SLR - May 2021 - Robert G. Stuke

Incidence and Risk Factors for Surgical Site Infection Following Elective Foot and Ankle Surgery: A Retrospective Study

Reference: Meng J, Zhu Y, Li Y, Sun T, Zhang F, Qin S, Zhao H. Incidence and Risk Factors for Surgical Site Infection Following Elective Foot and Ankle Surgery: A Retrospective Study. J Orthop Surg Res. 2020 Oct 1;15(1):449. doi: 10.1186/s13018-020-01972-4. PMID: 33004062; PMCID: PMC7528469.

Level of Evidence: III

Scientific Literature Review 

Reviewed By: Robert G. Stuke, DPM
Residency Program: Long Island Jewish Forest Hills Hospital – Northwell Health, Queens, NY

Podiatric Relevance: Surgical site infection (SSI) represents 31 percent of all hospital-acquired illness and is the most common nosocomial infection. SSI in elective orthopedic surgery is infrequent, but, they can lead to serious consequences, such as bone union-related issues, joint dysfunction, amputation, and even increased mortality. Due to these reasons, this study was to determine the incidence rate of SSI in patients undergoing elective foot and ankle surgery and identify the independent risk factors associated with SSIs.

Methods: This was a retrospective study consisting of 1,201 patients with 1,259 elective foot surgeries between July 2015 and June 2018. Demographics such as age, sex, body mass index (BMI), tobacco use, alcohol consumption, and comorbidities (hypertension, diabetes mellitus (DM), chronic heart disease, chronic pulmonary disease, peripheral vascular disease, and rheumatoid disease) were obtained.  In addition, laboratory biomarkers such as preoperative white blood cell (WBC), neutrophil (NEUT), lymphocyte (LYM), red blood cell (RBC), hemoglobin (HGB), hematocrit (HCT), total protein (TP), albumin (ALB), globulin (GLOB), A/G value, and FBG were collected and compared. SSI was confirmed by documented signs or symptoms of infection in the EMR and bacteria culture results or drug sensitivity available in the microbial culture report. SSI was defined as an incisional infection that occurs within 30 days after surgery if no implant is left in place or within one year if an implant is left in place.

Results: Twenty-six SSIs occurred in 26 patients, representing an overall incidence rate of 2.1 percent. Of them, 16 (incidence rate, 1.3 percent) were superficial and 10 (incidence rate, 0.8 percent) were deep SSI. The median time at which SSIs occurred was 5.5 days after operation, ranging from two to 38 days postoperatively. Most SSIs occurred in the forefoot (22/26, 84.6 percent) and 21 were cultured positive for causative organisms, with Pseudomonas aeruginosa in six cases, MRSA in six, MSSA in four, MRCNS in two, Escherichia coli in two, and Proteus mirabilis in one case. After adjustment for confounding factors, five independent risk factors were identified to be associated with SSI. Delay of each day before operation was associated with 21 percent increased risk of SSI. With reference to normal FBG level (< 6.1mmol/L), the risk of SSI was increased by 17 percent with each increment of 1 mmol/L. Compared to normal ALB level (= 35g/L) or NEUT count (1.8–6.3 × 109/L), the abnormal level was associated with 2.33 times and 1.72 times increased risk of SSI, respectively. The risk of SSI in patients with implantation of allograft or bone substitute was 3.76 times as those with none. 

Conclusions: The incidence rate of SSI following elective foot and ankle surgery was overall low, but relatively high for forefoot surgeries. Factors such as prolonged preoperative stay, allograft or bone substitute, elevated FBG level, ALB level, and NEUT count were identified to be independently associated with SSI. As a result, these factors can be used to help physicians in patient counseling, SSI risk assessment, and stratifying patients, and should be kept in mind through the perioperative period.

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