Effect of Hemostatic Material on Sternal Healing After Cardiac Surgery

Improved early risk stratification of deep sternal wound infection risk after coronary artery bypass grafting

BACKGROUND

Deep sternal wound infection (DSWI) following open heart surgery is associated with excessive morbidity and mortality. Contemporary DSWI risk prediction models aim at identifying high-risk patients with varying complexity and performance characteristics. We aimed to optimize the DSWI risk factor set and to identify additional risk factors for early postoperative detection of patients prone to DSWI.

METHODS

Single-centre retrospective analysis of patients with isolated multivessel coronary artery disease undergoing myocardial revascularization at Paracelsus Medical University Nuremberg between 2007 and 2022 was performed to identify risk factors for DSWI. Three data sets were created to examine preoperative, intraoperative, and early postoperative parameters, constituting the "Baseline", the "Improved Baseline" and the "Extended" models. The "Extended" data set included risk factors that had not been analysed before. Univariable and stepwise forward multiple logistic regression analyses were performed for each respective set of variables.

RESULTS

From 5221 patients, 179 (3.4%) developed DSWI. The "Extended" model performed best, with the area under the curve (AUC) of 0.80, 95%-CI: [0.76, 0.83]. Pleural effusion requiring intervention, postoperative delirium, preoperative hospital stay > 24 h, and the use of fibrin sealant were new independent predictors of DSWI in addition to age, Diabetes Mellitus on insulin, Body Mass Index, peripheral artery disease, mediastinal re-exploration, bilateral internal mammary harvesting, acute kidney injury and blood transfusions.

CONCLUSIONS

The "Extended" regression model with the short-term postoperative complications significantly improved DSWI risk discrimination after surgical revascularization. Short preoperative stay, prevention of postoperative delirium, protocols reducing the need for evacuation of effusion and restrictive use of fibrin sealant for sternal closure facilitate DSWI reduction.

TRIAL REGISTRATION

The registered retrospective study was registered at the study centre and approved by the Institutional Review Board of Paracelsus Medical University Nuremberg (IRB-2019-005).

Morphological, cytotoxicity, and coagulation assessments of perlite as a new hemostatic biomaterial

Hemorrhage control is vital for clinical outcomes after surgical treatment and pre-hospital trauma injuries. Numerous biomaterials have been investigated to control surgical and traumatic bleeding. In this study, for the first time, perlite was introduced as an aluminosilicate biomaterial and compared with other ceramics such as kaolin and bentonite in terms of morphology, cytotoxicity, mutagenicity, and hemostatic evaluations. Cellular studies showed that perlite has excellent viability, good cell adhesion, and high anti-mutagenicity. Coagulation results demonstrated that the shortest clotting time (140 seconds with a concentration of 50 mg mL^-1) was obtained for perlite samples compared to other samples. Therefore, perlite seems most efficient as a biocompatible ceramic for hemorrhage control and other biomaterial designs.

Computed Tomography Imaging Assessment of the Effect of Vancomycin Paste on Poststernotomy Healing

Purpose

To assess vancomycin paste effect on poststernotomy healing in high-risk coronary artery bypass grafting (CABG) patients compared to bone wax using the 6-point computed tomography (CT) score. Additionally assessed the reliability of this score and its relationship to the occurrence of infection.

Patients and Methods

A prospective comparative analysis included 126 high-risk CABG patients. The patients were randomly assigned into bone wax or vancomycin paste for sternal haemostasis. All patients were submitted to CT examinations 6-months postoperative. Two radiologists independently reviewed all CT scans to assess sternal healing using the 6-point CT score. The CT healing score of the two groups was compared. The kappa statistics were used to calculate the inter-reader agreement (IRA) of the 6-point CT score.

Results

The final analysis included 61 patients in each group. The main CT score for sternal healing was 3.9±0.4 in the vancomycin group and 3.3±0.8 in the bone wax group. Patients in the vancomycin group had a higher statistically significant improvement in CT healing score than those in the bone wax group (p<0.001). There was no statistically significant relationship (p = 0.79) between the occurrence of infection and the 6-point CT score in the vancomycin group. The overall IRA of the 6-point CT score was good in two groups (κ = 0.79 in the vancomycin group and = 0.78 in the bone wax group).

Conclusion

Vancomycin paste had a better CT healing score and can be used as a sternal haemostatic material instead of bone wax. The 6-point CT healing score is a reliable diagnostic tool for evaluating sternal healing.

Efficacy and Safety of Bioabsorbable Bone Hemostatic Agent in Total Knee Arthroplasty: A Prospective Randomized Controlled Trial

Although a bioabsorbable bone hemostatic agent (BBHA) was developed approximately 20 years ago to overcome the shortcomings of conventional bone wax, its bleeding control capacity has not yet been studied. This study was aimed at investigating the efficacy and safety of BBHA in total knee arthroplasty (TKA). Sixty-two patients who underwent unilateral primary TKA for knee osteoarthritis were included and randomized to the control or BBHA group. Before releasing the tourniquet, BBHA was applied on the bone-cut surface that was not covered by implants. The primary variable was the drainage volume during the postoperative period. The secondary outcomes were total estimated blood loss (EBL), hemoglobin level, hematocrit level, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, range of motion (ROM), pain visual analog scale (VAS) score, and rate of complications. There were no significant differences in drainage volume or EBL between the 2 groups. Hemoglobin and hematocrit levels were higher in the BBHA group during the 4-week postoperative period; however, the intergroup differences were not significant. The ESR, CRP, ROM, and pain VAS scores in the BBHA group were not significantly different from the corresponding values in the control group. No specific complications were observed. Although BBHA was found to be safe without complications, it did not decrease bleeding after TKA in general cases. Further studies are necessary to evaluate the efficacy of BBHA in patients with coagulation problems.

Recent developments in controlling sternal wound infection after cardiac surgery and measures to enhance sternal healing

One of the major risks of cardiac surgery is the occurrence of infection at the sternal wound site. Sternal wound infections are primarily classified into superficial infection and deep sternal wound infection or mediastinitis. A patient is diagnosed with mediastinitis if microorganisms are present in their mediastinal tissue/fluid or with the observation of sternal wound infection during operation and with characteristic symptoms including chest pain, fever, and purulent drainage from the mediastinum. It is usually caused by Staphylococcal organisms in 75.8% of cases and the rest is caused by gram-negative bacteria. Currently, in cardiac surgery, hemostasis is achieved using electrocautery and bone wax, and the sternum is closed using wire cerclage. Several studies show that bone wax can act as a nidus for initiation of infection and the oozing blood and hematoma at the site can promote the growth of infectious organisms. Many research groups have developed different types of biomaterials and reported on the prevention of infection and healing of the sternum. These materials are reported to have both positive and negative effects. In this review, we highlight the current clinical practices undertaken to prevent infection and bleeding as well as research progress in this field and their outcomes in controlling bleeding, infection, and enhancing sternal healing.

Analysis of sternal healing after median sternotomy in low risk patients at midterm follow-up: retrospective cohort study from two centres

Background

For low risk patients undergoing median sternotomies, no midterm follow-up studies involving sternal healing have been conducted. In this study we evaluated sternal healing in low risk patients by chest CT scan and the risk factors associated with poor healing were analyzed.

Methods

Patients who underwent sternal median incision heart surgery from September 2014 to March 2015 were recruited. The clinical information of these patients during hospitalization was collected, and the CT scan data were submitted to the two chief physicians of the Radiology Department for radiographical sternal healing score determination. Based on the method of wound closure, the patients were divided into sternum plate (Plates) and wire groups (Wires).

Results

Forty-four patients were recruited. The mean CT examination time was 17.27 ± 2.30 months postoperatively. Twenty-nine (65.9%) patients met the criteria for radiographic sternal healing. Three segments, including the aortopulmonary window, the main pulmonary artery, and the aortic root, had healed less in comparison to the manubrium segment. Compared to patients in whom 6–7 metal wires were used for sternal closure, healing of the lower sternum was worse in patients in whom five wires were used, but the difference in healing was not statistically significant. Univariate analysis of sternal healing showed that patient age was a risk factor for sternal non-healing. When the patient age was > 45 years, the predicted risk of radiographic sternal non-union was 1.833 (95% CI: 1.343–2.503).

Conclusions

At the mid-term follow-up, 65.9% of patients undergoing median sternotomies demonstrated radiographic sternal healing. Age, but not closure device, was a risk factor for sternal non-healing in low risk patients. Use of more wires had a positive impact on sternal healing.

Trial registration

researchregistry4918, registered 28 May 2019, retrospectively registered.

Analysis of bone healing with a novel bone wax substitute compared with bone wax in a porcine bone defect model

Aim:

This pilot study describes a novel composite of hydroxyapatite and biodegradable polylactic acid with wax-like handling properties (BoneSeal^®). The goal was to compare quantitative measures of bone healing between BoneSeal versus Bone wax.

Materials & methods:

BoneSeal and Bone wax were introduced into separate defects of a single porcine specimen. After 6 weeks, the defect sites were harvested for analysis.

Results:

Both groups had similar hemostatic action. The amount of new bone was significantly greater at 6 weeks in the BoneSeal group (38.05%) versus the Bone wax group (11.88%), p = 0.028.

Conclusion:

In this pilot study, BoneSeal had higher amounts of new bone formation compared with Bone wax.

This small pilot study compares two materials, Bone wax and BoneSeal, which could be used in bone surgery. In bone surgery, there is a need for the materials to stop bleeding as well as have good bone healing capabilities. We investigated the bone healing characteristics of two different materials. We implanted these materials into the arm and leg bones of a single pig. After a period of 6 weeks, we investigated the sites of implantation. We found that implantation sites of BoneSeal had higher amounts of new bone formation.

Sternal instability measured with radiostereometric analysis. A study of method feasibility, accuracy and precision

Background

A small, but unstable, saw-gap may hinder bone-bridging and induce development of painful sternal dehiscence. We propose the use of Radiostereometric Analysis (RSA) for evaluation of sternal instability and present a method validation.

Methods

Four bone analogs (phantoms) were sternotomized and tantalum beads were inserted in each half. The models were reunited with wire cerclage and placed in a radiolucent separation device. Stereoradiographs (n = 48) of the phantoms in 3 positions were recorded at 4 imposed separation points. The accuracy and precision was compared statistically and presented as translations along the 3 orthogonal axes. 7 sternotomized patients were evaluated for clinical RSA precision by double-examination stereoradiographs (n = 28).

Results

In the phantom study, we found no systematic error (p > 0.3) between the three phantom positions, and precision for evaluation of sternal separation was 0.02 mm. Phantom accuracy was mean 0.13 mm (SD 0.25).

In the clinical study, we found a detection limit of 0.42 mm for sternal separation and of 2 mm for anterior-posterior dislocation of the sternal halves for the individual patient.

Conclusion

RSA is a precise and low-dose image modality feasible for clinical evaluation of sternal stability in research.

Trial registration

ClinicalTrials.gov Identifier: NCT02738437, retrospectively registered.

Screening of Osteogenic-Enhancing Short Peptides from BMPs for Biomimetic Material Applications

Bone regeneration is an important issue in many situations, such as bone fracture and surgery. Umbilical cord mesenchymal stem cells (UC-MSCs) are promising cell sources for bone regeneration. Bone morphogenetic proteins and their bioactive peptides are biomolecules known to enhance the osteogenic differentiation of MSCs. However, fibrosis can arise during the development of implantable biomaterials. Therefore, it is important to control cell organization by enhancing osteogenic proliferation and differentiation and inhibiting fibroblast proliferation. Thus, we focused on the screening of such osteogenic-enhancing peptides. In the present study, we developed new peptide array screening platforms to evaluate cell proliferation and alkaline phosphatase activity in osteoblasts, UC-MSCs and fibroblasts. The conditions for the screening platform were first defined using UC-MSCs and an osteogenic differentiation peptide known as W9. Next, in silico screening to define the candidate peptides was carried out to evaluate the homology of 19 bone morphogenetic proteins. Twenty-five candidate 9-mer peptides were selected for screening. Finally, the screening of osteogenic-enhancing (osteogenic cell-selective proliferation and osteogenic differentiation) short peptide was carried out using the peptide array method, and three osteogenic-enhancing peptides were identified, confirming the validity of this screening.

Sternal healing after coronary artery bypass grafting using bilateral internal thoracic arteries: assessment by computed tomography scan

Background

This study aimed to investigate sternal healing over time and the incidence of poor sternal healing in patients undergoing coronary artery bypass graft (CABG) surgery using bilateral internal thoracic arteries.

Methods

This study enrolled 197 patients who underwent isolated CABG using skeletonized bilateral internal thoracic arteries (sBITA) from 2006 through 2009. Postoperative computed tomography (CT) angiography was performed on all patients at monthly intervals for three to six months after surgery. In 108 patients, an additional CT study was performed 24 to 48 months after surgery. The axial CT images were used to score sternal fusion at the manubrium, the upper sternum, and the lower sternum. These scores were added to evaluate overall healing: a score of 0 to 1 reflected poor healing, a score of 2 to 4 was defined as fair healing, and a score of 5 to 6 indicated complete healing. Medical records were also retrospectively reviewed to identify perioperative variables associated with poor early sternal healing.

Results

Three to six months after surgery, the average total score of sternal healing was 2.07±1.52 and 68 patients (34.5%) showed poor healing. Poor healing was most frequently found in the manubrium, which was scored as zero in 72.6% of patients. In multivariate analysis, the factors associated with poor early healing were shorter post-surgery time, older age, diabetes mellitus, and postoperative renal dysfunction. In later CT images, the average sternal healing score improved to 5.88±0.38 and complete healing was observed in 98.2% of patients.

Conclusion

Complete sternal healing takes more than three months after a median sternotomy for CABG using sBITA. Healing is most delayed in the manubrium.