Efficacy of Sternum GuardTM in Comparison of Bone Wax in Post Cardiac Surgery Patient: A Single Blind, Single Centre, Randomized Control Trial
Phase: NA
Conditions: Coronary Artery Disease, Valvular Heart Disease, Congenital Heart Disease in Adolescence, Post Operative Wound Infection, Surgical Site Infection, Postoperative Hemorrhage
Sponsor: Indonesia University

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UNIVERSITAS INDONESIA 
 
 
Efficacy of Sternum GuardTM in comparison of Bone Wax in Post 
Cardiac Surgery Patient: A Single Blind, Single Centre, Randomized 
Control Trial 
 
 
STUDY PROTOCOL AND STATISTICAL 
ANALYSIS PLAN 
 
 
Principal Investigator: 
Dr. dr. Dudy Arman Hanafy, Sp.BTKV (K) MARS. 
 
Investigator:  
dr. Konda Kinanti Muroso, BMedSc.  
dr. Sugisman, Sp. BTKV (K) 
 
 
 
FAKULTAS KEDOKTERAN UNIVERSITAS INDONESIA 
Department of Surgery 
Cardiac, Thoracic, and Vascular Surgery Division 
JAKARTA 
 20 December 2019 

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Abstract 
 
Introduction 
Median sternotomy is currently the main access site for cardiac surgery. Surgical site 
infection (SSI) of the sternum is a distressing complication in cardiac surgery after 
median sternotomy. The incidence of postoperative superficial and deep SSI in cardiac 
surgery varies from 1.3 to 12.8%. Bone wax is a nonabsorbable substance and it is 
believed that bone wax may cause inflammation and mechanically inhibit osteoblastic 
activity, which may eventually lead to increased risk of postoperative sternal dehiscence. 
Sternum GuardTM is a sternal protection device that covers the sternum after median 
sternotomy, it has specific mechanical protection that prevents lesions on the sternum. 
Therefore, we would like to evaluate the efficacy of Sternum GuardTM as opposed to Bone 
wax in post cardiac surgery patients in reducing the surgical site infection, sternal 
dehiscence and to assess the satisfaction rate of the surgeons.  
 
Objectives 
The aim of the research is to evaluate the efficacy of Sternum GuardTM in post cardiac 
surgery patient with the application of Sternum GuardTM in comparison with bone wax 
intraoperatively. 
Method 
This study will adopt a single blind, single center, randomized control trial design for 3 
months. 
 
 
 
 
 
 
 
 

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Table of Contents 
Abstract............................................................................. Error! Bookmark not defined. 
List of Tables................................................................................................................ V 
Chapter 1 ..................................................................................................................... 8 
Introduction ................................................................................................................. 8 
1.1 Background .................................................................................................................. 8 
1.2 Research Problem Formulation ................................................................................... 9 
1.3 Research Questions ...................................................................................................... 9 
1.4 Hypothesis .................................................................................................................... 9 
1.5 Objectives ..................................................................................................................... 9 
1.6 Benefit of the Study .................................................................................................... 10 
1.6.1 Academic Aspect ................................................................................................................ 10 
1.6.2 Clinical Aspect ................................................................................................................... 10 
1.6.3 Research Aspect ................................................................................................................. 10 
Chapter 2 ................................................................................................................... 11 
Literature Review ....................................................................................................... 11 
2.1 Sternum anatomy ....................................................................................................... 11 
2.2 Median sternotomy .................................................................................................... 12 
2.3 Complications following median sternotomy ............................................................ 14 
2.4 Surgical site infection ................................................................................................. 14 
2.5 Risk factors for sternal wound infections .................................................................. 17 
2.6 Deep sternal wound infection ..................................................................................... 19 
2.7 Sternal dehiscence ...................................................................................................... 19 
Chapter 3 ................................................................................................................... 22 
Methods ..................................................................................................................... 22 
3.1 Design ......................................................................................................................... 22 
3.2 Time and location ....................................................................................................... 22 
3.3 Sample and population ............................................................................................... 22 
3.4 Inclusion and exclusion criteria ................................................................................. 22 
3.5 Randomization and blinding procedure, and assessment schedule .......................... 23 
3.6 Data extraction ........................................................................................................... 23 
3.7 Sample size estimation ............................................................................................... 24 
3.8 Variable identification ................................................................................................ 25 
3.9 Data analysis ............................................................................................................... 25 
3.10 Clinical outcome indicators and assessments .......................................................... 25 

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3.11 Operational definition .............................................................................................. 26 
3. 12 Ethics ....................................................................................................................... 29 
3. 13 Research flow........................................................................................................... 30 
3.14 Dummy table ............................................................................................................ 31 
References.................................................................................................................. 32 
Appendix .................................................................................................................... 36 
Questionnaire for the Surgeons ........................................................................................ 38 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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List of Tables 
 
Table 1 - Table of Operational Definition ................................................................... 26 
 
Table 2 - Dummy Table 1 ........................................................................................... 31 
 
Table 3 - Dummy Table 2 ........................................................................................... 31 
 
Table 4 - Time Schedule ............................................................................................. 36 
 
Table 5 – Resources fee .............................................................................................. 36 
 
Table 6 - Materials Cost .............................................................................................. 37 
 
Table 7 - Operational Cost .......................................................................................... 37 
 
Table 8 - Total Amount............................................................................................... 37 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
8 
 
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Chapter 1 
 Introduction 
 
1.1 Background 
Nowadays, a high volume of cardiac surgery has been performed at National 
Cardiovascular Centre Harapan Kita, Jakarta, Indonesia. In 2017 there were 1721 cardiac 
surgery conducted in the adult cardiac surgery division.1 Of those, 801 were coronary 
artery bypass graft surgeries, 598 were heart valve repair and replacement surgeries, 93 
were vascular surgeries, 116 were congenital cardiac surgeries, 8 surgeries in intracardiac 
tumour, and 105 other cardiac surgeries.1  
 
In cardiac surgeries, the current approach established is through median sternotomy. The 
sternum consists of a low vascularized tissue and it may be damaged especially when 
internal thoracic arteries are used for coronary artery bypass grafting. Thus, the 
postoperative complication related to sternal healing are common. 2-4 The sternotomy 
wound may be complicated with partial or complete sternal dehiscence and sternal wound 
infection, osteomyelitis or even mediastinitis. Surgical site infection (SSI) involving the 
sternum is a distressing complication in cardiac surgery. The incidence of postoperative 
superficial and deep SSI in cardiac surgery varies from 1.3 to 12.8%. 2 
 
Subsequent to median sternotomy, bone wax has been applied for decades as a 
mechanical barrier to maintain the haemostasis on the surface edges of the sternum. Bone 
wax is a nonabsorbable substance and it is believed that bone wax may cause 
inflammation as it is produced foreign body reaction and mechanically inhibit 
osteoblastic activity, which may eventually lead to increased risk of postoperative sternal 
dehiscence. Apparently, the use of bone wax has no clear recommendation in any 
guidelines and there are still controversies regarding the efficacy and safety of the 
application of bone wax. 3-5  
 
To overcome the problem that may be related to the use of bone wax. Different innovative 
approaches are evaluated, including, a non-woven material to protect the sternum during 
operation. Sternum GuardTM is a single use, sterile surgical drape, for sternal protection, 

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with modified cellulose designed specifically to reduce the risk of surgical site infection. 
It is a sternal protection device that covers the sternum after median sternotomy and has 
specific mechanical protection that prevents lesions on the sternum. It is made from a non 
– woven material. Sternum GuardTM provides haemostatic effect through a natural 
reaction to compression and blood absorption. Moreover, it decreased the bacterial 
proliferation by decreasing the pH. The Sternum GuardTM covers the entire incision angle 
and subcutaneous tissue and it has very low particle release. It is easy to use and maintains 
a dry surgical site. 6-7 
 
However, there are still insufficient evidence to support the use of modified cellulose 
non-woven material in cardiac surgery. Thus, in this study we would like to compare the 
efficacy of Sternum GuardTM as opposed to Bone wax in post cardiac surgery patients.  
 
1.2 Research Problem Formulation 
There is a deficient of evidence to verify the efficacy of Sternum GuardTM in reducing the 
rates of surgical site infection and sternal dehiscence in post cardiac surgery patients, 
specifically in Indonesian characteristic subjects. Thus, we would like to conduct this 
study to provide evidences regarding the use of Sternum GuardTM. 
 
1.3 Research Questions 
Is Sternum GuardTM more effective than Bone Wax application intraoperatively in 
reducing surgical site infection and sternal dehiscence for post cardiac surgery patients?  
 
1.4 Hypothesis  
We hypothesize that Sternum GuardTM is more effective than Bone Wax in reducing 
surgical site infection and sternal dehiscence for post cardiac surgery patients.  
 
1.5 Objectives  
Overall Objective: 
The aim of the research is to compare the efficacy of Sternum GuardTM as opposed to 
bone wax in post cardiac surgery patient.  
 

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Specific Objectives: 
1. To compare the surgical site infection and sternal dehiscence rates at the end of hospital 
stay, day 14 post operation, and day 30 post operation in post cardiac surgery patient with 
the application of Sternum GuardTM as opposed to bone wax intraoperatively.  
2. To compare the haemostasis effect of Sternum GuardTM as opposed to bone wax 
intraoperatively in cardiac surgery.  
3. To compare the satisfaction rate (includes global satisfaction rate, haemostasis and 
dryness of surgical site, and mechanical protection) of the surgeons who are using the 
Sternum GuardTM as opposed to bone wax intraoperatively in cardiac surgery.  
 
1.6 Benefit of the Study 
1.6.1 Academic Aspect  
This study is expected to benefit academically by providing an answer as well as 
justification on the efficacy of Sternum GuardTM in post cardiac surgery patient in 
comparison with bone wax intraoperatively. 
 
1.6.2 Clinical Aspect  
This study is believed to have impact clinically in reducing surgical site infection and 
sternal dehiscence in post cardiac surgery patients. By reducing the surgical infection and 
sternal dehiscence rates it would reduce the morbidities and mortalities rates as well.  
 
1.6.3 Research Aspect  
This study could be the foundation of another study in evaluating which aspects that could 
lead to surgical site infection and sternal dehiscence post cardiac surgery. Additionally, 
it could identify another effective method to reduce the percentages of surgical site 
infection and sternal dehiscence in post cardiac surgery patients.  
 
 
 

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Chapter 2 
 Literature Review 
 
2.1 Sternum anatomy  
Interestingly, the anatomy and physiology of the chest wall and sternum are completely 
entangled. The musculoskeletal structure of the chest wall and sternum are served to give 
protection to the lungs and thoracic viscera. The structure of the skeletal of the thorax 
consists of 12 pairs of ribs and their cartilages, 12 thoracic vertebrae, the intervertebral 
discs, and the sternum.8 
The sternum lies in the anterior midline. It is an elongated and flat bone and has 
approximately 15 to 20 cm long. It is structured from the cartilaginous precursors that 
ossify separately to form the components in which divided by three parts: the manubrium, 
the body, and the xyphoid process.9-10 
The first part is the manubrium, it is about 5 cm wide in its upper half and around 2.5 to 
3 cm wide in its lower half. The upper border of the manubrium is solidified and marked 
on either side by a notch for articulation with the clavicle. Ventrally, an indentation is 
present together with the sternal ends of each of the clavicle, it forms the jugular or the 
suprasternal notch. The widest part is distinct by the bilateral indentations, the costal 
incisura, in which to accommodate articulation of the first costal cartilage.9 
The second part is the body of the sternum. It is the longest part and slightly more than 
twice the length of the manubrium. It is skewed at a steeper angle than the manubrium 
and its articulation with that bone forms the angle that is called the sternal angle. The 
lateral side of the body expose segmental incisura for articulation of coastal cartilage 2 to 
7. This part ends a about the level of the 10th or 11th of thoracic vertebrae, where it forms 
a cartilaginous joint with the xyphoid process. 9 
The last part of the sternum called the xyphoid process. It is the shortest and thinnest part 
of the sternum. Occasionally, this part is bifid or perforated. 9 
 

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The blood supply to the sternum has been studied repeatedly over the past decades 
especially its association with the notorious complication in sternotomy wound healing. 
The major source of arterial branches to the sternum is the internal thoracic or mammary 
artery (ITA or IMA). It originates from the subclavian artery directly or sometimes from 
a common trunk with another artery of the thyrocervical trunk. Before entering the 
mediastinum, it crosses the phrenic nerve either dorsally or ventrally. It descends 1–2 cm 
from the lateral margin of the sternum adjacent to the posterior aspect of the chest wall, 
partly covered by the transversus thoracic muscle from the third to the sixth costal 
cartilage.11 
Blood supply to the sternum originate either directly from the medial aspect of the ITA 
(non-collateral branches) or from short trunks that also give rise to perforating branches 
to the intercostal and pectoral muscles and overlying skin or to anterior intercostal rami. 
Sternal blood supply branches are intersegmental, means that it is located in the 
intercostal spaces and form arcades at the lateral edge of the sternum. It is also more 
frequent in cranial than in caudal segments, particularly in the second and third intercostal 
space.  
Based on the blood supply anatomy it is evident that harvesting of the ITA or IMA for 
coronary bypass surgery will interrupt the sternal circulation to some extent. Therefore, 
when the ITA or IMA is dissected, any branches should be ligated as close as possible to 
the main vessel in order to preserve the collateral branches.12 
2.2 Median sternotomy  
Median sternotomy remains the most common incision used for cardiac surgical 
procedures as it offers straightforward access to all cardiac chambers and to the origins 
and proximal portions of the great vessels. This incision can also be used to repair aortic 
arch lesions and descending thoracic aortic lesions.  
 
A straight vertical midline skin incision is generally made in patients undergoing a 
median sternotomy. This incision commences several centimeters below the suprasternal 
notch and extends to the tip of the xiphoid. The exact midline over the sternum then is 
scored with the cautery. A retractor elevates the upper angle of the vertical skin incision, 
placing the underlying tissues on tension. The soft tissue is separated from the superior 

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surface of the manubrium, and a right-angled clamp is passed over the denuded 
manubrium into the space behind, hugging the bone. The clamp is spread to create a space 
for the tip of the sternal saw. The suprasternal ligament is cut with the cautery.13 
 
The blade of an electric or air-driven saw is held snugly against the posterior surface of 
the manubrium with the cutting edge against the superior manubrial surface. After 
activating the saw, the surgeon cuts the manubrium and sternum, staying precisely in the 
midline. The tip of the saw is kept elevated so that the toe of the saw hugs the back of the 
sternum. During sawing, the anesthesiologist should cease ventilating the patient and 
exert no pressure on the lungs, so that the soft tissue and pleura will fall away from the 
sternum. Drifting away from the midline with the saw must be avoided because the 
sternum will not spread evenly, and its later closure will be more difficult.13 
 
Alternatively, the sternum can be divided from the bottom up. The xiphoid process is 
mobilized or excised, and the tip of the blade is introduced beneath it. In neonates and 
infants, the xiphoid process may be excised, the costal margin on either side elevated by 
sharp retractors, and sharp, well-aligned scissors used to cut the sternum in the midline, 
from below upward.13 
 
When the incision is properly made, the pleural spaces are infrequently entered. A thin 
layer of bone wax is spread over the bone marrow, primarily where the bleeding is active. 
When the sternum is fragile, as in older patients, it is better to avoid wax altogether. 
Bleeding points in the cut edge of the anterior and posterior sternal periosteum are 
cauterized, but excessive cauterization should be avoided. A retractor is inserted and 
opened just enough to permit dissection. After a few minutes, it is opened further. It 
should be opened no more than is necessary for the procedure, because excessive 
retraction, particularly of the upper half of the sternum, may cause rib fractures, 
dislocation of costochondral junctions, injury to the brachial plexus, and damage to the 
stellate ganglion.13 
 
Dissection continues by incising the fascia that envelops the thymus gland. The right and 
left lobes of the thymus are separated up to the level of the brachiocephalic vein. In infants 

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and children, and occasionally in adults, the thymus may be sub-totally resected, leaving 
only the cervical portion cephalad to the brachiocephalic vein, to avoid expanding 
hematomas that may cause postoperative bleeding.13 The pericardium is then opened 
longitudinally in the midline, from the diaphragm below to the brachiocephalic vein 
above. Where this incision meets the diaphragm, care must be taken not to incise the 
parietal peritoneum. If entry is made into the peritoneal cavity, the opening is sutured to 
avoid sequestration of blood and fluid in it. The pericardium is cut at right angles to the 
longitudinal incision at its diaphragmatic end, farther on the left than on the right, after 
pushing back the pleura to avoid entering the pleural spaces. Pericardial stay sutures are 
then placed.13  
 
2.3 Complications following median sternotomy  
Sternal wound complications following median sternotomy remain a challenge in cardiac 
surgery with a severe burden for the patient and high costs for health care providers.14-16 
According to previous studies, superficial problems occurred in 1.1–6.7% whereas the 
incidence of deep sternal wound complications ranged from 0.1 to 3.7%.17-19 
A change in the spectrum of cardiac surgery has been observed in recent years. Patients 
are older, suffer more frequently from diabetes mellitus and have a higher average body 
mass index (BMI). There is a decreasing number of surgical bypass grafts20,21 
accompanied by a trend towards more valve operations and complex procedures. In 
addition, the frequency of emergency procedures is rising.22  
 
2.4 Surgical site infection 
Over 234 million surgeries are performed around the world every year23, yet despite the 
remarkable advances in surgical technologies and anaesthetic techniques, surgical site 
infections (SSIs) remain a major cause of patient morbidity and mortality.24 SSIs are 
potential complications associated with any surgical procedure; however, they are the 
most preventable hospital acquired infection (HAI). It is estimated that SSI will occur in 
up to 9.5% of inpatient surgical procedures. SSI is defined as any infection occurring 
within 30 days after surgery or within 12 months of surgical implantation of a prosthesis 
or foreign body.23  
 

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Millions of surgical procedures are conducted around the world each year. Most 
procedures result in surgical wounds that heal by primary intention, where wound edges 
are re-approximated using sutures, staples, clips or glue. Some surgical wounds are left 
open to heal (where closure is not appropriate because of infection, physical impossibility 
of approximating wound edges or because of the need to allow drainage) and some 
wounds break down following closure; these open wounds heal from the 'bottom-up' 
(known as 'healing by secondary intention').23  
 
Surgical wounds are at risk from microbial contamination and thus possible infection. 
Contamination may originate from the patient, for example when microbes on the skin 
enter a wound, or from the surrounding environment, for example from operating staff, 
the theatre, or wider hospital and home environments. SSI was identified as the leading 
cause of hospital-acquired infection in a systematic review of studies in low-and middle-
income countries.25  
 
SSI is a serious global issue that can lead to significant morbidity, need for re-intervention 
and treatment (including antibiotic use), delayed wound healing, and in very serious 
infections, the possibility of death.26,27 SSIs also increase consumption of healthcare 
resources. Recent figures from the UK suggest that SSIs lead to a median increased 
hospital stay of 10 days (95% confidence interval (CI) 7 to 13 days) with an associated 
median additional cost attributed to SSI of GBP 5239 (95% CI GBP 4622 to 6719). The 
UK National Institute for Health and Care Excellence (NICE) identified that an SSI 
increased the costs of surgery by two to five times.28 In the USA, Lissovoy et 
al29 estimated that the extended length of stay and increased treatment costs associated 
with SSIs over a one-year period led to approximately 1 million additional inpatient-days, 
costing an additional USD 1.6 billion. 
 
Definition of SSI  
Although there is no single agreed diagnostic tool or protocol to confirm the presence of 
an SSI, Bruce et al 30  identified 41 different definitions for SSI and 13 grading scales, the 
Centers for Disease Control and Prevention (CDC) definition is commonly used.31 
 

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A superficial SSI is defined as: an infection occurring within 30 days after the operation 
and only involving the skin and subcutaneous tissue of the incision that is associated with 
at least one of the following: 
• 
Purulent drainage, with or without laboratory confirmation, from the surgical site; 
• 
Organisms isolated from an aseptically-obtained culture of fluid or tissue from the 
surgical site; 
• 
At least one of the following signs or symptoms of infection: pain or tenderness, 
localised swelling, redness or heat, and superficial incision is deliberately opened 
by the surgeon and is culture-positive or not cultured. A culture-negative finding 
does not meet this criterion; 
• 
Diagnosis of SSI by the surgeon or attending physician. 
 
A deep incisional SSI is defined as: infection that occurs within 30 days after the 
operative procedure if no implant is left in place, or within one year if an implant is left 
in place, and the infection appears to be related to the operative procedure and involves 
deep soft tissues (e.g. fibrous connective tissues and muscle layers) of the incision 
associated with one of the following: 
• 
purulent drainage from the deep incision, but not from the organ/space component 
of the surgical site; 
• 
a deep incision spontaneously dehisces (opens up) or is deliberately opened by 
the surgeon and is culture-positive or not cultured when the patient has at least 
one of the following symptoms: fever or localised pain or tenderness; 
• 
an abscess, or other evidence of infection involving the deep incision is found on 
direct examination, during re-operation, or by histopathologic or radiologic 
examination; 
• 
diagnosis of a deep incisional SSI by a surgeon or attending physician. 
 
 
 
 
 
 

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Interventions 
Many interventions are used with the aim of reducing the risk of SSI in people undergoing 
surgery. These interventions can be delivered at three stages: preoperatively, 
intraoperatively and postoperatively32 
• 
Preoperative phase: the time period between the decision for the need for surgery 
and when everything is ready for the operation to start, that is, the patient is on 
the operating table. 
• 
Intraoperative phase: the time period from when the patient is on the operating 
table to when the operation has finished and the wound is closed (if relevant). Any 
activity taking place after induction of anaesthesia to be in this phase because this 
starts in the operating theatre itself.  
• 
Postoperative phase: as the time period from the end of the intraoperative phase 
to resolution of surgical procedure. Whilst dressings, wound drains and negative 
pressure wound therapy are often placed over wounds at the end of surgery, their 
use is predominantly outside of theatre, so they are considered in the postoperative 
phase. 
 
2.5 Risk factors for sternal wound infections 
The risk factors for sternal wound infection is multifactorial. Any factors that contributes 
to poor wound or bone healing (e.g. malnutrition, osteopenia) or increases the risk for 
surgical site infection (e.g. diabetes mellitus, immunosuppression) may influence the 
manifestation of sternal wound infection, especially if two or more factors are present. 33-
40 There are several retrospective and prospective studies that have identified other factors 
relating to sternal wound infection. It is included obesity, diabetes mellitus, hypertension, 
chronic obstructive lung disease (COPD), smoking, steroid therapy, immunosuppression, 
advanced age, congestive heart failures, and respiratory failures. 41-42 
There are also technical factors that play a role in the risk of sternal wound infection or 
even sternal dehiscence. It may include prolonged operative time, the need for chest 
compression, 
postoperative 
bleeding, 
intraoperative 
complication, 
transfusion, 
reoperation, asymmetric sternotomy incision that is difficult to realign, bone ischemia 
due to excessive use of electrocautery or possibly internal thoracic artery harvesting 

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(especially if bilateral), or even the excessive use of bone wax around the sternal edges 
intraoperatively. 42-45 
Bone Wax  
Bone wax was first introduced in medicine in 1886. It is a sterile stick and is used as a 
topical haemostatic material composed of a softening agent such as Vaseline and 
beeswax. When it is applied on the surface of the bones, it remains indeterminately and 
may cause various adverse effects. 46-48 
 
At first the primary reason for using bone wax is to maintain haemostasis. However, it 
has no biological or chemical hemostatic effect. One study stated that the hemostatic 
effect of bone wax is associated with the physical blocking of the holes in the bone and 
stopping the blood flow from damaged vessels into the bone. However, the literature data 
do not support a reduction of blood or blood product consumption as a result of a 
presumably decreased perioperative blood loss when using bone wax. 46 
 
Additionally, bone wax is known to inhibit bone healing and osteogenesis. It inhibits the 
osteoblastic activity, prevent bone healing and may lead to creation of a pseudo-arthrosis. 
A sternal wound is different than other bone wound, it is associated with the exertion of 
dynamics of a chest wall mobility especially in the work of breathing. Thus, the 
osteogenesis and the wound healing is very important. It is reported that chronic 
inflammatory reactions with the presence of residual bone wax exist up to 10 years after 
the operation. 48-54 
 
Bone wax is not an absorbable or metabolized material. It may induce a foreign body 
reaction which characterized by giant cells, plasma cells, fibrous tissue, and a lack of 
bone formation, that may trigger an allergic reaction or granuloma formation. 47-48, 52-54 In 
anatomic-pathology study of 18 cadavers by Sudmann et al, it was reported that bone wax 
induces chronic inflammation and granuloma formation in the sternum postoperatively.55 
Moreover, bone wax has shown to be related with pulmonary embolic events. In an 
experimental study, in which, there were radioactively labelled bone wax applied at the 
sternal wound. It was found that bone wax accumulated in significant quantities in the 

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lung. This shows that bone wax may embolize and may give rise to secondary pulmonary 
complications.54  
2.6 Deep sternal wound infection  
Deep sternal wound infection (DSWI) is a serious postoperative complication of cardiac 
surgery. According to the literature, the incidence of DSWI after cardiac surgery has been 
variously reported as between 0.8 and 5.0%.55-59 This postoperative complication is a 
serious one, being responsible for a mortality rate varies between 19% and 29% in 
different series of adult cardiac surgical patients. 55-59 Based on JACVSD registered data 
from 2004 to 2009, the overall incidence of DSWI after cardiac surgery was 1.8%, as for 
each operative procedure, the incidence of postoperative DSWI was 1.8% in isolated 
CABG group, 1.3% in valve group, 2.8% in valve with CABG group, 1.9% in thoracic 
aorta group and 3.4% in thoracic aorta with CABG group. When operative procedure 
concomitant with CABG was done, the incidence of postoperative DSWI showed 1.5% 
of elevation compared with isolated original valve and thoracic aortic procedure. Internal 
thoracic artery use, prolonged operative time and longer cardiopulmonary bypass time 
are possible mechanisms to explain these increased rates of DSWI. 
 
2.7 Sternal dehiscence  
Sternal Dehiscence is a serious complication of cardiac surgery which is often a 
predecessor to mediastinitis, in fact it is often accompanied with mediastinitis. The 
incidence of sternal dehiscence after median sternotomy is varied between 0.5% to 8.4%. 
60-63 Sternal dehiscence is defined as the separation of the edges of the sternum from one 
to another and can occur in the absence of soft tissue dehiscence. This condition can be 
caused by wire fracture, loosening, or “puling through” the sternal edges. 64 
 
Patients may complain of a painful chest motion and “clicking”. The diagnosis is made 
upon physical examination by placing each hand on either side of the sternum and having 
the patient cough, which will cause a click or “rocking” of the sternum64. Sternal 
dehiscence is a surgical emergency as the complication may include an increased risk of 
ventricular rupture due to sharp wires or bone fragments rubbing against the heart. When 
sternal dehiscence occurs in the early postoperative period, the patient is taken to the 
operating room for exploration.64-65 

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Theoretical Framework  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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Conceptual Framework 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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Chapter 3 
Methods 
 
 
3.1 Design  
This study will adopt a single blind randomized control trial design for 3 months.  
 
3.2 Time and location 
This study will be conducted for 3 months, starting from December 2019 – February 
2020. It will be held at the National Cardiovascular Centre Harapan Kita, Jakarta, 
Indonesia.  
 
3.3 Sample and population  
The participant in this study will be recruited from the adult cardiac surgery division at 
the National Cardiovascular Centre Harapan Kita, Jakarta, Indonesia. All participants will 
be selected randomly and are eligible for cardiac surgery. Participants then will undergo 
an eligibility assessment based on the inclusion and exclusion criteria. Afterwards, the 
participants that are qualified for this study will be divided into two groups (control vs 
treatment group) randomly.   
 
3.4 Inclusion and exclusion criteria 
Inclusion Criteria: 
1. Patients ages > 18 years old  
2. Patients who are scheduled electively for cardiac surgery  
3. Cardiac surgery with the usage of cardiopulmonary bypass machine 
4. Patients who are agreed to participate in this study 
 
Exclusion Criteria: 
1. Patients who are scheduled for surgery in emergency or urgent manner  
2. Patients with the history of uncontrolled hypertension and uncontrolled diabetes 
mellitus.  
3. Patients with the history of past cardiac surgery  

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Drop – out Criteria:  
1. Patients who are pronounced death on operation table  
2. Patients who are pronounced death within hospitalization  
3. Patients who are lost to follow up (Day 30 post-operative) 
4. Patients who are not committed for the whole stage of the research 
 
3.5 Randomization and blinding procedure, and assessment schedule  
Participants which are included in this study will be randomized into two groups: A. 
Control Group (Bone Wax) and B. Treatment Group (Sternum GuardTM). The 
randomization process will be conducted by a block randomisation technique. This study 
is conducted in a single blind manner. The surgeons will not be blinded by the 
intervention, as it is impossible for the surgeons to not acknowledge the intervention. The 
participants on both groups will be blinded for the intervention given. The project leader 
will also be blinded when gathering and assessing the data from the study. Both of the 
groups then will be assessed for outcomes intraoperatively, at the end of the hospital stay, 
day 14 post – operative, and day 30 post - operative. The surgeons’ point of view on both 
interventions will be evaluated after the surgery.  
 
3.6 Data extraction  
Every participant included in this study will be scheduled for any cardiac surgery 
electively. Every participant will undergo the surgery with cardiopulmonary bypass. All 
of the surgery will be conducted in a similar manner, however, if there is any complication 
intraoperatively, every action will be taken according to the situation and will be 
recorded. Before incision the Sternum GuardTM and sterile drapes for the bone wax group 
will be weighed. After median sternotomy, the surgeons will be given Bone Wax or 
Sternum GuardTM to be applied to the sternum. The decisions will be made based on the 
block randomisation technique and will be informed beforehand to the nurse scrub and 
the surgeon. In the Bone Wax group, cauterization will be used according to the sternum’s 
condition and surgeon’s decision before applying the sterile draping and after removing 
it if needed. In the Sternum GuardTM group, cauterization will also be applied before 
inserting it to the sternum and after removing the Sternum GuardTM if needed.  
 

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Subsequent to median sternotomy, sternal bleeding will be assessed. In the Sternum 
GuardTM group, immediately before cauterization and in Bone Wax group right before 
applying the bone wax.  
Once the surgery is done, the Sternum GuardTM and the sterile drapes will be weighed 
again. Sternal trauma will be evaluated at the end of surgery (visible trauma or no visible 
trauma). In the Sternum GuardTM group, within 5 minutes of Sternum Guard and sternal 
retractors removal and on the Bone Wax group within 5 minutes of removal of the sterile 
drapes and sternal retractors. Another sternal bleeding assessment will be done on both 
groups. in the Sternum GuardTM group it will be assessed immediately after removing the 
Sternum Guard, before the cauterization, while on the Bone Wax group, before applying 
any bone wax and cauterization. The sternotomy wound will be evaluated and 
documented at Day 0, at the end of hospital stay, Day 14 post - operative, and Day 30 
post-operative. After the surgery, the surgeons will be given questionnaire regarding the 
use of Sternum GuardTM as opposed to Bone Wax.  
 
3.7 Sample size estimation  
The sample size in this study is estimated by using the formula for hypothesis tests for 
two population proportions (two-sided test) 
 
𝑛= 
%𝑍'()/+,2𝑃/(1 −𝑃)
/// + 𝑍'(5,𝑃'(1 −𝑃') + 𝑃+(1 −𝑃+)6
+
(𝑃' −𝑃+)+
 
 
details: 
a 
: 5 
1-b 
: 90 
P1 
: 0.15 
P2 
: 0.05 
n 
: 376 
 
From the equation above, it is estimated for the sample size of the study to be 376 samples, 
with estimated drop out proportion of 10%, it is deduced the sample size of 414 samples.  
 

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3.8 Variable identification  
Independent variable in this study included the patient that are eligible for cardiac surgery. 
Dependent variable in this study are the assessment of surgical site infection and sternal 
dehiscence, haemostasis effect in Sternum GuardTM and Bone Wax group, and 
satisfaction rates of the surgeons. 
 
3.9 Data analysis  
All collected data will be verified and will be statistically analyzed using SPSS and the 
result from the data analysis was considered statistically significant with a p-value of < 
0.05. For descriptive analysis, we will perform the analysis independently for numerical 
and categorical data. All numerical data will be analyzed using Coefficient of Variance 
and confirmed by Kolmogorov-Smirnov normality test. Normally distributed data will be 
analyzed using mean and standard deviation, meanwhile the abnormally distributed data 
will be analyzed using median, minimum value and maximum value. Categorical data 
analysis will be presented by percentage and frequencies table.  
 
For inferential data analysis, we will perform the comparison tests and mean comparison 
test. The proportion comparison tests are applied for comparing categorical independence 
variable between Sternum GuardTM and bone wax group, such as Chi-square test and 
Fisher’s Exact test as an alternative for chi-squared test. Mean comparison tests are 
utilized for comparing numerical independence variable between Sternum GuardTM and 
bone wax group, such as Independent T-Test and Mann-Whitney test for the non-
parametric test.         
 
3.10 Clinical outcome indicators and assessments  
1. Surgical site infection: assessment of the surgical site infection includes the types 
of infection (deep and superficial), sternal dehiscence, and percentage of the 
surgical site infection and sternal dehiscence.  The participants will be assessed at 
day 0, at the end of the hospital stay, day 14 post - operative, and day 30 – post 
operative. All of the sternotomy wound will be documented digitally at day 0, at 
the end of the hospital stay, day 14 post – operative, and day 30 post-operative.  
 

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2. Haemostasis effect: It will assess the quantity of blood lost from the sternal edges 
in Sternum GuardTM and Bone Wax group. The Sternum GuardTM and sterile 
drapes will be weighed before and after surgery to estimate the blood lost. 
 
3. Satisfaction Rate: The satisfaction rate will be evaluated using a questionnaire 
distributed to the surgeons. The questionnaire will contain overall satisfaction, 
ease of placement, maintenance of a dry field throughout the surgery, ease of 
removal; each of this question will have four different response which are 
satisfied, fairly satisfied, fairly dissatisfied, dissatisfied. Additionally, the 
surgeons will be asked about the experience in using Sternum GuardTM as 
compared to Bone Wax and it will contain 3 different response: worse, similar, 
better.  
 
3.11 Operational definition  
A. Control Group with Bone Wax: 
Group of patients who undergo cardiac surgery with the use of cardiopulmonary bypass 
and use Bone Wax to protect the sternum after median sternotomy.  
 
B. Treatment Group with Sternum GuardTM: 
Group of patients who undergo cardiac surgery with the use of cardiopulmonary bypass 
and use Sternum GuardTM to protect the sternum after median sternotomy.  
 
Table 1 - Table of Operational Definition 
 
Variable 
Definition 
Type 
of 
Data 
Code 
1 
Age 
The age of participant when 
undergo the cardiac surgery, it 
defines with calculated birth 
year taken from the medical 
record  
Numerik 
 
2 
Gender  
Gender which is included in 
this study are based one the 
Categorical  
1 = Male 
2 = Female 

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data recorded in the medical 
record.  
3 
Comorbid 
Data 
extracted 
from 
anamnesis and the medical 
record, with blood pressure 
≥140/90 mmHg and diabetes 
mellitus 
(Fasting 
Blood 
Glucose >126 mg/dL or 2 hr 
post prandial blood glucose or 
one time blood glucose >200 
mg/dL) 
Categorical 
1 = Yes 
2 = No 
6 
Cardiac 
Surgery 
Any cardiac surgery that are 
conducted in adult cardiac 
surgery division which are 
using 
cardiopulmonary 
bypass 
Categorical 
1 = CABG  
2 = Valve 
3 = CABG + 
Valve 
4 = Vascular        
7 
Surgical Site 
Infection 
Surgical site infection is 
divided 
by 
2 
categories 
(Superficial: infection occurs 
just in the area where the 
incision is made; Deep: occurs 
beneath the incision area in 
muscle 
and 
the 
tissues 
surrounding the muscle). It is 
evaluated at day 0, at the end 
of hospital stay, day 14 post – 
operative and day 30 post-
operative 
Categorical 
1 = Deep  
2 = Superficial 
8 
Sternal 
Dehiscence 
Occurs when there is an 
evidence 
of 
sternum 
separation. 
Often 
Categorical 
1 = Yes 
2 = No 

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accompanies 
with 
mediastinitis.  
9 
Haemostasis 
Effect 
The data obtained by quantity 
of blood lost from the sternal 
edges in Sternum GuardTM 
and Bone Wax group. The 
Sternum GuardTM and sterile 
drapes 
will 
be 
weighed 
digitally before and after 
surgery to estimate the blood 
lost.  
Numeric 
 
10 
Satisfaction 
Rate 
The result obtained by the 
questionnaire in both groups.  
 
Overall satisfaction rate 
 
Maintenance of a dry surgical 
field during intervention (both 
groups) 
 
Haemostatic effect 
 
Ease of insertion (Sternum 
GuardTM group) 
 
Ease of removal (Sternum 
GuardTM group) 
 
Categorical 
1 = Satisfied 
2 
= 
fairly 
satisfied 
3 
= 
fairly 
dissatisfied 
4 = dissatisfied 
 
 
 
12 
Experience 
satisfaction 
rate 
The result obtained by the 
questionnaire for the Sternum 
GuardTM  group.  
Categorical 
1 = worse 
2 = similar 
3 = better 

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13 
Uncontrolled 
Diabetes 
Mellitus  
A fasting plasma glucose 
(FPG) level of 126 mg/dL or 
higher, or a random plasma 
glucose of 200 mg/dL or 
higher, or hemoglobin A1c 
(HbA1c) level of 6.5% or 
higher.  
Categorical 
1 = yes  
2 = no  
14 
Uncontrolled 
Hypertension 
An average Systolic Blood 
Pressure of ≥140 mmHg or an 
average 
Diastolic 
Blood 
Pressure 
of 
≥90 
mmHg, 
among 
those 
with 
hypertension 
 
Categorical 
1 = yes  
2 = no  
 
 
 
3. 12 Ethics  
This study will be reviewed by the committee ethics in the National Cardiovascular 
Centre Harapan Kita. 
 
 
 
 
 
 
 
 
 
 
 

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3. 13 Research flow 
 
 
 
 
 
 
 
 

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3.14 Dummy table  
 
Participant Characteristic  
 
Table 2 - Dummy Table 1 
 
 
Sternum Guard TM 
Bone Wax 
 
N 
% 
N 
% 
Age ** 
 
 
 
 
Male * 
 
 
 
 
CABG * 
 
 
 
 
CABG + VALVE* 
 
 
 
 
VALVE * 
 
 
 
 
VASCULAR * 
 
 
 
 
Hypertension * 
 
 
 
 
Diabetes Mellitus * 
 
 
 
 
CPB 
time 
< 
60 
minutes * 
 
 
 
 
CPB 
time 
> 
60 
minutes * 
 
 
 
 
*) n(%) 
**) mean + SD  
 
Outcomes  
 
Table 3 - Dummy Table 2 
 
Sternum Guard TM 
Bone Wax 
Primary Outcomes  
N 
% 
N 
% 
Surgical Site Infection: 
 
 
 
 
Superficial * 
 
 
 
 
Deep * 
 
 
 
 
 
 
 
 
 
Sternal Dehiscence: 
 
 
 
 
Yes * 
 
 
 
 
No * 
 
 
 
 
 
 
 
 
 
Haemostasis 
Effect 
(gr)** 
 
 
 
 
 
 
 
 
 
Satisfaction Rates ** 
 
 
 
 
Satisfied 
 
 
 
 
Fairly satisfied 
 
 
 
 
Fairly dissatisfied 
 
 
 
 
Dissatisfied 
 
 
 
 
*) n(%) 
**) mean + SD 

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Appendix 
 
 
Table 4 - Time Schedule 
 
 
 
Activity  
Months (2019-2020) 
7 
8 
9 
10 
11 
12 
01 
02 
03 
1 
Literature Writing 
2 
Ethical Approval 
 
 
 
 
 
 
 
 
 
3 
Data extraction 
4 
Statistical Analysis 
5 
Result  
 
 
 
Cost Details:  
 
Table 5 – Resources fee 
 
Remarks: * (estimated fee) 
 
 
 
 
 
Resources 
 
Persons 
Fee/hours 
 
Hours/week 
Total 
hours 
Total Amount 
1.  Researcher 1 
Rp. 170.000* 
30 hours 
360 hours Rp. 61.200.000 
2. Assistant  
2 
Rp. 100.000* 
30 hours 
360 hours Rp. 36.000.000 
 
 
Total Amount  
Rp. 97.200.000 

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Table 6 - Materials Cost 
No 
Materials 
Pieces 
Price Per piece 
Total Amount 
1. 
Sternum GuardTM 
207 
Rp. 1,280,000 
Rp. 264.960.000 
(FREE FROM 
VYGON) 
2. 
Scale 
4 
Rp. 100,000 
Rp. 400,000 
 
Total Amount 
 
 
Rp. 400.000 
Table 7 - Operational Cost 
No 
Details 
Pieces 
Price per Piece 
Total Amount 
1.  
Stationery  
10 
Rp. 50,000 
Rp. 500,000 
2. 
Copies of Files 
500 
Rp. 500 
Rp. 250,000 
3. 
Miscellaneous (file holder, 
binder, printer ink jet, etc) 
200 
Varies (Rp. 
10.000 – Rp. 
400.000) 
Rp. 2,500,000 
 
Total Amount 
Rp. 3.250,000 
 
Table 8 - Total Amount 
 
 
 
 
 
 
 
 
Total Amount 
(Rp) 
Rp. 100.850.000 
Statement 
One hundred million and eight hundred and fifty thousand rupiah  

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Questionnaire for the Surgeons 
Efficacy of Sternum GuardTM in comparison of Bone Wax in Post Cardiac Surgery 
Patient: A Single Blind, Single Centre, Randomized Control Trial 
Research Principles: dr. Konda Kinanti Muroso, B.MedSc. ; Dr. dr. Dudy A Hanafy, Sp. BTKV (K) MARS. 
 
Please tick (Ö) the box accordingly; Please leave your comment(s) 
Section 1 
(Sternum Guard) 
Surgeon’s Satisfaction with Sternum Guard 
 
Satisfied 
Fairly 
Satisfied 
Fairly 
Dissatisfied 
Dissatisfied Comments 
Overall 
Satisfaction 
 
 
 
 
 
Ease of placement 
 
 
 
 
 
Maintenance of a 
dry field 
throughout the 
surgery 
 
 
 
 
 
Haemostasis effect   
 
 
 
 
Ease of removal 
 
 
 
 
 
 
 
 
 
 
 
Section 2 
Surgeon’s Experience in using Sternum Guard as opposed to Bone Wax  
 
Worse 
Similar 
Better 
 
Comments 
Experience of the 
surgeon in using 
Sternum Guard as 
compared to Bone 
Wax 
 
 
 
 
 
 
 
Comment(s): 
1.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Time and Date:                                                                                         Group: 
Investigator:  
 
Patient’s initial: 

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Questionnaire for the Surgeons 
Efficacy of Sternum GuardTM in comparison of Bone Wax in Post Cardiac Surgery 
Patient: A Single Blind, Single Centre, Randomized Control Trial 
Research Principles: dr. Konda Kinanti Muroso, B.MedSc. ; Dr. dr. Dudy A Hanafy, Sp. BTKV (K) MARS. 
 
 
 
 
 
Comment (s): 
1.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Time and Date:                                                                                         Group: 
Investigator:  
 
Patient’s initial: 
Section 1 (Bone Wax)  
Surgeon’s Satisfaction with Bone Wax 
 
Satisfied Fairly 
Satisfied 
Fairly 
Dissatisfied 
Dissatisfied 
Comments 
Overall Satisfaction 
 
 
 
 
 
Ease of placement 
 
 
 
 
 
Maintenance of a dry 
field throughout the 
surgery 
 
 
 
 
 
Haemostasis effect  
 
 
 
 
 
Ease of removal (if 
any)