated with unplanned readmission. The incidence of complications following surgery for degenerative spine disease is lower than that for trauma, infectious or malignant etiologies, which may be the result of underreporting owing to the retrospective design of most studies. The complication rate is associated with not only the complexity of the surgery but also the surgeons’ experience, which could constitute a potential bias that may be challenging to take in consideration. Moreover, there is a lack of a generalized classification system assessing complications following spinal surgery, which makes it difficult to determine its impact on postoperative outcomes. Therefore, a robust correlation between postoperative complications and unplanned readmission should be clarified with large-scale and well-designed prospective studies.

Limitations

The present systematic review had some limitations. First, we included only studies that focused on LDD. Therefore, surgeries for deformities, fractures, and spinal tumors were excluded. Also, based on our inclusion criteria, some newly developed procedures such as endoscopic spine surgery or robotic spine surgery were not included in our review.

Second, nearly half of the included studies were from the NSQIP databases, and the duplication of cohorts made the quantitative analysis of risk factors impracticable. In addition, studies from national databases or single institutions were included, and considerable variations in patient characteristics and sample sizes were observed. Third, we believe that short-term outcomes, including unplanned readmission, were influenced by the surgeon’s technical experience, which could represent a potential performance bias.

Conclusions

Through a systematic review, we identified the predictors of 30-day unplanned readmission in patients undergoing surgery for LDD. These findings may be used to identify patients at a higher risk of readmission, for whom caution should be exercised by clinicians.

Supplemental Material

Supplemental Material - Risk Factors for 30-day Unplanned Readmission following Surgery for Lumbar Degenerative Diseases: A Systematic Review

Supplemental Material for Risk Factors for 30-day Unplanned Readmission following Surgery for Lumbar Degenerative Diseases: A Systematic Review by Liang-Yi Chen, MD, Yu Chang, MD, Chia-En Wong, MD, Kuan-Yu Chi, MD, Jung-Shun Lee, MD, MSc, Chi-Chen Huang, MD, and Po-Hsuan Lee, MD in Global Spine Journal

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iDs

Jung-Shun Lee

Po-Hsuan Lee

Supplemental Material

Supplemental material for this article is available online.

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