Sternal fixation techniques following sternotomy for preventing sternal wound complications

  • Protocol
  • Intervention

Authors


Abstract

This is the protocol for a review and there is no abstract. The objectives are as follows:

To evaluate the efficacy and safety of sternal fixation techniques for preventing sternal wound complications following sternotomy .

Background

Description of the condition

The most frequent method for accessing the heart and coronary arteries during cardiac surgical procedures involves an incision along the length of the sternum (breastbone) in the midline, and the division of the sternum into two equal parts—right and left (median sternotomy). The standard closure technique after median sternotomy is to join the two parts using steel wires (i.e. figure-of-eight fashion wiring). However, this closure technique has been associated with several serious complications that have prompted surgeons to look for new closure methods. These complications include sternal instability (movement of the sternum at the site of sternal division), dehiscence (re-opening of the wound at the site of the sternal division), and mediastinitis (inflammation of the area below the sternum and between the right and left lungs, the mediastinum). These conditions represent the major causes of morbidity and mortality following cardiac surgery (Tekümit 2009). Infection rates after median sternotomy vary from 0.2% to 10%, and, in cases of infection, the morbidity and mortality rates vary from 5% to 25% (Landes 2007). The incidence of postoperative complications is more frequent with the following risk factors: thoracic radiation, obesity, diabetes, osteoporosis, chronic lung disease, immunosuppression, renal failure, hypertension, advancing age and chronic use of corticosteroids (Graeber 2004; Losanoff 2002; Molina 2004; Peivandi 2003).

New strategies for the closure of median sternotomies are being sought to minimise the incidence of infections and complications, however, an optimal technique has yet to be established (Fedak 2011; Imren 2006).

Description of the intervention

The traditional sternal closure method is performed with stainless steel wires using a simple transversal suture or figure-of-eight to join the two parts of the sternum. Alternative methods that have been developed include the following:

  • Titanium plate fixation: the titanium sternal fixation system consists of a transverse or longitudinal plate that is fixed with titanium self-tapping uni-lock screws (Huh 2008; Levin 2010; Voss 2008; Voss 2009). Transverse placement is thought to be associated with more complications in the long term (Voss 2008).

  • Modified parasternal (lateral sternal board) wire technique:  this technique places two additional wires on the sternal side in a longitudinal manner craniocaudally (from 'head to tail'), followed by the six transversely-placed wires routinely used in traditional closure methods (Sharma 2004). This approach reinforces the lateral sternal board to allow a good closure, and reduces sternal instability.

  • Bilateral pectoral muscle flaps: in this type of surgery, both of the pectoralis muscles from the right and left sides are brought to the middle of the thorax and then sutured above the sternal incision.

  • Sternal Talon: this new, rapid sternal fixation technique uses a titanium double-foot hook (talon) system that pulls the two sides of the sternum together using a ratchet mechanism. The mechanism is locked by a screw on the anterior surface. It is hoped that the Talon should eliminate the need for wires, plates or screws, reducing the incidence of postoperative complications and improving long-term stabilisation.

  • Nickel Titanium Naval Ordinance Laboratory (NITINOL) thermo reactive clips: nitinol is a metallic material composed of a mixture of approximately equal amounts of nickel and titanium. An applicator is used to pick up the clips and to fit them around the sternum.

  • Kirschner wires: these stainless steel pins are used to hold bone fragments together, and can be used in any type of bone closure, including standard sternotomy.

  • Posthorax vest: this is a post-operative support vest that is applied at 48 hours after the operation and has the appearance of an air jacket (Gorlitzer 2010).

  • Kryptonite biocompatible adhesive: this bone adhesive is applied in a thin layer on the trabecular interface (supportive structure) of the bone. The bone is cleaned with a sterile brush and irrigated with saline solution, before the adhesive is placed (Fedak 2011).

  • Robicsek-type closure: this closure uses double wires on each side of the sternum, followed by placement of circumferential wires with alternating posterior and anterior sutures that are passed from the costal cartilages down to the xiphoid process (Schimmer 2008).

All of these alternative closure methods have the disadvantage of being more labour intensive than the standard method, and so increase the surgical time and the cost of the intervention. Furthermore, Kirschner wires, which are inexpensive, can migrate to other sites in the body, and the posthorax vest can restrict breathing movements, which is particularly harmful in elderly patients.

How the intervention might work

Traditional closing is the fastest and easiest method to implement because the two edges of the sternum are approximate and tied to one another with steel wires. Alternative methods have been developed to minimise complications, thus increasing the chances of a robust sternal consolidation.

  • The posthorax vest provides an anteroposterior stabilisation towards the sternum instead of simple compression, while holding the two halves of the sternum in place (Gorlitzer 2010).

  • The kryptonite biocompatible adhesive allows healing by osteo-integration (fusing) with the host bone over time, without fibrosis or inflammation. It is a simple alternative to wire closure that may yield benefits with regard to functional recovery, respiratory function, incisional pain and analgesic requirements (Fedak 2011).

  • The Robicsek-type closure stabilises the sternum, prevents transversal wires from cutting bone, changes the site of pressure, and provides wider support (Schimmer 2008).

  • Kirschner wires have sharp edges and do not require bone drilling, which facilitates their placement.

Why it is important to do this review

As traditional closure techniques (i.e. steel wires) have been found to lead to a high rate of morbidity in certain groups of patients (e.g. obese, diabetic, and those with chronic obstructive pulmonary disease), evaluation of several other methods is increasing in attempts to reduce these complications. However, there is still much uncertainty regarding which method is best for managing this condition. Therefore, this review aims to present an overview of the current evidence related to the best approach to prevent sternal complications after median sternotomy.

Objectives

To evaluate the efficacy and safety of sternal fixation techniques for preventing sternal wound complications following sternotomy .

Methods

Criteria for considering studies for this review

Types of studies

We will include randomised controlled trials (RCTs), or, in the absence of RCTs, quasi-RCTs (RCTs in which allocation to treatment was obtained by alternation, use of alternate medical records, date of birth, or other predictable methods) in this systematic review.

Types of participants

All participants undergoing median sternotomy, regardless of gender, age, or race.

Types of interventions

We will consider any sternal fixation technique that aims to prevent sternal wound complications, such as the conventional sternal closure (i.e. figure-of-eight-fashion wiring); nitinol thermo reactive clips; Kirschner wires; sternal plating with pectoralis advancement flaps; titanium plate fixation; post thorax vest; absorbable, transverse sternal plating; adhesive-enhanced closure (i.e. Kryptonite biocompatible adhesive); and Robicsek-type closure. The interventions will be compared against each other.

Types of outcome measures

Primary outcomes

Primary outcomes will include the following.

  • Wound dehiscence.

  • Deep sternal wound infection (DSWI).

Both will be measured by clinical history, physical examination, laboratory tests or image techniques, or both. We will consider an early stage follow-up point (i.e. within 30 days), and a later stage follow-up point (i.e. after 30 days).

Secondary outcomes

Secondary outcomes will include the following.

  • Uneventful healing.

  • DSWI-related death and all-case mortality.

  • Chest pain related to procedure.

  • Sternal instability measured by clinical history, physical examination and/or image techniques.

  • Mediastinitis detected by image techniques.

  • Postoperative health-related quality of life measured by any validated measurement scale, however defined by authors.

  • Period of mechanical ventilation.

  • Duration of stay in the intensive care unit.

  • Thoracic deformation such as asymmetries, bulging and retractions.

  • Incidence of pneumonia.

  • Length of hospital stay.

  • Re-operation.

Search methods for identification of studies

Electronic searches

We will search the following electronic databases to identify reports of relevant randomised clinical trials:

  • The Cochrane Wounds Group Specialised Register;

  • The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library) (Latest issue);

  • Ovid MEDLINE (1946 to present);

  • Ovid EMBASE (1974 to present);

  • EBSCO CINAHL (1982 to present);

  • LILACS (1982 to present).

We will use the following provisional search strategy in The Cochrane Central Register of Controlled Trials (CENTRAL):

#1 MeSH descriptor: [Thoracic Surgery] explode all trees
#2 MeSH descriptor: [Cardiac Surgical Procedures] explode all trees
#3 MeSH descriptor: [Sternotomy] explode all trees
#4 MeSH descriptor: [Sternum] explode all trees and with qualifiers: [Surgery - SU]
#5 [mh thorax] and [mh /SU]
#6 ((cardiac next surg*) or (thoracic surg*)):ti,ab,kw
#7 sternotomy:ti,ab,kw
#8 {or #1-#7}
#9 MeSH descriptor: [Suture Techniques] explode all trees
#10 MeSH descriptor: [Surgical Fixation Devices] explode all trees
#11 ((closure next method*) or (closure next technique*) or (sternal next closure*) or "sternal fixation" or "surgical fixation"):ti,ab,kw
#12 ((titanium next plate*) or "wire" or "wires" or "Sternal Talon" or "Nickel Titanium Naval Ordinance Laboratory" or NITINOL or "clip" or "clips" or "vest" or "vests" or Robicsek):ti,ab,kw
#13 {or #9-#12}
#14 MeSH descriptor: [Surgical Wound Infection] explode all trees
#15 MeSH descriptor: [Surgical Wound Dehiscence] explode all trees
#16 (surg* near/5 infect*):ti,ab,kw
#17 (surg* near/5 wound*):ti,ab,kw
#18 (surg* near/5 site*):ti,ab,kw
#19 (surg* near/5 incision*):ti,ab,kw
#20 (surg* near/5 dehisc*):ti,ab,kw
#21 (wound* near/5 dehisc*):ti,ab,kw
#22 (wound near/5 disrupt*):ti,ab,kw
#23 (wound next complication*):ti,ab,kw
#24 {or #14-#23}
#25 #8 and #13 and #24

We will adapt this strategy to search Ovid MEDLINE, Ovid EMBASE and EBSCO CINAHL. We will combine the Ovid MEDLINE search with the Cochrane Highly Sensitive Search Strategy for identifying randomised trials in MEDLINE: sensitivity- and precision-maximising version (2008 revision) (Lefebvre 2011). We will combine the EMBASE search with the Ovid EMBASE filter developed by the UK Cochrane Centre (Lefebvre 2011). We will combine the CINAHL searches with the trial filters developed by the Scottish Intercollegiate Guidelines Network (SIGN 2013). We will not restrict studies with respect to language, date of publication or study setting.

We will search the following clinical trials registries:

Searching other resources

We will check the reference lists of all relevant studies we identify for additional relevant citations. We will contact study authors, experts and manufacturers to identify unpublished data.

Data collection and analysis

Selection of studies

Independently, two review authors (KFP and DC) will screen the trials identified by the literature search. They will resolve disagreements by consulting with the other review authors (AC and RED), and also consult them regarding quality assurance of the review processes. After this initial assessment, the same review authors (KFP and DC) will obtain full versions of articles that appear to match the inclusion criteria. They will delete duplicate publications that have been identified from different electronic databases.

Data extraction and management

Independently, two review authors (KFP and DC) will extract data and resolve any discrepancies by discussion. The authors will use a standard data extraction form to extract the following information: characteristics of the study (design, methods of randomisation); participants (numbers, age, setting, inclusion and exclusion criteria); interventions; outcomes (types of outcome measures, adverse events). They will then check for errors before entering the data into the review writing software, Review Manager (RevMan) 5.2 (Review Manager 2012).

Assessment of risk of bias in included studies

We will assess study quality by using the 'Risk of bias' tool for Cochrane reviews (Higgins 2011). We will use the following six separate criteria, and grade each according to the standards explained below.

  • Random sequence generation

 - Low risk of bias: sequence generation was achieved using computer random-number generation or a random-number table. Drawing lots, tossing a coin, shuffling cards, and throwing dice are adequate, if performed by an independent adjudicator.
- Uncertain risk of bias: the trial is described as randomised, but the method of sequence generation was not specified.
- High risk of bias: the sequence generation method was not, or may not have been, random. Quasi-randomised studies, those using dates, names, or admittance numbers in order to allocate patients are inadequate and will only be included in the review in the absence of RCTs

  • Allocation concealment

- Low risk of bias: allocation was controlled by a central and independent randomisation unit, sequentially-numbered, opaque and sealed envelopes or similar, so that intervention allocations could not have been foreseen in advance of, or during, enrolment.
- Uncertain risk of bias: the trial was described as randomised, but the method used to conceal the allocation was not described, so intervention allocations may have been foreseen in advance of, or during, enrolment.
- High risk of bias: if the allocation sequence was known to the investigators who assigned participants, or if the study was quasi-randomised. Quasi-randomised studies will be excluded from the review for the assessment of benefits, but not for assessment of harms.

  • Blinding of participants and personnel

It is difficult to blind personnel for this type of intervention. So, we will classify the primary outcomes as being at high risk of bias, as a surgeons’s belief may influence the reporting of sternal dehiscence and deep sternal wound infection. However, it is possible to blind the participants, so we will consider outcomes that are not reported by hospital staff as follows.

- Low risk of bias: blinding was performed adequately, or the outcome measurement was not likely to be influenced by lack of blinding.
- Uncertain risk of bias: there is insufficient information to assess whether the type of blinding used was likely to induce bias on the estimate of effect.
- High risk of bias: no blinding or incomplete blinding, and the outcome or the outcome measurement was likely to be influenced by lack of blinding.

  • Blinding of outcome assessors

- Low risk of bias: blinding was performed adequately, or the outcome measurement is not likely to be influenced by lack of blinding.
- Uncertain risk of bias: there is insufficient information to assess whether the type of blinding used is likely to induce bias on the estimate of effect.
- High risk of bias: no blinding or incomplete blinding, and the outcome or the outcome measurement is likely to be influenced by lack of blinding.

  • Incomplete outcome data

- Low risk of bias: the underlying reasons for missing data were unlikely to make treatment effects depart from plausible values, or proper methods were employed to handle missing data.
- Uncertain risk of bias: there is insufficient information to assess whether the missing data mechanism in combination with the method used to handle missing data are likely to induce bias on the estimate of effect.
- High risk of bias: the crude estimate of effects (e.g. complete case estimate) will clearly be biased due to the underlying reasons for missing data, and the methods used to handle missing data were unsatisfactory.

  • Selective outcome reporting

- Low risk of bias: pre-defined, or clinically relevant and reasonably expected outcomes are reported. We will also search for trial protocols and compare the outcomes that were pre-defined in them with those reported in the publication.
- Uncertain risk of bias: it is unclear whether data for these outcomes were recorded or not.
- High risk of bias: one or more clinically relevant and reasonably expected outcomes were not reported; data on these outcomes were likely to have been recorded.

We will assess all included trials for risk of bias. If the risk of bias in a trial is judged as 'low' in all the listed above domains, the trial will fall in the 'low risk of bias' group of trials. If the risk of bias in the assessed trials is judged as 'uncertain' or 'high' in one or more of the specified domains, then the trial will fall in the 'high risk of bias' group of trials.

Initially, relevant information for making a judgment about a criterion will be copied from the original publication into an assessment table. If additional information is available from study authors, this will also be entered in the table along with an indication that this is unpublished information. Two review authors (KFP and RED) will make a judgment independently as to whether the risk of bias for each criterion was considered to be 'low', 'uncertain', or 'high'. We will resolve disagreements by discussion.

We will record this information for each included trial in ’Risk of bias’ tables in RevMan, and summarise the risk of bias for each trial in a summary ’Risk of bias’ figure and graph.

Measures of treatment effect

(a) Binary outcomes
For dichotomous data such as number of sternal dehiscence, we will use the risk ratio (RR) as the effect measure with 95% confidence intervals (CI).

(b) Continuous outcomes
For continuous data such as reductions in duration of stay in the intensive care unit and in hospital, we will present the results as mean differences (MD) with 95% confidence intervals (CI). When pooling data across studies we will estimate the mean difference (MD), if the outcomes are measured in the same way across trials. We will use the standardised mean difference (SMD) to combine trials that measure the same outcome, but use different methods.

(c) Time-to-event data
Time to complete healing of sternal dehiscence is time-to-event data. The most appropriate way of summarising this type of data is to use methods used in survival analysis and to express the intervention effect as a hazard ratio.

Unit of analysis issues

The unit of analysis will be each person recruited into the trials.

Dealing with missing data

An intention-to-treat analysis (ITT) is one in which all the participants of a trial are analysed according to the intervention to which they were allocated, whether they received the intervention, or not. We will assume that participants who dropped out of trials are either non-respondents (people who fail to heal, i.e. worst case scenario) or respondents (people who heal, i.e. best case scenario). For each trial we will report whether or not the investigators stated whether the analysis was performed according to the ITT principle. If participants were excluded after allocation, we will report in full any details provided. For the worst case scenario we will consider the drop outs as non-respondents and we will treat those participants who were not included in the analysis as if their sternal dehiscence did not heal. For the best case scenario, we will consider the drop outs as respondents and we will treat these participants who are not included in the analysis as if their sternal dehiscence did heal. Where trials report results for participants who complete the trial without specifying the numbers initially randomised to each group, we will present only complete case data. For other outcomes we will present data for all people randomised, where reported; otherwise we will base estimates on complete cases only.

Assessment of heterogeneity

We will look for clinical heterogeneity by examination of the study details, and then test for statistical heterogeneity between trial results using the Chi2 test and the I2 value. We will consider a P value of 0.1 as significant (Deeks 2011). We will classify heterogeneity using the following I2 values and meta-analyse regardless of the values for statistical heterogeneity.

• 0 to 40%: might not be important.
• 30% to 60%: may represent moderate heterogeneity.
• 50% to 90%: may represent substantial heterogeneity.
• 75% to 100%: considerable heterogeneity.

If included studies are not sufficiently homogeneous to combine in a meta-analysis, but they are all favourable to a specific intervention, we will plot them.

To avoid heterogeneity, we will also separate meta-analyses according to the different sternal fixation techniques employed.

The following factors will be investigated as potential causes of heterogeneity.

• Clinical diversity, e.g. study location and setting, characteristics of participants, co-morbidity and treatments participants may be receiving at trial entry, definition of outcomes and main outcomes.
• Methodological diversity, e.g. assessment of randomisation process, risk of bias and analytical method (ITT versus treated).
• Statistical diversity: this will be explored initially by looking at the estimates of treatment effect of included studies and considering whether we are confident that a combined estimate will give a meaningful description

First we will consider whether study population (age and baseline characteristics) and the interventions are sufficiently similar. If this is the case, we will assess statistical heterogeneity either by using a forest plot to assess whether confidence intervals (CIs) from individual study estimates overlap, or by using the I2 statistic, which examines the percentage of total variation across studies due to heterogeneity rather than to chance (Higgins 2003).

Assessment of reporting biases

In addition to assessing the risk of selective outcome reporting as part of the 'Risk of bias' assessment, we will assess the likelihood of potential publication bias using funnel plots, provided that there are at least ten trials (Sterne 2011). When small studies in a meta-analysis tend to show larger treatment effects, other causes will be considered including; selection biases, poor methodological quality, heterogeneity and chance (Sterne 2011).

Data synthesis

We will analyse the data using RevMan 5.2 software provided by the Cochrane Collaboration. We will use a fixed-effect model for meta-analysis in the absence of clinical, methodological and statistical heterogeneity. Additionally, if the I2 value is greater than zero, we will apply a random-effects model to see whether the conclusions differ, and any difference will be noted. If pooling is not possible or appropriate, we will present a narrative summary (Deeks 2011).

Subgroup analysis and investigation of heterogeneity

Subgroup analyses are secondary analyses in which the participants are divided into groups according to shared characteristics, and outcome analyses are then conducted to determine whether there are any significant treatment effects that are related to that characteristic. If data permit, we will carry out the following subgroup analyses.

  • Age: adults (18 years or older) versus children (under 18 years of age).

  • High risk populations (i.e. 90% or more of participants with risk factors such as obesity, diabetes, osteoporosis, chronic pulmonary lung disease, immunosuppression) versus low risk populations (i.e. 10% or less of participants with risk factors).

  • Underlying reason for surgery (e.g. coronary versus valve surgery; cardiac versus non-cardiac surgery).

  • Elective versus emergency procedures.

Sensitivity analysis

If there are an adequate number of studies, we will perform a sensitivity analysis to explore the robustness of the results. Only studies at low risk of bias will be considered in a sensitivity analysis. Studies with inadequate allocation concealment; achieving inadequate follow-up and where outcome assessment was unblinded or where blinding of outcome assessment was uncertain, will be considered as being of high risk of bias.

Summary of findings tables

We will use the principles of the GRADE system to assess the strength of evidence of the body of evidence associated with specific outcomes in our review and construct a 'Summary of findings' table using the GRADE software (Guyatt 2008). The GRADE approach appraises the quality of a body of evidence based on the extent to which one can be confident that an estimate of effect or association reflects the item being assessed. The quality of a body of evidence considers within-study risk of bias (methodologic quality), the directness of the evidence, heterogeneity of the data, the precision of effect estimates, and the risk of publication bias. The specific outcomes we will consider for GRADE are wound dehiscence and DSWI.

Acknowledgements

We would like to thank Sally Bell-Syer (Managing Editor), Dirk Ubbink (editor), Ruth Foxlee (Trials Search Co-ordinator), Susanne Hempel (methodologist), Giovanni Casazza (statistics editor), Mark Dayer (expert referee), Derick Mendonca (expert referee), and Shirley Manknell (consumer referee) for their help during the preparation of this protocol. In addition the copy editor Elizabeth Royle.

Contributions of authors

Regina El Dib: conceived the review question; developed and co-ordinated development of the protocol; performed part of the writing and completed the first draft; edited and made an intellectual contribution to the protocol; provided advice and approved final submission of the protocol, and acts as guarantor.
Karin Pinotti: conceived the review question; developed, performed part of the writing, and completed the first draft of the protocol; edited and made an intellectual contribution to the protocol; provided advice and approved final submission of the protocol.
Daniele Cataneo: conceived the review question; developed, performed part of the writing, and completed the first draft of the protocol; edited and made an intellectual contribution to the protocol; provided advice and approved final submission of the protocol.
Olavo Ribeiro: developed and completed the first draft of the protocol; made an intellectual contribution to the protocol, and provided advice.
Antonio Cataneo: conceived the review question and secured funding for the review; developed, performed part of the writing, and completed the first draft of the protocol; edited and made an intellectual contribution to the protocol; provided advice and approved final submission of the protocol; and acts as guarantor.

Contributions of editorial base:

Nicky Cullum: edited the protocol; advised on methodology, interpretation and protocol content.
Joan Webster, Editor: approved the final protocol prior to submission.
Sally Bell-Syer: coordinated the editorial process. Advised on methodology, interpretation and content. Edited the protocol.
Ruth Foxlee: designed the search strategy and edited the search methods section.
Rachel Richardson: checked the final draft protocol.

Declarations of interest

Karin Pinotti: none known
Regina El Dib: none known
Leandro Ramos Silva: none known
Daniele Cataneo: none known
Olavo Ribeiro: none known
Antonio Cataneo: none known

Sources of support

Internal sources

  • By our own, Brazil.

External sources

  • The National Institute for Health Research (NIHR) is the sole funder of the Cochrane Wounds Group, UK.

Ancillary