Introduction
Surgical site infection (SSI) is an adverse complication of orthopedic surgery and can increase the risk of readmission [
1,
2]. Moreover, SSI often caused poor prognosis, decreased quality of life and the possibility of reoperation [
3,
4]. It is well known that HIV patients are more likely to develop SSI than those who are not infected with HIV due to their dramatically decreased CD4 cell count and weak immune resistance [
5]. With the extension of HIV infection time, the probability of opportunistic infection increases greatly, and postoperative orthopedic incision is prone to infection [
6].
In clinical orthopedic surgery, internal fixation and implant devices are often used. Due to the body’s autoimmunity rejection of foreign objects, the chance of postoperative wound infection is greatly increased [
7]. Internal fixation and implant devices are kept in the body for a long time, creating space and attachments for the growth of pathogens. Therefore, not only does the incidence of SSI increase in the early stage of orthopedic surgery, but it also increases the risk of infection in the later stage. If the internal fixation and implant devices become infected, the body must be treated with antibiotics for a long time, and the internal fixation and implant devices should be removed or replaced as soon as possible. This will greatly increase the medical costs of patients [
8]. Currently, there are few quantitative studies and prediction models which show that HIV virus and reduced CD4 count increase the risk of infection with internal fixation and implant devices during orthopedic surgery [
9,
10]. According to WHO guidelines on infection prevention and control, penicillin should be used for prevention as soon as 1 hour after orthopedic surgery, and the duration should not exceed 24 h [
11]. However, clinicians generally expect the incidence of postoperative SSI to be less than 2% [
12].
Although there are currently surgical guidelines for internal fixation and implant devices, these are based only on data from non-HIV patients. Specific orthopedic guidelines for HIV patients do not yet exist. Therefore, it is necessary for orthopedic surgeons in hospitals with infectious diseases to formulate corresponding operational guidelines. The purpose of this study was to develop a Nomogram prediction model for the incidence of SSI in patients with HIV who underwent orthopedic internal fixation and implant surgery.
Discussion
In this study, we sought to identify the independent risk factors in adult patients susceptible to SSI after instrumented fusion surgery for orthopedic diseases. We analyzed the clinical data of 101 patients who underwent orthopedic surgery in Beijing Ditan Hospital from April 20 to August 2019. According to whether patients had SSI, they were divided into two groups. Preoperative CD4 T cells, presence or absence of opportunistic infection, and organ dysfunction were used to identify whether there was SSI in the patients [
16].
According to the results, SSI is mainly related to factors such as basic disease, operation time and CD4, CRP, ESR, PCT, and D-dimmer. Multivariate logistic regression analysis showed that risk factors indicating overall postoperative SSI included CD4 < 430.75/ul, ESR > 17.46, and PCT > 0.22. The scoring model was as follows:Logit(SSI) = − 2.63589–0.00314*CD4 < 430.75/ul = 1) + 0.04695*(ESR < 17.46 = 1) + 2.93694*(PCT < 0.22 = 1). The model consisting of risk factors might be used to accurately assess whether a patient has SSI.
The results of this study were slightly different from the results reported in the current literature. Firstly, the subjects in the former study [
18] were all a type of incision, but the results of this study did not include the relevant factors of the incision category. Moreover, targeted application of nutritional support treatment before surgery, so that patients better tolerate surgery, so albumin and hemoglobin have not become a risk factor affecting surgical site infection [
19]. Pay attention to perioperative nutritional support and immune reconstitution in HIV-positive patients, correct treatment of hypoproteinemia and anemia, and infusion of plasma or suspended red blood cells if necessary [
19]. Older patients should be paid more attention to the adjustment of this situation. The results of this study showed that the SSI rate was 14.85%, further confirming the significance of standardized treatment during perioperative period.
The CD4+ T count were significantly associated with the incidence of SSI in patients [
20]. Reported in the literature, CD4 T lymphocyte count< 200/ul and viral load> 500,000 copies/ul, the incidence of postoperative incision infection wound would increase [
21]. Therefore, in order to prevent surgical site infection, it is necessary to control the patient’s CD4 count and improve the patient’s immunity status [
22]. At the same time, apply clinical classification of HIV System, to assess the safety of surgery, for patients with CD4 T lymphocyte count higher than grade 2, careful consideration of surgery, it is best to adjust the CD4 T lymphocyte count to a higher level after elective surgery, it is best to improve the perioperative adjuvant treatment after elective surgery [
23].
However, the choice of whether to operate and the timing of surgery cannot be completely dependent on the CD4 T count, and it is necessary to determine the tolerance to surgery in combination with the patient’s general condition, such as ESR and PCT.
The ESR level also affected the incidence of surgical site infections in orthopedic patients with HIV-positive patients. HIV patients have low or even reduced immunity and a higher risk of opportunistic infections [
24]. More and more complex internal fixations were likely to cause infection of the incision, and the disturbance to the physiological function of the body is also large, which could active the inflammatory system [
25]. When the acute inflammation occurred, blood acutephase reactant increased rapidly, including α-antirypsin, α2-mactoglobulin, C reactive protein, haptoglobin, transferrin, fibrinogen, etc. [
26]. The main reason is that the above components, which were released increasingly, could promote the rouley-like aggregation of red blood cells to a greater or lesser extent [
27]. The rapid increase of ESR could be seen in 2–3 days after the occurrence of inflammation. Therefore, under the premise of following the basic principles of orthopedic surgery, surgery should use precise incision, fixation tendencies, such as the selection of simple and effective fixed equipment. The ESR level should be detected timely to estimate the incidence of SSI.
PCT is a protein, which increased in the SSI patients (OR = 220.746,
P < 0.05). Its levels in the plasma rose in severe bacterial, fungal and parasitic infections as well as sepsis [
28]. Bacterial endotoxin played an important role in the induction process [
29]. PCT was a parameter for the diagnosis and monitoring of bacterial inflammatory disease infections. Elevated PCT levels occurred in severe shock, systemic inflammatory response syndrome and multiple organ dysfunction syndrome [
29]. PCT was closely related to the occurrence and process of severe bacterial and septicemic infections, and could accurately reflect whether the source of infection causing lesions (such as peritonitis) has been eradicated [
30]. Daily monitoring of PCT concentrations provided a reliable evaluation of treatment outcomes. PCT might be used to monitor surgical trauma or compound trauma.
The nomogram could be used to predict the risk of HIV positive patients and decided whether to undergo surgical treatment and preoperative interventions. The nomogram model helped doctors in treatment decisions. Compared with traditional tools (such as the NHSN index), the nomogram established in this study was more suitable for the assessment of infection risk of HIV positive patients after orthopedic surgery. Limited by the nature of the sample, this study was suitable for risk assessment of HIV positive patients after orthopedic surgery. In follow-up studies, we would include more samples and extend it to other populations.
However, there were some defects in the research. No a priori threshold was pre-specified, this might lead to a bias in the interpretation of the tests and generalisability of the results. Due to the nature of the sample, this study had certain limitations. In follow-up research, we would add some of the most common descriptive information to enhance the generality of the results. In a short period of time, no more samples could be collected, so in follow-up research, we would conduct external verification of the nomogram. The optimal cut-off point was calculated by Youden’s index method. And we would conduct external verification and include more indicators in follow-up research.
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