Risk factors for surgical site infection after percutaneous endoscopic lumbar discectomy

Abstract

The objective of this study was to investigate the risk factors associated with surgical site infection (SSI) after percutaneous endoscopic lumbar discectomy (PELD) in patients with lumbar disc herniation (LDH). A retrospective analysis was performed on a cohort of 335 patients who underwent PELD between January 2016 and January 2023. Data were derived from the Hospital Information System (HIS), and a comprehensive statistical assessment was performed using IBM SPSS Statistics version 25.0. Both univariate and multivariate logistic regression analyses assessed a range of risk determinants, such as age, body mass index (BMI), comorbidities, laboratory test parameters and surgery‐related variables. The incidence of SSI after PELD was 2.7% (9/335). Univariate analysis highlighted BMI, diabetes mellitus, long‐term corticosteroid consumption, surgical time and cerebrospinal fluid leakage as significant predictors of SSI. Multivariate logistic regression identified BMI, diabetes mellitus, long‐term corticosteroid consumption, surgical time and cerebrospinal fluid leakage as significant risk factors for SSI after PELD. High BMI, diabetes mellitus, long‐term corticosteroid consumption, long surgical time and postoperative cerebrospinal fluid leakage are predisposing factors for SSI in patients undergoing PELD. Precise interventions focused on such risk components, including careful preoperative assessment and strategic postoperative care, are essential to reduce the incidence of SSI and improve surgical efficacy.

Abbreviations

ALB

albumin

ASA

American Society of Anesthesiologists

BMI

body mass index

CHD

coronary heart disease

COD

conventional open discectomy

Hb

haemoglobin

HIS

hospital information system

K—S

Kolmogorov–Smirnov

LDH

lumbar disc herniation

MD

microdiscectomy

MED

microendoscopic discectomy

PELD

percutaneous endoscopic lumbar discectomy

PETD

percutaneous endoscopic transforaminal discectomy

SSI

surgical site infection

VAS

visual analogue scale

1. INTRODUCTION

Lumbar disc herniation (LDH) is the most common degenerative disease of the spine, which is characterised by persistent or recurrent radicular pain and positive signs of nerve root tension. ¹ Its incidence is increasing year by year, with a prevalence of up to 7.62% in China. ² Although the pathogenesis is unclear, it is associated with a variety of factors, including trauma, genetic factors, developmental deficiencies and bad habits. ³ Surgery is often required when standard conservative treatment fails or the condition worsens.

With the development of surgical techniques and medical devices, the surgical approaches for LDH include conventional open discectomy (COD), microdiscectomy (MD), microendoscopic discectomy (MED) and percutaneous endoscopic lumbar discectomy (PELD). The potential advantages of MD over COD are less intraoperative bleeding, shorter hospital stay, lower risk of surgical site infection (SSI), earlier return to work and no association with an increased rate of perioperative complications. ⁴ , ⁵ Compared with MED and MD, percutaneous endoscopic transforaminal discectomy (PETD) is associated with faster recovery and better clinical outcomes. ⁶ Some studies have shown that the recurrence rate of PELD is similar to that of COD or MED. ⁷ , ⁸ , ⁹ However, the reoperation rate of PELD has also been reported to be higher than that of COD. ¹⁰ Nevertheless, PELD is still widely used by many surgeons for patients with LDH.

Although PELD is considered a mainstream technique for the treatment of LDH, it has various risks and complications of its own. ¹¹ , ¹² Among them, infection (wound infection or deep infection) is a thorny issue for orthopaedic surgeons. SSI defined as an infection that occurs at or near the surgical incision site within 30 days of surgery can have serious consequences, including prolonged hospital stays, repeat surgery, prolonged morbidity and even death. ¹³ , ¹⁴ Previous studies have shown that the occurrence of SSI after orthopaedic‐related surgery is a multifactorial event influenced by a variety of factors. ¹⁵ , ¹⁶ Although there is a large body of literature on the subject, it often leads to inconsistent conclusions and a lack of consensus in identifying these risk factors. ¹⁷ , ¹⁸ This discrepancy in the literature suggests an urgent need for more comprehensive studies. The aim of these studies is not only to identify the main risk factors but also to understand their interactions in order to optimise prevention and treatment strategies. Currently, there are relatively few reports on SSI after PELD. Therefore, the aim of this study was to delve into the risk factors for SSI, especially for LDH patients undergoing PELD.

2. MATERIALS AND METHODS

2.1. Patients

This study retrospectively analysed 335 patients with LDH who underwent PELD between January 2016 and January 2023 at our hospital. The inclusion criteria were as follows: (1) failure of conservative treatment for more than 6 months and request for surgery; (2) 18 years of age or older and (3) written informed consent from the patient and his/her family before surgery. The exclusion criteria were as follows: (1) patients with a history of lumbar surgery or the presence of lumbar malignancy, instability and infection; (2) psychiatric illnesses or disorders of consciousness; (3) less than 3 months of follow‐up and (4) incomplete medical record data.

2.2. Surgical procedure

All patients were operated by the same surgical team under nerve block anaesthesia. The surgical approach used was PETD. The surgical procedure included determination of puncture path, sterilisation, puncture, foraminoplasty, placement of the working cannula and decompression of the nerve root. ¹² Antibiotics were not routinely used throughout the perioperative period. Stitches were removed at 2 weeks according to wound healing.

2.3. Data collection

Data were obtained by accessing the Hospital Information System (HIS). Information on all patients was collected according to the inclusion and exclusion criteria mentioned above. The data included: (1) general baseline information such as age, gender, height, weight, smoking and alcohol consumption, comorbidities, history of corticosteroid use and Visual Analogue Scale (VAS); (2) surgery‐related variables such as responsible level, blood loss, American Society of Anaesthesiologists (ASA), surgical time and incidence of cerebrospinal fluid leakage; (3) laboratory test parameters such as preoperative haemoglobin and albumin (ALB). Preoperative haemoglobin was mainly used to assess whether the patient was comorbidly anaemic. ¹⁹ The occurrence of infection was determined from hospital records, including clinical symptoms, signs and laboratory blood test results. The patients who developed wound infection were set up as the case group and the remaining patients were set up as the control group.

2.4. Statistical analysis

Statistical analyses for this study were performed strictly using IBM SPSS Statistics, version 25.0 (SPSS Chicago, IL, USA). First, normality of continuous variables was assessed using the Kolmogorov–Smirnov (K–S) test. For variables obeying or approximating a normal distribution, the mean ± standard deviation (x ± s) was used. For non‐normally distributed data, appropriate non‐parametric tests were used. Secondly, for comparison of two groups of patients, independent‐samples t‐test was used for continuous variables. In the case of categorical variables, the chi‐square (χ ²) test was used. Finally, complex multivariate analyses were performed using multiple logistic regression models to identify independent risk factors for SSI. p < 0.05 was considered to indicate statistical significance.

3. RESULTS

3.1. Univariate analysis

The incidence of SSI after PELD in LDH patients was 2.7%. The univariate analysis of risk factors for SSI revealed significant differences between the case and control groups. Differences between the two groups were statistically significant (p < 0.05) in terms of BMI, diabetes mellitus, long‐term use of corticosteroids, surgical time and cerebrospinal fluid leakage (p < 0.05). By contrast, age, gender, alcohol consumption, smoking, VAS, preoperative ALB, ASA, blood loss and responsible level had no statistically significant effect (p > 0.05) (Table 1).

TABLE 1.

Univariate analysis of risk factors for SSI of percutaneous endoscopic lumbar discectomy.

Variable	Case group	Control group	x 2/t	p‐Value
Age, years	48.1 ± 17.6	53.5 ± 13.1	−1.123	0.262
Gender, n			2.541	0.111
Male	6	131
Female	3	195
BMI, kg/m2	25.0 ± 1.9	20.5 ± 2.1	6.370	<0.001
Hypertension	1	25	0.145	0.703
Diabetes mellitus	4	36	9.293	0.002
CHD	0	19	0.556	0.456
Long‐term use of corticosteroids	3	20	10.132	0.001
Smoke	4	63	3.454	0.063
Alcohol consumption	2	79	0.019	0.889
VAS	7.2 ± 1.3	7.7 ± 0.9	−1.535	0.125
Preoperative anaemia	2	21	3.411	0.065
Preoperative ALB, g/L	34.5 ± 1.4	36.8 ± 4.1	−1.732	0.084
ASA classification	2.0 ± 0.5	1.9 ± 0.5	0.504	0.615
Surgical time, min	137.0 ± 13.0	87.2 ± 25.1	5.942	<0.001
Blood loss, mL	37.8 ± 11.8	32.5 ± 10.2	1.524	0.129
Responsible level			0.407	0.816
L3/4	1	35
L4/5	4	83
L5/S1	4	208
Cerebrospinal fluid leakage	3	14	15.332	<0.001
Total	9	326	‐	‐

Abbreviations: ALB, albumin; ASA, American Society of Anesthesiologists; BMI, body mass index; CHD, coronary heart disease; SSI, surgical site infection; VAS, visual analogue scale.

3.2. Multivariate logistic regression analysis

Table 2 presented a multivariate logistic regression analysis focused on identifying significant determinants of SSI after PELD in patients with LDH. The analysis showed that BMI, diabetes mellitus, long‐term use of corticosteroids, surgical time and cerebrospinal fluid leakage were significant predictors with p‐values of less than 0.05.

TABLE 2.

Multivariate logistic regression analysis.

Risk factors	B value	Standard error	Wald	OR	95% CI	p‐Value
BMI	−4.971	1.458	11.632	0.007	0.000 ~ 0.121	0.001
Diabetes mellitus	−3.587	1.306	7.550	0.028	0.002 ~ 0.358	0.006
Long‐term use of corticosteroids	−3.815	1.672	5.208	0.022	0.001 ~ 0.584	0.022
Surgical time	−3.905	1.265	9.538	0.020	0.002 ~ 0.240	0.002
Cerebrospinal fluid leakage	−3.031	1.360	4.968	0.048	0.003 ~ 0.694	0.026

4. DISCUSSION

Although PELD has been proven to be a safe, effective and feasible minimally invasive surgical technique, ²⁰ it is still not possible to completely avoid the complication of wound infection. In our study, the incidence of SSI was 2.7%. This result suggests that spine surgeons should pay attention to the perioperative management of minimally invasive spine surgery to reduce the incidence of SSI. Another important finding of our study was that BMI, diabetes mellitus, long‐term use of corticosteroids, surgical time and cerebrospinal fluid leakage are independent risk factors for SSI. Unlike previous studies, we included a wider range of predictors, resulting in a more complete risk profile. Clinically, these findings provide a valuable reference value for preoperative planning, intraoperative techniques and postoperative care, helping healthcare professionals, including spine surgeons and wound therapists, to stratify risk and develop individualised intervention strategies to potentially reduce the incidence of postoperative wound infection.

The idea that obesity is a risk factor for the development of SSI has been validated by relevant experts. ²¹ , ²² , ²³ , ²⁴ However, the exact biological mechanisms linking BMI and SSI remain to be fully elucidated. Obese patients have a thick subcutaneous adipose layer, and adipose tissue promotes the production of inflammatory cytokines, which in turn leads to insulin resistance and indirectly to elevated blood glucose, eventually increasing the risk of infection. ²⁵ This metabolic imbalance includes dysregulated cytokine production and a chronic low‐grade inflammatory state. ²⁶ Our study found similar findings that high BMI (higher than 24 kg/m²) can significantly increase the occurrence of SSI. Therefore, in order to reduce the incidence of postoperative SSI in obese patients, it is important to develop a preoperative fat reduction programme that is tailored to the health of the individual. For obese patients undergoing elective PELD treatment, especially those with high fat content, dietary guidance and exercise for fat reduction in authorised specialties are recommended before surgery.

Numerous systematic reviews and meta‐analyses describe the link between diabetes and SSI. ²⁷ , ²⁸ , ²⁹ Elevated blood glucose levels not only inhibit natural wound healing mechanisms by reducing collagen synthesis and disrupting angiogenesis, but also create an environment conducive to bacterial proliferation. ³⁰ Pennington et al. ²⁷ demonstrated that persistent postoperative hyperglycaemia is a risk factor for deep wound infection after spinal surgery. Maragakis et al. ³¹ reported that the incidence of SSI was significantly lower in the presence of a glucose level of less than 11.1 mmol/L, and when blood glucose was maintained at 5.5–16.7 mmol/L, the incidence of SSI decreased with lower blood glucose values. Therefore, spine surgeons need to work with endocrinologists to maintain patients' blood glucose in the normal range, which is particularly important for reducing the incidence of SSI after spine surgery. In addition, our study found that long‐term corticosteroid consumption can increase the occurrence of SSI. Chronic steroid administration has a wide range of negative effects on body systems, including immunosuppression. Newton et al. found that long‐term oral corticosteroid therapy was associated with an increased risk of postoperative infections in patients undergoing 4‐corner fusion. ³² Long‐term steroid use weakens various components of innate and adaptive immunity, altering metabolism and increasing susceptibility to infection. ³³

Our study found that prolonged surgical time can increase the occurrence of SSI. Increased surgical time, on the one hand, leads to prolonged exposure of the surgical area to the outside world, which increases the risk of contamination; on the other hand, it can also lead to an increase in surgical trauma and haemorrhage. Schoenfeld et al. ³⁴ reported that surgical time greater than 309 min significantly increases the risk of SSI. Therefore, preoperative prediction of surgical time is important for the prevention of SSI. Adequate preoperative preparation and surgical planning can reduce surgical time, thus indirectly reducing the incidence of SSI. Cerebrospinal fluid leakage is a possible complication of PELD procedure. In our study, it was an independent risk factor for SSI, which is consistent with other study. ³⁵ Apparently, cerebrospinal fluid leakage is a relative headache for clinicians, mainly because of its secondary complication such as infection. ³⁶ This may be related to the persistent wound exudation after cerebrospinal fluid occurrence, which in turn leads to secondary infection. Therefore, spinal surgeons ensure delicate intraoperative manoeuvres to avoid damage to the dura mater. In the event of cerebrospinal fluid leakage, methods such as cerebrospinal fluid diversion by lumbar drain ³⁷ can be used in co‐operation with neurosurgeons to reduce the incidence of SSI.

This study has several limitations. Firstly, this study was a single‐centre retrospective study and lacked randomised controls. Second, the study population may not be fully representative, limiting the generalisability of the findings. Further, despite the large amount of data collected, some factors such as socioeconomic status and postoperative treatment adherence were not included in this study, which may introduce bias in the results. Finally, the short observation period may have missed some positive cases. A prospective multicentre study with a large sample size is needed in the future to confirm our findings.

5. CONCLUSION

In patients undergoing percutaneous endoscopic lumbar discectomy, there is still a risk of postoperative wound infection. High BMI, diabetes mellitus, long‐term corticosteroid consumption, long surgical time and cerebrospinal fluid leakage are independent risk factors for SSI. Appropriate interventions targeting these risk factors may reduce the incidence of such infections. Our findings emphasise integrated perioperative management, promoting individualised patient risk assessment to improve surgical outcomes.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflicts of interest.

Xiao B, Chen T, Zhao Q, et al. Risk factors for surgical site infection after percutaneous endoscopic lumbar discectomy. Int Wound J. 2024;21(4):e14605. doi: 10.1111/iwj.14605

DATA AVAILABILITY STATEMENT

The datasets generated during the current study are available from the corresponding author on reasonable request.