Biomechanical comparison of median sternotomy closures

Improving Sternal Closure Outcomes in Cardiac Surgery: Polyethylene Suture Tapes vs. Steel Wires

Background: Steel wires are often inadequate for sternal closure for patients at high risk of sternal complications. This study compares a novel sternal closure system to conventional steel wires to assess its potential to reduce sternal complication rates and improve clinical outcomes. Methods: A retrospective study was conducted on 300 consecutive patients undergoing cardiac surgery via median sternotomy. A total of 150 patients underwent steel wire sternal closure, while 150 underwent suture tape closure. Preoperative, intraoperative, and postoperative data were collected and analyzed for both groups. Results: Rates of sternal wound infections (1% vs. 5%, p = 0.0363) and sternal dehiscence (0% vs. 5%, p = 0.0297) were lower in the suture tape group. Suture tape patients had significantly less pain at 14 and 30 days (p = 0.0002 and 0.0071). The requirement for sternal protection adjuncts was eliminated with suture tape closure. Sternal closure time was significantly shorter in the suture tape group (11 vs. 19 min, p < 0.0001). Conclusions: Suture tapes proved safe, feasible, and effective for sternal closure, demonstrating significant advantages for sternal closure over steel wires, with reduced rates of sternal dehiscence, infection, postoperative incisional pain, and closure time. These superior outcomes and the elimination of sternal protection adjuncts can potentially reduce healthcare costs. Our experiences suggest that this novel sternal closure system has significant potential, with larger prospective studies warranted to optimize sternal closure strategies.

Partial coverage adhesive augmented sternal fixation and stabilization: A biomechanical analysis

Adhesive-augmented sternal fixation (AASF) has been investigated as an alternative to the clinical standard of cerclage wires; however, previous studies have focused on a full adhesive layer across the sternal midline, which acts as a barrier to bone healing. This study used a human cadaveric model to investigate if partial coverage AASF used in combination with wired fixation could provide adequate stability. Median sternotomies were performed on fifteen human cadaveric sterna. Three groups (n = 5) with varying adhesive coverage (50 %, 62.5 %, 75 %) of the sternal midline and traditional wiring were investigated. Cyclic lateral distraction loading of 10 N to 100 N was applied at 50 N/s. Every 30 cycles, the maximum load was increased by 100 N to a maximum of 500 N. Displacement was measured using transducers spanning the transection line at the manubrium, body, and xiphoid. Mean maximum total displacement (MMTD) for all groups was significantly below 2 mm (p < 0.001) with 1.49 mm ± 0.82 mm, 0.97 mm ± 0. 55 mm, and 0.67 mm ± 0.65 mm in the 50 %, 62.5 %, and 75 % groups respectively. MMTD in the 50 % group was significantly greater than MMTD in the 62.5 % and 75 % groups. AASF improved stability as coverage of the sternal surface with adhesive increased. Partial coverage of the sternal midline with adhesive may provide similar rigidity to a full layer while enabling earlier sternal ossification at the transection line compared to wiring alone.

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.

Biomechanical comparison of bone staple fixation methods with suture material for median sternotomy closure using 3D-printed bone models

AIM

To compare the biomechanical properties of three different sternal closure techniques in a 3D-printed bone model of a sternum from a 30-kg dog.

METHODS

Median sternotomy was performed on a total of 90 three-dimensional (3D) copies of a polycarbonate (PC) model of a sternum, generated from the CT images of the sternum of a 30-kg German Shepherd dog. Three different methods were used to repair the sternotomies: polydioxanone suture (group PDS, n = 30), stainless steel bone staples (group SS, n = 30), and nitinol bone staples (group NS, n = 30). Each repair method was tested by applying tensile force in one of three ways (longitudinally, laterally, or torsionally) resulting in a sample size of n = 10 for each repair method-loading combination. In all experiments, the loads at 1-mm and 2-mm gap formation, failure, and the displacement at the failure point were measured.

RESULTS

In lateral distraction and longitudinal shear tests, NS and SS staple repairs required application of significantly greater force than PDS across all displacement criteria (1 and 2 mm). NS exhibited significantly greater failure load than PDS. In torsion tests, NS required significantly greater application of force compared to SS or PDS at all displacement criteria (1 and 2 mm) and exhibited a greater failure load than PDS. In terms of displacement at failure point, PDS suture showed more displacement than SS or NS across all experiments (laterally, longitudinally, torsionally).

CONCLUSIONS

In this study, bone staples were mechanically superior to PDS suture in median sternotomy closure using 3D-printed bone model in terms of 1-mm, 2-mm displacement loads, and displacement at failure. NS had a higher failure load than PDS under lateral, longitudinal, and torsional distraction.

CLINICAL RELEVANCE

These study results imply that bone staples can be considered as an alternative surgical method for median sternotomy closure in dogs.

Biomechanical comparison of canine median sternotomy closure using suture tape and orthopedic wire cerclage

OBJECTIVE

To compare the mechanical properties of suture tape and orthopedic wire cerclage in an ex vivo canine median sternotomy model.

STUDY DESIGN

Ex vivo.

ANIMALS

Twelve large-breed canine cadaveric sternums.

METHODS

Median sternotomies were performed, leaving the manubrium intact. The specimens were randomly assigned to group W (20-gauge stainless steel orthopedic wire cerclage in a figure-of-eight pattern) or group ST (suture tape in a figure-of-eight pattern). Each specimen was laterally distracted until failure using an electrodynamic materials-testing system.

RESULTS

No differences were observed for displacement, yield load, maximum load, implant failure between the groups. The orthopedic wire construct was stiffer than the suture tape construct.

CONCLUSION

Suture tape was biomechanically similar to orthopedic wire cerclage for sternotomy closure in dogs, although wire constructs were stiffer.

CLINICAL SIGNIFICANCE

Suture tape may represent an alternative to cerclage wire for sternotomy closure in dogs. Additional studies evaluating its clinical use are needed.

Trunk stabilising exercises promote sternal stability in patients after median sternotomy for heart valve surgery: a randomised trial

QUESTION

What is the effect of trunk stabilising exercises on sternal stability in women who have undergone heart valve surgery via median sternotomy?

DESIGN

Randomised controlled trial with concealed allocation, assessor blinding and intention-to-treat analysis.

PARTICIPANTS

Thirty-six women aged 40 to 50 years who had undergone heart valve surgery via median sternotomy 7 days before enrolment.

INTERVENTION

All participants in both groups received cardiac rehabilitation during hospitalisation and three times per week for 4 weeks after discharge. In addition, participants in the experimental group were prescribed a regimen of trunk stabilising exercises to be performed three times per week for 4 weeks. At each exercise session, each of 11 exercises were to be performed with five to ten repetitions.

OUTCOME MEASURES

The primary outcome was sternal separation (the distance between the two halves of the bisected sternum). The secondary outcome was the Sternal Instability Scale from 0 (no instability) to 3 (an unstable sternum with substantial movement or separation). Measures were taken before and after the 4-week intervention period.

RESULTS

After the 4-week intervention period, the experimental group had a greater decrease in sternal separation by 0.09 cm (95% CI 0.07 to 0.11). The experimental group was twice as likely to improve by at least one grade on the Sternal Instability Scale by 4 weeks (RR 2.00, 95% CI 1.07 to 3.75). The experimental group was almost three times as likely to have a clinically stable sternum (grade 0 on the Sternal Instability Scale) by 4 weeks (RR 2.75, 95% CI 1.07 to 7.04).

CONCLUSION

Trunk stabilising exercises were an effective and feasible method of promoting sternal stability in women who underwent heart valve surgery via median sternotomy.

TRIAL REGISTRATION

NCT04632914.

Review of Biomechanical Studies and Finite Element Modeling of Sternal Closure Using Bio-Active Adhesives

The most common complication of median sternotomy surgery is sternum re-separation after sternal fixation, which leads to high rates of morbidity and mortality. The adhered sternal fixation technique comprises the wiring fixation technique and the use of bio-adhesives. Adhered sternal fixation techniques have not been extensively studied using finite element analysis, so mechanical testing studies and finite element analysis of sternal fixation will be presented in this review to find the optimum techniques for simulating sternal fixation with adhesives. The optimal wiring technique should enhance bone stability and limit sternal displacement. Bio-adhesives have been proposed to support sternal fixation, as wiring is prone to failure in cases of post-operative problems. The aim of this paper is to review and present the existing numerical and biomechanical sternal fixation studies by reviewing common sternal closure techniques, adhesives for sternal closure, biomechanical modeling of sternal fixation, and finite element modeling of sternal fixation systems. Investigating the physical behavior of 3D sternal fixation models by finite element analysis (FEA) will lower the expense of conducting clinical trials. This indicates that FEA studies of sternal fixation with adhesives are needed to analyze the efficiency of this sternal closure technique virtually.

Chitosan Scaffold Containing Periostin Enhances Sternum Bone Healing and Decreases Serum Level of TNF-α and IL-6 after Sternotomy in Rat

BACKGROUND

In the aftermath of bone injuries, such as cranium and sternum, bone wax (BW) is used to control bleeding from the bone surfaces during surgery. Made up of artificial substances, however, it is associated with many complications such as inflammation, increased risk for infection, and bone repair delay. We, therefore, in this study set out to design and evaluate a novel BW without the above-mentioned side-effects reported for other therapies.

METHODS

The pastes (new BW(s)) were prepared in the laboratory and examined by MTT, MIC, MBC, and degradability tests. Then, 60 adult male Wistar rats, divided into six equal groups including chitosan (CT), CT-octacalcium phosphate (OCP), CT-periostin (Post), CT-OCP-Post, Control (Ctrl), and BW, underwent sternotomy surgery. Once the surgeries were completed, the bone repair was assessed radiologically and thereafter clinically in vivo and in vitro using CT-scan, H&E, ELISA, and qRT-PCR.

RESULTS

All pastes displayed antibacterial properties and the CT-Post group had the highest cell viability compared to the control group. In contrast to the BW, CT-Post group demonstrated weight changes in the degradability test. In the CT-Post group, more number of osteocyte cells, high trabeculae percentage, and the least fibrous connective tissue were observed compared to other groups. Additionally, in comparison to the CT and Ctrl groups, higher alkaline phosphatase activity, as well as decreased level of serum tumor necrosis factor-α, interleukin-6, and OCN in the CT-Post group was evident. Finally, Runx2, OPG, and RANKL genes' expression was significantly higher in the CT-Post group than in other groups.

CONCLUSION

Our results provide insights into the desirability of pastes in terms of cellular viability, degradability, antibacterial properties, and surgical site restoration compared to the BW group. Besides, Periostin could enhance the osteogenic properties of bone tissue defect site.

Development and Validation of a Physiological Testing Method for Sternal Closure Systems

After a median sternotomy, the sternal bone has to be refixated using implants such as wires, plates or clamps. However, there is still a lack of specifically applicable test methods to investigate the mechanical safety and effectiveness of such implant systems. The aim of this study was to develop a new test method that replicates the in vivo loads acting on the sternum and that is applicable to all types of sternal closure systems.

Based on the scientific literature a setup was developed that incorporates the physiological loads acting on the sternum during breathing (91 N) and coughing (328 N). These loads are applied to a sternum replicate at 5 Hz for approximately 1.8 million cycles. This cycle number is assumed to represent the healing period. For validation, the new method was applied to two different sternal closure systems: a PEEK clamp system and wires.

The new test method proved to be easily applicable. The validation tests with the two sternal closure systems showed reasonable and reproducible results regarding all outcome parameters. The pre-tension exerted by the implants significantly differed between the two implant groups and decreased after the first coughing cycles. The fracture gap separation during breathing also significantly different between the two test groups but it was similar during coughing. No implant failed.

Using this new test method it is possible to compare sternal closure systems under reproducible conditions and interpret their mechanical characteristics regarding their in vivo safety and effectiveness.

Comparison of polyetheretherketone cables and stainless steel wires for sternal fixation after median sternotomy

Objective

To compare the sternal fixation effect of a polyetheretherketone (PEEK) cable product and stainless steel wire after median sternotomy.

Methods

A multicentre retrospective clinical trial was conducted in patients that underwent median sternotomy for a range of surgical reasons. The sternum was fixed using PEEK sternal cables in the experimental group and stainless steel wires in the control group. The general patient state, product manoeuvrability, bone and wound healing state and blood test results were evaluated at seven visits during the preoperative, surgical and follow-up periods.

Results

A total of 108 patients (54 in each group) were included in the analysis at the final 180-day follow-up. The sternum was successfully closed using PEEK cables or steel wires in all patients and all healed well. No pathological changes were found on the X-ray imaging. Computed tomography imaging confirmed ideal fracture healing. No significant difference was found between the experimental group and the control group in outcomes.

Conclusion

PEEK cables are easy to implant and show desirable effectiveness in sternal fixation without any observed side-effects.

Non-tumorous diseases of the sternum and its articulations: At the front gate of the chest

Abnormalities of the sternal and peri-sternal regions are commonly seen in clinical practice and may be one of the important causes of chest pain particularly anterior chest wall pain. While reading computed tomography (CT) of the chest for evaluation of chest pain, the sternal region is either easily overlooked or its abnormality is often detected incidentally. This article will provide an overview of normal sternal anatomy and congenital variants as well as a variety of non-tumorous pathologic conditions of the sternum and adjacent joints, with emphasis on CT, to help radiologists, particularly thoracic radiologists, to make an accurate diagnosis in their daily practice. Non-tumorous abnormalities include trauma (fractures and dislocations), infection (osteomyelitis, septic arthritis), degenerative (osteoarthritis) and inflammatory conditions (rheumatoid arthritis, seronegative arthritides), and metabolic disorders (Paget's disease and renal osteodystrophy) as well as treatment related changes such as poststernotomy and its complications (dehiscence, nonunion) and postradiation changes of the sternum.

Orthopedic Principles to Facilitate Enhanced Recovery After Cardiac Surgery

Enhanced recovery after surgery (ERAS) protocols recognize early postoperative mobilization as a driver of faster postoperative recovery, return to normal activities, and improved long-term patient outcomes. For patients undergoing open cardiac surgery, an opportunity for facilitating earlier mobilization and a return to normal activity lies in the use of improved techniques to stabilize the sternal osteotomy. By following the key orthopedic principles of approximation, compression, and rigid fixation, a more nuanced approach to sternal precaution protocols is possible, which may enable earlier patient mobilization, physical rehabilitation, and recovery.

Wire-based sternal closure: MRI-related heating at 1.5 T/64 MHz and 3 T/128 MHz based on simulation and experimental phantom study

PURPOSE

The paper investigates factors that affect the RF-induced heating for commonly used wire-based sternal closure under 1.5 T and 3 T MRI systems and clarifies the heating mechanisms.

METHODS

Numerical simulations based on the finite-difference time-domain method and experimental measurements in ASTM (American Society for Testing and Materials) phantom were used in the study. Various configurations of the wire-based sternal closure in the phantom were studied based on parameter sweeps to understand key factors related to the RF-induced heating. In vivo simulations were further performed to explore the RF-induced heating in computational human phantoms for clinically relevant scenarios.

RESULTS

The wire-based sternal closure can lead to peak 1-g averaged spatial absorption ratio of 106.3 W/kg and 75.2 W/kg in phantom and peak 1-g averaged specific absorption rate of 32.1 W/kg and 62.1 W/kg in computational human models near the device at 1.5 T and 3 T, respectively. In phantom, the simulated maximum temperature rises for 15-minute RF exposure are 9.4°C at 1.5 T and 5.8°C at 3 T. Generally, the RF-induced heating will be higher when the electrical length of the device is close to the resonant length or when multiple components are spaced closely along the longitudinal direction.

CONCLUSION

The RF-induced heating related to wire-based sternal closure can be significant due to the antenna effect and capacitive mutual coupling effect related to the specific geometries of devices.

Total arterial myocardial revascularization using bilateral internal mammary arteries and the role of postoperative sternal stabilization to reduce wound infections in a large cohort study

OBJECTIVES

Total arterial myocardial revascularization using bilateral internal mammary arteries shows improved results for mortality, long-term survival and superior graft patency. It has become the standard technique according to recent guidelines. However, these patients may have an increased risk of developing sternal wound infections, especially obese patients or those with diabetes. One reason for the wound complications may be early sternum instability. This situation could be avoided by using a thorax support vest (e.g. Posthorax® vest). This retrospective study compared the wound complications after bilateral internal mammary artery grafting including the use of a Posthorax vest.

METHODS

Between April 2015 and May 2017, 1613 patients received total arterial myocardial revascularization using bilateral internal mammary artery via a median sternotomy. The Posthorax support vest was used from the second postoperative day. We compared those patients with 1667 patients operated on via the same access in the preceding 26 months. The end points were the incidence of wound infections, when the wound infection occurred and how many wound revisions were needed until wound closure.

RESULTS

The demographic data of both groups were similar. A significant advantage for the use of a thorax support vest could be seen regarding the incidence of wound infections (P = 0.036) and the length of hospital stay when a wound complication did occur (P = 0.018).

CONCLUSIONS

As seen in this retrospective study, the early perioperative use of a thorax stabilization vest, such as the Posthorax vest, can reduce the incidence of sternal wound complications significantly. Furthermore, when a wound infection occurred, and the patient returned to the hospital for wound revision, patients who were given the Posthorax vest postoperatively had a significantly shorter length of stay until wound closure.

Feasibility of primary sternal plating for morbidly obese patients after cardiac surgery

BACKGROUND

Morbidly obese patients (body mass index [BMI] ≥ 35 kg/m2) who undergo cardiac surgery involving median sternotomy have a higher-than-normal risk of sternal dehiscence. To explore a potential solution to this problem, we examined the utility of transverse sternal plating for primary sternal closure in morbidly obese cardiac surgical patients.

METHODS

We retrospectively reviewed data from cardiac surgical patients who underwent single primary xiphoid transverse titanium plate reinforcement for primary sternal closure from August 2009 to July 2010 (n = 8), and we compared their outcomes with those of patients with BMI ≥35 kg/m2 who underwent cardiac surgery without sternal plate reinforcement from April 2008 to July 2009 (n = 14). All cases were performed by the same surgeon.

RESULTS

The 2 groups of patients had similar demographics and comorbidities (P > 0.05 for all). All patients with sternal plate reinforcement reported sternal stability at last follow-up (at a median of 27 months postoperatively; range, 8.4-49.3 months), whereas 1 patient (7.1%) who underwent standard closure developed sterile sternal dehiscence (P = 0.4). Postoperative patient-controlled analgesia (PCA) morphine usage was significantly higher for patients without sternal plate reinforcement than for patients who had sternal plate reinforcement (3.6 mg/h vs 1.3 mg/h, P = 0.008). No patient in the sternal plate group had wound seroma or perioperative complications attributable to sternal closure technique.

CONCLUSION

Single xiphoid transverse plate reinforcement for primary sternal closure is a feasible option for morbidly obese patients, who are otherwise at high risk of developing sternal dehiscence. Using this technique may decrease postoperative narcotics usage. Morbidly obese patients (body mass index ≥35 kg/m2) have a higher-than-normal risk of sternal dehiscence after cardiac surgery. In a pilot study, we found that those who underwent transverse sternal plating (n = 8) had no sternal dehiscence and required less postoperative analgesia than patients who underwent standard wire closure (n = 14).

Retrospective analysis of the impact of sternum closure technique on postoperative comfort and rehabilitation

Introduction

Sternum closure techniques have been compared regarding biomechanics, efficacy in high-risk patients and prevention of mediastinitis or sternal dehiscence. There are no papers concerning patients' comfort and postoperative rehabilitation rate.

Aim

To establish the best surgical closure technique after midline sternotomy regarding the lowest pain level in the postoperative period and the highest rate of postoperative rehabilitation.

Material and methods

A retrospective analysis was performed on a group of 100 patients after cardiothoracic procedures which was divided into 3 subgroups according to sternal closure technique based on postoperative thoracic X-ray. To assess patients' pain and their physical activity we used a custom questionnaire. The statistical analysis was performed on the data regarding occurrence of wound healing complications risk factors, Numerical Rating Scale (NRS) for Pain score, the number of days until achieving important rehabilitations stages and the occurrence of sternal refixation.

Results

Subgroups had 35, 33 and 32 patients. The statistical analysis showed significantly lower NRS scores between the 14^th (p = 0.0012) (1.17) and 30^th (p = 0.0196) day (0.65) after the procedure in the group sutured with only single interrupted wire. There was also a significant difference in the number of days between the operation and the first time the patient could lie sideways (p = 0.0105). There was no statistically significant difference between the three groups regarding other measured factors.

Conclusions

The single wire suture provides less pain at the 14^th and 30^th day postoperatively measured on the NRS and ensures faster rehabilitation compared to sternal closing technique which involves placing both single and figure-of-8 sutures.

Usefulness of sternal closure with bioresorbable plate in respiratory function after coronary artery bypass grafting

OBJECTIVE

The aim of our study is to investigate that sternal reconstruction using bioresorbable plate in median sternotomy may reduce postoperative respiratory dysfunction when compared with wire cerclage only.

METHODS

We reviewed 107 patients who were undergone coronary artery bypass grafting with median sternotomy. Patients were divided into two groups; patients underwent sternal reconstruction with bioresorbable plate and wire cerclage (S group, n = 56), patients with wire cerclage only (N group, n = 51), and perioperative respiratory function and postoperative pain score data were analyzed and compared between two groups.

RESULTS

There was no significantly difference in preoperative respiratory function in both groups. However, in postoperative change rate of respiratory function, N group had significant decrease compared with S group in vital capacity (VC) (N: S = 74.8 ± 12.4: 85.2 ± 14.8%, p = 0.020), VC as a percentage of predicated VC (N: S = 75.0 ± 12.5: 86.4 ± 15.1%, p = 0.012), and forced expiratory volume in the first second (N: S = 73.7 ± 9.2: 85.3 ± 16.4%, p = 0.012). In Prince Henry Pain Scale, there were significantly more in N group compared with S group (N: S = 3.4 ± 1.0: 2.6 ± 1.4, p = 0.003).

CONCLUSION

Sternal fixation with bioresorbable plate could reduce impairment of postoperative respiratory function in comparison to wire cerclage only.

Sternotomy closure using rigid plate fixation: a paradigm shift from wire cerclage

Background

Rigid plate fixation (RPF) is the cornerstone in managing fractures and osteotomies except for sternotomy, where most cardiac surgeons continue to use wire cerclage (WC). Results of a multicenter randomized trial evaluating sternal healing, sternal complications, patient reported outcome measures (PROMs), and costs after sternotomy closure with RPF or WC are summarized here.

Methods

Twelve US centers randomized 236 patients to either RPF (n=116) or WC (n=120). The primary endpoint, sternal healing at 6 months, was evaluated by a core laboratory using computed tomography and a validated 6-point scale (greater scores represent greater healing). Secondary endpoints assessed through 6 months included sternal complications and PROMs. Costs from the time of sternal closure through 90 days and 6 months were analyzed by a health economic core laboratory.

Results

RPF compared to WC resulted in better sternal healing scores at 3 (2.6±1.1 vs. 1.8±1.0; P<0.0001) and 6 months (3.8±1.0 vs. 3.3±1.1; P=0.0007) and higher sternal union rates at 3 [41% (42/103) vs. 16% (16/102); P<0.0001] and 6 months [80% (81/101) vs. 67% (67/100); P=0.03]. There were fewer sternal complications with RPF through 6 months [0% (0/116) vs. 5% (6/120); P=0.03] and a trend towards fewer sternal wound infections [0% (0/116) vs. 4.2% (5/120); P=0.06]. All PROMs including sternal pain, upper extremity function (UEF), and quality-of-life scores were numerically better in RPF patients compared to WC patients at all follow-up time points. Although RPF was associated with a trend toward higher index hospitalization costs, a trend towards lower follow-up costs resulted in total costs that were $1,888 less at 90 days in RPF patients compared to WC patients (95% CI: -$8,889 to $4,273; P=0.52) and $1,646 less at 6 months (95% CI: -$9,127 to $4,706; P=0.61).

Conclusions

Sternotomy closure with RPF resulted in significantly better sternal healing, fewer sternal complications, improved PROMs and was cost neutral through 90 days and 6 months compared to WC.

Failure of sternal wires depends on the number of turns and plastic deformation: combined experimental and computational approach

OBJECTIVES

The number of turns at the end of a wire closure is not described or discussed in any cardiosurgical guidelines. The hands-on experience of the surgeon plays a significant role. The aim of this work was to clarify the relationship between the number of turns of the suture and the resulting strength of the sternal fixation.

METHODS

The study was performed in 2 independent steps. The first step was a finite element simulation, where the stress and strain distribution of the sternal fixation was observed. The second step included the experimental set-up and the statistical evaluation of the results.

RESULTS

Our study showed that the failure force rose linearly as the number of turns increased. The lowest average measured force was 370 N (3 turns); the highest was 430 N (7 turns). The failure modes were either untwisting of the wires or rupture of the closure, which is controlled by the number of turns. As the number of turns increases, superficial cracks can occur.

CONCLUSIONS

Based on our results, the 5-turn option is the best solution for the closure. The failure force is still double the value reported in the literature, so there is a high safety margin for failure. The failure mode is untwisting; hence, no unexpected fracture can occur, and there is still an elastic core in the cross-section of the wire.

Multifilament Cable Wire versus Conventional Wire for Sternal Closure in Patients Undergoing Major Cardiac Surgery

Background

Stainless steel wiring remains the most popular technique for primary sternal closure. Recently, a multifilament cable wiring system (Pioneer Surgical Technology Inc., Marquette, MI, USA) was introduced for sternal closure and has gained wide acceptance due to its superior resistance to tension. We aimed to compare conventional steel wiring to multifilament cable fixation for sternal closure in patients undergoing major cardiac surgery.

Methods

Data were collected retrospectively on 1,354 patients who underwent sternal closure after major cardiac surgery, using either the multifilament cable wiring system or conventional steel wires between January 2009 and October 2010. The surgical outcomes of these two groups of patients were compared using propensity score matching based on 18 baseline patient characteristics.

Results

Propensity score matching yielded 392 pairs of patients in the two groups whose baseline profiles showed no significant differences. No significant differences between the two groups were observed in the rates of early mortality (2.0% vs. 1.3%, p=0.578), major wound complications requiring reconstruction (1.3% vs. 1.3%, p>0.99), minor wound complications (3.6% vs. 2.0%, p=0.279), or mediastinitis (0.8% vs. 1.0%, p=1.00). Patients in the multifilament cable group had fewer sternal bleeding events than those in the conventional wire group, but this tendency was not statistically significant (4.3% vs. 7.4%, p=0.068).

Conclusion

The surgical outcomes of sternal closure using multifilament cable wires were comparable to those observed when conventional steel wires were used. Therefore, the multifilament cable wiring system may be considered a viable option for sternal closure in patients undergoing major cardiac surgery.

Mechanism of sternotomy dehiscence

OBJECTIVES

Biomechanical modelling of the forces acting on a median sternotomy can explain the mechanism of sternotomy dehiscence, leading to improved closure techniques.

METHODS

Chest wall forces on 40 kPa coughing were measured using a novel finite element analysis (FEA) ellipsoid chest model, based on average measurements of eight adult male thoracic computerized tomography (CT) scans, with Pearson's correlation coefficient used to assess the anatomical accuracy. Another FEA model was constructed representing the barrel chest of chronic obstructive pulmonary disease (COPD) patients. Six, seven and eight trans-sternal and figure-of-eight closures were tested against both FEA models.

RESULTS

Comparison between chest wall measurements from CT data and the normal ellipsoid FEA model showed an accurate fit (P < 0.001, correlation coefficients: coronal r = 0.998, sagittal r = 0.991). Coughing caused rotational moments of 92 Nm, pivoting at the suprasternal notch for the normal FEA model, rising to 118 Nm in the COPD model (t-test, P < 0.001). The threshold for dehiscence was 84 Nm with a six-sternal-wire closure, 107 Nm with seven wires, 127 Nm with eight wires and 71 Nm for three figure-of-eights.

CONCLUSIONS

The normal rib cage closely fits the ellipsoid FEA model. Lateral chest wall forces were significantly higher in the barrel-shaped chest. Rotational moments generated by forces acting on a six-sternal-wire closure at the suprasternal notch were sufficient to cause lateral distraction pivoting at the top of the manubrium. The six-sternal-wire closure may be successfully enhanced by the addition of one or two extra wires at the lower end of the sternotomy, depending on chest wall shape.

Evaluation of sternal closure with absorbable polydioxanone sutures in children

Introduction: Sternal dehiscence, sternal wound infection and mediastinitis are troublesome complications following median sternotomy which are major causes of morbidity and mortality of patients. Synthetic polydioxanone absorbable suture seems effective in prevention of these complications in children undergoing open heart surgery.

Methods: During 2 years period, 620 patients who underwent median sternotomy were studied. The efficacy of absorbable polydioxanone suture was tested on patients using figure-of-eight suture technique. The patients’ age ranged from newborn to 15 years old. All surgical interventions were performed according to a standard protocol.

Results: No sternal sutures were broken during the sternal closure and no case of mediastinitis was seen. Two patients experienced sternal dehiscence (0.32%). Follow-up period of patients were established between 1 to 132 months after open heart surgery.

Conclusion: Sternal closure with the polydioxanone suture in combination with figure-of-eight technique is a safe and suitable method in children with good clinical results.

A novel modified Robicsek technique for sternal closure: “Double-check”

A median sternotomy is the most common approach for cardiac and great vessel surgery. After a median sternotomy, healing complications such as instability, nonunion, and infection, are rare but devastating. Predisposing factors for sternal complications are old age, diabetes, steroid treatment, postmenopause state, obesity, reoperation, and the use of bilateral internal mammary arteries. Patients with sternal dehiscence frequently require reoperation to maintain optimum sternal stability. The technique chosen for sternal closure must provide excellent sternal approximation. We describe a modified Robicsek procedure reinforced with figure-of-8 sternal wires. We named this technique “double-check”.

Poststernotomy mediastinitis and the role of broken steel wires: retrospective study

OBJECTIVE

Mediastinitis is a severe complication of cardiac surgery. Sternal instability is concomitantly present in most cases. Broken steel wires may cause sternal instability. In this study, the role of broken steel wires in sternal closure was evaluated in patients who developed poststernotomy mediastinitis.

METHODS

Preoperative, perioperative, and postoperative data of patients who underwent thoracic surgery between 1996 and 2006 were retrieved from the SUMMIT registry database. Patients needing reoperation for mediastinitis were identified. Patients' charts and chest radiographs from initial surgery to reoperation for mediastinitis were reviewed.

RESULTS

Forty-five patients developed postoperative mediastinitis needing reoperation (0.6%). Because of loss to follow-up, 31 patients were evaluated. Eight patients (25.8%) presented fractured steel wires. Most of the broken steel wires (87.5%) manifested at the cranial site of figure-of-eight configurations. In the patients without broken steel wires, mediastinitis manifested after 14 days compared with 38 days in the patients with broken wires. Time until mediastinitis was not significantly different (P = 0.229). The mean time until steel wire disruption was 14 days (range, 4-48 days).

CONCLUSIONS

Broken steel wires were observed before mediastinitis became manifest. Fracturing occurred mainly at the cranial site of figure-of-eight configurations. The results of the present study emphasize that closure technique plays a prominent role in the development of mediastinitis. Because mediastinitis is associated with an increased risk for early morbidity, attention should be paid to patients presenting with broken steel wires. New techniques for median sternotomy closure are needed that are less prone to mechanical fatigue than are steel wires.

A review of sternal closure techniques

Sternotomy and sternal closure occur prior to and post cardiac surgery, respectively. Although post-operative complications associated with poor sternal fixation can result in morbidity, mortality, and considerable resource utilization, sternotomy is preferred over other methods such as lateral thoracotomy. Rigid sternal fixation is associated with stability and reduced incidence of post-operative complications. This is a comprehensive review of the literature evaluating in vivo, in vitro, and clinical responses to applying commercial and experimental surgical tools for sternal fixation after median sternotomy. Wiring, interlocking, plate-screw, and cementation techniques have been examined for closure, but none have experienced widespread adoption. Although all techniques have their advantages, serious post-operative complications were associated with the use of wiring and/or plating techniques in high-risk patients. A fraction of studies have analyzed the use of sternal interlocking systems and only a single study analyzed the effect of using kryptonite cement with wires. Plating and interlocking techniques are superior to wiring in terms of stability and reduced rate of post-operative complications; however, further clinical studies and long-term follow-up are required. The ideal sternal closure should ensure stability, reduced rate of post-operative complications, and a short hospitalization period, alongside cost-effectiveness.

Deep sternal wound complications: an overview of old and new therapeutic options

Deep sternal wound complications represent a significant problem in current open heart surgery and still pose a tremendous challenge to surgeons. Over the years, many treatment modalities have been proposed, but only few found their way into daily clinical practice of cardiothoracic surgeons. A gold standard has not been defined yet. This review was designed to give an overview of the preferred surgical strategies.

Prevention of sternal wound complications after sternotomy: results of a large prospective randomized multicentre trial

OBJECTIVES

A prospective randomized multicentre trial was performed to analyse the efficacy of a vest (Posthorax support vest®) to prevent sternal wound infection after cardiac surgery, and to identify risk factors.

METHODS

From September 2007 to March 2010, 2539 patients undergoing cardiac surgery via median sternotomy were prospectively randomized into those who received a Posthorax® vest and those who did not. Patients were instructed to wear the vest postoperatively for 24 h a day for at least 6 weeks; the duration of follow-up was 90 days. Patients who did not use the vest within a period of 72 h postoperatively were regarded as study dropouts. Statistical calculations were based on an intention-to-treat (ITT) analysis. Further evaluations comprised all subgroups of patients.

RESULTS

Complete data were available for 2539 patients (age 67 ± 11years, 45% female). Of these, 1351 were randomized to receive a vest, while 1188 received no vest. No significant differences were observed between groups regarding age, gender, diabetes, body mass index, chronic obstructive pulmonary disease (COPD), renal failure, the logistic EuroSCORE and the indication for surgery. The frequency of deep wound complications (dWC: mediastinitis and sternal dehiscence) was significantly lower in vest (n = 14; 1.04%) vs non-vest (n = 27; 2.27%) patients (ITT, P < 0.01), but superficial complications did not differ between groups. Subanalysis of vest patients revealed that only 933 (Group A) wore the vest according to the protocol, while 202 (Group BR) refused to wear the vest (non-compliance) and 216 (Group BN) did not use the vest for other reasons. All dWC occurred in Groups BR (n = 7) and BN (n = 7), although these groups had the same preoperative risk profile as Group A. Postoperatively, Group BN had a prolonged intubation time, a longer stay in the intensive care unit, greater use of intra-aortic balloon pump, higher frequency of COPD and a larger percentage of patients who required prolonged surgery.

CONCLUSIONS

Consistent use of the Posthorax® vest prevented deep sternal wounds. The anticipated risk factors for wound complications did not prove to be relevant, whereas intra- and postoperative complications appear to be very significant.

Late postcardiotomy sternal dehiscence: a simple approach using Stratos® system

Management of late sternal dehiscence is challenging and time consuming. Although numerous techniques exist including rewiring and titanium plates screwing to stabilize the sternum, we describe an alternative technique by using four titanium clips and one connecting bar.

Early and long-term results of pectoralis muscle flap reconstruction versus sternal rewiring following failed sternal closure

OBJECTIVES

The aim of the study was to compare early and long-term results of pectoralis muscle flap reconstruction with those of sternal rewiring following failed sternal closure. Primary outcomes of the study were survival and failure rate. Respiratory function, chronic pain and quality of life were also evaluated.

METHODS

In a propensity-score matching analysis, of 94 patients who underwent sternal reconstruction, 40 were selected; 20 underwent sternal reconstruction with bilateral pectoralis muscle flaps (Group 1) and 20 underwent sternal rewiring (Group 2). Survival and failure rates were evaluated by in-hospital records and at follow-up. Respiratory function measures, including vital capacity (VC), were evaluated both by spirometry and computed tomography (CT) volumetry. Chronic pain was evaluated by the visual analogue pain scale.

RESULTS

At 85 ± 24 months of follow-up, survival and procedure failure were 95 and 90% in Group 1 and 60 and 55% in Group 2, respectively (P < 0.01, for both comparisons). Based on CT-scan volumetry, in Group 1, severe non-union and hemisternal paradoxical movement occurred less frequently (2 vs 7, P = 0.01). At spirometry assessment, postoperative VC was greater in Group 1 (3220 ± 290 vs 3070 ± 290 ml, P = 0.04). The same trend was detected by CT-scan in-expiratory measures (4034 ± 1800 vs 3182 ± 862 mm(3), P < 0.05). Correspondingly, in Group 1, less patients presented in NYHA Class III (P < 0.05), and both chronic persistent pain score and physical health quality-of-life score were significantly better in the same group.

CONCLUSIONS

In our study, muscle flap reconstruction guaranteed better early and late-term results as shown by lower rates of mortality, procedure failure and hemisternum stability. Moreover, Group 1 patients had greater postoperative VC, lower NYHA class and better quality of life. These results suggest that, in patients with multiple bone fracture, the rewiring approach does not promote physiological bone consolidation, whereas the muscle flap reconstruction can assure more physiological ventilatory dynamics.

The use of Nitinol clips for primary sternal closure in cardiac surgery

PURPOSE

Deep sternal wound complications after cardiac surgery have an incidence of 2 to 8% and carry a significant mortality. The aim of this study was to evaluate the effect of thermo-reactive Nitinol clips on the incidence of postoperative deep sternal wound complications.

METHODS

We retrospectively reviewed 1119 consecutive patients that underwent major cardiac surgery via median sternotomy in our centre. Sternal closure was performed using Nitinol clips in 235 patients (Group I) and standard stainless steel wires in 884 patients (Group II). The risk factors that were identified between the two groups were age, EuroSCORE, body mass index, diabetes and pulmonary comorbidity.

RESULTS

The overall incidence of deep sternal wound complications was 2.2% (25/1119).The incidence was higher in Group II (2.3%) compared to Group I (1.7%) (p = 0?8).Mechanical sternal dehiscence occurred in 2 patients in Group II. Mortality related to sternal wound complications was 8% (2/21) in Group II whereas in Group I was 0%.

CONCLUSION

The incidence of sternal wound complications and the mortality related to them were lower in patients undergoing sternal closure with Nitinol clips. A randomized study to further evaluate the possible advantages of Nitinol clips is warranted.

Rigid plate fixation promotes better bone healing after sternotomy

Sternotomy is the most common surgically created osteotomy in surgery. Rigid fixation of osteotomies are important for stability and bony union. This review shows the superiority of rigid plate fixation in achieving better bone healing after sternotomy. It also highlights use of plate fixation for mini-sternotomies and rib fractures.

Sternal closure with rigid plate fixation versus wire closure: a randomized controlled multicenter trial

BACKGROUND

Rigid bone fixation is the standard of care for all bone reconstructions except that after sternotomy. Sternal reconstruction after median sternotomy using rigid fixation with plates may improve bone healing and reduce pain when compared with wire cerclage.

METHODS

One-hundred forty patients at six centers who were determined preoperatively to be at high risk for sternal wound complications were randomly assigned to sternal closure with rigid plate fixation (n=70) or wire cerclage (n=70). Sternal healing was evaluated at 3 or 6 months by a core laboratory using computed tomography. Pain and function were evaluated at postoperative day 3 through discharge, 3 weeks, 6 weeks, 3 months, and 6 months.

RESULTS

Sternal healing was superior in rigid plate fixation patients at both 3 and 6 months. Mean computed tomography scores in the rigid plate fixation and wire cerclage groups at 3 months were 1.7±1.1 and 0.9±0.8 (p=0.003). At 6 months, the scores were 3.2±1.6 and 2.2±1.1, respectively (p=0.01). At 6 months, 70% of rigid plate fixation patients had achieved sternal union, compared with 24% of conventional wire cerclage patients (p=0.003). Pain scores and narcotic usage were lower in rigid plate fixation patients. Significant differences in pain scores were observed at 3 weeks for total pain (p=0.020) and pain with coughing (p=0.0084) or sneezing (p=0.030). Complication rates were similar in both groups.

CONCLUSIONS

Sternal reconstruction using rigid fixation with plates improved bone healing and reduced early postoperative pain compared with wire cerclage.

The number of wires for sternal closure has a significant influence on sternal complications in high-risk patients

OBJECTIVES

Sternal dehiscence and mediastinitis are rare but serious complications following cardiac surgery. The aim of this study was to investigate the influence of the number of sternal wires used for chest closure on sternal complications.

METHODS

From May 2003 to April 2007, 4714 adult patients received cardiac surgery in our institute. X-ray images of all patients were reviewed and the used wires were counted. Patients who received another material or longitudinal wiring technique according to Robicsek for chest closure were excluded from this analysis; thus 4466 patients were included into the final analysis. Figure-of-eight wiring was counted as two wires.

RESULTS

Sternal complications occurred in 2.4%, and hospital mortality with or without sternal complications were 2.8 and 2.7%, respectively (P = 0.60). Mean numbers of sternal wires were 7.8 in both patient groups with or without sternal complications (P = 0.79). Multivariate analysis revealed diabetes mellitus [odds ratio (OR) 1.54, 95% CI 1.01-2.34, P = 0.04], chronic obstructive pulmonary disease (OR 1.85, 95% CI 1.12-2.79, P = 0.01) and renal insufficiency (OR 1.70, 95% CI 1.11-2.59, P = 0.001) as significant risk factors for sternal complications. In high-risk patients, the use of less than eight wires was significantly associated with postoperative sternal complications.

CONCLUSIONS

Particularly in high-risk patients, careful haemostasis should be done and eight or more wires should be used to avoid sternal complications.

Does the number of wires used to close a sternotomy have an impact on deep sternal wound infection?

OBJECTIVES

We studied the influence of the number of sternotomy mechanical fixation points on deep sternal wound infection (DSWI).

METHODS

Between September 2007 and February 2011, 2672 patients underwent a standard peri-sternal wire closure following a median sternotomy for a first-time cardiac surgery. Data were collected during the study period.

RESULTS

The mean age of the patients was 66 ± 11 and 1978 (74.0%) were male. The mean body mass index (BMI) was 28.9 ± 9.3 and the median of the logistic EuroSCORE was 3.14, with a range of 0.88-54.1. Postoperatively, 40 (1.5%) patients developed DSWI after 14 ± 6 days, of whom 39 (92.5%) had positive deep sternal wound specimen cultures, predominantly Staphylococci (62.5%). The risk of DSWI was significantly increased in patients in whom eight or fewer paired points of sternal wire fixation were used when compared with patients in whom nine or more paired points of fixation were used (P = 0.002). Preoperative myocardial infarction (P = 0.001), elevated BMI (P = 0.046), bilateral internal mammary artery harvest (P < 0.0001), postoperative hypoxia (P < 0.0001), sepsis (P = 0.019) and postoperative inotrope use (P = 0.007) significantly increased the risk of DSWI.

CONCLUSIONS

DSWI is associated with hypoxia, ischaemia, sepsis and mechanical sternal instability. DSWI may be prevented by using nine or more paired fixation points when closing with standard peri-sternal wires.