Mechanism of sternotomy dehiscence

Mechanical Analysis of a Novel Sternal Closure System in Static Tensile Loading

The most common means of sternal closure after sternotomy is stainless steel wire cerclage. These wires, while inexpensive and simple in design, are known to be associated with low strength and sternal dehiscence. In this biomechanical analysis, we compare single sternal wires, double sternal wires, and a novel sternal closure device we have designed to mitigate sternal dehiscence. The device uses polymer grommets at the sternal interfaces to distribute load over a large surface area of bone. Samples of each closure device were installed in a bone model and distracted at a rate of 10 mm/min while tensile forces were continuously measured and compared. Single wires generated the lowest stiffness and strength values, followed by the double wires. The novel device demonstrated significantly higher stiffness and strength at all displacements compared with the single and double wires. Clinical use of this device may result in meaningful reduction in complications associated with the use of standard sternal wires such as sternal separation and fracture.

Practice Patterns in Sternal Closure and Evaluation of Adoption of a Novel Sternal Closure Device

OBJECTIVE

The technique for sternal closure has remained largely unchanged owing to the efficacy, simplicity, and low cost of stainless-steel sternal wires. Despite their ubiquity, several other closure devices designed to address the complications associated with sternal wires such as sternal bleeding and dehiscence have become popular. We have developed a novel sternal closure device that reduces sternal bleeding and dehiscence. This study quantifies the use of currently available sternal closure devices and determines predicted uptake of the novel device.

METHODS

An electronic survey, designed to determine practice patterns for sternal closure, was distributed to 70 US cardiac surgeons. The survey included a discrete choice section in which surgeons evaluated relative value of device attributes including cost, ease of emergent sternal reentry, and dehiscence risk.

RESULTS

There were 70 surgeons from 30 states who completed the survey. The most frequent means of sternal closure was straight sternal wires (35.8%), followed by straight sternal wires plus figure-of-8 sternal wires (18.1%), double wires (10.9%), plates (10.2%), and other (25%). The relative utilization shifted from sternal wires to sternal plates as the risk for dehiscence increased. The adoption of the novel closure device was estimated at 34.6%.

CONCLUSIONS

The standard stainless-steel sternal wire remains the most common means of sternal reapproximation, but its utilization is lower in patients at high risk for sternal dehiscence. Based on this survey, there is acceptance in the community for a novel sternal closure device designed to address the limitations of traditional sternal closure methods.

Injury to a cardiopulmonary resuscitation provider by sternal wire

Background

Median sternotomy is a common surgical procedure during cardiac and pulmonary surgeries. There are many reports of patient injury associated with wire breakage. However, there are only a few reports of healthcare worker injuries by sternal wire.

Case Presentation

A patient in his 70s, having a history of thoracic aorta replacement, collapsed suddenly and paramedics started mechanical chest compression. On hospital arrival, the emergency department nurse attempted to initiate manual chest compression but was injured by a sternal wire protrusion on the patient's chest. The emergency physician placed gauze on the sternal wire and continued manual chest compression, but the patient died.

Conclusion

To prevent this injury, cardiopulmonary resuscitation (CPR) providers should consciously check the patient's chest. If they observe wire exposure, they should immediately place a gauze, pad or consider performing mechanical chest compression. Safety measures such as the installing rubber pads in the AED should be considered.

Novel mesh suture may resist bone cutting seen with wire-based sternal closures

OBJECTIVE

Sternal dehiscence is frequently associated with wire-based closures cutting through fragile bone, allowing sternal motion, separation, and infection. We investigated whether bone cutting could be limited by using a newly available mesh suture with improved force distribution.

METHODS

Five sternal models were closed using 8 interrupted single sternal wires, double sternal wires, braided poly(ethylene terephthalate) sutures, single-wrapped mesh sutures, or double-wrapped mesh sutures. To simulate chest-wall forces, closed sternal models were pulled apart using 1020 N of axial force applied incrementally. Double sternal wire and double-wrapped mesh suture were further compared by closing 3 new models with each material and subjecting these models to cyclic loading cycles, simulating breathing and coughing. Image analysis of needle hole size measured "bone cutting" by each closure material and sternal distraction as a function of force.

RESULTS

All models exhibited maximal separation at the xiphoid. During axial loading, needle hole size increased 7.2% in the double-wrapped mesh suture model and 9.2% in the double-wire model. Single-wrapped mesh suture, single wires, and braided poly(ethylene terephthalate) extended needle hole size by 6.7%, 47.0%, and 168.3% of original size, respectively. The double-wire model resisted sternal distraction best, separating 0.285 cm at the xiphoid. During cyclic loading, mesh suture exhibited significantly less bone cutting (P = .02) than double wire, with comparable levels of sternal separation (P = .07).

CONCLUSIONS

Mesh suture may resist bone cutting seen in sternal wire closure in bone models with comparable distraction to currently used sternal closure methods.

“Negotiating a new normality” - a longitudinal qualitative exploration of the meaning of living with an open surgical wound

Purpose

Little is known about the experiences of people living with open surgical wounds. These wounds are common and predominantly affect young and actively working people. The aim of this qualitative study was to explore the meaning of living with open surgical wounds.

Methods

A qualitative exploratory study was conducted. We collected data using two individual interviews with each of ten participants (aged between 18–73 years) who had open surgical wounds. Our analytical approach was based on qualitative content analysis. Methods are reported using COREQ guidelines.

Results

We found that the meaning of living with open surgical wounds is shaped by five subthemes: “enduring healing”, “life disruption”, “adapting to a new reality”, “striving for healing” and “returning to normal life;” all under an overarching theme of “negotiating a new normality”.

Conclusion

Participants’ well-being and everyday living are greatly impacted by open surgical wounds. Findings from this study emphasize that open surgical wounds are a long-term condition with a typical “chronicity” trajectory; this brings a new perspective to previous findings of studies on living with complex wounds. This study has also highlighted areas for further research, related to improving individuals’ experience of living with open surgical wounds.

Percutaneous Cementoplasty to Treat Sternal Instability After Cardiac Surgery

Introduction

Although rare, sternal pseudarthrosis is encountered after cardiac surgery and impacts the quality of life by triggering motion-dependent chest pain. We thought to describe its treatment by percutaneous cementoplasty and report the clinical follow-up of patients treated in our institution.

Methods

This case series is a retrospective study based on five patients who benefited from a sternal cementoplasty as a treatment for symptomatic pseudarthrosis after cardiac surgery. The progression of the symptoms was assessed during clinical follow-up using the Quebec back pain disability (QBPD) scale and Visual Analog Scale (VAS).

Results

None of the patients presented evidence of local complications or neurological disorders. The intra- et post-operative images show no major leak of the cement, no embolism and no damage to the internal mammary artery or the heart. All patients described an improved quality of life due to reduced pain in all-day clinical activities. The QBPD scores improved from 54.8 ± 29.3 to 30.0 ± 17.4 (p = 0.02) and the VAS from 7.0 ± 2.8 to 1.6 ± 1.6 (p = 0.01). Furthermore, three out of five patients could completely stop taking analgesics.

Conclusion

Sternal pseudarthrosis is a debilitating affliction that may complicate sternotomy after cardiac surgery. This series demonstrates that a more conservative approach such as cementoplasty can be successful in terms of reducing pain, and constitutes a promising technique in selected cases.

Feedback Training Improves Compliance with Sternal Precaution Guidelines during Functional Mobility: Implications for Optimizing Recovery in Older Patients after Median Sternotomy

Patients often need to use their arms to assist with functional activities, but after open heart surgery, pushing with the arms is limited to <10 lb (4.5 kg) to help minimize force across the healing sternum. The main purposes of this study were to determine if older patients (>60 years old) (1) accurately estimated upper extremity (UE) weight bearing force of 10 lb or less and (2) if feedback training improved their ability to limit UE force and pectoralis major muscle contraction during functional activities. An instrumented walker was used to measure UE weight bearing force, and electromyography was used to measure pectoralis major muscle activity simultaneously during 4 functional mobility tasks. After baseline testing, healthy older subjects (n = 30) completed a brief session of visual and auditory concurrent feedback training. Results showed that the self-selected UE force was >10 lb for all tasks (20.0-39.7 lb [9.1-18.0 kg]), but after feedback training, it was significantly reduced (10.6-21.3 lb [4.8-9.7 kg]). During most trials (92%), study participants used >12 lb (5.5 kg) of arm weight bearing force. Pectoralis major muscle peak electromyography activity was <23% of maximal voluntary isometric contraction and was reduced (9.8-14.9%) after feedback training. Older patients may not be able to accurately estimate UE arm force used during weight bearing activities, and visual and auditory feedback improves accuracy and also modulation of pectoralis major muscle activation. Results suggest that an instrumented walker and feedback training could be clinically useful for older patients recovering from open heart surgery.

Value of Perioperative Chest X-ray for the Prediction of Sternal Wound Complications after Cardiac Surgery in High-Risk Patients: A "Work in Progress" Analysis

BACKGROUND

Sternal wound complications are serious events that occur after cardiac surgery. Few studies have investigated the predictive value of chest X-ray radiological measurements for sternal complications.

METHODS

Several perioperative radiological measurements at chest X-ray and clinical characteristics were computed in 849 patients deemed at high risk for sternal dehiscence (SD) or More than Grade 1 Surgical Site Infection (MG1-SSI). Multivariable analysis identified independent predictors, whilst receiver operating characteristics (ROC) curve analyses highlighted cut-off values of radiological measurements for the prediction of both complications.

RESULTS

SD occurred in 8.8% of the patients, MG1-SSI in 6.8%. Chronic obstructive pulmonary disease (COPD) was the only independent predictor for SD (Odds Ratio, O.R. 12.1; p < 0.001); proximal sternal height (PSH) was the only independent protective factor (O.R. 0.58; p < 0.001), with a cut-off value of 11.7 mm (sensitivity 70.5%, specificity 71.0%; ROC area under the curve (AUC) = 0.768, p < 0.001). Diabetes mellitus (O.R. 3.5; p < 0.001) and COPD (O.R. 21.3; p < 0.001) were independent predictors for MG1-SSI; indexed proximal sternal height (iPSH) was as a protective factor (O.R. 0.26; p < 0.001) with a cut-off of 5.97 mm (sensitivity 70.2%, specificity 69.0%; ROC AUC = 0.739, p < 0.001). No other radiological measurements were independently correlated with SD or MG1-SS (p = N.S.).

CONCLUSION

PSH and iPSH at preoperative chest X-ray may act as indicators of high risk for sternal wound complications, allowing for early preventative measures.

Continuous postoperative pericardial flushing method versus standard care for wound drainage after adult cardiac surgery: A randomized controlled trial

BACKGROUND

Excessive bleeding, incomplete wound drainage, and subsequent accumulation of blood and clots in the pericardium have been associated with a broad spectrum of bleeding-related complications after cardiac surgery. We developed and studied the continuous postoperative pericardial flushing (CPPF) method to improve wound drainage and reduce blood loss and bleeding-related complications.

METHODS

We conducted a single-center, open-label, ITT, randomized controlled trial at the Academic Medical Center Amstserdam. Adults undergoing cardiac surgery for non-emergent valvular or congenital heart disease (CHD) were randomly assigned (1:1) to receive CPPF method or standard care. The primary outcome was actual blood loss after 12-hour stay in the intensive care unit (ICU). Secondary outcomes included bleeding-related complications and clinical outcome after six months follow-up.

FINDINGS

Between May 2013 and February 2016, 170 patients were randomly allocated to CPPF method (study group; n = 80) or to standard care (control group; n = 90). CPPF significantly reduced blood loss after 12-hour stay in the ICU (-41%) when compared to standard care (median differences -155 ml, 95% confidence interval (CI) -310 to 0; p=≤0·001). Cardiac tamponade and reoperation for bleeding did not occur in the study group versus one and three in the control group, respectively. At discharge from hospital, patients in the study group were less likely to have pleural effusion in a surgically opened pleural cavity (22% vs. 36%; p = 0·043).

INTERPRETATION

Our study results indicate that CPPF is a safe and effective method to improve chest tube patency and reduce blood loss after cardiac surgery. Larger trials are needed to draw final conclusions concerning the effectiveness of CPPF on clinically relevant outcomes.

Use of new cannulated screws for primary sternal closure in high risk patients for sternal dehiscence

Background

Median sternotomy is still the approach of choice for heart surgery and the most common sternal closure is conventional six-wire technique. Mediastinitis is the frightening complication of the median sternotomy and occurs from 1% up to 2.4% of cases with a mortality rate which ranges from 14% up to 47%. Many methods have been suggested to reinforce the sternum with the common goal to improve sternal stability and prevent mediastinitis, but there is not consensus among cardiac surgeons on the optimal way to close the sternum. For this reason, we report our experience with a sternal device that, although not entirely new as a concept, has new technical features and plays a new role in preventing sternal dehiscence, according to the most recent findings on mechanism which leads to sternal dehiscence.

Methods

We enrolled 62 high risk patients for sternal dehiscence (patients with 2 well established historical risk factors), and we closed the sternum of the patients with a new surgical option consisting of passing, in a conventional six-wire sternal closure, the last sixth steel wire (Ø 1.0 mm, n° 5) through a couple of titanium cannulated screws (Ø 5.5 mm, self-tap-ping with a length from 10 to 16 mm and 2-mm increments) inserted into the 5th or 6th couple of rib cartilages.

Results

Primary chest closure with cannulated screws was performed on 48 males and 14 females. The average age of patients was 67.6 years (range, 43-88 years). The average follow-up was 12.8±16.2 months (range, 1-41 months). Chronic obstructive pulmonary disease (COPD) was the most common preoperative risk factor. The average number of risk factors was 2.4 (range, 2-4). Coronary artery bypass grafting (CABG) was the most common cardiac procedure. There were no peri-operative deaths. BMI >30 Kg/m² and diabetes were the associated of risk factors predisposing to superficial skin dehiscence.

Conclusions

In our clinical experience with high risk patients, this surgical option suggests that there is evidence of an effective stabilization of standard sternal closure and this option seems a promising technique to prevent the domino effect which starts from the xifoid bone and proceeds to the manubrium with the effect of leading to sternal instability which is the first step to mediastinitis.

Wearable Sensor-Based Digital Biomarker to Estimate Chest Expansion During Sit-to-Stand Transitions-A Practical Tool to Improve Sternal Precautions in Patients Undergoing Median Sternotomy

Sternal precautions are a universal part of the discharge education for post-sternotomy patients to reduce the risk of sternal complications. However, they are always designed based on physical therapists' or surgeons' subjective judgment without any objective evidence. Thus, they could be overly restrictive to hinder the patients' recovery, physically and psychologically. To fill this gap, this paper proposes a digital biomarker to estimate chest expansion during sit-to-stand transitions based on wearable inertial sensing and data fusion technologies. First, we carried out bench tests to evaluate the reliability of the digital biomarker to represent relative sensor rotation. We also verified effectiveness of this digital biomarker to detect subtle skin extension in proactive chest expansion trials by 11 healthy volunteers. Then, we measured the digital biomarker during sit-to-stand transitions with different strategies and some daily routine activities (walking, sitting, and standing) performed by the healthy volunteers and 22 post-sternotomy patients. The comparison between these measurements evaluated the effectiveness of several known guidelines of sternal precautions for sit-to-stand transitions. The results showed that first, pushing up from a chair by taking support from armrests induced larger chest expansion ( p = 0.009 ) compared with sit-to-stand transition while keeping the arms relaxed; second, crossing the arms or hugging a pillow can help reduce chest expansion ( ) compared with keeping the arms relaxed during sit-to-stand transitions; third, pushing up while taking support from a frontal support (e.g., table or walker) induced the same level of chest expansion ( ) as that during sit-to-stand transition while keeping the arms relaxed.

An Evidence-Based Perspective on Movement and Activity Following Median Sternotomy

Cardiac surgery via median sternotomy is performed in over 1 million patients per year worldwide. Despite evidence, sternal precautions in the form of restricted arm and trunk activity are routinely prescribed to patients following surgery to prevent sternal complications. Sternal precautions may exacerbate loss of independence and prevent patients from returning home directly after hospital discharge. In addition, immobility and deconditioning associated with restricting physical activity potentially contribute to the negative sequelae of median sternotomy on patient symptoms, physical and psychosocial function, and quality of life. Interpreting the clinical impact of sternal precautions is challenging due to inconsistent definitions and applications globally. Following median sternotomy, typical guidelines involve limiting arm movement during loaded lifting, pushing, and pulling for 6 to 8 weeks. This perspective paper proposes that there is robust evidence to support early implementation of upper body activity and exercise in patients recovering from median sternotomy while minimizing risk of complications. A clinical paradigm shift is encouraged, one that encourages a greater amount of controlled upper body activity, albeit modified in some situations, and less restrictive sternal precautions. Early screening for sternal complication risk factors and instability followed by individualized progressive functional activity and upper body therapeutic exercise is likely to promote optimal and timely patient recovery. Substantial research documenting current clinical practice of sternal precautions, early physical therapy, and cardiac rehabilitation provides support and the context for understanding why a less restrictive and more active plan of care is warranted and recommended for patients following a median sternotomy.

Direct sternal administration of Vancomycin and Gentamicin during closure prevents wound infection

OBJECTIVES

Deep sternal wound infection is still a major complication in patients undergoing cardiac surgery. We previously identified mammary artery harvesting as a risk factor for decreased antibiotic tissue penetration. In addition, other risk factors including diabetes may inhibit sufficient tissue penetration of perioperative antibiotic prophylaxis. A novel closure protocol applying 2 topical antibiotics and further recommendations for sternal wiring was introduced at our department to decrease the incidence of sternal wound infections.

METHODS

A 12-month period prior to (March 2013-February 2014) and after (July 2014-June 2015) the introduction of a novel sternal closure protocol was studied. All sternal wound infections resulting from an operation during this period were analysed. The closure protocol consisted of the intra-sternal application of vancomycin and the subcutaneous application of gentamicin. Furthermore, we increased the number of sternal wires for more uniform distribution of lateral forces.

RESULTS

Patients in both groups were comparable regarding demographic data and risk factors. Fifty-three out of 919 patients operated prior to the protocol change developed an infection (5.8%). The introduction of the novel sternal closure protocol reduced this number to 19 out of 932 patients (2.0%; P  < 0.001). A binary regression including common risk factors revealed a strong independent risk reduction by the novel protocol (OR 0.322, P  < 0.001). The number of sternal wires was not significant in this analysis.

CONCLUSIONS

The topical application of 2 antibiotic agents significantly reduced sternal wound infection. However, the results of this trial should be confirmed in a randomized trial.

Iterative metal artefact reduction (MAR) in postsurgical chest CT: comparison of three iMAR-algorithms

OBJECTIVES

The purpose of this study was to evaluate the impact of three novel iterative metal artefact (iMAR) algorithms on image quality and artefact degree in chest CT of patients with a variety of thoracic metallic implants.

METHODS

27 postsurgical patients with thoracic implants who underwent clinical chest CT between March and May 2015 in clinical routine were retrospectively included. Images were retrospectively reconstructed with standard weighted filtered back projection (WFBP) and with three iMAR algorithms (iMAR-Algo1 = Cardiac algorithm, iMAR-Algo2 = Pacemaker algorithm and iMAR-Algo3 = ThoracicCoils algorithm). The subjective and objective image quality was assessed.

RESULTS

Averaged over all artefacts, artefact degree was significantly lower for the iMAR-Algo1 (58.9 ± 48.5 HU), iMAR-Algo2 (52.7 ± 46.8 HU) and the iMAR-Algo3 (51.9 ± 46.1 HU) compared with WFBP (91.6 ± 81.6 HU, p < 0.01 for all). All iMAR reconstructed images showed significantly lower artefacts (p < 0.01) compared with the WFPB while there was no significant difference between the iMAR algorithms, respectively. iMAR-Algo2 and iMAR-Algo3 reconstructions decreased mild and moderate artefacts compared with WFBP and iMAR-Algo1 (p < 0.01).

CONCLUSION

All three iMAR algorithms led to a significant reduction of metal artefacts and increase in overall image quality compared with WFBP in chest CT of patients with metallic implants in subjective and objective analysis. The iMARAlgo2 and iMARAlgo3 were best for mild artefacts. IMARAlgo1 was superior for severe artefacts. Advances in knowledge: Iterative MAR led to significant artefact reduction and increase image-quality compared with WFBP in CT after implementation of thoracic devices. Adjusting iMAR-algorithms to patients' metallic implants can help to improve image quality in CT.

Internal rib structure can be predicted using mathematical models: An anatomic study comparing the chest to a shell dome with application to understanding fractures

The human rib cage resembles a masonry dome in shape. Masonry domes have a particular construction that mimics stress distribution. Rib cortical thickness and bone density were analyzed to determine whether the morphology of the rib cage is sufficiently similar to a shell dome for internal rib structure to be predicted mathematically. A finite element analysis (FEA) simulation was used to measure stresses on the internal and external surfaces of a chest-shaped dome. Inner and outer rib cortical thickness and bone density were measured in the mid-axillary lines of seven cadaveric rib cages using computerized tomography scanning. Paired t tests and Pearson correlation were used to relate cortical thickness and bone density to stress. FEA modeling showed that the stress was 82% higher on the internal than the external surface, with a gradual decrease in internal and external wall stresses from the base to the apex. The inner cortex was more radio-dense, P < 0.001, and thicker, P < 0.001, than the outer cortex. Inner cortical thickness was related to internal stress, r = 0.94, P < 0.001, inner cortical bone density to internal stress, r = 0.87, P = 0.003, and outer cortical thickness to external stress, r = 0.65, P = 0.035. Mathematical models were developed relating internal and external cortical thicknesses and bone densities to rib level. The internal anatomical features of ribs, including the inner and outer cortical thicknesses and bone densities, are similar to the stress distribution in dome-shaped structures modeled using FEA computer simulations of a thick-walled dome pressure vessel. Fixation of rib fractures should include the stronger internal cortex.

External rib structure can be predicted using mathematical models: An anatomical study with application to understanding fractures and intercostal muscle function

As ribs adapt to stress like all bones, and the chest behaves as a pressure vessel, the effect of stress on the ribs can be determined by measuring rib height and thickness. Rib height and thickness (depth) were measured using CT scans of seven rib cages from anonymized cadavers. A Finite Element Analysis (FEA) model of a rib cage was constructed using a validated approach and used to calculate intramuscular forces as the vectors of both circumferential and axial chest wall forces at right angles to the ribs. Nonlinear quadratic models were used to relate rib height and rib thickness to rib level, and intercostal muscle force to vector stress. Intercostal muscle force was also related to vector stress using Pearson correlation. For comparison, rib height and thickness were measured on CT scans of children. Rib height increased with rib level, increasing by 13% between the 3rd and 7th rib levels, where the 7th/8th rib was the widest part or "equator" of the rib cage, P < 0.001 (t-test). Rib thickness showed a statistically significant 23% increase between the 3rd and 7th ribs, P = 0.004 (t-test). Intercostal muscle force was significantly related to vector stress, Pearson correlation r = 0.944, P = 0.005. The three nonlinear quadratic models developed all had statistically significant parameter estimates with P < 0.03. External rib morphology, in particular rib height and thickness, can be predicted using statistical mathematical models. Rib height is significantly related to the calculated intercostal muscle force, showing that environmental factors affect external rib morphology.