Analysis of risk factors for surgical site infection in spinal surgery patients and study of direct economic losses

Abstract

Background

Surgical site infection (SSI) is a serious complication of spine surgery, leading to prolonged hospital stays, re-operations, and economic losses. The aim of the study was to explore the types and quantities of pathogenic bacteria involved, the incidence of SSI, and to identify the independent risk factors and direct economic impact on patients with postoperative SSI in spine surgery.

Methods

The medical records of spine surgery patients from January 2023 to April 2024 at two hospitals in Xinjiang were retrospectively reviewed. Patients with SSIs were included in the case group, and patients without SSIs were matched 1:1 based on hospital, department, age ± 5 years, primary diagnosis, and the specific surgery type. They were then subjected to univariate and multivariate paired logistic regression analyses. The Wilcoxon signed-rank test was used to compare differences in hospitalization costs and duration of stay between the two groups.

Results

A total of 38 individuals, or 0.63% of the 6018 adults who had spinal procedures, experienced SSI. Findings from the univariate analysis demonstrated a statistically significant correlation between SSI (p < 0.05), intraoperative bleeding of 300 ml or more, and the duration of indwelling drain use. Many separate risk variables for SSI were found by multivariate regression analysis: combined underlying diseases (OR 2.634, 95% CI 1.02–6.78), days with an indwelling urinary catheter (OR 1.38, 95% CI 1.01–1.88), and days with an indwelling drain (OR 1.449, 95% CI 1.01–2.07). The most prevalent bacteria identified as causing skin infections were Staphylococcus aureus and Staphylococcus epidermidis. About $1,688.50 in direct economic loss was attributable to SSI in patients undergoing spine surgery.

Conclusions

The presence of combined underlying diseases, extended use of indwelling urinary catheters, and prolonged use of indwelling drains significantly increase the risk of SSI in spine surgery patients.

Introduction

Surgical site infection (SSI) is a serious complication following spinal surgery in the United States, where up to 1 million spine surgeries are performed annually [1]. Previous studies [2–5] have reported an incidence rate of 0.49% to 16.1% among spinal surgery patients. With the increasing number of surgeries globally, the prevention of SSIs has become increasingly critical [6]. SSIs may necessitate antibiotic treatment, surgical debridement, and prolonged hospital stays [7, 8], resulting in substantial financial losses to both patients and healthcare systems [3]. From the patient’s perspective, the average direct cost of treating SSI complications ranges from $15,817 to $38,701 [9–11]. The overall incidence of SSIs following spinal surgery was 3.1% in a meta-analysis [12] including 27 investigations; 1.4% of SSIs were superficial, while 1.7% were deep. Moreover, spinal surgeries are often urgent due to progressive neurological symptoms, instability from trauma or tumors, leaving insufficient time to assess and manage preoperative conditions [13]. Consequently, accurately identifying risk factors for spinal SSIs is vital for early screening and proactive prevention.

Research has shown that some factors increase the likelihood of SSIs following spinal surgery. These include intraoperative blood loss, emergency surgery, hypoproteinemia, diabetes mellitus, and an American Society of Anesthesiologists (ASA) score of 3 [5, 14, 15]. A meta-analysis [16] of 35 studies found that SSIs could be caused by medical devices that were not properly reprocessed after use; additionally, contamination of surgical gowns, gloves, and air is another relevant factor. Economic losses from SSI are categorized into direct and indirect losses [17], with direct economic losses primarily comprising additional medical costs and extended hospital stays due to SSI treatment; and the latter encompassing increased outpatient expenses and loss of wages [18]. Blumberg et al. [19] found that 4.7% of spinal surgery patients with SSIs required a return to the operating room, 14% required readmission to the hospital for treatment of postoperative spinal infections, and the direct economic loss due to SSIs amounted to $16,242.

Although SSI is a prevalent issue following spinal surgery, the reasons behind it remain unknown, and most previous studies have focused on analyzing the economic loss from total hospital costs due to spinal SSIs. Analyses of specific cost losses caused by SSIs, such as costs for general medical services, treatment, nursing care, laboratory tests, diagnostic examinations, medications, surgical blood transfusions, and consumables are relatively few, thereby addressing a significant research gap. Thus, this study’s overarching goal is to learn more about the incidence of SSIs (both deep and superficial), the types and quantities of pathogenic bacteria involved, as well as the risk factors and financial burdens these infections impose.

Materials and methods

Study design and inclusion criteria

This retrospective study received approval from the Ethics Committee of the Fifth Affiliated Hospital of Xinjiang Medical University (certification number: XYDWFYSk-2022–12). Patients were reviewed by the Ethics Committee of the Fifth Affiliated Hospital of Xinjiang Medical University and certify that the study was performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki. Due to the observational nature of this study, each included hospital waived the requirement for informed consent. All clinical data were anonymized and de-identified before analysis. Utilizing a paired retrospective case–control design, this study retrospectively collected data on patients undergoing spinal surgery from January 2023 to April 2024 at two hospitals via the Apricot and HIS systems (Hangzhou Xinglin Information Technology Company Limited, located in Zhejiang Province, China, version information: 12.9.1.9, URL: http://www.xinglin-tech.com; Venture Huikang Technology Company Limited, which is located in Zhejiang Province, China, version information: BS-EMR5.6 Build 2017–07-18, URL: http://www.bsoft.com.cn-m.). Patients who developed SSIs postoperatively were classified as the case group, while those who did not develop SSIs comprised the control group. Inclusion criteria: (1) Patients having SSI according to the 2019 Centers for Disease Control and Prevention (CDC) National Healthcare Safety Network (NHSN) Patient Safety Manual. When an infection develops in an organ or space within 30 days after surgery, or within 90 days if a prosthetic implant is involved, it is considered a SSI [20]. This includes both deep and superficial incisional infections. (2) Availability of complete clinical records. (3) Patients ≥ 18 years of age. (4) Patients with malignant tumors. Exclusion criteria: (1) Patients with community-acquired infections upon admission. (2) Pregnant women. Matching methods: To control confounding factors, the case and control groups were matched 1:1 according to same hospital, same department, sex, age ± 5 years [21], primary diagnosis and the specific surgery type.

Data collection

Data on the variables of interest were retrospectively gathered through the hospital’s electronic systems; the Apricot system and the HIS system. Patient variables collected included: General data such as age, gender, BMI, cigarette smoking, presence of diabetes mellitus, hypertension, coronary heart disease, history of malignant tumors, and other underlying conditions, as well as the number of days hospitalized prior to surgery. Surgical-related factors encompassed ASA score, preoperative antibiotic use, minimally invasive surgery status, the duration of surgery, presence of implants, and bone grafting, intraoperative haemorrhage (typically assessed by weighing gauze bleed-through, scaling negative pressure suction bottles, and laboratory testing), and intraoperative blood transfusion; postoperative treatment factors included admission to the ICU, use of glucocorticoids, and the duration of both indwelling urinary catheters and drains. Bacterial cultures obtained before and during surgery were collected from the SSI group. Hospitalization charges were compiled, covering total hospital charges, general medical services, treatments, nursing care, laboratory tests, diagnostic examinations, medications, surgical blood transfusions, consumables, and other fees. These costs fail to distinguish between patients who underwent multiple surgical debridements due to infection and those who did not. Microbiologic culture results were recorded for all patients who developed SSI. Types of spinal surgeries performed included posterior and anterior approach spinal fusion, lumbar discectomy, internal fixation of spinal fractures with incision and repositioning, decompression of the spinal canal, and bone grafting.

Statistical analysis

We used SPSS 26.0 to do the statistical analysis. We checked if the data was normally distributed and if the variance was homogeneous, normality test was performed using the Shapiro–Wilk test. Median and interquartile range (IQR) was used to represent non-normally distributed data, whilst regularly distributed data were shown as mean ± SD. The percentages and frequencies of the categorical variables were presented. To find independent risk factors, variables having a P-value less than 0.2 were included in a paired multivariate logistic regression analysis after univariate analysis. To compare the case and control groups on hospitalization expenditures and lengths of stay, the Wilcoxon Signed Ranks Test was used. A statistically significant result was defined as p < 0.05.

Results

General data

From January 2023 to April 2024, a total of 6,018 patients underwent spinal surgery at two leading hospitals. Out of these, 38 developed SSI. One case was excluded due to incomplete medical records, three cases were discarded based on the matching condition, and 34 pairs were successfully matched. The average age of the 34 pairings who were successfully matched was 54 ± 14 years, and there were 13 men and 21 females in those pairs. The overall postoperative SSI incidence was 0.63% (38/6018), with incidences of superficial and deep SSIs at 0.45% (27/6018) and 0.17% (10/6018), respectively. The incidence of organ/space SSI was 0.02% (1/6018).

Results of univariate analyses

Table 1 outlines the relationships between study variables and SSI incidence. Univariate analysis indicated no significant differences in age, gender, BMI, cigarette smoking, diabetes mellitus, ASA score, preoperative antibiotic use, length of hospitalization before surgery, minimally invasive surgery, duration of surgery, presence or absence of implants, presence or absence of bone grafting, intraoperative blood transfusion, postoperative ICU visits, use of drainage tubes, and glucocorticosteroid treatment between patients with and without SSI. However, Intraoperative bleeding ≥ 300 ml was associated with SSI (P < 0.05), patients with SSI had a longer duration of indwelling drains (median [IQR], 5 [2.75 ~ 8] days vs. 3 [1 ~ 4.5] days; P = 0.029). Additionally, significant factors from the univariate analysis, along with those with P < 0.2 (number of co-existing underlying diseases, and duration of catheter use), were included in the multivariate paired logistic regression analysis (Table 1).

Table 1.

Clinical characteristics of patients undergoing spinal surgery

Characteristics	No SSI	SSI	χ2 /Z	P value
	n = 34 (%)	n = 34 (%)
Age
Mean ± SD	54.4±14.0	54.0±14.0	0.113a	0.911
Gende
Male	13 (25.5)	13 (25.5)	0	1
Female	21 (41.2)	21 (41.2)
BMI
<25	13 (38.2)	13 (38.2)
25-30	17 (50)	14 (41.2)
>30	4 (11.8)	7 (20.6)	1.109	0.575
Cigarette smoking
No	34(100)	32 (94.1)
Yes	0	2 (5.9)	0.515	0.473
Diabetes mellitus
No	29 (85.3	25 (73.5)
Yes	5 (14.7)	9 (26.5)	1.439	0.230
Number of combined underlying diseases
Median/IQR	0/0-1	1/0-2	-1.617	0.106
ASA score
<2	8 (49)	6 (17.6)
≥2	26 (51)	28 (82.4)	0.360	0.549
Number of days of preoperative hospitalization
Median/IQR	5/3.75-7	5/3-7.25	-0.105	0.916
Preoperative antibiotic use
No	13(38.2)	10(29.4)
Yes	21(61.8)	24(70.6)	0.591	0.442
Minimally invasive
No	29 (85.3)	31 (92.2)
Yes	5 (14.7)	3 (8.8)	0.142	0.707
Duration of surgery (min)
<180	19 (55.9)	30 (88.2)
≥180	15 (44.1)	4 (11.8)	0.060	0.806
Presence of implants
No	13 (38.2)	11 (32.4)
Yes	21 (61.8)	23 (67.6)	0.258	0.612
Bone grafting
No	25 (73.5)	26 (76.5)
Yes	9 (26.5)	8 (23.5)	0.078	0.779
Intraoperative bleeding(ml)
<300	34(100)	26(76.5)
≥300	0	8(23.5)	6.942	0.008
Intraoperative blood transfusion
No	30(88.2)	27(79.4)
Yes	4(11.8)	7(20.6)	0.976	0.323
Postoperative to ICU
No	33 (97.1)	32 (94.1)
Yes	1 (2.9)	2 (5.9)	0	1
Glucocorticosteroid treatment
No	20 (58.8)	16 (47.1)
Yes	14 (41.2)	18 (52.9)	0.944	0.331
Duration of indwelling urinary catheter(days)
Median/IQR	2/0-4	3/1-5	-1.737	0.082
Use of drain tubes
No	6(17.6)	2(5.9)
Yes	28(82.4)	32(97.1)	1.275	0.259
Duration of indwelling drains(days)
Median/IQR	3/1-4.5	5/2.75-8	-2.678	0.029

^at-test

Results of multivariate logistic analysis

The ultimate multivariate logistic regression model revealed three distinct risk factors that are independent predictors of SSI. Coexisting underlying medical conditions (odds ratio [OR] 2.634; 95% confidence interval [CI] 1.02–6.78; P = 0.045), duration of indwelling urinary catheters (OR 1.38; CI 1.01–1.88; P = 0.041), and duration of indwelling drains (OR 1.449; CI 1.01–2.07; P = 0.042) were significant predictors of SSI (Table 2).

Table 2.

Multivariate analysis of risk factors for surgical site infections in postoperative spine surgery patients

Variables	Odds ratio	Confidence interval	P value
Number of comorbid underlying diseases	2.634	1.02–6.78	0.045
Intraoperative bleeding ≥ 300(ml)	0.642	0.06–7.22	0.720
Duration of indwelling urinary catheter	1.38	1.01–1.88	0.041
Duration of indwelling drains	1.449	1.01–2.07	0.042

Microbiological characterization of SSI

Microbiological cultures were performed on all 34 patients diagnosed with SSI, and 26 of them (76.5%) yielded positive results. Staphylococcus aureus was detected in 42.3% (11/26) of the cases that tested positive. Among these cases, 18% (2/11) of the Staphylococcus aureus isolates were found to be methicillin-resistant (MRSA). Staphylococcus epidermidis was the second most common microbe, detected in 23.1% (6/26) of the positive cultures. Among these isolates, 50% (3/6) were identified as methicillin-resistant Staphylococcus epidermidis (MRSE). Additionally, Enterobacter cloacae and Escherichia coli each appeared in 7.7% (2/26) of positive cases. Less common, found in 3.8% (1/26) of cases, were the human subspecies of Streptococcus hemolyticus, Enterococcus faecium, Staphylococcus hominis, and Staphylococcus lentus (Table 3).

Table 3.

Microbiological characteristics of SSI

Organism(s)	NO. of patients	Percentage (%)
Staphylococcus aureus	11	42.3
MRSA	2
Staphylococcus epidermidis	6	23.1
MRSE	3
Enterobacter cloacae	2	7.7
Escherichia coli	2	7.7
Staphylococcus hemolyticus	1	3.8
Enterococcus faecium	1	3.8
Staphylococcus hominis	1	3.8
Staphylococcus lentus	1	3.8
Total	26	100%

Direct economic loss of SSI in spine patients

The direct economic loss attributed to SSI in spine patients was $1,688.50. Hospitalization costs for these patients included general medical services, treatments, nursing, laboratory tests, examinations, medications, proprietary Chinese medicines, surgical blood transfusions, consumables, and other charges. The Wilcocon Signed Ranks Test revealed no significant differences in the costs of proprietary medicines and surgical blood transfusions; however, there were statistically significant differences in hospitalization, general medical services, treatments, nursing, laboratory tests, examinations, medications, and consumables costs (P < 0.05). The median length of stay was 29.5 days for the case group and 16 days for the control group. The average length of stay was increased by 14.5 days because of SSI, according to the Wilcoxon Signed Ranks Test, which showed a statistically significant difference (Z = -4.962, P = 0.000) (Table 4).

Table 4.

Economic losses for each of the postoperative surgical site infections after spinal surgery

Sports event	Case group		Control subjects		Difference		Z	P
	M	Q	M	Q	M	Q
Hospital fees	5516.95	7917.62	3563.24	5057.30	1688.50	3036.15	-5.086	0.000
General medical services	213.99	321.34	100.73	136.47	117.11	211.44	-4.351	0.000
Treatment cost	673.89	1058.56	367.78	537.25	181.02	703.48	-3.479	0.001
Nursing costs	98.28	153.41	45.85	68.11	52.64	85.51	-4.881	0.000
Laboratory costs	671.86	900.20	312.06	469.81	307.16	588.91	-4.556	0.000
Examination costs	487.83	640.40	407.40	572.99	54.25	289.00	-2.026	0.043
Medication costs	460.11	1011.91	316.06	514.70	196.00	548.20	-3.889	0.000
Costs of proprietary Chinese medicines	12.06	24.01	4.88	24.94	0.00	17.54	-0.205	0.838
Surgical blood transfusion costs	1036.70	1447.60	927.50	1192.10	122.01	368.55	-1.787	0.074
Cost of consumables	1158.97	2062.86	727.07	1308.50	162.12	752.10	-2.060	0.039
Other expenses	7.00	10.08	1.54	4.48	5.18	7.42	-4.103	0.000
Days of hospitalization	29.5	36.5	16	21	14.5	21.25	-4.962	0.000

Composition of direct economic losses from SSI in spine patients

As detailed in Table 5, the composition of direct economic losses from SSI varied significantly, ranging from 0.22 to 21.68%. In descending order, these were: consumables at $162.12 (21.68% of total SSI direct economic loss), medication costs at $196 (19.79%), laboratory costs at $307.16 (14.85%), treatment costs at $181.02 (14.57%), surgical blood transfusion costs at $122.01 (6.66%), general medical services at $117.11 (6.61%), examination fees at $54.25 (4.01%), nursing care at $52.64 (2.72%), and other fees at $5.18 (0.24%). The cost for proprietary Chinese medicines was negligible at $0 (0.22%).

Table 5.

Component ratio analysis of direct economic losses from SSIs(%)

Cost category	Aggregate($)	Component ratio(%)
General medical services	5118.26	6.61
Treatment costs	11282.67	14.57
Care costs	2104.76	2.72
Laboratory fees	11499.04	14.85
Inspection costs	3107.86	4.01
Medication costs	15319.36	19.79
Proprietary Chinese medicine costs	-168.17	0.22
Surgical blood transfusion costs	5155.37	6.66
Other costs	184.52	0.24
Consumables costs	16787.82	21.68
Hospitalization costs	77426.58	100

Component ratio = sum of costs/total hospitalization costs

Discussion

SSIs may have adverse consequences for patients, including the need for reoperation, secondary hospitalization, and prolonged antibiotic therapy. Moreover, the extended treatment and care, additional surgical interventions, and longer hospital stays associated with SSIs, along with potential delays in the patient’s return to work, can impose substantial financial burdens. Thus, identifying the risk factors for SSIs and quantifying the direct economic losses associated with them are of great clinical and practical significance. The main findings of this study were that intraoperative bleeding of ≥ 300 mL and the number of days with indwelling drains were significant risk factors for SSIs. Additionally, the presence of co-morbidities, the duration of indwelling urinary catheter use, and the length of time with an indwelling drain were independent risk factors for SSIs. These findings are crucial not only for optimizing surgical and nursing protocols and enhancing patient safety but also for reducing healthcare costs, boosting hospital management efficiency, and alleviating the financial burden on patients. Mitigating the risk of SSIs demands a collaborative approach among healthcare professionals, patients, and healthcare institutions. Healthcare professionals must rigorously adhere to aseptic surgical principles, master surgical techniques, optimize the operating room environment, use antibiotics rationally, and enhance patient education on self-protection. Patients should engage proactively with medical professionals in their treatment and care, and monitor their own recovery. Medical institutions need to enhance oversight and assessment, and continually refine their regulations and operational procedures. The incidence of SSIs after spinal surgery ranges from 0.49% to 16.1%, according to previous studies [2–5]. The current study observed an overall incidence of SSI at a rate of 0.63%, which is consistent with the reported data. A study included 4,166 cases of spinal surgery patients with a 1.6% incidence of SSIs [22]. Mahan et al. reported that the incidence of SSI for non-endoscopic discectomy was 1.2% and 0.001% for endoscopic procedures [23], indicating that SSI rates vary depending on the type of surgery, the surgical approach, and the level of medical care in each location.

During surgery, the serum and tissue concentrations of antimicrobial drugs decrease progressively with increasing blood loss, elevating the risk of SSI. It has been found [24] that intraoperative bleeding ≥ 400 ml is an independent risk factor for SSI. A retrospective analysis of 1,009 patients undergoing spinal surgery [25] showed that perioperative blood loss > 500 ml was associated with SSI. In this study, intraoperative bleeding ≥ 300 ml was a risk factor for SSI, which is consistent with the findings. Differences may arise from larger perioperative blood loss compared to intraoperative losses and variations in surgical techniques and medical care standards affecting blood loss amounts. Therefore, to reduce the risk of SSI, medical personnel should ensure thorough preoperative preparations, minimize tissue damage during surgery, and employ appropriate surgical instruments and hemostatic techniques to control bleeding effectively.

Edmiston et al. [26] noted that the occurrence of SSI after surgery was linked to comorbid underlying conditions, such as diabetes mellitus, coagulation disorders, and congestive heart failure. In addition, Henkelmann et al. [27] identified that the number of comorbidities as a correlate of poor patient prognosis. Edmiston et al. [3] demonstrated that diabetes mellitus, which induces microangiopathy and local tissue ischemia, ultimately delays wound healing, thereby increasing the risk of SSI after spinal surgery [28]. However, this study did not identify diabetes mellitus as a risk factor for SSI, and consistent conclusions were not drawn, possibly due to the small sample size. Furthermore, hypertension has been recognized as a separate risk factor for SSI in a case–control study [24]. Particularly in a hospital specializing in spinal tumor surgery, the incidence of SSI was reported at 20.37% with a mortality rate of 12% [29]. Tumor patients, often weakened by chemotherapy and radiotherapy, are more susceptible to infections at surgical sites due to reduced immunity and bodily functions. Our research revealed that the existence of comorbid underlying conditions is an independent risk factor for SSI. Each extra disease in the case group increases the likelihood of SSI by a factor of 2.529 compared to the control group. Therefore, individuals who have a higher number of comorbid underlying diseases are at a higher risk of developing SSI after surgery.

During the perioperative period, surgeons, anesthesiologists, and nurses utilize catheters to avoid intraoperative contamination, postoperative activity restrictions, and urinary retention. The duration of perioperative indwelling urinary catheterization has been linked to postoperative SSIs, particularly, indwelling urinary catheters lasting longer than 1 day were correlated with SSI in women, with pathogens found in both urine and surgical sites [30]. Núñez-Pereira et al. [31] suggested that urinary catheters during the perioperative period might lead to urinary tract infections and potentially contribute to SSIs. In addition, extended catheterization can impede early postoperative movement, therefore promoting the occurrence of SSIs. This study confirmed that the length of time a urinary catheter remains in place is an independent risk factor for SSI, which supports previous research. Therefore, the catheter should be removed as soon as the patient’s condition permits to minimize the occurrence of SSI. Therefore, removing urinary catheters as soon as clinically feasible is critical to minimize infection risks.

Drainage tubes are routinely utilized post-spinal surgery [32, 33]. Spinal surgery is different from other surgeries in that intraoperative hematoma formation may lead to severe spinal cord injury. Therefore, effective drainage is crucial for preventing SSIs after spinal surgery. However, prolonged drainage may cause local tissue inflammation, and bacteria may reach the surgical incision site through the drain, increasing the risk of SSI. Rao et al. [34] discovered that the length of time that drains are left in place following spinal surgery was a separate factor that increased the chance of developing SSI. They suggested that removing the drains early could reduce the occurrence of SSI. Furthermore, Li et al. [35] found a strong correlation between extended drainage duration and SSI, suggesting that the ideal drainage period should not surpass 48 h. The study found that the length of time that drains were left in place was identified as a separate risk factor for SSI, which is in line with earlier research. Nevertheless, because of the study’s retrospective approach, there is a possibility that there are more unidentified variables that may have influenced the extended duration of drainage. Although anticoagulation therapy is a risk factor for hematoma formation, anticoagulants are typically avoided in patients at low risk for venous thromboembolism (VTE) and those undergoing open spinal surgery to prevent irreversible damage from epidural hematoma compression of the spinal cord [36]. Instead, physical–mechanical prophylaxis such as compression stockings and mechanical lower extremity compression devices are widely used in clinical settings to prevent thrombosis. Consequently, drains should be removed as early as possible based on the patient’s condition to prevent prolonged drainage from facilitating retrograde flow of pathogenic bacteria, thus reducing the risk of SSI.

Research indicates that a variety of pathogenic bacteria, predominantly gram-positive, cause SSIs. Kim et al. [37] in a study of 1,831 cases, identified methicillin-resistant Staphylococcus epidermidis and Staphylococcus aureus as the most common pathogens in SSIs. Zhou et al. [12] in a meta-analysis of 27 studies, noted that Staphylococcus aureus (37.9%) was the most frequent pathogen causing SSI after spinal surgery, followed by Staphylococcus epidermidis (22.7%). In this study, Staphylococcus aureus was the predominant pathogen (42.3%), followed by Staphylococcus epidermidis (23.1%), Enterobacter cloacae (7.7%), and Escherichia coli (7.7%). These findings are not entirely consistent with other studies due to different infection sites involving various tissue depths and locations, potentially exposing them to different microbial environments; inadequate disinfection during the surgical procedure might fail to sterilize surgical instruments and improperly care for the incision post-operation, introducing different causative organisms; and geographical differences in pathogenic bacteria. Therefore, clinically, rational prophylactic use of antimicrobials is essential to control the proliferation of pathogenic bacteria and reduce the risk of SSI.

For spinal surgery, McGirt [9] et al. reported SSI in 292 out of 5,170 patients (5.6%), with an average direct cost of $15,817 per SSI. Atkinson et al. [38] found that the average hospital cost in the SSI group was £12,789 compared to £4,733 in the no SSI group, indicating that costs were 60% higher in the SSI group. In this study, the case group consistently incurred higher costs compared to the control group, with a direct economic loss associated with SSI amounting to $1,688.50 and hospitalization costs 65% higher in the SSI group, which imposed a significant financial burden on patients. the proportion of direct economic loss for SSI patients varied widely, ranging from 0.22 to 21.68%. The highest costs associated with SSI following spinal surgery were for consumables ($162.12 or 21.68%), followed by medications ($196 or 19.79%) and laboratory fees ($307.16 or 14.85%). Possible reasons for these variations include differing economic impacts of SSI across countries and regions. Additionally, this figure only the cost of hospitalization to the patient, not the total direct cost, and does not include costs associated with outpatient antibiotic therapy or non-medical expenditures incurred during hospitalization. This type of economic analysis has policy implications and aids in promoting evidence-based decision-making.

Limitations

There are specific constraints to our investigation. Firstly, this study is retrospective, and the restricted number of patients with SSI may have hindered our capacity to identify correlations and statistical differences in some factors. A multicenter study could help overcome this limitation. Secondly, the limited incidence of tumor cases among SSI patients and the small sample size precludes a detailed analysis of their impact on SSI occurrence. Additionally, certain variables such as the level of surgery and trauma were not included in this study. Finally, this study did not consider indirect costs to patients, which would have led to an underestimation of the total economic loss to SSI patients.

Conclusion

In conclusion, this retrospective study found a 0.63% incidence of SSIs in spine surgery. Intraoperative bleeding of ≥ 300 ml was identified as a risk factor for SSIs; independent risk factors included the number of co-morbidities, the duration of catheterization, and the required duration of an indwelling drain. The median direct economic loss from an SSI was $1,688.50. During surgery, it is critical for medical staff to monitor bleeding closely and implement timely and effective hemostatic measures to minimize bleeding. Based on the patient’s condition, urinary catheters and drains should be removed as soon as feasible, and the duration of indwelling urinary catheters and drains should be minimized to reduce both the incidence of SSI and the economic burden on patients. Future studies should continue to analyze risk factors and economic impacts in patients undergoing spinal surgery through prospective multicenter studies, and should include indirect economic losses in the analysis.

Authors’ contributions

Conceptualization: Q.Z., K.Z., P.T. Data curation: Q.Z., B.D., Y.Z. Formal analysis: Q.Z., K.Z., P.T., X.W. Methodology: A.M., X.W., B.D. Writing original draf: Q.Z., B.D., Y.Z., A.M., X.W., K.Z., P.T. Writing-review & editing: Q.Z., X.W., B.D., A.M., X.W., K.Z., P.T. All authors reviewed the manuscript.

Funding

This work was supported by the Natural Science Foundation of the Xinjiang Uygur Autonomous Region (2022D01C564), Xinjiang Medical University Student Innovation Training Program Project (No. S202310760071) and Xinjiang Uygur Autonomous Region Hospital Management Institute (No. YGYJ2024007).

Data availability

The data of this study are available from the corresponding author upon request.

Declarations

Ethics approval and consent to partcipate

This retrospective study received approval from the Ethics Committee of the Fifth Affiliated Hospital of Xinjiang Medical University (certification number: XYDWFYSk-2022–12), Patients were reviewed by the Ethics Committee of the Fifth Affiliated Hospital of Xinjiang Medical University and certify that the study was performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki. Due to the observational nature of this study, each study hospital waived the requirement for informed consent. All clinical data were anonymized and de-identified before analysis.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.