Discussion:
Sternal dehiscence represents one of the major causes of morbidity after
cardiac surgery performed through full median sternotomy. The key to the
successful management of NISD is early referral to refixation [9].
Time to reoperation for refixation varies in the literature from 10 to
300 days [4,6]. In our study, refixation was performed after a mean
time of 49.4±9.5 days following the initial procedure. Surgery for this
complication should be performed as soon as possible.
Multiple surgical techniques have been described for reconstructing the
anterior chest wall in the treatment of sternal dehiscence, but none of
them is yet considered the gold-standard procedure [10]. In our
hospital, Robicsek repair is the first method of treatment in NSID after
median sternotomy whereas TRNC method is mostly advised for patients
with multiple comorbidities. In this study, we compared the surgical
results of the TRNC technique in patients with a previously failed
Robicsek treatment (group A) and patients who were directly referred for
TRNC treatment after a diagnosis of NISD (group B). Moreover, we
compared group B with those who underwent Robicsek repair as the first
procedure (group C). Our aim was to establish the importance of
prioritization of TRNC treatment in high-risk NISD patients.
The potential mechanisms of comorbidities that increase the risk of
sternal dehiscence in high-risk patients are as follows: the sternum
healing is compromised due to the separating radial forces from the
prolonged ventilation and chronic abundant cough in COPD; the sternum
bone fragility is induced by the intrinsic pathology in patients
>75 years of age, diabetes and severe osteoporosis; and
that osteosynthesis is reduced in patients with renal insufficiency,
chest irradiation and chronic steroid use. Additional risk factors could
include congestive heart failure and peripheral vascular disease,
because these patients have particularly compromised peripheral
vascularization, which reduces sternal healing [11]. In morbidly
obese patients, the lateral stress is increased even more because of
their body habitus. Excessive tissue places additional stress on the
sternotomy closure, both laterally by the chest wall and inferiorly by
the abdominal wall [12]. In our study, there was no significant
difference between the groups in terms of comorbidities.
Bilateral internal mammary artery usage interrupts sternal blood flow,
which poses a risk for sternal dehiscence. Prolonged retraction of both
sternum halves may cause ischemic fields and result in healing problems
after long cardio-pulmonary bypass runs, repeated sternal openings, and
rewirings. An asymmetric off-center sternotomy and transverse fractures
prevent a decent anatomical sternal closure due to disruption of
sternochondral joints and sternum halves (Figure 3) [13]. In our
study, there was no significant difference between the groups in terms
of surgical complications. Both group A and group B consisted of
high-risk patients.
The classic technique described by Robicsek et al. relocates and
distributes the pressure over the sternum by changing the site of the
pressure and providing wider support [8]. The disadvantage of this
technique is the need for substernal dissection and the effect on the
blood flow to the area. When intercostal arteries are squeezed by the
ring formed by steel wires running up-and-down and anterior-posterior
around the ribs, a constrictive weave is produced that can disrupt the
collateral blood supply to the sternum. This may worsen a pre-existing
ischemia, which facilitates bacterial colonization and delays sternal
healing. Furthermore, ischemia may cause bone necrosis and additional
sternal fragmentation [13,14]. In our study, 260 patients underwent
Robicsek repair due to NISD, but 6.1% had still sternal dehiscence
afterward (n=16). Out of those 16 patients, 11 cases were high-risk
patients and they were referred to TRNC treatment. The success rate of
the Robicsek method in the treatment of high risk NISD patients, was
35.3% (6/17). On the other hand, its fail rate was only 2.1% in
without high-risk patients (5/243).
The TRNC technique is easier and has a shorter operation time than the
Robicsek method. In our study, operative time in group B was
significantly shorter compared to group C as expected. The TRNC method
is also considered a safer technique because less substernal dissection
is needed. TRNCs have shown less risk for tearing the bone than steel
wires. Nitinol clips are not integrated into the bone and their
thermoreactive characteristics allow them to be removed easily when
required [15]. The TRNC technique brings both hemi-sternums together
without harming the intercostal structures. Therefore, it does not
technically affect sternal blood flow [16]. Many studies have
hypothesized that using TRNCs is a superior dehiscence repair method
compared to Robicsek method [8,17]. The disadvantage of the TRNC
technique is that it is more expensive due to the cost of hardware. The
cost of each plate ranges from 90 euro to 100 euro. In our study, we
only used TRNCs in high-risk patients and patients with failed Robicsek
procedures. We wished to use the TRNC method in each patient with NISD,
but its cost prevented us from performing this method on regular basis.
After observing several cases of Robicsek repair failure in high-risk
patients, most high-risk patients with NISD were directly referred to
the thoracic surgery clinic for TRNC treatment.
In our study, we observed that ischemic tissues were more common, the
sternum often adhered to the underlying tissue, and sometimes to the
myocardium, due to previous Robicsek procedure during TRNC treatment in
group A. Since group B had no history of failed a Robicsek method, the
surgeon could perform a rapid and less challenging TRNC treatment
without additional surgical risks, due to significantly less need for
substernal dissection. In our study, we did not perform substernal
dissection in group B. Consequently, operation time and operative blood
loss in group B was significantly lower compared to group A. Moreover,
nonunion rate was significantly lower in group B.
According to various studies, the most commonly reported complications
of TRNC treatment are: postoperative pneumonia with an incidence up to
10%, hematoma or seroma formation with an incidence up to 24%, and
clip removal due to infection or pain up to 50% [18]. Current
sternal dehiscence treatment methods have morbidity rates of 10–25%
and mortality rates of 5–47% [19]. Refixation has a high risk of
postoperative complications regardless of the chosen treatment method
[20]. In our study, although both group A and B consisted of
high-risk patients, the postoperative complication rate in group A was
significantly higher than in group B (54.5% vs 17.4%). Due to this
higher complication rate, hospitalization in group A was also
significantly longer compared to that in group B. Postoperative wound
complication and pneumonia rates were significantly higher in group A.
As a result, an additional operation for refixation and the introduction
of an extra session of general anesthesia for patients with additional
diseases greatly increased both surgical risks and postoperative
complication rates. Fortunately, there was no mortality in either group.
Our study was a single center, retrospective study. We did not include
patients with infectious sternal dehiscence due to lack of recorded
data. Therefore, we could not come to a general conclusion about the
usage of the TRNC system in high-risk patients and were limited to NISD.
Due to the small number of patients included in our study, statistical
power was low and our ability to examine low-frequency outcomes was
limited.
Patients with multiple established factors of sternal dehiscence are
high-risk patients for the treatment of NISD. TRNC use in sternal
closure of high-risk patients may prevent sternal dehiscence, but it is
impractical to use such expensive materials on regular basis. The
Robicsek procedure is proven to be an effective method in the treatment
of NISD but, in case of its failure, subsequent TRNC treatment might
become cumbersome in high-risk patients. In our study; a direct TRNC
treatment approach for high-risk patients in the treatment of NISD was
superior to the Robicsek method because a previously failed Robicsek
procedure caused significantly higher morbidity and additional operative
risk in later TRNC treatment of high-risk cases. Ultimately, we
speculate that a direct TRNC treatment for NISD is favorable in
high-risk patients.
Acknowledgements : English editing by ‘Editage’
Conflict of interest : none
Funding: None