Enhancing the Unicompartmental Knee Arthroplasty Safety via Finite Element Analysis of Coronary Plane Alignment: A Case Report.

Although Oxford unicompartmental knee arthroplasty is often used to successfully treat patients with knee osteoarthritis isolated at the medial compartment, we present a case of fracture just below the tibial keel caused by either a shift in medial loading position or an increased amount of tibial osteotomy. Finite element analysis was used to determine which factor was more important. First, a 3D-surface model of the patient's tibia and the implant shape were created using computed tomography-Digital Imaging and Communications in Medicine (CT-DICOM) data taken preoperatively. The finite element analysis found that following unicompartmental knee arthroplasty, the cortical stress (normal, 5.8 MPa) on the medial tibial metaphyseal cortex increased as the load point moved medially (3 and 12 mm medially: 7.0 and 10.7 MPa, respectively) but was mild with increased tibial bone resection (2 and 6 mm lower: 6.1 and 6.5 MPa, respectively). Implanting the femoral component more medially than the preoperative plan increases stresses in the medial cortex of the tibia and may cause fractures.

Impact of intrawound vancomycin powder on prevention of surgical site infection after posterior spinal surgery.

OBJECTIVE: Surgical site infection (SSI) after posterior spinal surgery is one of the severe complications that may occur despite administration of prophylactic antibiotics and the use of intraoperative aseptic precautions. The use of intrawound vancomycin powder for SSI prevention is still controversial, with a lack of high-quality and large-scale studies. The purpose of this retrospective study using a propensity score-matched analysis was to clarify whether intrawound vancomycin powder prevents SSI occurrence after spinal surgery. METHODS: The authors analyzed 1261 adult patients who underwent posterior spinal surgery between 2010 and 2018 (mean age 62.3 years; 506 men, 755 women; follow-up period at least 1 year). Baseline and surgical data were assessed. After a preliminary analysis, a propensity score model was established with adjustments for age, sex, type of disease, and previously reported risk factors for SSI. The SSI rates were compared between patients with intrawound vancomycin powder treatment (vancomycin group) and those without (control group). RESULTS: In a preliminary analysis of 1261 unmatched patients (623 patients in the vancomycin group and 638 patients in the control group), there were significant differences between the groups in age (p = 0.041), body mass index (p = 0.013), American Society of Anesthesiologists classification (p < 0.001), malnutrition (p = 0.001), revision status (p < 0.001), use of steroids (p = 0.019), use of anticoagulation (p = 0.033), length of surgery (p = 0.003), estimated blood loss (p < 0.001), and use of instrumentation (p < 0.001). There was no significant difference in SSI rates between the vancomycin and control groups (21 SSIs [3.4%] vs 33 SSIs [5.2%]; OR 0.640, 95% CI 0.368-1.111; p = 0.114). Using a one-to-one propensity score-matched analysis, 444 pairs of patients from the vancomycin and control groups were selected. There was no significant difference in the baseline and surgical data, except for height (p = 0.046), between both groups. The C-statistic for the propensity score model was 0.702. In the score-matched analysis, 12 (2.7%) and 24 (5.4%) patients in the vancomycin and control groups, respectively, developed SSIs (OR 0.486, 95% CI 0.243-0.972; p = 0.041). There were no systemic complications related to the use of vancomycin. CONCLUSIONS: The current study showed that intrawound vancomycin powder was useful in reducing the risk of SSI after posterior spinal surgery by half, without adverse events. Intrawound vancomycin powder use is a safe and effective procedure for SSI prevention.

Does preoperative prognostic nutrition index predict surgical site infection after spine surgery?

PURPOSE: Malnutrition is reported as one of the risk factors for surgical site infection (SSI). The prognostic nutritional index (PNI) is a simple method for nutritional evaluation. However, little is known about the relationship between SSI and the PNI in patients after spine surgery. We aimed to determine independent predictors of SSI after spine surgery. METHODS: We analyzed 1115 patients who underwent spine surgery (369 males, 746 females, mean age 56 years, follow-up period: at least 1 year). Patients were divided into SSI and non-SSI groups. Preoperative risk factors, including PNI (10 × serum albumin [g/dL] + 0.005 × total lymphocyte count [/µL]), were assessed. RESULTS: Postoperatively, 43 patients (3.9%) experienced SSI. Univariate analysis showed that preoperative PNI (48.5 vs 51.7; p < 0.01), revision status (p < 0.05), male sex (p < 0.01), body mass index (BMI) (p < 0.05), and usage of anticoagulant agents (p < 0.05) differed significantly between the SSI and non-SSI groups. Multivariate logistic regression analysis showed that preoperative PNI (odds ratio [OR], 0.94; 95% confidence interval [CI]: 0.90-0.98; p < 0.01), male sex (OR, 2.64; 95% CI: 1.40-4.99; p < 0.01), length of surgery ≥ 180 min (OR, 2.78; 95% CI: 1.30-5.96; p < 0.01), BMI ≥ 30 kg/m2 (OR, 2.89; 95% CI: 1.20-6.97; p < 0.05), and revision status (OR, 2.30; 95% CI: 1.07-4.98; p < 0.05) were independently associated with SSI postoperatively. CONCLUSION: Lower preoperative PNI was found to be a risk factor for SSI after spine surgery. Patients with lower preoperative PNI values should be cautioned about the risk of SSI and provide adequate informed consent.