Surgical site infection (SSI) is one of the most important postoperative complications after craniotomy, which is a major cause of morbidity, length of hospital stay, healthcare costs, and death in rare instances. Although there has been significant progress in neurosurgical practice, perioperative antimicrobial prophylaxis, sterile operative conditions, and wound care, SSIs remain a significant problem in neurosurgical practice globally. The reported rate of SSI following craniotomy has ranged from 1% to 20%, depending on the patient population, the complexity of the surgical procedure, and the quality of the infection-control measures at the institution, as well as on the definition of SSI. Infections can affect the superficial incisional tissues, the deep soft tissues, bone flaps, the meninges, or the intracranial structures. They will require extended antibiotic therapy, additional surgery, and/or removal of the bone flap [1,2]. Patients requiring craniotomy are especially vulnerable to postoperative infections due to the length of the operation, exposure of intracranial structures, placement of foreign substances, the leakage of CSF, and underlying neurological disorders. In addition, the majority of the neurosurgical patient population have other medical comorbidities, like diabetes mellitus, hypertension, chronic kidney disease, malnutrition, obesity, smoking, and immunosuppression, that affect wound healing and vulnerability to infection. Other factors that raise the risk of postoperative SSI include emergency procedures, traumatic brain injury, repeat craniotomy, prolonged intensive care unit (ICU) stay, and mechanical ventilation [3,4]. Advanced age, diabetes mellitus, obesity, smoking, prolonged operative time, cerebrospinal fluid leakage, emergency surgery, contaminated wound, repeat surgery, and a prolonged preoperative hospital stay are significant risk factors for postoperative SSI after craniotomy. But these factors are not equally prevalent across all settings, due to differences in patient populations, surgical techniques, perioperative management, antimicrobial policies, and healthcare system infrastructure. Thus, local epidemiological information is crucial for pinpointing the institution-specific risk factors and for establishing targeted preventive measures [5,6]. Postoperative SSI after craniotomy is not only a significant clinical problem, but also a major economic burden on the healthcare system. The patients who go on to develop SSI often need longer courses of intravenous antibiotic treatment, further imaging tests, repeat surgery, intensive care unit (ICU) admission, and extended hospital stay. Such complications have a great impact on treatment costs, besides postponing neurological rehabilitation and recovery. Furthermore, postoperative infection can also have negative consequences on long-term neurological function and quality of life [7,8]. The identification of patients with an increased risk at an early stage allows the clinician to work towards optimizing modifiable risk factors before the surgery, put in place evidence-based preventive measures, and improve postoperative monitoring. Perioperative antibiotic prophylaxis, careful surgery, control of blood sugar levels, smoking cessation, shortening operative time, minimizing temperature changes, and standardizing infection-prevention packages have shown a positive impact on reducing postoperative infections. However, despite these precautions, SSI persists, and it is necessary to constantly assess contributing factors at individual institutions [9,10]. There is very little information available in Pakistan on the incidence and determinants of postoperative SSI after craniotomy. Earlier published studies are mainly from developed countries, whose patients' characteristics, healthcare resources, and infection-control practices have significant differences from those in developing healthcare settings. Thus, it is crucial to identify local risk factors to establish effective preventive measures and to enhance results in neurosurgery.

Study Objective

To assess the prevalence and identify independent risk factors for postoperative surgical site infection in patients undergoing a craniotomy at a tertiary care hospital

Study Design and Setting

A retrospective cohort study was performed in the Department of Neurosurgery of Ayub Teaching Hospital MTI Abbottabad from 1st January 2023 to 31st December 2025.

Participants

We included 100 consecutive adult patients who had been referred for elective or emergency craniotomy during the study period. Detailed demographic, clinical, operative, and post-operative follow-up data were analyzed in the medical records. The patients were followed up for 30 days after surgery to observe the presence or absence of surgical site infection, based on the standard criteria.

Sample Size Calculation

The sample size was calculated using the WHO sample size calculator, with an expected prevalence of surgical site infections after surgery of 15%, a confidence level of 95%, and an allowable margin of error—eligible patients who were eligible for consecutive enrollment during the study period.

Inclusion Criteria

• Patients aged ≥18 years.
• Patients who had elective or emergency craniotomy.
• Full medical and operative records are available.
• A minimum postoperative follow-up of 30 days.
• Includes cases from the histopathological and traumatic group.

Exclusion Criteria

• Surgery for a wound in the same area of the head.
• Previous wound infection in the head region before surgery.
• Non-surgical bur-hole operations.
• Patients with incomplete patient records.
• Death within 48 hours after surgery.
• Disappeared for postoperative follow-up.

Diagnostic & Management Strategy

Postoperative SSI was diagnosed based on the Centers for Disease Control and Prevention (CDC) definition. Patients were given conventional antibiotic prophylaxis, routine wound treatment, and treatment as per the standard practice, as appropriate, such as culture-based antibiotic therapy and surgical debridement where necessary.

Statistical Analysis

SPSS 27.0 was used to analyze the data. Data for continuous variables were presented as mean ± SD, and for categorical variables as frequencies and percentages. Significant predictors were identified with the chi-square test, independent t-test, and multivariable logistic regression. A p-value < 0.05 was defined as statistically significant

A total of 100 patients underwent craniotomy during the study period. The mean age was 48.7 ± 15.3 years, with 61 (61%) males and 39 (39%) females. Postoperative surgical site infection developed in 18 patients (18%), whereas 82 patients (82%) had an uncomplicated postoperative course. Patients with SSI were significantly older than those without infection (56.2 ± 13.1 vs. 47.1 ± 15.2 years; p=0.018). Diabetes mellitus was present in 6 (33.3%) patients with SSI compared with 9 (11.0%) patients without SSI (p=0.011). Operative duration exceeding four hours occurred in 13 (72.2%) infected patients and 29 (35.4%) non-infected patients (p=0.004). Emergency craniotomy was performed in 9 (50.0%) patients with SSI compared with 18 (22.0%) patients without SSI (p=0.021). Smoking was significantly associated with postoperative infection (44.4% vs. 19.5%; p=0.028). Multivariable logistic regression identified prolonged operative duration (adjusted OR=3.42; 95% CI: 1.28–9.14; p=0.014) and diabetes mellitus (adjusted OR=2.96; 95% CI: 1.07–8.17; p=0.036) as independent predictors of SSI. No statistically significant association was observed between patient sex and postoperative infection (p=0.462).

Table 1. Baseline Demographic and Clinical Characteristics of the Study Population (N = 100)

Values are presented as mean ± standard deviation or frequency (%). SSI = Surgical Site Infection.

Table 2. Comparison of Patients with and Without Surgical Site Infection

Continuous variables are expressed as mean ± SD, whereas categorical variables are presented as frequency (%). P-values were calculated using the independent t-test or Chi-square test as appropriate. Statistical significance was set at p<0.05.

Table 3. Multivariable Logistic Regression Analysis of Risk Factors for Postoperative Surgical Site Infection

Multivariable logistic regression identified independent predictors of postoperative surgical site infection. OR = Odds Ratio; CI = Confidence Interval. Variables with p<0.05 were considered statistically significant.

Table 4. Clinical Outcomes of Patients with Surgical Site Infection (n = 18)

Clinical outcomes among patients who developed postoperative surgical site infection following craniotomy. Values are expressed as frequencies (%) or means ± standard deviations.

This present retrospective cohort study aimed to assess the risk factors for postoperative surgical site infection (SSI) in 100 patients who underwent craniotomy. The overall incidence of SSI was 18%, consistent with the incidence rate reported in recent literature in neurosurgery, which typically ranges between 5% and 20% depending on the patient characteristics, the complexity of surgery, the surveillance system, and the hospital infection-control program [11,12]. Our incidence is slightly lower than in some developed healthcare systems, but within the international range, and could be attributed to patient profiles, emergency surgical workload, or the resources available in the healthcare system. In the current study, increasing age was significantly correlated with PS- SSI. Patients who were diagnosed with SSI were significantly older than those without infection (56.2 ± 13.1 vs. 47.1 ± 15.2 years; p=0.018). Advanced age has consistently been identified as an important risk factor, as elderly patients are likely to have weaker immune function, multiple comorbidities, lesser tissue repair ability, and poorer nutritional status. Systematic reviews and multicenter studies have also recently shown that age is a risk factor for postoperative infection after neurosurgery [13,14]. One of the most important independent risk factors for the development of SSI in our cohort was diabetes mellitus. Nearly three times more of the patients with diabetes were infected (adjusted OR=2.96, p=0.036). Hyperglycemia affects neutrophils, collagen formation, angiogenesis, and wound healing, leading to greater susceptibility to postoperative infection. In recent years, diabetes mellitus has also been shown to be a major independent risk factor for post-craniotomy SSI in meta-analyses and observational studies conducted in the period from 2023 to 2025 [15,16]. The other independent predictor of SSI in the present study was the length of the operation (>4 hours, adjusted OR 3.42, p=0.014). A longer procedure allows for more time for the environment to contaminate surgical wounds, more surgical tissue manipulation, and often more technically complex procedures. These findings have been consistently reported in recent systematic reviews, such as the 2013 study, which showed that operative time is one of the most reproducible predictors of postoperative neurosurgical infections [17]. The results confirm the need to plan surgery efficiently and to avoid any surgical delay when it is not indicated. Univariate analysis found that emergency craniotomy was significantly associated with postoperative SSI. Traumatic brain injury, intracranial bleed, contaminated wounds, poor preoperative optimization, and limited preparation time are common aspects of emergency surgery and can lead to a higher risk for infection [18]. After multivariable adjustment, emergency surgery was no longer an independent predictor, but this is consistent with recent cohort studies that showed emergency neurosurgical surgery was associated with a higher crude rate of SSI compared with elective surgery [19]. Other factors that had a significant association with SSI in our study were smoking. Smoking impairs tissue oxygenation, microvascular circulation, collagen synthesis, and immune function, thereby slowing wound healing. More recently, several studies have also shown that smoking leads to wound complications and surgical site infections after major neurosurgical procedures [20]. This study demonstrates the importance of smoking cessation programs before surgery and interventions that optimize patients' perioperative care. No statistically significant difference was found between postoperative SSI and patient sex, consistent with several recent reports that found that sex is not an independent factor for postoperative infection after controlling for other clinical factors. Rather, the patient's comorbidities and operative factors seem to play a more important role in the risk of infection.

Limitations

The retrospective design of this study and the small number of participants may limit the generalizability of the results. The selection bias and incompleteness of documentation, inherent with retrospective data collection, could not be avoided. Furthermore, microbiological profiles, antimicrobial resistance patterns, and long-term patient outcomes were not assessed.

Surgical site infection is a major complication after craniotomy. Risk factors for increased infection included advanced age, diabetes mellitus, prolonged operative time, emergency surgery, and smoking. Proper risk stratification, to optimize comorbidities and to follow evidence-based perioperative infection prevention guidelines, could have a positive effect on the outcomes of neurosurgical procedures, as well as the incidence of SSIs.

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